Any Qt Quick application, for example Qt Quick Controls 2 Gallery, seems to properly draw their content after a new geometry was set, but then it leaves (or draws) a region that is the size of the original window on top of the real content with a blue region around it.

Making the window to repaint makes the region to disappear. Qt Widget applications with OpenGL surface flashes a similar blue region for about a single frame, but then properly repaints itself.

To reproduce, set QT_OPENGL=angle, run a Qt Quick application and press "Win + Left arrow"

This doesn't seem to be reproducible with desktop OpenGL.