Every host seat with pointer capability propagates events to one of
sub-pointer depending which output window we entered.
active_pointer tracks reference to sub-pointer on enter/leave events to
avoid lookup for it on every move events.
Fixesswaywm/wlroots#1499
This effectively gets swaywm/wlroots#1499 to the point where
functionality somewhat preserved and no crash happens.
We still can have only one cursor, but we can control it from multiple
seats in time-sharing manner by entering/leaving output.
This commit makes `get_current_time_msec` correctly return milliseconds
as opposed to microseconds. It also considers the value of `tv_sec`, so
we don't lose occasionally go back in time by one second. Finally, the
function is moved into `util/time.cc` so that it can be reused elsewhere
without having to consider these pitfalls.
Previously, each time a wl_seat.capabilities event was received the
Wayland backend created new input devices. It now only does so the first
time.
Input devices are now destroyed when the cap is removed.
Closes: https://github.com/swaywm/sway/issues/5055
