DefFrameProcW function (winuser.h)

Provides default processing for any window messages that the window procedure of a multiple-document interface (MDI) frame window does not process. All window messages that are not explicitly processed by the window procedure must be passed to the DefFrameProc function, not the DefWindowProc function.


LRESULT DefFrameProcW(
  [in] HWND   hWnd,
  [in] HWND   hWndMDIClient,
  [in] UINT   uMsg,
  [in] WPARAM wParam,
  [in] LPARAM lParam


[in] hWnd

Type: HWND

A handle to the MDI frame window.

[in] hWndMDIClient

Type: HWND

A handle to the MDI client window.

[in] uMsg

Type: UINT

The message to be processed.

[in] wParam


Additional message-specific information.

[in] lParam


Additional message-specific information.

Return value


The return value specifies the result of the message processing and depends on the message. If the hWndMDIClient parameter is NULL, the return value is the same as for the DefWindowProc function.


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 DefFrameProc instead. The DefFrameProc function also handles the following messages.

Message Response
WM_COMMAND Activates the MDI child window that the user chooses. This message is sent when the user chooses an MDI child window from the window menu of the MDI frame window. The window identifier accompanying this message identifies the MDI child window to be activated.
WM_MENUCHAR Opens the window menu of the active MDI child window when the user presses the ALT+ – (minus) key combination.
WM_SETFOCUS Passes the keyboard focus to the MDI client window, which in turn passes it to the active MDI child window.
WM_SIZE Resizes the MDI client window to fit in the new frame window's client area. If the frame window procedure sizes the MDI client window to a different size, it should not pass the message to the DefWindowProc function.


The winuser.h header defines DefFrameProc 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.


Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Target Platform Windows
Header winuser.h (include Windows.h)
Library User32.lib
DLL User32.dll

See also




Multiple Document Interface