We were checking for a locked session in desktop_focus_view(), but there
are several other call sites of seat_focus_surface() which were missing
such a check. Any one of those could cause the lock screen to lose focus
(making the session impossible to unlock) or another surface to gain it
(breaching the session lock).
To fix the issue, make any call to seat_focus_surface() no-op when the
session is locked. Add a specific seat_focus_lock_surface() function
which is the only way to bypass the check and is called only from
session-lock.c.
Currently, if the output layout changes while the session is locked,
the lock surfaces may end up wrongly positioned, which looks bad and
may reveal some of the user's workspace underneath.
To prevent this, re-align the scene trees and reconfigure the lock
surfaces when the output layout changes.
XWayland views can self-declare that they don't want keyboard focus via
the ICCCM WM_HINTS property. Most of the logic is already in place to
avoid giving focus to such views (e.g. taskbars).
Add a couple of missing pieces to make this work:
- Hook up view_isfocusable() to look at WM_HINTS for XWayland views
- Adjust desktop_focus_topmost_mapped_view() to skip unfocusable views
