Moved from wayland_backend.[h|cpp] to buffer.[h|cpp] and
shm_pool.[h|cpp]. Buffer is slightly adjusted to have the ShmPool
passed in as a ctor argument and the ctor is private and friended with
ShmPool, so that it can only be constructed from ShmPool.
A Surface class is split out which holds a wl_surface and supports
attaching a buffer, setting the damage and emitting a signal when the
frame callback got called.
It doesn't come with a unit test yet as it first needs the ShmPool
and Buffer properly split out to easily set it up.
Returns true if the OperationMode requires KWin to composite to a
Wayland surface. This replaces the checks for the WaylandBackend or env
variable used so far in the construction of the Scene.
This compositor uses only the QPainter API to perform rendering. The
window's X Pixmap is mapped to a QImage using XShm. As rendering backend
a QImage is used.
The new compositing type "QPainterCompositing" is introduced. Effects
need to be adjusted to explicitly check the compositing type and no
longer assume the compositing type is XRender if it's not OpenGL.
This compositor can be selected with using "Q" as the value for
KWIN_COMPOSE env variable or setting the config value to "QPainter".
The GUI is not yet adjusted to select this compositor.
The QPainter scene provides currently the following features:
* 2D transformations (translation and scalation)
* opacity modifications
* rendering of decorations (new PaintRedirector sub class)
* rendering of shadows
* rendering of effect frames
* rendering to a Wayland surface
The following features are currently not provided:
* saturation changes
* brightness changes
* 3D transformations
* rendering to X Overlay window
* offscreen rendering (e.g. needed for screen shot effect)
* custom rendering in the effects to the current back buffer
