ccontext:ArcNegative(xc, yc, radius, angle1, angle2)
radius to the current path. The
arc is centered at (xc, yc), begins at angle1 and proceeds in
the direction of decreasing angles to end at angle2. If angle2 is
greater than angle1 it will be progressively decreased by
2*#PI until it is less than angle1.
See ccontext:Arc() for more details. This function differs only in the direction of the arc between the two angles.