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

[Adel Gadllah <agadllah src gnome org>]

commit f96dc97c4f421c38384cd25775f8478ffd309191
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 8c635d5..63c12c0 100644
--- a/src/compositor/meta-window-actor.c
+++ b/src/compositor/meta-window-actor.c
@@ -734,6 +734,9 @@ 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;