arc of circle?

There isn't currently a way to draw an arc using VCODES. There are 2 ways you could implement this currently. You could create an arc on an image (jpg or png), then draw that image on a target. You could also draw a circle and place another target which is black over it partially. Obviously neither of these work very well if you want to dynamically change how much of the arc you are drawing.  Please let us know a bit more about what you want to do if neither of these solutions work for you so we can think about adding this as a feature.