Comment 8 for bug 916253

Notes to self (and others); Evince, Eog, etc are patched in Ubuntu ('debian/patches/11_grip_gestures.patch') to additionally use a library called "libgrip".

For Evince, pinch to zoom (two fingers) and X/Y scroll (two fingers) both work. This both have a 0.5-second delay before anything happens, and these both are jerky; but they do now work. The stacks used appears to be that:

  Evince talks to Gtk+ and Grip.
  Libgrip appears to talks to some other stuff including (I think) Geis.
  The other stuff including (I think) Geis eventually talks to X11.
  X11 in-turn talks to the kernel via /dev/input/event* (symlinked from /dev/input/wacom-touch).

Per Richard above, you can enable/disable the last step of X11 talking to the kernel and exclusively binding to /dev/input/wacom-touch with:

  xinput set-prop 'Wacom ISDv4 E6 Finger touch' 'Device Enabled' 0
  xinput set-prop 'Wacom ISDv4 E6 Finger touch' 'Device Enabled' 1

however, there's no need to do this as, as two-finger multitouch events appears to be being pass all the way down the stack anyway. For debugging, I found:

  geisview, GUI that dumps the Gesture availability tree
  geistest, crashes
  pygeis, crashes

For talking to the kernel; use "xinput set-prop 'Wacom ISDv4 E6 Finger touch' 'Device Enabled' 0" first:

  mtview, talks to kernel /dev/input directly, not via Grip or Geis
  input-events, use with raw device number (eg. '8') to get MT events