说明： 此程序用QuadCurve2D产生有一个控制电和两个重点的quadratic curve，并允许通过改变控制电或曲线重点的位置来绘制弧线 (this procedure with a QuadCurve2D produce electricity and control of two key quadratic curve, and allow control by changing the curve-- or to focus on the location of drawing arcs)
