拖动无标题窗口 通常我们是拖动标题栏来移动窗口，当没有标题栏时，该如何来拖动窗口呢？方法是 当我们在窗口区按下鼠标左键时，调用ReleaseCapture函数，释放鼠标的俘获，同时 发送移动标题栏的消息，就可以实现窗口的拖动-Usually drag the window without the title we are dragging the title bar to move the window, when there is no title bar, the window on