This library contains just one proc.
- mob.PointArrow(obj/Arrow, atom/Target, MinDistance, ArrowDistance)
- Arrow: an obj in src's client's screen to be updated.
- Target: the atom that the arrow is tracking.
- MinDistance: the minimum pixel distance between src and Target before the arrow is made visible.
- ArrowDistance: the pixel distance between the center of the screen and the arrow in the screen.