生成一个坐标轴，鼠标在坐标轴范围内左击一下，捕获一个坐标并在该位置生成一个小叉叉，并在坐标的右上角生成一个小方框，储存坐标值-Generate a coordinate axis, the mouse left click within the scope of the axis about to capture a coordinate and generate a small cross at that location, and generates a small box in the upper right corner coordinates, the coordinate value store