Since commit d370f1e58, Xwayland can optionally be started rootful and
fullscreen.
To do so, it will setup a viewport to scale the root window to match the
size of the output.
However, if the rootful Xwayland window receives an xdg-surface configure
event before the output definition is complete, as with e.g. the labwc
Wayland compositor, we might end up trying to setup a viewport with a
destination size of 0x0 which is a protocol violation, and that kills
Xwayland.
To avoid that issue, only setup the viewport if the output size is
meaningful.
Also, please note that once the output definition is complete, i.e. when
the "done" event is eventually received, we shall recompute the size for
fullscreen again, hence achieving the desired fullscreen state.
Fixes: d370f1e58 - xwayland: add fullscreen mode for rootful
Closes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1717
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1621>
66f5e7e96a