[mutter] actor: Always use get_paint_volume override for active effects

[Carlos Garnacho <carlosg src gnome org>]

commit 5d19aee23a55a642517ec43b116e4452ab0c6cf1
Author: Sam Spilsbury <sam endlessm com>
Date:   Wed Aug 29 08:32:29 2018 +0800

    actor: Always use get_paint_volume override for active effects
    
    If an effect is active and it overrides the paint volume, we should
    always recompute the paint volume when requested and not use the
    cache, since the paint volume override can change from call to
    call depending on what phase of painting we are in. For instance,
    if we are part way through painting effects and request the
    paint volume, the paint volume should only go up to the current
    effect, but in a later call to compute repaint regions, the
    paint volume needs to expand to accomadate the effect.
    
    This still involves a lot of recomputation in the case of effects -
    in a later clutter version it would be worth adding an API to
    allow effects to explicitly recompute and return a new the paint
    volume up to the current effect as opposed to recomputing
    the cached one.

 clutter/clutter/clutter-actor.c          | 34 +++++++++++++++++++++++++++++++-
 clutter/clutter/clutter-effect-private.h |  1 +
 clutter/clutter/clutter-effect.c         |  8 ++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)
---
diff --git a/clutter/clutter/clutter-actor.c b/clutter/clutter/clutter-actor.c
index 8e160067e..843e04abb 100644
--- a/clutter/clutter/clutter-actor.c
+++ b/clutter/clutter/clutter-actor.c
@@ -17521,6 +17521,32 @@ _clutter_actor_get_paint_volume_real (ClutterActor *self,
   return TRUE;
 }
 
+static gboolean
+_clutter_actor_has_active_paint_volume_override_effects (ClutterActor *self)
+{
+  const GList *l;
+
+  if (self->priv->effects == NULL)
+    return FALSE;
+
+  /* We just need to all effects current effect to see
+   * if anyone wants to override the paint volume. If so, then
+   * we need to recompute, since the paint volume returned can
+   * change from call to call. */
+  for (l = _clutter_meta_group_peek_metas (self->priv->effects);
+       l != NULL;
+       l = l->next)
+    {
+      ClutterEffect *effect = l->data;
+
+      if (clutter_actor_meta_get_enabled (CLUTTER_ACTOR_META (effect)) &&
+          _clutter_effect_has_custom_paint_volume (effect))
+        return TRUE;
+    }
+
+  return FALSE;
+}
+
 /* The public clutter_actor_get_paint_volume API returns a const
  * pointer since we return a pointer directly to the cached
  * PaintVolume associated with the actor and don't want the user to
@@ -17537,7 +17563,13 @@ _clutter_actor_get_paint_volume_mutable (ClutterActor *self)
 
   if (priv->paint_volume_valid)
     {
-      if (!priv->needs_paint_volume_update)
+      /* If effects are applied, the actor paint volume
+       * needs to be recomputed on each paint, since those
+       * paint volumes could change over the duration of the
+       * effect. */
+      if (!priv->needs_paint_volume_update &&
+          priv->current_effect == NULL &&
+          !_clutter_actor_has_active_paint_volume_override_effects (self))
         return &priv->paint_volume;
       clutter_paint_volume_free (&priv->paint_volume);
     }
diff --git a/clutter/clutter/clutter-effect-private.h b/clutter/clutter/clutter-effect-private.h
index 578b6a13a..c1e9b3b7f 100644
--- a/clutter/clutter/clutter-effect-private.h
+++ b/clutter/clutter/clutter-effect-private.h
@@ -9,6 +9,7 @@ gboolean        _clutter_effect_pre_paint               (ClutterEffect
 void            _clutter_effect_post_paint              (ClutterEffect           *effect);
 gboolean        _clutter_effect_get_paint_volume        (ClutterEffect           *effect,
                                                          ClutterPaintVolume      *volume);
+gboolean        _clutter_effect_has_custom_paint_volume (ClutterEffect           *effect);
 void            _clutter_effect_paint                   (ClutterEffect           *effect,
                                                          ClutterEffectPaintFlags  flags);
 void            _clutter_effect_pick                    (ClutterEffect           *effect,
diff --git a/clutter/clutter/clutter-effect.c b/clutter/clutter/clutter-effect.c
index 06df7ffbd..5db5541b7 100644
--- a/clutter/clutter/clutter-effect.c
+++ b/clutter/clutter/clutter-effect.c
@@ -308,6 +308,14 @@ _clutter_effect_get_paint_volume (ClutterEffect      *effect,
   return CLUTTER_EFFECT_GET_CLASS (effect)->get_paint_volume (effect, volume);
 }
 
+gboolean
+_clutter_effect_has_custom_paint_volume (ClutterEffect *effect)
+{
+  g_return_val_if_fail (CLUTTER_IS_EFFECT (effect), FALSE);
+
+  return CLUTTER_EFFECT_GET_CLASS (effect)->get_paint_volume != clutter_effect_real_get_paint_volume;
+}
+
 /**
  * clutter_effect_queue_repaint:
  * @effect: A #ClutterEffect which needs redrawing