Wayland: Partial damage limited to SHM buffers
Apparently we currently only implement partial damage for SHM buffers, see
https://gitlab.gnome.org/GNOME/mutter/blob/427670cc638d02f84897ae7fa174de4ac995e7dc/src/wayland/meta-wayland-buffer.c#L530 (edit: we do seem to implement it but it does work - anymore? See #947 (comment 656221)).
While SHM buffers benefit the most from partial redraws (as they are not zero-copy) we also want to limit redraws for EGL/DMABUF clients, allowing us to reduce texture blits. This is especially pressing as GTK4 and partial damage for Firefox are coming closer (https://bugzilla.mozilla.org/show_bug.cgi?id=1484812).
Further more it would be too sad to lose optimizations like !867 (merged) here.