actor: Add a method for computing the default paint volume

Now that ClutterActor has a default paint volume, subclasses may wish
to retrieve it without chaining up to the parent's implementation of
the get_paint_volume() function.

The get_default_paint_volume() returns a ClutterPaintVolume pointer
to the paint volume as computed by the default implementation of the
get_paint_volume() virtual function; it can only be used immediately,
as it's not guaranteed to survive across multiple frames.

clutter/clutter-actor.c

@@ -4683,33 +4683,11 @@ atk_implementor_iface_init (AtkImplementorIface *iface)
 }
 
 static gboolean
-clutter_actor_real_get_paint_volume (ClutterActor       *self,
-                                     ClutterPaintVolume *volume)
+clutter_actor_update_default_paint_volume (ClutterActor       *self,
+                                           ClutterPaintVolume *volume)
 {
   ClutterActorPrivate *priv = self->priv;
-  ClutterActor *child;
-  ClutterActorClass *klass;
-  gboolean res;
-
-  klass = CLUTTER_ACTOR_GET_CLASS (self);
-
-  /* XXX - this thoroughly sucks, but we don't want to penalize users
-   * who use ClutterActor as a "new ClutterGroup" by forcing a full-stage
-   * redraw. This should go away in 2.0.
-   */
-  if (klass->paint == clutter_actor_real_paint &&
-      klass->get_paint_volume == clutter_actor_real_get_paint_volume)
-    {
-      res = TRUE;
-    }
-  else
-    {
-      /* 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;
-    }
+  gboolean res = FALSE;
 
   /* we start from the allocation */
   clutter_paint_volume_set_width (volume,
@@ -4730,6 +4708,8 @@ clutter_actor_real_get_paint_volume (ClutterActor       *self,
     }
   else
     {
+      ClutterActor *child;
+
       if (priv->has_clip &&
           priv->clip.width >= 0 &&
           priv->clip.height >= 0)
@@ -4774,6 +4754,89 @@ clutter_actor_real_get_paint_volume (ClutterActor       *self,
     }
 
   return res;
+
+}
+
+static gboolean
+clutter_actor_real_get_paint_volume (ClutterActor       *self,
+                                     ClutterPaintVolume *volume)
+{
+  ClutterActorClass *klass;
+  gboolean res;
+
+  klass = CLUTTER_ACTOR_GET_CLASS (self);
+
+  /* XXX - this thoroughly sucks, but we don't want to penalize users
+   * who use ClutterActor as a "new ClutterGroup" by forcing a full-stage
+   * redraw. This should go away in 2.0.
+   */
+  if (klass->paint == clutter_actor_real_paint &&
+      klass->get_paint_volume == clutter_actor_real_get_paint_volume)
+    {
+      res = TRUE;
+    }
+  else
+    {
+      /* 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 (clutter_actor_update_default_paint_volume (self, volume))
+    return res;
+
+  return FALSE;
+}
+
+/**
+ * clutter_actor_get_default_paint_volume:
+ * @self: a #ClutterActor
+ *
+ * Retrieves the default paint volume for @self.
+ *
+ * This function provides the same #ClutterPaintVolume that would be
+ * computed by the default implementation inside #ClutterActor of the
+ * #ClutterActorClass.get_paint_volume() virtual function.
+ *
+ * This function should only be used by #ClutterActor subclasses that
+ * cannot chain up to the parent implementation when computing their
+ * paint volume.
+ *
+ * Return value: (transfer none): a pointer to the default
+ *   #ClutterPaintVolume, relative to the #ClutterActor, or %NULL if
+ *   the actor could not compute a valid paint volume. The returned value
+ *   is not guaranteed to be stable across multiple frames, so if you
+ *   want to retain it, you will need to copy it using
+ *   clutter_paint_volume_copy().
+ *
+ * Since: 1.10
+ */
+const ClutterPaintVolume *
+clutter_actor_get_default_paint_volume (ClutterActor *self)
+{
+  ClutterPaintVolume volume;
+  ClutterPaintVolume *res;
+
+  g_return_val_if_fail (CLUTTER_IS_ACTOR (self), NULL);
+
+  res = NULL;
+  _clutter_paint_volume_init_static (&volume, self);
+  if (clutter_actor_update_default_paint_volume (self, &volume))
+    {
+      ClutterActor *stage = _clutter_actor_get_stage_internal (self);
+
+      if (stage != NULL)
+        {
+          res = _clutter_stage_paint_volume_stack_allocate (CLUTTER_STAGE (stage));
+          _clutter_paint_volume_copy_static (&volume, res);
+        }
+    }
+
+  clutter_paint_volume_free (&volume);
+
+  return res;
 }
 
 static gboolean
@@ -14481,8 +14544,10 @@ _clutter_actor_get_paint_volume_mutable (ClutterActor *self)
  * ensure their volume has a depth of 0. (This will be true so long as
  * you don't call clutter_paint_volume_set_depth().)</note>
  *
- * Return value: (transfer none): a pointer to a #ClutterPaintVolume
- *   or %NULL if no volume could be determined.
+ * Return value: (transfer none): a pointer to a #ClutterPaintVolume,
+ *   or %NULL if no volume could be determined. The returned pointer
+ *   is not guaranteed to be valid across multiple frames; if you want
+ *   to keep it, you will need to copy it using clutter_paint_volume_copy().
  *
  * Since: 1.6
  */
@@ -14512,8 +14577,10 @@ clutter_actor_get_paint_volume (ClutterActor *self)
  * transformed paint volume of all of its children and union them
  * together using clutter_paint_volume_union().
  *
- * Return value: (transfer none): a pointer to a #ClutterPaintVolume
- *   or %NULL if no volume could be determined.
+ * Return value: (transfer none): a pointer to a #ClutterPaintVolume,
+ *   or %NULL if no volume could be determined. The returned pointer is
+ *   not guaranteed to be valid across multiple frames; if you wish to
+ *   keep it, you will have to copy it using clutter_paint_volume_copy().
  *
  * Since: 1.6
  */

clutter/clutter-actor.h

@@ -454,6 +454,7 @@ void                            clutter_actor_get_background_color
 const ClutterPaintVolume *      clutter_actor_get_paint_volume                  (ClutterActor               *self);
 const ClutterPaintVolume *      clutter_actor_get_transformed_paint_volume      (ClutterActor               *self,
                                                                                  ClutterActor               *relative_to_ancestor);
+const ClutterPaintVolume *      clutter_actor_get_default_paint_volume          (ClutterActor               *self);
 
 /* Events */
 void                            clutter_actor_set_reactive                      (ClutterActor               *actor,

clutter/clutter.symbols

@@ -90,6 +90,7 @@ clutter_actor_get_clip
 clutter_actor_get_clip_to_allocation
 clutter_actor_get_constraint
 clutter_actor_get_constraints
+clutter_actor_get_default_paint_volume
 clutter_actor_get_depth
 clutter_actor_get_effect
 clutter_actor_get_effects

doc/reference/clutter/clutter-sections.txt

@@ -444,6 +444,7 @@ clutter_actor_get_transformation_matrix
 clutter_actor_get_paint_volume
 clutter_actor_get_paint_box
 clutter_actor_get_transformed_paint_volume
+clutter_actor_get_default_paint_volume
 
 <SUBSECTION>
 clutter_actor_set_anchor_point