The ABSOLUTE_ORIGIN_CHANGED allocation flag is only really useful to
propagate the information of the absolute origin of an actor having
changed inside Clutter. It wasn't used anywhere else besides for some
debug messages and it probably shouldn't be used in custom layout
implementations anyway since 1) actors shouldn't have to be aware of
absolute allocation changes and 2) it doesn't factor in changes to the
transformation matrix of a parent.
Also the propagation of absolute origin changes using this flag broke
with commit 0eab73dc2e and now hidden actors are no longer notified
about those changes.
Additionally, this flag gets in the way of a few potential optimizations
since it has to be propagated even if the allocation box of the child
hasn't changed, forcing a reallocation of the child.
So replace this flag with a simple new private property of ClutterActor
absolute_origin_changed, but keep the exact same behavior for now.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1245
dc8e5c7f8b