Performance issue with image painting on Mac

Customer report:

"Attached is a modified scribble app (ModifiedScribble.zip) which reproduces the problem on Mac. It has been constructed in a similar style to our commercial Qt application (ActivInspire). I tested using Qt6.2.1 and macOS Catalina. The problem is seen when attached to a 4K monitor. The problem can be seen with a mouse (also pen and touch). Try to draw a circle, you will get a multi-sided shape. This problem existed in Qt5, but was not as bad. The problem did not exist in Qt4. The ActivInspire source code has not changed in this area since it was working perfectly in Qt4.

I modified QRasterPaintEngine::drawImage (changed source code attached - QRasterPaintEngineDrawImageDebugChanges.txt ) to log the paths taken through the method as most of the time was spent in _platform_memmove$VARIANT$Haswell, called from QRasterPaintEngine::drawImage.

You can see from the attached log for drawing a small circle (smallCircleLog.txt), that most of the time is from 1 path in QRasterPaintEngine::drawImage."