-- for k,v in pairs( event ) do
By uncommenting that you can know what is inside the table, and here is the component:
pressure, x, y, tiltX, tiltY, pointerType (can indicate whether it is pen or eraser), tangentialPressure (this is rare i think, only for airbrush type)
Actually there is still z & rotation, but i don't think i it is needed, so i removed them.
I believe it would work on Mac, because this is native in the Qt engine.
For Android/iOS, i think it would be "event.touch.pressure", because when i read about touch event, actually there is data to know whether it is finger or pen (different from this pentablet).