[mutter/gbsneto/offscreen-paint-node: 19/20] clutter/offscreen-effect: Document paint nodes

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

commit 5643e86fed864ecfddf29156ccec9287a2041d6a
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Sun Jul 5 18:55:04 2020 -0300

    clutter/offscreen-effect: Document paint nodes
    
    https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1355

 clutter/clutter/clutter-offscreen-effect.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
---
diff --git a/clutter/clutter/clutter-offscreen-effect.c b/clutter/clutter/clutter-offscreen-effect.c
index 7be3056b36..7799dfd653 100644
--- a/clutter/clutter/clutter-offscreen-effect.c
+++ b/clutter/clutter/clutter-offscreen-effect.c
@@ -60,6 +60,30 @@
  * #ClutterOffscreenEffectClass.create_texture() virtual function; no chain up
  * to the #ClutterOffscreenEffect implementation is required in this
  * case.
+ *
+ * ## Paint nodes
+ *
+ * #ClutterOffscreenEffect is generates the following paint node tree:
+ *
+ * |[<!-- language="plain" -->
+ * Effect
+ *  ├─────────┐
+ * Layer   Pipeline
+ *  │
+ * Actor
+ * ]|
+ *
+ * When the actor contents are cached, the generated paint node tree
+ * looks like this:
+ *
+ * |[<!-- language="plain" -->
+ * Effect
+ *  │
+ * Pipeline
+ * ]|
+ *
+ * In both cases, the "Pipeline" node is created with the return value
+ * of #ClutterOffscreenEffectClass.create_pipeline().
  */
 
 #include "clutter-build-config.h"