QMainWIndow and QQuickWidget/QOpenglWidget do not work together

Create a main window form in designer, then place a QQuickWidget/QOpenglWidget in the central area.

What I see is that the window gets "distorted" - the whole contents of the QtCreator window is shifted up about 20-30 pixels so the menu bar and the is hidden.

If I remove the QOpenglWidget again, the creator window is okay, but the designer area is still wrong. A repaint fixes this though.

I see similar but slightly different results when I try and place a QOpenglWidget in QMainWIndow in code. After setting the resize root note to widget flag, it almost works, except the menu bar is invisible - the area is there and I can click the menu bar and get the proper menu folded down, but the menu bar itself is not painted. Without the resize flag set, the window doesn't show the menu bar.

My environment is a downloaded binary Qt 5.9.2 on Windows 10. I did not compile Qt myself or have any strange settings. This happens with a vanilla Qt.