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Message Maps (MFC) 

This section of the reference lists all message mapping macros and all CWnd message-map entries along with the corresponding member function prototypes:

Category Description

WM_COMMAND Message Handler

Handles WM_COMMAND messages generated by user menu selections or menu access keys.

Child Window Notification Message Handlers

Handle notification messages from child windows.

WM_ Message Handlers

Handle WM_ messages, such as WM_PAINT.

User-Defined Message Handlers

Handle user-defined messages.

(For an explanation of the terminology and conventions used in this reference, see How to Use the Message Map Cross-Reference.)

Since Windows is a message-oriented operating system, a large portion of programming for the Windows environment involves message handling. Each time an event such as a keystroke or mouse click occurs, a message is sent to the application, which must then handle the event.

The Microsoft Foundation Class Library offers a programming model optimized for message-based programming. In this model, "message maps" are used to designate which functions will handle various messages for a particular class. Message maps contain one or more macros that specify which messages will be handled by which functions. For example, a message map containing an ON_COMMAND macro might look something like this:

    ON_COMMAND( ID_MYCMD, OnMyCommand )
    // ... More entries to handle additional commands

The ON_COMMAND macro is used to handle command messages generated by menus, buttons, and accelerator keys. Macros are available to map the following:

  • Control notifications

  • User-defined messages

  • Registered user-defined messages

  • User-interface update messages

  • Commands

  • Update handler messages

  • Control notifications

Although message-map macros are important, you generally won't have to use them directly. This is because the Properties window automatically creates message-map entries in your source files when you use it to associate message-handling functions with messages. Any time you want to edit or add a message-map entry, you can use the Properties window.


The Properties window does not support message-map ranges. You must write these message-map entries yourself.

However, message maps are an important part of the Microsoft Foundation Class Library. You should understand what they do, and documentation is provided for them.