The mapping is slightly inspired by the mapping in QtWayland.
But the mapping in QtWayland seems wrong. E.g. there is a linux kernel
button called BTN_BACK which is not mapped to Qt::BackButton.
Anyway we are not really interested in the mapping being 100 % correct
for the case in KWin. KWin internally uses only very few mouse buttons
and all others are only relevant to figure out whether buttons are
pressed. The button code itself is passed to the seat with the native
code.
All pointer related code is moved into a new class called
PointerInputRedirection.
The main idea is to simplify the code and make it easier to maintain.
Therefore also a few changes in the setup were performed:
* before init() is called, no processing is performed
* init() is only called on Wayland and after Workspace is created
* init property is set to false once Workspace or WaylandServer is
destroyed
Thus code can operate on the following assumptions:
* Workspace is valid
* WaylandServer is valid
* ScreenLocker integration is used
The various checks whether there is a waylandServer() and whether
there is a seat are no longer needed.
Some of the checks have been reordered to be faster in the most common
use case of using libinput. E.g. whether warping is supported is first
evaluated by the variable bound to whether we have libinput and only if
that is false the backend is checked.
The new class doesn't have signals but invokes the signals provided
by InputRedirection. I didn't want to add new signals as I consider
them as not needed. The areas in KWin needing those signals should
be ported to InputEventFilters.
