Properly reset focus when surfaces get added/removed. E.g. when
writing in Kate additional surfaces are created for which we do
not want to pass focus.
The button state is a seat-global state and not a per pointer state.
All pressed/released and axis events are moved to the SeatInterface
and just invoke the related method on the focused surface pointer.
This method is supposed to return the PointerInterface for the current
focused surface. At the moment it just creates the one global
PointerInterface. The existing SeatInterface::pointer method got
removed as that is actually wrong usage.
There can only be one focused surface per Seat, thus the information
should be hold in the seat.
This only adjusts the API, the actual data is still hold in the
PointerInterface. This still needs adjustment.
This test application "testRenderingServer" is able to start a
Wayland server and uses a QWidget to render the "scene". It manages
ShellSurfaces and renders them on the QWidget in a very static way.
Furthermore input events (key, pointer, wheel) are forwarded to the
top most Surface.
This test server is able to support kwin_wayland as a client, but
weston's test application in latest release fail due to missing
xdg_shell support.
