gtk: disable GTK Clipboard with a new meson option

The GTK Clipboard implementation may cause guest hangs.

Therefore implement new configure switch: --enable-gtk-clipboard,

as a meson option disabled by default, which warns in the help
text about the experimental nature of the feature.
Regenerate the meson build options to include it.

The initialization of the clipboard is gtk.c, as well as the
compilation of gtk-clipboard.c are now conditional on this new
option to be set.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1150
Signed-off-by: Claudio Fontana <cfontana@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jim Fehlig <jfehlig@suse.com>
Message-Id: <20221121135538.14625-1-cfontana@suse.de>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

meson.build

@@ -1246,6 +1246,8 @@ endif
 gtk = not_found
 gtkx11 = not_found
 vte = not_found
+have_gtk_clipboard = get_option('gtk_clipboard').enabled()
+
 if not get_option('gtk').auto() or have_system
   gtk = dependency('gtk+-3.0', version: '>=3.22.0',
                    method: 'pkg-config',
@@ -1264,6 +1266,8 @@ if not get_option('gtk').auto() or have_system
                        required: get_option('vte'),
                        kwargs: static_kwargs)
     endif
+  elif have_gtk_clipboard
+    error('GTK clipboard requested, but GTK not found')
   endif
 endif
 
@@ -1842,6 +1846,7 @@ if glusterfs.found()
 endif
 config_host_data.set('CONFIG_GTK', gtk.found())
 config_host_data.set('CONFIG_VTE', vte.found())
+config_host_data.set('CONFIG_GTK_CLIPBOARD', have_gtk_clipboard)
 config_host_data.set('CONFIG_LIBATTR', have_old_libattr)
 config_host_data.set('CONFIG_LIBCAP_NG', libcap_ng.found())
 config_host_data.set('CONFIG_EBPF', libbpf.found())

meson_options.txt

@@ -219,6 +219,13 @@ option('vnc_sasl', type : 'feature', value : 'auto',
        description: 'SASL authentication for VNC server')
 option('vte', type : 'feature', value : 'auto',
        description: 'vte support for the gtk UI')
+
+# GTK Clipboard implementation is disabled by default, since it may cause hangs
+# of the guest VCPUs. See gitlab issue 1150:
+# https://gitlab.com/qemu-project/qemu/-/issues/1150
+
+option('gtk_clipboard', type: 'feature', value : 'disabled',
+       description: 'clipboard support for the gtk UI (EXPERIMENTAL, MAY HANG)')
 option('xkbcommon', type : 'feature', value : 'auto',
        description: 'xkbcommon support')
 option('zstd', type : 'feature', value : 'auto',

scripts/meson-buildoptions.sh

@@ -93,6 +93,7 @@ meson_options_help() {
   printf "%s\n" '  glusterfs       Glusterfs block device driver'
   printf "%s\n" '  gnutls          GNUTLS cryptography support'
   printf "%s\n" '  gtk             GTK+ user interface'
+  printf "%s\n" '  gtk-clipboard   clipboard support for GTK (EXPERIMENTAL, MAY HANG)'
   printf "%s\n" '  guest-agent     Build QEMU Guest Agent'
   printf "%s\n" '  guest-agent-msi Build MSI package for the QEMU Guest Agent'
   printf "%s\n" '  hax             HAX acceleration support'
@@ -274,6 +275,8 @@ _meson_option_parse() {
     --disable-gprof) printf "%s" -Dgprof=false ;;
     --enable-gtk) printf "%s" -Dgtk=enabled ;;
     --disable-gtk) printf "%s" -Dgtk=disabled ;;
+    --enable-gtk-clipboard) printf "%s" -Dgtk_clipboard=enabled ;;
+    --disable-gtk-clipboard) printf "%s" -Dgtk_clipboard=disabled ;;
     --enable-guest-agent) printf "%s" -Dguest_agent=enabled ;;
     --disable-guest-agent) printf "%s" -Dguest_agent=disabled ;;
     --enable-guest-agent-msi) printf "%s" -Dguest_agent_msi=enabled ;;

ui/gtk.c

@@ -2403,7 +2403,9 @@ static void gtk_display_init(DisplayState *ds, DisplayOptions *opts)
         opts->u.gtk.show_tabs) {
         gtk_menu_item_activate(GTK_MENU_ITEM(s->show_tabs_item));
     }
+#ifdef CONFIG_GTK_CLIPBOARD
     gd_clipboard_init(s);
+#endif /* CONFIG_GTK_CLIPBOARD */
 }
 
 static void early_gtk_display_init(DisplayOptions *opts)

ui/meson.build

@@ -97,7 +97,10 @@ if gtk.found()
   softmmu_ss.add(when: 'CONFIG_WIN32', if_true: files('win32-kbd-hook.c'))
 
   gtk_ss = ss.source_set()
-  gtk_ss.add(gtk, vte, pixman, files('gtk.c', 'gtk-clipboard.c'))
+  gtk_ss.add(gtk, vte, pixman, files('gtk.c'))
+  if have_gtk_clipboard
+    gtk_ss.add(files('gtk-clipboard.c'))
+  endif
   gtk_ss.add(when: x11, if_true: files('x_keymap.c'))
   gtk_ss.add(when: opengl, if_true: files('gtk-gl-area.c'))
   gtk_ss.add(when: [x11, opengl], if_true: files('gtk-egl.c'))