To find XWayland output that should be the primary one, iterate through all
XWayland outputs, and compare their geometry to the geometry of the primary
logical monitor.
To avoid possible race conditions (Mutter's monitor configuration already
updated, but Xrandr not yet), set the output both after Randr notifications and
after 'monitors-changed' signal.
https://gitlab.gnome.org/GNOME/mutter/-/issues/1407
Signed-off-by: Aleksandr Mezin <mezin.alexander@gmail.com>
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1558>