Adding a barrier and later enabling the input capture session will
create MetaBarrier instances for each added input capture barrier.
The barriers are created as "sticky" which means that when a pointer
hits the barrier, it'll stick to the point of entry, until it's
released.
The input capture session is also turned into a state machine with
explicit state, to more easily track things.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2628>
This API aims to provide a way for users to capture input devices under
certain conditions, for example when a pointer crosses a specified
barrier.
So far only part of the API is implemented, specifially the session
management as well as zone advertisement, where a zone refers to a
region in the compositor which edges will eventually be made available
for barrier placement.
So far the remote access handle is created while the session is enable,
despite the input capturing isn't actually active yet. This will change
in the future once it can actually become active.
v2: Remove absolute/relative pointer, keep only pointer (ofourdan)
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2628>
