关键字：WindowsSDK 消息机制
http://www.codeproject.com/Articles/599/Windows-Message-Handling-Part-3
Handling Messages in SDK applications
Windows Classes and Window Procedures
DefWindowProc
Sending Messages
LOWORD and HIWORD macros: Split up lParam and wParam
MAKELPARAM and MAKEWPARAM macros: concatenate two 16-bit values
Dialogs
User-defined messages
Registered Windows Messages