由于整个Windows是图形显示系统，因此对系统而言，用户程序的每一个界面、窗口都是系统的一个画布。程序员可以利用这一特点来实现窗口的特殊效果。-Because Windows is the graphical display of the system, therefore the system, the user interface of each program, the window system is a canvas. Programmers can use this characteristic to achieve special effects window.