[mutter/gbsneto/offscreen-paint-node: 1/4] clutter/offscreen-effect: Implement paint_node()

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 5b23f41b682c0248553c20e386dc7d6a28643d11
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Sun Jul 5 17:57:37 2020 -0300

    clutter/offscreen-effect: Implement paint_node()
    
    The paint node tree that ClutterOffscreenEffect generates is
    simple:
    
      Root
        |------------+
        |            |
      Layer        Pipeline
        |
      Actor
    
    Right now, both pre-paint and ClutterLayerNode push the offscreen
    to the framebuffer stack. That's harmless, and will go away soon
    anyway.
    
    The actor node is created and added in a separate function because
    it'll be reused by the next commit.

 clutter/clutter/clutter-offscreen-effect.c | 35 ++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
---
diff --git a/clutter/clutter/clutter-offscreen-effect.c b/clutter/clutter/clutter-offscreen-effect.c
index 84a2d8557f..4871562b76 100644
--- a/clutter/clutter/clutter-offscreen-effect.c
+++ b/clutter/clutter/clutter-offscreen-effect.c
@@ -484,6 +484,40 @@ clutter_offscreen_effect_post_paint (ClutterEffect       *effect,
   clutter_offscreen_effect_paint_texture (self, paint_context);
 }
 
+static void
+add_actor_node (ClutterOffscreenEffect *offscreen_effect,
+                ClutterPaintNode       *node,
+                int                     paint_opacity)
+{
+  ClutterOffscreenEffectPrivate *priv = offscreen_effect->priv;
+  ClutterPaintNode *actor_node;
+
+  actor_node = clutter_actor_node_new (priv->actor, paint_opacity);
+  clutter_paint_node_add_child (node, actor_node);
+  clutter_paint_node_unref (actor_node);
+}
+
+static void
+clutter_offscreen_effect_paint_node (ClutterEffect           *effect,
+                                     ClutterPaintNode        *node,
+                                     ClutterPaintContext     *paint_context,
+                                     ClutterEffectPaintFlags  flags)
+{
+  ClutterOffscreenEffect *offscreen_effect = CLUTTER_OFFSCREEN_EFFECT (effect);
+  ClutterOffscreenEffectPrivate *priv = offscreen_effect->priv;
+  ClutterPaintNode *layer_node;
+  CoglFramebuffer *fb;
+
+  fb = COGL_FRAMEBUFFER (priv->offscreen);
+  layer_node = clutter_layer_node_new_to_framebuffer (fb, priv->pipeline);
+  clutter_paint_node_set_static_name (layer_node,
+                                      "ClutterOffscreenEffect (actor offscreen)");
+  clutter_paint_node_add_child (node, layer_node);
+  clutter_paint_node_unref (layer_node);
+
+  add_actor_node (offscreen_effect, layer_node, 255);
+}
+
 static void
 clutter_offscreen_effect_paint (ClutterEffect           *effect,
                                 ClutterPaintContext     *paint_context,
@@ -557,6 +591,7 @@ clutter_offscreen_effect_class_init (ClutterOffscreenEffectClass *klass)
   effect_class->pre_paint = clutter_offscreen_effect_pre_paint;
   effect_class->post_paint = clutter_offscreen_effect_post_paint;
   effect_class->paint = clutter_offscreen_effect_paint;
+  effect_class->paint_node = clutter_offscreen_effect_paint_node;
 
   gobject_class->finalize = clutter_offscreen_effect_finalize;
 }