[mutter] MetaWindowActor: Skip paint optimization for actors with an effect

[Adel Gadllah <agadllah src gnome org>]

commit 7c6bc730313f32030618b819a81c1a65d36659d2
Author: Adel Gadllah <adel gadllah gmail com>
Date:   Tue Sep 20 16:55:48 2011 +0200

    MetaWindowActor: Skip paint optimization for actors with an effect
    
    The optimizations might not work for an actor with an effect, and
    our clipped drawing interferes badly with the operation of
    CoglOffscreenEffect.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=659523

 src/compositor/meta-window-group.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)
---
diff --git a/src/compositor/meta-window-group.c b/src/compositor/meta-window-group.c
index 1623219..107e7ba 100644
--- a/src/compositor/meta-window-group.c
+++ b/src/compositor/meta-window-group.c
@@ -145,6 +145,25 @@ meta_window_group_paint (ClutterActor *actor)
       if (!CLUTTER_ACTOR_IS_VISIBLE (l->data))
         continue;
 
+      /* If an actor has effects applied, then that can change the area
+       * it paints and the opacity, so we no longer can figure out what
+       * portion of the actor is obscured and what portion of the screen
+       * it obscures, so we skip the actor.
+       *
+       * This has a secondary beneficial effect: if a ClutterOffscreenEffect
+       * is applied to an actor, then our clipped redraws interfere with the
+       * caching of the FBO - even if we only need to draw a small portion
+       * of the window right now, ClutterOffscreenEffect may use other portions
+       * of the FBO later. So, skipping actors with effects applied also
+       * prevents these bugs.
+       *
+       * Theoretically, we should check clutter_actor_get_offscreen_redirect()
+       * as well for the same reason, but omitted for simplicity in the
+       * hopes that no-one will do that.
+       */
+      if (clutter_actor_get_effects (l->data) != NULL)
+        continue;
+
       if (META_IS_WINDOW_ACTOR (l->data))
         {
           MetaWindowActor *window_actor = l->data;