VC++限制鼠标的活动范围，将鼠标限制在一定的区域内移动，比如本程序中，就是把鼠标限制在仅和窗体大小一样的区域中，也就是鼠标不能移出窗体，在到达边缘的时候，鼠标不能再向外移动，当点击“释放鼠标”后，鼠标完全恢复正常状态。-VC++ to limit the scope of activities of the mouse, the mouse is limited to moving within a certain area, such as the program is limited to only the mouse and window size in the same area, that is, the mouse can not be removed from the form, when reaching the edge of the , the mouse can not move outward, when click the "release the mouse", the mouse returned to normal state.