Adding Handlers With Class Wizard:
Whenever a handler is added, the class wizard places the prototype for the message handler in the header (.H) file. It gives a skeleton handler in the implementation file (.cpp) in the class that is placed in the base class combo box. It also adds the messagemap entry which connects the message and the handler in the implementation file. For illustration, for the WM_LBUTTONDOWN message, the prototype afx_msg void OnLButtonDown( UINT nFlags, CPoint point) is inserted in the header (.H) file by the class wizard. The class wizard includes the skeleton handler in the implementation file (.cpp). The skeleton handler would look as shown below:
void CAppView :: OnLButtonDown( UINT nFlags, CPoint point)
Also the class wizard inserts an entrance in the Message_Map macro.
BEGIN_MESSAGE_MAP( CAppView, CView)