Qt 6.9 Gui module on Windows with D3D 11 and 12 uses dedicated vblank watcher thread to update window (https://doc.qt.io/qt-6/whatsnew69.html). This thread calls IDXGIOutput::WaitForVBlank that must halt the thread until the next vblank occurs.
This implementation is based on incorrect calculation of vblank occurrence. But it helps to update window.
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https://gitlab.winehq.org/wine/wine/-/merge_requests/8707