Implements arc-to according to the HTML Canvas spec.
A convenience function that implements the HTML arc_to functionality.
After this, the current point will be the point where the circle with the given radius touches the line from x1, y1
to x2, y2.
| this |
a path builder |
| x1 |
x coordinate of first control point |
| y1 |
y coordinate of first control point |
| x2 |
x coordinate of second control point |
| y2 |
y coordinate of second control point |
| radius |
radius of the circle |