Deal with multiple-touchpad situation
As discussed in Issue 487, it is desirable to disable the touch component of a Wacom tablet sometimes, to avoid false input while drawing.
However I noticed we don't deal with a corner case of having multiple touch input devices, such as using a notebook with internal touchpad and the wacom tablet attached. When I tested this, the internal touchpad cannot be disabled when it's the only positioning device and attaching the wacom doesn't change the situation. We should probably expose individual input devices to allow to disable a particular one in thes corner case. Needs design.