[mutter/wayland] window-actor: Use more conservative paint volume

[Adel Gadllah <agadllah src gnome org>]

commit 2d67b01c3a706b45d1c2a32b4d5c5c5487fe06f6
Author: Adel Gadllah <adel gadllah gmail com>
Date:   Wed Sep 4 19:43:08 2013 +0200

    window-actor: Use more conservative paint volume
    
    We know which part of the window is not obscured, so take advantaged of that
    to limit the size of the paint volume that we report.

 src/compositor/meta-window-actor.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/src/compositor/meta-window-actor.c b/src/compositor/meta-window-actor.c
index 6e7f4bf..6b5660a 100644
--- a/src/compositor/meta-window-actor.c
+++ b/src/compositor/meta-window-actor.c
@@ -767,6 +767,9 @@ meta_window_actor_get_paint_volume (ClutterActor       *actor,
       gdk_rectangle_union (&bounds, &shadow_bounds, &bounds);
     }
 
+  if (priv->unobscured_region)
+    cairo_region_intersect_rectangle (priv->unobscured_region, &bounds);
+
   origin.x = bounds.x;
   origin.y = bounds.y;
   origin.z = 0.0f;