cullable: Reset the culling state instead of skipping the traversal

When we traversed down to reset the culling state, previously we
would just skip any actors that wanted culling. In order to properly
reset the unobscured_region before painting, we need to traverse down
to these places as well. Do this by calling cull_out with NULL regions
for both arguments, and adapt existing cull_out implementations to
match.

https://bugzilla.gnome.org/show_bug.cgi?id=720631

src/compositor/meta-cullable.c

@@ -70,10 +70,16 @@ meta_cullable_cull_out_children (MetaCullable   *cullable,
   while (clutter_actor_iter_prev (&iter, &child))
     {
       float x, y;
+      gboolean needs_culling;
 
-      if (!CLUTTER_ACTOR_IS_VISIBLE (child))
+      if (!META_IS_CULLABLE (child))
         continue;
 
+      needs_culling = (unobscured_region != NULL && clip_region != NULL);
+
+      if (needs_culling && !CLUTTER_ACTOR_IS_VISIBLE (child))
+        needs_culling = FALSE;
+
       /* 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
@@ -90,15 +96,14 @@ meta_cullable_cull_out_children (MetaCullable   *cullable,
        * as well for the same reason, but omitted for simplicity in the
        * hopes that no-one will do that.
        */
-      if (clutter_actor_has_effects (child))
-        continue;
+      if (needs_culling && clutter_actor_has_effects (child))
+        needs_culling = FALSE;
 
-      if (!META_IS_CULLABLE (child))
-        continue;
-
-      if (!meta_actor_is_untransformed (child, NULL, NULL))
-        continue;
+      if (needs_culling && !meta_actor_is_untransformed (child, NULL, NULL))
+        needs_culling = FALSE;
 
+      if (needs_culling)
+        {
           clutter_actor_get_position (child, &x, &y);
 
           /* Temporarily move to the coordinate system of the actor */
@@ -110,6 +115,11 @@ meta_cullable_cull_out_children (MetaCullable   *cullable,
           cairo_region_translate (unobscured_region, x, y);
           cairo_region_translate (clip_region, x, y);
         }
+      else
+        {
+          meta_cullable_cull_out (META_CULLABLE (child), NULL, NULL);
+        }
+    }
 }
 
 /**

src/compositor/meta-shaped-texture.c

@@ -863,7 +863,9 @@ meta_shaped_texture_cull_out (MetaCullable   *cullable,
     {
       if (priv->opaque_region)
         {
+          if (unobscured_region)
             cairo_region_subtract (unobscured_region, priv->opaque_region);
+          if (clip_region)
             cairo_region_subtract (clip_region, priv->opaque_region);
         }
     }

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

@@ -59,9 +59,6 @@ void     meta_window_actor_set_updates_frozen  (MetaWindowActor *self,
 void     meta_window_actor_queue_frame_drawn   (MetaWindowActor *self,
                                                 gboolean         no_delay_frame);
 
-void meta_window_actor_set_unobscured_region      (MetaWindowActor *self,
-                                                   cairo_region_t  *unobscured_region);
-
 void meta_window_actor_effect_completed (MetaWindowActor *actor,
                                          gulong           event);
 

src/compositor/meta-window-actor.c

@@ -1707,7 +1707,7 @@ see_region (cairo_region_t *region,
  * Provides a hint as to what areas of the window need to queue
  * redraws when damaged. Regions not in @unobscured_region are completely obscured.
  */
-void
+static void
 meta_window_actor_set_unobscured_region (MetaWindowActor *self,
                                          cairo_region_t  *unobscured_region)
 {
@@ -1744,6 +1744,9 @@ meta_window_actor_set_clip_region_beneath (MetaWindowActor *self,
   if (appears_focused ? priv->focused_shadow : priv->unfocused_shadow)
     {
       g_clear_pointer (&priv->shadow_clip, cairo_region_destroy);
+
+      if (beneath_region)
+        {
           priv->shadow_clip = cairo_region_copy (beneath_region);
 
           if (clip_shadow_under_window (self))
@@ -1752,6 +1755,9 @@ meta_window_actor_set_clip_region_beneath (MetaWindowActor *self,
               cairo_region_subtract (priv->shadow_clip, frame_bounds);
             }
         }
+      else
+        priv->shadow_clip = NULL;
+    }
 }
 
 static void

src/compositor/meta-window-group.c

@@ -115,8 +115,6 @@ meta_window_group_paint (ClutterActor *actor)
 {
   cairo_region_t *clip_region;
   cairo_region_t *unobscured_region;
-  ClutterActorIter iter;
-  ClutterActor *child;
   cairo_rectangle_int_t visible_rect, clip_rect;
   int paint_x_offset, paint_y_offset;
   int paint_x_origin, paint_y_origin;
@@ -125,18 +123,6 @@ meta_window_group_paint (ClutterActor *actor)
   MetaWindowGroup *window_group = META_WINDOW_GROUP (actor);
   ClutterActor *stage = clutter_actor_get_stage (actor);
 
-  /* Start off by treating all windows as completely unobscured, so damage anywhere
-   * in a window queues redraws, but confine it more below. */
-  clutter_actor_iter_init (&iter, actor);
-  while (clutter_actor_iter_next (&iter, &child))
-    {
-      if (META_IS_WINDOW_ACTOR (child))
-        {
-          MetaWindowActor *window_actor = META_WINDOW_ACTOR (child);
-          meta_window_actor_set_unobscured_region (window_actor, NULL);
-        }
-    }
-
   /* Normally we expect an actor to be drawn at it's position on the screen.
    * However, if we're inside the paint of a ClutterClone, that won't be the
    * case and we need to compensate. We look at the position of the window