QSGWindowsRenderLoop breaks all animations

Attached is a very small demonstration program. It is simply a QPropertyAnimation that is animating the opacity of a QMainWindow. When you press the button it creates a QQuickWindow (just creates it) - doing this breaks any animation such that they no longer progress.

The reason this happens is that the QQuickWindow constructor calls through to :

QSGRenderLoop *QSGRenderLoop::instance()

which decides it's best to use QSGWindowsRenderLoop (due to the QCoreApplication::setAttribute(Qt::AA_UseSoftwareOpenGL); in main.cpp)

Somehow this is broken such that it never advances the global timer and so all the animations don't progress. The QSGAnimationDriver::advance() function does not get called, no animations run from that point forwards, even new animations that you create.

It all works fine if I override the QSG_RENDER_LOOP by setting the environment variable QSG_RENDER_LOOP=threaded

So it would seem that the QSGWindowsRenderLoop is broken somehow.