Gimp only recognizes a change in input device (from pen to mouse) when the cursor leaves the painting area.
If I paint with my pen, stop and then move my mouse it will move the cursor but the brush will still be the one from the pen (and the brush area will stay in place) and only if the cursor (now controlled by the mouse) leaves the paint area it will switch fully switch to mouse-mode (now the mouse controls the brush, and the brush is set to what ever was selected for the mouse.)
I would like gimp to switch instantly so I do not have to leave the paint area first.
Background: My tablet supports touch (in that if i use my fingers, it sends mouse (not pen) signals to gimp. - And in this touch(mouse)-mode zooming gestures work in gimp. But if I always have to move the cursor outside the painting area for gimp to recognize the change fully, that is very annoying.
Sidenote: Gimp instantly recognizes the change from pen to eraser (no need to leave the painting area) only the change to mouse is not instant.