Qt has problems initializing everything correctly if there is no screen
at startup. E.g. the breeze widget style tries to initialize some pixmaps
and this fails. In worst case hitting asserts in Qt (debug build).
This change creates a dummy screen which gets destroyed as soon as there
is a real screen.
Reviewed-By: notmart and sebas
ASAN righly complained: we need to delete our Wayland objects before
we destroy the internal client connection. Solved by better setting
parent relationships in the QPA plugin and correctly delete objects
in destroy of internal client connection.
We no longer need to have the event dispatcher created before starting
the QApplication, thus we can leave it to the QPA plugin to creat it.
Also we don't need to implement our own dispatcher any more but can
use one from Qt5PlatformSupport as we link it anyways. The special
need for dispatching the WaylandServer is no longer needed as we can
explicitly dispatch it from the QPA plugin if needed.
This introduces an own QPA plugin for KWin. QtWayland's plugin is not
a good solution for KWin as QtWayland is meant for Wayland clients and
not for a Wayland server. Given that it makes more sense to have a very
minimal QPA plugin which supports the use cases we actually have.
With our own QPA plugin we should be able to improve the following
areas:
* no need to create Wayland server before QApplication
* Qt::BypassWindowManagerHint can be supported
* no workaround for creating OpenGL context in main thread
* sharing OpenGL context with Qt
* OpenGL context for Qt on libhybris backend
The plugin supports so far the following features:
* creating a QPlatformWindow using KWayland::Client (ShellSurface)
* creating a QPlatformBackingStore using a ShmPool
* creating a QPlatformOpenGLContext with Wayland::EGL
* or creating a QPlatformOpenGLContext which shares with KWin's scene
* creating a QPlatformScreen for each KWayland::Client::Output
* QPlatformNativeInterface compatible to QtWayland
