Currently xdg-shell applies a geometry set with set_window_geometry
unconditionally. But the specification requires:
> When applied, the effective window geometry will be
> the set window geometry clamped to the bounding rectangle of the
> combined geometry of the surface of the xdg_surface and the
> associated subsurfaces.
This is especially important to implement viewporter and
transformation.
After 20176d03, the Wayland backend only synchronizes with the
compositor after a geometry was set, and it was different from
the current geometry.
That commit was mistakenly comparing the geometry before chaining
up, which would yield a false negative on the case where the
client didn't call set_geometry() before commit().
Fix that by caching the old geometry locally, chain up (and thus
apply the new geometry rectangle), then comparing the old and
current geometry rectangles.
Fixes https://gitlab.gnome.org/GNOME/mutter/issues/150
The current implementation of the XdgSurface v6 protocol does not check
if the window changed before calling meta_window_wayland_move_resize().
The problem with this approach is that calling this function is a costly
operation since we enter the compositor side. In GNOME Shell case, it is
in JavaScript, which triggers a GJS trampoline. Calling this function on
every mouse movement is naturally as terrible as it could be - and is
exactly what happens now.
This commit adds the necessary checks to only call move_resize() when
the window actually changed, or when it needs to be updated.
https://bugzilla.gnome.org/show_bug.cgi?id=780292
Issue: #78
