The gnome-shell magnifier listens to the `visibility-changed` signal
and calls meta_cursor_tracker_set_pointer_visible(false) when the
cursor became visible.
This leads to a reentrance in meta_cursor_tracker_set_pointer_visible()
and clutter_seat_uninhibit_unfocus() gets called twice, once from the
meta_cursor_tracker_set_pointer_visible(false) by the magnifier and then
the original meta_cursor_tracker_set_pointer_visible(true) continues,
after the first call has set is_showing to false again. This breaks the
inhibitor counting and the ability to use the cursor while using the
magnifier.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3661>
a1381ea6bc