This finally allows us to have predictable sliders where a wheel whill always
result in a brightness change rather than having it go from 0 to 10 which is still
below 33% in case of 3 keyboard brightness steps resulting in no change whatsoever.
It also shows 0/3, 1/3, etc instead of percentage in such cases.

Also clean up a bit, remove superfluous clipping and prevent brightness change
on popup instantiation