[Interest] Astropad and Tablet events

[Alexei Gilchrist]

Hi all,

I'm trying to use Astropad (app provides OsX tablet interface with an 
iPad) with an app I’ve written and I'm getting odd results with tablet 
events in QT. First of all, I've been in contact with the devs and they 
seem to think it's a QT bug rather than an Astropad bug, and in any case 
Astropad works with other graphics programs that I've tried.

I'm coding in python using pyqt and have Python 3.5.0 and QT 5.5.0 
installed.

At the level of QWidget you get an initial TabletPress event with 
pressure=0 followed immediately by a TabletRelease event with pressure>0 
at which point the rest of the stroke is only reported as mouse events, 
with are low frequency and don’t contain pressure info.

Astropad:

     TabletPress: pointer=1 pressure=0.0 tilt=(27,12)
     TabletRelease: pointer=1 pressure=0.13333334028720856 tilt=(27,12)
     MousePress
     MouseMove
     MouseMove
     ...[ many MouseMove ]...
     MouseRelease

Works as you'd expect with Wacom tablet, though accepting the tablet 
events does't stop the mouse events being fired (minor niggle):

     TabletPress: pointer=1 pressure=0.4313725531101227 tilt=(0,0)
     MousePress
     TabletMove: pointer=1 pressure=0.45098039507865906 tilt=(0,0)
     MouseMove
     TabletMove: pointer=1 pressure=0.45098039507865906 tilt=(0,0)
     TabletMove: pointer=1 pressure=0.4470588266849518 tilt=(0,0)
     ...[ many MouseMove and many more TableMove ] ...
     TabletRelease: pointer=1 pressure=0.0 tilt=(0,0)
     MouseMove
     MouseRelease

At the level of QApplication I'm seeing TabletEnterProximity and 
TabletLeaveProximity events as you'd expect.

Any ideas on how to fix or work around this? It looks like QT is getting 
confused and is interpreting the stroke on the tablet as having lifted 
and falling back to default mouse handling. I've tried re-emmiting a 
tablet press or move event from code with no joy.

Alexei
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