Q125435: PRB: Hidden MDI Child Window Causes Corrupted MDI Window Menu

Article: Q125435
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbMDI kbMenu kbMFC kbVC kbGrpDSMFCATL
Last Modified: 06-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, versions 1.0, 1.5 
   - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 2.1, 2.2, 4.0, 4.1, 4.2 
-------------------------------------------------------------------------------

SYMPTOMS
========

If an MDI child window is hidden or disabled, the Window menu is not properly
updated for the visible MDI child windows. Specifically, the Window menu
continues to show deleted MDI child windows or fails to add new MDI child
windows to the list.

CAUSE
=====

These problems occur only after at least one MDI child window has been
destroyed. When Windows destroys an MDI child window, it moves activation to a
different window. This activation change causes MFC to change and refresh the
MDI frame window's menu. Windows does not handle this menu refresh message
correctly while in the process of destroying an MDI child window when other
windows are hidden or disabled. This problem does not occur if the window being
destroyed is hidden or disabled.

RESOLUTION
==========

To work around this problem, program your application to ensure that that an MDI
child window is always hidden or disabled before it is destroyed. The
destruction of MDI child windows is managed by the MDICLIENT window in the
processing of the WM_MDIDESTROY message. You can customize the behavior of this
message as follows:

1. Subclass the MDICLIENT window and provide a handler for the message. For an
  example that shows how to subclass the MDICLIENT window, please see the
  following article in the Microsoft Knowledge Base:

  Q129471 How to SubClass the MDIClient by Using MFC

2. Add a message handler for the WM_MDIDESTROY message to the class used to
  subclass the MDICLIENT window; this example calls it the CMDIClientWnd class.
  This message is not listed by ClassWizard, so you will need to add the
  handler manually. For additional information about how to do this, please see
  the following article in the Microsoft Knowledge Base:

  Q99848 Use ON_MESSAGE() Macro to Map Less-Common Messages

3. Implement the OnMDIDestroy function as follows:

  LRESULT CMDIClientWnd::OnMDIDestroy(WPARAM wParam,LPARAM lParam)
     {

        // wParam contains the hwnd of the child being destroyed
        HWND hwndChild = (HWND) wParam;
        ::ShowWindow(hwndChild,SW_HIDE);
        return Default();
     };

NOTE: It has been reported that in some cases, a call to
::EnableWindow(hwndChild,FALSE); is required before the call to ::ShowWindow.

Additional query words:

======================================================================
Keywords          : kbMDI kbMenu kbMFC kbVC kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.