[mutter/wip/carlosg/avoid-parent-relayouts: 2/3] clutter: Avoid relayouts when raising/lowering children

[Carlos Garnacho <carlosg src gnome org>]

commit 37ddc34035a0f4e7782c599985031ef616aee247
Author: Carlos Garnacho <carlosg gnome org>
Date:   Fri Aug 10 21:30:58 2018 +0200

    clutter: Avoid relayouts when raising/lowering children
    
    These calls don't actually affect the layout, but the paint order.
    It seems safe to skip the full relayout/repaint of the parent actor,
    and redraw only the area occupied by the affected child.

 clutter/clutter/clutter-actor.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)
---
diff --git a/clutter/clutter/clutter-actor.c b/clutter/clutter/clutter-actor.c
index f455f2b29..6913f315a 100644
--- a/clutter/clutter/clutter-actor.c
+++ b/clutter/clutter/clutter-actor.c
@@ -1722,6 +1722,22 @@ set_show_on_set_parent (ClutterActor *self,
     }
 }
 
+static void
+clutter_actor_queue_redraw_on_parent (ClutterActor *self)
+{
+  const ClutterPaintVolume *pv;
+
+  if (!self->priv->parent)
+    return;
+
+  /* A relayout/redraw is underway */
+  if (self->priv->needs_allocation)
+    return;
+
+  pv = clutter_actor_get_transformed_paint_volume (self, self->priv->parent);
+  _clutter_actor_queue_redraw_with_clip (self->priv->parent, 0, pv);
+}
+
 /**
  * clutter_actor_show:
  * @self: A #ClutterActor
@@ -13655,7 +13671,7 @@ clutter_actor_set_child_above_sibling (ClutterActor *self,
                                     sibling);
   g_object_unref(child);
 
-  clutter_actor_queue_relayout (self);
+  clutter_actor_queue_redraw_on_parent (child);
 }
 
 /**
@@ -13702,7 +13718,7 @@ clutter_actor_set_child_below_sibling (ClutterActor *self,
                                     sibling);
   g_object_unref(child);
 
-  clutter_actor_queue_relayout (self);
+  clutter_actor_queue_redraw_on_parent (child);
 }
 
 /**