In entries labeled <memberFxn>, write your own member function for a derived CWnd class. Give your function any name you like. Other functions, such as OnActivate, are member functions of class CWnd. If called, they pass the message to the DefWindowProc Windows function. To process Windows notification messages, override the corresponding CWnd function in your derived class. Your function should call the overridden function in your base class to let the base class and Windows respond to the message.
In all cases, put the function prototype in the CWnd-derived class header, and code the message map entry as shown.
The following terms are used:
| Term | Definition |
| id | Any user-defined menu item ID (WM_COMMAND messages) or control ID (child window notification messages). |
| “message” and “wNotifyCode” | Windows message IDs as defined in WINDOWS.H. |
| nMessageVariable | Name of a variable that contains the return value from the RegisterWindowMessage Windows function. It must be declared NEAR. |