[clutter] actor: Warn on adding/removing itself as a child

[Emmanuele Bassi <ebassi src gnome org>]

commit c6e40de500534df321d2150229a16215054fce38
Author: Emmanuele Bassi <ebassi gnome org>
Date:   Tue Mar 29 15:04:50 2016 +0100

    actor: Warn on adding/removing itself as a child
    
    ClutterActor should warn if a user tries to add or remove an actor to,
    and from, itself on the scene graph.
    
    Clutter will likely crash, or warn way down the line, but if we can make
    debugging simpler then we should.

 clutter/clutter-actor.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)
---
diff --git a/clutter/clutter-actor.c b/clutter/clutter-actor.c
index d966e40..fedcbfe 100644
--- a/clutter/clutter-actor.c
+++ b/clutter/clutter-actor.c
@@ -4198,6 +4198,13 @@ clutter_actor_remove_child_internal (ClutterActor                 *self,
   gboolean stop_transitions;
   GObject *obj;
 
+  if (self == child)
+    {
+      g_warning ("Cannot remove actor '%s' from itself.",
+                 _clutter_actor_get_debug_name (self));
+      return;
+    }
+
   destroy_meta = (flags & REMOVE_CHILD_DESTROY_META) != 0;
   emit_parent_set = (flags & REMOVE_CHILD_EMIT_PARENT_SET) != 0;
   emit_actor_removed = (flags & REMOVE_CHILD_EMIT_ACTOR_REMOVED) != 0;
@@ -12777,6 +12784,13 @@ clutter_actor_add_child_internal (ClutterActor              *self,
   ClutterActor *old_first_child, *old_last_child;
   GObject *obj;
 
+  if (self == child)
+    {
+      g_warning ("Cannot add the actor '%s' to itself.",
+                  _clutter_actor_get_debug_name (self));
+      return;
+    }
+
   if (child->priv->parent != NULL)
     {
       g_warning ("The actor '%s' already has a parent, '%s'. You must "