[mutter] Fix cogl crash from updating non-existent texture

[Jasper St. Pierre <jstpierre src gnome org>]

commit 162213be0d1ce5d0cf1d6c40f7a65a8ab5861b57
Author: Jasper St. Pierre <jstpierre mecheye net>
Date:   Wed Nov 9 15:12:06 2011 -0500

    Fix cogl crash from updating non-existent texture
    
    The code here was always incorrect - we were processing damage events for
    windows without having a texture. Before, this didn't matter, as
    cogl_texture_get_width silently returned 0 for invalid handles. Cogl commit
    4c3dadd35e4657a151025118814534d05091d4db changed this.
    
    The fix here involves two strategies. First, we try to guard MetaTextureTower
    from invalid textures. Second, we try not to go down the path that eventually
    calls meta_shaped_texture_update_area by not handling damage events if we
    don't have a texture for the window.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=660941

 src/compositor/meta-texture-tower.c |    3 +++
 src/compositor/meta-window-actor.c  |    5 +++++
 2 files changed, 8 insertions(+), 0 deletions(-)
---
diff --git a/src/compositor/meta-texture-tower.c b/src/compositor/meta-texture-tower.c
index 8dbe62e..0025472 100644
--- a/src/compositor/meta-texture-tower.c
+++ b/src/compositor/meta-texture-tower.c
@@ -198,6 +198,9 @@ meta_texture_tower_update_area (MetaTextureTower *tower,
 
   g_return_if_fail (tower != NULL);
 
+  if (tower->textures[0] == COGL_INVALID_HANDLE)
+    return;
+
   texture_width = cogl_texture_get_width (tower->textures[0]);
   texture_height = cogl_texture_get_height (tower->textures[0]);
 
diff --git a/src/compositor/meta-window-actor.c b/src/compositor/meta-window-actor.c
index ef47bc8..b69049f 100644
--- a/src/compositor/meta-window-actor.c
+++ b/src/compositor/meta-window-actor.c
@@ -958,6 +958,9 @@ meta_window_actor_damage_all (MetaWindowActor *self)
                 "pixmap-height", &pixmap_height,
                 NULL);
 
+  if (!priv->mapped || priv->needs_pixmap)
+    return;
+
   clutter_x11_texture_pixmap_update_area (texture_x11,
                                           0,
                                           0,
@@ -2029,6 +2032,8 @@ meta_window_actor_process_damage (MetaWindowActor    *self,
       return;
     }
 
+  if (!priv->mapped || priv->needs_pixmap)
+    return;
 
   clutter_x11_texture_pixmap_update_area (texture_x11,
                                           event->area.x,