Wrong position of dropdown menu when QWebEngineView is wrapped in QGraphicsProxyWidget

When a QWebEngineView is wrapped in a QGraphicsProxyWidget, drop down menus appear at the wrong position. There are several cases:

• Initially, the menu will appear at a positon relative to the scene instead relative to the item.
• When I resize the item, then themenu appears at the correct position.
• When I then move the item or the viewport of the QGraphicsView, then the menus appear at the previous position and do not follow the move.
• When I scale the item, then the menu itself is scaled, but its position relative to the item is not scaled.

To check this out, I created a minimal proof-of-failure at https://github.com/letsfindaway/WebWidgetDropdown. Try it out as follows:

• When you first click on the dropdown menu, then the browser window moves to the bottom richt. Use the sctrollbars to go to the top left. Here you see the menu.
• When you then seelct the workaround checkbox at the top, then the item is slightly resized. After that, the menu appears at the correct location.
• When you press the Move or Zoom push buttons, then the item is moved or zoomed, and the menu appears again at the wrong location.

For me this looks as if some position and scaling information is not completely forwarded to the piece of code which determins the position of the menu. Resizing the item seems at least to update the position information, while the scale information is still not used to compute the position.

Note: This describes the behavior for Qt 5. For Qt 6 it is a little bit different. But still the drop down menu appears at wrong locations. And the workaround for Qt5 (resizing the item) has no effect with Qt 6.