Message Maps (MFC)
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The latest version of this topic can be found at 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:
BEGIN_MESSAGE_MAP(CMyDoc, CDocument)
ON_COMMAND(ID_MYCMD, &CMyDoc::OnMyCommand)
END_MESSAGE_MAP()
The ON_COMMAND macro is used to handle command messages generated by menus, buttons, and accelerator keys. Macros are available to map the following:
Windows Messages
Control notifications
User-defined messages
Command Messages
Registered user-defined messages
User-interface update messages
Ranges of 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.
Note
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.