KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q80125: INFO: Terminating the Creation of an MDI Child Window

Article: Q80125
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): kb16bitonly kbMDI kbSDKPlatform kbWndw
Last Modified: 11-JUN-1999

3.00 3.10
WINDOWS
kbprg

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

- Microsoft Windows Software Development Kit (SDK) 3.1 
-------------------------------------------------------------------------------

SUMMARY
=======

In an application designed with the Microsoft Windows Multiple Document
Interface (MDI), there are situations in which it is desirable to destroy an MDI
child window during the processing of its WM_CREATE message. For example, the
design of the application may require terminating window creation if a memory
allocation needed to hold data for an MDI child fails.

Unfortunately, returning -1 to end processing of the WM_CREATE message will not
cleanly destroy the child window. Similarly, posting a WM_CLOSE message will
cause the display to flash as the child is drawn, made active, and destroyed.
This article describes a technique to avoid this unacceptable visual effect.

To avoid the flash, the application can clear the redraw flag for the MDI client
window. This prevents the MDI client window and its children from painting. The
remainder of this article contains code to implement this technique.

Before the application processes the MDI child window's WM_CREATE message, it
does not change its display to reflect the new child window. If the application
determines that it must abort creating the MDI child window at this time, it
should clear the MDI client window's redraw flag and post a WM_CLOSE message to
the child window. When the application processes the WM_DESTROY message, turn
the redraw flag back on. The following code demonstrates these steps:

     case WM_CREATE:

      ...

         if (DestroyMePolitely)
             {
             SendMessage(hWndMDIClient, WM_SETREDRAW, FALSE, 0L);
             PostMessage(hWnd, WM_CLOSE, 0, 0L);
             }
         break;

     ...

     case WM_DESTROY:
         SendMessage(hWndMDIClient, WM_SETREDRAW, TRUE, 0L);

Additional query words: 3.00 3.10

======================================================================
Keywords          : kb16bitonly kbMDI kbSDKPlatform kbWndw 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1
Issue type        : kbinfo

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

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.