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MFC Programming Supplementary note:

Structures, Styles, Callbacks, and Message Maps

What do we have in this Module?

Structures Used by MFC
Styles Used by MFC
MFC Styles
Callback Functions Used by MFC
Message Maps
Message Map Macros
Message-Map Declaration and Demarcation Macros
Message-Mapping Macros
Message-Map Range Macros

This section documents the structures, styles, and callback functions used by the Microsoft Foundation Class Library and the MFC message maps.

Structures Used by MFC

The following table lists structures that are called from various member functions.

ABC Structure	HSE_VERSION_INFO Structure
ABCFLOAT Structure	HTTP_FILTER_AUTHENT Structure
AFX_EXTENSION_MODULE Structure	HTTP_FILTER_CONTEXT Structure
BITMAP Structure	HTTP_FILTER_LOG Structure
BITMAPINFO Structure	HTTP_FILTER_PREPROC_HEADERS Structure
CDaoDatabaseInfo Structure	HTTP_FILTER_RAW_DATA Structure
CDaoErrorInfo Structure	HTTP_FILTER_URL_MAP Structure
CDaoFieldInfo Structure	HTTP_FILTER_VERSION Structure
CDaoIndexFieldInfo Structure	LINGER Structure
CDaoIndexInfo Structure	LOGBRUSH Structure
CDaoParameterInfo Structure	LOGPEN Structure
CDaoQueryDefInfo Structure	MEASUREITEMSTRUCT Structure
CDaoRelationFieldInfo Structure	MINMAXINFO Structure
CDaoRelationInfo Structure	MSG Structure
CDaoTableDefInfo Structure	NCCALCSIZE_PARAMS Structure
CDaoWorkspaceInfo Structure	PAINTSTRUCT Structure
CODBCFieldInfo Structure	POINT Structure
COLORADJUSTMENT Structure	RECT Structure
COMPAREITEMSTRUCT Structure	RGNDATA Structure
CREATESTRUCT Structure	SOCKADDR Structure
DELETEITEMSTRUCT Structure	SOCKADDR_IN Structure
DEVNAMES Structure	SYSTEMTIME Structure
DHtmlUrlEventMapEntry Structure	WINDOWPLACEMENT Structure
DRAWITEMSTRUCT Structure	WINDOWPOS Structure
EXTENSION_CONTROL_BLOCK Structure	WSADATA Structure
FILETIME Structure	XFORM Structure
Table 1.

Styles Used by MFC

Use the following styles when you create the corresponding MFC object. In most cases, these styles are set in the dwStyle parameter of the class Create() function.

MFC Styles

Style	Description
Button styles	Applies to CButton Class objects, such as radio buttons, check boxes and pushbuttons. Specify a combination of styles in the dwStyle parameter of CButton::Create.
Combo-box styles	Applies to CComboBox Class objects. Specify a combination of styles in the dwStyle parameter of CComboBox::Create.
Edit styles	Applies to CEdit Class objects. Specify a combination of styles in the dwStyle parameter of CEdit::Create.
Frame-window styles	Applies to CFrameWnd Class objects. Specify a combination of styles in the dwStyle parameter of CFrameWnd::Create.
List-box styles	Applies to CListBox Class objects. Specify a combination of styles in the dwStyle parameter of CListBox::Create.
Message-box styles	Applies to AfxMessageBox items. Specify a combination of styles in the nType parameter of AfxMessageBox.
Scroll-bar styles	Applies to CScrollBar Class objects. Specify a combination of styles in the dwStyle parameter of CScrollBar::Create.
Static styles	Applies to CStatic Class objects. Specify a combination of styles in the dwStyle parameter of CStatic::Create.
Window styles	Applies to CWnd Class objects. Specify a combination of styles in the dwStyle parameter of CWnd::Create or CWnd::CreateEx.
Extended window styles	Applies to CWnd Class objects. Specify a combination of styles in the dwExStyle parameter of CWnd::CreateEx.
Table 2.

Callback Functions Used by MFC

Three callback functions appear in the Microsoft Foundation Class Library. A description of callback functions that are passed to CDC::EnumObjects, CDC::GrayString, and CDC::SetAbortProc follows this topic. Note that all callback functions must trap MFC exceptions before returning to Windows, since exceptions cannot be thrown across callback boundaries.

Message Maps

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.
Table 3.

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, OnMyCommand)

// ... More entries to handle additional commands

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. 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.

Message Map Macros

To support message maps, MFC supplies the following macros:

Message-Map Declaration and Demarcation Macros

DECLARE_MESSAGE_MAP	Declares that a message map will be used in a class to map messages to functions (must be used in the class declaration).
BEGIN_MESSAGE_MAP	Begins the definition of a message map (must be used in the class implementation).
END_MESSAGE_MAP	Ends the definition of a message map (must be used in the class implementation).
Table 4.

Message-Mapping Macros

ON_COMMAND	Indicates which function will handle a specified command message.
ON_CONTROL	Indicates which function will handle a specified control-notification message.
ON_MESSAGE	Indicates which function will handle a user-defined message.
ON_OLECMD	Indicates which function will handle a menu command from a DocObject or its container.
ON_REGISTERED_MESSAGE	Indicates which function will handle a registered user-defined message.
ON_REGISTERED_THREAD_MESSAGE	Indicates which function will handle a registered user-defined message when you have a CWinThread class.
ON_THREAD_MESSAGE	Indicates which function will handle a user-defined message when you have a CWinThread class.
ON_UPDATE_COMMAND_UI	Indicates which function will handle a specified user-interface update command message.
Table 5.

Message-Map Range Macros

ON_COMMAND_RANGE	Indicates which function will handle the range of command IDs specified in the first two parameters to the macro.
ON_UPDATE_COMMAND_UI_RANGE	Indicates which update handler will handle the range of command IDs specified in the first two parameters to the macro.
ON_CONTROL_RANGE	Indicates which function will handle notifications from the range of control IDs specified in the second and third parameters to the macro. The first parameter is a control-notification message, such as BN_CLICKED.
Table 6.

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