Trackballs are effectively stationary devices and can be positioned at any
rotation. They are also employed by users with impaired dexterity which
sometimes implies that they are positioned at an non-default angle to make the
buttons easier to reach.
Add a config option for rotation for trackball devices. Currently only
supported for 90-degree angles, if there is a need we can add more angles
later.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
