Variable bow thickness depending on length

If a house-style prefers to have thicker slurs (and/or ties, etc.), sometimes they can appear overly thick when their length is short. To counter this apparent increase of thickness, you can make the 'thickness property of slurs variable depending on its length.

The following snippet uses the function variable-bow-thickness which requires four values, two for min and max bow length (min-l and max-l, respectively) and two for min and max bow thickness (min-t and max-t, respectively). The final thickness is determined by the following conditions:
(Note: bow length is estimated by calculating the linear distance between its endpoints)