iPad rendering corruption - blank areas

 I have an application that runs on desktop and mobile devices.

I ported the app from Qt 5.15 to 6.0 and found that the graphics are not rendered correctly in Qt6 (they were fine in 5.15 and work on desktop versions with Qt6).

When the app starts the splash screen is shown correctly. I think this is not coming from Qt, but from the iOS splash screen engine.

Once Qt kicks in, the graphics are clipped severely: Only 70-80% of the screen is covered by the application. There are solid gray bands at the bottom and right edge of the screen.

I can also see graphics artifacts that look like incorrect redraws. A horizontal band of "old" pixels is often visible after a widget is redrawn.

The application believes it has the right resolution and layout. Interaction also works in the "invisible areas", so I can press buttons etc, even if they are inside the gray bands. The behaviour is identical on the most recent Qt releases (6.0.1, 6.0.2, 6.1.0 beta1).

The app is meant to run in horizontal full-screen mode (activated via info.plist tags "UIRequiresFullScreen" & "UISupportedInterfaceOrientations"). How-ever, testing with status bars on (not full-screen) and portrait layout, the results are exactly the same = significant portions of the UI are blank.