当用鼠标左键点下绘制正方形，拖动鼠标会产生正方形线，右键探出菜单，退出，放大，缩小。When you press left botton,it will be genereted a squre,move it will display your track with square,right botton will pop menu,include exit,zoom in,zoom out-When the next point with the left mouse button draw a square, drag the mouse will produce a square line, right-out menu, exit, zooming and narrow. When you press left botton, it will be genereted a squre, move it will display your track with square, right botton will pop menu, include exit, zoom in, zoom out