Not only is this simpler, but it also is more correct (for explanation
why, try holding both shift keys while dragging, and just releasing one
of them - the previous code would briefly turn aspect ratio off).
A custom divisor like 24 or 32 will result in a range containing
many divisors that are already in the `Common` and `Triplets` presets.
When this happens, it can become impossible to cycle between presets,
because the preset can only be changed if the new divisor isn't already
contained within the current preset's range.