window-actor: add new signal "effects-completed"

When using plugins, the effects will affect the MetaWindowActor size
and position.

Add a new signal "effects-completed" wired to the corresponding
MetaWindowActor which is emitted when all effects are completed so that
derived objects can be notified when all effects are completed and use
the actual size and position.

Closes: https://gitlab.gnome.org/GNOME/mutter/issues/104
(cherry picked from commit 85bbd82ae8)

src/compositor/meta-window-actor-private.h

@@ -58,5 +58,6 @@ void meta_window_actor_effect_completed (MetaWindowActor  *actor,
 
 MetaSurfaceActor *meta_window_actor_get_surface (MetaWindowActor *self);
 void meta_window_actor_update_surface (MetaWindowActor *self);
+MetaWindowActor *meta_window_actor_from_window (MetaWindow *window);
 
 #endif /* META_WINDOW_ACTOR_PRIVATE_H */

src/compositor/meta-window-actor.c

@@ -142,6 +142,8 @@ struct _FrameData
 enum
 {
   FIRST_FRAME,
+  EFFECTS_COMPLETED,
+
   LAST_SIGNAL
 };
 
@@ -238,6 +240,21 @@ meta_window_actor_class_init (MetaWindowActorClass *klass)
                   NULL, NULL, NULL,
                   G_TYPE_NONE, 0);
 
+  /**
+   * MetaWindowActor::effects-completed:
+   * @actor: the #MetaWindowActor instance
+   *
+   * The ::effects-completed signal will be emitted once all pending compositor
+   * effects are completed.
+   */
+  signals[EFFECTS_COMPLETED] =
+    g_signal_new ("effects-completed",
+                  G_TYPE_FROM_CLASS (object_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+
   pspec = g_param_spec_object ("meta-window",
                                "MetaWindow",
                                "The displayed MetaWindow",
@@ -1131,6 +1148,7 @@ meta_window_actor_after_effects (MetaWindowActor *self)
       return;
     }
 
+  g_signal_emit (self, signals[EFFECTS_COMPLETED], 0);
   meta_window_actor_sync_visibility (self);
   meta_window_actor_sync_actor_geometry (self, FALSE);
 }
@@ -2157,3 +2175,9 @@ meta_window_actor_sync_updates_frozen (MetaWindowActor *self)
 
   meta_window_actor_set_updates_frozen (self, meta_window_updates_are_frozen (window));
 }
+
+MetaWindowActor *
+meta_window_actor_from_window (MetaWindow *window)
+{
+  return META_WINDOW_ACTOR (meta_window_get_compositor_private (window));
+}