QTabletEvents don't scale well with high-dpi setting enabled

When drawing on a tablet with Windows 10 with  Qt::AA_EnableHighDpiScaling enabled, QTabletEvents coordinates are not scaled with the scale factor of Windows 10 (e.g. 175%). So for example in a simple painting application when the user draws on the center of a QQuickItem using the coordinates from a QTabletEvent, visually the strokes appear on the top left of the window. To workaround this issue one can multiply the coordinates of the QTabletEvent by the effective devicePixelRatio of the current window (e.g. using QQuickWindow::effectiveDevicePixelRatio) and the coordinates are correctly scaled.

However, even this workaround is incomplete. The problem is that it only works if the drawing is done using QTabletEvent:posF() which, according to my testing on Windows 10, only returns coordinates to double precision with no more than 1 decimal place. In order to obtain high precision coordinates the following hack is needed:

// event is QTabletEvent retrieved from QQuickWindow and delivered to a QQuickItem
QPointF pos; 
pos.setX(event->globalPosF().x()- event->globalX() + event->x());
pos.setY(event->globalPosF().y() - event->globalY() + event->y());

This retrieves high precision coordinates, but when a scaling factor is applied according to the device pixel ratio (e.g. pos * QQuickWindow::effectiveDevicePixelRatio) there are some artifacts and the strokes drawn are "shaky". I have checked that using:

QGuiApplication::setHighDpiScaleFactorRoundingPolicy(Qt::HighDpiScaleFactorRoundingPolicy::PassThrough);

mitigates this somehow but doesn't exactly resolve the issue. If high dpi scaling is disabled, the issue is non-existent.

The issue described above can easily be reproduced on Window 10 tablets (mine is a Samsung Galaxy Book 10.6) by creating a simple drawing application that uses QQuickPaintedItem (example https://github.com/dragly/hello-remarkable). I can also provide one if needed.