Linux: Touch/Tablet events can fill up the event queue, causing latency in touch feedback

I'm opening an issue with the same title as QTBUG-14102 because the same exact issue is still present on recent qt versions (probably due to a regression ?)

Here's an okular bug report I opened with this issue:

https://bugs.kde.org/show_bug.cgi?id=399208

If I debug by printing this function: (mouseMoveEvent) https://github.com/KDE/okulTouchar/blob/master/ui/pageview.cpp#L2092 I see that the function gets executed in up to 40-50 milliseconds, but the latency stays low as extra events get discarded/accumulated (I set the mouse to 1000hz input, but I clearly don't see that function executing at 1000hz), but when I use the wacom tablet, it seems like no (synthesized) events are discarded and the latency occurs as explained in QTBUG-14102