ea20076bad
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.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1355>