The new tiling code, instead of based around "tiling states", is instead
based around constrained edges. This allows us to have windows that have
three constrained edges, but keep one free-floating, e.g. a window tiled
to the left has the left, top, and bottom edges constrained, but the
right edge can be left resizable.
This system also is easily extended to support corner tiling. We also,
using the new "size state" system, also keep normal, tiled, and
maximized sizes independently, allowing the maximize button to bounce
between maximized and tiled states without reverting to normal in
between. Dragging from the top will always restore the normal state,
though.
wayland/cursor: Keep a private use count and reference to active buffer
In order for the native cursor renderer to be able to create a hw
cursor in response to wl_pointer.set_cursor(), keep a private use-count
and reference to the active buffer, stopping it from being released
until it is consumed, replaced, or the surface is destroyed.
MetaWaylandSurface: Keep an extra buffer use count for role-less surfaces
Whether a surface needs to keep the committed wl_buffer un-released
depends on what role the surface gets assigned to. For example a cursor
role may need an unreleased shm buffer in order to create a hw cursor from
it.
In order to support this, keep a separate reference and use count to
the buffer on behalf of the in the future assigned role, and release
those references after the surface was assigned a role. A role that
needs its own references and use counts, must in its assign function
make sure to add those.
wayland: Move buffer use count to MetaWaylandSurface
Each wl_surface.commit with a newly attached buffer should result in
one wl_buffer.release for the attached buffer. For example attaching
the same buffer to two different surfaces must always result in two
wl_buffer.release events being emitted by the server. The client is
responsible for counting the wl_buffer.release events and be sure to
have received as many release events as it has attached and committed
the buffer, before reusing it.
