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NF:winuser.DefMDIChildProcA

DefMDIChildProcA function (winuser.h)

Provides default processing for any window message that the window procedure of a multiple-document interface (MDI) child window does not process. (ANSI)

DefMDIChildProcA

winuser/DefMDIChildProcA

winmsg\defmdichildproc.htm

winmsg

VS|winui|~\winui\windowsuserinterface\windowing\multipledocumentinterface\multipledocumentinterfacereference\multipledocumentinterfacefunctions\defmdichildproc.htm

12/05/2018

DefMDIChildProc, DefMDIChildProc function [Windows and Messages], DefMDIChildProcA, DefMDIChildProcW, _win32_DefMDIChildProc, _win32_defmdichildproc_cpp, winmsg.defmdichildproc, winui._win32_defmdichildproc, winuser/DefMDIChildProc, winuser/DefMDIChildProcA, winuser/DefMDIChildProcW

winuser.h

Windows.h

Windows

Windows 2000 Professional [desktop apps only]

Windows 2000 Server [desktop apps only]

DefMDIChildProcW (Unicode) and DefMDIChildProcA (ANSI)

User32.lib

User32.dll

Windows

19H1

DefMDIChildProcA

winuser/DefMDIChildProcA

c++

APIRef

kbSyntax

DllExport

User32.dll

DefMDIChildProc

DefMDIChildProcA

DefMDIChildProcW

DefMDIChildProcA function

-description

Provides default processing for any window message that the window procedure of a multiple-document interface (MDI) child window does not process. A window message not processed by the window procedure must be passed to the DefMDIChildProc function, not to the DefWindowProc function.

-parameters

-param hWnd [in]

Type: HWND

A handle to the MDI child window.

-param uMsg [in]

Type: UINT

The message to be processed.

-param wParam [in]

Type: WPARAM

Additional message-specific information.

-param lParam [in]

Type: LPARAM

Additional message-specific information.

-returns

Type: LRESULT

The return value specifies the result of the message processing and depends on the message.

-remarks

The DefMDIChildProc function assumes that the parent window of the MDI child window identified by the hWnd parameter was created with the MDICLIENT class.

When an application's window procedure does not handle a message, it typically passes the message to the DefWindowProc function to process the message. MDI applications use the DefFrameProc and DefMDIChildProc functions instead of DefWindowProc to provide default message processing. All messages that an application would usually pass to DefWindowProc (such as nonclient messages and the WM_SETTEXT message) should be passed to DefMDIChildProc instead. In addition, DefMDIChildProc also handles the following messages.

Message	Response
WM_CHILDACTIVATE	Performs activation processing when MDI child windows are sized, moved, or displayed. This message must be passed.
WM_GETMINMAXINFO	Calculates the size of a maximized MDI child window, based on the current size of the MDI client window.
WM_MENUCHAR	Passes the message to the MDI frame window.
WM_MOVE	Recalculates MDI client scroll bars if they are present.
WM_SETFOCUS	Activates the child window if it is not the active MDI child window.
WM_SIZE	Performs operations necessary for changing the size of a window, especially for maximizing or restoring an MDI child window. Failing to pass this message to the DefMDIChildProc function produces highly undesirable results.
WM_SYSCOMMAND	Handles window menu commands: SC_NEXTWINDOW, SC_PREVWINDOW, SC_MOVE, SC_SIZE, and SC_MAXIMIZE.

Note

The winuser.h header defines DefMDIChildProc as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.