设计一个鼠标程序，在按下Ctrl键的同时按下鼠标左键，在窗口中拖动鼠标，可以画出一个圆；在按下Shift键的同时按下鼠标左键，在窗口中拖动鼠标，画出一个矩形。-The design of a mouse procedures, press the Ctrl key while pressing the left mouse button, drag the mouse in the window, you can draw a circle　in pressing Shift key while pressing the left mouse button, drag the mouse in the window , draw a rectangle.