如何实现MDI主应用程序的窗体背景呢，答案是采用超级武器---子类化，这样主程序的背景处理部分就由我们自己的类来处理了！具体实现代码如下！从CWnd派生一个类CBGColorWnd,然后分别处理WM_ERASEBKGND和WM_SIZE即可

Small and handy control resizer utility. Register every control s sizes and pass WM_SIZE to utility

Small and handy control resizer. Register every control you need to resize and pass WM_SIZE message to resizer

自己写的SizeManager类，用来管理窗口上子控件的Size，在主窗口的WM_SIZE消息响应函数中调用即可，可自动改变控件的大小和位置。-Write your own SizeManager class, used to manage the child window controls Size, WM_SIZE message in the main window of the response function call can automatically change the siz