Michael,

I spent a few hours troubleshooting using a standard 3 button mouse and here's what I learned:

- An LMB click event is generated by the tablet software when the nib is pressed against the tablet glass. There's an adjustable pressure threshold for what counts as an LMB click event.

- When I go to drag a view it's usually from a state of not having the pen against the glass, so I typically hit the glass hard enough to generate an LMB event when I start dragging and may generate LMB events while moving the pen over the glass due to inadvertent variations in pressure.

- dragging views works fine in v5 if I am careful to either press the pen buttons that emulate MMB/RMB before the pen touches the glass, or to be careful to use such light pressure when moving the pen over the glass that no LMB pointer events are generated in the moments before I press the buttons on the pen assigned to MMB/RMB

- v4 is much more tolerant of how I touch the pen to glass while simultaneously pressing an MMB or RMB emulation button on the pen. Maybe it's a matter of timing?

One clue might be something that you can reproduce with a standard mouse. Drag the view by holding RMB and moving mouse. With RMB still pressed now press LMB and continue moving mouse. The view will continue to drag with mouse movement, but it will fail to follow mouse movement after the LMB is released, even though the RMB is still pressed. Pressing the LMB back down will draw a marquee even though RMB is still pressed.

Would it be a problem to override LMB with MMB and RMB when dragging? As it stands, in both v4 and v5 the selection marquee disappears after one or a few clicks of MMB or RMB while LMB is held, so there wouldn't be a loss of function.

Don't bother fixing if it's complicated. My workaround is to set the pen nib pressure threshold for LMB emulation high so that I'm less likely to generate LMB events.




Odds and ends:
- The tablet software isn't aware of other apps. It's just a mouse and keyboard emulator as far as I can tell. I thought that this happened at the hardware level, with the tablet control software merely changing settings in the tablet USB device firmware, but that's not right since Karabiner Event Viewer doesn't recognize the tablet as an input device. So, I guess it's some sort of virtual keyboard+mouse.
- v5 recognizes RMB pointer events generated by the tablet/pen: it triggers repeat of the previous operation and works for dragging if I am careful as described above.

- Peer