1. Have a primary UHD-screen scaled to 200% and a secondary FullHD-screen scaled to 100%.
2. Run the example "Qt Quick Controls 2 - Gallery" on the primary screen.
   It's in Examples\Qt-5.10.1\quickcontrols2\gallery\gallery.pro
   
3. Move the example to the secondary screen.
   It will be resized so it has the same physical size, but less pixels. The window's content will not be redrawn correctly:
   
4. Resize the example's window.
   This will trigger redrawing:
   

The window should be redrawn automatically in step 3.