INFO: Calling MFC MDI Base Class Message Handlers (93916)


The information in this article applies to:

  • The Microsoft Foundation Classes (MFC), when used with:
    • Microsoft C/C++ for MS-DOS 7.0
    • Microsoft Visual C++ for Windows, 16-bit edition 1.0
    • Microsoft Visual C++ for Windows, 16-bit edition 1.5
    • Microsoft Visual C++ for Windows, 16-bit edition 1.51
    • Microsoft Visual C++ for Windows, 16-bit edition 1.52
    • Microsoft Visual C++, 32-bit Editions 1.0
    • Microsoft Visual C++, 32-bit Editions 2.0
    • Microsoft Visual C++, 32-bit Editions 2.1
    • Microsoft Visual C++, 32-bit Editions 2.2
    • Microsoft Visual C++, 32-bit Editions 4.0
This article was previously published under Q93916

SUMMARY

In an application developed for the Microsoft Windows environment that uses the multiple document interface (MDI), an application that implements an MDI frame window or an MDI child window must pass certain messages to the default window procedure to provide default MDI functionality. When the application uses the Microsoft C++ Foundation Classes (MFC), the application calls the base class message handler after processing an MDI message to provide the default MDI behavior.

MORE INFORMATION

According to the Windows Software Development Kit (SDK) documentation for DefMDIChildProc, an application that uses MDI must pass messages to the appropriate function to provide default MDI behavior. In MFC, one of the message handling functions listed in the message map processes the MDI messages. If an application overrides the message handler for these messages, it may be necessary for the application to call the base class message handler after processing the message for MDI to function correctly.

The text below lists the messages processed by DefFrameProc() and DefMDIChildProc(), and the message handler that corresponds to each message:

Messages Processed by DefFrameProc()

   WM_COMMAND     OnCommand()
   WM_MENUCHAR    OnMenuChar()
   WM_SETFOCUS    OnSetFocus()
   WM_SIZE        OnSize()

Messages Processed by DefMDIChildProc()

   WM_CHILDACTIVATE    OnChildActivate()
   WM_GETMINMAXINFO    OnGetMinMaxInfo()
   WM_MENUCHAR         OnMenuChar()
   WM_MOVE             OnSize()
   WM_SETFOCUS         OnSetFocus()
   WM_SIZE             OnSize()
   WM_SYSCOMMAND       OnSysCommand()
If a class derived from CMDIFrameWnd overrides the OnCommand() message handler, it must call the CMDIFrameWnd::OnCommand() function for each message that it does not handle. Please refer to the Windows SDK documentation for more information about the messages processed by the DefFrameProc() and DefMDIChildProc() functions.
Modification Type:MajorLast Reviewed:12/11/2003
Keywords:kbArchitecture kbDocView kbinfo KbUIDesign KB93916
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