They're only on screen when they're being used, and we don't have
a GAL available to calculate their actual extents from (since their
text scales with zoom).
Fixes https://gitlab.com/kicad/code/kicad/issues/5845
As long as the arc angle stays below <60°, it will automatically choose between
clockwise and counter clockwise. This allows the user to choose the direction
with a simple mouse movement.