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iPad rendering corruption (6.0.1, 6.0.2, 6.1.0 preview)



  • 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 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).

    I am using a 10.2 inch 2019 iPad with 2160 x 1620 pixels physical resolution and iOS 14.4. QScreen reports that the display has a resolution of 1440 x 1080 pixels, with pixel scale of 1.5 (which matches the physical resolution). Similarly the main widget is 1440 x 1080 pixels.

    The app runs in full-screen mode (activated via info.plist "UIRequiresFullScreen" tag).

    Does anyone have similar (or dissimilar) experience? Any ideas on how to solve this?

    PS. I am not sure if this topic should be in Qt6 or the mobile forum section - it matches both.



  • I recommend you report that bug in https://bugreports.qt.io/




  • Lifetime Qt Champion

    Hi,

    Since it's mainly Qt 6, it's the right place.

    Can you provide a minimal compilable example on the bug report ? That will help pinpoint the issue.



  • Example code and screenshot added to the bug report.


  • Lifetime Qt Champion

    Great ! Thank you very much.


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