Message maps are an MFC approach to windows programming. Instead of
writing a WinMain () function that sends messages to your WindProc and
then writing a WindProc that checks which kind of message this is and
then calls another of your functions, you just write the function that
will handle the message, and you add a message map to your class that
says, in effect, "I will handle this sort of message." The framework
handles whatever routing is required to send that message to you.
A number of macros are used in message maps:- DECLARE_MESSAGE_MAP: used
in the include file to declare that there will be a message map in the
source file.- BEGIN MESSAGE MAP: marks the beginning of the message map
in the source file.- END MESSAGE MAP: marks the end of the message map-
ON_COMMAND: used to delegate the handling of a command to a function of a
class.- ON_COMMAD_RANGS: used to handle a group of commands-
ON_MESSAGE: used to delegate the handling of a user defined message to a
function- ON_NOTIFY: used to handle the control notification message
with some extra information and calls a member function of a class.