asymmetric hand controller actions

[avrljk]

Most A-Painter users paint with one hand, seldom using their other hand controller's trigger, touchpad, joystick, grips and butons. The other hand controller is mostly used for positioning the palette of painting tools.

Novices users would be unlikely to notice if the non-painting hand controller's input devices were remapped to convenient actions for other users.

#214, #180