We'll soon introduce a unified wlr_surface map event. Up until now, compositors
have been using wlr_xwayland_surface's map event to setup various wlr_surface
related listeners (e.g. commit). This will no longer be possible when that
event is moved over to wlr_surface. Introduce new events where the compositor
can add/remove wlr_surface event listeners.
This is needed for compositors that want to reserve space for
XWayland panels. Such a feature can be useful in a "transitional"
setup, where only the X11 window manager and compositor is replaced
but other components of an X11 desktop environment are still used.
This change simply reads the X11 property; the compositor is free
to ignore it. Thus, compositors that don't want to support such a
"transitional" feature are not impacted.
v2: Update xwayland_surface_associate()
32daa43a45 has removed the asymmetry in
the relationship of a wlr_surface and an unmapped wlr_xwayland_surface,
when wlr_surface.role_data wasn't NULL but wlr_xwayland_surface.surface
was. However, this also means that
wlr_xwayland_surface_from_wlr_surface() now returns NULL if the
wlr_surface is unmapped. Fix the documentation to reflect this.
