本程序实现的功能：

生成一个网格图，在网格中绘制圆，圆的圆心位置和半径可由对话框给定，网格的密度要能根据圆的直径大小而改变；也左键可用鼠标在屏幕上单击确定圆心，并拖动橡皮筋再单击鼠标右键确定半径大小。

具体操作说明：

菜单中的“绘图”菜单下有两个子菜单，分别为“鼠标交互”和“对话框设置”子菜单。

点击“鼠标交互”，即可用鼠标在窗口中画圆，鼠标左键按下的位置为圆心，采用橡皮筋画法，当拖动鼠标时，可看到圆也跟随变化，当再按下鼠标右键时即得到半径，从而绘制出圆形；

也可采用对话框设置的方式来画圆，点击“对话框设置”，会弹出一个设置对话框，在此对话框上可输入圆心的X、Y坐标以及半径的值，当点击“确定”按钮之后，即在窗口中绘出指定圆心位置和大小的圆同时在窗口中绘出一个网格图，该网格图的密度随圆半径的大小而改变。

-The program features:

Generate a grid map, draw a circle in the grid, and the radius of the circle center position given by the dialog box, the grid density should be according to the size of the diameter of the circle change　also left on the screen, use the mouse to click OK center of the circle, and drag the rubber band and then click the right mouse button to determine the radius size.

Specific Instructions:

Menu in the "Drawing" menu there are two submenus, namely the "mouse interaction" and "Dialog Settings" submenu.

Click the "mouse interaction", you can use the mouse to draw a circle in the window, press the left mouse button the location of a circle, using the rubber band method of painting, when you drag the mouse, you can see the circle to follow changes when the mouse and then press right when the radius is obtained, which draw circle

Also can be a way to Circle dialog settings, click on "Settings dialog", will pop up a settings dialog, in this dialog box to enter the