When running headless, weston will not expose a wl_seat.
This was removed with commit a1046adc ("compositor-headless: do not
create a seat").
However, some applications, namely GTK3 based, will log a warning when
there is no wl_seat:
| gdk_seat_get_keyboard assertion GDK_IS_SEAT(seat) failed
While this is arguably a bug in GTK3 which should not complain with a
legit setup, that breaks the CI of those projects when using Weston,
while most of the other Wayland compositors will create a fake seat when
running headless, making weston the odd ball there.
This changes adds a new option "--fake-seat" that will instruct weston
to create a seat when running headless. The default remains not to
create a seat though, so backward compatibility is preserved.
This partially reverts commit a1046adc66.
See-also: https://gitlab.freedesktop.org/ofourdan/xwayland-run/-/issues/12
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>