测试鼠标是否点击到直线上。仅仅是提供了一个函数，有需要的朋友只需要载入这个函数即可。 计算的方法是利用点到直线的距离公式。-Test whether the mouse click to the line. Merely provides a function, a friend in need this function only needs to load. Method of calculation is the use of point to line distance formul