Initial

.gitignore

@@ -0,0 +1,20 @@
+.DS_Store
+
+*.pbxuser
+*.perspective
+*.perspectivev3
+
+*.mode1v3
+*.mode2v3
+
+*.xcodeproj/xcuserdata/*.xcuserdatad
+
+*.xccheckout
+*.xcuserdatad
+
+Pods
+
+DerivedData
+build
+
+.ruby-version

.travis.yml

@@ -0,0 +1,39 @@
+branches:
+  only:
+    - master
+language: objective-c
+os: osx
+osx_image: xcode9.2
+env:
+  matrix:
+    - TEST_TYPE=iOS
+    - TEST_TYPE=OSX
+    - TEST_TYPE=tvOS
+    - TEST_TYPE=CocoaPods
+install:
+- |
+  if [ "$TEST_TYPE" = iOS ] || [ "$TEST_TYPE" = OSX ] || [ "$TEST_TYPE" = tvOS ]; then
+    gem install xcpretty -N --no-ri --no-rdoc
+    gem install cocoapods --quiet --no-ri --no-rdoc
+    pod install
+  fi
+script:
+- |
+  if [ "$TEST_TYPE" = iOS ]; then
+    set -o pipefail
+    xcodebuild -workspace pop.xcworkspace -scheme pop-ios-framework -sdk iphonesimulator build test -destination "platform=iOS Simulator,name=iPhone SE" GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=YES GCC_GENERATE_TEST_COVERAGE_FILES=YES | xcpretty -c
+  elif [ "$TEST_TYPE" = OSX ]; then
+    set -o pipefail
+    xcodebuild -workspace pop.xcworkspace -scheme pop-osx-framework -sdk macosx build test GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=YES GCC_GENERATE_TEST_COVERAGE_FILES=YES | xcpretty -c
+  elif [ "$TEST_TYPE" = tvOS ]; then
+    set -o pipefail
+    xcodebuild -workspace pop.xcworkspace -scheme pop-tvos-framework -sdk appletvsimulator build test -destination "platform=tvOS Simulator,name=Apple TV" GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=YES GCC_GENERATE_TEST_COVERAGE_FILES=YES | xcpretty -c
+  elif [ "$TEST_TYPE" = CocoaPods ]; then
+    pod lib lint pop.podspec
+    pod lib lint --use-libraries pop.podspec
+  fi
+after_success:
+- |
+  if [ "$TEST_TYPE" = iOS ] || [ "$TEST_TYPE" = OSX ] || [ "$TEST_TYPE" = tvOS ]; then
+    bash <(curl -s https://codecov.io/bash)
+  fi

CONTRIBUTING.md

@@ -0,0 +1,28 @@
+# Contributing
+We want to make contributing to Pop as easy and transparent as
+possible. If you run into problems, please open an issue. We also actively welcome pull requests.
+
+## Pull Requests
+1. Fork the repo and create your branch from `master`.
+2. If you've added code that should be tested, add tests
+3. If you've changed APIs, update the documentation.
+4. Ensure the test suite passes.
+5. Make sure your code lints.
+6. If you haven't already, complete the Contributor License Agreement ("CLA").
+
+## Contributor License Agreement ("CLA")
+In order to accept your pull request, we need you to submit a CLA. You only need
+to do this once to work on any of Facebook's open source projects.
+
+Complete your CLA here: <https://code.facebook.com/cla>
+
+## Issues  
+We use GitHub issues to track public bugs. Please ensure your description is
+clear and has sufficient instructions to be able to reproduce the issue.
+
+## Coding Style  
+* 2 spaces for indentation rather than tabs
+
+## License
+By contributing to Pop you agree that your contributions will be licensed
+under its BSD license.

Configuration/Compiler.xcconfig

@@ -0,0 +1,77 @@
+//
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+//
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+//
+
+// Deployment targets
+MACOSX_DEPLOYMENT_TARGET = 10.7
+IPHONEOS_DEPLOYMENT_TARGET = 8.0
+TVOS_DEPLOYMENT_TARGET = 9.0
+
+// Warnings
+GCC_TREAT_WARNINGS_AS_ERRORS = YES
+CLANG_WARN_CONSTANT_CONVERSION = YES
+CLANG_WARN_ENUM_CONVERSION = YES
+CLANG_WARN_INT_CONVERSION = YES
+CLANG_WARN_INFINITE_RECURSION = YES
+CLANG_WARN_SUSPICIOUS_MOVE = YES
+CLANG_WARN__DUPLICATE_METHOD_MATCH = YES
+CLANG_WARN_BOOL_CONVERSION = YES
+CLANG_WARN_EMPTY_BODY = YES
+CLANG_WARN_OBJC_MISSING_PROPERTY_SYNTHESIS = YES
+CLANG_WARN_CXX0X_EXTENSIONS = NO
+CLANG_WARN_UNREACHABLE_CODE = YES
+CLANG_WARN_DEPRECATED_OBJC_IMPLEMENTATIONS = YES
+CLANG_WARN_OBJC_IMPLICIT_RETAIN_SELF = YES
+CLANG_WARN_STRICT_PROTOTYPES = YES
+GCC_WARN_ABOUT_DEPRECATED_FUNCTIONS = NO
+GCC_WARN_ABOUT_MISSING_PROTOTYPES = YES
+GCC_WARN_ABOUT_RETURN_TYPE = YES
+GCC_WARN_INITIALIZER_NOT_FULLY_BRACKETED = YES
+GCC_WARN_MISSING_PARENTHESES = YES
+GCC_WARN_SHADOW = YES
+GCC_WARN_SIGN_COMPARE = YES
+GCC_WARN_UNINITIALIZED_AUTOS = YES
+GCC_WARN_UNDECLARED_SELECTOR = YES
+GCC_WARN_UNUSED_FUNCTION = YES
+GCC_WARN_UNUSED_VARIABLE = YES
+GCC_WARN_64_TO_32_BIT_CONVERSION = YES
+CLANG_WARN_BLOCK_CAPTURE_AUTORELEASING = YES
+CLANG_WARN_COMMA = YES
+CLANG_WARN_NON_LITERAL_NULL_CONVERSION = YES
+CLANG_WARN_OBJC_LITERAL_CONVERSION = YES
+CLANG_WARN_RANGE_LOOP_ANALYSIS = YES
+WARNING_CFLAGS = -Wall -Wextra -Wno-unused-parameter
+
+// Language
+GCC_C_LANGUAGE_STANDARD = gnu99
+CLANG_CXX_LANGUAGE_STANDARD = c++11
+CLANG_CXX_LIBRARY = libc++
+
+// Application Extension
+APPLICATION_EXTENSION_API_ONLY = YES
+
+// Preprocessing
+ENABLE_STRICT_OBJC_MSGSEND = YES
+
+// Enable ARC
+CLANG_ENABLE_OBJC_ARC = YES
+
+// Modules
+CLANG_ENABLE_MODULES=YES
+
+// Search Paths
+ALWAYS_SEARCH_USER_PATHS = NO
+FRAMEWORK_SEARCH_PATHS = $(inherited) $(BUILT_PRODUCTS_DIR)
+LIBRARY_SEARCH_PATHS = $(BUILT_PRODUCTS_DIR) $(inherited)
+HEADER_SEARCH_PATHS = $(inherited) $(SYMROOT)/Headers $(DERIVED_FILE_DIR)
+
+// Code Generation
+GCC_DYNAMIC_NO_PIC = NO
+GCC_NO_COMMON_BLOCKS = YES
+GCC_INLINES_ARE_PRIVATE_EXTERN = YES
+GCC_SYMBOLS_PRIVATE_EXTERN = NO

Configuration/Product/ApplicationTests.xcconfig

@@ -0,0 +1,16 @@
+// 
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+// 
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+// 
+
+#include "LogicTests.xcconfig"
+
+// Linking
+BUNDLE_LOADER = $(BUILT_PRODUCTS_DIR)/$(PROJECT_NAME)TestHost.app/$(PROJECT_NAME)TestHost
+
+// Unit Testing
+TEST_HOST = "$(BUNDLE_LOADER)"

Configuration/Product/Framework.xcconfig

@@ -0,0 +1,15 @@
+//
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+//
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+//
+
+#include "../Compiler.xcconfig"
+
+// Version
+DYLIB_COMPATIBILITY_VERSION = 1
+DYLIB_CURRENT_VERSION = 1
+CURRENT_PROJECT_VERSION = 1

Configuration/Product/LogicTests.xcconfig

@@ -0,0 +1,14 @@
+// 
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+// 
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+// 
+
+#include "../Compiler.xcconfig"
+
+// Deployment
+DSTROOT = /tmp/$(TARGET_NAME)
+SKIP_INSTALL = YES

Configuration/Product/StaticLibrary.xcconfig

@@ -0,0 +1,21 @@
+// 
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+// 
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+// 
+
+#include "../Compiler.xcconfig"
+
+// Deployment
+DSTROOT = /tmp/$(TARGET_NAME)
+INSTALL_PATH = $(SYMROOT)/Headers
+SKIP_INSTALL = YES
+
+// declare inlines as extern
+GCC_INLINES_ARE_PRIVATE_EXTERN = YES
+
+// Use PRODUCT_NAME instead of TARGET_NAME to support multiple targets for different platforms
+PUBLIC_HEADERS_FOLDER_PATH = include/$(PRODUCT_NAME)

Configuration/Project/Project-Debug.xcconfig

@@ -0,0 +1,31 @@
+// 
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+// 
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+// 
+
+#include "Project.xcconfig"
+
+// Architectures
+ONLY_ACTIVE_ARCH = YES
+
+// Code Generation
+GCC_OPTIMIZATION_LEVEL = 0
+
+// Enable assertions
+ENABLE_NS_ASSERTIONS = YES
+
+// Avoid compression overhead
+COMPRESS_PNG_FILES = NO
+
+// Deployment
+COPY_PHASE_STRIP = NO
+
+// Default to dwarf
+DEBUG_INFORMATION_FORMAT = dwarf
+
+// Testing
+ENABLE_TESTABILITY = YES

Configuration/Project/Project-Profile.xcconfig

@@ -0,0 +1,31 @@
+// 
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+// 
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+// 
+
+#include "Project.xcconfig"
+
+// Code Generation
+GCC_OPTIMIZATION_LEVEL = s
+
+// Disable assertions
+ENABLE_NS_ASSERTIONS = NO
+
+// Enable Xcode PNG compression
+COMPRESS_PNG_FILES = YES
+
+// Deployment
+COPY_PHASE_STRIP = NO
+
+// Preprocessing
+GCC_PREPROCESSOR_DEFINITIONS = PROFILE=1 NS_BLOCK_ASSERTIONS NDEBUG
+
+// We need debug symbols for profiling
+DEBUG_INFORMATION_FORMAT = dwarf-with-dsym
+
+// Not all libraries have a Profile version. Allow using the Release version if they don't.
+LIBRARY_SEARCH_PATHS = $(BUILT_PRODUCTS_DIR) $(BUILD_DIR)/Release$(EFFECTIVE_PLATFORM_NAME)

Configuration/Project/Project-Release.xcconfig

@@ -0,0 +1,25 @@
+// 
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+// 
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+// 
+
+#include "Project.xcconfig"
+
+// Code Generation
+GCC_OPTIMIZATION_LEVEL = s
+
+// Disable assertions
+ENABLE_NS_ASSERTIONS = NO
+
+// Enable Xcode PNG compression
+COMPRESS_PNG_FILES = YES
+
+// Build Options
+VALIDATE_PRODUCT = YES
+
+// Preprocessing
+GCC_PREPROCESSOR_DEFINITIONS = PROFILE=1 NS_BLOCK_ASSERTIONS NDEBUG

Configuration/Project/Project.xcconfig

@@ -0,0 +1,16 @@
+// 
+// Copyright (c) 2014-present, Facebook, Inc.
+// All rights reserved.
+// 
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+// 
+
+#include "../Compiler.xcconfig"
+
+// Install
+SKIP_INSTALL = YES
+
+// Code Signing
+CODE_SIGN_IDENTITY =

LICENSE

@@ -0,0 +1,30 @@
+BSD License
+
+For Pop software
+
+Copyright (c) 2014, Facebook, Inc. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+   list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+   this list of conditions and the following disclaimer in the documentation
+   and/or other materials provided with the distribution.
+
+ * Neither the name Facebook nor the names of its contributors may be used to
+   endorse or promote products derived from this software without specific
+   prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
+ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

PATENTS

@@ -0,0 +1,33 @@
+Additional Grant of Patent Rights Version 2
+
+"Software" means the Pop software distributed by Facebook, Inc.
+
+Facebook, Inc. ("Facebook") hereby grants to each recipient of the Software
+("you") a perpetual, worldwide, royalty-free, non-exclusive, irrevocable
+(subject to the termination provision below) license under any Necessary
+Claims, to make, have made, use, sell, offer to sell, import, and otherwise
+transfer the Software. For avoidance of doubt, no license is granted under
+Facebook’s rights in any patent claims that are infringed by (i) modifications
+to the Software made by you or any third party or (ii) the Software in
+combination with any software or other technology.
+
+The license granted hereunder will terminate, automatically and without notice,
+if you (or any of your subsidiaries, corporate affiliates or agents) initiate
+directly or indirectly, or take a direct financial interest in, any Patent
+Assertion: (i) against Facebook or any of its subsidiaries or corporate
+affiliates, (ii) against any party if such Patent Assertion arises in whole or
+in part from any software, technology, product or service of Facebook or any of
+its subsidiaries or corporate affiliates, or (iii) against any party relating
+to the Software. Notwithstanding the foregoing, if Facebook or any of its
+subsidiaries or corporate affiliates files a lawsuit alleging patent
+infringement against you in the first instance, and you respond by filing a
+patent infringement counterclaim in that lawsuit against that party that is
+unrelated to the Software, the license granted hereunder will not terminate
+under section (i) of this paragraph due to such counterclaim.
+
+A "Necessary Claim" is a claim of a patent owned by Facebook that is
+necessarily infringed by the Software standing alone.
+
+A "Patent Assertion" is any lawsuit or other action alleging direct, indirect,
+or contributory infringement or inducement to infringe any patent, including a
+cross-claim or counterclaim.

Podfile

@@ -0,0 +1,15 @@
+abstract_target 'Tests' do
+  pod 'OCMock', '~> 2.2'
+  
+  target :'pop-tests-ios' do
+    platform :ios, '6.0'
+  end
+
+  target :'pop-tests-tvos' do
+    platform :tvos, '9.0'
+  end
+
+  target :'pop-tests-osx' do
+    platform :osx, '10.8'
+  end
+end

Podfile.lock

@@ -0,0 +1,12 @@
+PODS:
+  - OCMock (2.2.4)
+
+DEPENDENCIES:
+  - OCMock (~> 2.2)
+
+SPEC CHECKSUMS:
+  OCMock: a6a7dc0e3997fb9f35d99f72528698ebf60d64f2
+
+PODFILE CHECKSUM: 06e2f62938dff5782de5abf2adf6966a85f24637
+
+COCOAPODS: 1.2.1

README.md

@@ -0,0 +1,341 @@
+![pop](https://github.com/facebook/pop/blob/master/Images/pop.gif?raw=true)
+
+Pop is an extensible animation engine for iOS, tvOS, and OS X. In addition to basic static animations, it supports spring and decay dynamic animations, making it useful for building realistic, physics-based interactions. The API allows quick integration with existing Objective-C or Swift codebases and enables the animation of any property on any object. It's a mature and well-tested framework that drives all the animations and transitions in [Paper](https://en.wikipedia.org/wiki/Facebook_Paper).
+
+[![Build Status](https://travis-ci.org/facebook/pop.svg)](https://travis-ci.org/facebook/pop)
+
+## Installation
+
+Pop is available on [CocoaPods](http://cocoapods.org). Just add the following to your project Podfile:
+
+```ruby
+pod 'pop', '~> 1.0'
+```
+
+Bugs are first fixed in master and then made available via a designated release. If you tend to live on the bleeding edge, you can use Pop from master with the following Podfile entry:
+
+```ruby
+pod 'pop', :git => 'https://github.com/facebook/pop.git'
+```
+
+### Framework (manual)
+By adding the project to your project and adding pop.embedded framework to the Embedded Binaries section on the General tab of your app's target, you can set up pop in seconds! This also enables `@import pop` syntax with header modules.
+
+**Note**: because of some awkward limitations with Xcode, embedded binaries must share the same name as the module and must have `.framework` as an extension. This means that you'll see three pop.frameworks when adding embedded binaries (one for OS X, one for tvOS, and one for iOS). You'll need to be sure to add the right one; they appear identically in the list but note the list is populated in order of targets. You can verify the correct one was chosen by checking the path next to the framework listed, in the format `<configuration>-<platform>` (e.g. `Debug-iphoneos`).
+
+![Embedded Binaries](Images/EmbeddedBinaries.png?raw=true)
+
+**Note 2**: this method does not currently play nicely with workspaces. Since targets can only depend on and embed products from other targets in the same project, it only works when pop.xcodeproj is added as a subproject to the current target's project. Otherwise, you'll need to manually set the build ordering in the scheme and copy in the product.
+
+### Static Library (manual)
+Alternatively, you can add the project to your workspace and adopt the provided configuration files or manually copy the files under the pop subdirectory into your project. If installing manually, ensure the C++ standard library is also linked by including `-lc++` to your project linker flags.
+
+## Usage
+
+Pop adopts the Core Animation explicit animation programming model. Use by including the following import:
+
+#### Objective-C
+
+```objective-c
+#import <pop/POP.h>
+```
+
+or if you're using the embedded framework:
+
+```objective-c
+@import pop;
+```
+
+#### Swift
+
+```swift
+import pop
+```
+
+### Start, Stop & Update
+
+To start an animation, add it to the object you wish to animate:
+
+#### Objective-C
+
+```objective-c
+POPSpringAnimation *anim = [POPSpringAnimation animation];
+...
+[layer pop_addAnimation:anim forKey:@"myKey"];
+```
+
+#### Swift
+
+```swift
+let anim = POPSpringAnimation()
+...
+layer.pop_add(anim, forKey: "myKey")
+```
+
+To stop an animation, remove it from the object referencing the key specified on start:
+
+#### Objective-C
+
+```objective-c
+[layer pop_removeAnimationForKey:@"myKey"];
+```
+
+#### Swift
+
+```swift
+layer.pop_removeAnimation(forKey: "myKey")
+```
+
+The key can also be used to query for the existence of an animation. Updating the toValue of a running animation can provide the most seamless way to change course:
+
+#### Objective-C
+
+```objective-c
+anim = [layer pop_animationForKey:@"myKey"];
+if (anim) {
+  /* update to value to new destination */
+  anim.toValue = @(42.0);
+} else {
+  /* create and start a new animation */
+  ....
+}
+```
+
+#### Swift
+
+```swift
+if let anim = layer.pop_animation(forKey: "myKey") as? POPSpringAnimation {
+    /* update to value to new destination */
+    anim.toValue = 42.0
+} else {
+    /* create and start a new animation */
+    ....
+}
+```
+
+While a layer was used in the above examples, the Pop interface is implemented as a category addition on NSObject. Any NSObject or subclass can be animated.
+
+### Types
+
+There are four concrete animation types: spring, decay, basic and custom.
+
+Spring animations can be used to give objects a delightful bounce. In this example, we use a spring animation to animate a layer's bounds from its current value to (0, 0, 400, 400):
+
+#### Objective-C
+
+```objective-c
+POPSpringAnimation *anim = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerBounds];
+anim.toValue = [NSValue valueWithCGRect:CGRectMake(0, 0, 400, 400)];
+[layer pop_addAnimation:anim forKey:@"size"];
+```
+
+#### Swift
+
+```swift
+if let anim = POPSpringAnimation(propertyNamed: kPOPLayerBounds) {
+    anim.toValue = NSValue(cgRect: CGRect(x: 0, y: 0, width: 400, height: 400))
+    layer.pop_add(anim, forKey: "size")
+}
+```
+
+Decay animations can be used to gradually slow an object to a halt. In this example, we decay a layer's positionX from it's current value and velocity 1000pts per second:
+
+#### Objective-C
+
+```objective-c
+POPDecayAnimation *anim = [POPDecayAnimation animationWithPropertyNamed:kPOPLayerPositionX];
+anim.velocity = @(1000.);
+[layer pop_addAnimation:anim forKey:@"slide"];
+```
+
+#### Swift
+
+```swift
+if let anim = POPDecayAnimation(propertyNamed: kPOPLayerPositionX) {
+    anim.velocity = 1000.0
+    layer.pop_add(anim, forKey: "slide")
+}
+```
+
+Basic animations can be used to interpolate values over a specified time period. To use an ease-in ease-out animation to animate a view's alpha from 0.0 to 1.0 over the default duration:
+
+#### Objective-C
+
+```objective-c
+POPBasicAnimation *anim = [POPBasicAnimation animationWithPropertyNamed:kPOPViewAlpha];
+anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
+anim.fromValue = @(0.0);
+anim.toValue = @(1.0);
+[view pop_addAnimation:anim forKey:@"fade"];
+```
+
+#### Swift
+
+```swift
+if let anim = POPBasicAnimation(propertyNamed: kPOPViewAlpha) {
+    anim.timingFunction = CAMediaTimingFunction(name: kCAMediaTimingFunctionEaseInEaseOut)
+    anim.fromValue = 0.0
+    anim.toValue = 1.0
+    view.pop_add(anim, forKey: "fade")
+}
+```
+
+`POPCustomAnimation` makes creating custom animations and transitions easier by handling CADisplayLink and associated time-step management. See header for more details.
+
+
+### Properties
+
+The property animated is specified by the `POPAnimatableProperty` class. In this example we create a spring animation and explicitly set the animatable property corresponding to `-[CALayer bounds]`:
+
+#### Objective-C
+
+```objective-c
+POPSpringAnimation *anim = [POPSpringAnimation animation];
+anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerBounds];
+```
+
+#### Swift
+
+```swift
+let anim = POPSpringAnimation()
+if let property = POPAnimatableProperty.property(withName: kPOPLayerBounds) as? POPAnimatableProperty {
+    anim.property = property
+}
+```
+
+The framework provides many common layer and view animatable properties out of box. You can animate a custom property by creating a new instance of the class. In this example, we declare a custom volume property:
+
+#### Objective-C
+
+```objective-c
+prop = [POPAnimatableProperty propertyWithName:@"com.foo.radio.volume" initializer:^(POPMutableAnimatableProperty *prop) {
+  // read value
+  prop.readBlock = ^(id obj, CGFloat values[]) {
+    values[0] = [obj volume];
+  };
+  // write value
+  prop.writeBlock = ^(id obj, const CGFloat values[]) {
+    [obj setVolume:values[0]];
+  };
+  // dynamics threshold
+  prop.threshold = 0.01;
+}];
+
+anim.property = prop;
+```
+
+#### Swift
+
+```swift
+if let prop = POPAnimatableProperty.property(withName: "com.foo.radio.volume", initializer: { prop in
+    guard let prop = prop else {
+        return
+    }
+    // read value
+    prop.readBlock = { obj, values in
+        guard let obj = obj as? Volumeable, let values = values else {
+            return
+        }
+
+        values[0] = obj.volume
+    }
+    // write value
+    prop.writeBlock = { obj, values in
+        guard var obj = obj as? Volumeable, let values = values else {
+            return
+        }
+
+        obj.volume = values[0]
+    }
+    // dynamics threshold
+    prop.threshold = 0.01
+}) as? POPAnimatableProperty {
+    anim.property = prop
+}
+```
+
+For a complete listing of provided animatable properties, as well more information on declaring custom properties see `POPAnimatableProperty.h`.
+
+
+### Debugging
+
+Here are a few tips when debugging. Pop obeys the Simulator's Toggle Slow Animations setting. Try enabling it to slow down animations and more easily observe interactions.
+
+Consider naming your animations. This will allow you to more easily identify them when referencing them, either via logging or in the debugger:
+
+#### Objective-C
+
+```objective-c
+anim.name = @"springOpen";
+```
+
+#### Swift
+
+```swift
+anim.name = "springOpen"
+```
+
+Each animation comes with an associated tracer. The tracer allows you to record all animation-related events, in a fast and efficient manner, allowing you to query and analyze them after animation completion. The below example starts the tracer and configures it to log all events on animation completion:
+
+#### Objective-C
+
+```objective-c
+POPAnimationTracer *tracer = anim.tracer;
+tracer.shouldLogAndResetOnCompletion = YES;
+[tracer start];
+```
+
+#### Swift
+
+```swift
+if let tracer = anim.tracer {
+    tracer.shouldLogAndResetOnCompletion = true
+    tracer.start()
+}
+```
+
+See `POPAnimationTracer.h` for more details.
+
+## Testing
+
+Pop has extensive unit test coverage. To install test dependencies, navigate to the root pop directory and type:
+
+```sh
+pod install
+```
+
+Assuming CocoaPods is installed, this will include the necessary OCMock dependency to the unit test targets.
+
+## SceneKit
+
+Due to SceneKit requiring iOS 8 and OS X 10.9, POP's SceneKit extensions aren't provided out of box. Unfortunately, [weakly linked frameworks](https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPFrameworks/Concepts/WeakLinking.html) cannot be used due to issues mentioned in the [Xcode 6.1 Release Notes](https://developer.apple.com/library/ios/releasenotes/DeveloperTools/RN-Xcode/Chapters/xc6_release_notes.html).
+
+To remedy this, you can easily opt-in to use SceneKit! Simply add this to the Preprocessor Macros section of your Xcode Project:
+
+```
+POP_USE_SCENEKIT=1
+```
+
+## Resources
+
+A collection of links to external resources that may prove valuable:
+
+* [AGGeometryKit+POP - Animating Quadrilaterals with Pop](https://github.com/hfossli/aggeometrykit-pop)
+* [Apple – Core Animation Programming Guide](https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreAnimation_guide/Introduction/Introduction.html)
+* [iOS Development Tips – UIScrollView-like deceleration with Pop](http://iosdevtips.co/post/84571595353/replicating-uiscrollviews-deceleration-with-facebook)
+* [Pop Playground – Repository of Pop animation examples](https://github.com/callmeed/pop-playground)
+* [Pop Playground 2 – Playing with Facebook's framework](http://victorbaro.com/2014/05/pop-playground-playing-with-facebooks-framework/)
+* [POP-MCAnimate – Concise syntax for the Pop animation framework](https://github.com/matthewcheok/POP-MCAnimate)
+* [Popping - Great examples in one project](https://github.com/schneiderandre/popping)
+* [Rebound – Spring Animations for Android](http://facebook.github.io/rebound/)
+* [Tapity Tutorial – Getting Started with Pop](http://tapity.com/tutorial-getting-started-with-pop/)
+* [Tweaks – Easily adjust parameters for iOS apps in development](https://github.com/facebook/tweaks)
+* [POP Tutorial in 5 steps](https://github.com/maxmyers/FacebookPop)
+* [VBFPopFlatButton – Flat animatable button, using Pop to transition between states](https://github.com/victorBaro/VBFPopFlatButton)
+
+## Contributing
+See the CONTRIBUTING file for how to help out.
+
+## License
+
+Pop is released under a BSD License. See LICENSE file for details.

codecov.yml

@@ -0,0 +1,10 @@
+coverage:
+  ignore:
+    - pop-tests/*
+  status:
+    patch: false
+    changes: false
+    project:
+      default:
+        target: 50
+comment: false

pop-tests/POPAnimatable.h

@@ -0,0 +1,28 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <CoreGraphics/CoreGraphics.h>
+
+#import <Foundation/Foundation.h>
+
+#import <QuartzCore/QuartzCore.h>
+
+@interface POPAnimatable : NSObject
+
+@property (nonatomic, assign) float radius;
+
+@property (nonatomic, assign) CGPoint position;
+
+- (NSArray *)recordedValuesForKey:(NSString *)key;
+
+- (void)startRecording;
+
+- (void)stopRecording;
+
+@end

pop-tests/POPAnimatable.mm

@@ -0,0 +1,76 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimatable.h"
+
+#import <pop/POP.h>
+
+@implementation POPAnimatable
+{
+  BOOL _recording;
+  NSMutableDictionary *_recordedValuesDict;
+}
+@synthesize radius = _radius;
+@synthesize position = _position;
+
+static void record_value(POPAnimatable *self, NSString *key, id value)
+{
+  if (!self->_recordedValuesDict) {
+    self->_recordedValuesDict = [NSMutableDictionary new];
+  }
+  NSMutableArray *values = self->_recordedValuesDict[key];
+  if (!values) {
+    values = [NSMutableArray array];
+    self->_recordedValuesDict[key] = values;
+  }
+  [values addObject:value];
+}
+
+static void record_value(POPAnimatable *self, NSString *key, float f)
+{
+  record_value(self, key, @(f));
+}
+
+static void record_value(POPAnimatable *self, NSString *key, CGPoint p)
+{
+  record_value(self, key, [NSValue valueWithCGPoint:p]);
+}
+
+- (void)setRadius:(float)radius
+{
+  _radius = radius;
+  if (_recording) {
+    record_value(self, @"radius", radius);
+  }
+}
+
+- (void)setPosition:(CGPoint)position
+{
+  _position = position;
+  if (_recording) {
+    record_value(self, @"position", position);
+  }
+}
+
+- (NSArray *)recordedValuesForKey:(NSString *)key
+{
+  return _recordedValuesDict[key];
+}
+
+- (void)startRecording
+{
+  _recording = YES;
+}
+
+- (void)stopRecording
+{
+  _recording = NO;
+}
+
+@end

pop-tests/POPAnimatablePropertyTests.mm

@@ -0,0 +1,142 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <XCTest/XCTest.h>
+
+#import <pop/POPAnimatableProperty.h>
+
+static const CGFloat epsilon = 0.0001f;
+static NSArray *properties = @[@"name", @"readBlock", @"writeBlock", @"threshold"];
+
+static void assertPropertyEqual(id self, POPAnimatableProperty *prop1, POPAnimatableProperty *prop2)
+{
+  for (NSString *property in properties) {
+    id value = [prop1 valueForKey:property];
+    id valueCopy = [prop2 valueForKey:property];
+    XCTAssertEqualObjects(value, valueCopy, @"unexpected inequality; value:%@ copy:%@", value, valueCopy);
+  }
+}
+
+@interface POPAnimatablePropertyTests : XCTestCase
+@end
+
+@implementation POPAnimatablePropertyTests
+
+- (void)testProvidedExistence
+{
+  NSArray *names = @[kPOPLayerPosition,
+                     kPOPLayerOpacity,
+                     kPOPLayerScaleXY,
+                     kPOPLayerSubscaleXY,
+                     kPOPLayerSubtranslationX,
+                     kPOPLayerSubtranslationY,
+                     kPOPLayerSubtranslationZ,
+                     kPOPLayerSubtranslationXY,
+                     kPOPLayerZPosition,
+                     kPOPLayerSize,
+                     kPOPLayerRotation,
+                     kPOPLayerRotationY,
+                     kPOPLayerRotationX,
+                     kPOPLayerShadowColor,
+                     kPOPLayerShadowOffset,
+                     kPOPLayerShadowOpacity,
+                     kPOPLayerShadowRadius,
+                     kPOPLayerCornerRadius,
+                     kPOPLayerBorderWidth,
+                     kPOPLayerBorderColor,
+                     kPOPShapeLayerStrokeStart,
+                     kPOPShapeLayerStrokeEnd,
+                     kPOPShapeLayerStrokeColor,
+                     kPOPShapeLayerLineWidth,
+                     kPOPShapeLayerLineDashPhase,
+#if TARGET_OS_IPHONE
+                     kPOPViewAlpha,
+                     kPOPViewBackgroundColor,
+                     kPOPViewCenter,
+                     kPOPViewFrame,
+                     kPOPViewBounds,
+                     kPOPViewSize,
+                     kPOPViewTintColor,
+                     kPOPScrollViewZoomScale,
+                     kPOPTableViewContentSize,
+                     kPOPTableViewContentOffset,
+                     kPOPCollectionViewContentSize,
+                     kPOPCollectionViewContentSize,
+                     kPOPLabelTextColor
+#else
+                     kPOPViewFrame,
+                     kPOPViewBounds,
+                     kPOPViewAlphaValue,
+                     kPOPViewFrameRotation,
+                     kPOPViewFrameCenterRotation,
+                     kPOPViewBoundsRotation,
+                     kPOPWindowFrame,
+                     kPOPWindowAlphaValue,
+                     kPOPWindowBackgroundColor
+#endif
+                     ];
+
+  for (NSString *name in names) {
+    POPAnimatableProperty *prop = [POPAnimatableProperty propertyWithName:name];
+    XCTAssertNotNil(prop, @"animatable property %@ should exist", name);
+  }
+}
+
+- (void)testUserCreation
+{
+  static NSString *name = @"lalalala";
+  static CGFloat threshold = 0.07;
+  POPAnimatableProperty *prop;
+
+  prop = [POPAnimatableProperty propertyWithName:name];
+  XCTAssertNil(prop, @"animatable property %@ should not exist", name);
+
+  prop = [POPAnimatableProperty propertyWithName:name initializer:^(POPMutableAnimatableProperty *p){
+    p.threshold = threshold;
+  }];
+  XCTAssertNotNil(prop, @"animatable property %@ should exist", name);
+  XCTAssertEqualWithAccuracy(threshold, prop.threshold, epsilon, @"property threshold %f should equal %f", prop.threshold, threshold);
+}
+
+- (void)testClassCluster
+{
+  POPAnimatableProperty *instance1 = [[POPAnimatableProperty alloc] init];
+  POPAnimatableProperty *instance2 = [[POPAnimatableProperty alloc] init];
+  XCTAssertTrue(instance1 == instance2, @"instance1:%@ instance2:%@", instance1, instance2);
+
+  for (NSString *property in properties) {
+    XCTAssertNoThrow([instance1 valueForKey:property], @"exception on %@", property);
+  }
+}
+
+- (void)testCopying
+{
+  // instance
+  POPAnimatableProperty *prop = [POPAnimatableProperty propertyWithName:kPOPLayerBounds];
+
+  // instance copy
+  POPAnimatableProperty *propCopy = [prop copy];
+
+  // test equality
+  assertPropertyEqual(self, prop, propCopy);
+}
+
+- (void)testMutableCopying
+{
+  // instance
+  POPAnimatableProperty *prop = [POPAnimatableProperty propertyWithName:kPOPLayerBounds];
+
+  // instance copy
+  POPAnimatableProperty *propCopy = [prop mutableCopy];
+
+  // test equality
+  assertPropertyEqual(self, prop, propCopy);
+}
+
+@end

pop-tests/POPAnimationMRRTests.mm

@@ -0,0 +1,91 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <QuartzCore/QuartzCore.h>
+
+#import <OCMock/OCMock.h>
+
+#import <XCTest/XCTest.h>
+
+#import <pop/POP.h>
+#import <pop/POPAnimatorPrivate.h>
+
+#import "POPAnimationTestsExtras.h"
+
+@interface POPAnimationMRRTests : XCTestCase
+{
+  POPAnimator *_animator;
+  CFTimeInterval _beginTime;
+}
+@end
+
+@implementation POPAnimationMRRTests
+
+- (void)setUp
+{
+  [super setUp];
+  _animator = [[POPAnimator sharedAnimator] retain];
+  _beginTime = CACurrentMediaTime();
+  _animator.beginTime = _beginTime;
+}
+
+- (void)tearDown
+{
+  [_animator release];
+  _animator = nil;
+  [super tearDown];
+}
+
+- (void)testZeroingDelegate
+{
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation();
+
+  @autoreleasepool {
+    id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+    anim.delegate = delegate;
+    XCTAssertNotNil(anim.delegate, @"delegate should not be nil");
+  }
+
+  XCTAssertNil(anim.delegate, @"delegate should be nil");
+}
+
+- (void)testAnimationCancellationOnAnimatableDeallocation
+{
+  id layer = nil;
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation();
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  @autoreleasepool {
+    layer = [OCMockObject niceMockForClass:[CALayer class]];
+    anim.delegate = delegate;
+
+    // expect position start
+    [[delegate expect] pop_animationDidStart:anim];
+
+    // run
+    [layer pop_addAnimation:anim forKey:@""];
+    POPAnimatorRenderTimes(_animator, _beginTime, @[@0.0]);
+
+    // verify
+    [layer verify];
+    [delegate verify];
+
+    // expect stop unfinished
+    [[delegate expect] pop_animationDidStop:anim finished:NO];
+    layer = nil;
+  }
+
+  // run
+  POPAnimatorRenderTimes(_animator, _beginTime, @[@0.5]);
+
+  // verify
+  [delegate verify];
+}
+
+@end

pop-tests/POPAnimationTests.mm

@@ -0,0 +1,891 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <QuartzCore/QuartzCore.h>
+
+#import <OCMock/OCMock.h>
+
+#import <XCTest/XCTest.h>
+
+#import <pop/POP.h>
+#import <pop/POPAnimationPrivate.h>
+#import <pop/POPAnimatorPrivate.h>
+
+#import "POPAnimatable.h"
+#import "POPAnimationRuntime.h"
+#import "POPAnimationTestsExtras.h"
+#import "POPBaseAnimationTests.h"
+#import "POPCGUtils.h"
+#import "POPAnimationInternal.h"
+
+using namespace POP;
+
+@interface POPAnimation (TestExtensions)
+@property (strong, nonatomic) NSString *sampleKey;
+@end
+
+@implementation POPAnimation (TestExtensions)
+- (NSString *)sampleKey { return [self valueForUndefinedKey:@"sampleKey"]; }
+- (void)setSampleKey:(NSString *)aValue { [self setValue:aValue forUndefinedKey:@"sampleKey"];}
+@end
+
+@interface POPAnimationTests : POPBaseAnimationTests
+@end
+
+@implementation POPAnimationTests
+
+- (void)testOrneryAbstractClasses
+{
+  XCTAssertThrows([[POPAnimation alloc] init], @"should not be able to instiate abstract class");
+  XCTAssertThrows([[POPPropertyAnimation alloc] init], @"should not be able to instiate abstract class");
+}
+
+- (void)testWithPropertyNamedConstruction
+{
+  POPSpringAnimation *anim = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerBounds];
+  POPAnimatableProperty *prop = [POPAnimatableProperty propertyWithName:kPOPLayerBounds];
+  XCTAssertTrue(anim.property == prop, @"expected:%@ actual:%@", prop, anim.property);
+}
+
+- (void)testAdditionRemoval
+{
+  CALayer *layer1 = self.layer1;
+  CALayer *layer2 = self.layer2;
+  [layer1 removeAllAnimations];
+  [layer2 removeAllAnimations];
+
+  POPAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  [layer1 pop_addAnimation:anim forKey:@"hello"];
+
+  NSArray *keys = [layer1 pop_animationKeys];
+  XCTAssertTrue(1 == keys.count);
+  XCTAssertTrue([@"hello" isEqualToString:keys.lastObject]);
+
+  [layer1 pop_removeAnimationForKey:@"hello"];
+  XCTAssertTrue(0 == [layer1 pop_animationKeys].count);
+
+  [layer1 pop_addAnimation:FBTestLinearPositionAnimation(self.beginTime) forKey:@"hello"];
+  [layer1 pop_addAnimation:FBTestLinearPositionAnimation(self.beginTime) forKey:@"world"];
+  [layer2 pop_addAnimation:FBTestLinearPositionAnimation(self.beginTime) forKey:@"hello"];
+
+  XCTAssertTrue(2 == [layer1 pop_animationKeys].count);
+  XCTAssertTrue(1 == [layer2 pop_animationKeys].count);
+
+  [layer1 pop_removeAllAnimations];
+  XCTAssertTrue(0 == [layer1 pop_animationKeys].count);
+  XCTAssertTrue(1 == [layer2 pop_animationKeys].count);
+}
+
+- (void)testStartStopDelegation
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // expect start, stop finished
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+  anim.delegate = delegate;
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @1.0]);
+
+  // verify expectations
+  [delegate verify];
+}
+
+- (void)testAnimationValues
+{
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+
+  // avoid fractional values; simplify verification
+  anim.roundingFactor = 1.0;
+
+  id layer = [OCMockObject niceMockForClass:[CALayer class]];
+  [[layer expect] setPosition:FBTestInterpolateLinear(Vector2r([anim.fromValue CGPointValue]), Vector2r([anim.toValue CGPointValue]), 0.25).cg_point()];
+  [[layer expect] setPosition:FBTestInterpolateLinear(Vector2r([anim.fromValue CGPointValue]), Vector2r([anim.toValue CGPointValue]), 0.5).cg_point()];
+  [[layer expect] setPosition:FBTestInterpolateLinear(Vector2r([anim.fromValue CGPointValue]), Vector2r([anim.toValue CGPointValue]), 0.75).cg_point()];
+  [[layer expect] setPosition:[anim.toValue CGPointValue]];
+
+  [layer pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1, 0.25);
+
+  [layer verify];
+}
+
+- (void)testNoAutoreverseRepeatCount0
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  anim.repeatCount = 0;
+  anim.roundingFactor = 1.0;
+  anim.autoreverses = NO;
+
+  NSValue *originalToValue = anim.toValue;
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 2.0, 0.25); // animate longer than needed to verify animation has stopped in the appropriate place
+
+  XCTAssertEqualObjects([layer1 valueForKeyPath:@"position"], originalToValue, @"expected equality; value1:%@ value2:%@", [layer1 valueForKey:@"position"], originalToValue);
+}
+
+- (void)testNoAutoreverseRepeatCount1
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  anim.repeatCount = 1;
+  anim.roundingFactor = 1.0;
+  anim.autoreverses = NO;
+
+  NSValue *originalToValue = anim.toValue;
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3.0, 0.25); // animate longer than needed to verify animation has stopped in the appropriate place
+
+  XCTAssertEqualObjects([layer1 valueForKeyPath:@"position"], originalToValue, @"expected equality; value1:%@ value2:%@", [layer1 valueForKey:@"position"], originalToValue);
+}
+
+- (void)testNoAutoreverseRepeatCount4
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  anim.repeatCount = 4;
+  anim.roundingFactor = 1.0;
+  anim.autoreverses = NO;
+
+  NSValue *originalToValue = anim.toValue;
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 6.0, 0.25); // animate longer than needed to verify animation has stopped in the appropriate place
+
+  XCTAssertEqualObjects([layer1 valueForKeyPath:@"position"], originalToValue, @"expected equality; value1:%@ value2:%@", [layer1 valueForKey:@"position"], originalToValue);
+}
+
+- (void)testAutoreverseRepeatCount0
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  anim.roundingFactor = 1.0;
+  anim.autoreverses = YES;
+  anim.repeatCount = 0;
+  [anim.tracer start];
+
+  NSValue *originalFromValue = anim.fromValue;
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3.0, 0.25); // animate longer than needed to verify animation has stopped in the appropriate place
+
+  XCTAssertEqualObjects([layer1 valueForKey:@"position"], originalFromValue, @"expected equality; value1:%@ value2:%@", [layer1 valueForKey:@"position"], originalFromValue);
+
+  NSArray *autoreversedEvents = [anim.tracer eventsWithType:kPOPAnimationEventAutoreversed];
+  XCTAssertTrue(1 == autoreversedEvents.count, @"unexpected autoreversed events %@", autoreversedEvents);
+
+  anim.autoreverses = NO;
+}
+
+- (void)testAutoreverseRepeatCount1
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  anim.roundingFactor = 1.0;
+  anim.autoreverses = YES;
+  anim.repeatCount = 1;
+  [anim.tracer start];
+
+  NSValue *originalFromValue = anim.fromValue;
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3.0, 0.25); // animate longer than needed to verify animation has stopped in the appropriate place
+
+  XCTAssertEqualObjects([layer1 valueForKey:@"position"], originalFromValue, @"expected equality; value1:%@ value2:%@", [layer1 valueForKey:@"position"], originalFromValue);
+
+  NSArray *autoreversedEvents = [anim.tracer eventsWithType:kPOPAnimationEventAutoreversed];
+  XCTAssertTrue(1 == autoreversedEvents.count, @"unexpected autoreversed events %@", autoreversedEvents);
+
+  anim.autoreverses = NO;
+}
+
+- (void)testAutoreverseRepeatCount4
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  anim.roundingFactor = 1.0;
+  anim.autoreverses = YES;
+
+  NSInteger repeatCount = 4;
+  anim.repeatCount = repeatCount;
+  [anim.tracer start];
+
+  NSValue *originalFromValue = anim.fromValue;
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 9.0, 0.25); // animate longer than needed to verify animation has stopped in the appropriate place
+
+  XCTAssertEqualObjects([layer1 valueForKey:@"position"], originalFromValue, @"expected equality; value1:%@ value2:%@", [layer1 valueForKey:@"position"], originalFromValue);
+
+  NSArray *autoreversedEvents = [anim.tracer eventsWithType:kPOPAnimationEventAutoreversed];
+  XCTAssertTrue((repeatCount * 2) - 1 == (int)autoreversedEvents.count, @"unexpected autoreversed events %@", autoreversedEvents);
+
+  anim.autoreverses = NO;
+}
+
+- (void)testReAddition
+{
+  CALayer *layer1 = self.layer1;
+  CALayer *layer2 = self.layer2;
+  [layer1 removeAllAnimations];
+  [layer2 removeAllAnimations];
+
+  static NSString *key = @"key";
+
+  POPAnimation *anim1, *anim2;
+  id delegate1, delegate2;
+
+  anim1 = FBTestLinearPositionAnimation(self.beginTime);
+  delegate1 = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // expect start, stop not finished
+  [[delegate1 expect] pop_animationDidStart:anim1];
+  [[delegate1 expect] pop_animationDidStop:anim1 finished:NO];
+
+  anim1.delegate = delegate1;
+  [layer1 pop_addAnimation:anim1 forKey:key];
+
+  anim2 = FBTestLinearPositionAnimation(self.beginTime);
+  delegate2 = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // expect start, stop finished
+  [[delegate2 expect] pop_animationDidStart:anim2];
+  [[delegate2 expect] pop_animationDidStop:anim2 finished:YES];
+  anim2.delegate = delegate2;
+
+  // add with same key
+  [layer1 pop_addAnimation:anim2 forKey:key];
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @1.0]);
+
+  // verify expectations
+  [delegate1 verify];
+  [delegate2 verify];
+}
+
+- (void)testAnimationDidStartBlock
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // set animation did start block
+  anim.animationDidStartBlock = ^(POPAnimation *a) {
+    [delegate pop_animationDidStart:a];
+  };
+
+  [[delegate expect] pop_animationDidStart:anim];
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @1.0]);
+  [delegate verify];
+}
+
+- (void)testAnimationDidReachToValueBlock
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // set animation did reach to value block
+  anim.animationDidReachToValueBlock = ^(POPAnimation *a) {
+    [delegate pop_animationDidReachToValue:a];
+  };
+
+  [[delegate expect] pop_animationDidReachToValue:anim];
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @1.0]);
+  [delegate verify];
+}
+
+- (void)testCompletionBlock
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  anim.completionBlock = ^(POPAnimation *a, BOOL finished) {
+    [delegate pop_animationDidStop:a finished:finished];
+  };
+
+  // test for unfinished completion
+  [[delegate expect] pop_animationDidStop:anim finished:NO];
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  [layer1 pop_removeAllAnimations];
+  [delegate verify];
+
+  anim = FBTestLinearPositionAnimation(self.beginTime);
+  delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // set completion block
+  anim.completionBlock = ^(POPAnimation *a, BOOL finished) {
+    [delegate pop_animationDidStop:a finished:finished];
+  };
+
+  // test for finished completion
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @1.0]);
+  [delegate verify];
+}
+
+- (void)testAnimationDidApplyBlock
+{
+  CALayer *layer1 = self.layer1;
+  [layer1 removeAllAnimations];
+
+  POPAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // set animation did apply block
+  anim.animationDidApplyBlock = ^(POPAnimation *a) {
+    [delegate pop_animationDidApply:a];
+  };
+
+  [[delegate expect] pop_animationDidApply:anim];
+
+  [layer1 pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @1.0]);
+  [delegate verify];
+}
+
+- (void)testReuse
+{
+  NSValue *fromValue = [NSValue valueWithCGPoint:CGPointMake(100, 100)];
+  NSValue *toValue = [NSValue valueWithCGPoint:CGPointMake(200, 200)];
+  CGFloat testProgress = 0.25;
+
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  anim.fromValue = fromValue;
+  anim.toValue = toValue;
+  anim.roundingFactor = 1.0;
+
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+  anim.delegate = delegate;
+
+  id layer = [OCMockObject niceMockForClass:[CALayer class]];
+
+  [[layer expect] setPosition:FBTestInterpolateLinear(Vector2r([fromValue CGPointValue]), Vector2r([toValue CGPointValue]), testProgress).cg_point()];
+  [[layer expect] setPosition:[toValue CGPointValue]];
+
+  [layer pop_addAnimation:anim forKey:@"key"];
+
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, [NSNumber numberWithFloat:testProgress * anim.duration], [NSNumber numberWithFloat:anim.duration]]);
+  [layer verify];
+  [delegate verify];
+
+  // new delegate & layer, same animation
+  delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+  anim.delegate = delegate;
+
+  layer = [OCMockObject niceMockForClass:[CALayer class]];
+  
+  [[layer expect] setPosition:FBTestInterpolateLinear(Vector2r([fromValue CGPointValue]), Vector2r([toValue CGPointValue]), testProgress).cg_point()];
+  [[layer expect] setPosition:[toValue CGPointValue]];
+
+  [layer pop_addAnimation:anim forKey:@"key"];
+
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, [NSNumber numberWithFloat:testProgress * anim.duration], [NSNumber numberWithFloat:anim.duration]]);
+  [layer verify];
+
+  [delegate verify];
+}
+
+- (void)testCancelBeforeBegin
+{
+  POPAnimation *anim = FBTestLinearPositionAnimation(self.beginTime + 100000);
+  [anim.tracer start];
+
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@"key"];
+  [layer pop_removeAllAnimations];
+
+  NSArray *didStartEvents = [anim.tracer eventsWithType:kPOPAnimationEventDidStart];
+  NSArray *didStopEvents = [anim.tracer eventsWithType:kPOPAnimationEventDidStop];
+  XCTAssertTrue(1 == didStartEvents.count, @"unexpected start events %@", didStartEvents);
+  XCTAssertTrue(1 == didStopEvents.count, @"unexpected stop events %@", didStopEvents);
+}
+
+- (void)testAddedKeys
+{
+  POPAnimation *anim = FBTestLinearPositionAnimation();
+  anim.sampleKey = @"value";
+  XCTAssertEqualObjects(anim.sampleKey, @"value", @"property value read should equal write");
+}
+
+- (void)testValueTypeResolution
+{
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  XCTAssertNil(anim.fromValue);
+  XCTAssertNil(anim.toValue);
+  XCTAssertNil(anim.velocity);
+
+  id pointValue = [NSValue valueWithCGPoint:CGPointMake(1, 2)];
+  anim.fromValue = pointValue;
+  anim.toValue = pointValue;
+  anim.velocity = pointValue;
+
+  XCTAssertEqualObjects(anim.fromValue, pointValue, @"property value read should equal write");
+  XCTAssertEqualObjects(anim.toValue, pointValue, @"property value read should equal write");
+  XCTAssertEqualObjects(anim.velocity, pointValue, @"property value read should equal write");
+
+  POPSpringAnimation *anim2 = [POPSpringAnimation animation];
+
+  id rectValue = [NSValue valueWithCGRect:CGRectMake(0, 0, 20, 20)];
+  anim2.fromValue = rectValue;
+  anim2.toValue = rectValue;
+  anim2.velocity = rectValue;
+  
+  XCTAssertEqualObjects(anim2.fromValue, rectValue, @"property value read should equal write");
+  XCTAssertEqualObjects(anim2.toValue, rectValue, @"property value read should equal write");
+  XCTAssertEqualObjects(anim2.velocity, rectValue, @"property value read should equal write");
+
+#if TARGET_OS_IPHONE
+
+  POPSpringAnimation *anim3 = [POPSpringAnimation animation];
+
+  id edgeInsetsValue = [NSValue valueWithUIEdgeInsets:UIEdgeInsetsMake(20, 40, 20, 40)];
+  anim3.fromValue = edgeInsetsValue;
+  anim3.toValue = edgeInsetsValue;
+  anim3.velocity = edgeInsetsValue;
+
+  XCTAssertEqualObjects(anim3.fromValue, edgeInsetsValue, @"property value read should equal write");
+  XCTAssertEqualObjects(anim3.toValue, edgeInsetsValue, @"property value read should equal write");
+  XCTAssertEqualObjects(anim3.velocity, edgeInsetsValue, @"property value read should equal write");
+
+#endif
+
+  POPSpringAnimation *anim4 = [POPSpringAnimation animation];
+  id transformValue = [NSValue valueWithCATransform3D:CATransform3DIdentity];
+  XCTAssertThrows(anim4.fromValue = transformValue, @"should not be able to set %@", transformValue);
+}
+
+- (void)testTracer
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  POPAnimationTracer *tracer = anim.tracer;
+  XCTAssertNotNil(tracer, @"missing tracer");
+  [tracer start];
+
+  NSNumber *animFromValue = @0.0;
+  NSNumber *animToValue = @1.0;
+  NSNumber *animVelocity = @0.1;
+  float animBounciness = 4.1;
+  float animSpeed = 13.0;
+  float animFriction = 123.;
+  float animMass = 0.9;
+  float animTension = 401.;
+
+  anim.property = self.radiusProperty;
+  anim.fromValue = animFromValue;
+  anim.toValue = animToValue;
+  anim.velocity = animVelocity;
+  anim.dynamicsFriction = animFriction;
+  anim.dynamicsMass = animMass;
+  anim.dynamicsTension = animTension;
+  anim.springBounciness = animBounciness;
+  anim.springSpeed = animSpeed;
+
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 5, 0.01);
+  [tracer stop];
+
+  NSArray *allEvents = tracer.allEvents;
+  NSArray *fromEvents = [tracer eventsWithType:kPOPAnimationEventFromValueUpdate];
+  NSArray *toEvents = [tracer eventsWithType:kPOPAnimationEventToValueUpdate];
+  NSArray *velocityEvents = [tracer eventsWithType:kPOPAnimationEventVelocityUpdate];
+  NSArray *bouncinessEvents = [tracer eventsWithType:kPOPAnimationEventBouncinessUpdate];
+  NSArray *speedEvents = [tracer eventsWithType:kPOPAnimationEventSpeedUpdate];
+  NSArray *frictionEvents = [tracer eventsWithType:kPOPAnimationEventFrictionUpdate];
+  NSArray *massEvents = [tracer eventsWithType:kPOPAnimationEventMassUpdate];
+  NSArray *tensionEvents = [tracer eventsWithType:kPOPAnimationEventTensionUpdate];
+  NSArray *startEvents = [tracer eventsWithType:kPOPAnimationEventDidStart];
+  NSArray *stopEvents = [tracer eventsWithType:kPOPAnimationEventDidStop];
+  NSArray *didReachEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+
+  // all events
+  XCTAssertTrue(0 != allEvents.count, @"unexpected allEvents count %@", allEvents);
+
+  // from events
+  XCTAssertTrue(1 == fromEvents.count, @"unexpected fromEvents count %@", fromEvents);
+  id eventFromValue = [(POPAnimationValueEvent *)fromEvents.lastObject value];
+  XCTAssertEqualObjects(animFromValue, eventFromValue, @"unexpected eventFromValue; expected:%@ actual:%@", animFromValue, eventFromValue);
+
+  // to events
+  XCTAssertTrue(1 == toEvents.count, @"unexpected toEvents count %@", toEvents);
+  id eventToValue = [(POPAnimationValueEvent *)toEvents.lastObject value];
+  XCTAssertEqualObjects(animToValue, eventToValue, @"unexpected eventToValue; expected:%@ actual:%@", animToValue, eventToValue);
+
+  // velocity events
+  XCTAssertTrue(1 == velocityEvents.count, @"unexpected velocityEvents count %@", velocityEvents);
+  id eventVelocity = [(POPAnimationValueEvent *)velocityEvents.lastObject value];
+  XCTAssertEqualObjects(animVelocity, eventVelocity, @"unexpected eventVelocity; expected:%@ actual:%@", animVelocity, eventVelocity);
+
+  // bounciness events
+  XCTAssertTrue(1 == bouncinessEvents.count, @"unexpected bouncinessEvents count %@", bouncinessEvents);
+  id eventBounciness = [(POPAnimationValueEvent *)bouncinessEvents.lastObject value];
+  XCTAssertEqualObjects(@(animBounciness), eventBounciness, @"unexpected bounciness; expected:%@ actual:%@", @(animBounciness), eventBounciness);
+
+  // speed events
+  XCTAssertTrue(1 == speedEvents.count, @"unexpected speedEvents count %@", speedEvents);
+  id eventSpeed = [(POPAnimationValueEvent *)speedEvents.lastObject value];
+  XCTAssertEqualObjects(@(animSpeed), eventSpeed, @"unexpected speed; expected:%@ actual:%@", @(animSpeed), eventSpeed);
+
+  // friction events
+  XCTAssertTrue(1 == frictionEvents.count, @"unexpected frictionEvents count %@", frictionEvents);
+  id eventFriction = [(POPAnimationValueEvent *)frictionEvents.lastObject value];
+  XCTAssertEqualObjects(@(animFriction), eventFriction, @"unexpected friction; expected:%@ actual:%@", @(animFriction), eventFriction);
+
+  // mass events
+  XCTAssertTrue(1 == massEvents.count, @"unexpected massEvents count %@", massEvents);
+  id eventMass = [(POPAnimationValueEvent *)massEvents.lastObject value];
+  XCTAssertEqualObjects(@(animMass), eventMass, @"unexpected mass; expected:%@ actual:%@", @(animMass), eventMass);
+
+  // tension events
+  XCTAssertTrue(1 == tensionEvents.count, @"unexpected tensionEvents count %@", tensionEvents);
+  id eventTension = [(POPAnimationValueEvent *)tensionEvents.lastObject value];
+  XCTAssertEqualObjects(@(animTension), eventTension, @"unexpected tension; expected:%@ actual:%@", @(animTension), eventTension);
+
+  // start & stop event
+  XCTAssertTrue(1 == startEvents.count, @"unexpected startEvents count %@", startEvents);
+  XCTAssertTrue(1 == stopEvents.count, @"unexpected stopEvents count %@", stopEvents);
+
+  // start before stop
+  NSUInteger startIdx = [allEvents indexOfObjectIdenticalTo:startEvents.firstObject];
+  NSUInteger stopIdx = [allEvents indexOfObjectIdenticalTo:stopEvents.firstObject];
+  XCTAssertTrue(startIdx < stopIdx, @"unexpected start/stop ordering startIdx:%lu stopIdx:%lu", (unsigned long)startIdx, (unsigned long)stopIdx);
+
+  // did reach event
+  XCTAssertTrue(1 == didReachEvents.count, @"unexpected didReachEvents %@", didReachEvents);
+
+  // did reach after start before stop
+  NSUInteger didReachIdx = [allEvents indexOfObjectIdenticalTo:didReachEvents.firstObject];
+  XCTAssertTrue(didReachIdx > startIdx, @"unexpected didReach/start ordering didReachIdx:%lu startIdx:%lu", (unsigned long)didReachIdx, (unsigned long)startIdx);
+  XCTAssertTrue(didReachIdx < stopIdx, @"unexpected didReach/stop ordering didReachIdx:%lu stopIdx:%lu", (unsigned long)didReachIdx, (unsigned long)stopIdx);
+
+  // write events
+  XCTAssertTrue(0 != writeEvents.count, @"unexpected writeEvents count %@", writeEvents);
+  id firstWriteValue = [(POPAnimationValueEvent *)writeEvents.firstObject value];
+  XCTAssertTrue(NSOrderedSame == [anim.fromValue compare:firstWriteValue], @"unexpected firstWriteValue; fromValue:%@ actual:%@", anim.fromValue, firstWriteValue);
+  id lastWriteValue = [(POPAnimationValueEvent *)writeEvents.lastObject value];
+  XCTAssertEqualObjects(lastWriteValue, anim.toValue, @"unexpected lastWriteValue; expected:%@ actual:%@", anim.toValue, lastWriteValue);
+}
+
+- (void)testAnimationContinuation
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = self.radiusProperty;
+  anim.fromValue = @0.0;
+  anim.toValue = @1.0;
+  anim.velocity = @10.0;
+  anim.springBounciness = 4;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 0.25, 0.05);
+
+  NSArray *didReachToEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+  NSArray *stopEvents = [tracer eventsWithType:kPOPAnimationEventDidStop];
+
+  // assert did reach but not stop
+  XCTAssertTrue(1 == didReachToEvents.count, @"unexpected didReachToEvents count %@", didReachToEvents);
+  XCTAssertTrue(0 == stopEvents.count, @"unexpected stopEvents count %@", stopEvents);
+
+  // update to value continuing animation
+  anim.toValue = @0.0;
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 2.0, 0.1);
+  [tracer stop];
+
+  // two did reach to events
+  didReachToEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+  XCTAssertTrue(2 == didReachToEvents.count, @"unexpected didReachToEvents count %@", didReachToEvents);
+
+  // first event value > animation to value
+  id firstDidReachValue = [(POPAnimationValueEvent *)didReachToEvents.firstObject value];
+  XCTAssertTrue(NSOrderedAscending == [anim.toValue compare:firstDidReachValue], @"unexpected firstDidReachValue; toValue:%@ actual:%@", anim.toValue, firstDidReachValue);
+
+  // second event value < animation to value
+  id lastDidReachValue = [(POPAnimationValueEvent *)didReachToEvents.lastObject value];
+  XCTAssertTrue(NSOrderedDescending == [anim.toValue compare:lastDidReachValue], @"unexpected lastDidReachValue; toValue:%@ actual:%@", anim.toValue, lastDidReachValue);
+
+  // did stop event
+  stopEvents = [tracer eventsWithType:kPOPAnimationEventDidStop];
+  XCTAssertTrue(1 == stopEvents.count, @"unexpected stopEvents count %@", stopEvents);
+  XCTAssertEqualObjects([(POPAnimationValueEvent *)stopEvents.lastObject value], @YES, @"unexpected stop event: %@", stopEvents.lastObject);
+}
+
+- (void)testRoundingFactor
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  
+  {
+    // non retina, additive & non-additive
+    BOOL additive = NO;
+    
+  LStart:
+    POPBasicAnimation *anim = [POPBasicAnimation animation];
+    anim.property = self.radiusProperty;
+    anim.fromValue = @0.0;
+    anim.toValue = @1.0;
+    anim.roundingFactor = 1.0;
+    anim.additive = additive;
+
+    POPAnimationTracer *tracer = anim.tracer;
+    [tracer start];
+
+    [circle pop_addAnimation:anim forKey:@"key"];
+    POPAnimatorRenderDuration(self.animator, self.beginTime, 0.25, 0.05);
+
+    NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+    BOOL containValue = POPAnimationEventsContainValue(writeEvents, @0.5);
+    XCTAssertFalse(containValue, @"unexpected write value %@", writeEvents);
+
+    if (!additive) {
+      additive = YES;
+      goto LStart;
+    }
+  }
+
+  {
+    // retina, additive & non-additive
+    BOOL additive = NO;
+    
+  LStartRetina:
+    POPBasicAnimation *anim = [POPBasicAnimation animation];
+    anim.property = self.radiusProperty;
+    anim.fromValue = @0.0;
+    anim.toValue = @1.0;
+    anim.roundingFactor = 0.5;
+
+    POPAnimationTracer *tracer = anim.tracer;
+    [tracer start];
+
+    [circle pop_addAnimation:anim forKey:@"key"];
+    POPAnimatorRenderDuration(self.animator, self.beginTime, 0.25, 0.05);
+
+    NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+    BOOL containValue = POPAnimationEventsContainValue(writeEvents, @0.5);
+    XCTAssertTrue(containValue, @"unexpected write value %@", writeEvents);
+
+    if (!additive) {
+      additive = YES;
+      goto LStartRetina;
+    }
+  }
+}
+
+- (void)testAdditiveAnimation
+{
+  const CGFloat baseValue = 1.;
+  const CGFloat fromValue = 1.;
+  const CGFloat toValue = 2.;
+  
+  POPAnimatable *circle = [POPAnimatable new];
+  circle.radius = baseValue;
+  
+  POPBasicAnimation *anim;
+  anim = [POPBasicAnimation animation];
+  anim.property = self.radiusProperty;
+  anim.fromValue = @(fromValue);
+  anim.toValue = @(toValue);
+  anim.additive = YES;
+  
+  [circle startRecording];
+  [circle pop_addAnimation:anim forKey:@"key1"];
+  
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 0.5, 0.05);
+
+  NSArray *writeEvents = [circle recordedValuesForKey:@"radius"];
+  CGFloat firstValue = [[writeEvents firstObject] floatValue];
+  CGFloat lastValue = [[writeEvents lastObject] floatValue];
+  
+  XCTAssertTrue(firstValue >= baseValue + fromValue, @"write value expected:%f actual:%f", baseValue + fromValue, firstValue);
+  XCTAssertTrue(lastValue == baseValue + toValue, @"write value expected:%f actual:%f", baseValue + toValue, lastValue);
+}
+
+- (void)testNilKey
+{
+  POPBasicAnimation *anim = FBTestLinearPositionAnimation(self.beginTime);
+  
+  // avoid fractional values; simplify verification
+  anim.roundingFactor = 1.0;
+  
+  id layer = [OCMockObject niceMockForClass:[CALayer class]];
+  [[layer expect] setPosition:FBTestInterpolateLinear(Vector2r([anim.fromValue CGPointValue]), Vector2r([anim.toValue CGPointValue]), 0.25).cg_point()];
+  [[layer expect] setPosition:FBTestInterpolateLinear(Vector2r([anim.fromValue CGPointValue]), Vector2r([anim.toValue CGPointValue]), 0.5).cg_point()];
+  [[layer expect] setPosition:FBTestInterpolateLinear(Vector2r([anim.fromValue CGPointValue]), Vector2r([anim.toValue CGPointValue]), 0.75).cg_point()];
+  [[layer expect] setPosition:[anim.toValue CGPointValue]];
+  
+  // verify nil key can be added, same as CA
+  [layer pop_addAnimation:anim forKey:nil];
+  
+  // verify attempting to remove nil key is a noop, same as CA
+  XCTAssertNoThrow([layer pop_removeAnimationForKey:nil], @"unexpected exception");
+
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1, 0.25);
+  [layer verify];
+}
+
+- (void)testIntegerAnimation
+{
+  const int toValue = 1;
+  NSNumber *boxedToValue = @1.0;
+
+  POPBasicAnimation *anim;
+
+  // literal
+  anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerOpacity];
+  XCTAssertNoThrow(anim.toValue = @(toValue), @"unexpected exception");
+  XCTAssertEqualObjects(anim.toValue, boxedToValue, @"expected equality; value1:%@ value2:%@", anim.toValue, boxedToValue);
+
+  // integer
+  anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerOpacity];
+  XCTAssertNoThrow(anim.toValue = @(toValue), @"unexpected exception");
+  XCTAssertEqualObjects(anim.toValue, boxedToValue, @"expected equality; value1:%@ value2:%@", anim.toValue, boxedToValue);
+
+  // short
+  anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerOpacity];
+  XCTAssertNoThrow(anim.toValue = @(toValue), @"unexpected exception");
+  XCTAssertEqualObjects(anim.toValue, boxedToValue, @"expected equality; value1:%@ value2:%@", anim.toValue, boxedToValue);
+
+  // unsigned short
+  anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerOpacity];
+  XCTAssertNoThrow(anim.toValue = @(toValue), @"unexpected exception");
+  XCTAssertEqualObjects(anim.toValue, boxedToValue, @"expected equality; value1:%@ value2:%@", anim.toValue, boxedToValue);
+
+  // int
+  anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerOpacity];
+  XCTAssertNoThrow(anim.toValue = @(toValue), @"unexpected exception");
+  XCTAssertEqualObjects(anim.toValue, boxedToValue, @"expected equality; value1:%@ value2:%@", anim.toValue, boxedToValue);
+
+  // unsigned int
+  anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerOpacity];
+  XCTAssertNoThrow(anim.toValue = @(toValue), @"unexpected exception");
+  XCTAssertEqualObjects(anim.toValue, boxedToValue, @"expected equality; value1:%@ value2:%@", anim.toValue, boxedToValue);
+
+  // long
+  anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerOpacity];
+  XCTAssertNoThrow(anim.toValue = @(toValue), @"unexpected exception");
+  XCTAssertEqualObjects(anim.toValue, boxedToValue, @"expected equality; value1:%@ value2:%@", anim.toValue, boxedToValue);
+
+  // unsigned long
+  anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerOpacity];
+  XCTAssertNoThrow(anim.toValue = @(toValue), @"unexpected exception");
+  XCTAssertEqualObjects(anim.toValue, boxedToValue, @"expected equality; value1:%@ value2:%@", anim.toValue, boxedToValue);
+
+  anim.fromValue = @0;
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:nil];
+
+  POPAnimatorRenderDuration(self.animator, self.beginTime + 0.1, 1, 0.1);
+
+  // verify writes happened
+  NSArray *writeEvents = tracer.writeEvents;
+  XCTAssertTrue(writeEvents.count == 5, @"unexpected events:%@", writeEvents);
+
+  // verify initial value
+  POPAnimationValueEvent *firstWriteEvent = writeEvents.firstObject;
+  XCTAssertTrue([firstWriteEvent.value isEqual:anim.fromValue], @"expected equality; value1:%@ value%@", firstWriteEvent.value, anim.fromValue);
+
+  // verify final value
+  XCTAssertEqualObjects([layer valueForKey:@"opacity"], anim.toValue, @"expected equality; value1:%@ value2:%@", [layer valueForKey:@"opacity"], anim.toValue);
+}
+
+- (void)testPlatformColorSupport
+{
+  POPSpringAnimation *anim = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerBackgroundColor];
+
+#if TARGET_OS_IPHONE
+  XCTAssertNoThrow(anim.fromValue = [UIColor whiteColor], @"unexpected exception");
+  XCTAssertNoThrow(anim.toValue = [UIColor redColor], @"unexpected exception");
+#else
+  XCTAssertNoThrow(anim.fromValue = [NSColor whiteColor], @"unexpected exception");
+  XCTAssertNoThrow(anim.toValue = [NSColor redColor], @"unexpected exception");
+#endif
+  
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+  
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@"color"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1, 0.1);
+
+  // expect some interpolation
+  NSArray *writeEvents = tracer.writeEvents;
+  XCTAssertTrue(writeEvents.count > 1, @"unexpected write events %@", writeEvents);
+
+  // get layer color components
+  CGFloat layerValues[4];
+  POPCGColorGetRGBAComponents(layer.backgroundColor, layerValues);
+
+  // get to color components
+  CGFloat toValues[4];
+  POPCGColorGetRGBAComponents((__bridge CGColorRef)anim.toValue, toValues);
+
+  // assert equality
+  XCTAssertTrue(layerValues[0] == toValues[0] && layerValues[1] == toValues[1] && layerValues[2] == toValues[2] && layerValues[3] == toValues[3], @"unexpected last color: [r:%f g:%f b:%f a:%f]", layerValues[0], layerValues[1], layerValues[2], layerValues[3]);
+}
+
+- (void)testNSCopyingSupportPOPBasicAnimation
+{
+  POPBasicAnimation *anim = [POPBasicAnimation animationWithPropertyNamed:@"test_property_name"];
+  
+  configureConcretePropertyAnimation(anim);
+  [self testCopyingSucceedsForConcretePropertyAnimation:anim];
+  
+  anim.duration = 1.8;
+  anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
+  
+  POPBasicAnimation *copy = [anim copy];
+  
+  XCTAssertEqual(copy.duration, anim.duration, @"expected equality; value1:%@ value2:%@", @(copy.duration), @(anim.duration));
+  XCTAssertEqualObjects(copy.timingFunction, anim.timingFunction, @"expected equality; value1:%@ value2:%@", copy.timingFunction, anim.timingFunction);
+}
+
+@end

pop-tests/POPAnimationTestsExtras.h

@@ -0,0 +1,19 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPVector.h"
+@class POPAnimator;
+@class POPBasicAnimation;
+
+extern void POPAnimatorRenderTime(POPAnimator *animator, CFTimeInterval beginTime, CFTimeInterval time);
+extern void POPAnimatorRenderTimes(POPAnimator *animator, CFTimeInterval beginTime, NSArray *times);
+extern void POPAnimatorRenderDuration(POPAnimator *animator, CFAbsoluteTime beginTime, CFTimeInterval duration, CFTimeInterval step);
+
+extern POPBasicAnimation *FBTestLinearPositionAnimation(CFTimeInterval beginTime = 0);
+extern POP::Vector2r FBTestInterpolateLinear(POP::Vector2r start, POP::Vector2r end, CGFloat progress);

pop-tests/POPAnimationTestsExtras.mm

@@ -0,0 +1,54 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimationTestsExtras.h"
+
+#import <pop/POP.h>
+#import <pop/POPAnimatorPrivate.h>
+
+void POPAnimatorRenderTime(POPAnimator *animator, CFTimeInterval beginTime, CFTimeInterval time)
+{
+  [animator renderTime:beginTime + time];
+}
+
+void POPAnimatorRenderTimes(POPAnimator *animator, CFTimeInterval beginTime, NSArray *times)
+{
+  for (NSNumber *time in times) {
+    [animator renderTime:beginTime + time.doubleValue];
+  }
+}
+
+void POPAnimatorRenderDuration(POPAnimator *animator, CFTimeInterval beginTime, CFTimeInterval duration, CFTimeInterval step)
+{
+  CFTimeInterval initialTime = animator.beginTime;
+  animator.beginTime = beginTime;
+  NSCAssert(step > 0, @"unexpected step %f", step);
+  CFTimeInterval time = 0;
+  while(time <= duration) {
+    [animator renderTime:beginTime + time];
+    time += step;
+  }
+  animator.beginTime = initialTime;
+}
+
+POPBasicAnimation *FBTestLinearPositionAnimation(CFTimeInterval beginTime)
+{
+  POPBasicAnimation *anim = [POPBasicAnimation linearAnimation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPosition];
+  anim.fromValue = [NSValue valueWithCGPoint:CGPointMake(0, 0)];
+  anim.toValue = [NSValue valueWithCGPoint:CGPointMake(100, 100)];
+  anim.duration = 1;
+  anim.beginTime = beginTime;
+  return anim;
+}
+
+POP::Vector2r FBTestInterpolateLinear(POP::Vector2r start, POP::Vector2r end, CGFloat progress)
+{
+  return start + ((end - start) * progress);
+}

pop-tests/POPBaseAnimationTests.h

@@ -0,0 +1,63 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <cmath>
+
+#import <XCTest/XCTest.h>
+
+#import "POPCGUtils.h"
+
+@class CALayer;
+@class POPAnimator;
+@class POPAnimatableProperty;
+@class POPAnimation;
+@class POPPropertyAnimation;
+
+@interface POPBaseAnimationTests : XCTestCase
+
+// two layers for test use
+@property (strong, nonatomic) CALayer *layer1, *layer2;
+
+// the animator to use for rendering
+@property (strong, nonatomic) POPAnimator *animator;
+
+// the time tests began
+@property (assign, nonatomic) CFTimeInterval beginTime;
+
+// radius animatable property
+@property (strong, nonatomic) POPAnimatableProperty *radiusProperty;
+
+- (void)testCopyingSucceedsForConcreteAnimation:(POPAnimation *)anim;
+- (void)testCopyingSucceedsForConcretePropertyAnimation:(POPPropertyAnimation *)anim;
+
+@end
+
+// max frame count required for animations to converge
+extern NSUInteger kPOPAnimationConvergenceMaxFrameCount;
+
+// counts the number of events of value within epsilon, starting from end
+extern NSUInteger POPAnimationCountLastEventValues(NSArray *events, NSNumber *value, float epsilon = 0);
+
+// returns YES if array of value events contain specified value
+extern BOOL POPAnimationEventsContainValue(NSArray *events, NSNumber *value);
+
+// equality with epsilon
+#define _EQL_(x, y, epsilon) (std::abs ((x) - (y)) < epsilon)
+
+// color equality assert
+#define POPAssertColorEqual(c1, c2) \
+{ \
+  CGFloat v1[4], v2[4]; \
+  POPCGColorGetRGBAComponents(c1, v1); \
+  POPCGColorGetRGBAComponents(c2, v2); \
+  XCTAssertTrue(_EQL_(v1[0], v2[0], 1e-6) && _EQL_(v1[1], v2[1], 1e-6) && _EQL_(v1[2], v2[2], 1e-6) && _EQL_(v1[3], v2[3], 1e-6), @"not equal color:[r:%f g:%f b:%f a:%f] color:[r:%f g:%f b:%f a:%f]", v1[0], v1[1], v1[2], v1[3], v2[0], v2[1], v2[2], v2[3]); \
+}
+
+extern void configureConcreteAnimation(POPAnimation *anim);
+extern void configureConcretePropertyAnimation(POPPropertyAnimation *anim);

pop-tests/POPBaseAnimationTests.mm

@@ -0,0 +1,147 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPBaseAnimationTests.h"
+
+#import <QuartzCore/QuartzCore.h>
+
+#import <OCMock/OCMock.h>
+
+#import <pop/POP.h>
+#import <pop/POPAnimatorPrivate.h>
+
+#import "POPAnimatable.h"
+#import "POPAnimationTestsExtras.h"
+#import "POPAnimationInternal.h"
+
+@implementation POPBaseAnimationTests
+{
+  CALayer *_layer1;
+  CALayer *_layer2;
+  POPAnimator *_animator;
+  CFTimeInterval _beginTime;
+  POPAnimatableProperty *_radiusProperty;
+  id delegate;
+}
+@synthesize layer1 = _layer1;
+@synthesize layer2 = _layer2;
+@synthesize animator = _animator;
+@synthesize beginTime = _beginTime;
+@synthesize radiusProperty = _radiusProperty;
+
+- (void)setUp
+{
+  [super setUp];
+  _layer1 = [[CALayer alloc] init];
+  _layer2 = [[CALayer alloc] init];
+  _animator = [POPAnimator sharedAnimator];
+  _radiusProperty = [POPAnimatableProperty propertyWithName:@"radius" initializer:^(POPMutableAnimatableProperty *prop){
+    prop.readBlock = ^(POPAnimatable *obj, CGFloat values[]) {
+      values[0] = [obj radius];
+    };
+    prop.writeBlock = ^(POPAnimatable *obj, const CGFloat values[]) {
+      obj.radius = values[0];
+    };
+    prop.threshold = 0.01;
+  }];
+  _beginTime = CACurrentMediaTime();
+  _animator.beginTime = _beginTime;
+}
+
+- (void)testCopyingSucceedsForConcreteAnimation:(POPAnimation *)anim
+{
+  POPAnimation *copy = [anim copy];
+  
+  XCTAssertEqualObjects(copy.name, anim.name, @"expected equality; value1:%@ value2:%@", copy.name, anim.name);
+  XCTAssertEqual(copy.beginTime, anim.beginTime, @"expected equality; value1:%@ value2:%@", @(copy.beginTime), @(anim.beginTime));
+  XCTAssertEqualObjects(copy.delegate, anim.delegate, @"expected equality; value1:%@ value2:%@", copy.delegate, anim.delegate);
+  XCTAssertEqualObjects(copy.animationDidStartBlock, anim.animationDidStartBlock, @"expected equality; value1:%@ value2:%@", copy.animationDidStartBlock, anim.animationDidStartBlock);
+  XCTAssertEqualObjects(copy.animationDidReachToValueBlock, anim.animationDidReachToValueBlock, @"expected equality; value1:%@ value2:%@", copy.animationDidReachToValueBlock, anim.animationDidReachToValueBlock);
+  XCTAssertEqualObjects(copy.completionBlock, anim.completionBlock, @"expected equality; value1:%@ value2:%@", copy.completionBlock, anim.completionBlock);
+  XCTAssertEqualObjects(copy.animationDidApplyBlock, anim.animationDidApplyBlock, @"expected equality; value1:%@ value2:%@", copy.animationDidApplyBlock, anim.animationDidApplyBlock);
+  XCTAssertEqual(copy.removedOnCompletion, anim.removedOnCompletion, @"expected equality; value1:%@ value2:%@", @(copy.removedOnCompletion), @(anim.removedOnCompletion));
+  XCTAssertEqual(copy.autoreverses, anim.autoreverses, @"expected equality; value1:%@ value2:%@", @(copy.autoreverses), @(anim.autoreverses));
+  XCTAssertEqual(copy.repeatCount, anim.repeatCount, @"expected equality; value1:%@ value2:%@", @(copy.repeatCount), @(anim.repeatCount));
+  XCTAssertEqual(copy.repeatForever, anim.repeatForever, @"expected equality; value1:%@ value2:%@", @(copy.repeatForever), @(anim.repeatForever));
+}
+
+- (void)testCopyingSucceedsForConcretePropertyAnimation:(POPPropertyAnimation *)anim
+{
+  [self testCopyingSucceedsForConcreteAnimation:anim];
+  
+  POPPropertyAnimation *copy = [anim copy];
+  
+  XCTAssertEqualObjects(copy.fromValue, anim.fromValue, @"expected equality; value1:%@ value2:%@", copy.fromValue, anim.fromValue);
+  XCTAssertEqualObjects(copy.toValue, anim.toValue, @"expected equality; value1:%@ value2:%@", copy.toValue, anim.toValue);
+  XCTAssertEqual(copy.roundingFactor, anim.roundingFactor, @"expected equality; value1:%@ value2:%@", @(copy.roundingFactor), @(anim.roundingFactor));
+  XCTAssertEqual(copy.clampMode, anim.clampMode, @"expected equality; value1:%@ value2:%@", @(copy.clampMode), @(anim.clampMode));
+  XCTAssertEqual(copy.additive, anim.additive, @"expected equality; value1:%@ value2:%@", @(copy.additive), @(anim.additive));
+}
+
+@end
+
+NSUInteger kPOPAnimationConvergenceMaxFrameCount = 12; // 12 frames, ~200ms at 1/60fps, the user perseption threshold
+
+NSUInteger POPAnimationCountLastEventValues(NSArray *events, NSNumber *value, float epsilon)
+{
+  __block NSUInteger count = 0;
+  [events enumerateObjectsWithOptions:NSEnumerationReverse usingBlock:^(POPAnimationValueEvent *event, NSUInteger idx, BOOL *ptrStop) {
+
+    BOOL match = 0 == epsilon ? [event.value isEqualToValue:value] : fabsf([event.value floatValue] - [value floatValue]) < epsilon;
+    if (!match) {
+      *ptrStop = YES;
+    } else {
+      count++;
+    }
+  }];
+  return count;
+}
+
+BOOL POPAnimationEventsContainValue(NSArray *events, NSNumber *value)
+{
+  for (POPAnimationValueEvent *event in events) {
+    if ([event.value isEqual:value]) {
+      return YES;
+    }
+  }
+  return NO;
+}
+
+void configureConcreteAnimation(POPAnimation *anim)
+{
+  static id delegate = [NSObject new];
+  
+  anim.name = @"pop_animation_copy_test";
+  anim.beginTime = 1.234;
+  anim.delegate = delegate; // dummy delegate
+  anim.animationDidStartBlock = ^(POPAnimation *a){ NSLog(@"Animation Did Start"); };
+  anim.animationDidReachToValueBlock = ^(POPAnimation *a){ NSLog(@"Animation Did Reach To Value"); };
+  anim.completionBlock = ^(POPAnimation *a, BOOL finished){ NSLog(@"Animation Finished"); };
+  anim.animationDidApplyBlock = ^(POPAnimation *){ NSLog(@"Animation Applied"); };
+  anim.removedOnCompletion = NO; // not default
+  anim.autoreverses = YES; // not default
+  anim.repeatCount = 42;
+  anim.repeatForever = YES; // not default
+}
+
+void configureConcretePropertyAnimation(POPPropertyAnimation *anim)
+{
+  configureConcreteAnimation(anim);
+  
+  // Decay animations don't use fromValue, so setting it here causes issues.
+  if (![anim isMemberOfClass:[POPDecayAnimation class]]) {
+    
+    anim.fromValue = @(12345);
+  }
+  
+  anim.toValue = @(77888);
+  anim.roundingFactor = 0.257;
+  anim.clampMode = 87;
+  anim.additive = YES; // not default
+}

pop-tests/POPBasicAnimationTests.mm

@@ -0,0 +1,162 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <XCTest/XCTest.h>
+
+#import <OCMock/OCMock.h>
+#import <pop/POPBasicAnimation.h>
+
+#import "POPAnimatable.h"
+#import "POPAnimationTestsExtras.h"
+#import "POPBaseAnimationTests.h"
+
+@interface POPBasicAnimationTests : POPBaseAnimationTests
+
+@end
+
+@implementation POPBasicAnimationTests
+
+- (void)testGreaterThanOneControlPointC1Y
+{
+  POPBasicAnimation *anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerPositionX];
+  anim.fromValue = @0;
+  anim.toValue = @100;
+  anim.timingFunction = [CAMediaTimingFunction functionWithControlPoints:0.15f :1.5f :0.55f :1.0f];
+  anim.duration = 0.36;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:nil];
+
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  // verify write count
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  XCTAssertTrue(writeEvents.count > 10, @"expected more write events %@", tracer.allEvents);
+  
+  // verify last written value is equal to animation to value
+  id lastValue = [(POPAnimationValueEvent *)writeEvents.lastObject value];
+  XCTAssertEqualObjects(lastValue, anim.toValue, @"expected more write events %@", tracer.allEvents);
+  
+  // verify last written value is less than previous value
+  id prevLastValue = [(POPAnimationValueEvent *)writeEvents[writeEvents.count - 2] value];
+  XCTAssertTrue(NSOrderedDescending == [prevLastValue compare:lastValue], @"unexpected lastValue; prevLastValue:%@ events:%@", prevLastValue, tracer.allEvents);
+}
+
+- (void)testColorInterpolation
+{
+  POPBasicAnimation *anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerBackgroundColor];
+
+#if TARGET_OS_IPHONE
+  anim.fromValue = [UIColor whiteColor];
+  anim.toValue = [UIColor redColor];
+#else
+  anim.fromValue = [NSColor whiteColor];
+  anim.toValue = [NSColor redColor];
+#endif
+  
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:nil];
+
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  // verify write events
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  XCTAssertTrue(writeEvents.count > 5, @"expected more write events %@", tracer.allEvents);
+
+  // assert final value
+  POPAssertColorEqual((__bridge CGColorRef)anim.toValue, layer.backgroundColor);
+}
+
+- (void)testZeroDurationAnimation
+{
+    POPBasicAnimation *anim = [POPBasicAnimation animationWithPropertyNamed:kPOPLayerBackgroundColor];
+    anim.duration = 0.0f;
+    
+#if TARGET_OS_IPHONE
+    anim.fromValue = [UIColor whiteColor];
+    anim.toValue = [UIColor redColor];
+#else
+    anim.fromValue = [NSColor whiteColor];
+    anim.toValue = [NSColor redColor];
+#endif
+    
+    POPAnimationTracer *tracer = anim.tracer;
+    [tracer start];
+    
+    CALayer *layer = [CALayer layer];
+    [layer pop_addAnimation:anim forKey:nil];
+    
+    // run animation
+    POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+    
+    // verify write events
+    NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+    XCTAssertTrue(writeEvents.count == 1, @"expected one write event %@", tracer.allEvents);
+    NSArray *stopEvents = [tracer eventsWithType:kPOPAnimationEventDidStop];
+    XCTAssertTrue(stopEvents.count == 1, @"expected one stop event %@", tracer.allEvents);
+    
+    // assert final value
+    POPAssertColorEqual((__bridge CGColorRef)anim.toValue, layer.backgroundColor);
+}
+
+#if TARGET_OS_IPHONE
+- (void)testEdgeInsetsSupport
+{
+  const UIEdgeInsets fromEdgeInsets = UIEdgeInsetsZero;
+  const UIEdgeInsets toEdgeInsets = UIEdgeInsetsMake(100, 200, 200, 400);
+  
+  POPBasicAnimation *anim = [POPBasicAnimation animationWithPropertyNamed:kPOPScrollViewContentInset];
+  anim.fromValue = [NSValue valueWithUIEdgeInsets:fromEdgeInsets];
+  anim.toValue = [NSValue valueWithUIEdgeInsets:toEdgeInsets];
+  
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+  
+  // expect start and stop to be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+  
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+  
+  id scrollView = [OCMockObject niceMockForClass:[UIScrollView class]];
+  [scrollView pop_addAnimation:anim forKey:nil];
+  
+  // expect final value to be set
+  [[scrollView expect] setContentInset:toEdgeInsets];
+  
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+  
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  
+  // verify delegate
+  [delegate verify];
+  
+  // verify scroll view
+  [scrollView verify];
+  
+  POPAnimationValueEvent *lastEvent = [writeEvents lastObject];
+  UIEdgeInsets lastEdgeInsets = [lastEvent.value UIEdgeInsetsValue];
+  
+  // verify last insets are to insets
+  XCTAssertTrue(UIEdgeInsetsEqualToEdgeInsets(lastEdgeInsets, toEdgeInsets), @"unexpected last edge insets value: %@", lastEvent);
+}
+#endif
+
+@end

pop-tests/POPCustomAnimationTests.mm

@@ -0,0 +1,169 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <OCMock/OCMock.h>
+
+#import <XCTest/XCTest.h>
+
+#import <pop/POPCustomAnimation.h>
+
+#import "POPAnimatable.h"
+#import "POPAnimationTestsExtras.h"
+#import "POPBaseAnimationTests.h"
+
+static const CGFloat epsilon = 0.0001f;
+
+@interface POPCustomAnimationTests : POPBaseAnimationTests
+@end
+
+@implementation POPCustomAnimationTests
+
+- (void)testCallbackFinished
+{
+  static NSString * const key = @"key";
+  static CFTimeInterval const timeInterval = 0.1;
+
+  __block NSUInteger callbackCount = 0;
+  
+  // animation
+  POPCustomAnimation *anim = [POPCustomAnimation animationWithBlock:^BOOL(id target, POPCustomAnimation *animation) {
+    if (0 != callbackCount) {
+      // validate elapsed time
+      XCTAssertEqualWithAccuracy(animation.elapsedTime, timeInterval, epsilon, @"expected elapsedTime:%f %@", timeInterval, animation);
+    }
+
+    // increment callback count
+    callbackCount++;
+
+    return callbackCount < 3;
+  }];
+
+  anim.beginTime = self.beginTime;
+  
+  // delegate
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  
+  // expect start, progress & stop to all be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+  [[delegate expect] pop_animationDidApply:anim];
+  
+  anim.delegate = delegate;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+  
+  // layer
+  id layer = [OCMockObject niceMockForClass:[CALayer class]];
+  [layer pop_addAnimation:anim forKey:key];
+  
+  POPAnimatorRenderDuration(self.animator, self.beginTime + 0.1, 5, 0.1);
+  XCTAssertTrue(callbackCount == 3, @"unexpected callbackCount:%lu", (unsigned long)callbackCount);
+  
+  NSArray *startEvents = [tracer eventsWithType:kPOPAnimationEventDidStart];
+  XCTAssertTrue(1 == startEvents.count, @"unexpected startEvents count %@", startEvents);
+  
+  NSArray *stopEvents = [tracer eventsWithType:kPOPAnimationEventDidStop];
+  XCTAssertTrue(1 == stopEvents.count, @"unexpected stopEvents count %@", stopEvents);
+
+  [layer verify];
+  [delegate verify];
+}
+
+- (void)testCallbackCancelled
+{
+  static NSString * const key = @"key";
+  static CFTimeInterval const timeInterval = 0.1;
+  
+  __block NSUInteger callbackCount = 0;
+  
+  // animation
+  POPCustomAnimation *anim = [POPCustomAnimation animationWithBlock:^BOOL(id target, POPCustomAnimation *animation) {
+    if (0 == callbackCount) {
+      // validate elapsed time acruel
+      XCTAssertEqualWithAccuracy(animation.elapsedTime, 0., epsilon, @"expected elapsedTime:%f %@", timeInterval, animation);
+    } else {
+      // validate elapsed time acruel
+      XCTAssertEqualWithAccuracy(animation.elapsedTime, timeInterval, epsilon, @"expected elapsedTime:%f %@", timeInterval, animation);
+    }
+    
+    // increment callback count
+    callbackCount++;
+    
+    if (callbackCount == 3) {
+      [target pop_removeAnimationForKey:key];
+    }
+    
+    return callbackCount < 3;
+  }];
+  
+  anim.beginTime = self.beginTime;
+  
+  // delegate
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  
+  // expect start, progress & stop to all be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:NO];
+  [[delegate expect] pop_animationDidApply:anim];
+  
+  anim.delegate = delegate;
+  
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  // layer
+  id layer = [OCMockObject niceMockForClass:[CALayer class]];
+  [layer pop_addAnimation:anim forKey:key];
+  
+  POPAnimatorRenderDuration(self.animator, self.beginTime + 0.1, 5, 0.1);
+  XCTAssertTrue(callbackCount == 3, @"unexpected callbackCount:%lu", (unsigned long)callbackCount);
+
+  NSArray *startEvents = [tracer eventsWithType:kPOPAnimationEventDidStart];
+  XCTAssertTrue(1 == startEvents.count, @"unexpected startEvents count %@", startEvents);
+  
+  NSArray *stopEvents = [tracer eventsWithType:kPOPAnimationEventDidStop];
+  XCTAssertTrue(1 == stopEvents.count, @"unexpected stopEvents count %@", stopEvents);
+  
+  [layer verify];
+  [delegate verify];
+}
+
+- (void)testAssociation
+{
+  static NSString * const key = @"key";
+  
+  __block id blockTarget = nil;
+  
+  POPCustomAnimation *anim = [POPCustomAnimation animationWithBlock:^(id target, POPCustomAnimation *animation) {
+    blockTarget = target;
+    return YES;
+  }];
+
+  id layer = [OCMockObject niceMockForClass:[CALayer class]];
+
+  [layer pop_addAnimation:anim forKey:key];
+  
+  // verify animation & key
+  XCTAssertTrue(anim == [layer pop_animationForKey:key], @"expected:%@ actual:%@", anim, [layer pop_animationForKey:key]);
+  XCTAssertTrue([[layer pop_animationKeys] containsObject:key], @"expected:%@ actual:%@", key, [layer pop_animationKeys]);
+  
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1, 0.1);
+
+  XCTAssertEqualObjects(layer, blockTarget, @"expected:%@ actual:%@", layer, blockTarget);
+  
+  // remove animations
+  [layer pop_removeAnimationForKey:key];
+
+  // verify animation & key
+  XCTAssertFalse(anim == [layer pop_animationForKey:key], @"expected:%@ actual:%@", (id)nil, [layer pop_animationForKey:key]);
+  XCTAssertFalse([[layer pop_animationKeys] containsObject:key], @"expected:%@ actual:%@", (id)nil, [layer pop_animationKeys]);
+}
+
+@end

pop-tests/POPDecayAnimationTests.mm

@@ -0,0 +1,544 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <QuartzCore/QuartzCore.h>
+
+#import <OCMock/OCMock.h>
+
+#import <XCTest/XCTest.h>
+
+#import <pop/POP.h>
+#import <pop/POPAnimatorPrivate.h>
+
+#import "POPAnimatable.h"
+#import "POPAnimationTestsExtras.h"
+#import "POPBaseAnimationTests.h"
+
+@interface POPDecayAnimationTests : POPBaseAnimationTests
+@end
+
+@implementation POPDecayAnimationTests
+
+static NSString *animationKey = @"key";
+static const CGFloat epsilon = 0.0001f;
+
+- (POPDecayAnimation *)_positionAnimation
+{
+  POPDecayAnimation *anim = [POPDecayAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPosition];
+  anim.fromValue = [NSValue valueWithCGPoint:CGPointZero];
+  anim.velocity = [NSValue valueWithCGPoint:CGPointMake(7223.021, 7223.021)];
+  anim.deceleration = 0.998000;
+  return anim;
+}
+
+- (POPDecayAnimation *)_positionXAnimation
+{
+  POPDecayAnimation *anim = [POPDecayAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPositionX];
+  anim.fromValue = @0.;
+  anim.velocity = @7223.021;
+  anim.deceleration = 0.998000;
+  return anim;
+}
+
+- (POPDecayAnimation *)_positionYAnimation
+{
+  POPDecayAnimation *anim = self._positionXAnimation;
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPositionY];
+  return anim;
+}
+
+- (void)testConvergence
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  POPDecayAnimation *anim = self._positionXAnimation;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 10.0, 1.0/60.0);
+  [tracer stop];
+
+  // did reach to value
+  POPAnimationValueEvent *didReachToEvent = [[tracer eventsWithType:kPOPAnimationEventDidReachToValue] lastObject];
+  XCTAssertEqualObjects(didReachToEvent.value, anim.toValue, @"unexpected did reach to event: %@ anim:%@", didReachToEvent, anim);
+
+  // finished
+  POPAnimationValueEvent *stopEvent = [[tracer eventsWithType:kPOPAnimationEventDidStop] lastObject];
+  XCTAssertEqualObjects(stopEvent.value, @YES, @"unexpected stop event %@", stopEvent);
+
+  // all write values monotonically increasing
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  POPAnimationValueEvent *lastWriteEvent = nil;
+  for (POPAnimationValueEvent *writeEvent in writeEvents) {
+    if (lastWriteEvent) {
+      NSComparisonResult result = [lastWriteEvent.value compare:writeEvent.value];
+      XCTAssertTrue(NSOrderedAscending == result || NSOrderedSame == result, @"write event values not monotonically increasing current:%@ last:%@ all:%@", writeEvent, lastWriteEvent, writeEvents);
+    }
+    lastWriteEvent = writeEvent;
+  }
+
+  // convergence threshold
+  NSUInteger toValueFrameCount = POPAnimationCountLastEventValues(writeEvents, anim.toValue, anim.property.threshold);
+  XCTAssertTrue(toValueFrameCount <= kPOPAnimationConvergenceMaxFrameCount, @"unexpected convergence; toValueFrameCount: %lu", (unsigned long)toValueFrameCount);
+}
+
+- (void)testConvergenceNegativeVelocity
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  POPDecayAnimation *anim = self._positionXAnimation;
+  anim.velocity = @-7223.021;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 10.0, 1.0/60.0);
+  [tracer stop];
+
+  // did reach to value
+  POPAnimationValueEvent *didReachToEvent = [[tracer eventsWithType:kPOPAnimationEventDidReachToValue] lastObject];
+  XCTAssertEqualObjects(didReachToEvent.value, anim.toValue, @"unexpected did reach to event: %@ anim:%@", didReachToEvent, anim);
+
+  // finished
+  POPAnimationValueEvent *stopEvent = [[tracer eventsWithType:kPOPAnimationEventDidStop] lastObject];
+  XCTAssertEqualObjects(stopEvent.value, @YES, @"unexpected stop event %@", stopEvent);
+
+  // all write values monotonically increasing
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  POPAnimationValueEvent *lastWriteEvent = nil;
+  for (POPAnimationValueEvent *writeEvent in writeEvents) {
+    if (lastWriteEvent) {
+      NSComparisonResult result = [lastWriteEvent.value compare:writeEvent.value];
+      XCTAssertTrue(NSOrderedDescending == result || NSOrderedSame == result, @"write event values not monotonically decreasing current:%@ last:%@ all:%@", writeEvent, lastWriteEvent, writeEvents);
+    }
+    lastWriteEvent = writeEvent;
+  }
+
+  // convergence threshold
+  NSUInteger toValueFrameCount = POPAnimationCountLastEventValues(writeEvents, anim.toValue, anim.property.threshold);
+  XCTAssertTrue(toValueFrameCount <= kPOPAnimationConvergenceMaxFrameCount, @"unexpected convergence; toValueFrameCount: %lu", (unsigned long)toValueFrameCount);
+}
+
+- (void)test2DConvergence
+{
+  POPDecayAnimation *animX = self._positionXAnimation;
+  POPDecayAnimation *animY = self._positionYAnimation;
+  XCTAssertEqual(animX.duration, animY.duration, @"unexpected durations animX:%@ animY:%@", animX, animY);
+  XCTAssertEqualObjects(animX.toValue, animY.toValue, @"unexpected toValue animX:%@ animY:%@", animX, animY);
+
+  POPDecayAnimation *anim = self._positionAnimation;
+  CFTimeInterval duration = anim.duration;
+  XCTAssertEqualWithAccuracy(animX.duration, duration, epsilon, @"unexpected durations animX:%@ anim:%@", animX, anim);
+  XCTAssertEqualObjects(animX.toValue, @([anim.toValue CGPointValue].x), @"unexpected toValue animX:%@ anim:%@", animX, anim);
+
+  POPAnimatable *circle = [POPAnimatable new];
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 10.0, 1.0/60.0);
+  [tracer stop];
+
+  // did reach to value
+  POPAnimationValueEvent *didReachToEvent = [[tracer eventsWithType:kPOPAnimationEventDidReachToValue] lastObject];
+  XCTAssertEqualObjects(didReachToEvent.value, anim.toValue, @"unexpected did reach to event: %@ anim:%@", didReachToEvent, anim);
+
+  // finished
+  POPAnimationValueEvent *stopEvent = [[tracer eventsWithType:kPOPAnimationEventDidStop] lastObject];
+  XCTAssertEqualObjects(stopEvent.value, @YES, @"unexpected stop event %@", stopEvent);
+
+  // increase X velocity
+  anim.velocity = [NSValue valueWithCGPoint:CGPointMake(7223.021 + 1000, 7223.021)];
+  XCTAssertTrue(anim.duration > duration, @"unexpected duration expected:%f anim:%@", duration, anim);
+
+  // increase Y velocity
+  anim.velocity = [NSValue valueWithCGPoint:CGPointMake(7223.021, 7223.021 + 1000)];
+  XCTAssertTrue(anim.duration > duration, @"unexpected duration expected:%f anim:%@", duration, anim);
+}
+
+- (void)testRemovedOnCompletionNoStartStopBasics
+{
+  static NSString *animationKey = @"key";
+
+  CALayer *layer = self.layer1;
+  POPAnimation *anim = self._positionXAnimation;
+  POPAnimationTracer *tracer = anim.tracer;
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // cleanup
+  [layer pop_removeAllAnimations];
+
+  // configure animation
+  anim.removedOnCompletion = NO;
+  anim.delegate = delegate;
+
+  __block BOOL completionBlock = NO;
+  __block BOOL completionBlockFinished = NO;
+  anim.completionBlock = ^(POPAnimation *a, BOOL finished) {
+    completionBlock = YES;
+    completionBlockFinished = finished;
+  };
+
+  // start tracer
+  [tracer start];
+
+  // expect start and stopped
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  [layer pop_addAnimation:anim forKey:animationKey];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 20.0, 1.0/60.0);
+  NSArray *allEvents = tracer.allEvents;
+
+  // verify delegate
+  [delegate verify];
+  XCTAssertTrue(completionBlock, @"completion block did not execute %@", allEvents);
+  XCTAssertTrue(completionBlockFinished, @"completion block did not finish %@", allEvents);
+
+  // assert animation has not been removed
+  XCTAssertTrue(anim == [layer pop_animationForKey:animationKey], @"expected animation on layer animations:%@", [layer pop_animationKeys]);
+}
+
+- (void)testRemovedOnCompletionNoContinuations
+{
+  static NSString *animationKey = @"key";
+  static NSArray *velocities = @[@50.0, @100.0, @20.0, @80.0];
+  static NSArray *durations = @[@2.0, @0.5, @0.5, @2.0];
+
+  CALayer *layer = self.layer1;
+  POPDecayAnimation *anim = self._positionXAnimation;
+  POPAnimationTracer *tracer = anim.tracer;
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // cleanup
+  [layer pop_removeAllAnimations];
+
+  // configure animation
+  anim.removedOnCompletion = NO;
+  anim.delegate = delegate;
+
+  // start tracer
+  [tracer start];
+
+  __block CFTimeInterval beginTime;
+  __block BOOL completionBlock = NO;
+  __block BOOL completionBlockFinished = NO;
+
+  [velocities enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *ptrStop) {
+    anim.velocity = obj;
+
+    if (0 == idx) {
+      [tracer reset];
+
+      // starts and stops
+      [[delegate expect] pop_animationDidStart:anim];
+      [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+      anim.completionBlock = ^(POPAnimation *a, BOOL finished) {
+        completionBlock = YES;
+        completionBlockFinished = finished;
+      };
+
+      [layer pop_addAnimation:anim forKey:animationKey];
+
+      beginTime = self.beginTime;
+      CFTimeInterval dt = [durations[idx] doubleValue];
+      POPAnimatorRenderDuration(self.animator, beginTime, dt, 1.0/60.0);
+      beginTime += dt;
+
+      NSArray *allEvents = tracer.allEvents;
+      NSArray *didReachEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+
+      // verify delegate
+      [delegate verify];
+      XCTAssertTrue(1 == didReachEvents.count, @"unexpected didReachEvents %@", didReachEvents);
+      XCTAssertTrue(completionBlock, @"completion block did not execute %@", allEvents);
+      XCTAssertTrue(completionBlockFinished, @"completion block did not finish %@", allEvents);
+    } else if (velocities.count - 1 == idx) {
+      // continue stoped animation
+      [tracer reset];
+      completionBlock = NO;
+      completionBlockFinished = NO;
+      [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+      CFTimeInterval dt = [durations[idx] doubleValue];
+      POPAnimatorRenderDuration(self.animator, beginTime, dt, 1.0/60.0);
+      beginTime += dt;
+
+      NSArray *allEvents = tracer.allEvents;
+      NSArray *didReachEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+
+      // verify delegate
+      [delegate verify];
+      XCTAssertTrue(1 == didReachEvents.count, @"unexpected didReachEvents %@", didReachEvents);
+      XCTAssertTrue(completionBlock, @"completion block did not execute %@", allEvents);
+      XCTAssertTrue(completionBlockFinished, @"completion block did not finish %@", allEvents);
+    } else {
+      // continue stoped (idx = 1) or started animation
+      if (1 == idx) {
+        [[delegate expect] pop_animationDidStart:anim];
+      }
+
+      // reset state
+      [tracer reset];
+      completionBlock = NO;
+      completionBlockFinished = NO;
+
+      CFTimeInterval dt = [durations[idx] doubleValue];
+      POPAnimatorRenderDuration(self.animator, beginTime, dt, 1.0/60.0);
+      beginTime += dt;
+
+      NSArray *allEvents = tracer.allEvents;
+      NSArray *didReachEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+
+      // verify delegate
+      [delegate verify];
+      XCTAssertTrue(0 == didReachEvents.count, @"unexpected didReachEvents %@", didReachEvents);
+      XCTAssertFalse(completionBlock, @"completion block did not execute %@ %@", anim, allEvents);
+      XCTAssertFalse(completionBlockFinished, @"completion block did not finish %@ %@", anim, allEvents);
+    }
+
+    // assert animation has not been removed
+    XCTAssertTrue(anim == [layer pop_animationForKey:animationKey], @"expected animation on layer animations:%@", [layer pop_animationKeys]);
+  }];
+}
+
+- (void)testNoOperationAnimation
+{
+  const CGPoint initialValue = CGPointMake(100, 100);
+
+  CALayer *layer = self.layer1;
+  layer.position = initialValue;
+  [layer pop_removeAllAnimations];
+
+  POPDecayAnimation *anim = [POPDecayAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPosition];
+
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+
+  // starts and stops
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [layer pop_addAnimation:anim forKey:animationKey];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 5, 1.0/60.0);
+
+  // verify delegate
+  [delegate verify];
+
+  // verify number values
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  for (POPAnimationValueEvent *writeEvent in writeEvents) {
+    XCTAssertEqualObjects(writeEvent.value, [NSValue valueWithCGPoint:initialValue], @"unexpected write event:%@ anim:%@", writeEvent, anim);
+  }
+}
+
+- (void)testContinuation
+{
+  POPDecayAnimation *anim = [POPDecayAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPositionX];
+  anim.fromValue = @0.0;
+  anim.velocity = @1000.0;
+
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+  [[delegate expect] pop_animationDidStart:anim];
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  CALayer *layer = self.layer1;
+  [layer pop_addAnimation:anim forKey:animationKey];
+
+  // run animation, not till completion
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1, 1.0/60.0);
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  [tracer reset];
+
+  // verify start delegation
+  [delegate verify];
+
+  // update velocity of active animation
+  anim.velocity = @1000.0;
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  // run animation some more
+  POPAnimatorRenderDuration(self.animator, self.beginTime + 1, 4, 1.0/60.0);
+  NSArray *moreWriteEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+
+  // verify stop delegation
+  [delegate verify];
+
+  // compare event values
+  POPAnimationValueEvent *firstEvent = [writeEvents firstObject];
+  POPAnimationValueEvent *lastEvent = [writeEvents lastObject];
+  POPAnimationValueEvent *firstMoreEvent = [moreWriteEvents firstObject];
+  XCTAssertTrue(NSOrderedAscending == [firstEvent.value compare:lastEvent.value]
+               && NSOrderedAscending == [lastEvent.value compare:firstMoreEvent.value], @"write event values not monotonically increasing %@ %@ %@", firstEvent, lastEvent, firstMoreEvent);
+}
+
+- (void)testRectSupport
+{
+  const CGRect fromRect = CGRectMake(0, 0, 0, 0);
+
+  POPDecayAnimation *anim = [POPDecayAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerBounds];
+  anim.fromValue = [NSValue valueWithCGRect:fromRect];
+  anim.velocity = [NSValue valueWithCGRect:CGRectMake(100, 100, 1000, 1000)];
+  
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+
+  // expect start and stop to be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  CALayer *layer = self.layer1;
+  [layer pop_addAnimation:anim forKey:animationKey];
+
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+  
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+
+  // verify delegate
+  [delegate verify];
+
+  POPAnimationValueEvent *lastEvent = [writeEvents lastObject];
+  CGRect lastRect = [lastEvent.value CGRectValue];
+  
+  XCTAssertTrue(!CGRectEqualToRect(fromRect, lastRect), @"unexpected last rect value: %@", lastEvent);
+  XCTAssertTrue(lastRect.origin.x == lastRect.origin.y && lastRect.size.width == lastRect.size.height && lastRect.origin.x < lastRect.size.width, @"unexpected last rect value: %@", lastEvent);
+}
+
+#if TARGET_OS_IPHONE
+- (void)testEdgeInsetsSupport
+{
+  const UIEdgeInsets fromEdgeInsets = UIEdgeInsetsZero;
+  const UIEdgeInsets velocityEdgeInsets = UIEdgeInsetsMake(100, 100, 1000, 1000);
+
+  POPDecayAnimation *anim = [POPDecayAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPScrollViewContentInset];
+  anim.fromValue = [NSValue valueWithUIEdgeInsets:fromEdgeInsets];
+  anim.velocity = [NSValue valueWithUIEdgeInsets:velocityEdgeInsets];
+
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+
+  // expect start and stop to be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  id scrollView = [OCMockObject niceMockForClass:[UIScrollView class]];
+  [scrollView pop_addAnimation:anim forKey:nil];
+
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+
+  // verify delegate
+  [delegate verify];
+
+  POPAnimationValueEvent *lastEvent = [writeEvents lastObject];
+  UIEdgeInsets lastEdgeInsets = [lastEvent.value UIEdgeInsetsValue];
+
+  XCTAssertTrue(!UIEdgeInsetsEqualToEdgeInsets(fromEdgeInsets, lastEdgeInsets), @"unexpected last edge insets value: %@", lastEvent);
+  XCTAssertTrue(lastEdgeInsets.top == lastEdgeInsets.left && lastEdgeInsets.bottom == lastEdgeInsets.right && lastEdgeInsets.top < lastEdgeInsets.bottom, @"unexpected last edge insets value: %@", lastEvent);
+}
+#endif
+
+- (void)testEndValueOnReuse
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  POPDecayAnimation *anim = self._positionXAnimation;
+  
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+  
+  // read out to value
+  CGFloat toValue = [anim.toValue floatValue];
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 5.0, 1.0/60.0);
+
+  NSArray *stopEvent = [tracer eventsWithType:kPOPAnimationEventDidStop];
+  XCTAssertTrue(1 == stopEvent.count, @"unexpected events:%@", tracer.allEvents);
+
+  CGFloat lastValue = [[(POPAnimationValueEvent *)tracer.writeEvents.lastObject value] floatValue];
+  XCTAssertEqualWithAccuracy(toValue, lastValue, 0.5, @"expected:%f actual event:%@", lastValue, tracer.writeEvents.lastObject);
+  // update animation
+  anim.fromValue = @([anim.toValue floatValue] - 100);
+  anim.velocity = @(5000.);
+
+  // and reuse
+  [tracer reset];
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 5.0, 1.0/60.0);
+
+  // verify decayed passed initial toValue
+  lastValue = [[(POPAnimationValueEvent *)tracer.writeEvents.lastObject value] floatValue];
+  XCTAssertTrue(lastValue > toValue, @"unexpected last value:%f", lastValue);
+}
+
+- (void)testComputedProperties
+{
+  POPDecayAnimation *anim = [POPDecayAnimation animationWithPropertyNamed:kPOPLayerPositionX];
+  
+  // set velocity, test duration
+  anim.velocity = @(100);
+  CGFloat d1 = anim.duration;
+  XCTAssertTrue(d1 > 0, @"unexpected duration %@", anim);
+  
+  // set velocity, test duration
+  anim.velocity = @(1000);
+  CGFloat d2 = anim.duration;
+  XCTAssertTrue(d2 > d1, @"unexpected duration %@", anim);
+
+  // set from value, test to value
+  anim.fromValue = @(0);
+  CGFloat p1 = [anim.toValue floatValue];
+  XCTAssertTrue(p1 > [anim.fromValue floatValue], @"unexpected to value %@", anim);
+  
+  // set from value, test to value
+  anim.fromValue = @(10000);
+  CGFloat p2 = [anim.toValue floatValue];
+  XCTAssertTrue(p2 > [anim.fromValue floatValue] && p2 > p1, @"unexpected to value %@", anim);
+}
+
+- (void)testNSCopyingSupportPOPDecayAnimation
+{
+  POPDecayAnimation *anim = [POPDecayAnimation animationWithPropertyNamed:@"test_prop_name"];
+  
+  configureConcretePropertyAnimation(anim);
+  
+  anim.velocity = @(1.8888);
+  anim.deceleration = -9.8;
+  
+  POPDecayAnimation *copy = [anim copy];
+  
+  XCTAssertEqualObjects(copy.velocity, anim.velocity, @"expected equality; value1:%@ value2:%@", copy.velocity, anim.velocity);
+  XCTAssertEqual(copy.deceleration, anim.deceleration, @"expected equality; value1:%@ value2:%@", @(copy.deceleration), @(anim.deceleration));
+}
+
+@end

pop-tests/POPEaseInEaseOutAnimationTests.mm

@@ -0,0 +1,92 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <OCMock/OCMock.h>
+
+#import <QuartzCore/QuartzCore.h>
+
+#import <XCTest/XCTest.h>
+
+#import <pop/POP.h>
+#import <pop/POPAnimatorPrivate.h>
+
+#import "POPAnimatable.h"
+#import "POPAnimationTestsExtras.h"
+#import "POPBaseAnimationTests.h"
+
+@interface POPEaseInEaseOutAnimationTests : POPBaseAnimationTests
+@end
+
+@implementation POPEaseInEaseOutAnimationTests
+
+- (void)testCompletion
+{
+  // animation
+  // the default from, to and bounciness values are used
+  POPBasicAnimation *anim = [POPBasicAnimation easeInEaseOutAnimation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerScaleXY];
+  anim.fromValue = [NSValue valueWithCGPoint:CGPointMake(1.0, 1.0)];
+  anim.toValue = [NSValue valueWithCGPoint:CGPointMake(0.97, 0.97)];
+
+  // delegate
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // expect start, progress & stop to all be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  anim.delegate = delegate;
+
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@"key"];
+
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @0.1, @0.2, @0.4]);
+  [delegate verify];
+}
+
+- (void)testRectSupport
+{
+  const CGRect fromRect = CGRectMake(0, 0, 0, 0);
+  const CGRect toRect = CGRectMake(100, 200, 200, 400);
+
+  POPBasicAnimation *anim = [POPBasicAnimation easeInEaseOutAnimation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerBounds];
+  anim.fromValue = [NSValue valueWithCGRect:fromRect];
+  anim.toValue = [NSValue valueWithCGRect:toRect];
+  
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+  
+  // expect start and stop to be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+  
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+  
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@""];
+  
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1, 1.0/60.0);
+  
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  
+  // verify delegate
+  [delegate verify];
+  
+  POPAnimationValueEvent *lastEvent = [writeEvents lastObject];
+  CGRect lastRect = [lastEvent.value CGRectValue];
+  
+  // verify last rect is to rect
+  XCTAssertTrue(CGRectEqualToRect(lastRect, toRect), @"unexpected last rect value: %@", lastEvent);
+}
+
+@end

pop-tests/POPSpringAnimationTests.mm

@@ -0,0 +1,687 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <OCMock/OCMock.h>
+
+#import <QuartzCore/QuartzCore.h>
+
+#import <XCTest/XCTest.h>
+
+#import <pop/POPAnimation.h>
+#import <pop/POPAnimationPrivate.h>
+#import <pop/POPAnimator.h>
+#import <pop/POPAnimatorPrivate.h>
+#import <pop/POPAnimationExtras.h>
+
+#import "POPAnimatable.h"
+#import "POPAnimationInternal.h"
+#import "POPAnimationTestsExtras.h"
+#import "POPBaseAnimationTests.h"
+#import "POPCGUtils.h"
+
+@interface POPSpringAnimationTests : POPBaseAnimationTests
+@end
+
+@implementation POPSpringAnimationTests
+
+static NSString *animationKey = @"key";
+
+- (POPSpringAnimation *)_positionAnimation
+{
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.fromValue = @0.0;
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPositionX];
+  anim.springBounciness = 4.0;
+  return anim;
+}
+
+- (void)testCompletion
+{
+  // animation
+  // the default from, to and bounciness values are used
+  NSArray *markers = @[@0.5, @0.75, @1.0];
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPosition];
+  anim.progressMarkers = markers;
+  XCTAssertEqualObjects(markers, anim.progressMarkers, @"%@ shoudl equal %@", markers, anim.progressMarkers);
+
+  // delegate
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // expect start, progress & stop to all be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  anim.delegate = delegate;
+
+  // layer
+  id layer = [OCMockObject niceMockForClass:[CALayer class]];
+
+  // expect position to be called
+  CGPoint position = CGPointMake(100, 100);
+  position = [(CALayer *)[[layer stub] andReturnValue:OCMOCK_VALUE(position)] position];
+  [layer pop_addAnimation:anim forKey:@"key"];
+
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @0.1, @0.2]);
+  [layer verify];
+  [delegate verify];
+}
+
+- (void)testConvergence
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPositionX];
+  anim.fromValue = @0.0;
+  anim.toValue = @100.0;
+  anim.velocity = @100.0;
+  anim.springBounciness = 0.5;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1.0, 1.0/60.0);
+  [tracer stop];
+
+  // finished
+  POPAnimationValueEvent *stopEvent = [[tracer eventsWithType:kPOPAnimationEventDidStop] lastObject];
+  XCTAssertEqualObjects(stopEvent.value, @YES, @"unexpected stop event %@", stopEvent);
+
+  // convergence threshold
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  NSUInteger toValueFrameCount = POPAnimationCountLastEventValues(writeEvents, anim.toValue, anim.property.threshold);
+  XCTAssertTrue(toValueFrameCount < kPOPAnimationConvergenceMaxFrameCount, @"unexpected convergence; toValueFrameCount: %lu", (unsigned long)toValueFrameCount);
+}
+
+- (void)testConvergenceRounded
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPositionX];
+  anim.fromValue = @0.0;
+  anim.toValue = @100.0;
+  anim.velocity = @100.0;
+  anim.springBounciness = 0.5;
+  anim.roundingFactor = 1.0;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1.0, 1.0/60.0);
+  [tracer stop];
+
+  // finished
+  POPAnimationValueEvent *stopEvent = [[tracer eventsWithType:kPOPAnimationEventDidStop] lastObject];
+  XCTAssertEqualObjects(stopEvent.value, @YES, @"unexpected stop event %@", stopEvent);
+
+  // convergence threshold
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  NSUInteger toValueFrameCount = POPAnimationCountLastEventValues(writeEvents, anim.toValue);
+  XCTAssertTrue(toValueFrameCount < kPOPAnimationConvergenceMaxFrameCount, @"unexpected convergence; toValueFrameCount: %lu", (unsigned long)toValueFrameCount);
+}
+
+- (void)testConvergenceClampedRounded
+{
+  POPAnimatable *circle = [POPAnimatable new];
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPositionX];
+  anim.fromValue = @0.0;
+  anim.toValue = @100.0;
+  anim.velocity = @100.0;
+  anim.springBounciness = 0.5;
+  anim.roundingFactor = 1.0;
+  anim.clampMode = kPOPAnimationClampEnd;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [circle pop_addAnimation:anim forKey:@"key"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 1.0, 1.0/60.0);
+  [tracer stop];
+
+  // finished
+  POPAnimationValueEvent *stopEvent = [[tracer eventsWithType:kPOPAnimationEventDidStop] lastObject];
+  XCTAssertEqualObjects(stopEvent.value, @YES, @"unexpected stop event %@", stopEvent);
+
+  // convergence threshold
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  NSUInteger toValueFrameCount = POPAnimationCountLastEventValues(writeEvents, anim.toValue);
+  XCTAssertTrue(toValueFrameCount < kPOPAnimationConvergenceMaxFrameCount, @"unexpected convergence; toValueFrameCount: %lu", (unsigned long)toValueFrameCount);
+}
+
+- (void)testRemovedOnCompletionNoStartStopBasics
+{
+  CALayer *layer = self.layer1;
+  POPSpringAnimation *anim = self._positionAnimation;
+  POPAnimationTracer *tracer = anim.tracer;
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // cleanup
+  [layer pop_removeAllAnimations];
+
+  // configure animation
+  anim.removedOnCompletion = NO;
+  anim.toValue = @5.0;
+  anim.delegate = delegate;
+
+  __block BOOL completionBlock = NO;
+  __block BOOL completionBlockFinished = NO;
+  anim.completionBlock = ^(POPAnimation *a, BOOL finished) {
+    completionBlock = YES;
+    completionBlockFinished = finished;
+  };
+
+  // start tracer
+  [tracer start];
+
+  // expect start and stopped
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  [layer pop_addAnimation:anim forKey:animationKey];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 20.0, 1.0/60.0);
+  NSArray *allEvents = tracer.allEvents;
+
+  // verify delegate
+  [delegate verify];
+  XCTAssertTrue(completionBlock, @"completion block did not execute %@", allEvents);
+  XCTAssertTrue(completionBlockFinished, @"completion block did not finish %@", allEvents);
+
+  // assert animation has not been removed
+  XCTAssertTrue(anim == [layer pop_animationForKey:animationKey], @"expected animation on layer animations:%@", [layer pop_animationKeys]);
+}
+
+- (void)testRemovedOnCompletionNoContinuations
+{
+  static NSString *animationKey = @"key";
+  static NSArray *toValues = @[@50.0, @100.0, @20.0, @80.0];
+  static NSArray *durations = @[@2.0, @0.3, @0.4, @2.0];
+
+  CALayer *layer = self.layer1;
+  POPSpringAnimation *anim = self._positionAnimation;
+  POPAnimationTracer *tracer = anim.tracer;
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+
+  // cleanup
+  [layer pop_removeAllAnimations];
+
+  // configure animation
+  anim.removedOnCompletion = NO;
+  anim.delegate = delegate;
+
+  // start tracer
+  [tracer start];
+
+  __block CFTimeInterval beginTime;
+  __block BOOL completionBlock = NO;
+  __block BOOL completionBlockFinished = NO;
+
+  [toValues enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *ptrStop) {
+    anim.toValue = obj;
+
+    if (0 == idx) {
+      [tracer reset];
+
+      // starts and stops
+      [[delegate expect] pop_animationDidStart:anim];
+      [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+      anim.completionBlock = ^(POPAnimation *a, BOOL finished) {
+        completionBlock = YES;
+        completionBlockFinished = finished;
+      };
+
+      [layer pop_addAnimation:anim forKey:animationKey];
+
+      beginTime = self.beginTime;
+      CFTimeInterval dt = [durations[idx] doubleValue];
+      POPAnimatorRenderDuration(self.animator, beginTime, dt, 1.0/60.0);
+      beginTime += dt;
+
+      NSArray *allEvents = tracer.allEvents;
+      NSArray *didReachEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+
+      // verify delegate
+      [delegate verify];
+      XCTAssertTrue(1 == didReachEvents.count, @"unexpected didReachEvents %@", didReachEvents);
+      XCTAssertTrue(completionBlock, @"completion block did not execute %@", allEvents);
+      XCTAssertTrue(completionBlockFinished, @"completion block did not finish %@", allEvents);
+    } else if (toValues.count - 1 == idx) {
+      // continue stoped animation
+      [tracer reset];
+      completionBlock = NO;
+      completionBlockFinished = NO;
+      [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+      CFTimeInterval dt = [durations[idx] doubleValue];
+      POPAnimatorRenderDuration(self.animator, beginTime, dt, 1.0/60.0);
+      beginTime += dt;
+
+      NSArray *allEvents = tracer.allEvents;
+      NSArray *didReachEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+
+      // verify delegate
+      [delegate verify];
+      XCTAssertTrue(1 == didReachEvents.count, @"unexpected didReachEvents %@", didReachEvents);
+      XCTAssertTrue(completionBlock, @"completion block did not execute %@", allEvents);
+      XCTAssertTrue(completionBlockFinished, @"completion block did not finish %@", allEvents);
+    } else {
+      // continue stoped (idx = 1) or started animation
+      if (1 == idx) {
+        [[delegate expect] pop_animationDidStart:anim];
+      }
+
+      // reset state
+      [tracer reset];
+      completionBlock = NO;
+      completionBlockFinished = NO;
+
+      CFTimeInterval dt = [durations[idx] doubleValue];
+      POPAnimatorRenderDuration(self.animator, beginTime, dt, 1.0/60.0);
+      beginTime += dt;
+
+      NSArray *allEvents = tracer.allEvents;
+      NSArray *didReachEvents = [tracer eventsWithType:kPOPAnimationEventDidReachToValue];
+
+      // verify delegate
+      [delegate verify];
+      XCTAssertTrue(1 == didReachEvents.count, @"unexpected didReachEvents %@", didReachEvents);
+      XCTAssertFalse(completionBlock, @"completion block did not execute %@ %@", anim, allEvents);
+      XCTAssertFalse(completionBlockFinished, @"completion block did not finish %@ %@", anim, allEvents);
+    }
+
+    // assert animation has not been removed
+    XCTAssertTrue(anim == [layer pop_animationForKey:animationKey], @"expected animation on layer animations:%@", [layer pop_animationKeys]);
+  }];
+}
+
+- (void)testNoOperationAnimation
+{
+  const CGPoint initialValue = CGPointMake(100, 100);
+
+  CALayer *layer = self.layer1;
+  layer.position = initialValue;
+  [layer pop_removeAllAnimations];
+
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPosition];
+
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+
+  // starts and stops
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  [layer pop_addAnimation:anim forKey:animationKey];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 5, 1.0/60.0);
+
+  // verify delegate
+  [delegate verify];
+
+  // verify number values
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  for (POPAnimationValueEvent *writeEvent in writeEvents) {
+    XCTAssertEqualObjects(writeEvent.value, [NSValue valueWithCGPoint:initialValue], @"unexpected write event:%@ anim:%@", writeEvent, anim);
+  }
+}
+
+- (void)testLazyValueInitialization
+{
+  CALayer *layer = self.layer1;
+  layer.position = CGPointZero;
+
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerPositionX];
+  anim.fromValue = @100.0;
+  anim.beginTime = self.beginTime + 0.3;
+
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  // add animation, but do not start
+  [layer pop_addAnimation:anim forKey:animationKey];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 0.2, 1.0/60.0);
+  XCTAssertNotNil(anim.fromValue, @"unexpected from value %@", anim);
+  XCTAssertNil(anim.toValue, @"unexpected to value %@", anim);
+
+  // start animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime + 0.2, 0.2, 1.0/60.0);
+  XCTAssertNotNil(anim.fromValue, @"unexpected from value %@", anim);
+  XCTAssertNotNil(anim.toValue, @"unexpected to value %@", anim);
+
+  // continue running animation
+  anim.fromValue = nil;
+  anim.toValue = @200.0;
+  POPAnimatorRenderDuration(self.animator, self.beginTime + 0.4, 0.2, 1.0/60.0);
+  XCTAssertNotNil(anim.fromValue, @"unexpected from value %@", anim);
+  XCTAssertNotNil(anim.toValue, @"unexpected to value %@", anim);
+}
+
+- (void)testLatentSpring
+{
+  POPSpringAnimation *translationAnimation = [POPSpringAnimation animation];
+  translationAnimation.dynamicsTension = 990;
+  translationAnimation.dynamicsFriction = 230;
+  translationAnimation.dynamicsMass = 1.0;
+  translationAnimation.property = [POPAnimatableProperty propertyWithName:kPOPLayerOpacity];
+  translationAnimation.removedOnCompletion = NO;
+  [self pop_addAnimation:translationAnimation forKey:@"test"];
+  POPAnimatorRenderDuration(self.animator, self.beginTime + 0.4, 0.2, 1.0/60.0);
+}
+
+- (void)testRectSupport
+{
+  const CGRect fromRect = CGRectMake(0, 0, 0, 0);
+  const CGRect toRect = CGRectMake(100, 200, 200, 400);
+  const CGRect velocityRect = CGRectMake(1000, 1000, 1000, 1000);
+
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerBounds];
+  anim.fromValue = [NSValue valueWithCGRect:fromRect];
+  anim.toValue = [NSValue valueWithCGRect:toRect];
+  anim.velocity = [NSValue valueWithCGRect:velocityRect];
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+
+  // expect start and stop to be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@""];
+
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+
+  // verify delegate
+  [delegate verify];
+
+  POPAnimationValueEvent *lastEvent = [writeEvents lastObject];
+  CGRect lastRect = [lastEvent.value CGRectValue];
+
+  // verify last rect is to rect
+  XCTAssertTrue(CGRectEqualToRect(lastRect, toRect), @"unexpected last rect value: %@", lastEvent);
+}
+
+#if TARGET_OS_IPHONE
+- (void)testEdgeInsetsSupport
+{
+  const UIEdgeInsets fromEdgeInsets = UIEdgeInsetsZero;
+  const UIEdgeInsets toEdgeInsets = UIEdgeInsetsMake(100, 200, 200, 400);
+  const UIEdgeInsets velocityEdgeInsets = UIEdgeInsetsMake(1000, 1000, 1000, 1000);
+
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPScrollViewContentInset];
+  anim.fromValue = [NSValue valueWithUIEdgeInsets:fromEdgeInsets];
+  anim.toValue = [NSValue valueWithUIEdgeInsets:toEdgeInsets];
+  anim.velocity = [NSValue valueWithUIEdgeInsets:velocityEdgeInsets];
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+
+  // expect start and stop to be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  id scrollView = [OCMockObject niceMockForClass:[UIScrollView class]];
+  [scrollView pop_addAnimation:anim forKey:nil];
+
+  // expect final value to be set
+  [[scrollView expect] setContentInset:toEdgeInsets];
+
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+
+  // verify delegate
+  [delegate verify];
+
+  // verify scroll view
+  [scrollView verify];
+
+  POPAnimationValueEvent *lastEvent = [writeEvents lastObject];
+  UIEdgeInsets lastEdgeInsets = [lastEvent.value UIEdgeInsetsValue];
+
+  // verify last insets are to insets
+  XCTAssertTrue(UIEdgeInsetsEqualToEdgeInsets(lastEdgeInsets, toEdgeInsets), @"unexpected last edge insets value: %@", lastEvent);
+}
+#endif
+
+- (void)testColorSupport
+{
+  CGFloat fromValues[4] = {1, 1, 1, 1};
+  CGFloat toValues[4] = {0, 0, 0, 1};
+  CGColorRef fromColor = POPCGColorRGBACreate(fromValues);
+  CGColorRef toColor = POPCGColorRGBACreate(toValues);
+
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerBounds];
+  anim.fromValue = (__bridge_transfer id)fromColor;
+  anim.toValue = (__bridge_transfer id)toColor;
+
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@""];
+
+  // run animation
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+
+  // verify delegate
+  [delegate verify];
+
+  // expect some interpolation
+  XCTAssertTrue(writeEvents.count > 1, @"unexpected write events %@", writeEvents);
+  POPAnimationValueEvent *lastEvent = [writeEvents lastObject];
+
+  // verify last written color is to color
+  POPAssertColorEqual((__bridge CGColorRef)lastEvent.value, (__bridge CGColorRef)anim.toValue);
+}
+
+static BOOL _floatingPointEqual(CGFloat a, CGFloat b)
+{
+  CGFloat epsilon = 0.0001;
+  return std::abs(a - b) < epsilon;
+}
+
+- (void)testBouncinessSpeedToTensionFrictionConversion
+{
+  CGFloat sampleBounciness = 12.0;
+  CGFloat sampleSpeed = 5.0;
+
+  CGFloat tension, friction, mass;
+  [POPSpringAnimation convertBounciness:sampleBounciness speed:sampleSpeed toTension:&tension friction:&friction mass:&mass];
+
+  CGFloat outBounciness, outSpeed;
+  [POPSpringAnimation convertTension:tension friction:friction toBounciness:&outBounciness speed:&outSpeed];
+
+  XCTAssertTrue(_floatingPointEqual(sampleBounciness, outBounciness) && _floatingPointEqual(sampleSpeed, outSpeed), @"(bounciness, speed) conversion failed. Mapped (%f, %f) back to (%f, %f)", sampleBounciness, sampleSpeed, outBounciness, outSpeed);
+}
+
+- (void)testTensionFrictionToBouncinessSpeedConversion
+{
+  CGFloat sampleTension = 240.0;
+  CGFloat sampleFriction = 25.0;
+
+  CGFloat bounciness, speed;
+  [POPSpringAnimation convertTension:sampleTension friction:sampleFriction toBounciness:&bounciness speed:&speed];
+
+  CGFloat outTension, outFriction, outMass;
+  [POPSpringAnimation convertBounciness:bounciness speed:speed toTension:&outTension friction:&outFriction mass:&outMass];
+
+  XCTAssertTrue(_floatingPointEqual(sampleTension, outTension) && _floatingPointEqual(sampleFriction, outFriction), @"(tension, friction) conversion failed. Mapped (%f, %f) back to (%f, %f)", sampleTension, sampleFriction, outTension, outFriction);
+}
+
+- (void)testRemovedOnCompletionNoContinuationValues
+{
+  static CGFloat fromValue = 400.0;
+  static NSArray *toValues = @[@200.0, @400.0];
+
+  // configure animation
+  POPSpringAnimation *anim = self._positionAnimation;
+  anim.fromValue = [NSNumber numberWithFloat:fromValue];
+  anim.toValue = toValues[0];
+  anim.removedOnCompletion = NO;
+
+  // run animation, from 400 to 200
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@""];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  // assert reached to value
+  XCTAssertTrue(layer.position.x == [anim.toValue floatValue], @"unexpected value:%@ %@", layer, anim);
+
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  // update to value, animate from 200 to 400
+  anim.toValue = toValues[1];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  // verify from 200 to 400
+  NSArray *writeEvents = [tracer eventsWithType:kPOPAnimationEventPropertyWrite];
+  XCTAssertTrue(writeEvents.count > 5, @"unexpected frame count %@", writeEvents);
+
+  CGFloat firstValue = [[(POPAnimationValueEvent *)[writeEvents firstObject] value] floatValue];
+  CGFloat lastValue = [[(POPAnimationValueEvent *)[writeEvents lastObject] value] floatValue];
+  XCTAssertEqualWithAccuracy(((CGFloat)[toValues[0] floatValue]), firstValue, 10, @"unexpected first value %@", writeEvents);
+  XCTAssertEqualWithAccuracy(((CGFloat)[toValues[1] floatValue]), lastValue, 10, @"unexpected last value %@", writeEvents);
+}
+
+- (void)testNilColor
+{
+  POPSpringAnimation *anim = [POPSpringAnimation animation];
+  anim.property = [POPAnimatableProperty propertyWithName:kPOPLayerBackgroundColor];
+
+#if TARGET_OS_IPHONE
+  anim.toValue = (__bridge id)[UIColor redColor].CGColor;
+#else
+  anim.toValue = (__bridge id)[NSColor redColor].CGColor;
+#endif
+  
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  // run animation
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@""];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  // verify valid from color exists
+  CGColorRef fromColor = (__bridge CGColorRef)anim.fromValue;
+  XCTAssertTrue(fromColor, @"unexpected value %p", fromColor);
+
+  // verify from color clear
+#if TARGET_OS_IPHONE
+  POPAssertColorEqual(fromColor, [UIColor clearColor].CGColor);
+#else
+  POPAssertColorEqual(fromColor, [NSColor clearColor].CGColor);
+#endif
+}
+
+- (void)testExcessiveJumpInTime
+{
+  POPSpringAnimation *anim = self._positionAnimation;
+  anim.toValue = @(1000.0);
+
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  id delegate = [OCMockObject niceMockForProtocol:@protocol(POPAnimationDelegate)];
+  anim.delegate = delegate;
+  
+  // expect start and stop to be called
+  [[delegate expect] pop_animationDidStart:anim];
+  [[delegate expect] pop_animationDidStop:anim finished:YES];
+
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:animationKey];
+
+  // render with large time jump
+  POPAnimatorRenderTimes(self.animator, self.beginTime, @[@0.0, @0.01, @300]);
+
+  // verify start stop
+  [delegate verify];
+
+  // verify last write event value
+  POPAnimationValueEvent *writeEvent = [[tracer eventsWithType:kPOPAnimationEventPropertyWrite] lastObject];
+  XCTAssertEqualObjects(writeEvent.value, anim.toValue, @"unexpected last write event %@", writeEvent);
+}
+
+- (void)testEquivalentFromToValues
+{
+  POPSpringAnimation *anim = [POPSpringAnimation animationWithPropertyNamed:kPOPLayerPosition];
+  anim.fromValue = [NSValue valueWithCGPoint:CGPointZero];
+  anim.toValue = [NSValue valueWithCGPoint:CGPointZero];
+  anim.velocity = [NSValue valueWithCGPoint:CGPointMake(1000.0, 1000.0)];
+
+  // start tracer
+  POPAnimationTracer *tracer = anim.tracer;
+  [tracer start];
+
+  // run animation
+  CALayer *layer = [CALayer layer];
+  [layer pop_addAnimation:anim forKey:@""];
+  POPAnimatorRenderDuration(self.animator, self.beginTime, 3, 1.0/60.0);
+
+  // verify last write event value
+  POPAnimationValueEvent *writeEvent = [[tracer eventsWithType:kPOPAnimationEventPropertyWrite] lastObject];
+  XCTAssertEqualObjects(writeEvent.value, anim.toValue, @"unexpected last write event %@", writeEvent);
+}
+
+- (void)testNSCopyingSupportPOPSpringAnimation
+{
+  POPSpringAnimation *anim = [POPSpringAnimation animationWithPropertyNamed:@"asdf_asdf_asdf"];
+  
+  configureConcretePropertyAnimation(anim);
+  
+  anim.velocity = @(4321);
+  anim.springBounciness = 11.1;
+  anim.springSpeed = 12;
+  anim.dynamicsTension = 0.83;
+  anim.dynamicsFriction = 0.97;
+  anim.dynamicsMass = 100;
+  
+  POPSpringAnimation *copy = [anim copy];
+  
+  XCTAssertEqualObjects(copy.velocity, anim.velocity, @"expected equality; value1:%@ value2:%@", copy.velocity, anim.velocity);
+  XCTAssertEqual(copy.springBounciness, anim.springBounciness, @"expected equality; value1:%@ value2:%@", @(copy.springBounciness), @(anim.springBounciness));
+  XCTAssertEqual(copy.springSpeed, anim.springSpeed, @"expected equality; value1:%@ value2:%@", @(copy.springSpeed), @(anim.springSpeed));
+  XCTAssertEqual(copy.dynamicsTension, anim.dynamicsTension, @"expected equality; value1:%@ value2:%@", @(copy.dynamicsTension), @(anim.dynamicsTension));
+  XCTAssertEqual(copy.dynamicsFriction, anim.dynamicsFriction, @"expected equality; value1:%@ value2:%@", @(copy.dynamicsFriction), @(anim.dynamicsFriction));
+  XCTAssertEqual(copy.dynamicsMass, anim.dynamicsMass, @"expected equality; value1:%@ value2:%@", @(copy.dynamicsMass), @(anim.dynamicsMass));
+}
+
+@end

pop-tests/pop-tests-ios-Info.plist

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleExecutable</key>
+	<string>${EXECUTABLE_NAME}</string>
+	<key>CFBundleIdentifier</key>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundlePackageType</key>
+	<string>BNDL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+</dict>
+</plist>

pop-tests/pop-tests-osx-Info.plist

@@ -0,0 +1,22 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleExecutable</key>
+	<string>${EXECUTABLE_NAME}</string>
+	<key>CFBundleIdentifier</key>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundlePackageType</key>
+	<string>BNDL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+</dict>
+</plist>

pop-tests/pop-tests-tvos-Info.plist

@@ -0,0 +1,24 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>CFBundleDevelopmentRegion</key>
+	<string>en</string>
+	<key>CFBundleExecutable</key>
+	<string>$(EXECUTABLE_NAME)</string>
+	<key>CFBundleIdentifier</key>
+	<string>$(PRODUCT_BUNDLE_IDENTIFIER)</string>
+	<key>CFBundleInfoDictionaryVersion</key>
+	<string>6.0</string>
+	<key>CFBundleName</key>
+	<string>$(PRODUCT_NAME)</string>
+	<key>CFBundlePackageType</key>
+	<string>BNDL</string>
+	<key>CFBundleShortVersionString</key>
+	<string>1.0</string>
+	<key>CFBundleSignature</key>
+	<string>????</string>
+	<key>CFBundleVersion</key>
+	<string>1</string>
+</dict>
+</plist>

pop.podspec

@@ -0,0 +1,21 @@
+Pod::Spec.new do |spec|
+  spec.name         = 'pop'
+  spec.version      = '1.0.11'
+  spec.license      =  { :type => 'BSD' }
+  spec.homepage     = 'https://github.com/facebook/pop'
+  spec.authors      = { 'Kimon Tsinteris' => 'kimon@mac.com' }
+  spec.summary      = 'Extensible animation framework for iOS and OS X.'
+  spec.source       = { :git => 'https://github.com/facebook/pop.git', :tag => '1.0.10' }
+  spec.source_files = 'pop/**/*.{h,m,mm,cpp}'
+  spec.public_header_files = 'pop/{POP,POPAnimatableProperty,POPAnimatablePropertyTypes,POPAnimation,POPAnimationEvent,POPAnimationExtras,POPAnimationTracer,POPAnimator,POPBasicAnimation,POPCustomAnimation,POPDecayAnimation,POPDefines,POPGeometry,POPLayerExtras,POPPropertyAnimation,POPSpringAnimation,POPVector}.h'
+  spec.requires_arc = true
+  spec.social_media_url = 'https://twitter.com/fbOpenSource'
+  spec.library = 'c++'
+  spec.pod_target_xcconfig = {
+       'CLANG_CXX_LANGUAGE_STANDARD' => 'c++11',
+       'CLANG_CXX_LIBRARY' => 'libc++'
+  }
+  spec.ios.deployment_target = '8.0'
+  spec.osx.deployment_target = '10.8'
+  spec.tvos.deployment_target = '9.0'
+end

pop.xcodeproj/project.pbxproj

@@ -0,0 +1,1948 @@
+// !$*UTF8*$!
+{
+	archiveVersion = 1;
+	classes = {
+	};
+	objectVersion = 46;
+	objects = {
+
+/* Begin PBXBuildFile section */
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pop.xcodeproj/project.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,7 @@
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pop.xcworkspace/contents.xcworkspacedata

@@ -0,0 +1,10 @@
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+   </FileRef>
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+   </FileRef>
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pop.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>

pop/POP.h

@@ -0,0 +1,30 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#ifndef POP_POP_H
+#define POP_POP_H
+
+#import <pop/POPDefines.h>
+
+#import <pop/POPAnimatableProperty.h>
+#import <pop/POPAnimatablePropertyTypes.h>
+#import <pop/POPAnimation.h>
+#import <pop/POPAnimationEvent.h>
+#import <pop/POPAnimationExtras.h>
+#import <pop/POPAnimationTracer.h>
+#import <pop/POPAnimator.h>
+#import <pop/POPBasicAnimation.h>
+#import <pop/POPCustomAnimation.h>
+#import <pop/POPDecayAnimation.h>
+#import <pop/POPGeometry.h>
+#import <pop/POPLayerExtras.h>
+#import <pop/POPPropertyAnimation.h>
+#import <pop/POPSpringAnimation.h>
+
+#endif /* POP_POP_H */

pop/POPAction.h

@@ -0,0 +1,67 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#ifndef POPACTION_H
+#define POPACTION_H
+
+#import <QuartzCore/CATransaction.h>
+
+#import <pop/POPDefines.h>
+
+#ifdef __cplusplus
+
+namespace POP {
+  
+  /**
+   @abstract Disables Core Animation actions using RAII.
+   @discussion The disablement of actions is scoped to the current transaction.
+   */
+  class ActionDisabler
+  {
+    BOOL state;
+    
+  public:
+    ActionDisabler() POP_NOTHROW
+    {
+      state = [CATransaction disableActions];
+      [CATransaction setDisableActions:YES];
+    }
+    
+    ~ActionDisabler()
+    {
+      [CATransaction setDisableActions:state];
+    }
+  };
+  
+  /**
+   @abstract Enables Core Animation actions using RAII.
+   @discussion The enablement of actions is scoped to the current transaction.
+   */
+  class ActionEnabler
+  {
+    BOOL state;
+    
+  public:
+    ActionEnabler() POP_NOTHROW
+    {
+      state = [CATransaction disableActions];
+      [CATransaction setDisableActions:NO];
+    }
+    
+    ~ActionEnabler()
+    {
+      [CATransaction setDisableActions:state];
+    }
+  };
+
+}
+
+#endif /* __cplusplus */
+
+#endif /* POPACTION_H */

pop/POPAnimatableProperty.h

@@ -0,0 +1,256 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <CoreGraphics/CoreGraphics.h>
+
+#import <Foundation/NSObject.h>
+
+#import <pop/POPDefines.h>
+#import <pop/POPAnimatablePropertyTypes.h>
+
+@class POPMutableAnimatableProperty;
+
+/**
+ @abstract Describes an animatable property.
+ */
+@interface POPAnimatableProperty : NSObject <NSCopying, NSMutableCopying>
+
+/**
+ @abstract Property accessor.
+ @param name The name of the property.
+ @return The animatable property with that name or nil if it does not exist.
+ @discussion Common animatable properties are included by default. Use the provided constants to reference.
+ */
++ (id)propertyWithName:(NSString *)name;
+
+/**
+ @abstract The designated initializer.
+ @param name The name of the property.
+ @param block The block used to configure the property on creation.
+ @return The animatable property with name if it exists, otherwise a newly created instance configured by block.
+ @discussion Custom properties should use reverse-DNS naming. A newly created instance is only mutable in the scope of block. Once constructed, a property becomes immutable.
+ */
++ (id)propertyWithName:(NSString *)name initializer:(void (^)(POPMutableAnimatableProperty *prop))block;
+
+/**
+ @abstract The name of the property.
+ @discussion Used to uniquely identify an animatable property.
+ */
+@property (readonly, nonatomic, copy) NSString *name;
+
+/**
+ @abstract Block used to read values from a property into an array of floats.
+ */
+@property (readonly, nonatomic, copy) POPAnimatablePropertyReadBlock readBlock;
+
+/**
+ @abstract Block used to write values from an array of floats into a property.
+ */
+@property (readonly, nonatomic, copy) POPAnimatablePropertyWriteBlock writeBlock;
+
+/**
+ @abstract The threshold value used when determining completion of dynamics simulations.
+ */
+@property (readonly, nonatomic, assign) CGFloat threshold;
+
+@end
+
+/**
+ @abstract A mutable animatable property intended for configuration.
+ */
+@interface POPMutableAnimatableProperty : POPAnimatableProperty
+
+/**
+ @abstract A read-write version of POPAnimatableProperty name property.
+ */
+@property (readwrite, nonatomic, copy) NSString *name;
+
+/**
+ @abstract A read-write version of POPAnimatableProperty readBlock property.
+ */
+@property (readwrite, nonatomic, copy) POPAnimatablePropertyReadBlock readBlock;
+
+/**
+ @abstract A read-write version of POPAnimatableProperty writeBlock property.
+ */
+@property (readwrite, nonatomic, copy) POPAnimatablePropertyWriteBlock writeBlock;
+
+/**
+ @abstract A read-write version of POPAnimatableProperty threshold property.
+ */
+@property (readwrite, nonatomic, assign) CGFloat threshold;
+
+@end
+
+POP_EXTERN_C_BEGIN
+
+/**
+ Common CALayer property names.
+ */
+extern NSString * const kPOPLayerBackgroundColor;
+extern NSString * const kPOPLayerBounds;
+extern NSString * const kPOPLayerCornerRadius;
+extern NSString * const kPOPLayerBorderWidth;
+extern NSString * const kPOPLayerBorderColor;
+extern NSString * const kPOPLayerOpacity;
+extern NSString * const kPOPLayerPosition;
+extern NSString * const kPOPLayerPositionX;
+extern NSString * const kPOPLayerPositionY;
+extern NSString * const kPOPLayerRotation;
+extern NSString * const kPOPLayerRotationX;
+extern NSString * const kPOPLayerRotationY;
+extern NSString * const kPOPLayerScaleX;
+extern NSString * const kPOPLayerScaleXY;
+extern NSString * const kPOPLayerScaleY;
+extern NSString * const kPOPLayerSize;
+extern NSString * const kPOPLayerSubscaleXY;
+extern NSString * const kPOPLayerSubtranslationX;
+extern NSString * const kPOPLayerSubtranslationXY;
+extern NSString * const kPOPLayerSubtranslationY;
+extern NSString * const kPOPLayerSubtranslationZ;
+extern NSString * const kPOPLayerTranslationX;
+extern NSString * const kPOPLayerTranslationXY;
+extern NSString * const kPOPLayerTranslationY;
+extern NSString * const kPOPLayerTranslationZ;
+extern NSString * const kPOPLayerZPosition;
+extern NSString * const kPOPLayerShadowColor;
+extern NSString * const kPOPLayerShadowOffset;
+extern NSString * const kPOPLayerShadowOpacity;
+extern NSString * const kPOPLayerShadowRadius;
+
+/**
+ Common CAShapeLayer property names.
+ */
+extern NSString * const kPOPShapeLayerStrokeStart;
+extern NSString * const kPOPShapeLayerStrokeEnd;
+extern NSString * const kPOPShapeLayerStrokeColor;
+extern NSString * const kPOPShapeLayerFillColor;
+extern NSString * const kPOPShapeLayerLineWidth;
+extern NSString * const kPOPShapeLayerLineDashPhase;
+
+/**
+ Common NSLayoutConstraint property names.
+ */
+extern NSString * const kPOPLayoutConstraintConstant;
+
+
+#if TARGET_OS_IPHONE
+
+/**
+ Common UIView property names.
+ */
+extern NSString * const kPOPViewAlpha;
+extern NSString * const kPOPViewBackgroundColor;
+extern NSString * const kPOPViewBounds;
+extern NSString * const kPOPViewCenter;
+extern NSString * const kPOPViewFrame;
+extern NSString * const kPOPViewScaleX;
+extern NSString * const kPOPViewScaleXY;
+extern NSString * const kPOPViewScaleY;
+extern NSString * const kPOPViewSize;
+extern NSString * const kPOPViewTintColor;
+
+/**
+ Common UIScrollView property names.
+ */
+extern NSString * const kPOPScrollViewContentOffset;
+extern NSString * const kPOPScrollViewContentSize;
+extern NSString * const kPOPScrollViewZoomScale;
+extern NSString * const kPOPScrollViewContentInset;
+extern NSString * const kPOPScrollViewScrollIndicatorInsets;
+
+/**
+ Common UITableView property names.
+ */
+extern NSString * const kPOPTableViewContentOffset;
+extern NSString * const kPOPTableViewContentSize;
+
+/**
+ Common UICollectionView property names.
+ */
+extern NSString * const kPOPCollectionViewContentOffset;
+extern NSString * const kPOPCollectionViewContentSize;
+
+/**
+ Common UINavigationBar property names.
+ */
+extern NSString * const kPOPNavigationBarBarTintColor;
+
+/**
+ Common UIToolbar property names.
+ */
+extern NSString * const kPOPToolbarBarTintColor;
+
+/**
+ Common UITabBar property names.
+ */
+extern NSString * const kPOPTabBarBarTintColor;
+
+/**
+ Common UILabel property names.
+ */
+extern NSString * const kPOPLabelTextColor;
+
+#else
+
+/**
+ Common NSView property names.
+ */
+extern NSString * const kPOPViewFrame;
+extern NSString * const kPOPViewBounds;
+extern NSString * const kPOPViewAlphaValue;
+extern NSString * const kPOPViewFrameRotation;
+extern NSString * const kPOPViewFrameCenterRotation;
+extern NSString * const kPOPViewBoundsRotation;
+
+/**
+ Common NSWindow property names.
+ */
+extern NSString * const kPOPWindowFrame;
+extern NSString * const kPOPWindowAlphaValue;
+extern NSString * const kPOPWindowBackgroundColor;
+
+#endif
+
+#if SCENEKIT_SDK_AVAILABLE
+
+/**
+ Common SceneKit property names.
+ */
+extern NSString * const kPOPSCNNodePosition;
+extern NSString * const kPOPSCNNodePositionX;
+extern NSString * const kPOPSCNNodePositionY;
+extern NSString * const kPOPSCNNodePositionZ;
+extern NSString * const kPOPSCNNodeTranslation;
+extern NSString * const kPOPSCNNodeTranslationX;
+extern NSString * const kPOPSCNNodeTranslationY;
+extern NSString * const kPOPSCNNodeTranslationZ;
+extern NSString * const kPOPSCNNodeRotation;
+extern NSString * const kPOPSCNNodeRotationX;
+extern NSString * const kPOPSCNNodeRotationY;
+extern NSString * const kPOPSCNNodeRotationZ;
+extern NSString * const kPOPSCNNodeRotationW;
+extern NSString * const kPOPSCNNodeEulerAngles;
+extern NSString * const kPOPSCNNodeEulerAnglesX;
+extern NSString * const kPOPSCNNodeEulerAnglesY;
+extern NSString * const kPOPSCNNodeEulerAnglesZ;
+extern NSString * const kPOPSCNNodeOrientation;
+extern NSString * const kPOPSCNNodeOrientationX;
+extern NSString * const kPOPSCNNodeOrientationY;
+extern NSString * const kPOPSCNNodeOrientationZ;
+extern NSString * const kPOPSCNNodeOrientationW;
+extern NSString * const kPOPSCNNodeScale;
+extern NSString * const kPOPSCNNodeScaleX;
+extern NSString * const kPOPSCNNodeScaleY;
+extern NSString * const kPOPSCNNodeScaleZ;
+extern NSString * const kPOPSCNNodeScaleXY;
+
+#endif
+
+POP_EXTERN_C_END

pop/POPAnimatableProperty.mm

@@ -0,0 +1,1310 @@
+/**
+  Copyright (c) 2014-present, Facebook, Inc.
+  All rights reserved.
+
+  This source code is licensed under the BSD-style license found in the
+  LICENSE file in the root directory of this source tree. An additional grant
+  of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimatableProperty.h"
+
+#import <QuartzCore/QuartzCore.h>
+
+#import "POPAnimationRuntime.h"
+#import "POPCGUtils.h"
+#import "POPDefines.h"
+#import "POPLayerExtras.h"
+
+// common threshold definitions
+static CGFloat const kPOPThresholdColor = 0.01;
+static CGFloat const kPOPThresholdPoint = 1.0;
+static CGFloat const kPOPThresholdOpacity = 0.01;
+static CGFloat const kPOPThresholdScale = 0.005;
+static CGFloat const kPOPThresholdRotation = 0.01;
+static CGFloat const kPOPThresholdRadius = 0.01;
+
+#pragma mark - Static
+
+// CALayer
+NSString * const kPOPLayerBackgroundColor = @"backgroundColor";
+NSString * const kPOPLayerBounds = @"bounds";
+NSString * const kPOPLayerCornerRadius = @"cornerRadius";
+NSString * const kPOPLayerBorderWidth = @"borderWidth";
+NSString * const kPOPLayerBorderColor = @"borderColor";
+NSString * const kPOPLayerOpacity = @"opacity";
+NSString * const kPOPLayerPosition = @"position";
+NSString * const kPOPLayerPositionX = @"positionX";
+NSString * const kPOPLayerPositionY = @"positionY";
+NSString * const kPOPLayerRotation = @"rotation";
+NSString * const kPOPLayerRotationX = @"rotationX";
+NSString * const kPOPLayerRotationY = @"rotationY";
+NSString * const kPOPLayerScaleX = @"scaleX";
+NSString * const kPOPLayerScaleXY = @"scaleXY";
+NSString * const kPOPLayerScaleY = @"scaleY";
+NSString * const kPOPLayerSize = @"size";
+NSString * const kPOPLayerSubscaleXY = @"subscaleXY";
+NSString * const kPOPLayerSubtranslationX = @"subtranslationX";
+NSString * const kPOPLayerSubtranslationXY = @"subtranslationXY";
+NSString * const kPOPLayerSubtranslationY = @"subtranslationY";
+NSString * const kPOPLayerSubtranslationZ = @"subtranslationZ";
+NSString * const kPOPLayerTranslationX = @"translationX";
+NSString * const kPOPLayerTranslationXY = @"translationXY";
+NSString * const kPOPLayerTranslationY = @"translationY";
+NSString * const kPOPLayerTranslationZ = @"translationZ";
+NSString * const kPOPLayerZPosition = @"zPosition";
+NSString * const kPOPLayerShadowColor = @"shadowColor";
+NSString * const kPOPLayerShadowOffset = @"shadowOffset";
+NSString * const kPOPLayerShadowOpacity = @"shadowOpacity";
+NSString * const kPOPLayerShadowRadius = @"shadowRadius";
+
+// CAShapeLayer
+NSString * const kPOPShapeLayerStrokeStart = @"shapeLayer.strokeStart";
+NSString * const kPOPShapeLayerStrokeEnd = @"shapeLayer.strokeEnd";
+NSString * const kPOPShapeLayerStrokeColor = @"shapeLayer.strokeColor";
+NSString * const kPOPShapeLayerFillColor = @"shapeLayer.fillColor";
+NSString * const kPOPShapeLayerLineWidth = @"shapeLayer.lineWidth";
+NSString * const kPOPShapeLayerLineDashPhase = @"shapeLayer.lineDashPhase";
+
+// NSLayoutConstraint
+NSString * const kPOPLayoutConstraintConstant = @"layoutConstraint.constant";
+
+#if TARGET_OS_IPHONE
+
+// UIView
+NSString * const kPOPViewAlpha = @"view.alpha";
+NSString * const kPOPViewBackgroundColor = @"view.backgroundColor";
+NSString * const kPOPViewBounds = kPOPLayerBounds;
+NSString * const kPOPViewCenter = @"view.center";
+NSString * const kPOPViewFrame = @"view.frame";
+NSString * const kPOPViewScaleX = @"view.scaleX";
+NSString * const kPOPViewScaleXY = @"view.scaleXY";
+NSString * const kPOPViewScaleY = @"view.scaleY";
+NSString * const kPOPViewSize = kPOPLayerSize;
+NSString * const kPOPViewTintColor = @"view.tintColor";
+
+// UIScrollView
+NSString * const kPOPScrollViewContentOffset = @"scrollView.contentOffset";
+NSString * const kPOPScrollViewContentSize = @"scrollView.contentSize";
+NSString * const kPOPScrollViewZoomScale = @"scrollView.zoomScale";
+NSString * const kPOPScrollViewContentInset = @"scrollView.contentInset";
+NSString * const kPOPScrollViewScrollIndicatorInsets = @"scrollView.scrollIndicatorInsets";
+
+// UITableView
+NSString * const kPOPTableViewContentOffset = kPOPScrollViewContentOffset;
+NSString * const kPOPTableViewContentSize = kPOPScrollViewContentSize;
+
+// UICollectionView
+NSString * const kPOPCollectionViewContentOffset = kPOPScrollViewContentOffset;
+NSString * const kPOPCollectionViewContentSize = kPOPScrollViewContentSize;
+
+// UINavigationBar
+NSString * const kPOPNavigationBarBarTintColor = @"navigationBar.barTintColor";
+
+// UIToolbar
+NSString * const kPOPToolbarBarTintColor = kPOPNavigationBarBarTintColor;
+
+// UITabBar
+NSString * const kPOPTabBarBarTintColor = kPOPNavigationBarBarTintColor;
+
+// UILabel
+NSString * const kPOPLabelTextColor = @"label.textColor";
+
+#else
+
+// NSView
+NSString * const kPOPViewFrame = @"view.frame";
+NSString * const kPOPViewBounds = @"view.bounds";
+NSString * const kPOPViewAlphaValue = @"view.alphaValue";
+NSString * const kPOPViewFrameRotation = @"view.frameRotation";
+NSString * const kPOPViewFrameCenterRotation = @"view.frameCenterRotation";
+NSString * const kPOPViewBoundsRotation = @"view.boundsRotation";
+
+// NSWindow
+NSString * const kPOPWindowFrame = @"window.frame";
+NSString * const kPOPWindowAlphaValue = @"window.alphaValue";
+NSString * const kPOPWindowBackgroundColor = @"window.backgroundColor";
+
+#endif
+
+#if SCENEKIT_SDK_AVAILABLE
+
+// SceneKit
+NSString * const kPOPSCNNodePosition = @"scnode.position";
+NSString * const kPOPSCNNodePositionX = @"scnnode.position.x";
+NSString * const kPOPSCNNodePositionY = @"scnnode.position.y";
+NSString * const kPOPSCNNodePositionZ = @"scnnode.position.z";
+NSString * const kPOPSCNNodeTranslation = @"scnnode.translation";
+NSString * const kPOPSCNNodeTranslationX = @"scnnode.translation.x";
+NSString * const kPOPSCNNodeTranslationY = @"scnnode.translation.y";
+NSString * const kPOPSCNNodeTranslationZ = @"scnnode.translation.z";
+NSString * const kPOPSCNNodeRotation = @"scnnode.rotation";
+NSString * const kPOPSCNNodeRotationX = @"scnnode.rotation.x";
+NSString * const kPOPSCNNodeRotationY = @"scnnode.rotation.y";
+NSString * const kPOPSCNNodeRotationZ = @"scnnode.rotation.z";
+NSString * const kPOPSCNNodeRotationW = @"scnnode.rotation.w";
+NSString * const kPOPSCNNodeEulerAngles = @"scnnode.eulerAngles";
+NSString * const kPOPSCNNodeEulerAnglesX = @"scnnode.eulerAngles.x";
+NSString * const kPOPSCNNodeEulerAnglesY = @"scnnode.eulerAngles.y";
+NSString * const kPOPSCNNodeEulerAnglesZ = @"scnnode.eulerAngles.z";
+NSString * const kPOPSCNNodeOrientation = @"scnnode.orientation";
+NSString * const kPOPSCNNodeOrientationX = @"scnnode.orientation.x";
+NSString * const kPOPSCNNodeOrientationY = @"scnnode.orientation.y";
+NSString * const kPOPSCNNodeOrientationZ = @"scnnode.orientation.z";
+NSString * const kPOPSCNNodeOrientationW = @"scnnode.orientation.w";
+NSString * const kPOPSCNNodeScale = @"scnnode.scale";
+NSString * const kPOPSCNNodeScaleX = @"scnnode.scale.x";
+NSString * const kPOPSCNNodeScaleY = @"scnnode.scale.y";
+NSString * const kPOPSCNNodeScaleZ = @"scnnode.scale.z";
+NSString * const kPOPSCNNodeScaleXY = @"scnnode.scale.xy";
+
+#endif
+
+/**
+ State structure internal to static animatable property.
+ */
+typedef struct
+{
+  NSString *name;
+  POPAnimatablePropertyReadBlock readBlock;
+  POPAnimatablePropertyWriteBlock writeBlock;
+  CGFloat threshold;
+} _POPStaticAnimatablePropertyState;
+typedef _POPStaticAnimatablePropertyState POPStaticAnimatablePropertyState;
+
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wglobal-constructors"
+static POPStaticAnimatablePropertyState _staticStates[] =
+{
+  /* CALayer */
+
+  {kPOPLayerBackgroundColor,
+    ^(CALayer *obj, CGFloat values[]) {
+      POPCGColorGetRGBAComponents(obj.backgroundColor, values);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      CGColorRef color = POPCGColorRGBACreate(values);
+      [obj setBackgroundColor:color];
+      CGColorRelease(color);
+    },
+    kPOPThresholdColor
+  },
+
+  {kPOPLayerBounds,
+    ^(CALayer *obj, CGFloat values[]) {
+      values_from_rect(values, [obj bounds]);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      [obj setBounds:values_to_rect(values)];
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerCornerRadius,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = [obj cornerRadius];
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      [obj setCornerRadius:values[0]];
+    },
+    kPOPThresholdRadius
+  },
+
+  {kPOPLayerBorderWidth,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = [obj borderWidth];
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      [obj setBorderWidth:values[0]];
+    },
+    0.01
+  },
+
+  {kPOPLayerBorderColor,
+    ^(CALayer *obj, CGFloat values[]) {
+      POPCGColorGetRGBAComponents(obj.borderColor, values);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      CGColorRef color = POPCGColorRGBACreate(values);
+      [obj setBorderColor:color];
+      CGColorRelease(color);
+    },
+    kPOPThresholdColor
+  },
+
+  {kPOPLayerPosition,
+    ^(CALayer *obj, CGFloat values[]) {
+      values_from_point(values, [(CALayer *)obj position]);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      [obj setPosition:values_to_point(values)];
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerPositionX,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = [(CALayer *)obj position].x;
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      CGPoint p = [(CALayer *)obj position];
+      p.x = values[0];
+      [obj setPosition:p];
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerPositionY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = [(CALayer *)obj position].y;
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      CGPoint p = [(CALayer *)obj position];
+      p.y = values[0];
+      [obj setPosition:p];
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerOpacity,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = [obj opacity];
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      [obj setOpacity:((float)values[0])];
+    },
+    kPOPThresholdOpacity
+  },
+
+  {kPOPLayerScaleX,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetScaleX(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetScaleX(obj, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPLayerScaleY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetScaleY(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetScaleY(obj, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPLayerScaleXY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values_from_point(values, POPLayerGetScaleXY(obj));
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetScaleXY(obj, values_to_point(values));
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPLayerSubscaleXY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values_from_point(values, POPLayerGetSubScaleXY(obj));
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetSubScaleXY(obj, values_to_point(values));
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPLayerTranslationX,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetTranslationX(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetTranslationX(obj, values[0]);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerTranslationY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetTranslationY(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetTranslationY(obj, values[0]);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerTranslationZ,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetTranslationZ(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetTranslationZ(obj, values[0]);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerTranslationXY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values_from_point(values, POPLayerGetTranslationXY(obj));
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetTranslationXY(obj, values_to_point(values));
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerSubtranslationX,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetSubTranslationX(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetSubTranslationX(obj, values[0]);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerSubtranslationY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetSubTranslationY(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetSubTranslationY(obj, values[0]);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerSubtranslationZ,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetSubTranslationZ(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetSubTranslationZ(obj, values[0]);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerSubtranslationXY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values_from_point(values, POPLayerGetSubTranslationXY(obj));
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetSubTranslationXY(obj, values_to_point(values));
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerZPosition,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = [obj zPosition];
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      [obj setZPosition:values[0]];
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerSize,
+    ^(CALayer *obj, CGFloat values[]) {
+      values_from_size(values, [obj bounds].size);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      CGSize size = values_to_size(values);
+      if (size.width < 0. || size.height < 0.)
+        return;
+
+      CGRect b = [obj bounds];
+      b.size = size;
+      [obj setBounds:b];
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPLayerRotation,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetRotation(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetRotation(obj, values[0]);
+    },
+    kPOPThresholdRotation
+  },
+
+  {kPOPLayerRotationY,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetRotationY(obj);
+    },
+    ^(id obj, const CGFloat values[]) {
+      POPLayerSetRotationY(obj, values[0]);
+    },
+    kPOPThresholdRotation
+  },
+
+  {kPOPLayerRotationX,
+    ^(CALayer *obj, CGFloat values[]) {
+      values[0] = POPLayerGetRotationX(obj);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+      POPLayerSetRotationX(obj, values[0]);
+    },
+    kPOPThresholdRotation
+  },
+
+  {kPOPLayerShadowColor,
+    ^(CALayer *obj, CGFloat values[]) {
+        POPCGColorGetRGBAComponents(obj.shadowColor, values);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+        CGColorRef color = POPCGColorRGBACreate(values);
+        [obj setShadowColor:color];
+        CGColorRelease(color);
+    },
+    0.01
+  },
+
+  {kPOPLayerShadowOffset,
+    ^(CALayer *obj, CGFloat values[]) {
+        values_from_size(values, [obj shadowOffset]);
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+        CGSize size = values_to_size(values);
+        [obj setShadowOffset:size];
+    },
+    0.01
+  },
+
+  {kPOPLayerShadowOpacity,
+    ^(CALayer *obj, CGFloat values[]) {
+        values[0] = [obj shadowOpacity];
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+        [obj setShadowOpacity:values[0]];
+    },
+    kPOPThresholdOpacity
+  },
+
+  {kPOPLayerShadowRadius,
+    ^(CALayer *obj, CGFloat values[]) {
+        values[0] = [obj shadowRadius];
+    },
+    ^(CALayer *obj, const CGFloat values[]) {
+        [obj setShadowRadius:values[0]];
+    },
+    kPOPThresholdRadius
+  },
+
+  /* CAShapeLayer */
+
+  {kPOPShapeLayerStrokeStart,
+    ^(CAShapeLayer *obj, CGFloat values[]) {
+      values[0] = obj.strokeStart;
+    },
+    ^(CAShapeLayer *obj, const CGFloat values[]) {
+      obj.strokeStart = values[0];
+    },
+    0.01
+  },
+
+  {kPOPShapeLayerStrokeEnd,
+    ^(CAShapeLayer *obj, CGFloat values[]) {
+      values[0] = obj.strokeEnd;
+    },
+    ^(CAShapeLayer *obj, const CGFloat values[]) {
+      obj.strokeEnd = values[0];
+    },
+    0.01
+  },
+
+  {kPOPShapeLayerStrokeColor,
+    ^(CAShapeLayer *obj, CGFloat values[]) {
+        POPCGColorGetRGBAComponents(obj.strokeColor, values);
+    },
+    ^(CAShapeLayer *obj, const CGFloat values[]) {
+        CGColorRef color = POPCGColorRGBACreate(values);
+        [obj setStrokeColor:color];
+        CGColorRelease(color);
+    },
+    kPOPThresholdColor
+  },
+
+  {kPOPShapeLayerFillColor,
+    ^(CAShapeLayer *obj, CGFloat values[]) {
+        POPCGColorGetRGBAComponents(obj.fillColor, values);
+    },
+    ^(CAShapeLayer *obj, const CGFloat values[]) {
+        CGColorRef color = POPCGColorRGBACreate(values);
+        [obj setFillColor:color];
+        CGColorRelease(color);
+    },
+    kPOPThresholdColor
+  },
+
+  {kPOPShapeLayerLineWidth,
+    ^(CAShapeLayer *obj, CGFloat values[]) {
+        values[0] = obj.lineWidth;
+    },
+    ^(CAShapeLayer *obj, const CGFloat values[]) {
+        obj.lineWidth = values[0];
+    },
+    0.01
+  },
+    
+    {kPOPShapeLayerLineDashPhase,
+        ^(CAShapeLayer *obj, CGFloat values[]) {
+            values[0] = obj.lineDashPhase;
+        },
+        ^(CAShapeLayer *obj, const CGFloat values[]) {
+            obj.lineDashPhase = values[0];
+        },
+        0.01
+    },
+
+  {kPOPLayoutConstraintConstant,
+    ^(NSLayoutConstraint *obj, CGFloat values[]) {
+      values[0] = obj.constant;
+    },
+    ^(NSLayoutConstraint *obj, const CGFloat values[]) {
+      obj.constant = values[0];
+    },
+    0.01
+  },
+
+#if TARGET_OS_IPHONE
+
+  /* UIView */
+
+  {kPOPViewAlpha,
+    ^(UIView *obj, CGFloat values[]) {
+      values[0] = obj.alpha;
+    },
+    ^(UIView *obj, const CGFloat values[]) {
+      obj.alpha = values[0];
+    },
+    kPOPThresholdOpacity
+  },
+
+  {kPOPViewBackgroundColor,
+    ^(UIView *obj, CGFloat values[]) {
+      POPUIColorGetRGBAComponents(obj.backgroundColor, values);
+    },
+    ^(UIView *obj, const CGFloat values[]) {
+      obj.backgroundColor = POPUIColorRGBACreate(values);
+    },
+    kPOPThresholdColor
+  },
+
+  {kPOPViewCenter,
+    ^(UIView *obj, CGFloat values[]) {
+      values_from_point(values, obj.center);
+    },
+    ^(UIView *obj, const CGFloat values[]) {
+      obj.center = values_to_point(values);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPViewFrame,
+    ^(UIView *obj, CGFloat values[]) {
+      values_from_rect(values, obj.frame);
+    },
+    ^(UIView *obj, const CGFloat values[]) {
+      obj.frame = values_to_rect(values);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPViewScaleX,
+    ^(UIView *obj, CGFloat values[]) {
+      values[0] = POPLayerGetScaleX(obj.layer);
+    },
+    ^(UIView *obj, const CGFloat values[]) {
+      POPLayerSetScaleX(obj.layer, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPViewScaleY,
+    ^(UIView *obj, CGFloat values[]) {
+      values[0] = POPLayerGetScaleY(obj.layer);
+    },
+    ^(UIView *obj, const CGFloat values[]) {
+      POPLayerSetScaleY(obj.layer, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPViewScaleXY,
+    ^(UIView *obj, CGFloat values[]) {
+      values_from_point(values, POPLayerGetScaleXY(obj.layer));
+    },
+    ^(UIView *obj, const CGFloat values[]) {
+      POPLayerSetScaleXY(obj.layer, values_to_point(values));
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPViewTintColor,
+    ^(UIView *obj, CGFloat values[]) {
+      POPUIColorGetRGBAComponents(obj.tintColor, values);
+    },
+    ^(UIView *obj, const CGFloat values[]) {
+        obj.tintColor = POPUIColorRGBACreate(values);
+    },
+    kPOPThresholdColor
+  },
+
+  /* UIScrollView */
+
+  {kPOPScrollViewContentOffset,
+    ^(UIScrollView *obj, CGFloat values[]) {
+      values_from_point(values, obj.contentOffset);
+    },
+    ^(UIScrollView *obj, const CGFloat values[]) {
+      [obj setContentOffset:values_to_point(values) animated:NO];
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPScrollViewContentSize,
+    ^(UIScrollView *obj, CGFloat values[]) {
+      values_from_size(values, obj.contentSize);
+    },
+    ^(UIScrollView *obj, const CGFloat values[]) {
+      obj.contentSize = values_to_size(values);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPScrollViewZoomScale,
+    ^(UIScrollView *obj, CGFloat values[]) {
+      values[0]=obj.zoomScale;
+    },
+    ^(UIScrollView *obj, const CGFloat values[]) {
+      obj.zoomScale=values[0];
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPScrollViewContentInset,
+    ^(UIScrollView *obj, CGFloat values[]) {
+      values[0] = obj.contentInset.top;
+      values[1] = obj.contentInset.left;
+      values[2] = obj.contentInset.bottom;
+      values[3] = obj.contentInset.right;
+    },
+    ^(UIScrollView *obj, const CGFloat values[]) {
+      obj.contentInset = values_to_edge_insets(values);
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPScrollViewScrollIndicatorInsets,
+    ^(UIScrollView *obj, CGFloat values[]) {
+      values[0] = obj.scrollIndicatorInsets.top;
+      values[1] = obj.scrollIndicatorInsets.left;
+      values[2] = obj.scrollIndicatorInsets.bottom;
+      values[3] = obj.scrollIndicatorInsets.right;
+    },
+    ^(UIScrollView *obj, const CGFloat values[]) {
+      obj.scrollIndicatorInsets = values_to_edge_insets(values);
+    },
+    kPOPThresholdPoint
+  },
+
+  /* UINavigationBar */
+
+  {kPOPNavigationBarBarTintColor,
+    ^(UINavigationBar *obj, CGFloat values[]) {
+      POPUIColorGetRGBAComponents(obj.barTintColor, values);
+    },
+    ^(UINavigationBar *obj, const CGFloat values[]) {
+      obj.barTintColor = POPUIColorRGBACreate(values);
+    },
+    kPOPThresholdColor
+  },
+
+  /* UILabel */
+
+  {kPOPLabelTextColor,
+    ^(UILabel *obj, CGFloat values[]) {
+      POPUIColorGetRGBAComponents(obj.textColor, values);
+    },
+    ^(UILabel *obj, const CGFloat values[]) {
+      obj.textColor = POPUIColorRGBACreate(values);
+    },
+    kPOPThresholdColor
+  },
+
+#else
+
+  /* NSView */
+
+  {kPOPViewFrame,
+    ^(NSView *obj, CGFloat values[]) {
+      values_from_rect(values, NSRectToCGRect(obj.frame));
+    },
+    ^(NSView *obj, const CGFloat values[]) {
+      obj.frame = NSRectFromCGRect(values_to_rect(values));
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPViewBounds,
+    ^(NSView *obj, CGFloat values[]) {
+      values_from_rect(values, NSRectToCGRect(obj.frame));
+    },
+    ^(NSView *obj, const CGFloat values[]) {
+      obj.bounds = NSRectFromCGRect(values_to_rect(values));
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPViewAlphaValue,
+    ^(NSView *obj, CGFloat values[]) {
+      values[0] = obj.alphaValue;
+    },
+    ^(NSView *obj, const CGFloat values[]) {
+      obj.alphaValue = values[0];
+    },
+    kPOPThresholdOpacity
+  },
+
+  {kPOPViewFrameRotation,
+    ^(NSView *obj, CGFloat values[]) {
+      values[0] = obj.frameRotation;
+    },
+    ^(NSView *obj, const CGFloat values[]) {
+      obj.frameRotation = values[0];
+    },
+    kPOPThresholdRotation
+  },
+
+  {kPOPViewFrameCenterRotation,
+    ^(NSView *obj, CGFloat values[]) {
+      values[0] = obj.frameCenterRotation;
+    },
+    ^(NSView *obj, const CGFloat values[]) {
+      obj.frameCenterRotation = values[0];
+    },
+    kPOPThresholdRotation
+  },
+
+  {kPOPViewBoundsRotation,
+    ^(NSView *obj, CGFloat values[]) {
+      values[0] = obj.boundsRotation;
+    },
+    ^(NSView *obj, const CGFloat values[]) {
+      obj.boundsRotation = values[0];
+    },
+    kPOPThresholdRotation
+  },
+
+  /* NSWindow */
+
+  {kPOPWindowFrame,
+    ^(NSWindow *obj, CGFloat values[]) {
+      values_from_rect(values, NSRectToCGRect(obj.frame));
+    },
+    ^(NSWindow *obj, const CGFloat values[]) {
+      [obj setFrame:NSRectFromCGRect(values_to_rect(values)) display:YES];
+    },
+    kPOPThresholdPoint
+  },
+
+  {kPOPWindowAlphaValue,
+    ^(NSWindow *obj, CGFloat values[]) {
+      values[0] = obj.alphaValue;
+    },
+    ^(NSWindow *obj, const CGFloat values[]) {
+      obj.alphaValue = values[0];
+    },
+    kPOPThresholdOpacity
+  },
+
+  {kPOPWindowBackgroundColor,
+    ^(NSWindow *obj, CGFloat values[]) {
+      POPNSColorGetRGBAComponents(obj.backgroundColor, values);
+    },
+    ^(NSWindow *obj, const CGFloat values[]) {
+      obj.backgroundColor = POPNSColorRGBACreate(values);
+    },
+    kPOPThresholdColor
+  },
+
+#endif
+
+#if SCENEKIT_SDK_AVAILABLE
+
+  /* SceneKit */
+
+  {kPOPSCNNodePosition,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values_from_vec3(values, obj.position);
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.position = values_to_vec3(values);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodePositionX,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.position.x;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.position = SCNVector3Make(values[0], obj.position.y, obj.position.z);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodePositionY,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.position.y;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.position = SCNVector3Make(obj.position.x, values[0], obj.position.z);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodePositionZ,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.position.z;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.position = SCNVector3Make(obj.position.x, obj.position.y, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeTranslation,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.transform.m41;
+      values[1] = obj.transform.m42;
+      values[2] = obj.transform.m43;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.transform = SCNMatrix4MakeTranslation(values[0], values[1], values[2]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeTranslationX,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.transform.m41;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.transform = SCNMatrix4MakeTranslation(values[0], obj.transform.m42, obj.transform.m43);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeTranslationY,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.transform.m42;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.transform = SCNMatrix4MakeTranslation(obj.transform.m41, values[0], obj.transform.m43);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeTranslationY,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.transform.m43;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.transform = SCNMatrix4MakeTranslation(obj.transform.m41, obj.transform.m42, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeRotation,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values_from_vec4(values, obj.rotation);
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.rotation = values_to_vec4(values);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeRotationX,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.rotation.x;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.rotation = SCNVector4Make(1.0, obj.rotation.y, obj.rotation.z, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeRotationY,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.rotation.y;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.rotation = SCNVector4Make(obj.rotation.x, 1.0, obj.rotation.z, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeRotationZ,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.rotation.z;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.rotation = SCNVector4Make(obj.rotation.x, obj.rotation.y, 1.0, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeRotationW,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.rotation.w;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.rotation = SCNVector4Make(obj.rotation.x, obj.rotation.y, obj.rotation.z, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeEulerAngles,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values_from_vec3(values, obj.eulerAngles);
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.eulerAngles = values_to_vec3(values);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeEulerAnglesX,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.eulerAngles.x;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.eulerAngles = SCNVector3Make(values[0], obj.eulerAngles.y, obj.eulerAngles.z);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeEulerAnglesY,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.eulerAngles.y;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.eulerAngles = SCNVector3Make(obj.eulerAngles.x, values[0], obj.eulerAngles.z);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeEulerAnglesZ,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.eulerAngles.z;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.eulerAngles = SCNVector3Make(obj.eulerAngles.x, obj.eulerAngles.y, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeOrientation,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values_from_vec4(values, obj.orientation);
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.orientation = values_to_vec4(values);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeOrientationX,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.orientation.x;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.orientation = SCNVector4Make(values[0], obj.orientation.y, obj.orientation.z, obj.orientation.w);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeOrientationY,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.orientation.y;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.orientation = SCNVector4Make(obj.orientation.x, values[0], obj.orientation.z, obj.orientation.w);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeOrientationZ,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.orientation.z;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.orientation = SCNVector4Make(obj.orientation.x, obj.orientation.y, values[0], obj.orientation.w);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeOrientationW,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.orientation.w;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.orientation = SCNVector4Make(obj.orientation.x, obj.orientation.y, obj.orientation.z, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeScale,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values_from_vec3(values, obj.scale);
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.scale = values_to_vec3(values);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeScaleX,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.scale.x;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.scale = SCNVector3Make(values[0], obj.scale.y, obj.scale.z);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeScaleY,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.scale.y;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.position = SCNVector3Make(obj.scale.x, values[0], obj.scale.z);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeScaleZ,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.scale.z;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.scale = SCNVector3Make(obj.scale.x, obj.scale.y, values[0]);
+    },
+    kPOPThresholdScale
+  },
+
+  {kPOPSCNNodeScaleXY,
+    ^(SCNNode *obj, CGFloat values[]) {
+      values[0] = obj.scale.x;
+      values[1] = obj.scale.y;
+    },
+    ^(SCNNode *obj, const CGFloat values[]) {
+      obj.scale = SCNVector3Make(values[0], values[1], obj.scale.z);
+    },
+    kPOPThresholdScale
+  },
+
+#endif
+
+};
+#pragma clang diagnostic pop
+
+static NSUInteger staticIndexWithName(NSString *aName)
+{
+  NSUInteger idx = 0;
+
+  while (idx < POP_ARRAY_COUNT(_staticStates)) {
+    if ([_staticStates[idx].name isEqualToString:aName])
+      return idx;
+    idx++;
+  }
+
+  return NSNotFound;
+}
+
+/**
+ Concrete static property class.
+ */
+@interface POPStaticAnimatableProperty : POPAnimatableProperty
+{
+@public
+  POPStaticAnimatablePropertyState *_state;
+}
+@end
+
+@implementation POPStaticAnimatableProperty
+
+- (NSString *)name
+{
+  return _state->name;
+}
+
+- (POPAnimatablePropertyReadBlock)readBlock
+{
+  return _state->readBlock;
+}
+
+- (POPAnimatablePropertyWriteBlock)writeBlock
+{
+  return _state->writeBlock;
+}
+
+- (CGFloat)threshold
+{
+  return _state->threshold;
+}
+
+@end
+
+#pragma mark - Concrete
+
+/**
+ Concrete immutable property class.
+ */
+@interface POPConcreteAnimatableProperty : POPAnimatableProperty
+- (instancetype)initWithName:(NSString *)name readBlock:(POPAnimatablePropertyReadBlock)read writeBlock:(POPAnimatablePropertyWriteBlock)write threshold:(CGFloat)threshold;
+@end
+
+@implementation POPConcreteAnimatableProperty
+
+// default synthesis
+@synthesize name, readBlock, writeBlock, threshold;
+
+- (instancetype)initWithName:(NSString *)aName readBlock:(POPAnimatablePropertyReadBlock)aReadBlock writeBlock:(POPAnimatablePropertyWriteBlock)aWriteBlock threshold:(CGFloat)aThreshold
+{
+  self = [super init];
+  if (nil != self) {
+    name = [aName copy];
+    readBlock = [aReadBlock copy];
+    writeBlock = [aWriteBlock copy];
+    threshold = aThreshold;
+  }
+  return self;
+}
+@end
+
+#pragma mark - Mutable
+
+@implementation POPMutableAnimatableProperty
+
+// default synthesis
+@synthesize name, readBlock, writeBlock, threshold;
+
+@end
+
+#pragma mark - Cluster
+
+/**
+ Singleton placeholder property class to support class cluster.
+ */
+@interface POPPlaceholderAnimatableProperty : POPAnimatableProperty
+
+@end
+
+@implementation POPPlaceholderAnimatableProperty
+
+// default synthesis
+@synthesize name, readBlock, writeBlock, threshold;
+
+@end
+
+/**
+ Cluster class.
+ */
+@implementation POPAnimatableProperty
+
+// avoid creating backing ivars
+@dynamic name, readBlock, writeBlock, threshold;
+
+static POPAnimatableProperty *placeholder = nil;
+
++ (void)initialize
+{
+  if (self == [POPAnimatableProperty class]) {
+    placeholder = [POPPlaceholderAnimatableProperty alloc];
+  }
+}
+
++ (id)allocWithZone:(struct _NSZone *)zone
+{
+  if (self == [POPAnimatableProperty class]) {
+    if (nil == placeholder) {
+      placeholder = [super allocWithZone:zone];
+    }
+    return placeholder;
+  }
+  return [super allocWithZone:zone];
+}
+
+- (id)copyWithZone:(NSZone *)zone
+{
+  if ([self isKindOfClass:[POPMutableAnimatableProperty class]]) {
+    POPConcreteAnimatableProperty *copyProperty = [[POPConcreteAnimatableProperty alloc] initWithName:self.name readBlock:self.readBlock writeBlock:self.writeBlock threshold:self.threshold];
+    return copyProperty;
+  } else {
+    return self;
+  }
+}
+
+- (id)mutableCopyWithZone:(NSZone *)zone
+{
+  POPMutableAnimatableProperty *copyProperty = [[POPMutableAnimatableProperty alloc] init];
+  copyProperty.name = self.name;
+  copyProperty.readBlock = self.readBlock;
+  copyProperty.writeBlock = self.writeBlock;
+  copyProperty.threshold = self.threshold;
+  return copyProperty;
+}
+
++ (id)propertyWithName:(NSString *)aName
+{
+  return [self propertyWithName:aName initializer:NULL];
+}
+
++ (id)propertyWithName:(NSString *)aName initializer:(void (^)(POPMutableAnimatableProperty *prop))aBlock
+{
+  POPAnimatableProperty *prop = nil;
+
+  static NSMutableDictionary *_propertyDict = nil;
+  if (nil == _propertyDict) {
+    _propertyDict = [[NSMutableDictionary alloc] initWithCapacity:10];
+  }
+
+  prop = _propertyDict[aName];
+  if (nil != prop) {
+    return prop;
+  }
+
+  NSUInteger staticIdx = staticIndexWithName(aName);
+
+  if (NSNotFound != staticIdx) {
+    POPStaticAnimatableProperty *staticProp = [[POPStaticAnimatableProperty alloc] init];
+    staticProp->_state = &_staticStates[staticIdx];
+    _propertyDict[aName] = staticProp;
+    prop = staticProp;
+  } else if (NULL != aBlock) {
+    POPMutableAnimatableProperty *mutableProp = [[POPMutableAnimatableProperty alloc] init];
+    mutableProp.name = aName;
+    mutableProp.threshold = 1.0;
+    aBlock(mutableProp);
+    prop = [mutableProp copy];
+  }
+
+  return prop;
+}
+
+- (NSString *)description
+{
+  NSMutableString *s = [NSMutableString stringWithFormat:@"%@ name:%@ threshold:%f", super.description, self.name, self.threshold];
+  return s;
+}
+
+@end

pop/POPAnimatablePropertyTypes.h

@@ -0,0 +1,11 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+typedef void (^POPAnimatablePropertyReadBlock)(id obj, CGFloat values[]);
+typedef void (^POPAnimatablePropertyWriteBlock)(id obj, const CGFloat values[]);

pop/POPAnimation.h

@@ -0,0 +1,188 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/NSObject.h>
+
+#import <pop/POPAnimationTracer.h>
+#import <pop/POPGeometry.h>
+
+@class CAMediaTimingFunction;
+
+/**
+ @abstract The abstract animation base class.
+ @discussion Instantiate and use one of the concrete animation subclasses.
+ */
+@interface POPAnimation : NSObject
+
+/**
+ @abstract The name of the animation.
+ @discussion Optional property to help identify the animation.
+ */
+@property (copy, nonatomic) NSString *name;
+
+/**
+ @abstract The beginTime of the animation in media time.
+ @discussion Defaults to 0 and starts immediately.
+ */
+@property (assign, nonatomic) CFTimeInterval beginTime;
+
+/**
+ @abstract The animation delegate.
+ @discussion See {@ref POPAnimationDelegate} for details.
+ */
+@property (weak, nonatomic) id delegate;
+
+/**
+ @abstract The animation tracer.
+ @discussion Returns the existing tracer, creating one if needed. Call start/stop on the tracer to toggle event collection.
+ */
+@property (readonly, nonatomic) POPAnimationTracer *tracer;
+
+/**
+ @abstract Optional block called on animation start.
+ */
+@property (copy, nonatomic) void (^animationDidStartBlock)(POPAnimation *anim);
+
+/**
+ @abstract Optional block called when value meets or exceeds to value.
+ */
+@property (copy, nonatomic) void (^animationDidReachToValueBlock)(POPAnimation *anim);
+
+/**
+ @abstract Optional block called on animation completion.
+ */
+@property (copy, nonatomic) void (^completionBlock)(POPAnimation *anim, BOOL finished);
+
+/**
+ @abstract Optional block called each frame animation is applied.
+ */
+@property (copy, nonatomic) void (^animationDidApplyBlock)(POPAnimation *anim);
+
+/**
+ @abstract Flag indicating whether animation should be removed on completion.
+ @discussion Setting to NO can facilitate animation reuse. Defaults to YES.
+ */
+@property (assign, nonatomic) BOOL removedOnCompletion;
+
+/**
+ @abstract Flag indicating whether animation is paused.
+ @discussion A paused animation is excluded from the list of active animations. On initial creation, defaults to YES. On animation addition, the animation is implicity unpaused. On animation completion, the animation is implicity paused including for animations with removedOnCompletion set to NO.
+ */
+@property (assign, nonatomic, getter = isPaused) BOOL paused;
+
+/**
+ @abstract Flag indicating whether animation autoreverses.
+ @discussion An animation that autoreverses will have twice the duration before it is considered finished. It will animate to the toValue, stop, then animate back to the original fromValue. The delegate methods are called as follows:
+
+     1) animationDidStart: is called at the beginning, as usual, and then after each toValue is reached and the autoreverse is going to start.
+     2) animationDidReachToValue: is called every time the toValue is reached. The toValue is swapped with the fromValue at the end of each animation segment. This means that with autoreverses set to YES, the animationDidReachToValue: delegate method will be called a minimum of twice.
+     3) animationDidStop:finished: is called every time the toValue is reached, the finished argument will be NO if the autoreverse is not yet complete.
+ */
+@property (assign, nonatomic) BOOL autoreverses;
+
+/**
+ @abstract The number of times to repeat the animation.
+ @discussion A repeatCount of 0 or 1 means that the animation will not repeat, just like Core Animation. A repeatCount of 2 or greater means that the animation will run that many times before stopping. The delegate methods are called as follows:
+
+     1) animationDidStart: is called at the beginning of each animation repeat.
+     2) animationDidReachToValue: is called every time the toValue is reached.
+     3) animationDidStop:finished: is called every time the toValue is reached, the finished argument will be NO if the autoreverse is not yet complete.
+
+When combined with the autoreverses property, a singular animation is effectively twice as long.
+ */
+@property (assign, nonatomic) NSInteger repeatCount;
+
+/**
+ @abstract Repeat the animation forever.
+ @discussion This property will make the animation repeat forever. The value of the repeatCount property is undefined when this property is set. The finished parameter of the delegate callback animationDidStop:finished: will always be NO.
+ */
+@property (assign, nonatomic) BOOL repeatForever;
+
+@end
+
+/**
+ @abstract The animation delegate.
+ */
+@protocol POPAnimationDelegate <NSObject>
+@optional
+
+/**
+ @abstract Called on animation start.
+ @param anim The relevant animation.
+ */
+- (void)pop_animationDidStart:(POPAnimation *)anim;
+
+/**
+ @abstract Called when value meets or exceeds to value.
+ @param anim The relevant animation.
+ */
+- (void)pop_animationDidReachToValue:(POPAnimation *)anim;
+
+/**
+ @abstract Called on animation stop.
+ @param anim The relevant animation.
+ @param finished Flag indicating finished state. Flag is true if the animation reached completion before being removed.
+ */
+- (void)pop_animationDidStop:(POPAnimation *)anim finished:(BOOL)finished;
+
+/**
+ @abstract Called each frame animation is applied.
+ @param anim The relevant animation.
+ */
+- (void)pop_animationDidApply:(POPAnimation *)anim;
+
+@end
+
+
+@interface NSObject (POP)
+
+/**
+ @abstract Add an animation to the reciver.
+ @param anim The animation to add.
+ @param key The key used to identify the animation.
+ @discussion The 'key' may be any string such that only one animation per unique key is added per object.
+ */
+- (void)pop_addAnimation:(POPAnimation *)anim forKey:(NSString *)key;
+
+/**
+ @abstract Remove all animations attached to the receiver.
+ */
+- (void)pop_removeAllAnimations;
+
+/**
+ @abstract Remove any animation attached to the receiver for 'key'.
+ @param key The key used to identify the animation.
+ */
+- (void)pop_removeAnimationForKey:(NSString *)key;
+
+/**
+ @abstract Returns an array containing the keys of all animations currently attached to the receiver.
+ The order of keys reflects the order in which animations will be applied.
+ */
+- (NSArray *)pop_animationKeys;
+
+/**
+ @abstract Returns any animation attached to the receiver.
+ @param key The key used to identify the animation.
+ @returns The animation currently attached, or nil if no such animation exists.
+ */
+- (id)pop_animationForKey:(NSString *)key;
+
+@end
+
+/**
+ *  This implementation of NSCopying does not do any copying of animation's state, but only configuration.
+ *  i.e. you cannot copy an animation and expect to apply it to a view and have the copied animation pick up where the original left off.
+ *  Two common uses of copying animations:
+ *  * you need to apply the same animation to multiple different views.
+ *  * you need to absolutely ensure that the the caller of your function cannot mutate the animation once it's been passed in.
+ */
+@interface POPAnimation (NSCopying) <NSCopying>
+
+@end

pop/POPAnimation.mm

@@ -0,0 +1,303 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimationExtras.h"
+#import "POPAnimationInternal.h"
+
+#import <objc/runtime.h>
+
+#import "POPAction.h"
+#import "POPAnimationRuntime.h"
+#import "POPAnimationTracerInternal.h"
+#import "POPAnimatorPrivate.h"
+
+using namespace POP;
+
+#pragma mark - POPAnimation
+
+@implementation POPAnimation
+@synthesize solver = _solver;
+@synthesize currentValue = _currentValue;
+@synthesize progressMarkers = _progressMarkers;
+
+#pragma mark - Lifecycle
+
+- (id)init
+{
+  [NSException raise:NSStringFromClass([self class]) format:@"Attempting to instantiate an abstract class. Use a concrete subclass instead."];
+  return nil;
+}
+
+- (id)_init
+{
+  self = [super init];
+  if (nil != self) {
+    [self _initState];
+  }
+  return self;
+}
+
+- (void)_initState
+{
+  _state = new POPAnimationState(self);
+}
+
+- (void)dealloc
+{
+  if (_state) {
+    delete _state;
+    _state = NULL;
+  };
+}
+
+#pragma mark - Properties
+
+- (id)delegate
+{
+  return _state->delegate;
+}
+
+- (void)setDelegate:(id)delegate
+{
+  _state->setDelegate(delegate);
+}
+
+- (BOOL)isPaused
+{
+  return _state->paused;
+}
+
+- (void)setPaused:(BOOL)paused
+{
+  _state->setPaused(paused ? true : false);
+}
+
+- (NSInteger)repeatCount
+{
+  if (_state->autoreverses) {
+    return _state->repeatCount / 2;
+  } else {
+    return _state->repeatCount;
+  }
+}
+
+- (void)setRepeatCount:(NSInteger)repeatCount
+{
+  if (repeatCount > 0) {
+    if (repeatCount > NSIntegerMax / 2) {
+      repeatCount = NSIntegerMax / 2;
+    }
+
+    if (_state->autoreverses) {
+      _state->repeatCount = (repeatCount * 2);
+    } else {
+      _state->repeatCount = repeatCount;
+    }
+  }
+}
+
+- (BOOL)autoreverses
+{
+  return _state->autoreverses;
+}
+
+- (void)setAutoreverses:(BOOL)autoreverses
+{
+  _state->autoreverses = autoreverses;
+  if (autoreverses) {
+    if (_state->repeatCount == 0) {
+      [self setRepeatCount:1];
+    }
+  }
+}
+
+FB_PROPERTY_GET(POPAnimationState, type, POPAnimationType);
+DEFINE_RW_PROPERTY_OBJ_COPY(POPAnimationState, animationDidStartBlock, setAnimationDidStartBlock:, POPAnimationDidStartBlock);
+DEFINE_RW_PROPERTY_OBJ_COPY(POPAnimationState, animationDidReachToValueBlock, setAnimationDidReachToValueBlock:, POPAnimationDidReachToValueBlock);
+DEFINE_RW_PROPERTY_OBJ_COPY(POPAnimationState, completionBlock, setCompletionBlock:, POPAnimationCompletionBlock);
+DEFINE_RW_PROPERTY_OBJ_COPY(POPAnimationState, animationDidApplyBlock, setAnimationDidApplyBlock:, POPAnimationDidApplyBlock);
+DEFINE_RW_PROPERTY_OBJ_COPY(POPAnimationState, name, setName:, NSString*);
+DEFINE_RW_PROPERTY(POPAnimationState, beginTime, setBeginTime:, CFTimeInterval);
+DEFINE_RW_FLAG(POPAnimationState, removedOnCompletion, removedOnCompletion, setRemovedOnCompletion:);
+DEFINE_RW_FLAG(POPAnimationState, repeatForever, repeatForever, setRepeatForever:);
+
+- (id)valueForUndefinedKey:(NSString *)key
+{
+  return _state->dict[key];
+}
+
+- (void)setValue:(id)value forUndefinedKey:(NSString *)key
+{
+  if (!value) {
+    [_state->dict removeObjectForKey:key];
+  } else {
+    if (!_state->dict)
+      _state->dict = [[NSMutableDictionary alloc] init];
+    _state->dict[key] = value;
+  }
+}
+
+- (POPAnimationTracer *)tracer
+{
+  if (!_state->tracer) {
+    _state->tracer = [[POPAnimationTracer alloc] initWithAnimation:self];
+  }
+  return _state->tracer;
+}
+
+- (NSString *)description
+{
+  NSMutableString *s = [NSMutableString stringWithFormat:@"<%@:%p", NSStringFromClass([self class]), self];
+  [self _appendDescription:s debug:NO];
+  [s appendString:@">"];
+  return s;
+}
+
+- (NSString *)debugDescription
+{
+  NSMutableString *s = [NSMutableString stringWithFormat:@"<%@:%p", NSStringFromClass([self class]), self];
+  [self _appendDescription:s debug:YES];
+  [s appendString:@">"];
+  return s;
+}
+
+#pragma mark - Utility
+
+POPAnimationState *POPAnimationGetState(POPAnimation *a)
+{
+  return a->_state;
+}
+
+- (BOOL)_advance:(id)object currentTime:(CFTimeInterval)currentTime elapsedTime:(CFTimeInterval)elapsedTime
+{
+  return YES;
+}
+
+- (void)_appendDescription:(NSMutableString *)s debug:(BOOL)debug
+{
+  if (_state->name)
+    [s appendFormat:@"; name = %@", _state->name];
+  
+  if (!self.removedOnCompletion)
+    [s appendFormat:@"; removedOnCompletion = %@", POPStringFromBOOL(self.removedOnCompletion)];
+  
+  if (debug) {
+    if (_state->active)
+      [s appendFormat:@"; active = %@", POPStringFromBOOL(_state->active)];
+    
+    if (_state->paused)
+      [s appendFormat:@"; paused = %@", POPStringFromBOOL(_state->paused)];
+  }
+  
+  if (_state->beginTime) {
+    [s appendFormat:@"; beginTime = %f", _state->beginTime];
+  }
+  
+  for (NSString *key in _state->dict) {
+    [s appendFormat:@"; %@ = %@", key, _state->dict[key]];
+  }
+}
+
+@end
+
+
+#pragma mark - POPPropertyAnimation
+
+#pragma mark - POPBasicAnimation
+
+#pragma mark - POPDecayAnimation
+
+@implementation NSObject (POP)
+
+- (void)pop_addAnimation:(POPAnimation *)anim forKey:(NSString *)key
+{
+  [[POPAnimator sharedAnimator] addAnimation:anim forObject:self key:key];
+}
+
+- (void)pop_removeAllAnimations
+{
+  [[POPAnimator sharedAnimator] removeAllAnimationsForObject:self];
+}
+
+- (void)pop_removeAnimationForKey:(NSString *)key
+{
+  [[POPAnimator sharedAnimator] removeAnimationForObject:self key:key];
+}
+
+- (NSArray *)pop_animationKeys
+{
+  return [[POPAnimator sharedAnimator] animationKeysForObject:self];
+}
+
+- (id)pop_animationForKey:(NSString *)key
+{
+  return [[POPAnimator sharedAnimator] animationForObject:self key:key];
+}
+
+@end
+
+@implementation NSProxy (POP)
+
+- (void)pop_addAnimation:(POPAnimation *)anim forKey:(NSString *)key
+{
+  [[POPAnimator sharedAnimator] addAnimation:anim forObject:self key:key];
+}
+
+- (void)pop_removeAllAnimations
+{
+  [[POPAnimator sharedAnimator] removeAllAnimationsForObject:self];
+}
+
+- (void)pop_removeAnimationForKey:(NSString *)key
+{
+  [[POPAnimator sharedAnimator] removeAnimationForObject:self key:key];
+}
+
+- (NSArray *)pop_animationKeys
+{
+  return [[POPAnimator sharedAnimator] animationKeysForObject:self];
+}
+
+- (id)pop_animationForKey:(NSString *)key
+{
+  return [[POPAnimator sharedAnimator] animationForObject:self key:key];
+}
+
+@end
+
+@implementation POPAnimation (NSCopying)
+
+- (instancetype)copyWithZone:(NSZone *)zone
+{
+  /*
+   * Must use [self class] instead of POPAnimation so that subclasses can call this via super.
+   * Even though POPAnimation and POPPropertyAnimation throw exceptions on init,
+   * it's safe to call it since you can only copy objects that have been successfully created.
+   */
+  POPAnimation *copy = [[[self class] allocWithZone:zone] init];
+  
+  if (copy) {
+    copy.name = self.name;
+    copy.beginTime = self.beginTime;
+    copy.delegate = self.delegate;
+    copy.animationDidStartBlock = self.animationDidStartBlock;
+    copy.animationDidReachToValueBlock = self.animationDidReachToValueBlock;
+    copy.completionBlock = self.completionBlock;
+    copy.animationDidApplyBlock = self.animationDidApplyBlock;
+    copy.removedOnCompletion = self.removedOnCompletion;
+    
+    copy.autoreverses = self.autoreverses;
+    copy.repeatCount = self.repeatCount;
+    copy.repeatForever = self.repeatForever;
+  }
+    
+  return copy;
+}
+
+@end

pop/POPAnimationEvent.h

@@ -0,0 +1,69 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+/**
+ @abstract Enumeraton of animation event types.
+ */
+typedef NS_ENUM(NSUInteger, POPAnimationEventType) {
+  kPOPAnimationEventPropertyRead = 0,
+  kPOPAnimationEventPropertyWrite,
+  kPOPAnimationEventToValueUpdate,
+  kPOPAnimationEventFromValueUpdate,
+  kPOPAnimationEventVelocityUpdate,
+  kPOPAnimationEventBouncinessUpdate,
+  kPOPAnimationEventSpeedUpdate,
+  kPOPAnimationEventFrictionUpdate,
+  kPOPAnimationEventMassUpdate,
+  kPOPAnimationEventTensionUpdate,
+  kPOPAnimationEventDidStart,
+  kPOPAnimationEventDidStop,
+  kPOPAnimationEventDidReachToValue,
+  kPOPAnimationEventAutoreversed
+};
+
+/**
+ @abstract The base animation event class.
+ */
+@interface POPAnimationEvent : NSObject
+
+/**
+ @abstract The event type. See {@ref POPAnimationEventType} for possible values.
+ */
+@property (readonly, nonatomic, assign) POPAnimationEventType type;
+
+/**
+ @abstract The time of event.
+ */
+@property (readonly, nonatomic, assign) CFTimeInterval time;
+
+/**
+ @abstract Optional string describing the animation at time of event.
+ */
+@property (readonly, nonatomic, copy) NSString *animationDescription;
+
+@end
+
+/**
+ @abstract An animation event subclass for recording value and velocity.
+ */
+@interface POPAnimationValueEvent : POPAnimationEvent
+
+/**
+ @abstract The value recorded.
+ */
+@property (readonly, nonatomic, strong) id value;
+
+/**
+ @abstract The velocity recorded, if any.
+ */
+@property (readonly, nonatomic, strong) id velocity;
+
+@end

pop/POPAnimationEvent.mm

@@ -0,0 +1,108 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimationEvent.h"
+#import "POPAnimationEventInternal.h"
+
+static NSString *stringFromType(POPAnimationEventType aType)
+{
+  switch (aType) {
+    case kPOPAnimationEventPropertyRead:
+      return @"read";
+    case kPOPAnimationEventPropertyWrite:
+      return @"write";
+    case kPOPAnimationEventToValueUpdate:
+      return @"toValue";
+    case kPOPAnimationEventFromValueUpdate:
+      return @"fromValue";
+    case kPOPAnimationEventVelocityUpdate:
+      return @"velocity";
+    case kPOPAnimationEventSpeedUpdate:
+      return @"speed";
+    case kPOPAnimationEventBouncinessUpdate:
+      return @"bounciness";
+    case kPOPAnimationEventFrictionUpdate:
+      return @"friction";
+    case kPOPAnimationEventMassUpdate:
+      return @"mass";
+    case kPOPAnimationEventTensionUpdate:
+      return @"tension";
+    case kPOPAnimationEventDidStart:
+      return @"didStart";
+    case kPOPAnimationEventDidStop:
+      return @"didStop";
+    case kPOPAnimationEventDidReachToValue:
+      return @"didReachToValue";
+    case kPOPAnimationEventAutoreversed:
+      return @"autoreversed";
+    default:
+      return nil;
+  }
+}
+
+@implementation POPAnimationEvent
+@synthesize type = _type;
+@synthesize time = _time;
+@synthesize animationDescription = _animationDescription;
+
+- (instancetype)initWithType:(POPAnimationEventType)aType time:(CFTimeInterval)aTime
+{
+  self = [super init];
+  if (nil != self) {
+    _type = aType;
+    _time = aTime;
+  }
+  return self;
+}
+
+- (NSString *)description
+{
+  NSMutableString *s = [NSMutableString stringWithFormat:@"<POPAnimationEvent:%f; type = %@", _time, stringFromType(_type)];
+  [self _appendDescription:s];
+  [s appendString:@">"];
+  return s;
+}
+
+// subclass override
+- (void)_appendDescription:(NSMutableString *)s
+{
+  if (0 != _animationDescription.length) {
+    [s appendFormat:@"; animation = %@", _animationDescription];
+  }
+}
+
+@end
+
+@implementation POPAnimationValueEvent
+@synthesize value = _value;
+@synthesize velocity = _velocity;
+
+- (instancetype)initWithType:(POPAnimationEventType)aType time:(CFTimeInterval)aTime value:(id)aValue
+{
+  self = [self initWithType:aType time:aTime];
+  if (nil != self) {
+    _value = aValue;
+  }
+  return self;
+}
+
+- (void)_appendDescription:(NSMutableString *)s
+{
+  [super _appendDescription:s];
+
+  if (nil != _value) {
+    [s appendFormat:@"; value = %@", _value];
+  }
+
+  if (nil != _velocity) {
+    [s appendFormat:@"; velocity = %@", _velocity];
+  }
+}
+
+@end

pop/POPAnimationEventInternal.h

@@ -0,0 +1,41 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import "POPAnimationEvent.h"
+
+@interface POPAnimationEvent ()
+
+/**
+ @abstract Default initializer.
+ */
+- (instancetype)initWithType:(POPAnimationEventType)type time:(CFTimeInterval)time;
+
+/**
+ @abstract Readwrite redefinition of public property.
+ */
+@property (readwrite, nonatomic, copy) NSString *animationDescription;
+
+@end
+
+@interface POPAnimationValueEvent ()
+
+/**
+ @abstract Default initializer.
+ */
+- (instancetype)initWithType:(POPAnimationEventType)type time:(CFTimeInterval)time value:(id)value;
+
+/**
+ @abstract Readwrite redefinition of public property.
+ */
+@property (readwrite, nonatomic, strong) id velocity;
+
+@end
+

pop/POPAnimationExtras.h

@@ -0,0 +1,43 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <QuartzCore/CAAnimation.h>
+
+#import <pop/POPDefines.h>
+#import <pop/POPSpringAnimation.h>
+
+/**
+ @abstract The current drag coefficient.
+ @discussion A value greater than 1.0 indicates Simulator slow-motion animations are enabled. Defaults to 1.0.
+ */
+extern CGFloat POPAnimationDragCoefficient(void);
+
+@interface CAAnimation (POPAnimationExtras)
+
+/**
+ @abstract Apply the current drag coefficient to animation speed.
+ @discussion Convenience utility to respect Simulator slow-motion animation settings.
+ */
+- (void)pop_applyDragCoefficient;
+
+@end
+
+@interface POPSpringAnimation (POPAnimationExtras)
+
+/**
+ @abstract Converts from spring bounciness and speed to tension, friction and mass dynamics values.
+ */
++ (void)convertBounciness:(CGFloat)bounciness speed:(CGFloat)speed toTension:(CGFloat *)outTension friction:(CGFloat *)outFriction mass:(CGFloat *)outMass;
+
+/**
+ @abstract Converts from dynamics tension, friction and mass to spring bounciness and speed values.
+ */
++ (void)convertTension:(CGFloat)tension friction:(CGFloat)friction toBounciness:(CGFloat *)outBounciness speed:(CGFloat *)outSpeed;
+
+@end

pop/POPAnimationExtras.mm

@@ -0,0 +1,117 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimationExtras.h"
+#import "POPAnimationPrivate.h"
+
+#if TARGET_OS_IPHONE
+#import <UIKit/UIKit.h>
+#endif
+
+#if TARGET_IPHONE_SIMULATOR
+UIKIT_EXTERN float UIAnimationDragCoefficient(); // UIKit private drag coefficient, use judiciously
+#endif
+
+#import "POPMath.h"
+
+CGFloat POPAnimationDragCoefficient()
+{
+#if TARGET_IPHONE_SIMULATOR
+  return UIAnimationDragCoefficient();
+#else
+  return 1.0;
+#endif
+}
+
+@implementation CAAnimation (POPAnimationExtras)
+
+- (void)pop_applyDragCoefficient
+{
+  CGFloat k = POPAnimationDragCoefficient();
+  if (k != 0 && k != 1)
+    self.speed = 1 / k;
+}
+
+@end
+
+@implementation POPSpringAnimation (POPAnimationExtras)
+
+static const CGFloat POPBouncy3NormalizationRange = 20.0;
+static const CGFloat POPBouncy3NormalizationScale = 1.7;
+static const CGFloat POPBouncy3BouncinessNormalizedMin = 0.0;
+static const CGFloat POPBouncy3BouncinessNormalizedMax = 0.8;
+static const CGFloat POPBouncy3SpeedNormalizedMin = 0.5;
+static const CGFloat POPBouncy3SpeedNormalizedMax = 200;
+static const CGFloat POPBouncy3FrictionInterpolationMax = 0.01;
+
++ (void)convertBounciness:(CGFloat)bounciness speed:(CGFloat)speed toTension:(CGFloat *)outTension friction:(CGFloat *)outFriction mass:(CGFloat *)outMass
+{
+  double b = POPNormalize(bounciness / POPBouncy3NormalizationScale, 0, POPBouncy3NormalizationRange);
+  b = POPProjectNormal(b, POPBouncy3BouncinessNormalizedMin, POPBouncy3BouncinessNormalizedMax);
+
+  double s = POPNormalize(speed / POPBouncy3NormalizationScale, 0, POPBouncy3NormalizationRange);
+
+  CGFloat tension = POPProjectNormal(s, POPBouncy3SpeedNormalizedMin, POPBouncy3SpeedNormalizedMax);
+  CGFloat friction = POPQuadraticOutInterpolation(b, POPBouncy3NoBounce(tension), POPBouncy3FrictionInterpolationMax);
+
+  tension = POP_ANIMATION_TENSION_FOR_QC_TENSION(tension);
+  friction = POP_ANIMATION_FRICTION_FOR_QC_FRICTION(friction);
+
+  if (outTension) {
+    *outTension = tension;
+  }
+
+  if (outFriction) {
+    *outFriction = friction;
+  }
+
+  if (outMass) {
+    *outMass = 1.0;
+  }
+}
+
++ (void)convertTension:(CGFloat)tension friction:(CGFloat)friction toBounciness:(CGFloat *)outBounciness speed:(CGFloat *)outSpeed
+{
+  // Convert to QC values, in which our calculations are done.
+  CGFloat qcFriction = QC_FRICTION_FOR_POP_ANIMATION_FRICTION(friction);
+  CGFloat qcTension = QC_TENSION_FOR_POP_ANIMATION_TENSION(tension);
+
+  // Friction is a function of bounciness and tension, according to the following:
+  // friction = POPQuadraticOutInterpolation(b, POPBouncy3NoBounce(tension), POPBouncy3FrictionInterpolationMax);
+  // Solve for bounciness, given a tension and friction.
+
+  CGFloat nobounceTension = POPBouncy3NoBounce(qcTension);
+  CGFloat bounciness1, bounciness2;
+
+  POPQuadraticSolve((nobounceTension - POPBouncy3FrictionInterpolationMax),      // a
+                  2 * (POPBouncy3FrictionInterpolationMax - nobounceTension),  // b
+                  (nobounceTension - qcFriction),                             // c
+                  bounciness1,                                                // x1
+                  bounciness2);                                               // x2
+
+
+  // Choose the quadratic solution within the normalized bounciness range
+  CGFloat projectedNormalizedBounciness = (bounciness2 < POPBouncy3BouncinessNormalizedMax) ? bounciness2 : bounciness1;
+  CGFloat projectedNormalizedSpeed = qcTension;
+
+  // Reverse projection + normalization
+  CGFloat bounciness = ((POPBouncy3NormalizationRange * POPBouncy3NormalizationScale) / (POPBouncy3BouncinessNormalizedMax - POPBouncy3BouncinessNormalizedMin)) * (projectedNormalizedBounciness - POPBouncy3BouncinessNormalizedMin);
+  CGFloat speed = ((POPBouncy3NormalizationRange * POPBouncy3NormalizationScale) / (POPBouncy3SpeedNormalizedMax - POPBouncy3SpeedNormalizedMin)) * (projectedNormalizedSpeed - POPBouncy3SpeedNormalizedMin);
+
+  // Write back results
+  if (outBounciness) {
+    *outBounciness = bounciness;
+  }
+
+  if (outSpeed) {
+    *outSpeed = speed;
+  }
+}
+
+@end

pop/POPAnimationInternal.h

@@ -0,0 +1,506 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimation.h"
+
+#import <QuartzCore/CAMediaTimingFunction.h>
+
+#import "POPAction.h"
+#import "POPAnimationRuntime.h"
+#import "POPAnimationTracerInternal.h"
+#import "POPMath.h"
+#import "POPSpringSolver.h"
+
+using namespace POP;
+
+/**
+ Enumeration of supported animation types.
+ */
+enum POPAnimationType
+{
+  kPOPAnimationSpring,
+  kPOPAnimationDecay,
+  kPOPAnimationBasic,
+  kPOPAnimationCustom,
+};
+
+typedef struct
+{
+  CGFloat progress;
+  bool reached;
+} POPProgressMarker;
+
+typedef void (^POPAnimationDidStartBlock)(POPAnimation *anim);
+typedef void (^POPAnimationDidReachToValueBlock)(POPAnimation *anim);
+typedef void (^POPAnimationCompletionBlock)(POPAnimation *anim, BOOL finished);
+typedef void (^POPAnimationDidApplyBlock)(POPAnimation *anim);
+
+@interface POPAnimation()
+- (instancetype)_init;
+
+@property (assign, nonatomic) SpringSolver4d *solver;
+@property (readonly, nonatomic) POPAnimationType type;
+
+/**
+ The current animation value, updated while animation is progressing.
+ */
+@property (copy, nonatomic, readonly) id currentValue;
+
+/**
+ An array of optional progress markers. For each marker specified, the animation delegate will be informed when progress meets or exceeds the value specified. Specifying values outside of the [0, 1] range will give undefined results.
+ */
+@property (copy, nonatomic) NSArray *progressMarkers;
+
+/**
+ Return YES to indicate animation should continue animating.
+ */
+- (BOOL)_advance:(id)object currentTime:(CFTimeInterval)currentTime elapsedTime:(CFTimeInterval)elapsedTime;
+
+/**
+ Subclass override point to append animation description.
+ */
+- (void)_appendDescription:(NSMutableString *)s debug:(BOOL)debug;
+
+@end
+
+NS_INLINE NSString *describe(VectorConstRef vec)
+{
+  return NULL == vec ? @"null" : vec->toString();
+}
+
+NS_INLINE Vector4r vector4(VectorConstRef vec)
+{
+  return NULL == vec ? Vector4r::Zero() : vec->vector4r();
+}
+
+NS_INLINE Vector4d vector4d(VectorConstRef vec)
+{
+  if (NULL == vec) {
+    return Vector4d::Zero();
+  } else {
+    return vec->vector4r().cast<double>();
+  }
+}
+
+NS_INLINE bool vec_equal(VectorConstRef v1, VectorConstRef v2)
+{
+  if (v1 == v2) {
+    return true;
+  }
+  if (!v1 || !v2) {
+    return false;
+  }
+  return *v1 == *v2;
+}
+
+NS_INLINE CGFloat * vec_data(VectorRef vec)
+{
+  return NULL == vec ? NULL : vec->data();
+}
+
+template<class T>
+struct ComputeProgressFunctor {
+  CGFloat operator()(const T &value, const T &start, const T &end) const {
+    return 0;
+  }
+};
+
+template<>
+struct ComputeProgressFunctor<Vector4r> {
+  CGFloat operator()(const Vector4r &value, const Vector4r &start, const Vector4r &end) const {
+    CGFloat s = (value - start).squaredNorm(); // distance from start
+    CGFloat e = (value - end).squaredNorm();   // distance from end
+    CGFloat d = (end - start).squaredNorm();   // distance from start to end
+
+    if (0 == d) {
+      return 1;
+    } else if (s > e) {
+      // s -------- p ---- e   OR   s ------- e ---- p
+      return sqrtr(s/d);
+    } else {
+      // s --- p --------- e   OR   p ---- s ------- e
+      return 1 - sqrtr(e/d);
+    }
+  }
+};
+
+struct _POPAnimationState;
+struct _POPDecayAnimationState;
+struct _POPPropertyAnimationState;
+
+extern _POPAnimationState *POPAnimationGetState(POPAnimation *a);
+
+
+#define FB_FLAG_GET(stype, flag, getter) \
+- (BOOL)getter { \
+  return ((stype *)_state)->flag; \
+}
+
+#define FB_FLAG_SET(stype, flag, mutator) \
+- (void)mutator (BOOL)value { \
+  if (value == ((stype *)_state)->flag) \
+    return; \
+  ((stype *)_state)->flag = value; \
+}
+
+#define DEFINE_RW_FLAG(stype, flag, getter, mutator) \
+  FB_FLAG_GET (stype, flag, getter) \
+  FB_FLAG_SET (stype, flag, mutator)
+
+#define FB_PROPERTY_GET(stype, property, ctype) \
+- (ctype)property { \
+  return ((stype *)_state)->property; \
+}
+
+#define FB_PROPERTY_SET(stype, property, mutator, ctype, ...) \
+- (void)mutator (ctype)value { \
+  if (value == ((stype *)_state)->property) \
+    return; \
+  ((stype *)_state)->property = value; \
+  __VA_ARGS__ \
+}
+
+#define FB_PROPERTY_SET_OBJ_COPY(stype, property, mutator, ctype, ...) \
+- (void)mutator (ctype)value { \
+  if (value == ((stype *)_state)->property) \
+    return; \
+  ((stype *)_state)->property = [value copy]; \
+  __VA_ARGS__ \
+}
+
+#define DEFINE_RW_PROPERTY(stype, flag, mutator, ctype, ...) \
+  FB_PROPERTY_GET (stype, flag, ctype) \
+  FB_PROPERTY_SET (stype, flag, mutator, ctype, __VA_ARGS__)
+
+#define DEFINE_RW_PROPERTY_OBJ(stype, flag, mutator, ctype, ...) \
+  FB_PROPERTY_GET (stype, flag, ctype) \
+  FB_PROPERTY_SET (stype, flag, mutator, ctype, __VA_ARGS__)
+
+#define DEFINE_RW_PROPERTY_OBJ_COPY(stype, flag, mutator, ctype, ...) \
+  FB_PROPERTY_GET (stype, flag, ctype) \
+  FB_PROPERTY_SET_OBJ_COPY (stype, flag, mutator, ctype, __VA_ARGS__)
+
+
+/**
+ Internal delegate definition.
+ */
+@interface NSObject (POPAnimationDelegateInternal)
+- (void)pop_animation:(POPAnimation *)anim didReachProgress:(CGFloat)progress;
+@end
+
+struct _POPAnimationState
+{
+  id __unsafe_unretained self;
+  POPAnimationType type;
+  NSString *name;
+  NSUInteger ID;
+  CFTimeInterval beginTime;
+  CFTimeInterval startTime;
+  CFTimeInterval lastTime;
+  id __weak delegate;
+  POPAnimationDidStartBlock animationDidStartBlock;
+  POPAnimationDidReachToValueBlock animationDidReachToValueBlock;
+  POPAnimationCompletionBlock completionBlock;
+  POPAnimationDidApplyBlock animationDidApplyBlock;
+  NSMutableDictionary *dict;
+  POPAnimationTracer *tracer;
+  CGFloat progress;
+  NSInteger repeatCount;
+
+  bool active:1;
+  bool paused:1;
+  bool removedOnCompletion:1;
+
+  bool delegateDidStart:1;
+  bool delegateDidStop:1;
+  bool delegateDidProgress:1;
+  bool delegateDidApply:1;
+  bool delegateDidReachToValue:1;
+
+  bool additive:1;
+  bool didReachToValue:1;
+  bool tracing:1; // corresponds to tracer started
+  bool userSpecifiedDynamics:1;
+  bool autoreverses:1;
+  bool repeatForever:1;
+  bool customFinished:1;
+
+  _POPAnimationState(id __unsafe_unretained anim) :
+  self(anim),
+  type((POPAnimationType)0),
+  name(nil),
+  ID(0),
+  beginTime(0),
+  startTime(0),
+  lastTime(0),
+  delegate(nil),
+  animationDidStartBlock(nil),
+  animationDidReachToValueBlock(nil),
+  completionBlock(nil),
+  animationDidApplyBlock(nil),
+  dict(nil),
+  tracer(nil),
+  progress(0),
+  repeatCount(0),
+  active(false),
+  paused(true),
+  removedOnCompletion(true),
+  delegateDidStart(false),
+  delegateDidStop(false),
+  delegateDidProgress(false),
+  delegateDidApply(false),
+  delegateDidReachToValue(false),
+  additive(false),
+  didReachToValue(false),
+  tracing(false),
+  userSpecifiedDynamics(false),
+  autoreverses(false),
+  repeatForever(false),
+  customFinished(false) {}
+
+  virtual ~_POPAnimationState()
+  {
+    name = nil;
+    dict = nil;
+    tracer = nil;
+    animationDidStartBlock = NULL;
+    animationDidReachToValueBlock = NULL;
+    completionBlock = NULL;
+    animationDidApplyBlock = NULL;
+  }
+
+  bool isCustom() {
+    return kPOPAnimationCustom == type;
+  }
+
+  bool isStarted() {
+    return 0 != startTime;
+  }
+
+  id getDelegate() {
+    return delegate;
+  }
+
+  void setDelegate(id d) {
+    if (d != delegate) {
+      delegate = d;
+      delegateDidStart = [d respondsToSelector:@selector(pop_animationDidStart:)];
+      delegateDidStop = [d respondsToSelector:@selector(pop_animationDidStop:finished:)];
+      delegateDidProgress = [d respondsToSelector:@selector(pop_animation:didReachProgress:)];
+      delegateDidApply = [d respondsToSelector:@selector(pop_animationDidApply:)];
+      delegateDidReachToValue = [d respondsToSelector:@selector(pop_animationDidReachToValue:)];
+    }
+  }
+
+  bool getPaused() {
+    return paused;
+  }
+
+  void setPaused(bool f) {
+    if (f != paused) {
+      paused = f;
+      if (!paused) {
+        reset(false);
+      }
+    }
+  }
+
+  CGFloat getProgress() {
+    return progress;
+  }
+
+  /* returns true if started */
+  bool startIfNeeded(id obj, CFTimeInterval time, CFTimeInterval offset)
+  {
+    bool started = false;
+
+    // detect start based on time
+    if (0 == startTime && time >= beginTime + offset) {
+
+      // activate & unpause
+      active = true;
+      setPaused(false);
+
+      // note start time
+      startTime = lastTime = time;
+      started = true;
+    }
+
+    // ensure values for running animation
+    bool running = active && !paused;
+    if (running) {
+      willRun(started, obj);
+    }
+
+    // handle start
+    if (started) {
+      handleDidStart();
+    }
+
+    return started;
+  }
+
+  void stop(bool removing, bool done) {
+    if (active)
+    {
+      // delegate progress one last time
+      if (done) {
+        delegateProgress();
+      }
+
+      if (removing) {
+        active = false;
+      }
+
+      handleDidStop(done);
+    } else {
+
+      // stopped before even started
+      // delegate start and stop regardless; matches CA behavior
+      if (!isStarted()) {
+        handleDidStart();
+        handleDidStop(false);
+      }
+    }
+
+    setPaused(true);
+  }
+
+  virtual void handleDidStart()
+  {
+    if (delegateDidStart) {
+      ActionEnabler enabler;
+      [delegate pop_animationDidStart:self];
+    }
+
+    POPAnimationDidStartBlock block = animationDidStartBlock;
+    if (block != NULL) {
+      ActionEnabler enabler;
+      block(self);
+    }
+
+    if (tracing) {
+      [tracer didStart];
+    }
+  }
+
+  void handleDidStop(BOOL done)
+  {
+    if (delegateDidStop) {
+      ActionEnabler enabler;
+      [delegate pop_animationDidStop:self finished:done];
+    }
+
+    // add another strong reference to completion block before callout
+    POPAnimationCompletionBlock block = completionBlock;
+    if (block != NULL) {
+      ActionEnabler enabler;
+      block(self, done);
+    }
+
+    if (tracing) {
+      [tracer didStop:done];
+    }
+  }
+
+  /* virtual functions */
+  virtual bool isDone() {
+    if (isCustom()) {
+      return customFinished;
+    }
+
+    return false;
+  }
+
+  bool advanceTime(CFTimeInterval time, id obj) {
+    bool advanced = false;
+    bool computedProgress = false;
+    CFTimeInterval dt = time - lastTime;
+
+    switch (type) {
+      case kPOPAnimationSpring:
+        advanced = advance(time, dt, obj);
+        break;
+      case kPOPAnimationDecay:
+        advanced = advance(time, dt, obj);
+        break;
+      case kPOPAnimationBasic: {
+        advanced = advance(time, dt, obj);
+        computedProgress = true;
+        break;
+      }
+      case kPOPAnimationCustom: {
+        customFinished = [self _advance:obj currentTime:time elapsedTime:dt] ? false : true;
+        advanced = true;
+        break;
+      }
+      default:
+        break;
+    }
+
+    if (advanced) {
+
+      // estimate progress
+      if (!computedProgress) {
+        computeProgress();
+      }
+
+      // delegate progress
+      delegateProgress();
+
+      // update time
+      lastTime = time;
+    }
+
+    return advanced;
+  }
+
+  virtual void willRun(bool started, id obj) {}
+  virtual bool advance(CFTimeInterval time, CFTimeInterval dt, id obj) { return false; }
+  virtual void computeProgress() {}
+  virtual void delegateProgress() {}
+
+  virtual void delegateApply() {
+    if (delegateDidApply) {
+      ActionEnabler enabler;
+      [delegate pop_animationDidApply:self];
+    }
+
+    POPAnimationDidApplyBlock block = animationDidApplyBlock;
+    if (block != NULL) {
+      ActionEnabler enabler;
+      block(self);
+    }
+  }
+
+  virtual void reset(bool all) {
+    startTime = 0;
+    lastTime = 0;
+  }
+};
+
+typedef struct _POPAnimationState POPAnimationState;
+
+
+@interface POPAnimation ()
+{
+@protected
+  struct _POPAnimationState *_state;
+}
+
+@end
+
+// NSProxy extensions, for testing purposes
+@interface NSProxy (POP)
+- (void)pop_addAnimation:(POPAnimation *)anim forKey:(NSString *)key;
+- (void)pop_removeAllAnimations;
+- (void)pop_removeAnimationForKey:(NSString *)key;
+- (NSArray *)pop_animationKeys;
+- (POPAnimation *)pop_animationForKey:(NSString *)key;
+@end

pop/POPAnimationPrivate.h

@@ -0,0 +1,16 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <pop/POPAnimation.h>
+
+#define POP_ANIMATION_FRICTION_FOR_QC_FRICTION(qcFriction) (25.0 + (((qcFriction - 8.0) / 2.0) * (25.0 - 19.0)))
+#define POP_ANIMATION_TENSION_FOR_QC_TENSION(qcTension) (194.0 + (((qcTension - 30.0) / 50.0) * (375.0 - 194.0)))
+
+#define QC_FRICTION_FOR_POP_ANIMATION_FRICTION(fbFriction) (8.0 + 2.0 * ((fbFriction - 25.0)/(25.0 - 19.0)))
+#define QC_TENSION_FOR_POP_ANIMATION_TENSION(fbTension) (30.0 + 50.0 * ((fbTension - 194.0)/(375.0 - 194.0)))

pop/POPAnimationRuntime.h

@@ -0,0 +1,99 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <objc/runtime.h>
+
+#import <CoreGraphics/CoreGraphics.h>
+#import <Foundation/Foundation.h>
+
+#import "POPAnimatablePropertyTypes.h"
+#import "POPVector.h"
+
+enum POPValueType
+{
+  kPOPValueUnknown = 0,
+  kPOPValueInteger,
+  kPOPValueFloat,
+  kPOPValuePoint,
+  kPOPValueSize,
+  kPOPValueRect,
+  kPOPValueEdgeInsets,
+  kPOPValueAffineTransform,
+  kPOPValueTransform,
+  kPOPValueRange,
+  kPOPValueColor,
+  kPOPValueSCNVector3,
+  kPOPValueSCNVector4,
+};
+
+using namespace POP;
+
+/**
+ Returns value type based on objc type description, given list of supported value types and length.
+ */
+extern POPValueType POPSelectValueType(const char *objctype, const POPValueType *types, size_t length);
+
+/**
+ Returns value type based on objc object, given a list of supported value types and length.
+ */
+extern POPValueType POPSelectValueType(id obj, const POPValueType *types, size_t length);
+
+/**
+ Array of all value types.
+ */
+extern const POPValueType kPOPAnimatableAllTypes[12];
+
+/**
+ Array of all value types supported for animation.
+ */
+extern const POPValueType kPOPAnimatableSupportTypes[10];
+
+/**
+ Returns a string description of a value type.
+ */
+extern NSString *POPValueTypeToString(POPValueType t);
+
+/**
+ Returns a mutable dictionary of weak pointer keys to weak pointer values.
+ */
+extern CFMutableDictionaryRef POPDictionaryCreateMutableWeakPointerToWeakPointer(NSUInteger capacity) CF_RETURNS_RETAINED;
+
+/**
+ Returns a mutable dictionary of weak pointer keys to weak pointer values.
+ */
+extern CFMutableDictionaryRef POPDictionaryCreateMutableWeakPointerToStrongObject(NSUInteger capacity) CF_RETURNS_RETAINED;
+
+/**
+ Box a vector.
+ */
+extern id POPBox(VectorConstRef vec, POPValueType type, bool force = false);
+
+/**
+ Unbox a vector.
+ */
+extern VectorRef POPUnbox(id value, POPValueType &type, NSUInteger &count, bool validate);
+
+/**
+ Read object value and return a Vector4r.
+ */
+NS_INLINE Vector4r read_values(POPAnimatablePropertyReadBlock read, id obj, size_t count)
+{
+  Vector4r vec = Vector4r::Zero();
+  if (0 == count)
+    return vec;
+
+  read(obj, vec.data());
+
+  return vec;
+}
+
+NS_INLINE NSString *POPStringFromBOOL(BOOL value)
+{
+  return value ? @"YES" : @"NO";
+}

pop/POPAnimationRuntime.mm

@@ -0,0 +1,329 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimationRuntime.h"
+
+#import <objc/objc.h>
+
+#import <QuartzCore/QuartzCore.h>
+
+#if TARGET_OS_IPHONE
+#import <UIKit/UIKit.h>
+#endif
+
+#import "POPCGUtils.h"
+#import "POPDefines.h"
+#import "POPGeometry.h"
+#import "POPVector.h"
+
+static Boolean pointerEqual(const void *ptr1, const void *ptr2) {
+  return ptr1 == ptr2;
+}
+
+static CFHashCode pointerHash(const void *ptr) {
+  return (CFHashCode)(ptr);
+}
+
+CFMutableDictionaryRef POPDictionaryCreateMutableWeakPointerToWeakPointer(NSUInteger capacity)
+{
+  CFDictionaryKeyCallBacks kcb = kCFTypeDictionaryKeyCallBacks;
+
+  // weak, pointer keys
+  kcb.retain = NULL;
+  kcb.release = NULL;
+  kcb.equal = pointerEqual;
+  kcb.hash = pointerHash;
+
+  CFDictionaryValueCallBacks vcb = kCFTypeDictionaryValueCallBacks;
+
+  // weak, pointer values
+  vcb.retain = NULL;
+  vcb.release = NULL;
+  vcb.equal = pointerEqual;
+
+  return CFDictionaryCreateMutable(NULL, capacity, &kcb, &vcb);
+}
+
+CFMutableDictionaryRef POPDictionaryCreateMutableWeakPointerToStrongObject(NSUInteger capacity)
+{
+  CFDictionaryKeyCallBacks kcb = kCFTypeDictionaryKeyCallBacks;
+
+  // weak, pointer keys
+  kcb.retain = NULL;
+  kcb.release = NULL;
+  kcb.equal = pointerEqual;
+  kcb.hash = pointerHash;
+
+  // strong, object values
+  CFDictionaryValueCallBacks vcb = kCFTypeDictionaryValueCallBacks;
+
+  return CFDictionaryCreateMutable(NULL, capacity, &kcb, &vcb);
+}
+
+static bool FBCompareTypeEncoding(const char *objctype, POPValueType type)
+{
+  switch (type)
+  {
+    case kPOPValueFloat:
+      return (strcmp(objctype, @encode(float)) == 0
+              || strcmp(objctype, @encode(double)) == 0
+              );
+
+    case kPOPValuePoint:
+      return (strcmp(objctype, @encode(CGPoint)) == 0
+#if !TARGET_OS_IPHONE
+              || strcmp(objctype, @encode(NSPoint)) == 0
+#endif
+              );
+
+    case kPOPValueSize:
+      return (strcmp(objctype, @encode(CGSize)) == 0
+#if !TARGET_OS_IPHONE
+              || strcmp(objctype, @encode(NSSize)) == 0
+#endif
+              );
+
+    case kPOPValueRect:
+      return (strcmp(objctype, @encode(CGRect)) == 0
+#if !TARGET_OS_IPHONE
+              || strcmp(objctype, @encode(NSRect)) == 0
+#endif
+              );
+    case kPOPValueEdgeInsets:
+#if TARGET_OS_IPHONE
+      return strcmp(objctype, @encode(UIEdgeInsets)) == 0;
+#else
+      return false;
+#endif
+      
+    case kPOPValueAffineTransform:
+      return strcmp(objctype, @encode(CGAffineTransform)) == 0;
+
+    case kPOPValueTransform:
+      return strcmp(objctype, @encode(CATransform3D)) == 0;
+
+    case kPOPValueRange:
+      return strcmp(objctype, @encode(CFRange)) == 0
+      || strcmp(objctype, @encode (NSRange)) == 0;
+
+    case kPOPValueInteger:
+      return (strcmp(objctype, @encode(int)) == 0
+              || strcmp(objctype, @encode(unsigned int)) == 0
+              || strcmp(objctype, @encode(short)) == 0
+              || strcmp(objctype, @encode(unsigned short)) == 0
+              || strcmp(objctype, @encode(long)) == 0
+              || strcmp(objctype, @encode(unsigned long)) == 0
+              || strcmp(objctype, @encode(long long)) == 0
+              || strcmp(objctype, @encode(unsigned long long)) == 0
+              );
+      
+    case kPOPValueSCNVector3:
+#if SCENEKIT_SDK_AVAILABLE
+      return strcmp(objctype, @encode(SCNVector3)) == 0;
+#else
+      return false;
+#endif
+      
+    case kPOPValueSCNVector4:
+#if SCENEKIT_SDK_AVAILABLE
+      return strcmp(objctype, @encode(SCNVector4)) == 0;
+#else
+      return false;
+#endif
+      
+    default:
+      return false;
+  }
+}
+
+POPValueType POPSelectValueType(const char *objctype, const POPValueType *types, size_t length)
+{
+  if (NULL != objctype) {
+    for (size_t idx = 0; idx < length; idx++) {
+      if (FBCompareTypeEncoding(objctype, types[idx]))
+        return types[idx];
+    }
+  }
+  return kPOPValueUnknown;
+}
+
+POPValueType POPSelectValueType(id obj, const POPValueType *types, size_t length)
+{
+  if ([obj isKindOfClass:[NSValue class]]) {
+    return POPSelectValueType([obj objCType], types, length);
+  } else if (NULL != POPCGColorWithColor(obj)) {
+    return kPOPValueColor;
+  }
+  return kPOPValueUnknown;
+}
+
+const POPValueType kPOPAnimatableAllTypes[12] = {kPOPValueInteger, kPOPValueFloat, kPOPValuePoint, kPOPValueSize, kPOPValueRect, kPOPValueEdgeInsets, kPOPValueAffineTransform, kPOPValueTransform, kPOPValueRange, kPOPValueColor, kPOPValueSCNVector3, kPOPValueSCNVector4};
+
+const POPValueType kPOPAnimatableSupportTypes[10] = {kPOPValueInteger, kPOPValueFloat, kPOPValuePoint, kPOPValueSize, kPOPValueRect, kPOPValueEdgeInsets, kPOPValueColor, kPOPValueSCNVector3, kPOPValueSCNVector4};
+
+NSString *POPValueTypeToString(POPValueType t)
+{
+  switch (t) {
+    case kPOPValueUnknown:
+      return @"unknown";
+    case kPOPValueInteger:
+      return @"int";
+    case kPOPValueFloat:
+      return @"CGFloat";
+    case kPOPValuePoint:
+      return @"CGPoint";
+    case kPOPValueSize:
+      return @"CGSize";
+    case kPOPValueRect:
+      return @"CGRect";
+    case kPOPValueEdgeInsets:
+      return @"UIEdgeInsets";
+    case kPOPValueAffineTransform:
+      return @"CGAffineTransform";
+    case kPOPValueTransform:
+      return @"CATransform3D";
+    case kPOPValueRange:
+      return @"CFRange";
+    case kPOPValueColor:
+      return @"CGColorRef";
+    case kPOPValueSCNVector3:
+      return @"SCNVector3";
+    case kPOPValueSCNVector4:
+      return @"SCNVector4";
+    default:
+      return nil;
+  }
+}
+
+id POPBox(VectorConstRef vec, POPValueType type, bool force)
+{
+  if (NULL == vec)
+    return nil;
+  
+  switch (type) {
+    case kPOPValueInteger:
+    case kPOPValueFloat:
+      return @(vec->data()[0]);
+      break;
+    case kPOPValuePoint:
+      return [NSValue valueWithCGPoint:vec->cg_point()];
+      break;
+    case kPOPValueSize:
+      return [NSValue valueWithCGSize:vec->cg_size()];
+      break;
+    case kPOPValueRect:
+      return [NSValue valueWithCGRect:vec->cg_rect()];
+      break;
+#if TARGET_OS_IPHONE
+    case kPOPValueEdgeInsets:
+      return [NSValue valueWithUIEdgeInsets:vec->ui_edge_insets()];
+      break;
+#endif
+    case kPOPValueColor: {
+      return (__bridge_transfer id)vec->cg_color();
+      break;
+    }
+#if SCENEKIT_SDK_AVAILABLE
+    case kPOPValueSCNVector3: {
+      return [NSValue valueWithSCNVector3:vec->scn_vector3()];
+      break;
+    }
+    case kPOPValueSCNVector4: {
+      return [NSValue valueWithSCNVector4:vec->scn_vector4()];
+      break;
+    }
+#endif
+    default:
+      return force ? [NSValue valueWithCGPoint:vec->cg_point()] : nil;
+      break;
+  }
+}
+
+static VectorRef vectorize(id value, POPValueType type)
+{
+  Vector *vec = NULL;
+
+  switch (type) {
+    case kPOPValueInteger:
+    case kPOPValueFloat:
+#if CGFLOAT_IS_DOUBLE
+      vec = Vector::new_cg_float([value doubleValue]);
+#else
+      vec = Vector::new_cg_float([value floatValue]);
+#endif
+      break;
+    case kPOPValuePoint:
+      vec = Vector::new_cg_point([value CGPointValue]);
+      break;
+    case kPOPValueSize:
+      vec = Vector::new_cg_size([value CGSizeValue]);
+      break;
+    case kPOPValueRect:
+      vec = Vector::new_cg_rect([value CGRectValue]);
+      break;
+#if TARGET_OS_IPHONE
+    case kPOPValueEdgeInsets:
+      vec = Vector::new_ui_edge_insets([value UIEdgeInsetsValue]);
+      break;
+#endif
+    case kPOPValueAffineTransform:
+      vec = Vector::new_cg_affine_transform([value CGAffineTransformValue]);
+      break;
+    case kPOPValueColor:
+      vec = Vector::new_cg_color(POPCGColorWithColor(value));
+      break;
+#if SCENEKIT_SDK_AVAILABLE
+    case kPOPValueSCNVector3:
+      vec = Vector::new_scn_vector3([value SCNVector3Value]);
+      break;
+    case kPOPValueSCNVector4:
+      vec = Vector::new_scn_vector4([value SCNVector4Value]);
+      break;
+#endif
+    default:
+      break;
+  }
+  
+  return VectorRef(vec);
+}
+
+VectorRef POPUnbox(id value, POPValueType &animationType, NSUInteger &count, bool validate)
+{
+  if (nil == value) {
+    count = 0;
+    return VectorRef(NULL);
+  }
+
+  // determine type of value
+  POPValueType valueType = POPSelectValueType(value, kPOPAnimatableSupportTypes, POP_ARRAY_COUNT(kPOPAnimatableSupportTypes));
+
+  // handle unknown types
+  if (kPOPValueUnknown == valueType) {
+    NSString *valueDesc = [[value class] description];
+    [NSException raise:@"Unsuported value" format:@"Animating %@ values is not supported", valueDesc];
+  }
+
+  // vectorize
+  VectorRef vec = vectorize(value, valueType);
+
+  if (kPOPValueUnknown == animationType || 0 == count) {
+    // update animation type based on value type
+    animationType = valueType;
+    if (NULL != vec) {
+      count = vec->size();
+    }
+  } else if (validate) {
+    // allow for mismatched types, so long as vector size matches
+    if (count != vec->size()) {
+      [NSException raise:@"Invalid value" format:@"%@ should be of type %@", value, POPValueTypeToString(animationType)];
+    }
+  }
+  
+  return vec;
+}

pop/POPAnimationTracer.h

@@ -0,0 +1,60 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import <pop/POPAnimationEvent.h>
+
+@class POPAnimation;
+
+/**
+ @abstract Tracer of animation events to facilitate unit testing & debugging.
+ */
+@interface POPAnimationTracer : NSObject
+
+/**
+ @abstract Start recording events.
+ */
+- (void)start;
+
+/**
+ @abstract Stop recording events.
+ */
+- (void)stop;
+
+/**
+ @abstract Resets any recoded events. Continues recording events if already started.
+ */
+- (void)reset;
+
+/**
+ @abstract Property representing all recorded events.
+ @discussion Events are returned in order of occurrence.
+ */
+@property (nonatomic, assign, readonly) NSArray *allEvents;
+
+/**
+ @abstract Property representing all recorded write events for convenience.
+ @discussion Events are returned in order of occurrence.
+ */
+@property (nonatomic, assign, readonly) NSArray *writeEvents;
+
+/**
+ @abstract Queries for events of specified type.
+ @param type The type of event to return.
+ @returns An array of events of specified type in order of occurrence.
+ */
+- (NSArray *)eventsWithType:(POPAnimationEventType)type;
+
+/**
+ @abstract Property indicating whether tracer should automatically log events and reset collection on animation completion.
+ */
+@property (nonatomic, assign) BOOL shouldLogAndResetOnCompletion;
+
+@end

pop/POPAnimationTracer.mm

@@ -0,0 +1,192 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimationTracer.h"
+
+#import <QuartzCore/QuartzCore.h>
+
+#import "POPAnimationEventInternal.h"
+#import "POPAnimationInternal.h"
+#import "POPSpringAnimation.h"
+
+@implementation POPAnimationTracer
+{
+  __weak POPAnimation *_animation;
+  POPAnimationState *_animationState;
+  NSMutableArray *_events;
+  BOOL _animationHasVelocity;
+}
+@synthesize shouldLogAndResetOnCompletion = _shouldLogAndResetOnCompletion;
+
+static POPAnimationEvent *create_event(POPAnimationTracer *self, POPAnimationEventType type, id value = nil, bool recordAnimation = false)
+{
+  bool useLocalTime = 0 != self->_animationState->startTime;
+  CFTimeInterval time = useLocalTime
+    ? self->_animationState->lastTime - self->_animationState->startTime
+    : self->_animationState->lastTime;
+
+  POPAnimationEvent *event;
+  __strong POPAnimation* animation = self->_animation;
+
+  if (!value) {
+    event = [[POPAnimationEvent alloc] initWithType:type time:time];
+  } else {
+    event = [[POPAnimationValueEvent alloc] initWithType:type time:time value:value];
+    if (self->_animationHasVelocity) {
+      [(POPAnimationValueEvent *)event setVelocity:[(POPSpringAnimation *)animation velocity]];
+    }
+  }
+
+  if (recordAnimation) {
+    event.animationDescription = [animation description];
+  }
+
+  return event;
+}
+
+- (id)initWithAnimation:(POPAnimation *)anAnim
+{
+  self = [super init];
+  if (nil != self) {
+    _animation = anAnim;
+    _animationState = POPAnimationGetState(anAnim);
+    _events = [[NSMutableArray alloc] initWithCapacity:50];
+    _animationHasVelocity = [anAnim respondsToSelector:@selector(velocity)];
+  }
+  return self;
+}
+
+- (void)readPropertyValue:(id)aValue
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventPropertyRead, aValue);
+  [_events addObject:event];
+}
+
+- (void)writePropertyValue:(id)aValue
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventPropertyWrite, aValue);
+  [_events addObject:event];
+}
+
+- (void)updateToValue:(id)aValue
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventToValueUpdate, aValue);
+  [_events addObject:event];
+}
+
+- (void)updateFromValue:(id)aValue
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventFromValueUpdate, aValue);
+  [_events addObject:event];
+}
+
+- (void)updateVelocity:(id)aValue
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventVelocityUpdate, aValue);
+  [_events addObject:event];
+}
+
+- (void)updateSpeed:(float)aFloat
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventSpeedUpdate, @(aFloat));
+  [_events addObject:event];
+}
+
+- (void)updateBounciness:(float)aFloat
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventBouncinessUpdate, @(aFloat));
+  [_events addObject:event];
+}
+
+- (void)updateFriction:(float)aFloat
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventFrictionUpdate, @(aFloat));
+  [_events addObject:event];
+}
+
+- (void)updateMass:(float)aFloat
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventMassUpdate, @(aFloat));
+  [_events addObject:event];
+}
+
+- (void)updateTension:(float)aFloat
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventTensionUpdate, @(aFloat));
+  [_events addObject:event];
+}
+
+- (void)didStart
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventDidStart, nil, true);
+  [_events addObject:event];
+}
+
+- (void)didStop:(BOOL)finished
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventDidStop, @(finished), true);
+  [_events addObject:event];
+
+  if (_shouldLogAndResetOnCompletion) {
+    NSLog(@"events:%@", self.allEvents);
+    [self reset];
+  }
+}
+
+- (void)didReachToValue:(id)aValue
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventDidReachToValue, aValue);
+  [_events addObject:event];
+}
+
+- (void)autoreversed
+{
+  POPAnimationEvent *event = create_event(self, kPOPAnimationEventAutoreversed);
+  [_events addObject:event];
+}
+
+- (void)start
+{
+  POPAnimationState *s = POPAnimationGetState(_animation);
+  s->tracing = true;
+}
+
+- (void)stop
+{
+  POPAnimationState *s = POPAnimationGetState(_animation);
+  s->tracing = false;
+}
+
+- (void)reset
+{
+  [_events removeAllObjects];
+}
+
+- (NSArray *)allEvents
+{
+  return [_events copy];
+}
+
+- (NSArray *)writeEvents
+{
+  return [self eventsWithType:kPOPAnimationEventPropertyWrite];
+}
+
+- (NSArray *)eventsWithType:(POPAnimationEventType)aType
+{
+  NSMutableArray *array = [NSMutableArray array];
+  for (POPAnimationEvent *event in _events) {
+    if (aType == event.type) {
+      [array addObject:event];
+    }
+  }
+  return array;
+}
+
+@end

pop/POPAnimationTracerInternal.h

@@ -0,0 +1,96 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import <pop/POPAnimationTracer.h>
+
+@interface POPAnimationTracer (Internal)
+
+/**
+ @abstract Designated initializer. Pass the animation being traced.
+ */
+- (instancetype)initWithAnimation:(POPAnimation *)anAnim;
+
+/**
+ @abstract Records read value.
+ */
+- (void)readPropertyValue:(id)aValue;
+
+/**
+ @abstract Records write value.
+ */
+- (void)writePropertyValue:(id)aValue;
+
+/**
+ Records to value update.
+ */
+- (void)updateToValue:(id)aValue;
+
+/**
+ @abstract Records from value update.
+ */
+- (void)updateFromValue:(id)aValue;
+
+/**
+ @abstract Records from value update.
+ */
+- (void)updateVelocity:(id)aValue;
+
+/**
+ @abstract Records bounciness update.
+ */
+- (void)updateBounciness:(float)aFloat;
+
+/**
+ @abstract Records speed update.
+ */
+- (void)updateSpeed:(float)aFloat;
+
+/**
+ @abstract Records friction update.
+ */
+- (void)updateFriction:(float)aFloat;
+
+/**
+ @abstract Records mass update.
+ */
+- (void)updateMass:(float)aFloat;
+
+/**
+ @abstract Records tension update.
+ */
+- (void)updateTension:(float)aFloat;
+
+/**
+ @abstract Records did add.
+ */
+- (void)didAdd;
+
+/**
+ @abstract Records did start.
+ */
+- (void)didStart;
+
+/**
+ @abstract Records did stop.
+ */
+- (void)didStop:(BOOL)finished;
+
+/**
+ @abstract Records did reach to value.
+ */
+- (void)didReachToValue:(id)aValue;
+
+/**
+ @abstract Records when an autoreverse animation takes place.
+ */
+- (void)autoreversed;
+
+@end

pop/POPAnimator.h

@@ -0,0 +1,59 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+@protocol POPAnimatorDelegate;
+
+/**
+ @abstract The animator class renders animations.
+ */
+@interface POPAnimator : NSObject
+
+/**
+ @abstract The shared animator instance.
+ @discussion Consumers should generally use the shared instance in lieu of creating new instances.
+ */
++ (instancetype)sharedAnimator;
+
+#if !TARGET_OS_IPHONE
+/**
+ @abstract Allows to select display to bind. Returns nil if failed to create the display link.
+ */
+- (instancetype)initWithDisplayID:(CGDirectDisplayID)displayID;
+#endif
+
+/**
+ @abstract The optional animator delegate.
+ */
+@property (weak, nonatomic) id<POPAnimatorDelegate> delegate;
+
+/**
+ @abstract Retrieves the nominal refresh period of a display link. Returns zero if unavailable.
+ */
+@property (readonly, nonatomic) CFTimeInterval refreshPeriod;
+
+@end
+
+/**
+ @abstract The animator delegate.
+ */
+@protocol POPAnimatorDelegate <NSObject>
+
+/**
+ @abstract Called on each frame before animation application.
+ */
+- (void)animatorWillAnimate:(POPAnimator *)animator;
+
+/**
+ @abstract Called on each frame after animation application.
+ */
+- (void)animatorDidAnimate:(POPAnimator *)animator;
+
+@end

pop/POPAnimator.mm

@@ -0,0 +1,909 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimator.h"
+#import "POPAnimatorPrivate.h"
+
+#import <list>
+#import <vector>
+
+#if !TARGET_OS_IPHONE
+#import <libkern/OSAtomic.h>
+#endif
+
+#import <objc/objc-auto.h>
+
+#import <QuartzCore/QuartzCore.h>
+
+#import "POPAnimation.h"
+#import "POPAnimationExtras.h"
+#import "POPBasicAnimationInternal.h"
+#import "POPDecayAnimation.h"
+
+using namespace std;
+using namespace POP;
+
+#define ENABLE_LOGGING_DEBUG 0
+#define ENABLE_LOGGING_INFO 0
+
+#if ENABLE_LOGGING_DEBUG
+#define FBLogAnimDebug NSLog
+#else
+#define FBLogAnimDebug(...)
+#endif
+
+#if ENABLE_LOGGING_INFO
+#define FBLogAnimInfo NSLog
+#else
+#define FBLogAnimInfo(...)
+#endif
+
+#if !TARGET_OS_IPHONE
+static const uint64_t kDisplayTimerFrequency = 60ull; // Hz
+#endif
+
+class POPAnimatorItem
+{
+public:
+  id __weak object;
+  NSString *key;
+  POPAnimation *animation;
+  NSInteger refCount;
+  id __unsafe_unretained unretainedObject;
+
+  POPAnimatorItem(id o, NSString *k, POPAnimation *a) POP_NOTHROW
+  {
+    object = o;
+    key = [k copy];
+    animation = a;
+    refCount = 1;
+    unretainedObject = o;
+  }
+
+  ~POPAnimatorItem()
+  {
+  }
+
+  bool operator==(const POPAnimatorItem& o) const {
+    return unretainedObject == o.unretainedObject && animation == o.animation && [key isEqualToString:o.key];
+  }
+
+};
+
+typedef std::shared_ptr<POPAnimatorItem> POPAnimatorItemRef;
+typedef std::shared_ptr<const POPAnimatorItem> POPAnimatorItemConstRef;
+
+typedef std::list<POPAnimatorItemRef> POPAnimatorItemList;
+typedef POPAnimatorItemList::iterator POPAnimatorItemListIterator;
+typedef POPAnimatorItemList::const_iterator POPAnimatorItemListConstIterator;
+
+#if !TARGET_OS_IPHONE
+static BOOL _disableBackgroundThread = YES;
+static uint64_t _displayTimerFrequency = kDisplayTimerFrequency;
+#endif
+
+@interface POPAnimator ()
+{
+#if TARGET_OS_IPHONE
+  CADisplayLink *_displayLink;
+#else
+  CVDisplayLinkRef _displayLink;
+  dispatch_source_t _displayTimer;
+  BOOL _displayTimerRunning;
+  int32_t _enqueuedRender;
+#endif
+  POPAnimatorItemList _list;
+  CFMutableDictionaryRef _dict;
+  NSMutableArray *_observers;
+  POPAnimatorItemList _pendingList;
+  CFRunLoopObserverRef _pendingListObserver;
+  CFTimeInterval _slowMotionStartTime;
+  CFTimeInterval _slowMotionLastTime;
+  CFTimeInterval _slowMotionAccumulator;
+  CFTimeInterval _beginTime;
+  pthread_mutex_t _lock;
+  BOOL _disableDisplayLink;
+}
+@end
+
+@implementation POPAnimator
+@synthesize delegate = _delegate;
+@synthesize disableDisplayLink = _disableDisplayLink;
+@synthesize beginTime = _beginTime;
+
+#if !TARGET_OS_IPHONE
+static CVReturn displayLinkCallback(CVDisplayLinkRef displayLink, const CVTimeStamp *now, const CVTimeStamp *outputTime, CVOptionFlags flagsIn, CVOptionFlags *flagsOut, void *context)
+{
+  if (_disableBackgroundThread) {
+    __unsafe_unretained POPAnimator *pa = (__bridge POPAnimator *)context;
+    int32_t* enqueuedRender = &pa->_enqueuedRender;
+    if (*enqueuedRender == 0) {
+      OSAtomicIncrement32(enqueuedRender);
+      dispatch_async(dispatch_get_main_queue(), ^{
+        [(__bridge POPAnimator*)context render];
+        OSAtomicDecrement32(enqueuedRender);
+      });
+    }
+  } else {
+    [(__bridge POPAnimator*)context render];
+  }
+  return kCVReturnSuccess;
+}
+#endif
+
+// call while holding lock
+static void updateDisplayLink(POPAnimator *self)
+{
+  BOOL paused = (0 == self->_observers.count && self->_list.empty()) || self->_disableDisplayLink;
+
+#if TARGET_OS_IPHONE
+  if (paused != self->_displayLink.paused) {
+    FBLogAnimInfo(paused ? @"pausing display link" : @"unpausing display link");
+    self->_displayLink.paused = paused;
+  }
+#else
+  if (NULL != self->_displayLink) {
+    if (paused == CVDisplayLinkIsRunning(self->_displayLink)) {
+      FBLogAnimInfo(paused ? @"pausing display link" : @"unpausing display link");
+      if (paused) {
+        CVDisplayLinkStop(self->_displayLink);
+      } else {
+        CVDisplayLinkStart(self->_displayLink);
+      }
+    }
+  } else {
+    if (paused == self->_displayTimerRunning) {
+      FBLogAnimInfo(paused ? @"pausing display timer" : @"unpausing display timer");
+      if (paused) {
+        self->_displayTimerRunning = NO;
+        dispatch_suspend(self->_displayTimer);
+      } else {
+        self->_displayTimerRunning = YES;
+        dispatch_resume(self->_displayTimer);
+      }
+    }
+  }
+#endif
+}
+
+static void updateAnimatable(id obj, POPPropertyAnimationState *anim, bool shouldAvoidExtraneousWrite = false)
+{
+  // handle user-initiated stop or pause; halt animation
+  if (!anim->active || anim->paused)
+    return;
+
+  if (anim->hasValue()) {
+    POPAnimatablePropertyWriteBlock write = anim->property.writeBlock;
+    if (NULL == write)
+      return;
+
+    // current animation value
+    VectorRef currentVec = anim->currentValue();
+
+    if (!anim->additive) {
+
+      // if avoiding extraneous writes and we have a read block defined
+      if (shouldAvoidExtraneousWrite) {
+
+        POPAnimatablePropertyReadBlock read = anim->property.readBlock;
+        if (read) {
+          // compare current animation value with object value
+          Vector4r currentValue = currentVec->vector4r();
+          Vector4r objectValue = read_values(read, obj, anim->valueCount);
+          if (objectValue == currentValue) {
+            return;
+          }
+        }
+      }
+      
+      // update previous values; support animation convergence
+      anim->previous2Vec = anim->previousVec;
+      anim->previousVec = currentVec;
+
+      // write value
+      write(obj, currentVec->data());
+      if (anim->tracing) {
+        [anim->tracer writePropertyValue:POPBox(currentVec, anim->valueType, true)];
+      }
+    } else {
+      POPAnimatablePropertyReadBlock read = anim->property.readBlock;
+      NSCAssert(read, @"additive requires an animatable property readBlock");
+      if (NULL == read) {
+        return;
+      }
+
+      // object value
+      Vector4r objectValue = read_values(read, obj, anim->valueCount);
+
+      // current value
+      Vector4r currentValue = currentVec->vector4r();
+      
+      // determine animation change
+      if (anim->previousVec) {
+        Vector4r previousValue = anim->previousVec->vector4r();
+        currentValue -= previousValue;
+      }
+
+      // avoid writing no change
+      if (shouldAvoidExtraneousWrite && currentValue == Vector4r::Zero()) {
+        return;
+      }
+      
+      // add to object value
+      currentValue += objectValue;
+      
+      // update previous values; support animation convergence
+      anim->previous2Vec = anim->previousVec;
+      anim->previousVec = currentVec;
+      
+      // write value
+      write(obj, currentValue.data());
+      if (anim->tracing) {
+        [anim->tracer writePropertyValue:POPBox(currentVec, anim->valueType, true)];
+      }
+    }
+  }
+}
+
+static void applyAnimationTime(id obj, POPAnimationState *state, CFTimeInterval time)
+{
+  if (!state->advanceTime(time, obj)) {
+    return;
+  }
+  
+  POPPropertyAnimationState *ps = dynamic_cast<POPPropertyAnimationState*>(state);
+  if (NULL != ps) {
+    updateAnimatable(obj, ps);
+  }
+  
+  state->delegateApply();
+}
+
+static void applyAnimationToValue(id obj, POPAnimationState *state)
+{
+  POPPropertyAnimationState *ps = dynamic_cast<POPPropertyAnimationState*>(state);
+
+  if (NULL != ps) {
+    
+    // finalize progress
+    ps->finalizeProgress();
+    
+    // write to value, updating only if needed
+    updateAnimatable(obj, ps, true);
+  }
+  
+  state->delegateApply();
+}
+
+static POPAnimation *deleteDictEntry(POPAnimator *self, id __unsafe_unretained obj, NSString *key, BOOL cleanup = YES)
+{
+  POPAnimation *anim = nil;
+
+  // lock
+  pthread_mutex_lock(&self->_lock);
+
+  NSMutableDictionary *keyAnimationsDict = (__bridge id)CFDictionaryGetValue(self->_dict, (__bridge void *)obj);
+  if (keyAnimationsDict) {
+
+    anim = keyAnimationsDict[key];
+    if (anim) {
+
+      // remove key
+      [keyAnimationsDict removeObjectForKey:key];
+
+      // cleanup empty dictionaries
+      if (cleanup && 0 == keyAnimationsDict.count) {
+        CFDictionaryRemoveValue(self->_dict, (__bridge void *)obj);
+      }
+    }
+  }
+
+  // unlock
+  pthread_mutex_unlock(&self->_lock);
+  return anim;
+}
+
+static void stopAndCleanup(POPAnimator *self, POPAnimatorItemRef item, bool shouldRemove, bool finished)
+{
+  // remove
+  if (shouldRemove) {
+    deleteDictEntry(self, item->unretainedObject, item->key);
+  }
+
+  // stop
+  POPAnimationState *state = POPAnimationGetState(item->animation);
+  state->stop(shouldRemove, finished);
+
+  if (shouldRemove) {
+    // lock
+    pthread_mutex_lock(&self->_lock);
+
+    // find item in list
+    // may have already been removed on animationDidStop:
+    POPAnimatorItemListIterator find_iter = find(self->_list.begin(), self->_list.end(), item);
+    BOOL found = find_iter != self->_list.end();
+
+    if (found) {
+      self->_list.erase(find_iter);
+    }
+
+    // unlock
+    pthread_mutex_unlock(&self->_lock);
+  }
+}
+
++ (id)sharedAnimator
+{
+  static POPAnimator* _animator = nil;
+  static dispatch_once_t onceToken;
+  dispatch_once(&onceToken, ^{
+    _animator = [[POPAnimator alloc] init];
+  });
+  return _animator;
+}
+
+#if !TARGET_OS_IPHONE
++ (BOOL)disableBackgroundThread
+{
+  return _disableBackgroundThread;
+}
+
++ (void)setDisableBackgroundThread:(BOOL)flag
+{
+  _disableBackgroundThread = flag;
+}
+
++ (uint64_t)displayTimerFrequency
+{
+  return _displayTimerFrequency;
+}
+
++ (void)setDisplayTimerFrequency:(uint64_t)frequency
+{
+  _displayTimerFrequency = frequency;
+}
+#endif
+
+#pragma mark - Lifecycle
+
+- (instancetype)init
+{
+  self = [super init];
+  if (nil == self) return nil;
+
+#if TARGET_OS_IPHONE
+  _displayLink = [CADisplayLink displayLinkWithTarget:self selector:@selector(render)];
+  _displayLink.paused = YES;
+  [_displayLink addToRunLoop:[NSRunLoop mainRunLoop] forMode:NSRunLoopCommonModes];
+#else
+  CVReturn ret = CVDisplayLinkCreateWithActiveCGDisplays(&_displayLink);
+  if (kCVReturnSuccess != ret) {
+    ret = CVDisplayLinkCreateWithCGDisplay(CGMainDisplayID(), &_displayLink);
+  }
+  if (kCVReturnSuccess == ret) {
+    CVDisplayLinkSetOutputCallback(_displayLink, displayLinkCallback, (__bridge void *)self);
+  } else {
+    FBLogAnimInfo(@"cannot create display link: ret=%ld, falling back to display timer at %llu Hz", (long)ret, _displayTimerFrequency);
+    // Thanks to Apple, on older OSes DISPATCH_TIMER_STRICT is not supported and dispatch_source_create failed if we use it.
+    unsigned long mask = (NSFoundationVersionNumber >= NSFoundationVersionNumber10_9) ? DISPATCH_TIMER_STRICT : 0;
+    _displayTimer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, mask, dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0));
+    NSAssert(nil != _displayTimer, @"Cannot create display timer");
+    dispatch_source_set_timer(_displayTimer, DISPATCH_TIME_NOW, NSEC_PER_SEC / _displayTimerFrequency, 0);
+    __weak POPAnimator *weakSelf = self;
+    dispatch_source_set_event_handler(_displayTimer, ^{
+      __strong POPAnimator *strongSelf = weakSelf;
+      if (__builtin_expect(nil != strongSelf, 1)) {
+        (void) displayLinkCallback(NULL, NULL, NULL, 0, NULL, (__bridge void *)strongSelf);
+      }
+    });
+  }
+#endif
+
+  _dict = POPDictionaryCreateMutableWeakPointerToStrongObject(5);
+  pthread_mutex_init(&_lock, NULL);
+
+  return self;
+}
+
+#if !TARGET_OS_IPHONE
+- (instancetype)initWithDisplayID:(CGDirectDisplayID)displayID
+{
+  if (kCGNullDirectDisplay == displayID) {
+    return [self init];
+  }
+  
+  self = [super init];
+  if (nil == self) return nil;
+  
+  CVReturn ret = CVDisplayLinkCreateWithCGDisplay(displayID, &_displayLink);
+  if (kCVReturnSuccess != ret) {
+    return nil;
+  }
+  CVDisplayLinkSetOutputCallback(_displayLink, displayLinkCallback, (__bridge void *)self);
+  
+  _dict = POPDictionaryCreateMutableWeakPointerToStrongObject(5);
+  pthread_mutex_init(&_lock, NULL);
+  
+  return self;
+}
+#endif
+
+- (void)dealloc
+{
+#if TARGET_OS_IPHONE
+  [_displayLink invalidate];
+#else
+  if (_displayLink != NULL) {
+    CVDisplayLinkStop(_displayLink);
+    CVDisplayLinkRelease(_displayLink);
+  }
+  if (_displayTimer != NULL) {
+    dispatch_source_cancel(_displayTimer);
+#if !OS_OBJECT_USE_OBJC
+    dispatch_release(_displayTimer);
+#endif
+    _displayTimer = NULL;
+  }
+#endif
+  [self _clearPendingListObserver];
+  
+  pthread_mutex_destroy(&_lock);
+}
+
+#pragma mark - Utility
+
+- (void)_processPendingList
+{
+  // rendering pending animations
+  CFTimeInterval time = [self _currentRenderTime];
+  [self _renderTime:(0 != _beginTime) ? _beginTime : time items:_pendingList];
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  // clear list and observer
+  _pendingList.clear();
+  [self _clearPendingListObserver];
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+}
+
+- (void)_clearPendingListObserver
+{
+  if (_pendingListObserver) {
+    CFRunLoopRemoveObserver(CFRunLoopGetMain(), _pendingListObserver, kCFRunLoopCommonModes);
+    CFRelease(_pendingListObserver);
+    _pendingListObserver = NULL;
+  }
+}
+
+- (void)_scheduleProcessPendingList
+{
+  // see WebKit for magic numbers, eg http://trac.webkit.org/changeset/166540
+  static const CFIndex CATransactionCommitRunLoopOrder = 2000000;
+  static const CFIndex POPAnimationApplyRunLoopOrder = CATransactionCommitRunLoopOrder - 1;
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  if (!_pendingListObserver) {
+    __weak POPAnimator *weakSelf = self;
+
+    _pendingListObserver = CFRunLoopObserverCreateWithHandler(kCFAllocatorDefault, kCFRunLoopBeforeWaiting | kCFRunLoopExit, false, POPAnimationApplyRunLoopOrder, ^(CFRunLoopObserverRef observer, CFRunLoopActivity activity) {
+      [weakSelf _processPendingList];
+    });
+
+    if (_pendingListObserver) {
+      CFRunLoopAddObserver(CFRunLoopGetMain(), _pendingListObserver,  kCFRunLoopCommonModes);
+    }
+  }
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+}
+
+- (void)_renderTime:(CFTimeInterval)time items:(std::list<POPAnimatorItemRef>)items
+{
+  // begin transaction with actions disabled
+  [CATransaction begin];
+  [CATransaction setDisableActions:YES];
+
+  // notify delegate
+  __strong __typeof__(_delegate) delegate = _delegate;
+  [delegate animatorWillAnimate:self];
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  // count active animations
+  const NSUInteger count = items.size();
+  if (0 == count) {
+    // unlock
+    pthread_mutex_unlock(&_lock);
+  } else {
+    // copy list into vector
+    std::vector<POPAnimatorItemRef> vector{ items.begin(), items.end() };
+
+    // unlock
+    pthread_mutex_unlock(&_lock);
+
+    for (auto item : vector) {
+      [self _renderTime:time item:item];
+    }
+  }
+
+  // notify observers
+  for (id observer in self.observers) {
+    [observer animatorDidAnimate:(id)self];
+  }
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  // update display link
+  updateDisplayLink(self);
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+
+  // notify delegate and commit
+  [delegate animatorDidAnimate:self];
+  [CATransaction commit];
+}
+
+- (void)_renderTime:(CFTimeInterval)time item:(POPAnimatorItemRef)item
+{
+  id obj = item->object;
+  POPAnimation *anim = item->animation;
+  POPAnimationState *state = POPAnimationGetState(anim);
+
+  if (nil == obj) {
+    // object exists not; stop animating
+    NSAssert(item->unretainedObject, @"object should exist");
+    stopAndCleanup(self, item, true, false);
+  } else {
+
+    // start if needed
+    state->startIfNeeded(obj, time, _slowMotionAccumulator);
+
+    // only run active, not paused animations
+    if (state->active && !state->paused) {
+      // object exists; animate
+      applyAnimationTime(obj, state, time);
+
+      FBLogAnimDebug(@"time:%f running:%@", time, item->animation);
+      if (state->isDone()) {
+        // set end value
+        applyAnimationToValue(obj, state);
+
+        state->repeatCount--;
+        if (state->repeatForever || state->repeatCount > 0) {
+          if ([anim isKindOfClass:[POPPropertyAnimation class]]) {
+            POPPropertyAnimation *propAnim = (POPPropertyAnimation *)anim;
+            id oldFromValue = propAnim.fromValue;
+            propAnim.fromValue = propAnim.toValue;
+
+            if (state->autoreverses) {
+              if (state->tracing) {
+                [state->tracer autoreversed];
+              }
+
+              if (state->type == kPOPAnimationDecay) {
+                POPDecayAnimation *decayAnimation = (POPDecayAnimation *)propAnim;
+                decayAnimation.velocity = [decayAnimation reversedVelocity];
+              } else {
+                propAnim.toValue = oldFromValue;
+              }
+            } else {
+              if (state->type == kPOPAnimationDecay) {
+                POPDecayAnimation *decayAnimation = (POPDecayAnimation *)propAnim;
+                id originalVelocity = decayAnimation.originalVelocity;
+                decayAnimation.velocity = originalVelocity;
+              } else {
+                propAnim.fromValue = oldFromValue;
+              }
+            }
+          }
+
+          state->stop(NO, NO);
+          state->reset(true);
+
+          state->startIfNeeded(obj, time, _slowMotionAccumulator);
+        } else {
+          stopAndCleanup(self, item, state->removedOnCompletion, YES);
+        }
+      }
+    }
+  }
+}
+
+#pragma mark - API
+
+- (NSArray *)observers
+{
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  // get observers
+  NSArray *observers = 0 != _observers.count ? [_observers copy] : nil;
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+  return observers;
+}
+
+- (void)addAnimation:(POPAnimation *)anim forObject:(id)obj key:(NSString *)key
+{
+  if (!anim || !obj) {
+    return;
+  }
+
+  // support arbitrarily many nil keys
+  if (!key) {
+    key = [[NSUUID UUID] UUIDString];
+  }
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  // get key, animation dict associated with object
+  NSMutableDictionary *keyAnimationDict = (__bridge id)CFDictionaryGetValue(_dict, (__bridge void *)obj);
+
+  // update associated animation state
+  if (nil == keyAnimationDict) {
+    keyAnimationDict = [NSMutableDictionary dictionary];
+    CFDictionarySetValue(_dict, (__bridge void *)obj, (__bridge void *)keyAnimationDict);
+  } else {
+    // if the animation instance already exists, avoid cancelling only to restart
+    POPAnimation *existingAnim = keyAnimationDict[key];
+    if (existingAnim) {
+      // unlock
+      pthread_mutex_unlock(&_lock);
+
+      if (existingAnim == anim) {
+        return;
+      }
+      [self removeAnimationForObject:obj key:key cleanupDict:NO];
+        
+      // lock
+      pthread_mutex_lock(&_lock);
+    }
+  }
+  keyAnimationDict[key] = anim;
+
+  // create entry after potential removal
+  POPAnimatorItemRef item(new POPAnimatorItem(obj, key, anim));
+
+  // add to list and pending list
+  _list.push_back(item);
+  _pendingList.push_back(item);
+
+  // support animation re-use, reset all animation state
+  POPAnimationGetState(anim)->reset(true);
+
+  // update display link
+  updateDisplayLink(self);
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+
+  // schedule runloop processing of pending animations
+  [self _scheduleProcessPendingList];
+}
+
+- (void)removeAllAnimationsForObject:(id)obj
+{
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  NSArray *animations = [(__bridge id)CFDictionaryGetValue(_dict, (__bridge void *)obj) allValues];
+  CFDictionaryRemoveValue(_dict, (__bridge void *)obj);
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+
+  if (0 == animations.count) {
+    return;
+  }
+
+  NSHashTable *animationSet = [[NSHashTable alloc] initWithOptions:NSHashTableObjectPointerPersonality capacity:animations.count];
+  for (id animation in animations) {
+    [animationSet addObject:animation];
+  }
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  POPAnimatorItemRef item;
+  for (auto iter = _list.begin(); iter != _list.end();) {
+    item = *iter;
+    if(![animationSet containsObject:item->animation]) {
+      iter++;
+    } else {
+      iter = _list.erase(iter);
+    }
+  }
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+
+  for (POPAnimation *anim in animations) {
+    POPAnimationState *state = POPAnimationGetState(anim);
+    state->stop(true, !state->active);
+  }
+}
+
+- (void)removeAnimationForObject:(id)obj key:(NSString *)key cleanupDict:(BOOL)cleanupDict
+{
+  POPAnimation *anim = deleteDictEntry(self, obj, key, cleanupDict);
+  if (nil == anim) {
+    return;
+  }
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  // remove from list
+  POPAnimatorItemRef item;
+  for (auto iter = _list.begin(); iter != _list.end();) {
+    item = *iter;
+    if(anim == item->animation) {
+      _list.erase(iter);
+      break;
+    } else {
+      iter++;
+    }
+  }
+
+  // remove from pending list
+  for (auto iter = _pendingList.begin(); iter != _pendingList.end();) {
+    item = *iter;
+    if(anim == item->animation) {
+      _pendingList.erase(iter);
+      break;
+    } else {
+      iter++;
+    }
+  }
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+
+  // stop animation and callout
+  POPAnimationState *state = POPAnimationGetState(anim);
+  state->stop(true, (!state->active && !state->paused));
+}
+
+- (void)removeAnimationForObject:(id)obj key:(NSString *)key
+{
+  [self removeAnimationForObject:obj key:key cleanupDict:YES];
+}
+
+- (NSArray *)animationKeysForObject:(id)obj
+{
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  // get keys
+  NSArray *keys = [(__bridge NSDictionary *)CFDictionaryGetValue(_dict, (__bridge void *)obj) allKeys];
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+  return keys;
+}
+
+- (id)animationForObject:(id)obj key:(NSString *)key
+{
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  // lookup animation
+  NSDictionary *keyAnimationsDict = (__bridge id)CFDictionaryGetValue(_dict, (__bridge void *)obj);
+  POPAnimation *animation = keyAnimationsDict[key];
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+  return animation;
+}
+
+- (CFTimeInterval)refreshPeriod
+{
+#if TARGET_OS_IPHONE
+  return self->_displayLink.duration;
+#else
+  if (NULL != self->_displayLink) {
+    CVTime period = CVDisplayLinkGetNominalOutputVideoRefreshPeriod(self->_displayLink);
+    if (period.flags & kCVTimeIsIndefinite) {
+      return 0;
+    }
+    return ((CFTimeInterval)period.timeValue / (CFTimeInterval)period.timeScale);
+  }
+  return (1.0 / (CFTimeInterval)_displayTimerFrequency);
+#endif
+}
+
+- (CFTimeInterval)_currentRenderTime
+{
+  CFTimeInterval time = CACurrentMediaTime();
+
+#if TARGET_IPHONE_SIMULATOR
+  // support slow-motion animations
+  time += _slowMotionAccumulator;
+  float f = POPAnimationDragCoefficient();
+
+  if (f > 1.0) {
+    if (!_slowMotionStartTime) {
+      _slowMotionStartTime = time;
+    } else {
+      time = (time - _slowMotionStartTime) / f + _slowMotionStartTime;
+      _slowMotionLastTime = time;
+    }
+  } else if (_slowMotionStartTime) {
+    CFTimeInterval dt = (_slowMotionLastTime - time);
+    time += dt;
+    _slowMotionAccumulator += dt;
+    _slowMotionStartTime = 0;
+  }
+#endif
+
+  return time;
+}
+
+- (void)render
+{
+  CFTimeInterval time = [self _currentRenderTime];
+  [self renderTime:time];
+}
+
+- (void)renderTime:(CFTimeInterval)time
+{
+  [self _renderTime:time items:_list];
+}
+
+- (void)addObserver:(id<POPAnimatorObserving>)observer
+{
+  NSAssert(nil != observer, @"attempting to add nil %@ observer", self);
+  if (nil == observer) {
+    return;
+  }
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  if (!_observers) {
+    // use ordered collection for deterministic callout
+    _observers = [[NSMutableArray alloc] initWithCapacity:1];
+  }
+
+  [_observers addObject:observer];
+  updateDisplayLink(self);
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+}
+
+- (void)removeObserver:(id<POPAnimatorObserving>)observer
+{
+  NSAssert(nil != observer, @"attempting to remove nil %@ observer", self);
+  if (nil == observer) {
+    return;
+  }
+
+  // lock
+  pthread_mutex_lock(&_lock);
+
+  [_observers removeObject:observer];
+  updateDisplayLink(self);
+
+  // unlock
+  pthread_mutex_unlock(&_lock);
+}
+
+@end

pop/POPAnimatorPrivate.h

@@ -0,0 +1,74 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <pop/POPAnimator.h>
+
+@class POPAnimation;
+
+@protocol POPAnimatorObserving <NSObject>
+@required
+
+/**
+ @abstract Called on each observer after animator has advanced. Core Animation actions are disabled by default.
+ */
+- (void)animatorDidAnimate:(POPAnimator *)animator;
+
+@end
+
+@interface POPAnimator ()
+
+#if !TARGET_OS_IPHONE
+/**
+ Determines whether or not to use a high priority background thread for animation updates. Using a background thread can result in faster, more responsive updates, but may be less compatible. Defaults to YES.
+ */
++ (BOOL)disableBackgroundThread;
++ (void)setDisableBackgroundThread:(BOOL)flag;
+
+/**
+ Determines the frequency (Hz) of the timer used when no display is available. Defaults to 60Hz.
+ */
++ (uint64_t)displayTimerFrequency;
++ (void)setDisplayTimerFrequency:(uint64_t)frequency;
+#endif
+
+/**
+ Used for externally driven animator instances.
+ */
+@property (assign, nonatomic) BOOL disableDisplayLink;
+
+/**
+ Time used when starting animations. Defaults to 0 meaning current media time is used. Exposed for unit testing.
+ */
+@property (assign, nonatomic) CFTimeInterval beginTime;
+
+/**
+ Exposed for unit testing.
+ */
+- (void)renderTime:(CFTimeInterval)time;
+
+/**
+ Funnel methods for category additions.
+ */
+- (void)addAnimation:(POPAnimation *)anim forObject:(id)obj key:(NSString *)key;
+- (void)removeAllAnimationsForObject:(id)obj;
+- (void)removeAnimationForObject:(id)obj key:(NSString *)key;
+- (NSArray *)animationKeysForObject:(id)obj;
+- (POPAnimation *)animationForObject:(id)obj key:(NSString *)key;
+
+/**
+ @abstract Add an animator observer. Observer will be notified of each subsequent animator advance until removal.
+ */
+- (void)addObserver:(id<POPAnimatorObserving>)observer;
+
+/**
+ @abstract Remove an animator observer.
+ */
+- (void)removeObserver:(id<POPAnimatorObserving>)observer;
+
+@end

pop/POPBasicAnimation.h

@@ -0,0 +1,71 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <pop/POPPropertyAnimation.h>
+
+/**
+ @abstract A concrete basic animation class.
+ @discussion Animation is achieved through interpolation.
+ */
+@interface POPBasicAnimation : POPPropertyAnimation
+
+/**
+ @abstract The designated initializer.
+ @returns An instance of a basic animation.
+ */
++ (instancetype)animation;
+
+/**
+ @abstract Convenience initializer that returns an animation with animatable property of name.
+ @param name The name of the animatable property.
+ @returns An instance of a basic animation configured with specified animatable property.
+ */
++ (instancetype)animationWithPropertyNamed:(NSString *)name;
+
+/**
+ @abstract Convenience constructor.
+ @returns Returns a basic animation with kCAMediaTimingFunctionDefault timing function.
+ */
++ (instancetype)defaultAnimation;
+
+/**
+ @abstract Convenience constructor.
+ @returns Returns a basic animation with kCAMediaTimingFunctionLinear timing function.
+ */
++ (instancetype)linearAnimation;
+
+/**
+ @abstract Convenience constructor.
+ @returns Returns a basic animation with kCAMediaTimingFunctionEaseIn timing function.
+ */
++ (instancetype)easeInAnimation;
+
+/**
+ @abstract Convenience constructor.
+ @returns Returns a basic animation with kCAMediaTimingFunctionEaseOut timing function.
+ */
++ (instancetype)easeOutAnimation;
+
+/**
+ @abstract Convenience constructor.
+ @returns Returns a basic animation with kCAMediaTimingFunctionEaseInEaseOut timing function.
+ */
++ (instancetype)easeInEaseOutAnimation;
+
+/**
+ @abstract The duration in seconds. Defaults to 0.4.
+ */
+@property (assign, nonatomic) CFTimeInterval duration;
+
+/**
+ @abstract A timing function defining the pacing of the animation. Defaults to nil indicating pacing according to kCAMediaTimingFunctionDefault.
+ */
+@property (strong, nonatomic) CAMediaTimingFunction *timingFunction;
+
+@end

pop/POPBasicAnimation.mm

@@ -0,0 +1,106 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPBasicAnimationInternal.h"
+
+@implementation POPBasicAnimation
+
+#undef __state
+#define __state ((POPBasicAnimationState *)_state)
+
+#pragma mark - Lifecycle
+
++ (instancetype)animation
+{
+  return [[self alloc] init];
+}
+
++ (instancetype)animationWithPropertyNamed:(NSString *)aName
+{
+  POPBasicAnimation *anim = [self animation];
+  anim.property = [POPAnimatableProperty propertyWithName:aName];
+  return anim;
+}
+
+- (void)_initState
+{
+  _state = new POPBasicAnimationState(self);
+}
+
++ (instancetype)linearAnimation
+{
+  POPBasicAnimation *anim = [self animation];
+  anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
+  return anim;
+}
+
++ (instancetype)easeInAnimation
+{
+  POPBasicAnimation *anim = [self animation];
+  anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseIn];
+  return anim;
+}
+
++ (instancetype)easeOutAnimation
+{
+  POPBasicAnimation *anim = [self animation];
+  anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseOut];
+  return anim;
+}
+
++ (instancetype)easeInEaseOutAnimation
+{
+  POPBasicAnimation *anim = [self animation];
+  anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
+  return anim;
+}
+
++ (instancetype)defaultAnimation
+{
+  POPBasicAnimation *anim = [self animation];
+  anim.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault];
+  return anim;
+}
+
+- (id)init
+{
+  return [self _init];
+}
+
+#pragma mark - Properties
+
+DEFINE_RW_PROPERTY(POPBasicAnimationState, duration, setDuration:, CFTimeInterval);
+DEFINE_RW_PROPERTY_OBJ(POPBasicAnimationState, timingFunction, setTimingFunction:, CAMediaTimingFunction*, __state->updatedTimingFunction(););
+
+#pragma mark - Utility
+
+- (void)_appendDescription:(NSMutableString *)s debug:(BOOL)debug
+{
+  [super _appendDescription:s debug:debug];
+  if (__state->duration)
+    [s appendFormat:@"; duration = %f", __state->duration];
+}
+
+@end
+
+@implementation POPBasicAnimation (NSCopying)
+
+- (instancetype)copyWithZone:(NSZone *)zone {
+  
+  POPBasicAnimation *copy = [super copyWithZone:zone];
+  
+  if (copy) {
+    copy.duration = self.duration;
+    copy.timingFunction = self.timingFunction; // not a 'copy', but timing functions are publicly immutable.
+  }
+  
+  return copy;
+}
+
+@end

pop/POPBasicAnimationInternal.h

@@ -0,0 +1,97 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPBasicAnimation.h"
+
+#import "POPPropertyAnimationInternal.h"
+
+// default animation duration
+static CGFloat const kPOPAnimationDurationDefault = 0.4;
+
+// progress threshold for computing done
+static CGFloat const kPOPProgressThreshold = 1e-6;
+
+static void interpolate(POPValueType valueType, NSUInteger count, const CGFloat *fromVec, const CGFloat *toVec, CGFloat *outVec, CGFloat p)
+{
+  switch (valueType) {
+    case kPOPValueInteger:
+    case kPOPValueFloat:
+    case kPOPValuePoint:
+    case kPOPValueSize:
+    case kPOPValueRect:
+    case kPOPValueEdgeInsets:
+    case kPOPValueColor:
+      POPInterpolateVector(count, outVec, fromVec, toVec, p);
+      break;
+    default:
+      NSCAssert(false, @"unhandled type %d", valueType);
+      break;
+  }
+}
+
+struct _POPBasicAnimationState : _POPPropertyAnimationState
+{
+  CAMediaTimingFunction *timingFunction;
+  double timingControlPoints[4];
+  CFTimeInterval duration;
+  CFTimeInterval timeProgress;
+
+  _POPBasicAnimationState(id __unsafe_unretained anim) : _POPPropertyAnimationState(anim),
+  timingFunction(nil),
+  timingControlPoints{0.},
+  duration(kPOPAnimationDurationDefault),
+  timeProgress(0.)
+  {
+    type = kPOPAnimationBasic;
+  }
+
+  bool isDone() {
+    if (_POPPropertyAnimationState::isDone()) {
+      return true;
+    }
+    return timeProgress + kPOPProgressThreshold >= 1.;
+  }
+
+  void updatedTimingFunction()
+  {
+    float vec[4] = {0.};
+    [timingFunction getControlPointAtIndex:1 values:&vec[0]];
+    [timingFunction getControlPointAtIndex:2 values:&vec[2]];
+    for (NSUInteger idx = 0; idx < POP_ARRAY_COUNT(vec); idx++) {
+      timingControlPoints[idx] = vec[idx];
+    }
+  }
+
+  bool advance(CFTimeInterval time, CFTimeInterval dt, id obj) {
+    // default timing function
+    if (!timingFunction) {
+      ((POPBasicAnimation *)self).timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionDefault];
+    }
+
+    // solve for normalized time, aka progress [0, 1]
+    CGFloat p = 1.0f;
+    if (duration > 0.0f) {
+        // cap local time to duration
+        CFTimeInterval t = MIN(time - startTime, duration) / duration;
+        p = POPTimingFunctionSolve(timingControlPoints, t, SOLVE_EPS(duration));
+        timeProgress = t;
+    } else {
+        timeProgress = 1.;
+    }
+
+    // interpolate and advance
+    interpolate(valueType, valueCount, fromVec->data(), toVec->data(), currentVec->data(), p);
+    progress = p;
+    clampCurrentValue();
+
+    return true;
+  }
+};
+
+typedef struct _POPBasicAnimationState POPBasicAnimationState;

pop/POPCGUtils.h

@@ -0,0 +1,152 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <CoreGraphics/CoreGraphics.h>
+
+#if TARGET_OS_IPHONE
+#import <UIKit/UIKit.h>
+#else
+#import <AppKit/AppKit.h>
+#endif
+
+#import "POPDefines.h"
+
+#if SCENEKIT_SDK_AVAILABLE
+#import <SceneKit/SceneKit.h>
+#endif
+
+POP_EXTERN_C_BEGIN
+
+NS_INLINE CGPoint values_to_point(const CGFloat values[])
+{
+  return CGPointMake(values[0], values[1]);
+}
+
+NS_INLINE CGSize values_to_size(const CGFloat values[])
+{
+  return CGSizeMake(values[0], values[1]);
+}
+
+NS_INLINE CGRect values_to_rect(const CGFloat values[])
+{
+  return CGRectMake(values[0], values[1], values[2], values[3]);
+}
+
+#if SCENEKIT_SDK_AVAILABLE
+NS_INLINE SCNVector3 values_to_vec3(const CGFloat values[])
+{
+  return SCNVector3Make(values[0], values[1], values[2]);
+}
+
+NS_INLINE SCNVector4 values_to_vec4(const CGFloat values[])
+{
+  return SCNVector4Make(values[0], values[1], values[2], values[3]);
+}
+#endif
+
+#if TARGET_OS_IPHONE
+
+NS_INLINE UIEdgeInsets values_to_edge_insets(const CGFloat values[])
+{
+  return UIEdgeInsetsMake(values[0], values[1], values[2], values[3]);
+}
+
+#endif
+
+NS_INLINE void values_from_point(CGFloat values[], CGPoint p)
+{
+  values[0] = p.x;
+  values[1] = p.y;
+}
+
+NS_INLINE void values_from_size(CGFloat values[], CGSize s)
+{
+  values[0] = s.width;
+  values[1] = s.height;
+}
+
+NS_INLINE void values_from_rect(CGFloat values[], CGRect r)
+{
+  values[0] = r.origin.x;
+  values[1] = r.origin.y;
+  values[2] = r.size.width;
+  values[3] = r.size.height;
+}
+
+#if SCENEKIT_SDK_AVAILABLE
+NS_INLINE void values_from_vec3(CGFloat values[], SCNVector3 v)
+{
+  values[0] = v.x;
+  values[1] = v.y;
+  values[2] = v.z;
+}
+
+NS_INLINE void values_from_vec4(CGFloat values[], SCNVector4 v)
+{
+  values[0] = v.x;
+  values[1] = v.y;
+  values[2] = v.z;
+  values[3] = v.w;
+}
+#endif
+
+#if TARGET_OS_IPHONE
+
+NS_INLINE void values_from_edge_insets(CGFloat values[], UIEdgeInsets i)
+{
+  values[0] = i.top;
+  values[1] = i.left;
+  values[2] = i.bottom;
+  values[3] = i.right;
+}
+
+#endif
+
+/**
+ Takes a CGColorRef and converts it into RGBA components, if necessary.
+ */
+extern void POPCGColorGetRGBAComponents(CGColorRef color, CGFloat components[]);
+
+/**
+ Takes RGBA components and returns a CGColorRef.
+ */
+extern CGColorRef POPCGColorRGBACreate(const CGFloat components[]) CF_RETURNS_RETAINED;
+
+/**
+ Takes a color reference and returns a CGColor.
+ */
+extern CGColorRef POPCGColorWithColor(id color) CF_RETURNS_NOT_RETAINED;
+
+#if TARGET_OS_IPHONE
+
+/**
+ Takes a UIColor and converts it into RGBA components, if necessary.
+ */
+extern void POPUIColorGetRGBAComponents(UIColor *color, CGFloat components[]);
+
+/**
+ Takes RGBA components and returns a UIColor.
+ */
+extern UIColor *POPUIColorRGBACreate(const CGFloat components[]) NS_RETURNS_RETAINED;
+
+#else
+
+/**
+ Takes a NSColor and converts it into RGBA components, if necessary.
+ */
+extern void POPNSColorGetRGBAComponents(NSColor *color, CGFloat components[]);
+
+/**
+ Takes RGBA components and returns a NSColor.
+ */
+extern NSColor *POPNSColorRGBACreate(const CGFloat components[]) NS_RETURNS_RETAINED;
+
+#endif
+
+POP_EXTERN_C_END

pop/POPCGUtils.mm

@@ -0,0 +1,150 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPCGUtils.h"
+
+#import <objc/runtime.h>
+
+void POPCGColorGetRGBAComponents(CGColorRef color, CGFloat components[])
+{
+  if (color) {
+    const CGFloat *colors = CGColorGetComponents(color);
+    size_t count = CGColorGetNumberOfComponents(color);
+
+    if (4 == count) {
+      // RGB colorspace
+      components[0] = colors[0];
+      components[1] = colors[1];
+      components[2] = colors[2];
+      components[3] = colors[3];
+    } else if (2 == count) {
+      // Grey colorspace
+      components[0] = components[1] = components[2] = colors[0];
+      components[3] = colors[1];
+    } else {
+      // Use CI to convert
+      CIColor *ciColor = [CIColor colorWithCGColor:color];
+      components[0] = ciColor.red;
+      components[1] = ciColor.green;
+      components[2] = ciColor.blue;
+      components[3] = ciColor.alpha;
+    }
+  } else {
+    memset(components, 0, 4 * sizeof(components[0]));
+  }
+}
+
+CGColorRef POPCGColorRGBACreate(const CGFloat components[])
+{
+#if TARGET_OS_IPHONE
+  CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB();
+  CGColorRef color = CGColorCreate(space, components);
+  CGColorSpaceRelease(space);
+  return color;
+#else
+  return CGColorCreateGenericRGB(components[0], components[1], components[2], components[3]);
+#endif
+}
+
+CGColorRef POPCGColorWithColor(id color)
+{
+  if (CFGetTypeID((__bridge CFTypeRef)color) == CGColorGetTypeID()) {
+    return ((__bridge CGColorRef)color);
+  }
+#if TARGET_OS_IPHONE
+  else if ([color isKindOfClass:[UIColor class]]) {
+    return [color CGColor];
+  }
+#else
+  else if ([color isKindOfClass:[NSColor class]]) {
+    // -[NSColor CGColor] is only supported since OSX 10.8+
+    if ([color respondsToSelector:@selector(CGColor)]) {
+      return [color CGColor];
+    }
+
+    /*
+     * Otherwise create a CGColorRef manually.
+     *
+     * The original accessor is (or would be) declared as:
+     *   @property(readonly) CGColorRef CGColor;
+     *   - (CGColorRef)CGColor NS_RETURNS_INNER_POINTER CF_RETURNS_NOT_RETAINED;
+     *
+     * (Please note that OSX' accessor is atomic, while iOS' isn't.)
+     *
+     * The access to the NSColor object must thus be synchronized
+     * and the CGColorRef be stored as an associated object,
+     * to return a reference which doesn't need to be released manually.
+     */
+    @synchronized(color) {
+      static const void* key = &key;
+
+      CGColorRef colorRef = (__bridge CGColorRef)objc_getAssociatedObject(color, key);
+
+      if (!colorRef) {
+        size_t numberOfComponents = [(NSColor *)color numberOfComponents];
+        CGFloat components[numberOfComponents];
+        CGColorSpaceRef colorSpace = [[(NSColor *)color colorSpace] CGColorSpace];
+
+        [color getComponents:components];
+
+        colorRef = CGColorCreate(colorSpace, components);
+
+        objc_setAssociatedObject(color, key, (__bridge id)colorRef, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
+        CGColorRelease(colorRef);
+      }
+
+      return colorRef;
+    }
+  }
+#endif
+  return nil;
+}
+
+#if TARGET_OS_IPHONE
+
+void POPUIColorGetRGBAComponents(UIColor *color, CGFloat components[])
+{
+  return POPCGColorGetRGBAComponents(POPCGColorWithColor(color), components);
+}
+
+UIColor *POPUIColorRGBACreate(const CGFloat components[])
+{
+  CGColorRef colorRef = POPCGColorRGBACreate(components);
+  UIColor *color = [[UIColor alloc] initWithCGColor:colorRef];
+  CGColorRelease(colorRef);
+  return color;
+}
+
+#else
+
+void POPNSColorGetRGBAComponents(NSColor *color, CGFloat components[])
+{
+  return POPCGColorGetRGBAComponents(POPCGColorWithColor(color), components);
+}
+
+NSColor *POPNSColorRGBACreate(const CGFloat components[])
+{
+  CGColorRef colorRef = POPCGColorRGBACreate(components);
+  NSColor *color = nil;
+
+  if (colorRef) {
+    if ([NSColor respondsToSelector:@selector(colorWithCGColor:)]) {
+      color = [NSColor colorWithCGColor:colorRef];
+    } else {
+      color = [NSColor colorWithCIColor:[CIColor colorWithCGColor:colorRef]];
+    }
+
+    CGColorRelease(colorRef);
+  }
+
+  return color;
+}
+
+#endif
+

pop/POPCustomAnimation.h

@@ -0,0 +1,46 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <pop/POPAnimation.h>
+
+@class POPCustomAnimation;
+
+/**
+ @abstract POPCustomAnimationBlock is the callback block of a custom animation.
+ @discussion This block will be executed for each animation frame and should update the property or properties being animated based on current timing.
+ @param target The object being animated. Reference the passed in target to help avoid retain loops.
+ @param animation The custom animation instance. Use to determine the current and elapsed time since last callback. Reference the passed in animation to help avoid retain loops.
+ @return Flag indicating whether the animation should continue animating. Return NO to indicate animation is done.
+ */
+typedef BOOL (^POPCustomAnimationBlock)(id target, POPCustomAnimation *animation);
+
+/**
+ @abstract POPCustomAnimation is a concrete animation subclass for custom animations.
+ */
+@interface POPCustomAnimation : POPAnimation
+
+/**
+@abstract Creates and returns an initialized custom animation instance.
+@discussion This is the designated initializer.
+@param block The custom animation callback block. See {@ref POPCustomAnimationBlock}.
+@return The initialized custom animation instance.
+*/
++ (instancetype)animationWithBlock:(POPCustomAnimationBlock)block;
+
+/**
+ @abstract The current animation time at time of callback.
+ */
+@property (readonly, nonatomic) CFTimeInterval currentTime;
+
+/**
+ @abstract The elapsed animation time since last callback.
+ */
+@property (readonly, nonatomic) CFTimeInterval elapsedTime;
+
+@end

pop/POPCustomAnimation.mm

@@ -0,0 +1,75 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimationInternal.h"
+
+#import "POPCustomAnimation.h"
+
+@interface POPCustomAnimation ()
+@property (nonatomic, copy) POPCustomAnimationBlock animate;
+@end
+
+@implementation POPCustomAnimation
+@synthesize currentTime = _currentTime;
+@synthesize elapsedTime = _elapsedTime;
+@synthesize animate = _animate;
+
++ (instancetype)animationWithBlock:(BOOL(^)(id target, POPCustomAnimation *))block
+{
+  POPCustomAnimation *b = [[self alloc] _init];
+  b.animate = block;
+  return b;
+}
+
+- (id)_init
+{
+  self = [super _init];
+  if (nil != self) {
+    _state->type = kPOPAnimationCustom;
+  }
+  return self;
+}
+
+- (CFTimeInterval)beginTime
+{
+  POPAnimationState *s = POPAnimationGetState(self);
+  return s->startTime > 0 ? s->startTime : s->beginTime;
+}
+
+- (BOOL)_advance:(id)object currentTime:(CFTimeInterval)currentTime elapsedTime:(CFTimeInterval)elapsedTime
+{
+  _currentTime = currentTime;
+  _elapsedTime = elapsedTime;
+  return _animate(object, self);
+}
+
+- (void)_appendDescription:(NSMutableString *)s debug:(BOOL)debug
+{
+  [s appendFormat:@"; elapsedTime = %f; currentTime = %f;", _elapsedTime, _currentTime];
+}
+
+@end
+
+/**
+ *  Note that only the animate block is copied, but not the current/elapsed times
+ */
+@implementation POPCustomAnimation (NSCopying)
+
+- (instancetype)copyWithZone:(NSZone *)zone {
+  
+  POPCustomAnimation *copy = [super copyWithZone:zone];
+  
+  if (copy) {
+    copy.animate = self.animate;
+  }
+  
+  return copy;
+}
+
+@end

pop/POPDecayAnimation.h

@@ -0,0 +1,66 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <pop/POPPropertyAnimation.h>
+
+/**
+ @abstract A concrete decay animation class.
+ @discussion Animation is achieved through gradual decay of animation value.
+ */
+@interface POPDecayAnimation : POPPropertyAnimation
+
+/**
+ @abstract The designated initializer.
+ @returns An instance of a decay animation.
+ */
++ (instancetype)animation;
+
+/**
+ @abstract Convenience initializer that returns an animation with animatable property of name.
+ @param name The name of the animatable property.
+ @returns An instance of a decay animation configured with specified animatable property.
+ */
++ (instancetype)animationWithPropertyNamed:(NSString *)name;
+
+/**
+ @abstract The current velocity value.
+ @discussion Set before animation start to account for initial velocity. Expressed in change of value units per second. The only POPValueTypes supported for velocity are: kPOPValuePoint, kPOPValueInteger, kPOPValueFloat, kPOPValueRect, and kPOPValueSize.
+ */
+@property (copy, nonatomic) id velocity;
+
+/**
+ @abstract The original velocity value.
+ @discussion Since the velocity property is modified as the animation progresses, this property stores the original, passed in velocity to support autoreverse and repeatCount.
+ */
+@property (copy, nonatomic, readonly) id originalVelocity;
+
+/**
+ @abstract The deceleration factor.
+ @discussion Values specifies should be in the range [0, 1]. Lower values results in faster deceleration. Defaults to 0.998.
+ */
+@property (assign, nonatomic) CGFloat deceleration;
+
+/**
+ @abstract The expected duration.
+ @discussion Derived based on input velocity and deceleration values.
+ */
+@property (readonly, assign, nonatomic) CFTimeInterval duration;
+
+/**
+ The to value is derived based on input velocity and deceleration.
+ */
+- (void)setToValue:(id)toValue NS_UNAVAILABLE;
+
+/**
+ @abstract The reversed velocity.
+ @discussion The reversed velocity based on the originalVelocity when the animation was set up.
+ */
+- (id)reversedVelocity;
+
+@end

pop/POPDecayAnimation.mm

@@ -0,0 +1,203 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPDecayAnimationInternal.h"
+
+#if TARGET_OS_IPHONE
+#import <UIKit/UIKit.h>
+#endif
+
+const POPValueType supportedVelocityTypes[6] = { kPOPValuePoint, kPOPValueInteger, kPOPValueFloat, kPOPValueRect, kPOPValueSize, kPOPValueEdgeInsets };
+
+@implementation POPDecayAnimation
+
+#pragma mark - Lifecycle
+
+#undef __state
+#define __state ((POPDecayAnimationState *)_state)
+
++ (instancetype)animation
+{
+  return [[self alloc] init];
+}
+
++ (instancetype)animationWithPropertyNamed:(NSString *)aName
+{
+  POPDecayAnimation *anim = [self animation];
+  anim.property = [POPAnimatableProperty propertyWithName:aName];
+  return anim;
+}
+
+- (id)init
+{
+  return [self _init];
+}
+
+- (void)_initState
+{
+  _state = new POPDecayAnimationState(self);
+}
+
+#pragma mark - Properties
+
+DEFINE_RW_PROPERTY(POPDecayAnimationState, deceleration, setDeceleration:, CGFloat, __state->toVec = NULL;);
+
+@dynamic velocity;
+
+- (id)toValue
+{
+  [self _ensureComputedProperties];
+  return POPBox(__state->toVec, __state->valueType);
+}
+
+- (CFTimeInterval)duration
+{
+  [self _ensureComputedProperties];
+  return __state->duration;
+}
+
+- (void)setFromValue:(id)fromValue
+{
+  super.fromValue = fromValue;
+  [self _invalidateComputedProperties];
+}
+
+- (void)setToValue:(id)aValue
+{
+  // no-op
+  NSLog(@"ignoring to value on decay animation %@", self);
+}
+
+- (id)reversedVelocity
+{
+  id reversedVelocity = nil;
+
+  POPValueType velocityType = POPSelectValueType(self.originalVelocity, supportedVelocityTypes, POP_ARRAY_COUNT(supportedVelocityTypes));
+  if (velocityType == kPOPValueFloat) {
+#if CGFLOAT_IS_DOUBLE
+    CGFloat originalVelocityFloat = [(NSNumber *)self.originalVelocity doubleValue];
+#else
+    CGFloat originalVelocityFloat = [(NSNumber *)self.originalVelocity floatValue];
+#endif
+    NSNumber *negativeOriginalVelocityNumber = @(-originalVelocityFloat);
+    reversedVelocity = negativeOriginalVelocityNumber;
+  } else if (velocityType == kPOPValueInteger) {
+    NSInteger originalVelocityInteger = [(NSNumber *)self.originalVelocity integerValue];
+    NSNumber *negativeOriginalVelocityNumber = @(-originalVelocityInteger);
+    reversedVelocity = negativeOriginalVelocityNumber;
+  } else if (velocityType == kPOPValuePoint) {
+    CGPoint originalVelocityPoint = [self.originalVelocity CGPointValue];
+    CGPoint negativeOriginalVelocityPoint = CGPointMake(-originalVelocityPoint.x, -originalVelocityPoint.y);
+    reversedVelocity = [NSValue valueWithCGPoint:negativeOriginalVelocityPoint];
+  } else if (velocityType == kPOPValueRect) {
+    CGRect originalVelocityRect = [self.originalVelocity CGRectValue];
+    CGRect negativeOriginalVelocityRect = CGRectMake(-originalVelocityRect.origin.x, -originalVelocityRect.origin.y, -originalVelocityRect.size.width, -originalVelocityRect.size.height);
+    reversedVelocity = [NSValue valueWithCGRect:negativeOriginalVelocityRect];
+  } else if (velocityType == kPOPValueSize) {
+    CGSize originalVelocitySize = [self.originalVelocity CGSizeValue];
+    CGSize negativeOriginalVelocitySize = CGSizeMake(-originalVelocitySize.width, -originalVelocitySize.height);
+    reversedVelocity = [NSValue valueWithCGSize:negativeOriginalVelocitySize];
+  } else if (velocityType == kPOPValueEdgeInsets) {
+#if TARGET_OS_IPHONE
+    UIEdgeInsets originalVelocityInsets = [self.originalVelocity UIEdgeInsetsValue];
+    UIEdgeInsets negativeOriginalVelocityInsets = UIEdgeInsetsMake(-originalVelocityInsets.top, -originalVelocityInsets.left, -originalVelocityInsets.bottom, -originalVelocityInsets.right);
+    reversedVelocity = [NSValue valueWithUIEdgeInsets:negativeOriginalVelocityInsets];
+#endif
+  }
+
+  return reversedVelocity;
+}
+
+- (id)originalVelocity
+{
+  return POPBox(__state->originalVelocityVec, __state->valueType);
+}
+
+- (id)velocity
+{
+  return POPBox(__state->velocityVec, __state->valueType);
+}
+
+- (void)setVelocity:(id)aValue
+{
+  POPValueType valueType = POPSelectValueType(aValue, supportedVelocityTypes, POP_ARRAY_COUNT(supportedVelocityTypes));
+  if (valueType != kPOPValueUnknown) {
+    VectorRef vec = POPUnbox(aValue, __state->valueType, __state->valueCount, YES);
+    VectorRef origVec = POPUnbox(aValue, __state->valueType, __state->valueCount, YES);
+
+    if (!vec_equal(vec, __state->velocityVec)) {
+      __state->velocityVec = vec;
+      __state->originalVelocityVec = origVec;
+
+      if (__state->tracing) {
+        [__state->tracer updateVelocity:aValue];
+      }
+
+      [self _invalidateComputedProperties];
+
+      // automatically unpause active animations
+      if (__state->active && __state->paused) {
+        __state->fromVec = NULL;
+        __state->setPaused(false);
+      }
+    }
+  } else {
+    __state->velocityVec = NULL;
+    NSLog(@"Invalid velocity value for the decayAnimation: %@", aValue);
+  }
+}
+
+#pragma mark - Utility
+
+- (void)_ensureComputedProperties
+{
+  if (NULL == __state->toVec) {
+    __state->computeDuration();
+    __state->computeToValue();
+  }
+}
+
+- (void)_invalidateComputedProperties
+{
+  __state->toVec = NULL;
+  __state->duration = 0;
+}
+
+- (void)_appendDescription:(NSMutableString *)s debug:(BOOL)debug
+{
+  [super _appendDescription:s debug:debug];
+
+  if (0 != self.duration) {
+    [s appendFormat:@"; duration = %f", self.duration];
+  }
+
+  if (__state->deceleration) {
+    [s appendFormat:@"; deceleration = %f", __state->deceleration];
+  }
+}
+
+@end
+
+@implementation POPDecayAnimation (NSCopying)
+
+- (instancetype)copyWithZone:(NSZone *)zone {
+  
+  POPDecayAnimation *copy = [super copyWithZone:zone];
+  
+  if (copy) {
+    // Set the velocity to the animation's original velocity, not its current.
+    copy.velocity = self.originalVelocity;
+    copy.deceleration = self.deceleration;
+    
+  }
+  
+  return copy;
+}
+
+@end

pop/POPDecayAnimationInternal.h

@@ -0,0 +1,127 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPDecayAnimation.h"
+
+#import <cmath>
+
+#import "POPPropertyAnimationInternal.h"
+
+// minimal velocity factor before decay animation is considered complete, in units / s
+static CGFloat kPOPAnimationDecayMinimalVelocityFactor = 5.;
+
+// default decay animation deceleration
+static CGFloat kPOPAnimationDecayDecelerationDefault = 0.998;
+
+static void decay_position(CGFloat *x, CGFloat *v, NSUInteger count, CFTimeInterval dt, CGFloat deceleration)
+{
+  dt *= 1000;
+
+  // v0 = v / 1000
+  // v = v0 * powf(deceleration, dt);
+  // v = v * 1000;
+
+  // x0 = x;
+  // x = x0 + v0 * deceleration * (1 - powf(deceleration, dt)) / (1 - deceleration)
+  float v0[count];
+  float kv = powf(deceleration, dt);
+  float kx = deceleration * (1 - kv) / (1 - deceleration);
+
+  for (NSUInteger idx = 0; idx < count; idx++) {
+    v0[idx] = v[idx] / 1000.;
+    v[idx] = v0[idx] * kv * 1000.;
+    x[idx] = x[idx] + v0[idx] * kx;
+  }
+}
+
+struct _POPDecayAnimationState : _POPPropertyAnimationState
+{
+  double deceleration;
+  CFTimeInterval duration;
+
+  _POPDecayAnimationState(id __unsafe_unretained anim) :
+  _POPPropertyAnimationState(anim),
+  deceleration(kPOPAnimationDecayDecelerationDefault),
+  duration(0)
+  {
+    type = kPOPAnimationDecay;
+  }
+
+  bool isDone() {
+    if (_POPPropertyAnimationState::isDone()) {
+      return true;
+    }
+
+    CGFloat f = dynamicsThreshold * kPOPAnimationDecayMinimalVelocityFactor;
+    const CGFloat *velocityValues = vec_data(velocityVec);
+    for (NSUInteger idx = 0; idx < valueCount; idx++) {
+      if (std::abs((velocityValues[idx])) >= f)
+        return false;
+    }
+    return true;
+
+  }
+
+  void computeDuration() {
+
+    // compute duration till threshold velocity
+    Vector4r scaledVelocity = vector4(velocityVec) / 1000.;
+
+    double k = dynamicsThreshold * kPOPAnimationDecayMinimalVelocityFactor / 1000.;
+    double vx = k / scaledVelocity.x;
+    double vy = k / scaledVelocity.y;
+    double vz = k / scaledVelocity.z;
+    double vw = k / scaledVelocity.w;
+    double d = log(deceleration) * 1000.;
+    duration = MAX(MAX(MAX(log(fabs(vx)) / d, log(fabs(vy)) / d), log(fabs(vz)) / d), log(fabs(vw)) / d);
+
+    // ensure velocity threshold is exceeded
+    if (std::isnan(duration) || duration < 0) {
+      duration = 0;
+    }
+  }
+
+  void computeToValue() {
+    // to value assuming final velocity as a factor of dynamics threshold
+    // derived from v' = v * d^dt used in decay_position
+    // to compute the to value with maximal dt, p' = p + (v * d) / (1 - d)
+    VectorRef fromValue = NULL != currentVec ? currentVec : fromVec;
+    if (!fromValue) {
+      return;
+    }
+
+    // ensure duration is computed
+    if (0 == duration) {
+      computeDuration();
+    }
+
+    // compute to value
+    VectorRef toValue(Vector::new_vector(fromValue.get()));
+    Vector4r velocity = velocityVec->vector4r();
+    decay_position(toValue->data(), velocity.data(), valueCount, duration, deceleration);
+    toVec = toValue;
+  }
+
+  bool advance(CFTimeInterval time, CFTimeInterval dt, id obj) {
+    // advance past not yet initialized animations
+    if (NULL == currentVec) {
+      return false;
+    }
+
+    decay_position(currentVec->data(), velocityVec->data(), valueCount, dt, deceleration);
+
+    // clamp to compute end value; avoid possibility of decaying past
+    clampCurrentValue(kPOPAnimationClampEnd | clampMode);
+
+    return true;
+  }
+
+};
+
+typedef struct _POPDecayAnimationState POPDecayAnimationState;

pop/POPDefines.h

@@ -0,0 +1,37 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#ifndef POP_POPDefines_h
+#define POP_POPDefines_h
+
+#import <Availability.h>
+
+#ifdef __cplusplus
+# define POP_EXTERN_C_BEGIN extern "C" {
+# define POP_EXTERN_C_END   }
+#else
+# define POP_EXTERN_C_BEGIN
+# define POP_EXTERN_C_END
+#endif
+
+#define POP_ARRAY_COUNT(x) sizeof(x) / sizeof(x[0])
+
+#if defined (__cplusplus) && defined (__GNUC__)
+# define POP_NOTHROW __attribute__ ((nothrow))
+#else
+# define POP_NOTHROW
+#endif
+
+#if defined(POP_USE_SCENEKIT)
+# if TARGET_OS_MAC || TARGET_OS_IPHONE
+#  define SCENEKIT_SDK_AVAILABLE 1
+# endif
+#endif
+
+#endif

pop/POPGeometry.h

@@ -0,0 +1,73 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+#if TARGET_OS_IPHONE
+#import <UIKit/UIGeometry.h>
+#endif
+
+#if !TARGET_OS_IPHONE
+
+/** NSValue extensions to support animatable types. */
+@interface NSValue (POP)
+
+/**
+ @abstract Creates an NSValue given a CGPoint.
+ */
++ (NSValue *)valueWithCGPoint:(CGPoint)point;
+
+/**
+ @abstract Creates an NSValue given a CGSize.
+ */
++ (NSValue *)valueWithCGSize:(CGSize)size;
+
+/**
+ @abstract Creates an NSValue given a CGRect.
+ */
++ (NSValue *)valueWithCGRect:(CGRect)rect;
+
+/**
+ @abstract Creates an NSValue given a CFRange.
+ */
++ (NSValue *)valueWithCFRange:(CFRange)range;
+
+/**
+ @abstract Creates an NSValue given a CGAffineTransform.
+ */
++ (NSValue *)valueWithCGAffineTransform:(CGAffineTransform)transform;
+
+/**
+ @abstract Returns the underlying CGPoint value.
+ */
+- (CGPoint)CGPointValue;
+
+/**
+ @abstract Returns the underlying CGSize value.
+ */
+- (CGSize)CGSizeValue;
+
+/**
+ @abstract Returns the underlying CGRect value.
+ */
+- (CGRect)CGRectValue;
+
+/**
+ @abstract Returns the underlying CFRange value.
+ */
+- (CFRange)CFRangeValue;
+
+/**
+ @abstract Returns the underlying CGAffineTransform value.
+ */
+- (CGAffineTransform)CGAffineTransformValue;
+
+@end
+
+#endif

pop/POPGeometry.mm

@@ -0,0 +1,94 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPGeometry.h"
+
+#if !TARGET_OS_IPHONE
+@implementation NSValue (POP)
+
++ (NSValue *)valueWithCGPoint:(CGPoint)point {
+  return [NSValue valueWithBytes:&point objCType:@encode(CGPoint)];
+}
+
++ (NSValue *)valueWithCGSize:(CGSize)size {
+  return [NSValue valueWithBytes:&size objCType:@encode(CGSize)];
+}
+
++ (NSValue *)valueWithCGRect:(CGRect)rect {
+  return [NSValue valueWithBytes:&rect objCType:@encode(CGRect)];
+}
+
++ (NSValue *)valueWithCFRange:(CFRange)range {
+  return [NSValue valueWithBytes:&range objCType:@encode(CFRange)];
+}
+
++ (NSValue *)valueWithCGAffineTransform:(CGAffineTransform)transform
+{
+  return [NSValue valueWithBytes:&transform objCType:@encode(CGAffineTransform)];
+}
+
+- (CGPoint)CGPointValue {
+  CGPoint result;
+  [self getValue:&result];
+  return result;
+}
+
+- (CGSize)CGSizeValue {
+  CGSize result;
+  [self getValue:&result];
+  return result;
+}
+
+- (CGRect)CGRectValue {
+  CGRect result;
+  [self getValue:&result];
+  return result;
+}
+
+- (CFRange)CFRangeValue {
+  CFRange result;
+  [self getValue:&result];
+  return result;
+}
+
+- (CGAffineTransform)CGAffineTransformValue {
+  CGAffineTransform result;
+  [self getValue:&result];
+  return result;
+}
+@end
+
+#endif
+
+#if TARGET_OS_IPHONE
+#import "POPDefines.h"
+
+#if SCENEKIT_SDK_AVAILABLE
+#import <SceneKit/SceneKit.h>
+
+/**
+  Dirty hacks because iOS is weird and decided to define both SCNVector3's and SCNVector4's objCType as "t". However @encode(SCNVector3) and @encode(SCNVector4) both return the proper definition ("{SCNVector3=fff}" and "{SCNVector4=ffff}" respectively)
+ 
+  [[NSValue valueWithSCNVector3:SCNVector3Make(0.0, 0.0, 0.0)] objcType] returns "t", whereas it should return "{SCNVector3=fff}".
+ 
+  *flips table*
+ */
+@implementation NSValue (SceneKitFixes)
+
++ (NSValue *)valueWithSCNVector3:(SCNVector3)vec3 {
+  return [NSValue valueWithBytes:&vec3 objCType:@encode(SCNVector3)];
+}
+
++ (NSValue *)valueWithSCNVector4:(SCNVector4)vec4 {
+  return [NSValue valueWithBytes:&vec4 objCType:@encode(SCNVector4)];
+}
+
+@end
+#endif
+#endif

pop/POPLayerExtras.h

@@ -0,0 +1,196 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <QuartzCore/QuartzCore.h>
+
+#import <pop/POPDefines.h>
+
+POP_EXTERN_C_BEGIN
+
+#pragma mark - Scale
+
+/**
+ @abstract Returns layer scale factor for the x axis.
+ */
+extern CGFloat POPLayerGetScaleX(CALayer *l);
+
+/**
+ @abstract Set layer scale factor for the x axis.
+ */
+extern void POPLayerSetScaleX(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer scale factor for the y axis.
+ */
+extern CGFloat POPLayerGetScaleY(CALayer *l);
+
+/**
+ @abstract Set layer scale factor for the y axis.
+ */
+extern void POPLayerSetScaleY(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer scale factor for the z axis.
+ */
+extern CGFloat POPLayerGetScaleZ(CALayer *l);
+
+/**
+ @abstract Set layer scale factor for the z axis.
+ */
+extern void POPLayerSetScaleZ(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer scale factors for x and y access as point.
+ */
+extern CGPoint POPLayerGetScaleXY(CALayer *l);
+
+/**
+ @abstract Sets layer x and y scale factors given point.
+ */
+extern void POPLayerSetScaleXY(CALayer *l, CGPoint p);
+
+#pragma mark - Translation
+
+/**
+ @abstract Returns layer translation factor for the x axis.
+ */
+extern CGFloat POPLayerGetTranslationX(CALayer *l);
+
+/**
+ @abstract Set layer translation factor for the x axis.
+ */
+extern void POPLayerSetTranslationX(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer translation factor for the y axis.
+ */
+extern CGFloat POPLayerGetTranslationY(CALayer *l);
+
+/**
+ @abstract Set layer translation factor for the y axis.
+ */
+extern void POPLayerSetTranslationY(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer translation factor for the z axis.
+ */
+extern CGFloat POPLayerGetTranslationZ(CALayer *l);
+
+/**
+ @abstract Set layer translation factor for the z axis.
+ */
+extern void POPLayerSetTranslationZ(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer translation factors for x and y access as point.
+ */
+extern CGPoint POPLayerGetTranslationXY(CALayer *l);
+
+/**
+ @abstract Sets layer x and y translation factors given point.
+ */
+extern void POPLayerSetTranslationXY(CALayer *l, CGPoint p);
+
+#pragma mark - Rotation
+
+/**
+ @abstract Returns layer rotation, in radians, in the X axis.
+ */
+extern CGFloat POPLayerGetRotationX(CALayer *l);
+
+/**
+ @abstract Sets layer rotation, in radians, in the X axis.
+ */
+extern void POPLayerSetRotationX(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer rotation, in radians, in the Y axis.
+ */
+extern CGFloat POPLayerGetRotationY(CALayer *l);
+
+/**
+ @abstract Sets layer rotation, in radians, in the Y axis.
+ */
+extern void POPLayerSetRotationY(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer rotation, in radians, in the Z axis.
+ */
+extern CGFloat POPLayerGetRotationZ(CALayer *l);
+
+/**
+ @abstract Sets layer rotation, in radians, in the Z axis.
+ */
+extern void POPLayerSetRotationZ(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns layer rotation, in radians, in the Z axis.
+ */
+extern CGFloat POPLayerGetRotation(CALayer *l);
+
+/**
+ @abstract Sets layer rotation, in radians, in the Z axis.
+ */
+extern void POPLayerSetRotation(CALayer *l, CGFloat f);
+
+#pragma mark - Sublayer Scale
+
+/**
+ @abstract Returns sublayer scale factors for x and y access as point.
+ */
+extern CGPoint POPLayerGetSubScaleXY(CALayer *l);
+
+/**
+ @abstract Sets sublayer x and y scale factors given point.
+ */
+extern void POPLayerSetSubScaleXY(CALayer *l, CGPoint p);
+
+#pragma mark - Sublayer Translation
+
+/**
+ @abstract Returns sublayer translation factor for the x axis.
+ */
+extern CGFloat POPLayerGetSubTranslationX(CALayer *l);
+
+/**
+ @abstract Set sublayer translation factor for the x axis.
+ */
+extern void POPLayerSetSubTranslationX(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns sublayer translation factor for the y axis.
+ */
+extern CGFloat POPLayerGetSubTranslationY(CALayer *l);
+
+/**
+ @abstract Set sublayer translation factor for the y axis.
+ */
+extern void POPLayerSetSubTranslationY(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns sublayer translation factor for the z axis.
+ */
+extern CGFloat POPLayerGetSubTranslationZ(CALayer *l);
+
+/**
+ @abstract Set sublayer translation factor for the z axis.
+ */
+extern void POPLayerSetSubTranslationZ(CALayer *l, CGFloat f);
+
+/**
+ @abstract Returns sublayer translation factors for x and y access as point.
+ */
+extern CGPoint POPLayerGetSubTranslationXY(CALayer *l);
+
+/**
+ @abstract Sets sublayer x and y translation factors given point.
+ */
+extern void POPLayerSetSubTranslationXY(CALayer *l, CGPoint p);
+
+POP_EXTERN_C_END

pop/POPLayerExtras.mm

@@ -0,0 +1,288 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPLayerExtras.h"
+
+#include "TransformationMatrix.h"
+
+using namespace WebCore;
+
+#define DECOMPOSE_TRANSFORM(L) \
+  TransformationMatrix _m(L.transform); \
+  TransformationMatrix::DecomposedType _d; \
+  _m.decompose(_d);
+
+#define RECOMPOSE_TRANSFORM(L) \
+  _m.recompose(_d); \
+  L.transform = _m.transform3d();
+
+#define RECOMPOSE_ROT_TRANSFORM(L) \
+  _m.recompose(_d, true); \
+  L.transform = _m.transform3d();
+
+#define DECOMPOSE_SUBLAYER_TRANSFORM(L) \
+  TransformationMatrix _m(L.sublayerTransform); \
+  TransformationMatrix::DecomposedType _d; \
+  _m.decompose(_d);
+
+#define RECOMPOSE_SUBLAYER_TRANSFORM(L) \
+  _m.recompose(_d); \
+  L.sublayerTransform = _m.transform3d();
+
+#pragma mark - Scale
+
+NS_INLINE void ensureNonZeroValue(CGFloat &f)
+{
+  if (f == 0) {
+    f = 1e-6;
+  }
+}
+
+NS_INLINE void ensureNonZeroValue(CGPoint &p)
+{
+  if (p.x == 0 && p.y == 0) {
+    p.x = 1e-6;
+    p.y = 1e-6;
+  }
+}
+
+CGFloat POPLayerGetScaleX(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.scaleX;
+}
+
+void POPLayerSetScaleX(CALayer *l, CGFloat f)
+{
+  ensureNonZeroValue(f);
+  DECOMPOSE_TRANSFORM(l);
+  _d.scaleX = f;
+  RECOMPOSE_TRANSFORM(l);
+}
+
+CGFloat POPLayerGetScaleY(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.scaleY;
+}
+
+void POPLayerSetScaleY(CALayer *l, CGFloat f)
+{
+  ensureNonZeroValue(f);
+  DECOMPOSE_TRANSFORM(l);
+  _d.scaleY = f;
+  RECOMPOSE_TRANSFORM(l);
+}
+
+CGFloat POPLayerGetScaleZ(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.scaleZ;
+}
+
+void POPLayerSetScaleZ(CALayer *l, CGFloat f)
+{
+  ensureNonZeroValue(f);
+  DECOMPOSE_TRANSFORM(l);
+  _d.scaleZ = f;
+  RECOMPOSE_TRANSFORM(l);
+}
+
+CGPoint POPLayerGetScaleXY(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return CGPointMake(_d.scaleX, _d.scaleY);
+}
+
+void POPLayerSetScaleXY(CALayer *l, CGPoint p)
+{
+  ensureNonZeroValue(p);
+  DECOMPOSE_TRANSFORM(l);
+  _d.scaleX = p.x;
+  _d.scaleY = p.y;
+  RECOMPOSE_TRANSFORM(l);
+}
+
+#pragma mark - Translation
+
+CGFloat POPLayerGetTranslationX(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.translateX;
+}
+
+void POPLayerSetTranslationX(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_TRANSFORM(l);
+  _d.translateX = f;
+  RECOMPOSE_TRANSFORM(l);
+}
+
+CGFloat POPLayerGetTranslationY(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.translateY;
+}
+
+void POPLayerSetTranslationY(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_TRANSFORM(l);
+  _d.translateY = f;
+  RECOMPOSE_TRANSFORM(l);
+}
+
+CGFloat POPLayerGetTranslationZ(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.translateZ;
+}
+
+void POPLayerSetTranslationZ(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_TRANSFORM(l);
+  _d.translateZ = f;
+  RECOMPOSE_TRANSFORM(l);
+}
+
+CGPoint POPLayerGetTranslationXY(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return CGPointMake(_d.translateX, _d.translateY);
+}
+
+void POPLayerSetTranslationXY(CALayer *l, CGPoint p)
+{
+  DECOMPOSE_TRANSFORM(l);
+  _d.translateX = p.x;
+  _d.translateY = p.y;
+  RECOMPOSE_TRANSFORM(l);
+}
+
+#pragma mark - Rotation
+
+CGFloat POPLayerGetRotationX(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.rotateX;
+}
+
+void POPLayerSetRotationX(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_TRANSFORM(l);
+  _d.rotateX = f;
+  RECOMPOSE_ROT_TRANSFORM(l);
+}
+
+CGFloat POPLayerGetRotationY(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.rotateY;
+}
+
+void POPLayerSetRotationY(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_TRANSFORM(l);
+  _d.rotateY = f;
+  RECOMPOSE_ROT_TRANSFORM(l);
+}
+
+CGFloat POPLayerGetRotationZ(CALayer *l)
+{
+  DECOMPOSE_TRANSFORM(l);
+  return _d.rotateZ;
+}
+
+void POPLayerSetRotationZ(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_TRANSFORM(l);
+  _d.rotateZ = f;
+  RECOMPOSE_ROT_TRANSFORM(l);
+}
+
+CGFloat POPLayerGetRotation(CALayer *l)
+{
+  return POPLayerGetRotationZ(l);
+}
+
+void POPLayerSetRotation(CALayer *l, CGFloat f)
+{
+  POPLayerSetRotationZ(l, f);
+}
+
+#pragma mark - Sublayer Scale
+
+CGPoint POPLayerGetSubScaleXY(CALayer *l)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  return CGPointMake(_d.scaleX, _d.scaleY);
+}
+
+void POPLayerSetSubScaleXY(CALayer *l, CGPoint p)
+{
+  ensureNonZeroValue(p);
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  _d.scaleX = p.x;
+  _d.scaleY = p.y;
+  RECOMPOSE_SUBLAYER_TRANSFORM(l);
+}
+
+#pragma mark - Sublayer Translation
+
+extern CGFloat POPLayerGetSubTranslationX(CALayer *l)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  return _d.translateX;
+}
+
+extern void POPLayerSetSubTranslationX(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  _d.translateX = f;
+  RECOMPOSE_SUBLAYER_TRANSFORM(l);
+}
+
+extern CGFloat POPLayerGetSubTranslationY(CALayer *l)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  return _d.translateY;
+}
+
+extern void POPLayerSetSubTranslationY(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  _d.translateY = f;
+  RECOMPOSE_SUBLAYER_TRANSFORM(l);
+}
+
+extern CGFloat POPLayerGetSubTranslationZ(CALayer *l)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  return _d.translateZ;
+}
+
+extern void POPLayerSetSubTranslationZ(CALayer *l, CGFloat f)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  _d.translateZ = f;
+  RECOMPOSE_SUBLAYER_TRANSFORM(l);
+}
+
+extern CGPoint POPLayerGetSubTranslationXY(CALayer *l)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  return CGPointMake(_d.translateX, _d.translateY);
+}
+
+extern void POPLayerSetSubTranslationXY(CALayer *l, CGPoint p)
+{
+  DECOMPOSE_SUBLAYER_TRANSFORM(l);
+  _d.translateX = p.x;
+  _d.translateY = p.y;
+  RECOMPOSE_SUBLAYER_TRANSFORM(l);
+}

pop/POPMath.h

@@ -0,0 +1,55 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import <CoreGraphics/CoreGraphics.h>
+
+#import "POPDefines.h"
+
+NS_INLINE CGFloat sqrtr(CGFloat f)
+{
+#if CGFLOAT_IS_DOUBLE
+  return sqrt(f);
+#else
+  return sqrtf(f);
+#endif
+}
+
+// round to nearest sub; pass 2.0 to round to every 0.5 (eg: retina pixels)
+NS_INLINE CGFloat POPSubRound(CGFloat f, CGFloat sub)
+{
+  return round(f * sub) / sub;
+}
+
+#define MIX(a, b, f) ((a) + (f) * ((b) - (a)))
+
+// the longer the duration, the higher the necessary precision
+#define SOLVE_EPS(dur) (1. / (1000. * (dur)))
+
+#define _EQLF_(x, y, epsilon) (fabsf ((x) - (y)) < epsilon)
+
+extern void POPInterpolateVector(NSUInteger count, CGFloat *dst, const CGFloat *from, const CGFloat *to, CGFloat f);
+
+extern double POPTimingFunctionSolve(const double vec[4], double t, double eps);
+
+// quadratic mapping of t [0, 1] to [start, end]
+extern double POPQuadraticOutInterpolation(double t, double start, double end);
+
+// normalize value to [0, 1] based on its range [startValue, endValue]
+extern double POPNormalize(double value, double startValue, double endValue);
+
+// project a normalized value [0, 1] to a given range [start, end]
+extern double POPProjectNormal(double n, double start, double end);
+
+// solve a quadratic equation of the form a * x^2 + b * x + c = 0
+extern void POPQuadraticSolve(CGFloat a, CGFloat b, CGFloat c, CGFloat &x1, CGFloat &x2);
+
+// for a given tension return the bouncy 3 friction that produces no bounce
+extern double POPBouncy3NoBounce(double tension);

pop/POPMath.mm

@@ -0,0 +1,83 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPMath.h"
+
+#import "POPAnimationPrivate.h"
+#import "UnitBezier.h"
+
+void POPInterpolateVector(NSUInteger count, CGFloat *dst, const CGFloat *from, const CGFloat *to, CGFloat f)
+{
+  for (NSUInteger idx = 0; idx < count; idx++) {
+    dst[idx] = MIX(from[idx], to[idx], f);
+  }
+}
+
+double POPTimingFunctionSolve(const double vec[4], double t, double eps)
+{
+  WebCore::UnitBezier bezier(vec[0], vec[1], vec[2], vec[3]);
+  return bezier.solve(t, eps);
+}
+
+double POPNormalize(double value, double startValue, double endValue)
+{
+  return (value - startValue) / (endValue - startValue);
+}
+
+double POPProjectNormal(double n, double start, double end)
+{
+  return start + (n * (end - start));
+}
+
+static double linear_interpolation(double t, double start, double end)
+{
+  return t * end + (1.f - t) * start;
+}
+
+double POPQuadraticOutInterpolation(double t, double start, double end)
+{
+  return linear_interpolation(2*t - t*t, start, end);
+}
+
+static double b3_friction1(double x)
+{
+  return (0.0007 * pow(x, 3)) - (0.031 * pow(x, 2)) + 0.64 * x + 1.28;
+}
+
+static double b3_friction2(double x)
+{
+  return (0.000044 * pow(x, 3)) - (0.006 * pow(x, 2)) + 0.36 * x + 2.;
+}
+
+static double b3_friction3(double x)
+{
+  return (0.00000045 * pow(x, 3)) - (0.000332 * pow(x, 2)) + 0.1078 * x + 5.84;
+}
+
+double POPBouncy3NoBounce(double tension)
+{
+  double friction = 0;
+  if (tension <= 18.) {
+    friction = b3_friction1(tension);
+  } else if (tension > 18 && tension <= 44) {
+    friction = b3_friction2(tension);
+  } else if (tension > 44) {
+    friction = b3_friction3(tension);
+  } else {
+    assert(false);
+  }
+  return friction;
+}
+
+void POPQuadraticSolve(CGFloat a, CGFloat b, CGFloat c, CGFloat &x1, CGFloat &x2)
+{
+  CGFloat discriminant = sqrt(b * b - 4 * a * c);
+  x1 = (-b + discriminant) / (2 * a);
+  x2 = (-b - discriminant) / (2 * a);
+}

pop/POPPropertyAnimation.h

@@ -0,0 +1,76 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <pop/POPAnimatableProperty.h>
+#import <pop/POPAnimation.h>
+
+/**
+ @abstract Flags for clamping animation values.
+ @discussion Animation values can optionally be clamped to avoid overshoot. kPOPAnimationClampStart ensures values are more than fromValue and kPOPAnimationClampEnd ensures values are less than toValue.
+ */
+typedef NS_OPTIONS(NSUInteger, POPAnimationClampFlags)
+{
+  kPOPAnimationClampNone        = 0,
+  kPOPAnimationClampStart       = 1UL << 0,
+  kPOPAnimationClampEnd         = 1UL << 1,
+  kPOPAnimationClampBoth = kPOPAnimationClampStart | kPOPAnimationClampEnd,
+};
+
+/**
+ @abstract The semi-concrete property animation subclass.
+ */
+@interface POPPropertyAnimation : POPAnimation
+
+/**
+ @abstract The property to animate.
+ */
+@property (strong, nonatomic) POPAnimatableProperty *property;
+
+/**
+ @abstract The value to animate from.
+ @discussion The value type should match the property. If unspecified, the value is initialized to the object's current value on animation start.
+ */
+@property (copy, nonatomic) id fromValue;
+
+/**
+ @abstract The value to animate to.
+ @discussion The value type should match the property. If unspecified, the value is initialized to the object's current value on animation start.
+ */
+@property (copy, nonatomic) id toValue;
+
+/**
+ @abstract The rounding factor applied to the current animated value.
+ @discussion Specify 1.0 to animate between integral values. Defaults to 0 meaning no rounding.
+ */
+@property (assign, nonatomic) CGFloat roundingFactor;
+
+/**
+ @abstract The clamp mode applied to the current animated value.
+ @discussion See {@ref POPAnimationClampFlags} for possible values. Defaults to kPOPAnimationClampNone.
+ */
+@property (assign, nonatomic) NSUInteger clampMode;
+
+/**
+ @abstract The flag indicating whether values should be "added" each frame, rather than set.
+ @discussion Addition may be type dependent. Defaults to NO.
+ */
+@property (assign, nonatomic, getter = isAdditive) BOOL additive;
+
+@end
+
+@interface POPPropertyAnimation (CustomProperty)
+
++ (instancetype)animationWithCustomPropertyNamed:(NSString *)name
+                                       readBlock:(POPAnimatablePropertyReadBlock)readBlock
+                                      writeBlock:(POPAnimatablePropertyWriteBlock)writeBlock;
+
++ (instancetype)animationWithCustomPropertyReadBlock:(POPAnimatablePropertyReadBlock)readBlock
+                                          writeBlock:(POPAnimatablePropertyWriteBlock)writeBlock;
+
+@end

pop/POPPropertyAnimation.mm

@@ -0,0 +1,149 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPPropertyAnimationInternal.h"
+
+@implementation POPPropertyAnimation
+
+#pragma mark - Lifecycle
+
+#undef __state
+#define __state ((POPPropertyAnimationState *)_state)
+
+- (void)_initState
+{
+  _state = new POPPropertyAnimationState(self);
+}
+
+#pragma mark - Properties
+
+DEFINE_RW_FLAG(POPPropertyAnimationState, additive, isAdditive, setAdditive:);
+DEFINE_RW_PROPERTY(POPPropertyAnimationState, roundingFactor, setRoundingFactor:, CGFloat);
+DEFINE_RW_PROPERTY(POPPropertyAnimationState, clampMode, setClampMode:, NSUInteger);
+DEFINE_RW_PROPERTY_OBJ(POPPropertyAnimationState, property, setProperty:, POPAnimatableProperty*, ((POPPropertyAnimationState*)_state)->updatedDynamicsThreshold(););
+DEFINE_RW_PROPERTY_OBJ_COPY(POPPropertyAnimationState, progressMarkers, setProgressMarkers:, NSArray*, ((POPPropertyAnimationState*)_state)->updatedProgressMarkers(););
+
+- (id)fromValue
+{
+  return POPBox(__state->fromVec, __state->valueType);
+}
+
+- (void)setFromValue:(id)aValue
+{
+  POPPropertyAnimationState *s = __state;
+  VectorRef vec = POPUnbox(aValue, s->valueType, s->valueCount, YES);
+  if (!vec_equal(vec, s->fromVec)) {
+    s->fromVec = vec;
+
+    if (s->tracing) {
+      [s->tracer updateFromValue:aValue];
+    }
+  }
+}
+
+- (id)toValue
+{
+  return POPBox(__state->toVec, __state->valueType);
+}
+
+- (void)setToValue:(id)aValue
+{
+  POPPropertyAnimationState *s = __state;
+  VectorRef vec = POPUnbox(aValue, s->valueType, s->valueCount, YES);
+
+  if (!vec_equal(vec, s->toVec)) {
+    s->toVec = vec;
+
+    // invalidate to dependent state
+    s->didReachToValue = false;
+    s->distanceVec = NULL;
+
+    if (s->tracing) {
+      [s->tracer updateToValue:aValue];
+    }
+
+    // automatically unpause active animations
+    if (s->active && s->paused) {
+      s->setPaused(false);
+    }
+  }
+}
+
+- (id)currentValue
+{
+  return POPBox(__state->currentValue(), __state->valueType);
+}
+
+#pragma mark - Utility
+
+- (void)_appendDescription:(NSMutableString *)s debug:(BOOL)debug
+{
+  [s appendFormat:@"; from = %@; to = %@", describe(__state->fromVec), describe(__state->toVec)];
+
+  if (_state->active)
+    [s appendFormat:@"; currentValue = %@", describe(__state->currentValue())];
+
+  if (__state->velocityVec && 0 != __state->velocityVec->norm())
+    [s appendFormat:@"; velocity = %@", describe(__state->velocityVec)];
+
+  if (!self.removedOnCompletion)
+    [s appendFormat:@"; removedOnCompletion = %@", POPStringFromBOOL(self.removedOnCompletion)];
+
+  if (__state->progressMarkers)
+    [s appendFormat:@"; progressMarkers = [%@]", [__state->progressMarkers componentsJoinedByString:@", "]];
+
+  if (_state->active)
+    [s appendFormat:@"; progress = %f", __state->progress];
+}
+
+@end
+
+@implementation POPPropertyAnimation (NSCopying)
+
+- (instancetype)copyWithZone:(NSZone *)zone {
+  
+  POPPropertyAnimation *copy = [super copyWithZone:zone];
+  
+  if (copy) {
+    copy.property = [self.property copyWithZone:zone];
+    copy.fromValue = self.fromValue;
+    copy.toValue = self.toValue;
+    copy.roundingFactor = self.roundingFactor;
+    copy.clampMode = self.clampMode;
+    copy.additive = self.additive;
+  }
+  
+  return copy;
+}
+
+@end
+
+@implementation POPPropertyAnimation (CustomProperty)
+
++ (instancetype)animationWithCustomPropertyNamed:(NSString *)name
+                                       readBlock:(POPAnimatablePropertyReadBlock)readBlock
+                                      writeBlock:(POPAnimatablePropertyWriteBlock)writeBlock
+{
+  POPPropertyAnimation *animation = [[self alloc] init];
+  animation.property = [POPAnimatableProperty propertyWithName:name initializer:^(POPMutableAnimatableProperty *prop) {
+    prop.readBlock = readBlock;
+    prop.writeBlock = writeBlock;
+  }];
+  return animation;
+}
+
++ (instancetype)animationWithCustomPropertyReadBlock:(POPAnimatablePropertyReadBlock)readBlock
+                                          writeBlock:(POPAnimatablePropertyWriteBlock)writeBlock
+{
+  return [self animationWithCustomPropertyNamed:[NSUUID UUID].UUIDString
+                                      readBlock:readBlock
+                                     writeBlock:writeBlock];
+}
+
+@end

pop/POPPropertyAnimationInternal.h

@@ -0,0 +1,359 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPAnimationInternal.h"
+#import "POPPropertyAnimation.h"
+
+static void clampValue(CGFloat &value, CGFloat fromValue, CGFloat toValue, NSUInteger clamp)
+{
+  BOOL increasing = (toValue > fromValue);
+
+  // Clamp start of animation.
+  if ((kPOPAnimationClampStart & clamp) &&
+      ((increasing && (value < fromValue)) || (!increasing && (value > fromValue)))) {
+    value = fromValue;
+  }
+
+  // Clamp end of animation.
+  if ((kPOPAnimationClampEnd & clamp) &&
+      ((increasing && (value > toValue)) || (!increasing && (value < toValue)))) {
+    value = toValue;
+  }
+}
+
+struct _POPPropertyAnimationState : _POPAnimationState
+{
+  POPAnimatableProperty *property;
+  POPValueType valueType;
+  NSUInteger valueCount;
+  VectorRef fromVec;
+  VectorRef toVec;
+  VectorRef currentVec;
+  VectorRef previousVec;
+  VectorRef previous2Vec;
+  VectorRef velocityVec;
+  VectorRef originalVelocityVec;
+  VectorRef distanceVec;
+  CGFloat roundingFactor;
+  NSUInteger clampMode;
+  NSArray *progressMarkers;
+  POPProgressMarker *progressMarkerState;
+  NSUInteger progressMarkerCount;
+  NSUInteger nextProgressMarkerIdx;
+  CGFloat dynamicsThreshold;
+
+  _POPPropertyAnimationState(id __unsafe_unretained anim) : _POPAnimationState(anim),
+  property(nil),
+  valueType((POPValueType)0),
+  valueCount(0),
+  fromVec(nullptr),
+  toVec(nullptr),
+  currentVec(nullptr),
+  previousVec(nullptr),
+  previous2Vec(nullptr),
+  velocityVec(nullptr),
+  originalVelocityVec(nullptr),
+  distanceVec(nullptr),
+  roundingFactor(0),
+  clampMode(0),
+  progressMarkers(nil),
+  progressMarkerState(nil),
+  progressMarkerCount(0),
+  nextProgressMarkerIdx(0),
+  dynamicsThreshold(0)
+  {
+    type = kPOPAnimationBasic;
+  }
+
+  ~_POPPropertyAnimationState()
+  {
+    if (progressMarkerState) {
+      free(progressMarkerState);
+      progressMarkerState = NULL;
+    }
+  }
+
+  bool canProgress() {
+    return hasValue();
+  }
+
+  bool shouldRound() {
+    return 0 != roundingFactor;
+  }
+
+  bool hasValue() {
+    return 0 != valueCount;
+  }
+
+  bool isDone() {
+    // inherit done
+    if (_POPAnimationState::isDone()) {
+      return true;
+    }
+
+    // consider an animation with no values done
+    if (!hasValue() && !isCustom()) {
+      return true;
+    }
+
+    return false;
+  }
+
+  // returns a copy of the currentVec, rounding if needed
+  VectorRef currentValue() {
+    VectorRef vec = VectorRef(Vector::new_vector(currentVec.get()));
+    if (shouldRound()) {
+      vec->subRound(1 / roundingFactor);
+    }
+      return vec;
+  }
+
+  void resetProgressMarkerState()
+  {
+    for (NSUInteger idx = 0; idx < progressMarkerCount; idx++)
+      progressMarkerState[idx].reached = false;
+
+    nextProgressMarkerIdx = 0;
+  }
+
+  void updatedProgressMarkers()
+  {
+    if (progressMarkerState) {
+      free(progressMarkerState);
+      progressMarkerState = NULL;
+    }
+
+    progressMarkerCount = progressMarkers.count;
+
+    if (0 != progressMarkerCount) {
+      progressMarkerState = (POPProgressMarker *)malloc(progressMarkerCount * sizeof(POPProgressMarker));
+      [progressMarkers enumerateObjectsUsingBlock:^(NSNumber *progressMarker, NSUInteger idx, BOOL *stop) {
+        progressMarkerState[idx].reached = false;
+        progressMarkerState[idx].progress = [progressMarker floatValue];
+      }];
+    }
+
+    nextProgressMarkerIdx = 0;
+  }
+
+  virtual void updatedDynamicsThreshold()
+  {
+    dynamicsThreshold = property.threshold;
+  }
+
+  void finalizeProgress()
+  {
+    progress = 1.0;
+    NSUInteger count = valueCount;
+    VectorRef outVec(Vector::new_vector(count, NULL));
+
+    if (outVec && toVec) {
+      *outVec = *toVec;
+    }
+
+    currentVec = outVec;
+    clampCurrentValue();
+    delegateProgress();
+  }
+
+  void computeProgress() {
+    if (!canProgress()) {
+      return;
+    }
+
+    static ComputeProgressFunctor<Vector4r> func;
+    Vector4r v = vector4(currentVec);
+    Vector4r f = vector4(fromVec);
+    Vector4r t = vector4(toVec);
+    progress = func(v, f, t);
+  }
+
+  void delegateProgress() {
+    if (!canProgress()) {
+      return;
+    }
+
+    if (delegateDidProgress && progressMarkerState) {
+
+      while (nextProgressMarkerIdx < progressMarkerCount) {
+        if (progress < progressMarkerState[nextProgressMarkerIdx].progress)
+          break;
+
+        if (!progressMarkerState[nextProgressMarkerIdx].reached) {
+          ActionEnabler enabler;
+          [delegate pop_animation:self didReachProgress:progressMarkerState[nextProgressMarkerIdx].progress];
+          progressMarkerState[nextProgressMarkerIdx].reached = true;
+        }
+
+        nextProgressMarkerIdx++;
+      }
+    }
+
+    if (!didReachToValue) {
+      bool didReachToValue = false;
+      if (0 == valueCount) {
+        didReachToValue = true;
+      } else {
+        Vector4r distance = toVec->vector4r();
+        distance -= currentVec->vector4r();
+
+        if (0 == distance.squaredNorm()) {
+          didReachToValue = true;
+        } else {
+          // components
+          if (distanceVec) {
+            didReachToValue = true;
+            const CGFloat *distanceValues = distanceVec->data();
+            for (NSUInteger idx = 0; idx < valueCount; idx++) {
+              didReachToValue &= (signbit(distance[idx]) != signbit(distanceValues[idx]));
+            }
+          }
+        }
+      }
+
+      if (didReachToValue) {
+        handleDidReachToValue();
+      }
+    }
+  }
+
+  void handleDidReachToValue() {
+    didReachToValue = true;
+
+    if (delegateDidReachToValue) {
+      ActionEnabler enabler;
+      [delegate pop_animationDidReachToValue:self];
+    }
+
+    POPAnimationDidReachToValueBlock block = animationDidReachToValueBlock;
+    if (block != NULL) {
+      ActionEnabler enabler;
+      block(self);
+    }
+
+    if (tracing) {
+      [tracer didReachToValue:POPBox(currentValue(), valueType, true)];
+    }
+  }
+
+  void readObjectValue(VectorRef *ptrVec, id obj)
+  {
+    // use current object value as from value
+    POPAnimatablePropertyReadBlock read = property.readBlock;
+    if (NULL != read) {
+
+      Vector4r vec = read_values(read, obj, valueCount);
+      *ptrVec = VectorRef(Vector::new_vector(valueCount, vec));
+
+      if (tracing) {
+        [tracer readPropertyValue:POPBox(*ptrVec, valueType, true)];
+      }
+    }
+  }
+
+  virtual void willRun(bool started, id obj) {
+    // ensure from value initialized
+    if (NULL == fromVec) {
+      readObjectValue(&fromVec, obj);
+    }
+
+    // ensure to value initialized
+    if (NULL == toVec) {
+      // compute decay to value
+      if (kPOPAnimationDecay == type) {
+        [self toValue];
+      } else {
+        // read to value
+        readObjectValue(&toVec, obj);
+      }
+    }
+
+    // handle one time value initialization on start
+    if (started) {
+
+      // initialize current vec
+      if (!currentVec) {
+        currentVec = VectorRef(Vector::new_vector(valueCount, NULL));
+
+        // initialize current value with from value
+        // only do this on initial creation to avoid overwriting current value
+        // on paused animation continuation
+        if (currentVec && fromVec) {
+          *currentVec = *fromVec;
+        }
+      }
+
+      // ensure velocity values
+      if (!velocityVec) {
+        velocityVec = VectorRef(Vector::new_vector(valueCount, NULL));
+      }
+      if (!originalVelocityVec) {
+        originalVelocityVec = VectorRef(Vector::new_vector(valueCount, NULL));
+      }
+    }
+
+    // ensure distance value initialized
+    // depends on current value set on one time start
+    if (NULL == distanceVec) {
+
+      // not yet started animations may not have current value
+      VectorRef fromVec2 = NULL != currentVec ? currentVec : fromVec;
+
+      if (fromVec2 && toVec) {
+        Vector4r distance = toVec->vector4r();
+        distance -= fromVec2->vector4r();
+
+        if (0 != distance.squaredNorm()) {
+          distanceVec = VectorRef(Vector::new_vector(valueCount, distance));
+        }
+      }
+    }
+  }
+
+  virtual void reset(bool all) {
+    _POPAnimationState::reset(all);
+
+    if (all) {
+      currentVec = NULL;
+      previousVec = NULL;
+      previous2Vec = NULL;
+    }
+    progress = 0;
+    resetProgressMarkerState();
+    didReachToValue = false;
+    distanceVec = NULL;
+  }
+
+  void clampCurrentValue(NSUInteger clamp)
+  {
+    if (kPOPAnimationClampNone == clamp)
+      return;
+
+    // Clamp all vector values
+    CGFloat *currentValues = currentVec->data();
+    const CGFloat *fromValues = fromVec->data();
+    const CGFloat *toValues = toVec->data();
+
+    for (NSUInteger idx = 0; idx < valueCount; idx++) {
+      clampValue(currentValues[idx], fromValues[idx], toValues[idx], clamp);
+    }
+  }
+
+  void clampCurrentValue()
+  {
+    clampCurrentValue(clampMode);
+  }
+};
+
+typedef struct _POPPropertyAnimationState POPPropertyAnimationState;
+
+@interface POPPropertyAnimation ()
+
+@end
+

pop/POPSpringAnimation.h

@@ -0,0 +1,67 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <pop/POPPropertyAnimation.h>
+
+/**
+ @abstract A concrete spring animation class.
+ @discussion Animation is achieved through modeling spring dynamics.
+ */
+@interface POPSpringAnimation : POPPropertyAnimation
+
+/**
+ @abstract The designated initializer.
+ @returns An instance of a spring animation.
+ */
++ (instancetype)animation;
+
+/**
+ @abstract Convenience initializer that returns an animation with animatable property of name.
+ @param name The name of the animatable property.
+ @returns An instance of a spring animation configured with specified animatable property.
+ */
++ (instancetype)animationWithPropertyNamed:(NSString *)name;
+
+/**
+ @abstract The current velocity value.
+ @discussion Set before animation start to account for initial velocity. Expressed in change of value units per second.
+ */
+@property (copy, nonatomic) id velocity;
+
+/**
+ @abstract The effective bounciness.
+ @discussion Use in conjunction with 'springSpeed' to change animation effect. Values are converted into corresponding dynamics constants. Higher values increase spring movement range resulting in more oscillations and springiness. Defined as a value in the range [0, 20]. Defaults to 4.
+ */
+@property (assign, nonatomic) CGFloat springBounciness;
+
+/**
+ @abstract The effective speed.
+ @discussion Use in conjunction with 'springBounciness' to change animation effect. Values are converted into corresponding dynamics constants. Higher values increase the dampening power of the spring resulting in a faster initial velocity and more rapid bounce slowdown. Defined as a value in the range [0, 20]. Defaults to 12.
+ */
+@property (assign, nonatomic) CGFloat springSpeed;
+
+/**
+ @abstract The tension used in the dynamics simulation.
+ @discussion Can be used over bounciness and speed for finer grain tweaking of animation effect.
+ */
+@property (assign, nonatomic) CGFloat dynamicsTension;
+
+/**
+ @abstract The friction used in the dynamics simulation.
+ @discussion Can be used over bounciness and speed for finer grain tweaking of animation effect.
+ */
+@property (assign, nonatomic) CGFloat dynamicsFriction;
+
+/**
+ @abstract The mass used in the dynamics simulation.
+ @discussion Can be used over bounciness and speed for finer grain tweaking of animation effect.
+ */
+@property (assign, nonatomic) CGFloat dynamicsMass;
+
+@end

pop/POPSpringAnimation.mm

@@ -0,0 +1,192 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPSpringAnimationInternal.h"
+
+@implementation POPSpringAnimation
+
+#pragma mark - Lifecycle
+
+#undef __state
+#define __state ((POPSpringAnimationState *)_state)
+
++ (instancetype)animation
+{
+  return [[self alloc] init];
+}
+
++ (instancetype)animationWithPropertyNamed:(NSString *)aName
+{
+  POPSpringAnimation *anim = [self animation];
+  anim.property = [POPAnimatableProperty propertyWithName:aName];
+  return anim;
+}
+
+- (void)_initState
+{
+  _state = new POPSpringAnimationState(self);
+}
+
+- (id)init
+{
+  self = [super _init];
+  if (nil != self) {
+    __state->solver = new SpringSolver4d(1, 1, 1);
+    __state->updatedDynamicsThreshold();
+    __state->updatedBouncinessAndSpeed();
+  }
+  return self;
+}
+
+- (void)dealloc
+{
+  if (__state) {
+    delete __state->solver;
+    __state->solver = NULL;
+  }
+}
+
+#pragma mark - Properties
+
+- (id)velocity
+{
+  return POPBox(__state->velocityVec, __state->valueType);
+}
+
+- (void)setVelocity:(id)aValue
+{
+  POPPropertyAnimationState *s = __state;
+  VectorRef vec = POPUnbox(aValue, s->valueType, s->valueCount, YES);
+  VectorRef origVec = POPUnbox(aValue, s->valueType, s->valueCount, YES);
+  if (!vec_equal(vec, s->velocityVec)) {
+    s->velocityVec = vec;
+    s->originalVelocityVec = origVec;
+
+    if (s->tracing) {
+      [s->tracer updateVelocity:aValue];
+    }
+  }
+}
+
+DEFINE_RW_PROPERTY(POPSpringAnimationState, dynamicsTension, setDynamicsTension:, CGFloat, [self _updatedDynamicsTension];);
+DEFINE_RW_PROPERTY(POPSpringAnimationState, dynamicsFriction, setDynamicsFriction:, CGFloat, [self _updatedDynamicsFriction];);
+DEFINE_RW_PROPERTY(POPSpringAnimationState, dynamicsMass, setDynamicsMass:, CGFloat, [self _updatedDynamicsMass];);
+
+FB_PROPERTY_GET(POPSpringAnimationState, springSpeed, CGFloat);
+- (void)setSpringSpeed:(CGFloat)aFloat
+{
+  POPSpringAnimationState *s = __state;
+  if (s->userSpecifiedDynamics || aFloat != s->springSpeed) {
+    s->springSpeed = aFloat;
+    s->userSpecifiedDynamics = false;
+    s->updatedBouncinessAndSpeed();
+    if (s->tracing) {
+      [s->tracer updateSpeed:aFloat];
+    }
+  }
+}
+
+FB_PROPERTY_GET(POPSpringAnimationState, springBounciness, CGFloat);
+- (void)setSpringBounciness:(CGFloat)aFloat
+{
+  POPSpringAnimationState *s = __state;
+  if (s->userSpecifiedDynamics || aFloat != s->springBounciness) {
+    s->springBounciness = aFloat;
+    s->userSpecifiedDynamics = false;
+    s->updatedBouncinessAndSpeed();
+    if (s->tracing) {
+      [s->tracer updateBounciness:aFloat];
+    }
+  }
+}
+
+- (SpringSolver4d *)solver
+{
+  return __state->solver;
+}
+
+- (void)setSolver:(SpringSolver4d *)aSolver
+{
+  if (aSolver != __state->solver) {
+    if (__state->solver) {
+      delete(__state->solver);
+    }
+    __state->solver = aSolver;
+  }
+}
+
+#pragma mark - Utility
+
+- (void)_updatedDynamicsTension
+{
+  __state->userSpecifiedDynamics = true;
+  if(__state->tracing) {
+    [__state->tracer updateTension:__state->dynamicsTension];
+  }
+  __state->updatedDynamics();
+}
+
+- (void)_updatedDynamicsFriction
+{
+  __state->userSpecifiedDynamics = true;
+  if(__state->tracing) {
+    [__state->tracer updateFriction:__state->dynamicsFriction];
+  }
+  __state->updatedDynamics();
+}
+
+- (void)_updatedDynamicsMass
+{
+  __state->userSpecifiedDynamics = true;
+  if(__state->tracing) {
+    [__state->tracer updateMass:__state->dynamicsMass];
+  }
+  __state->updatedDynamics();
+}
+
+- (void)_appendDescription:(NSMutableString *)s debug:(BOOL)debug
+{
+  [super _appendDescription:s debug:debug];
+
+  if (debug) {
+    if (_state->userSpecifiedDynamics) {
+      [s appendFormat:@"; dynamics = (tension:%f, friction:%f, mass:%f)", __state->dynamicsTension, __state->dynamicsFriction, __state->dynamicsMass];
+    } else {
+      [s appendFormat:@"; bounciness = %f; speed = %f", __state->springBounciness, __state->springSpeed];
+    }
+  }
+}
+
+@end
+
+@implementation POPSpringAnimation (NSCopying)
+
+- (instancetype)copyWithZone:(NSZone *)zone {
+  
+  POPSpringAnimation *copy = [super copyWithZone:zone];
+  
+  if (copy) {
+    id velocity = POPBox(__state->originalVelocityVec, __state->valueType);
+    
+    // If velocity never gets set, then POPBox will return nil, messing up __state->valueCount.
+    if (velocity) {
+      copy.velocity = velocity;
+    }
+    
+    copy.springBounciness = self.springBounciness;
+    copy.springSpeed = self.springSpeed;
+    copy.dynamicsTension = self.dynamicsTension;
+    copy.dynamicsFriction = self.dynamicsFriction;
+    copy.dynamicsMass = self.dynamicsMass;
+  }
+  
+  return copy;
+}
+
+@end

pop/POPSpringAnimationInternal.h

@@ -0,0 +1,132 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <cmath>
+
+#import "POPAnimationExtras.h"
+#import "POPPropertyAnimationInternal.h"
+
+struct _POPSpringAnimationState : _POPPropertyAnimationState
+{
+  SpringSolver4d *solver;
+  CGFloat springSpeed;
+  CGFloat springBounciness; // normalized springiness
+  CGFloat dynamicsTension;  // tension
+  CGFloat dynamicsFriction; // friction
+  CGFloat dynamicsMass;     // mass
+
+  _POPSpringAnimationState(id __unsafe_unretained anim) : _POPPropertyAnimationState(anim),
+  solver(nullptr),
+  springSpeed(12.),
+  springBounciness(4.),
+  dynamicsTension(0),
+  dynamicsFriction(0),
+  dynamicsMass(0)
+  {
+    type = kPOPAnimationSpring;
+  }
+
+  bool hasConverged()
+  {
+    NSUInteger count = valueCount;
+    if (shouldRound()) {
+      return vec_equal(previous2Vec, previousVec) && vec_equal(previousVec, toVec);
+    } else {
+      if (!previousVec || !previous2Vec)
+        return false;
+
+      CGFloat t  = dynamicsThreshold / 5;
+
+      const CGFloat *toValues = toVec->data();
+      const CGFloat *previousValues = previousVec->data();
+      const CGFloat *previous2Values = previous2Vec->data();
+
+      for (NSUInteger idx = 0; idx < count; idx++) {
+          if ((std::abs(toValues[idx] - previousValues[idx]) >= t) || (std::abs(previous2Values[idx] - previousValues[idx]) >= t)) {
+          return false;
+        }
+      }
+      return true;
+    }
+  }
+
+  bool isDone() {
+    if (_POPPropertyAnimationState::isDone()) {
+      return true;
+    }
+    return solver->started() && (hasConverged() || solver->hasConverged());
+  }
+
+  void updatedDynamics()
+  {
+    if (NULL != solver) {
+      solver->setConstants(dynamicsTension, dynamicsFriction, dynamicsMass);
+    }
+  }
+
+  void updatedDynamicsThreshold()
+  {
+    _POPPropertyAnimationState::updatedDynamicsThreshold();
+    if (NULL != solver) {
+      solver->setThreshold(dynamicsThreshold);
+    }
+  }
+
+  void updatedBouncinessAndSpeed() {
+    [POPSpringAnimation convertBounciness:springBounciness speed:springSpeed toTension:&dynamicsTension friction:&dynamicsFriction mass:&dynamicsMass];
+    updatedDynamics();
+  }
+
+  bool advance(CFTimeInterval time, CFTimeInterval dt, id obj) {
+    // advance past not yet initialized animations
+    if (NULL == currentVec) {
+      return false;
+    }
+
+    CFTimeInterval localTime = time - startTime;
+
+    Vector4d value = vector4d(currentVec);
+    Vector4d toValue = vector4d(toVec);
+    Vector4d velocity = vector4d(velocityVec);
+
+    SSState4d state;
+    state.p = toValue - value;
+
+    // the solver assumes a spring of size zero
+    // flip the velocity from user perspective to solver perspective
+    state.v = velocity * -1;
+
+    solver->advance(state, localTime, dt);
+    value = toValue - state.p;
+
+    // flip velocity back to user perspective
+    velocity = state.v * -1;
+
+    *currentVec = value;
+
+    if (velocityVec) {
+      *velocityVec = velocity;
+    }
+
+    clampCurrentValue();
+
+    return true;
+  }
+
+  virtual void reset(bool all) {
+    _POPPropertyAnimationState::reset(all);
+
+    if (solver) {
+      solver->setConstants(dynamicsTension, dynamicsFriction, dynamicsMass);
+      solver->reset();
+    }
+  }
+};
+
+typedef struct _POPSpringAnimationState POPSpringAnimationState;

pop/POPSpringSolver.h

@@ -0,0 +1,190 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+ 
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import <Foundation/Foundation.h>
+
+#import <pop/POPVector.h>
+
+namespace POP {
+  
+  template <typename T>
+  struct SSState
+  {
+    T p;
+    T v;
+  };
+  
+  template <typename T>
+  struct SSDerivative
+  {
+    T dp;
+    T dv;
+  };
+  
+  typedef SSState<Vector4d> SSState4d;
+  typedef SSDerivative<Vector4d> SSDerivative4d;
+  
+  const CFTimeInterval solverDt = 0.001f;
+  const CFTimeInterval maxSolverDt = 30.0f;
+  
+  /**
+   Templated spring solver class.
+   */
+  template <typename T>
+  class SpringSolver
+  {
+    double _k; // stiffness
+    double _b; // dampening
+    double _m; // mass
+    
+    double _tp; // threshold
+    double _tv; // threshold velocity
+    double _ta; // threshold acceleration
+    
+    CFTimeInterval _accumulatedTime;
+    SSState<T> _lastState;
+    T _lastDv;
+    bool _started;
+    
+  public:
+    SpringSolver(double k, double b, double m = 1) : _k(k), _b(b), _m(m), _started(false)
+    {
+      _accumulatedTime = 0;
+      _lastState.p = T::Zero();
+      _lastState.v = T::Zero();
+      _lastDv = T::Zero();
+      setThreshold(1.);
+    }
+    
+    ~SpringSolver()
+    {
+    }
+    
+    bool started()
+    {
+      return _started;
+    }
+    
+    void setConstants(double k, double b, double m)
+    {
+      _k = k;
+      _b = b;
+      _m = m;
+    }
+    
+    void setThreshold(double t)
+    {
+      _tp = t / 2;          // half a unit
+      _tv = 25.0 * t;       // 5 units per second, squared for comparison
+      _ta = 625.0 * t * t;  // 5 units per second squared, squared for comparison
+    }
+    
+    T acceleration(const SSState<T> &state, double t)
+    {
+      return state.p*(-_k/_m) - state.v*(_b/_m);
+    }
+    
+    SSDerivative<T> evaluate(const SSState<T> &initial, double t)
+    {
+      SSDerivative<T> output;
+      output.dp = initial.v;
+      output.dv = acceleration(initial, t);
+      return output;
+    }
+    
+    SSDerivative<T> evaluate(const SSState<T> &initial, double t, double dt, const SSDerivative<T> &d)
+    {
+      SSState<T> state;
+      state.p = initial.p + d.dp*dt;
+      state.v = initial.v + d.dv*dt;
+      SSDerivative<T> output;
+      output.dp = state.v;
+      output.dv = acceleration(state, t+dt);
+      return output;
+    }
+    
+    void integrate(SSState<T> &state, double t, double dt)
+    {
+      SSDerivative<T> a = evaluate(state, t);
+      SSDerivative<T> b = evaluate(state, t, dt*0.5, a);
+      SSDerivative<T> c = evaluate(state, t, dt*0.5, b);
+      SSDerivative<T> d = evaluate(state, t, dt, c);
+      
+      T dpdt = (a.dp + (b.dp + c.dp)*2.0 + d.dp) * (1.0/6.0);
+      T dvdt = (a.dv + (b.dv + c.dv)*2.0 + d.dv) * (1.0/6.0);
+      
+      state.p = state.p + dpdt*dt;
+      state.v = state.v + dvdt*dt;
+      
+      _lastDv = dvdt;
+    }
+    
+    SSState<T> interpolate(const SSState<T> &previous, const SSState<T> &current, double alpha)
+    {
+      SSState<T> state;
+      state.p = current.p*alpha + previous.p*(1-alpha);
+      state.v = current.v*alpha + previous.v*(1-alpha);
+      return state;
+    }
+    
+    void advance(SSState<T> &state, double t, double dt)
+    {
+      _started = true;
+      
+      if (dt > maxSolverDt) {
+        // excessive time step, force shut down
+        _lastDv = _lastState.v = _lastState.p = T::Zero();
+      } else {
+        _accumulatedTime += dt;
+        
+        SSState<T> previousState = state, currentState = state;
+        while (_accumulatedTime >= solverDt) {
+          previousState = currentState;
+          this->integrate(currentState, t, solverDt);
+          t += solverDt;
+          _accumulatedTime -= solverDt;
+        }
+        CFTimeInterval alpha = _accumulatedTime / solverDt;
+        _lastState = state = this->interpolate(previousState, currentState, alpha);
+      }
+    }
+    
+    bool hasConverged()
+    {
+      if (!_started) {
+        return false;
+      }
+      
+      for (size_t idx = 0; idx < _lastState.p.size(); idx++) {
+        if (fabs(_lastState.p(idx)) >= _tp) {
+          return false;
+        }
+      }
+      
+      return (_lastState.v.squaredNorm() < _tv) && (_lastDv.squaredNorm() < _ta);
+    }
+    
+    void reset()
+    {
+      _accumulatedTime = 0;
+      _lastState.p = T::Zero();
+      _lastState.v = T::Zero();
+      _lastDv = T::Zero();
+      _started = false;
+    }
+  };
+
+  /**
+   Convenience spring solver type definitions.
+   */
+  typedef SpringSolver<Vector2d> SpringSolver2d;
+  typedef SpringSolver<Vector3d> SpringSolver3d;
+  typedef SpringSolver<Vector4d> SpringSolver4d;
+}
+

pop/POPVector.h

@@ -0,0 +1,396 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#ifndef __POP__FBVector__
+#define __POP__FBVector__
+
+#ifdef __cplusplus
+
+#include <iostream>
+#include <vector>
+
+#import <objc/NSObjCRuntime.h>
+
+#import <CoreGraphics/CoreGraphics.h>
+#import <Foundation/NSException.h>
+
+#import "POPDefines.h"
+
+#if SCENEKIT_SDK_AVAILABLE
+#import <SceneKit/SceneKit.h>
+#endif
+
+#if TARGET_OS_IPHONE
+#import <UIKit/UIKit.h>
+#endif
+
+namespace POP {
+
+  /** Fixed two-size vector class */
+  template <typename T>
+  struct Vector2
+  {
+  private:
+    typedef T Vector2<T>::* const _data[2];
+    static const _data _v;
+
+  public:
+    T x;
+    T y;
+
+    // Zero vector
+    static const Vector2 Zero() { return Vector2(0); }
+
+    // Constructors
+    Vector2() {}
+    explicit Vector2(T v) { x = v; y = v; };
+    explicit Vector2(T x0, T y0) : x(x0), y(y0) {};
+    explicit Vector2(const CGPoint &p) : x(p.x), y (p.y) {}
+    explicit Vector2(const CGSize &s) : x(s.width), y (s.height) {}
+
+    // Copy constructor
+    template<typename U> explicit Vector2(const Vector2<U> &v) : x(v.x), y(v.y) {}
+
+    // Index operators
+    const T& operator[](size_t i) const { return this->*_v[i]; }
+    T& operator[](size_t i) { return this->*_v[i]; }
+    const T& operator()(size_t i) const { return this->*_v[i]; }
+    T& operator()(size_t i) { return this->*_v[i]; }
+
+    // Backing data
+    T * data() { return &(this->*_v[0]); }
+    const T * data() const { return &(this->*_v[0]); }
+
+    // Size
+    inline size_t size() const { return 2; }
+
+    // Assignment
+    Vector2 &operator= (T v) { x = v; y = v; return *this;}
+    template<typename U> Vector2 &operator= (const Vector2<U> &v) { x = v.x; y = v.y; return *this;}
+
+    // Negation
+    Vector2 operator- (void) const { return Vector2<T>(-x, -y); }
+
+    // Equality
+    bool operator== (T v) const { return (x == v && y == v); }
+    bool operator== (const Vector2 &v) const { return (x == v.x && y == v.y); }
+
+    // Inequality
+    bool operator!= (T v) const {return (x != v || y != v); }
+    bool operator!= (const Vector2 &v) const { return (x != v.x || y != v.y); }
+
+    // Scalar Math
+    Vector2 operator+ (T v) const { return Vector2(x + v, y + v); }
+    Vector2 operator- (T v) const { return Vector2(x - v, y - v); }
+    Vector2 operator* (T v) const { return Vector2(x * v, y * v); }
+    Vector2 operator/ (T v) const { return Vector2(x / v, y / v); }
+    Vector2 &operator+= (T v) { x += v; y += v; return *this; };
+    Vector2 &operator-= (T v) { x -= v; y -= v; return *this; };
+    Vector2 &operator*= (T v) { x *= v; y *= v; return *this; };
+    Vector2 &operator/= (T v) { x /= v; y /= v; return *this; };
+
+    // Vector Math
+    Vector2 operator+ (const Vector2 &v) const { return Vector2(x + v.x, y + v.y); }
+    Vector2 operator- (const Vector2 &v) const { return Vector2(x - v.x, y - v.y); }
+    Vector2 &operator+= (const Vector2 &v) { x += v.x; y += v.y; return *this; };
+    Vector2 &operator-= (const Vector2 &v) { x -= v.x; y -= v.y; return *this; };
+
+    // Norms
+    CGFloat norm() const { return sqrtr(squaredNorm()); }
+    CGFloat squaredNorm() const { return x * x + y * y; }
+
+    // Cast
+    template<typename U> Vector2<U> cast() const { return Vector2<U>(x, y); }
+    CGPoint cg_point() const { return CGPointMake(x, y); };
+  };
+
+  template<typename T>
+  const typename Vector2<T>::_data Vector2<T>::_v = { &Vector2<T>::x, &Vector2<T>::y };
+
+  /** Fixed three-size vector class */
+  template <typename T>
+  struct Vector3
+  {
+  private:
+    typedef T Vector3<T>::* const _data[3];
+    static const _data _v;
+
+  public:
+    T x;
+    T y;
+    T z;
+
+    // Zero vector
+    static const Vector3 Zero() { return Vector3(0); };
+
+    // Constructors
+    Vector3() {}
+    explicit Vector3(T v) : x(v), y(v), z(v) {};
+    explicit Vector3(T x0, T y0, T z0) : x(x0), y(y0), z(z0) {};
+
+    // Copy constructor
+    template<typename U> explicit Vector3(const Vector3<U> &v) : x(v.x), y(v.y), z(v.z) {}
+
+    // Index operators
+    const T& operator[](size_t i) const { return this->*_v[i]; }
+    T& operator[](size_t i) { return this->*_v[i]; }
+    const T& operator()(size_t i) const { return this->*_v[i]; }
+    T& operator()(size_t i) { return this->*_v[i]; }
+
+    // Backing data
+    T * data() { return &(this->*_v[0]); }
+    const T * data() const { return &(this->*_v[0]); }
+
+    // Size
+    inline size_t size() const { return 3; }
+
+    // Assignment
+    Vector3 &operator= (T v) { x = v; y = v; z = v; return *this;}
+    template<typename U> Vector3 &operator= (const Vector3<U> &v) { x = v.x; y = v.y; z = v.z; return *this;}
+
+    // Negation
+    Vector3 operator- (void) const { return Vector3<T>(-x, -y, -z); }
+
+    // Equality
+    bool operator== (T v) const { return (x == v && y == v && z = v); }
+    bool operator== (const Vector3 &v) const { return (x == v.x && y == v.y && z == v.z); }
+
+    // Inequality
+    bool operator!= (T v) const {return (x != v || y != v || z != v); }
+    bool operator!= (const Vector3 &v) const { return (x != v.x || y != v.y || z != v.z); }
+
+    // Scalar Math
+    Vector3 operator+ (T v) const { return Vector3(x + v, y + v, z + v); }
+    Vector3 operator- (T v) const { return Vector3(x - v, y - v, z - v); }
+    Vector3 operator* (T v) const { return Vector3(x * v, y * v, z * v); }
+    Vector3 operator/ (T v) const { return Vector3(x / v, y / v, z / v); }
+    Vector3 &operator+= (T v) { x += v; y += v; z += v; return *this; };
+    Vector3 &operator-= (T v) { x -= v; y -= v; z -= v; return *this; };
+    Vector3 &operator*= (T v) { x *= v; y *= v; z *= v; return *this; };
+    Vector3 &operator/= (T v) { x /= v; y /= v; z /= v; return *this; };
+
+    // Vector Math
+    Vector3 operator+ (const Vector3 &v) const { return Vector3(x + v.x, y + v.y, z + v.z); }
+    Vector3 operator- (const Vector3 &v) const { return Vector3(x - v.x, y - v.y, z - v.z); }
+    Vector3 &operator+= (const Vector3 &v) { x += v.x; y += v.y; z += v.z; return *this; };
+    Vector3 &operator-= (const Vector3 &v) { x -= v.x; y -= v.y; z -= v.z; return *this; };
+
+    // Norms
+    CGFloat norm() const { return sqrtr(squaredNorm()); }
+    CGFloat squaredNorm() const { return x * x + y * y + z * z; }
+
+    // Cast
+    template<typename U> Vector3<U> cast() const { return Vector3<U>(x, y, z); }
+  };
+
+  template<typename T>
+  const typename Vector3<T>::_data Vector3<T>::_v = { &Vector3<T>::x, &Vector3<T>::y, &Vector3<T>::z };
+
+  /** Fixed four-size vector class */
+  template <typename T>
+  struct Vector4
+  {
+  private:
+    typedef T Vector4<T>::* const _data[4];
+    static const _data _v;
+
+  public:
+    T x;
+    T y;
+    T z;
+    T w;
+
+    // Zero vector
+    static const Vector4 Zero() { return Vector4(0); };
+
+    // Constructors
+    Vector4() {}
+    explicit Vector4(T v) : x(v), y(v), z(v), w(v) {};
+    explicit Vector4(T x0, T y0, T z0, T w0) : x(x0), y(y0), z(z0), w(w0) {};
+
+    // Copy constructor
+    template<typename U> explicit Vector4(const Vector4<U> &v) : x(v.x), y(v.y), z(v.z), w(v.w) {}
+
+    // Index operators
+    const T& operator[](size_t i) const { return this->*_v[i]; }
+    T& operator[](size_t i) { return this->*_v[i]; }
+    const T& operator()(size_t i) const { return this->*_v[i]; }
+    T& operator()(size_t i) { return this->*_v[i]; }
+
+    // Backing data
+    T * data() { return &(this->*_v[0]); }
+    const T * data() const { return &(this->*_v[0]); }
+
+    // Size
+    inline size_t size() const { return 4; }
+
+    // Assignment
+    Vector4 &operator= (T v) { x = v; y = v; z = v; w = v; return *this;}
+    template<typename U> Vector4 &operator= (const Vector4<U> &v) { x = v.x; y = v.y; z = v.z; w = v.w; return *this;}
+
+    // Negation
+    Vector4 operator- (void) const { return Vector4<T>(-x, -y, -z, -w); }
+
+    // Equality
+    bool operator== (T v) const { return (x == v && y == v && z = v, w = v); }
+    bool operator== (const Vector4 &v) const { return (x == v.x && y == v.y && z == v.z && w == v.w); }
+
+    // Inequality
+    bool operator!= (T v) const {return (x != v || y != v || z != v || w != v); }
+    bool operator!= (const Vector4 &v) const { return (x != v.x || y != v.y || z != v.z || w != v.w); }
+
+    // Scalar Math
+    Vector4 operator+ (T v) const { return Vector4(x + v, y + v, z + v, w + v); }
+    Vector4 operator- (T v) const { return Vector4(x - v, y - v, z - v, w - v); }
+    Vector4 operator* (T v) const { return Vector4(x * v, y * v, z * v, w * v); }
+    Vector4 operator/ (T v) const { return Vector4(x / v, y / v, z / v, w / v); }
+    Vector4 &operator+= (T v) { x += v; y += v; z += v; w += v; return *this; };
+    Vector4 &operator-= (T v) { x -= v; y -= v; z -= v; w -= v; return *this; };
+    Vector4 &operator*= (T v) { x *= v; y *= v; z *= v; w *= v; return *this; };
+    Vector4 &operator/= (T v) { x /= v; y /= v; z /= v; w /= v; return *this; };
+
+    // Vector Math
+    Vector4 operator+ (const Vector4 &v) const { return Vector4(x + v.x, y + v.y, z + v.z, w + v.w); }
+    Vector4 operator- (const Vector4 &v) const { return Vector4(x - v.x, y - v.y, z - v.z, w - v.w); }
+    Vector4 &operator+= (const Vector4 &v) { x += v.x; y += v.y; z += v.z; w += v.w; return *this; };
+    Vector4 &operator-= (const Vector4 &v) { x -= v.x; y -= v.y; z -= v.z; w -= v.w; return *this; };
+
+    // Norms
+    CGFloat norm() const { return sqrtr(squaredNorm()); }
+    CGFloat squaredNorm() const { return x * x + y * y + z * z + w * w; }
+
+    // Cast
+    template<typename U> Vector4<U> cast() const { return Vector4<U>(x, y, z, w); }
+  };
+
+  template<typename T>
+  const typename Vector4<T>::_data Vector4<T>::_v = { &Vector4<T>::x, &Vector4<T>::y, &Vector4<T>::z, &Vector4<T>::w };
+
+  /** Convenience typedefs */
+  typedef Vector2<float> Vector2f;
+  typedef Vector2<double> Vector2d;
+  typedef Vector2<CGFloat> Vector2r;
+  typedef Vector3<float> Vector3f;
+  typedef Vector3<double> Vector3d;
+  typedef Vector3<CGFloat> Vector3r;
+  typedef Vector4<float> Vector4f;
+  typedef Vector4<double> Vector4d;
+  typedef Vector4<CGFloat> Vector4r;
+
+  /** Variable-sized vector class */
+  class Vector
+  {
+    size_t _count;
+    CGFloat *_values;
+
+  private:
+    Vector(size_t);
+    Vector(const Vector& other);
+
+  public:
+    ~Vector();
+
+    // Creates a new vector instance of count with values. Initializing a vector of size 0 returns NULL.
+    static Vector *new_vector(NSUInteger count, const CGFloat *values);
+
+    // Creates a new vector given a pointer to another. Can return NULL.
+    static Vector *new_vector(const Vector * const other);
+
+    // Creates a variable size vector given a static vector and count.
+    static Vector *new_vector(NSUInteger count, Vector4r vec);
+
+    // Size of vector
+    NSUInteger size() const { return _count; }
+
+    // Returns array of values
+    CGFloat *data () { return _values; }
+    const CGFloat *data () const { return _values; };
+
+    // Vector2r support
+    Vector2r vector2r() const;
+
+    // Vector4r support
+    Vector4r vector4r() const;
+
+    // CGFloat support
+    static Vector *new_cg_float(CGFloat f);
+
+    // CGPoint support
+    CGPoint cg_point() const;
+    static Vector *new_cg_point(const CGPoint &p);
+
+    // CGSize support
+    CGSize cg_size() const;
+    static Vector *new_cg_size(const CGSize &s);
+
+    // CGRect support
+    CGRect cg_rect() const;
+    static Vector *new_cg_rect(const CGRect &r);
+
+#if TARGET_OS_IPHONE
+    // UIEdgeInsets support
+    UIEdgeInsets ui_edge_insets() const;
+    static Vector *new_ui_edge_insets(const UIEdgeInsets &i);
+#endif
+
+    // CGAffineTransform support
+    CGAffineTransform cg_affine_transform() const;
+    static Vector *new_cg_affine_transform(const CGAffineTransform &t);
+
+    // CGColorRef support
+    CGColorRef cg_color() const CF_RETURNS_RETAINED;
+    static Vector *new_cg_color(CGColorRef color);
+
+#if SCENEKIT_SDK_AVAILABLE
+    // SCNVector3 support
+    SCNVector3 scn_vector3() const;
+    static Vector *new_scn_vector3(const SCNVector3 &vec3);
+
+    // SCNVector4 support
+    SCNVector4 scn_vector4() const;
+    static Vector *new_scn_vector4(const SCNVector4 &vec4);
+#endif
+
+    // operator overloads
+    CGFloat &operator[](size_t i) const {
+      NSCAssert(size() > i, @"unexpected vector size:%lu", (unsigned long)size());
+      return _values[i];
+    }
+
+    // Returns the mathematical length
+    CGFloat norm() const;
+    CGFloat squaredNorm() const;
+
+    // Round to nearest sub
+    void subRound(CGFloat sub);
+
+    // Returns string description
+    NSString * toString() const;
+
+    // Operator overloads
+    template<typename U> Vector& operator= (const Vector4<U>& other) {
+      size_t count = MIN(_count, other.size());
+      for (size_t i = 0; i < count; i++) {
+        _values[i] = other[i];
+      }
+      return *this;
+    }
+    Vector& operator= (const Vector& other);
+    void swap(Vector &first, Vector &second);
+    bool operator==(const Vector &other) const;
+    bool operator!=(const Vector &other) const;
+  };
+
+  /** Convenience typedefs */
+  typedef std::shared_ptr<Vector> VectorRef;
+  typedef std::shared_ptr<const Vector> VectorConstRef;
+
+}
+#endif /* __cplusplus */
+#endif /* defined(__POP__FBVector__) */

pop/POPVector.mm

@@ -0,0 +1,335 @@
+/**
+ Copyright (c) 2014-present, Facebook, Inc.
+ All rights reserved.
+
+ This source code is licensed under the BSD-style license found in the
+ LICENSE file in the root directory of this source tree. An additional grant
+ of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "POPVector.h"
+
+#import "POPDefines.h"
+#import "POPCGUtils.h"
+#import "POPMath.h"
+
+namespace POP
+{
+
+  Vector::Vector(const size_t count)
+  {
+    _count = count;
+    _values = 0 != count ? (CGFloat *)calloc(count, sizeof(CGFloat)) : NULL;
+  }
+
+  Vector::Vector(const Vector& other)
+  {
+    _count = other.size();
+    _values = 0 != _count ? (CGFloat *)calloc(_count, sizeof(CGFloat)) : NULL;
+    if (0 != _count) {
+      memcpy(_values, other.data(), _count * sizeof(CGFloat));
+    }
+  }
+
+  Vector::~Vector()
+  {
+    if (NULL != _values) {
+      free(_values);
+      _values = NULL;
+    }
+    _count = 0;
+  }
+
+  void Vector::swap(Vector &first, Vector &second)
+  {
+    using std::swap;
+    swap(first._count, second._count);
+    swap(first._values, second._values);
+  }
+
+  Vector& Vector::operator=(const Vector& other)
+  {
+    Vector temp(other);
+    swap(*this, temp);
+    return *this;
+  }
+
+  bool Vector::operator==(const Vector &other) const {
+    if (_count != other.size()) {
+      return false;
+    }
+
+    const CGFloat * const values = other.data();
+
+    for (NSUInteger idx = 0; idx < _count; idx++) {
+      if (_values[idx] != values[idx]) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  bool Vector::operator!=(const Vector &other) const {
+    if (_count == other.size()) {
+      return false;
+    }
+
+    const CGFloat * const values = other.data();
+
+    for (NSUInteger idx = 0; idx < _count; idx++) {
+      if (_values[idx] != values[idx]) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  Vector *Vector::new_vector(NSUInteger count, const CGFloat *values)
+  {
+    if (0 == count) {
+      return NULL;
+    }
+
+    Vector *v = new Vector(count);
+    if (NULL != values) {
+      memcpy(v->_values, values, count * sizeof(CGFloat));
+    }
+    return v;
+  }
+
+  Vector *Vector::new_vector(const Vector * const other)
+  {
+    if (NULL == other) {
+      return NULL;
+    }
+
+    return Vector::new_vector(other->size(), other->data());
+  }
+
+  Vector *Vector::new_vector(NSUInteger count, Vector4r vec)
+  {
+    if (0 == count) {
+      return NULL;
+    }
+
+    Vector *v = new Vector(count);
+
+    NSCAssert(count <= 4, @"unexpected count %lu", (unsigned long)count);
+    for (NSUInteger i = 0; i < MIN(count, (NSUInteger)4); i++) {
+      v->_values[i] = vec[i];
+    }
+
+    return v;
+  }
+
+  Vector4r Vector::vector4r() const
+  {
+    Vector4r v = Vector4r::Zero();
+    for (size_t i = 0; i < _count; i++) {
+      v(i) = _values[i];
+    }
+    return v;
+  }
+
+  Vector2r Vector::vector2r() const
+  {
+    Vector2r v = Vector2r::Zero();
+    if (_count > 0) v(0) = _values[0];
+    if (_count > 1) v(1) = _values[1];
+    return v;
+  }
+
+  Vector *Vector::new_cg_float(CGFloat f)
+  {
+    Vector *v = new Vector(1);
+    v->_values[0] = f;
+    return v;
+  }
+
+  CGPoint Vector::cg_point () const
+  {
+    Vector2r v = vector2r();
+    return CGPointMake(v(0), v(1));
+  }
+
+  Vector *Vector::new_cg_point(const CGPoint &p)
+  {
+    Vector *v = new Vector(2);
+    v->_values[0] = p.x;
+    v->_values[1] = p.y;
+    return v;
+  }
+
+  CGSize Vector::cg_size () const
+  {
+    Vector2r v = vector2r();
+    return CGSizeMake(v(0), v(1));
+  }
+
+  Vector *Vector::new_cg_size(const CGSize &s)
+  {
+    Vector *v = new Vector(2);
+    v->_values[0] = s.width;
+    v->_values[1] = s.height;
+    return v;
+  }
+
+  CGRect Vector::cg_rect() const
+  {
+    return _count < 4 ? CGRectZero : CGRectMake(_values[0], _values[1], _values[2], _values[3]);
+  }
+
+  Vector *Vector::new_cg_rect(const CGRect &r)
+  {
+    Vector *v = new Vector(4);
+    v->_values[0] = r.origin.x;
+    v->_values[1] = r.origin.y;
+    v->_values[2] = r.size.width;
+    v->_values[3] = r.size.height;
+    return v;
+  }
+
+#if TARGET_OS_IPHONE
+
+  UIEdgeInsets Vector::ui_edge_insets() const
+  {
+    return _count < 4 ? UIEdgeInsetsZero : UIEdgeInsetsMake(_values[0], _values[1], _values[2], _values[3]);
+  }
+
+  Vector *Vector::new_ui_edge_insets(const UIEdgeInsets &i)
+  {
+    Vector *v = new Vector(4);
+    v->_values[0] = i.top;
+    v->_values[1] = i.left;
+    v->_values[2] = i.bottom;
+    v->_values[3] = i.right;
+    return v;
+  }
+
+#endif
+
+  CGAffineTransform Vector::cg_affine_transform() const
+  {
+    if (_count < 6) {
+      return CGAffineTransformIdentity;
+    }
+
+    NSCAssert(size() >= 6, @"unexpected vector size:%lu", (unsigned long)size());
+    CGAffineTransform t;
+    t.a = _values[0];
+    t.b = _values[1];
+    t.c = _values[2];
+    t.d = _values[3];
+    t.tx = _values[4];
+    t.ty = _values[5];
+    return t;
+  }
+
+  Vector *Vector::new_cg_affine_transform(const CGAffineTransform &t)
+  {
+    Vector *v = new Vector(6);
+    v->_values[0] = t.a;
+    v->_values[1] = t.b;
+    v->_values[2] = t.c;
+    v->_values[3] = t.d;
+    v->_values[4] = t.tx;
+    v->_values[5] = t.ty;
+    return v;
+  }
+
+  CGColorRef Vector::cg_color() const
+  {
+    if (_count < 4) {
+      return NULL;
+    }
+    return POPCGColorRGBACreate(_values);
+  }
+
+  Vector *Vector::new_cg_color(CGColorRef color)
+  {
+    CGFloat rgba[4];
+    POPCGColorGetRGBAComponents(color, rgba);
+    return new_vector(4, rgba);
+  }
+
+#if SCENEKIT_SDK_AVAILABLE
+  SCNVector3 Vector::scn_vector3() const
+  {
+    return _count < 3 ? SCNVector3Make(0.0, 0.0, 0.0) : SCNVector3Make(_values[0], _values[1], _values[2]);
+  }
+
+  Vector *Vector::new_scn_vector3(const SCNVector3 &vec3)
+  {
+    Vector *v = new Vector(3);
+    v->_values[0] = vec3.x;
+    v->_values[1] = vec3.y;
+    v->_values[2] = vec3.z;
+    return v;
+  }
+
+  SCNVector4 Vector::scn_vector4() const
+  {
+    return _count < 4 ? SCNVector4Make(0.0, 0.0, 0.0, 0.0) : SCNVector4Make(_values[0], _values[1], _values[2], _values[3]);
+  }
+
+  Vector *Vector::new_scn_vector4(const SCNVector4 &vec4)
+  {
+    Vector *v = new Vector(4);
+    v->_values[0] = vec4.x;
+    v->_values[1] = vec4.y;
+    v->_values[2] = vec4.z;
+    v->_values[3] = vec4.w;
+    return v;
+  }
+#endif
+
+  void Vector::subRound(CGFloat sub)
+  {
+    for (NSUInteger idx = 0; idx < _count; idx++) {
+      _values[idx] = POPSubRound(_values[idx], sub);
+    }
+  }
+
+  CGFloat Vector::norm() const
+  {
+    return sqrtr(squaredNorm());
+  }
+
+  CGFloat Vector::squaredNorm() const
+  {
+    CGFloat d = 0;
+    for (NSUInteger idx = 0; idx < _count; idx++) {
+      d += (_values[idx] * _values[idx]);
+    }
+    return d;
+  }
+
+  NSString * Vector::toString() const
+  {
+    if (0 == _count)
+      return @"()";
+
+    if (1 == _count)
+      return [NSString stringWithFormat:@"%f", _values[0]];
+
+    if (2 == _count)
+      return [NSString stringWithFormat:@"(%.3f, %.3f)", _values[0], _values[1]];
+
+    NSMutableString *s = [NSMutableString stringWithCapacity:10];
+
+    for (NSUInteger idx = 0; idx < _count; idx++) {
+      if (0 == idx) {
+        [s appendFormat:@"[%.3f", _values[idx]];
+      } else if (idx == _count - 1) {
+        [s appendFormat:@", %.3f]", _values[idx]];
+      } else {
+        [s appendFormat:@", %.3f", _values[idx]];
+      }
+    }
+
+    return s;
+
+  }
+}

pop/WebCore/FloatConversion.h

@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2007 Apple Inc.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1.  Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
+ *     its contributors may be used to endorse or promote products derived
+ *     from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+ * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef FloatConversion_h
+#define FloatConversion_h
+
+#include <CoreGraphics/CGBase.h>
+
+namespace WebCore {
+
+    template<typename T>
+    float narrowPrecisionToFloat(T);
+
+    template<>
+    inline float narrowPrecisionToFloat(double number)
+    {
+        return static_cast<float>(number);
+    }
+
+    template<typename T>
+    CGFloat narrowPrecisionToCGFloat(T);
+
+    template<>
+    inline CGFloat narrowPrecisionToCGFloat(double number)
+    {
+        return static_cast<CGFloat>(number);
+    }
+
+} // namespace WebCore
+
+#endif // FloatConversion_h

pop/WebCore/TransformationMatrix.cpp

@@ -0,0 +1,1074 @@
+/*
+ * Copyright (C) 2005, 2006 Apple Computer, Inc.  All rights reserved.
+ * Copyright (C) 2009 Torch Mobile, Inc.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "TransformationMatrix.h"
+
+#include <math.h>
+
+#include "FloatConversion.h"
+
+inline double deg2rad(double d)  { return d * M_PI / 180.0; }
+inline double rad2deg(double r)  { return r * 180.0 / M_PI; }
+inline double deg2grad(double d) { return d * 400.0 / 360.0; }
+inline double grad2deg(double g) { return g * 360.0 / 400.0; }
+inline double turn2deg(double t) { return t * 360.0; }
+inline double deg2turn(double d) { return d / 360.0; }
+inline double rad2grad(double r) { return r * 200.0 / M_PI; }
+inline double grad2rad(double g) { return g * M_PI / 200.0; }
+
+//using namespace std;
+
+namespace WebCore {
+  
+  //
+  // Supporting Math Functions
+  //
+  // This is a set of function from various places (attributed inline) to do things like
+  // inversion and decomposition of a 4x4 matrix. They are used throughout the code
+  //
+  
+  //
+  // Adapted from Matrix Inversion by Richard Carling, Graphics Gems <http://tog.acm.org/GraphicsGems/index.html>.
+  
+  // EULA: The Graphics Gems code is copyright-protected. In other words, you cannot claim the text of the code
+  // as your own and resell it. Using the code is permitted in any program, product, or library, non-commercial
+  // or commercial. Giving credit is not required, though is a nice gesture. The code comes as-is, and if there
+  // are any flaws or problems with any Gems code, nobody involved with Gems - authors, editors, publishers, or
+  // webmasters - are to be held responsible. Basically, don't be a jerk, and remember that anything free comes
+  // with no guarantee.
+  
+  // A clarification about the storage of matrix elements
+  //
+  // This class uses a 2 dimensional array internally to store the elements of the matrix.  The first index into
+  // the array refers to the column that the element lies in; the second index refers to the row.
+  //
+  // In other words, this is the layout of the matrix:
+  //
+  // | m_matrix[0][0] m_matrix[1][0] m_matrix[2][0] m_matrix[3][0] |
+  // | m_matrix[0][1] m_matrix[1][1] m_matrix[2][1] m_matrix[3][1] |
+  // | m_matrix[0][2] m_matrix[1][2] m_matrix[2][2] m_matrix[3][2] |
+  // | m_matrix[0][3] m_matrix[1][3] m_matrix[2][3] m_matrix[3][3] |
+  
+  typedef double Vector4[4];
+  typedef double Vector3[3];
+  
+  const double SMALL_NUMBER = 1.e-8;
+  
+  // inverse(original_matrix, inverse_matrix)
+  //
+  // calculate the inverse of a 4x4 matrix
+  //
+  // -1
+  // A  = ___1__ adjoint A
+  //       det A
+  
+  //  double = determinant2x2(double a, double b, double c, double d)
+  //
+  //  calculate the determinant of a 2x2 matrix.
+  
+  static double determinant2x2(double a, double b, double c, double d)
+  {
+    return a * d - b * c;
+  }
+  
+  //  double = determinant3x3(a1, a2, a3, b1, b2, b3, c1, c2, c3)
+  //
+  //  Calculate the determinant of a 3x3 matrix
+  //  in the form
+  //
+  //      | a1,  b1,  c1 |
+  //      | a2,  b2,  c2 |
+  //      | a3,  b3,  c3 |
+  
+  static double determinant3x3(double a1, double a2, double a3, double b1, double b2, double b3, double c1, double c2, double c3)
+  {
+    return a1 * determinant2x2(b2, b3, c2, c3)
+    - b1 * determinant2x2(a2, a3, c2, c3)
+    + c1 * determinant2x2(a2, a3, b2, b3);
+  }
+  
+  //  double = determinant4x4(matrix)
+  //
+  //  calculate the determinant of a 4x4 matrix.
+  
+  static double determinant4x4(const TransformationMatrix::Matrix4& m)
+  {
+    // Assign to individual variable names to aid selecting
+    // correct elements
+    
+    double a1 = m[0][0];
+    double b1 = m[0][1];
+    double c1 = m[0][2];
+    double d1 = m[0][3];
+    
+    double a2 = m[1][0];
+    double b2 = m[1][1];
+    double c2 = m[1][2];
+    double d2 = m[1][3];
+    
+    double a3 = m[2][0];
+    double b3 = m[2][1];
+    double c3 = m[2][2];
+    double d3 = m[2][3];
+    
+    double a4 = m[3][0];
+    double b4 = m[3][1];
+    double c4 = m[3][2];
+    double d4 = m[3][3];
+    
+    return a1 * determinant3x3(b2, b3, b4, c2, c3, c4, d2, d3, d4)
+    - b1 * determinant3x3(a2, a3, a4, c2, c3, c4, d2, d3, d4)
+    + c1 * determinant3x3(a2, a3, a4, b2, b3, b4, d2, d3, d4)
+    - d1 * determinant3x3(a2, a3, a4, b2, b3, b4, c2, c3, c4);
+  }
+  
+  // adjoint( original_matrix, inverse_matrix )
+  //
+  //   calculate the adjoint of a 4x4 matrix
+  //
+  //    Let  a   denote the minor determinant of matrix A obtained by
+  //         ij
+  //
+  //    deleting the ith row and jth column from A.
+  //
+  //                  i+j
+  //   Let  b   = (-1)    a
+  //        ij            ji
+  //
+  //  The matrix B = (b  ) is the adjoint of A
+  //                   ij
+  
+  static void adjoint(const TransformationMatrix::Matrix4& matrix, TransformationMatrix::Matrix4& result)
+  {
+    // Assign to individual variable names to aid
+    // selecting correct values
+    double a1 = matrix[0][0];
+    double b1 = matrix[0][1];
+    double c1 = matrix[0][2];
+    double d1 = matrix[0][3];
+    
+    double a2 = matrix[1][0];
+    double b2 = matrix[1][1];
+    double c2 = matrix[1][2];
+    double d2 = matrix[1][3];
+    
+    double a3 = matrix[2][0];
+    double b3 = matrix[2][1];
+    double c3 = matrix[2][2];
+    double d3 = matrix[2][3];
+    
+    double a4 = matrix[3][0];
+    double b4 = matrix[3][1];
+    double c4 = matrix[3][2];
+    double d4 = matrix[3][3];
+    
+    // Row column labeling reversed since we transpose rows & columns
+    result[0][0]  =   determinant3x3(b2, b3, b4, c2, c3, c4, d2, d3, d4);
+    result[1][0]  = - determinant3x3(a2, a3, a4, c2, c3, c4, d2, d3, d4);
+    result[2][0]  =   determinant3x3(a2, a3, a4, b2, b3, b4, d2, d3, d4);
+    result[3][0]  = - determinant3x3(a2, a3, a4, b2, b3, b4, c2, c3, c4);
+    
+    result[0][1]  = - determinant3x3(b1, b3, b4, c1, c3, c4, d1, d3, d4);
+    result[1][1]  =   determinant3x3(a1, a3, a4, c1, c3, c4, d1, d3, d4);
+    result[2][1]  = - determinant3x3(a1, a3, a4, b1, b3, b4, d1, d3, d4);
+    result[3][1]  =   determinant3x3(a1, a3, a4, b1, b3, b4, c1, c3, c4);
+    
+    result[0][2]  =   determinant3x3(b1, b2, b4, c1, c2, c4, d1, d2, d4);
+    result[1][2]  = - determinant3x3(a1, a2, a4, c1, c2, c4, d1, d2, d4);
+    result[2][2]  =   determinant3x3(a1, a2, a4, b1, b2, b4, d1, d2, d4);
+    result[3][2]  = - determinant3x3(a1, a2, a4, b1, b2, b4, c1, c2, c4);
+    
+    result[0][3]  = - determinant3x3(b1, b2, b3, c1, c2, c3, d1, d2, d3);
+    result[1][3]  =   determinant3x3(a1, a2, a3, c1, c2, c3, d1, d2, d3);
+    result[2][3]  = - determinant3x3(a1, a2, a3, b1, b2, b3, d1, d2, d3);
+    result[3][3]  =   determinant3x3(a1, a2, a3, b1, b2, b3, c1, c2, c3);
+  }
+  
+  // Returns false if the matrix is not invertible
+  static bool inverse(const TransformationMatrix::Matrix4& matrix, TransformationMatrix::Matrix4& result)
+  {
+    // Calculate the adjoint matrix
+    adjoint(matrix, result);
+    
+    // Calculate the 4x4 determinant
+    // If the determinant is zero,
+    // then the inverse matrix is not unique.
+    double det = determinant4x4(matrix);
+    
+    if (fabs(det) < SMALL_NUMBER)
+      return false;
+    
+    // Scale the adjoint matrix to get the inverse
+    
+    for (int i = 0; i < 4; i++)
+      for (int j = 0; j < 4; j++)
+        result[i][j] = result[i][j] / det;
+    
+    return true;
+  }
+  
+  // End of code adapted from Matrix Inversion by Richard Carling
+  
+  // Perform a decomposition on the passed matrix, return false if unsuccessful
+  // From Graphics Gems: unmatrix.c
+  
+  // Transpose rotation portion of matrix a, return b
+  static void transposeMatrix4(const TransformationMatrix::Matrix4& a, TransformationMatrix::Matrix4& b)
+  {
+    for (int i = 0; i < 4; i++)
+      for (int j = 0; j < 4; j++)
+        b[i][j] = a[j][i];
+  }
+  
+  // Multiply a homogeneous point by a matrix and return the transformed point
+  static void v4MulPointByMatrix(const Vector4 p, const TransformationMatrix::Matrix4& m, Vector4 result)
+  {
+    result[0] = (p[0] * m[0][0]) + (p[1] * m[1][0]) +
+    (p[2] * m[2][0]) + (p[3] * m[3][0]);
+    result[1] = (p[0] * m[0][1]) + (p[1] * m[1][1]) +
+    (p[2] * m[2][1]) + (p[3] * m[3][1]);
+    result[2] = (p[0] * m[0][2]) + (p[1] * m[1][2]) +
+    (p[2] * m[2][2]) + (p[3] * m[3][2]);
+    result[3] = (p[0] * m[0][3]) + (p[1] * m[1][3]) +
+    (p[2] * m[2][3]) + (p[3] * m[3][3]);
+  }
+  
+  static double v3Length(Vector3 a)
+  {
+    return sqrt((a[0] * a[0]) + (a[1] * a[1]) + (a[2] * a[2]));
+  }
+  
+  static void v3Scale(Vector3 v, double desiredLength)
+  {
+    double len = v3Length(v);
+    if (len != 0) {
+      double l = desiredLength / len;
+      v[0] *= l;
+      v[1] *= l;
+      v[2] *= l;
+    }
+  }
+  
+  static double v3Dot(const Vector3 a, const Vector3 b)
+  {
+    return (a[0] * b[0]) + (a[1] * b[1]) + (a[2] * b[2]);
+  }
+  
+  // Make a linear combination of two vectors and return the result.
+  // result = (a * ascl) + (b * bscl)
+  static void v3Combine(const Vector3 a, const Vector3 b, Vector3 result, double ascl, double bscl)
+  {
+    result[0] = (ascl * a[0]) + (bscl * b[0]);
+    result[1] = (ascl * a[1]) + (bscl * b[1]);
+    result[2] = (ascl * a[2]) + (bscl * b[2]);
+  }
+  
+  // Return the cross product result = a cross b */
+  static void v3Cross(const Vector3 a, const Vector3 b, Vector3 result)
+  {
+    result[0] = (a[1] * b[2]) - (a[2] * b[1]);
+    result[1] = (a[2] * b[0]) - (a[0] * b[2]);
+    result[2] = (a[0] * b[1]) - (a[1] * b[0]);
+  }
+  
+  static bool decompose(const TransformationMatrix::Matrix4& mat, TransformationMatrix::DecomposedType& result)
+  {
+    TransformationMatrix::Matrix4 localMatrix;
+    memcpy(localMatrix, mat, sizeof(TransformationMatrix::Matrix4));
+    
+    // Normalize the matrix.
+    if (localMatrix[3][3] == 0)
+      return false;
+    
+    int i, j;
+    for (i = 0; i < 4; i++)
+      for (j = 0; j < 4; j++)
+        localMatrix[i][j] /= localMatrix[3][3];
+    
+    // perspectiveMatrix is used to solve for perspective, but it also provides
+    // an easy way to test for singularity of the upper 3x3 component.
+    TransformationMatrix::Matrix4 perspectiveMatrix;
+    memcpy(perspectiveMatrix, localMatrix, sizeof(TransformationMatrix::Matrix4));
+    for (i = 0; i < 3; i++)
+      perspectiveMatrix[i][3] = 0;
+    perspectiveMatrix[3][3] = 1;
+    
+    if (determinant4x4(perspectiveMatrix) == 0)
+      return false;
+    
+    // First, isolate perspective.  This is the messiest.
+    if (localMatrix[0][3] != 0 || localMatrix[1][3] != 0 || localMatrix[2][3] != 0) {
+      // rightHandSide is the right hand side of the equation.
+      Vector4 rightHandSide;
+      rightHandSide[0] = localMatrix[0][3];
+      rightHandSide[1] = localMatrix[1][3];
+      rightHandSide[2] = localMatrix[2][3];
+      rightHandSide[3] = localMatrix[3][3];
+      
+      // Solve the equation by inverting perspectiveMatrix and multiplying
+      // rightHandSide by the inverse.  (This is the easiest way, not
+      // necessarily the best.)
+      TransformationMatrix::Matrix4 inversePerspectiveMatrix, transposedInversePerspectiveMatrix;
+      inverse(perspectiveMatrix, inversePerspectiveMatrix);
+      transposeMatrix4(inversePerspectiveMatrix, transposedInversePerspectiveMatrix);
+      
+      Vector4 perspectivePoint;
+      v4MulPointByMatrix(rightHandSide, transposedInversePerspectiveMatrix, perspectivePoint);
+      
+      result.perspectiveX = perspectivePoint[0];
+      result.perspectiveY = perspectivePoint[1];
+      result.perspectiveZ = perspectivePoint[2];
+      result.perspectiveW = perspectivePoint[3];
+      
+      // Clear the perspective partition
+      localMatrix[0][3] = localMatrix[1][3] = localMatrix[2][3] = 0;
+      localMatrix[3][3] = 1;
+    } else {
+      // No perspective.
+      result.perspectiveX = result.perspectiveY = result.perspectiveZ = 0;
+      result.perspectiveW = 1;
+    }
+    
+    // Next take care of translation (easy).
+    result.translateX = localMatrix[3][0];
+    localMatrix[3][0] = 0;
+    result.translateY = localMatrix[3][1];
+    localMatrix[3][1] = 0;
+    result.translateZ = localMatrix[3][2];
+    localMatrix[3][2] = 0;
+    
+    // Vector4 type and functions need to be added to the common set.
+    Vector3 row[3], pdum3;
+    
+    // Now get scale and shear.
+    for (i = 0; i < 3; i++) {
+      row[i][0] = localMatrix[i][0];
+      row[i][1] = localMatrix[i][1];
+      row[i][2] = localMatrix[i][2];
+    }
+    
+    // Compute X scale factor and normalize first row.
+    result.scaleX = v3Length(row[0]);
+    v3Scale(row[0], 1.0);
+    
+    // Compute XY shear factor and make 2nd row orthogonal to 1st.
+    result.skewXY = v3Dot(row[0], row[1]);
+    v3Combine(row[1], row[0], row[1], 1.0, -result.skewXY);
+    
+    // Now, compute Y scale and normalize 2nd row.
+    result.scaleY = v3Length(row[1]);
+    v3Scale(row[1], 1.0);
+    result.skewXY /= result.scaleY;
+    
+    // Compute XZ and YZ shears, orthogonalize 3rd row.
+    result.skewXZ = v3Dot(row[0], row[2]);
+    v3Combine(row[2], row[0], row[2], 1.0, -result.skewXZ);
+    result.skewYZ = v3Dot(row[1], row[2]);
+    v3Combine(row[2], row[1], row[2], 1.0, -result.skewYZ);
+    
+    // Next, get Z scale and normalize 3rd row.
+    result.scaleZ = v3Length(row[2]);
+    v3Scale(row[2], 1.0);
+    result.skewXZ /= result.scaleZ;
+    result.skewYZ /= result.scaleZ;
+    
+    // At this point, the matrix (in rows[]) is orthonormal.
+    // Check for a coordinate system flip.  If the determinant
+    // is -1, then negate the matrix and the scaling factors.
+    v3Cross(row[1], row[2], pdum3);
+    if (v3Dot(row[0], pdum3) < 0) {
+      
+      result.scaleX *= -1;
+      result.scaleY *= -1;
+      result.scaleZ *= -1;
+      
+      for (i = 0; i < 3; i++) {
+        row[i][0] *= -1;
+        row[i][1] *= -1;
+        row[i][2] *= -1;
+      }
+    }
+    
+    // Now, get the rotations out, as described in the gem.
+    
+    result.rotateY = asin(-row[0][2]);
+    if (cos(result.rotateY) != 0) {
+      result.rotateX = atan2(row[1][2], row[2][2]);
+      result.rotateZ = atan2(row[0][1], row[0][0]);
+    } else {
+      result.rotateX = atan2(-row[2][0], row[1][1]);
+      result.rotateZ = 0;
+    }
+    
+    double s, t, x, y, z, w;
+    
+    t = row[0][0] + row[1][1] + row[2][2] + 1.0;
+    
+    if (t > 1e-4) {
+      s = 0.5 / sqrt(t);
+      w = 0.25 / s;
+      x = (row[2][1] - row[1][2]) * s;
+      y = (row[0][2] - row[2][0]) * s;
+      z = (row[1][0] - row[0][1]) * s;
+    } else if (row[0][0] > row[1][1] && row[0][0] > row[2][2]) {
+      s = sqrt (1.0 + row[0][0] - row[1][1] - row[2][2]) * 2.0; // S=4*qx
+      x = 0.25 * s;
+      y = (row[0][1] + row[1][0]) / s;
+      z = (row[0][2] + row[2][0]) / s;
+      w = (row[2][1] - row[1][2]) / s;
+    } else if (row[1][1] > row[2][2]) {
+      s = sqrt (1.0 + row[1][1] - row[0][0] - row[2][2]) * 2.0; // S=4*qy
+      x = (row[0][1] + row[1][0]) / s;
+      y = 0.25 * s;
+      z = (row[1][2] + row[2][1]) / s;
+      w = (row[0][2] - row[2][0]) / s;
+    } else {
+      s = sqrt(1.0 + row[2][2] - row[0][0] - row[1][1]) * 2.0; // S=4*qz
+      x = (row[0][2] + row[2][0]) / s;
+      y = (row[1][2] + row[2][1]) / s;
+      z = 0.25 * s;
+      w = (row[1][0] - row[0][1]) / s;
+    }
+    
+    result.quaternionX = x;
+    result.quaternionY = y;
+    result.quaternionZ = z;
+    result.quaternionW = w;
+    
+    return true;
+  }
+  
+  // Perform a spherical linear interpolation between the two
+  // passed quaternions with 0 <= t <= 1
+  static void slerp(double qa[4], const double qb[4], double t)
+  {
+    double ax, ay, az, aw;
+    double bx, by, bz, bw;
+    double cx, cy, cz, cw;
+    double angle;
+    double th, invth, scale, invscale;
+    
+    ax = qa[0]; ay = qa[1]; az = qa[2]; aw = qa[3];
+    bx = qb[0]; by = qb[1]; bz = qb[2]; bw = qb[3];
+    
+    angle = ax * bx + ay * by + az * bz + aw * bw;
+    
+    if (angle < 0.0) {
+      ax = -ax; ay = -ay;
+      az = -az; aw = -aw;
+      angle = -angle;
+    }
+    
+    if (angle + 1.0 > .05) {
+      if (1.0 - angle >= .05) {
+        th = acos (angle);
+        invth = 1.0 / sin (th);
+        scale = sin (th * (1.0 - t)) * invth;
+        invscale = sin (th * t) * invth;
+      } else {
+        scale = 1.0 - t;
+        invscale = t;
+      }
+    } else {
+      bx = -ay;
+      by = ax;
+      bz = -aw;
+      bw = az;
+      scale = sin(M_PI * (.5 - t));
+      invscale = sin (M_PI * t);
+    }
+    
+    cx = ax * scale + bx * invscale;
+    cy = ay * scale + by * invscale;
+    cz = az * scale + bz * invscale;
+    cw = aw * scale + bw * invscale;
+    
+    qa[0] = cx; qa[1] = cy; qa[2] = cz; qa[3] = cw;
+  }
+  
+  // End of Supporting Math Functions
+  
+  TransformationMatrix::TransformationMatrix(const CGAffineTransform& t)
+  {
+    setMatrix(t.a, t.b, t.c, t.d, t.tx, t.ty);
+  }
+
+  TransformationMatrix::TransformationMatrix(const CATransform3D& t)
+  {
+    setMatrix(
+              t.m11, t.m12, t.m13, t.m14,
+              t.m21, t.m22, t.m23, t.m24,
+              t.m31, t.m32, t.m33, t.m34,
+              t.m41, t.m42, t.m43, t.m44);
+  }
+
+  CATransform3D TransformationMatrix::transform3d() const
+  {
+    CATransform3D t;
+    t.m11 = narrowPrecisionToFloat(m11());
+    t.m12 = narrowPrecisionToFloat(m12());
+    t.m13 = narrowPrecisionToFloat(m13());
+    t.m14 = narrowPrecisionToFloat(m14());
+    t.m21 = narrowPrecisionToFloat(m21());
+    t.m22 = narrowPrecisionToFloat(m22());
+    t.m23 = narrowPrecisionToFloat(m23());
+    t.m24 = narrowPrecisionToFloat(m24());
+    t.m31 = narrowPrecisionToFloat(m31());
+    t.m32 = narrowPrecisionToFloat(m32());
+    t.m33 = narrowPrecisionToFloat(m33());
+    t.m34 = narrowPrecisionToFloat(m34());
+    t.m41 = narrowPrecisionToFloat(m41());
+    t.m42 = narrowPrecisionToFloat(m42());
+    t.m43 = narrowPrecisionToFloat(m43());
+    t.m44 = narrowPrecisionToFloat(m44());
+    return t;
+  }
+
+  CGAffineTransform TransformationMatrix::affineTransform () const
+  {
+    CGAffineTransform t;
+    t.a = narrowPrecisionToFloat(m11());
+    t.b = narrowPrecisionToFloat(m12());
+    t.c = narrowPrecisionToFloat(m21());
+    t.d = narrowPrecisionToFloat(m22());
+    t.tx = narrowPrecisionToFloat(m41());
+    t.ty = narrowPrecisionToFloat(m42());
+    return t;
+  }
+
+  TransformationMatrix::operator CATransform3D() const
+  {
+    return transform3d();
+  }
+  
+  TransformationMatrix& TransformationMatrix::scale(double s)
+  {
+    return scaleNonUniform(s, s);
+  }
+  
+  TransformationMatrix& TransformationMatrix::rotateFromVector(double x, double y)
+  {
+    return rotate(rad2deg(atan2(y, x)));
+  }
+  
+  TransformationMatrix& TransformationMatrix::flipX()
+  {
+    return scaleNonUniform(-1.0, 1.0);
+  }
+  
+  TransformationMatrix& TransformationMatrix::flipY()
+  {
+    return scaleNonUniform(1.0, -1.0);
+  }
+  
+  TransformationMatrix& TransformationMatrix::scaleNonUniform(double sx, double sy)
+  {
+    m_matrix[0][0] *= sx;
+    m_matrix[0][1] *= sx;
+    m_matrix[0][2] *= sx;
+    m_matrix[0][3] *= sx;
+    
+    m_matrix[1][0] *= sy;
+    m_matrix[1][1] *= sy;
+    m_matrix[1][2] *= sy;
+    m_matrix[1][3] *= sy;
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::scale3d(double sx, double sy, double sz)
+  {
+    scaleNonUniform(sx, sy);
+    
+    m_matrix[2][0] *= sz;
+    m_matrix[2][1] *= sz;
+    m_matrix[2][2] *= sz;
+    m_matrix[2][3] *= sz;
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::rotate3d(double x, double y, double z, double angle)
+  {
+    // Normalize the axis of rotation
+    double length = sqrt(x * x + y * y + z * z);
+    if (length == 0) {
+      // A direction vector that cannot be normalized, such as [0, 0, 0], will cause the rotation to not be applied.
+      return *this;
+    } else if (length != 1) {
+      x /= length;
+      y /= length;
+      z /= length;
+    }
+    
+    // Angles are in degrees. Switch to radians.
+    angle = deg2rad(angle);
+    
+    double sinTheta = sin(angle);
+    double cosTheta = cos(angle);
+    
+    TransformationMatrix mat;
+    
+    // Optimize cases where the axis is along a major axis
+    if (x == 1.0 && y == 0.0 && z == 0.0) {
+      mat.m_matrix[0][0] = 1.0;
+      mat.m_matrix[0][1] = 0.0;
+      mat.m_matrix[0][2] = 0.0;
+      mat.m_matrix[1][0] = 0.0;
+      mat.m_matrix[1][1] = cosTheta;
+      mat.m_matrix[1][2] = sinTheta;
+      mat.m_matrix[2][0] = 0.0;
+      mat.m_matrix[2][1] = -sinTheta;
+      mat.m_matrix[2][2] = cosTheta;
+      mat.m_matrix[0][3] = mat.m_matrix[1][3] = mat.m_matrix[2][3] = 0.0;
+      mat.m_matrix[3][0] = mat.m_matrix[3][1] = mat.m_matrix[3][2] = 0.0;
+      mat.m_matrix[3][3] = 1.0;
+    } else if (x == 0.0 && y == 1.0 && z == 0.0) {
+      mat.m_matrix[0][0] = cosTheta;
+      mat.m_matrix[0][1] = 0.0;
+      mat.m_matrix[0][2] = -sinTheta;
+      mat.m_matrix[1][0] = 0.0;
+      mat.m_matrix[1][1] = 1.0;
+      mat.m_matrix[1][2] = 0.0;
+      mat.m_matrix[2][0] = sinTheta;
+      mat.m_matrix[2][1] = 0.0;
+      mat.m_matrix[2][2] = cosTheta;
+      mat.m_matrix[0][3] = mat.m_matrix[1][3] = mat.m_matrix[2][3] = 0.0;
+      mat.m_matrix[3][0] = mat.m_matrix[3][1] = mat.m_matrix[3][2] = 0.0;
+      mat.m_matrix[3][3] = 1.0;
+    } else if (x == 0.0 && y == 0.0 && z == 1.0) {
+      mat.m_matrix[0][0] = cosTheta;
+      mat.m_matrix[0][1] = sinTheta;
+      mat.m_matrix[0][2] = 0.0;
+      mat.m_matrix[1][0] = -sinTheta;
+      mat.m_matrix[1][1] = cosTheta;
+      mat.m_matrix[1][2] = 0.0;
+      mat.m_matrix[2][0] = 0.0;
+      mat.m_matrix[2][1] = 0.0;
+      mat.m_matrix[2][2] = 1.0;
+      mat.m_matrix[0][3] = mat.m_matrix[1][3] = mat.m_matrix[2][3] = 0.0;
+      mat.m_matrix[3][0] = mat.m_matrix[3][1] = mat.m_matrix[3][2] = 0.0;
+      mat.m_matrix[3][3] = 1.0;
+    } else {
+      // This case is the rotation about an arbitrary unit vector.
+      //
+      // Formula is adapted from Wikipedia article on Rotation matrix,
+      // http://en.wikipedia.org/wiki/Rotation_matrix#Rotation_matrix_from_axis_and_angle
+      //
+      // An alternate resource with the same matrix: http://www.fastgraph.com/makegames/3drotation/
+      //
+      double oneMinusCosTheta = 1 - cosTheta;
+      mat.m_matrix[0][0] = cosTheta + x * x * oneMinusCosTheta;
+      mat.m_matrix[0][1] = y * x * oneMinusCosTheta + z * sinTheta;
+      mat.m_matrix[0][2] = z * x * oneMinusCosTheta - y * sinTheta;
+      mat.m_matrix[1][0] = x * y * oneMinusCosTheta - z * sinTheta;
+      mat.m_matrix[1][1] = cosTheta + y * y * oneMinusCosTheta;
+      mat.m_matrix[1][2] = z * y * oneMinusCosTheta + x * sinTheta;
+      mat.m_matrix[2][0] = x * z * oneMinusCosTheta + y * sinTheta;
+      mat.m_matrix[2][1] = y * z * oneMinusCosTheta - x * sinTheta;
+      mat.m_matrix[2][2] = cosTheta + z * z * oneMinusCosTheta;
+      mat.m_matrix[0][3] = mat.m_matrix[1][3] = mat.m_matrix[2][3] = 0.0;
+      mat.m_matrix[3][0] = mat.m_matrix[3][1] = mat.m_matrix[3][2] = 0.0;
+      mat.m_matrix[3][3] = 1.0;
+    }
+    multiply(mat);
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::rotate3d(double rx, double ry, double rz)
+  {
+    // Angles are in degrees. Switch to radians.
+    rx = deg2rad(rx);
+    ry = deg2rad(ry);
+    rz = deg2rad(rz);
+    
+    TransformationMatrix mat;
+    
+    double sinTheta = sin(rz);
+    double cosTheta = cos(rz);
+    
+    mat.m_matrix[0][0] = cosTheta;
+    mat.m_matrix[0][1] = sinTheta;
+    mat.m_matrix[0][2] = 0.0;
+    mat.m_matrix[1][0] = -sinTheta;
+    mat.m_matrix[1][1] = cosTheta;
+    mat.m_matrix[1][2] = 0.0;
+    mat.m_matrix[2][0] = 0.0;
+    mat.m_matrix[2][1] = 0.0;
+    mat.m_matrix[2][2] = 1.0;
+    mat.m_matrix[0][3] = mat.m_matrix[1][3] = mat.m_matrix[2][3] = 0.0;
+    mat.m_matrix[3][0] = mat.m_matrix[3][1] = mat.m_matrix[3][2] = 0.0;
+    mat.m_matrix[3][3] = 1.0;
+    
+    TransformationMatrix rmat(mat);
+    
+    sinTheta = sin(ry);
+    cosTheta = cos(ry);
+    
+    mat.m_matrix[0][0] = cosTheta;
+    mat.m_matrix[0][1] = 0.0;
+    mat.m_matrix[0][2] = -sinTheta;
+    mat.m_matrix[1][0] = 0.0;
+    mat.m_matrix[1][1] = 1.0;
+    mat.m_matrix[1][2] = 0.0;
+    mat.m_matrix[2][0] = sinTheta;
+    mat.m_matrix[2][1] = 0.0;
+    mat.m_matrix[2][2] = cosTheta;
+    mat.m_matrix[0][3] = mat.m_matrix[1][3] = mat.m_matrix[2][3] = 0.0;
+    mat.m_matrix[3][0] = mat.m_matrix[3][1] = mat.m_matrix[3][2] = 0.0;
+    mat.m_matrix[3][3] = 1.0;
+    
+    rmat.multiply(mat);
+    
+    sinTheta = sin(rx);
+    cosTheta = cos(rx);
+    
+    mat.m_matrix[0][0] = 1.0;
+    mat.m_matrix[0][1] = 0.0;
+    mat.m_matrix[0][2] = 0.0;
+    mat.m_matrix[1][0] = 0.0;
+    mat.m_matrix[1][1] = cosTheta;
+    mat.m_matrix[1][2] = sinTheta;
+    mat.m_matrix[2][0] = 0.0;
+    mat.m_matrix[2][1] = -sinTheta;
+    mat.m_matrix[2][2] = cosTheta;
+    mat.m_matrix[0][3] = mat.m_matrix[1][3] = mat.m_matrix[2][3] = 0.0;
+    mat.m_matrix[3][0] = mat.m_matrix[3][1] = mat.m_matrix[3][2] = 0.0;
+    mat.m_matrix[3][3] = 1.0;
+    
+    rmat.multiply(mat);
+    
+    multiply(rmat);
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::translate(double tx, double ty)
+  {
+    m_matrix[3][0] += tx * m_matrix[0][0] + ty * m_matrix[1][0];
+    m_matrix[3][1] += tx * m_matrix[0][1] + ty * m_matrix[1][1];
+    m_matrix[3][2] += tx * m_matrix[0][2] + ty * m_matrix[1][2];
+    m_matrix[3][3] += tx * m_matrix[0][3] + ty * m_matrix[1][3];
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::translate3d(double tx, double ty, double tz)
+  {
+    m_matrix[3][0] += tx * m_matrix[0][0] + ty * m_matrix[1][0] + tz * m_matrix[2][0];
+    m_matrix[3][1] += tx * m_matrix[0][1] + ty * m_matrix[1][1] + tz * m_matrix[2][1];
+    m_matrix[3][2] += tx * m_matrix[0][2] + ty * m_matrix[1][2] + tz * m_matrix[2][2];
+    m_matrix[3][3] += tx * m_matrix[0][3] + ty * m_matrix[1][3] + tz * m_matrix[2][3];
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::translateRight(double tx, double ty)
+  {
+    if (tx != 0) {
+      m_matrix[0][0] +=  m_matrix[0][3] * tx;
+      m_matrix[1][0] +=  m_matrix[1][3] * tx;
+      m_matrix[2][0] +=  m_matrix[2][3] * tx;
+      m_matrix[3][0] +=  m_matrix[3][3] * tx;
+    }
+    
+    if (ty != 0) {
+      m_matrix[0][1] +=  m_matrix[0][3] * ty;
+      m_matrix[1][1] +=  m_matrix[1][3] * ty;
+      m_matrix[2][1] +=  m_matrix[2][3] * ty;
+      m_matrix[3][1] +=  m_matrix[3][3] * ty;
+    }
+    
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::translateRight3d(double tx, double ty, double tz)
+  {
+    translateRight(tx, ty);
+    if (tz != 0) {
+      m_matrix[0][2] +=  m_matrix[0][3] * tz;
+      m_matrix[1][2] +=  m_matrix[1][3] * tz;
+      m_matrix[2][2] +=  m_matrix[2][3] * tz;
+      m_matrix[3][2] +=  m_matrix[3][3] * tz;
+    }
+    
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::skew(double sx, double sy)
+  {
+    // angles are in degrees. Switch to radians
+    sx = deg2rad(sx);
+    sy = deg2rad(sy);
+    
+    TransformationMatrix mat;
+    mat.m_matrix[0][1] = tan(sy); // note that the y shear goes in the first row
+    mat.m_matrix[1][0] = tan(sx); // and the x shear in the second row
+    
+    multiply(mat);
+    return *this;
+  }
+  
+  TransformationMatrix& TransformationMatrix::applyPerspective(double p)
+  {
+    TransformationMatrix mat;
+    if (p != 0)
+      mat.m_matrix[2][3] = -1/p;
+    
+    multiply(mat);
+    return *this;
+  }
+  
+  // this = mat * this.
+  TransformationMatrix& TransformationMatrix::multiply(const TransformationMatrix& mat)
+  {
+    Matrix4 tmp;
+    
+    tmp[0][0] = (mat.m_matrix[0][0] * m_matrix[0][0] + mat.m_matrix[0][1] * m_matrix[1][0]
+                 + mat.m_matrix[0][2] * m_matrix[2][0] + mat.m_matrix[0][3] * m_matrix[3][0]);
+    tmp[0][1] = (mat.m_matrix[0][0] * m_matrix[0][1] + mat.m_matrix[0][1] * m_matrix[1][1]
+                 + mat.m_matrix[0][2] * m_matrix[2][1] + mat.m_matrix[0][3] * m_matrix[3][1]);
+    tmp[0][2] = (mat.m_matrix[0][0] * m_matrix[0][2] + mat.m_matrix[0][1] * m_matrix[1][2]
+                 + mat.m_matrix[0][2] * m_matrix[2][2] + mat.m_matrix[0][3] * m_matrix[3][2]);
+    tmp[0][3] = (mat.m_matrix[0][0] * m_matrix[0][3] + mat.m_matrix[0][1] * m_matrix[1][3]
+                 + mat.m_matrix[0][2] * m_matrix[2][3] + mat.m_matrix[0][3] * m_matrix[3][3]);
+    
+    tmp[1][0] = (mat.m_matrix[1][0] * m_matrix[0][0] + mat.m_matrix[1][1] * m_matrix[1][0]
+                 + mat.m_matrix[1][2] * m_matrix[2][0] + mat.m_matrix[1][3] * m_matrix[3][0]);
+    tmp[1][1] = (mat.m_matrix[1][0] * m_matrix[0][1] + mat.m_matrix[1][1] * m_matrix[1][1]
+                 + mat.m_matrix[1][2] * m_matrix[2][1] + mat.m_matrix[1][3] * m_matrix[3][1]);
+    tmp[1][2] = (mat.m_matrix[1][0] * m_matrix[0][2] + mat.m_matrix[1][1] * m_matrix[1][2]
+                 + mat.m_matrix[1][2] * m_matrix[2][2] + mat.m_matrix[1][3] * m_matrix[3][2]);
+    tmp[1][3] = (mat.m_matrix[1][0] * m_matrix[0][3] + mat.m_matrix[1][1] * m_matrix[1][3]
+                 + mat.m_matrix[1][2] * m_matrix[2][3] + mat.m_matrix[1][3] * m_matrix[3][3]);
+    
+    tmp[2][0] = (mat.m_matrix[2][0] * m_matrix[0][0] + mat.m_matrix[2][1] * m_matrix[1][0]
+                 + mat.m_matrix[2][2] * m_matrix[2][0] + mat.m_matrix[2][3] * m_matrix[3][0]);
+    tmp[2][1] = (mat.m_matrix[2][0] * m_matrix[0][1] + mat.m_matrix[2][1] * m_matrix[1][1]
+                 + mat.m_matrix[2][2] * m_matrix[2][1] + mat.m_matrix[2][3] * m_matrix[3][1]);
+    tmp[2][2] = (mat.m_matrix[2][0] * m_matrix[0][2] + mat.m_matrix[2][1] * m_matrix[1][2]
+                 + mat.m_matrix[2][2] * m_matrix[2][2] + mat.m_matrix[2][3] * m_matrix[3][2]);
+    tmp[2][3] = (mat.m_matrix[2][0] * m_matrix[0][3] + mat.m_matrix[2][1] * m_matrix[1][3]
+                 + mat.m_matrix[2][2] * m_matrix[2][3] + mat.m_matrix[2][3] * m_matrix[3][3]);
+    
+    tmp[3][0] = (mat.m_matrix[3][0] * m_matrix[0][0] + mat.m_matrix[3][1] * m_matrix[1][0]
+                 + mat.m_matrix[3][2] * m_matrix[2][0] + mat.m_matrix[3][3] * m_matrix[3][0]);
+    tmp[3][1] = (mat.m_matrix[3][0] * m_matrix[0][1] + mat.m_matrix[3][1] * m_matrix[1][1]
+                 + mat.m_matrix[3][2] * m_matrix[2][1] + mat.m_matrix[3][3] * m_matrix[3][1]);
+    tmp[3][2] = (mat.m_matrix[3][0] * m_matrix[0][2] + mat.m_matrix[3][1] * m_matrix[1][2]
+                 + mat.m_matrix[3][2] * m_matrix[2][2] + mat.m_matrix[3][3] * m_matrix[3][2]);
+    tmp[3][3] = (mat.m_matrix[3][0] * m_matrix[0][3] + mat.m_matrix[3][1] * m_matrix[1][3]
+                 + mat.m_matrix[3][2] * m_matrix[2][3] + mat.m_matrix[3][3] * m_matrix[3][3]);
+    
+    setMatrix(tmp);
+    return *this;
+  }
+  
+  void TransformationMatrix::multVecMatrix(double x, double y, double& resultX, double& resultY) const
+  {
+    resultX = m_matrix[3][0] + x * m_matrix[0][0] + y * m_matrix[1][0];
+    resultY = m_matrix[3][1] + x * m_matrix[0][1] + y * m_matrix[1][1];
+    double w = m_matrix[3][3] + x * m_matrix[0][3] + y * m_matrix[1][3];
+    if (w != 1 && w != 0) {
+      resultX /= w;
+      resultY /= w;
+    }
+  }
+  
+  void TransformationMatrix::multVecMatrix(double x, double y, double z, double& resultX, double& resultY, double& resultZ) const
+  {
+    resultX = m_matrix[3][0] + x * m_matrix[0][0] + y * m_matrix[1][0] + z * m_matrix[2][0];
+    resultY = m_matrix[3][1] + x * m_matrix[0][1] + y * m_matrix[1][1] + z * m_matrix[2][1];
+    resultZ = m_matrix[3][2] + x * m_matrix[0][2] + y * m_matrix[1][2] + z * m_matrix[2][2];
+    double w = m_matrix[3][3] + x * m_matrix[0][3] + y * m_matrix[1][3] + z * m_matrix[2][3];
+    if (w != 1 && w != 0) {
+      resultX /= w;
+      resultY /= w;
+      resultZ /= w;
+    }
+  }
+  
+  bool TransformationMatrix::isInvertible() const
+  {
+    if (isIdentityOrTranslation())
+      return true;
+    
+    double det = WebCore::determinant4x4(m_matrix);
+    
+    if (fabs(det) < SMALL_NUMBER)
+      return false;
+    
+    return true;
+  }
+  
+  TransformationMatrix TransformationMatrix::inverse() const
+  {
+    if (isIdentityOrTranslation()) {
+      // identity matrix
+      if (m_matrix[3][0] == 0 && m_matrix[3][1] == 0 && m_matrix[3][2] == 0)
+        return TransformationMatrix();
+      
+      // translation
+      return TransformationMatrix(1, 0, 0, 0,
+                                  0, 1, 0, 0,
+                                  0, 0, 1, 0,
+                                  -m_matrix[3][0], -m_matrix[3][1], -m_matrix[3][2], 1);
+    }
+    
+    TransformationMatrix invMat;
+    bool inverted = WebCore::inverse(m_matrix, invMat.m_matrix);
+    if (!inverted)
+      return TransformationMatrix();
+    
+    return invMat;
+  }
+  
+  void TransformationMatrix::makeAffine()
+  {
+    m_matrix[0][2] = 0;
+    m_matrix[0][3] = 0;
+    
+    m_matrix[1][2] = 0;
+    m_matrix[1][3] = 0;
+    
+    m_matrix[2][0] = 0;
+    m_matrix[2][1] = 0;
+    m_matrix[2][2] = 1;
+    m_matrix[2][3] = 0;
+    
+    m_matrix[3][2] = 0;
+    m_matrix[3][3] = 1;
+  }
+  
+  static inline void blendFloat(double& from, double to, double progress)
+  {
+    if (from != to)
+      from = from + (to - from) * progress;
+  }
+  
+  void TransformationMatrix::blend(const TransformationMatrix& from, double progress)
+  {
+    if (from.isIdentity() && isIdentity())
+      return;
+    
+    // decompose
+    DecomposedType fromDecomp;
+    DecomposedType toDecomp;
+    from.decompose(fromDecomp);
+    decompose(toDecomp);
+    
+    // interpolate
+    blendFloat(fromDecomp.scaleX, toDecomp.scaleX, progress);
+    blendFloat(fromDecomp.scaleY, toDecomp.scaleY, progress);
+    blendFloat(fromDecomp.scaleZ, toDecomp.scaleZ, progress);
+    blendFloat(fromDecomp.skewXY, toDecomp.skewXY, progress);
+    blendFloat(fromDecomp.skewXZ, toDecomp.skewXZ, progress);
+    blendFloat(fromDecomp.skewYZ, toDecomp.skewYZ, progress);
+    blendFloat(fromDecomp.translateX, toDecomp.translateX, progress);
+    blendFloat(fromDecomp.translateY, toDecomp.translateY, progress);
+    blendFloat(fromDecomp.translateZ, toDecomp.translateZ, progress);
+    blendFloat(fromDecomp.perspectiveX, toDecomp.perspectiveX, progress);
+    blendFloat(fromDecomp.perspectiveY, toDecomp.perspectiveY, progress);
+    blendFloat(fromDecomp.perspectiveZ, toDecomp.perspectiveZ, progress);
+    blendFloat(fromDecomp.perspectiveW, toDecomp.perspectiveW, progress);
+    
+    slerp(&fromDecomp.quaternionX, &toDecomp.quaternionX, progress);
+    
+    // recompose
+    recompose(fromDecomp);
+  }
+  
+  bool TransformationMatrix::decompose(DecomposedType& decomp) const
+  {
+    if (isIdentity()) {
+      memset(&decomp, 0, sizeof(decomp));
+      decomp.perspectiveW = 1;
+      decomp.scaleX = 1;
+      decomp.scaleY = 1;
+      decomp.scaleZ = 1;
+    }
+    
+    if (!WebCore::decompose(m_matrix, decomp))
+      return false;
+    return true;
+  }
+  
+  void TransformationMatrix::recompose(const DecomposedType& decomp, bool useEulerAngle)
+  {
+    makeIdentity();
+    
+    // first apply perspective
+    m_matrix[0][3] = decomp.perspectiveX;
+    m_matrix[1][3] = decomp.perspectiveY;
+    m_matrix[2][3] = decomp.perspectiveZ;
+    m_matrix[3][3] = decomp.perspectiveW;
+    
+    // now translate
+    translate3d(decomp.translateX, decomp.translateY, decomp.translateZ);
+    
+    if (!useEulerAngle) {
+      // apply rotation
+      double xx = decomp.quaternionX * decomp.quaternionX;
+      double xy = decomp.quaternionX * decomp.quaternionY;
+      double xz = decomp.quaternionX * decomp.quaternionZ;
+      double xw = decomp.quaternionX * decomp.quaternionW;
+      double yy = decomp.quaternionY * decomp.quaternionY;
+      double yz = decomp.quaternionY * decomp.quaternionZ;
+      double yw = decomp.quaternionY * decomp.quaternionW;
+      double zz = decomp.quaternionZ * decomp.quaternionZ;
+      double zw = decomp.quaternionZ * decomp.quaternionW;
+      
+      // Construct a composite rotation matrix from the quaternion values
+      TransformationMatrix rotationMatrix(1 - 2 * (yy + zz), 2 * (xy - zw), 2 * (xz + yw), 0,
+                                          2 * (xy + zw), 1 - 2 * (xx + zz), 2 * (yz - xw), 0,
+                                          2 * (xz - yw), 2 * (yz + xw), 1 - 2 * (xx + yy), 0,
+                                          0, 0, 0, 1);
+      
+      multiply(rotationMatrix);
+    } else {
+      rotate3d(1.0, 0.0, 0.0, rad2deg(decomp.rotateX));
+      rotate3d(0.0, 1.0, 0.0, rad2deg(decomp.rotateY));
+      rotate3d(0.0, 0.0, 1.0, rad2deg(decomp.rotateZ));
+    }
+    
+    // now apply skew
+    if (decomp.skewYZ) {
+      TransformationMatrix tmp;
+      tmp.setM32(decomp.skewYZ);
+      multiply(tmp);
+    }
+    
+    if (decomp.skewXZ) {
+      TransformationMatrix tmp;
+      tmp.setM31(decomp.skewXZ);
+      multiply(tmp);
+    }
+    
+    if (decomp.skewXY) {
+      TransformationMatrix tmp;
+      tmp.setM21(decomp.skewXY);
+      multiply(tmp);
+    }
+    
+    // finally, apply scale
+    scale3d(decomp.scaleX, decomp.scaleY, decomp.scaleZ);
+  }
+}

pop/WebCore/TransformationMatrix.h

@@ -0,0 +1,279 @@
+/*
+ * Copyright (C) 2005, 2006 Apple Computer, Inc.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef TransformationMatrix_h
+#define TransformationMatrix_h
+
+#include <string.h> //for memcpy
+
+#include <CoreGraphics/CGAffineTransform.h>
+
+#include <QuartzCore/QuartzCore.h>
+
+namespace WebCore {
+
+  class TransformationMatrix {
+  public:
+
+    typedef double Matrix4[4][4];
+
+    TransformationMatrix() { makeIdentity(); }
+    TransformationMatrix(const TransformationMatrix& t) { *this = t; }
+    TransformationMatrix(double a, double b, double c, double d, double e, double f) { setMatrix(a, b, c, d, e, f); }
+    TransformationMatrix(double m11, double m12, double m13, double m14,
+                         double m21, double m22, double m23, double m24,
+                         double m31, double m32, double m33, double m34,
+                         double m41, double m42, double m43, double m44)
+    {
+      setMatrix(m11, m12, m13, m14, m21, m22, m23, m24, m31, m32, m33, m34, m41, m42, m43, m44);
+    }
+
+    void setMatrix(double a, double b, double c, double d, double e, double f)
+    {
+      m_matrix[0][0] = a; m_matrix[0][1] = b; m_matrix[0][2] = 0; m_matrix[0][3] = 0;
+      m_matrix[1][0] = c; m_matrix[1][1] = d; m_matrix[1][2] = 0; m_matrix[1][3] = 0;
+      m_matrix[2][0] = 0; m_matrix[2][1] = 0; m_matrix[2][2] = 1; m_matrix[2][3] = 0;
+      m_matrix[3][0] = e; m_matrix[3][1] = f; m_matrix[3][2] = 0; m_matrix[3][3] = 1;
+    }
+
+    void setMatrix(double m11, double m12, double m13, double m14,
+                   double m21, double m22, double m23, double m24,
+                   double m31, double m32, double m33, double m34,
+                   double m41, double m42, double m43, double m44)
+    {
+      m_matrix[0][0] = m11; m_matrix[0][1] = m12; m_matrix[0][2] = m13; m_matrix[0][3] = m14;
+      m_matrix[1][0] = m21; m_matrix[1][1] = m22; m_matrix[1][2] = m23; m_matrix[1][3] = m24;
+      m_matrix[2][0] = m31; m_matrix[2][1] = m32; m_matrix[2][2] = m33; m_matrix[2][3] = m34;
+      m_matrix[3][0] = m41; m_matrix[3][1] = m42; m_matrix[3][2] = m43; m_matrix[3][3] = m44;
+    }
+
+    TransformationMatrix& operator =(const TransformationMatrix &t)
+    {
+      setMatrix(t.m_matrix);
+      return *this;
+    }
+
+    TransformationMatrix& makeIdentity()
+    {
+      setMatrix(1, 0, 0, 0,  0, 1, 0, 0,  0, 0, 1, 0,  0, 0, 0, 1);
+      return *this;
+    }
+
+    bool isIdentity() const
+    {
+      return m_matrix[0][0] == 1 && m_matrix[0][1] == 0 && m_matrix[0][2] == 0 && m_matrix[0][3] == 0 &&
+      m_matrix[1][0] == 0 && m_matrix[1][1] == 1 && m_matrix[1][2] == 0 && m_matrix[1][3] == 0 &&
+      m_matrix[2][0] == 0 && m_matrix[2][1] == 0 && m_matrix[2][2] == 1 && m_matrix[2][3] == 0 &&
+      m_matrix[3][0] == 0 && m_matrix[3][1] == 0 && m_matrix[3][2] == 0 && m_matrix[3][3] == 1;
+    }
+
+    // This form preserves the double math from input to output
+    void map(double x, double y, double& x2, double& y2) const { multVecMatrix(x, y, x2, y2); }
+
+    double m11() const { return m_matrix[0][0]; }
+    void setM11(double f) { m_matrix[0][0] = f; }
+    double m12() const { return m_matrix[0][1]; }
+    void setM12(double f) { m_matrix[0][1] = f; }
+    double m13() const { return m_matrix[0][2]; }
+    void setM13(double f) { m_matrix[0][2] = f; }
+    double m14() const { return m_matrix[0][3]; }
+    void setM14(double f) { m_matrix[0][3] = f; }
+    double m21() const { return m_matrix[1][0]; }
+    void setM21(double f) { m_matrix[1][0] = f; }
+    double m22() const { return m_matrix[1][1]; }
+    void setM22(double f) { m_matrix[1][1] = f; }
+    double m23() const { return m_matrix[1][2]; }
+    void setM23(double f) { m_matrix[1][2] = f; }
+    double m24() const { return m_matrix[1][3]; }
+    void setM24(double f) { m_matrix[1][3] = f; }
+    double m31() const { return m_matrix[2][0]; }
+    void setM31(double f) { m_matrix[2][0] = f; }
+    double m32() const { return m_matrix[2][1]; }
+    void setM32(double f) { m_matrix[2][1] = f; }
+    double m33() const { return m_matrix[2][2]; }
+    void setM33(double f) { m_matrix[2][2] = f; }
+    double m34() const { return m_matrix[2][3]; }
+    void setM34(double f) { m_matrix[2][3] = f; }
+    double m41() const { return m_matrix[3][0]; }
+    void setM41(double f) { m_matrix[3][0] = f; }
+    double m42() const { return m_matrix[3][1]; }
+    void setM42(double f) { m_matrix[3][1] = f; }
+    double m43() const { return m_matrix[3][2]; }
+    void setM43(double f) { m_matrix[3][2] = f; }
+    double m44() const { return m_matrix[3][3]; }
+    void setM44(double f) { m_matrix[3][3] = f; }
+
+    double a() const { return m_matrix[0][0]; }
+    void setA(double a) { m_matrix[0][0] = a; }
+
+    double b() const { return m_matrix[0][1]; }
+    void setB(double b) { m_matrix[0][1] = b; }
+
+    double c() const { return m_matrix[1][0]; }
+    void setC(double c) { m_matrix[1][0] = c; }
+
+    double d() const { return m_matrix[1][1]; }
+    void setD(double d) { m_matrix[1][1] = d; }
+
+    double e() const { return m_matrix[3][0]; }
+    void setE(double e) { m_matrix[3][0] = e; }
+
+    double f() const { return m_matrix[3][1]; }
+    void setF(double f) { m_matrix[3][1] = f; }
+
+    // this = this * mat
+    TransformationMatrix& multiply(const TransformationMatrix&);
+
+    TransformationMatrix& scale(double);
+    TransformationMatrix& scaleNonUniform(double sx, double sy);
+    TransformationMatrix& scale3d(double sx, double sy, double sz);
+
+    TransformationMatrix& rotate(double d) { return rotate3d(0, 0, d); }
+    TransformationMatrix& rotateFromVector(double x, double y);
+    TransformationMatrix& rotate3d(double rx, double ry, double rz);
+
+    // The vector (x,y,z) is normalized if it's not already. A vector of
+    // (0,0,0) uses a vector of (0,0,1).
+    TransformationMatrix& rotate3d(double x, double y, double z, double angle);
+
+    TransformationMatrix& translate(double tx, double ty);
+    TransformationMatrix& translate3d(double tx, double ty, double tz);
+
+    // translation added with a post-multiply
+    TransformationMatrix& translateRight(double tx, double ty);
+    TransformationMatrix& translateRight3d(double tx, double ty, double tz);
+
+    TransformationMatrix& flipX();
+    TransformationMatrix& flipY();
+    TransformationMatrix& skew(double angleX, double angleY);
+    TransformationMatrix& skewX(double angle) { return skew(angle, 0); }
+    TransformationMatrix& skewY(double angle) { return skew(0, angle); }
+
+    TransformationMatrix& applyPerspective(double p);
+    bool hasPerspective() const { return m_matrix[2][3] != 0.0f; }
+
+    bool isInvertible() const;
+
+    // This method returns the identity matrix if it is not invertible.
+    // Use isInvertible() before calling this if you need to know.
+    TransformationMatrix inverse() const;
+
+    // decompose the matrix into its component parts
+    typedef struct {
+      double scaleX, scaleY, scaleZ;
+      double skewXY, skewXZ, skewYZ;
+      double rotateX, rotateY, rotateZ;
+      double quaternionX, quaternionY, quaternionZ, quaternionW;
+      double translateX, translateY, translateZ;
+      double perspectiveX, perspectiveY, perspectiveZ, perspectiveW;
+    } DecomposedType;
+    
+    bool decompose(DecomposedType& decomp) const;
+    void recompose(const DecomposedType& decomp, bool useEulerAngle = false);
+
+    void blend(const TransformationMatrix& from, double progress);
+
+    bool isAffine() const
+    {
+      return (m13() == 0 && m14() == 0 && m23() == 0 && m24() == 0 &&
+              m31() == 0 && m32() == 0 && m33() == 1 && m34() == 0 && m43() == 0 && m44() == 1);
+    }
+
+    // Throw away the non-affine parts of the matrix (lossy!)
+    void makeAffine();
+
+    bool operator==(const TransformationMatrix& m2) const
+    {
+      return (m_matrix[0][0] == m2.m_matrix[0][0] &&
+              m_matrix[0][1] == m2.m_matrix[0][1] &&
+              m_matrix[0][2] == m2.m_matrix[0][2] &&
+              m_matrix[0][3] == m2.m_matrix[0][3] &&
+              m_matrix[1][0] == m2.m_matrix[1][0] &&
+              m_matrix[1][1] == m2.m_matrix[1][1] &&
+              m_matrix[1][2] == m2.m_matrix[1][2] &&
+              m_matrix[1][3] == m2.m_matrix[1][3] &&
+              m_matrix[2][0] == m2.m_matrix[2][0] &&
+              m_matrix[2][1] == m2.m_matrix[2][1] &&
+              m_matrix[2][2] == m2.m_matrix[2][2] &&
+              m_matrix[2][3] == m2.m_matrix[2][3] &&
+              m_matrix[3][0] == m2.m_matrix[3][0] &&
+              m_matrix[3][1] == m2.m_matrix[3][1] &&
+              m_matrix[3][2] == m2.m_matrix[3][2] &&
+              m_matrix[3][3] == m2.m_matrix[3][3]);
+    }
+
+    bool operator!=(const TransformationMatrix& other) const { return !(*this == other); }
+
+    // *this = *this * t (i.e., a multRight)
+    TransformationMatrix& operator*=(const TransformationMatrix& t)
+    {
+      return multiply(t);
+    }
+
+    // result = *this * t (i.e., a multRight)
+    TransformationMatrix operator*(const TransformationMatrix& t)
+    {
+      TransformationMatrix result = *this;
+      result.multiply(t);
+      return result;
+    }
+
+    CATransform3D transform3d () const;
+    CGAffineTransform affineTransform () const;
+
+    TransformationMatrix(const CATransform3D&);
+    operator CATransform3D() const;
+
+    TransformationMatrix(const CGAffineTransform&);
+    operator CGAffineTransform() const;
+
+  private:
+
+    // multiply passed 2D point by matrix (assume z=0)
+    void multVecMatrix(double x, double y, double& dstX, double& dstY) const;
+
+    // multiply passed 3D point by matrix
+    void multVecMatrix(double x, double y, double z, double& dstX, double& dstY, double& dstZ) const;
+
+    void setMatrix(const Matrix4 m)
+    {
+      if (m && m != m_matrix)
+        memcpy(m_matrix, m, sizeof(Matrix4));
+    }
+
+    bool isIdentityOrTranslation() const
+    {
+      return m_matrix[0][0] == 1 && m_matrix[0][1] == 0 && m_matrix[0][2] == 0 && m_matrix[0][3] == 0 &&
+      m_matrix[1][0] == 0 && m_matrix[1][1] == 1 && m_matrix[1][2] == 0 && m_matrix[1][3] == 0 &&
+      m_matrix[2][0] == 0 && m_matrix[2][1] == 0 && m_matrix[2][2] == 1 && m_matrix[2][3] == 0 &&
+      m_matrix[3][3] == 1;
+    }
+
+    Matrix4 m_matrix;
+  };
+
+} // namespace WebCore
+
+#endif // TransformationMatrix_h

pop/WebCore/UnitBezier.h

@@ -0,0 +1,123 @@
+/*
+ * Copyright (C) 2008 Apple Inc. All Rights Reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
+ * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
+ * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef UnitBezier_h
+#define UnitBezier_h
+
+#include <math.h>
+
+namespace WebCore {
+  
+  struct UnitBezier {
+    UnitBezier(double p1x, double p1y, double p2x, double p2y)
+    {
+      // Calculate the polynomial coefficients, implicit first and last control points are (0,0) and (1,1).
+      cx = 3.0 * p1x;
+      bx = 3.0 * (p2x - p1x) - cx;
+      ax = 1.0 - cx -bx;
+      
+      cy = 3.0 * p1y;
+      by = 3.0 * (p2y - p1y) - cy;
+      ay = 1.0 - cy - by;
+    }
+    
+    double sampleCurveX(double t)
+    {
+      // `ax t^3 + bx t^2 + cx t' expanded using Horner's rule.
+      return ((ax * t + bx) * t + cx) * t;
+    }
+    
+    double sampleCurveY(double t)
+    {
+      return ((ay * t + by) * t + cy) * t;
+    }
+    
+    double sampleCurveDerivativeX(double t)
+    {
+      return (3.0 * ax * t + 2.0 * bx) * t + cx;
+    }
+    
+    // Given an x value, find a parametric value it came from.
+    double solveCurveX(double x, double epsilon)
+    {
+      double t0;
+      double t1;
+      double t2;
+      double x2;
+      double d2;
+      int i;
+      
+      // First try a few iterations of Newton's method -- normally very fast.
+      for (t2 = x, i = 0; i < 8; i++) {
+        x2 = sampleCurveX(t2) - x;
+        if (fabs (x2) < epsilon)
+          return t2;
+        d2 = sampleCurveDerivativeX(t2);
+        if (fabs(d2) < 1e-6)
+          break;
+        t2 = t2 - x2 / d2;
+      }
+      
+      // Fall back to the bisection method for reliability.
+      t0 = 0.0;
+      t1 = 1.0;
+      t2 = x;
+      
+      if (t2 < t0)
+        return t0;
+      if (t2 > t1)
+        return t1;
+      
+      while (t0 < t1) {
+        x2 = sampleCurveX(t2);
+        if (fabs(x2 - x) < epsilon)
+          return t2;
+        if (x > x2)
+          t0 = t2;
+        else
+          t1 = t2;
+        t2 = (t1 - t0) * .5 + t0;
+      }
+      
+      // Failure.
+      return t2;
+    }
+    
+    double solve(double x, double epsilon)
+    {
+      return sampleCurveY(solveCurveX(x, epsilon));
+    }
+    
+  private:
+    double ax;
+    double bx;
+    double cx;
+    
+    double ay;
+    double by;
+    double cy;
+  };
+}
+#endif

pop/module.modulemap

@@ -0,0 +1,6 @@
+framework module pop {
+    umbrella header "POP.h"
+    
+    exclude header "POPAnimationPrivate.h"
+    exclude header "POPAnimatorPrivate.h"
+}