draw-spline in dc<%>

Draws a three-point spline using the current pen.

• (send a-dc draw-spline x1 y1 x2 y2 x3 y3) -> void
     x1 : real number
     y1 : real number
     x2 : real number
     y2 : real number
     x3 : real number
     y3 : real number

  Draws a spline from (x1, y1) to (x3, y3) using (x2, y2) as the control point.

  Restrictions on the magnitude of drawing coordinates are described with dc<%>.