Add a third field: "hover", which is updated from input.c after input
keys MP_KEY_MOUSE_LEAVE and MP_KEY_MOUSE_ENTER - which are typically
sent by the VO.
It's part of mouse-pos and not a new property because it's highly tied
to mouse-pos - it makes x/y invalid while the cursor doesn't hover the
window.
Unike mouse-move, no dummy command was generated, so we add dummy
command in order for observer notification to work even while nothing
is bound.
Like mouse-pos, clients could not detect whether the mouse pointer
hovers the window because the OSC force-binds the MOUSE_LEAVE key, and
now they can using the hover field.
The lua mp.get_mouse_pos() wrapper still returns only x, y because
that's what osc.lua needs. Other clients can simply read the property.
Avi Halachmi (:avih)
58004ea2ef