Translating the right/bottom coordinates from offsets to absolute
coordinates in wlroots (rather than in the compositor) was supposed to
be more reliable, since wlroots had access to the X11 screen size.
It ended up being less reliable, because the screen size values
(xwm->screen->width_in_pixels/height_in_pixels) are not updated when the
output layout changes.
So let's remove the translation from wlroots, and let the compositor
figure it out. From what I can understand of the current XWayland code,
the X11 screen size should generally match the overall wlr_output_layout
bounding box, which the compositor has access to.
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.
