[clutter] Properly manage timeline refcounting in clutter_animation_set_timeline()

[Tristan Van Berkom <tvb src gnome org>]

commit 67058229f00880c4abf4bc33bef832ba17101ec3
Author: Tristan Van Berkom <tristan van berkom gmail com>
Date:   Tue Mar 27 16:57:03 2012 +0900

    Properly manage timeline refcounting in clutter_animation_set_timeline()
    
    This patch fixes clutter to not crash when multiple animations share
    the same timeline and the actors are explicitly destroyed before
    the timeline completes (bug 672890)

 clutter/clutter-animation.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)
---
diff --git a/clutter/clutter-animation.c b/clutter/clutter-animation.c
index 94f6dba..8880b04 100644
--- a/clutter/clutter-animation.c
+++ b/clutter/clutter-animation.c
@@ -1601,7 +1601,7 @@ clutter_animation_set_timeline (ClutterAnimation *animation,
   if (priv->alpha != NULL)
     cur_timeline = clutter_alpha_get_timeline (priv->alpha);
   else
-    cur_timeline = NULL;
+    cur_timeline = priv->timeline;
 
   if (cur_timeline == timeline)
     return;
@@ -1621,10 +1621,19 @@ clutter_animation_set_timeline (ClutterAnimation *animation,
   priv->timeline_completed_id = 0;
   priv->timeline_frame_id = 0;
 
+  /* Release previously set timeline if any */
+  g_clear_object (&priv->timeline);
+
   if (priv->alpha != NULL)
     clutter_alpha_set_timeline (priv->alpha, timeline);
   else
-    priv->timeline = timeline;
+    {
+      /* Hold a reference to the timeline if it's not reffed by the priv->alpha */
+      priv->timeline = timeline;
+
+      if (priv->timeline)
+	g_object_ref (priv->timeline);
+    }
 
   g_object_notify_by_pspec (G_OBJECT (animation), obj_props[PROP_TIMELINE]);
   g_object_notify_by_pspec (G_OBJECT (animation), obj_props[PROP_DURATION]);
@@ -1632,8 +1641,6 @@ clutter_animation_set_timeline (ClutterAnimation *animation,
 
   if (timeline != NULL)
     {
-      g_object_ref (timeline);
-
       priv->timeline_started_id =
         g_signal_connect (timeline, "started",
                           G_CALLBACK (on_timeline_started),