Fixes steps ticks not highlighted under current value in RTL.
Fixes slider groove visibly collapsing in front of a handle near the
start of a slider, i.e. close to the
from value by extending the
groove up to at least a half of the handle, but still filling 100% space
value === to.
Removes duplicated (identical) code for an extra tick: it works just as fine with an incremented numeric model.
Rounds up all potentially floating sizes to ensure that there are no visual glitches or off-by-one-pixel jumps back and forth.
Simple test for mirroring and edge cases:
Note the lack of blue tick highlighting on the bottom, and the subtly gray ends of sliders on the second row.
(Top is en_US, bottom is ar_EG. Until Qt 6.2 it was not possible to unmirror controls)