[clutter/wip/apocalypses/apocalypse-1: 33/46] actor: Provide a better get_paint_volume() implementation

[Emmanuele Bassi <ebassi src gnome org>]

commit 18c3c82e31ce11c6a5cae85dc301f7a0b5a2f518
Author: Emmanuele Bassi <ebassi linux intel com>
Date:   Mon Dec 5 12:45:08 2011 +0000

    actor: Provide a better get_paint_volume() implementation
    
    ClutterActor can do better by default than just giving up immediately.
    
    An actor can check for the clip region, and for its children's paint
    volume, for instance.
    
    Just these two should give us a better default implementation for newly
    written code.

 clutter/clutter-actor.c |   60 ++++++++++++++++++++++++++++++++++++++++++++++-
 1 files changed, 59 insertions(+), 1 deletions(-)
---
diff --git a/clutter/clutter-actor.c b/clutter/clutter-actor.c
index d2b99e9..643d74e 100644
--- a/clutter/clutter-actor.c
+++ b/clutter/clutter-actor.c
@@ -4126,7 +4126,65 @@ static gboolean
 clutter_actor_real_get_paint_volume (ClutterActor       *self,
                                      ClutterPaintVolume *volume)
 {
-  return FALSE;
+  ClutterActorPrivate *priv = self->priv;
+  gboolean res;
+  GList *l;
+
+  /* this is the default return value: we cannot know if a class
+   * is going to paint outside its allocation, so we take the
+   * conservative approach.
+   */
+  res = FALSE;
+
+  /* if the actor has a clip set then we have a pretty definite
+   * size for the paint volume: the actor cannot possibly paint
+   * outside the clip region.
+   */
+  if (priv->clip_to_allocation)
+    {
+      clutter_paint_volume_set_from_allocation (volume, self);
+
+      res = TRUE;
+    }
+  else if (priv->has_clip)
+    {
+      ClutterVertex origin;
+
+      origin.x = priv->clip[0];
+      origin.y = priv->clip[1];
+      origin.z = 0;
+
+      clutter_paint_volume_set_origin (volume, &origin);
+      clutter_paint_volume_set_width (volume, priv->clip[2]);
+      clutter_paint_volume_set_height (volume, priv->clip[3]);
+
+      res = TRUE;
+    }
+
+  /* if we don't have children we just bail out here */
+  if (priv->children == NULL)
+    return res;
+
+  /* but if we have children then we ask for their paint volume in
+   * our coordinates. if any of our children replies that it doesn't
+   * have a paint volume, we bail out
+   */
+  for (l = priv->children; l != NULL; l = l->next)
+    {
+      ClutterActor *child = l->data;
+      const ClutterPaintVolume *child_volume;
+
+      child_volume = clutter_actor_get_transformed_paint_volume (child, self);
+      if (child_volume == NULL)
+        {
+          res = FALSE;
+          break;
+        }
+
+      clutter_paint_volume_union (volume, child_volume);
+    }
+
+  return res;
 }
 
 static gboolean