Changing display scaling on Windows leads to cached device pixel ratio invalidation in QML window

Steps to Reproduce:

• • Primary monitor: 4K display (3840x2160 @ 200% scaling).
  • Secondary monitor: 1080p display (1920x1080 @ 100% scaling).
  • Launch a Qt QML application in fullscreen/maximized mode on the 4K monitor.

1. Trigger the issue:

• • On the secondary 1080p monitor, open Windows Display Settings.
  • Change the primary 4K monitor's resolution to 1920x1080 with 150% scaling.

1. Observe:

• • In fullscreen/maximized mode:

• • • The application logs:

      "The cached device pixel ratio value was stale on window expose. Please file a QTBUG which explains how to reproduce."

    • Rendered content (position/size) becomes incorrect.
  • In windowed mode:

• • • The application repeatedly logs:
      QSGThreadedRenderLoop: expose event received for window QQuickWindowQmlImpl(0x24fea3795e0 exposed, visibility=QWindow::Windowed, flags=QFlags<Qt::WindowType>(Window), title=screentest, geometry=1069,191 636x479) with invalid geometry: QRect(1069,191 636x479) on QScreen(0x24fe6e5fcd0, name=\\.\DISPLAY1)​
    • Window geometry validation fails despite correct coordinates.

1. Restore original settings:

• • Revert the 4K monitor to 3840x2160 @ 200% scaling → rendering errors persist.

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    Actual Result:

• Cached device pixel ratio fails to update dynamically when display scaling changes.
• In fullscreen/maximized mode: Rendering corruption (position/size mismatch).
• In windowed mode: Repeated QSGThreadedRenderLoop warnings about invalid geometry.
• Errors persist even after restoring original display settings.

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  Expected Result:

• Qt should automatically detect DPI/scaling changes and update rendering parameters.
• Window geometry validation should handle coordinate updates correctly.
• Window content should realign seamlessly after display configuration changes.

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  Additional Notes:

• Issue occurs in both fullscreen/maximized and windowed modes with distinct error patterns.
• Workaround: Manually restarting the application temporarily resolves the issue.