The Yoga isn’t my laptop, so I couldn’t try out the demo right away.
What I notice with the demo and the active pen is that when I stop “drawing a line”, the pointer is stuck at the end position for a bit, even if I keep the pen close to the surface, and only starts following the actual pen position again after a bit of delay. I think when it picks up the new position again, that’s exactly when MyPaint draws the unwanted straight line. So I’d say there’s definitely something wonky with gtk, but I can’t say who is at fault for that unwanted line, which is the most annoying issue with the pen right now. The slowness is there in the demo as well, but it doesn’t bother me much since it feels like slow position tracking. I don’t know about the jagged lines since the demo doesn’t actually draw any lines so it’s hard to see how smooth the movement is. It looks okay in the demo, but then, the effect isn’t very strong.
With the wacom tablet, when I lift the pen far enough away from the tablet that it can’t pick up the position anymore and then set it down again at a new position, MyPaint doesn’t draw any unwanted lines, so there must be something different going on with the active pen, even it in the gtk-demo the effect looks the same.
EDIT: How does the whole gtk lib thing work, I wonder? Could I compile the gtk libs from source and use them to compile MyPaint against without having to switch the rest of the system over?
