DOCUMENT:Q138830  06-JUN-2001  [visualc]
TITLE   :FIX: Dismissing Splash Screen from Component Causes Assertion
PRODUCT :Microsoft C Compiler
PROD/VER:winnt:
OPER/SYS:
KEYWORDS:kbMFC KbUIDesign kbVC400bug kbVC410fix kbGrpDSMFCATL kbNoUpdate

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

 - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.0 
 - Microsoft Visual C++, 32-bit Professional Edition, version 4.0 
 - Microsoft Visual C++, 32-bit Learning Edition, version 4.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

Dismissing a Splash Screen Component inserted from the Component Gallery results
in an Assertion failure in Wincore.cpp on line 863. This happens only when you
try to dismiss the splash screen early by clicking on a mouse button or pressing
a key on the keyboard.

CAUSE
=====

Following is part of the code inserted by the component that is relevant to this
problem:

      CWinApp derived class' PreTranslateMessage:

         BOOL CMyApp::PreTranslateMessage(MSG* pMsg)
         {
           CSplashWnd::PreTranslateAppMessage(pMsg);

           return CWinApp::PreTranslateMessage(pMsg);
         }

The CSplashWnd::PreTranslateAppMessage() looks like this:

      void CSplashWnd::PreTranslateAppMessage()
      {
        if (c_pSplashWnd == NULL)
          return;

       if (pMsg->message == WM_KEYDOWN ||
           pMsg->message == WM_SYSKEYDOWN ||
           pMsg->message == WM_LBUTTONDOWN ||
           pMsg->message == WM_RBUTTONDOWN ||
           pMsg->message == WM_MBUTTONDOWN ||
           pMsg->message == WM_NCLBUTTONDOWN ||
           pMsg->message == WM_NCRBUTTONDOWN ||
           pMsg->message == WM_NCMBUTTONDOWN)
           {
             c_pSplashWnd->HideSplashScreen();
           }
       }

       void CSplashWnd::HideSplashScreen()
       {
         DestroyWindow();
         AfxGetMainWnd()->UpdateWindow();
       }

If a key is pressed while the splash screen is displayed, HideSplashScreen() is
called, which destroys the window. When the PreTranslateAppMessage() function
returns, CWinApp::PreTranslateMessage() is called for the message when its
window has been destroyed already.

RESOLUTION
==========

This problem can be avoided by not calling CWinApp::PreTranslateMessage() if the
splash screen window has alaredy been destroyed. Make the following
modifications to accomplish this:

1. Change the CWinApp derived class' PreTranslateMessage() from what is show in
   the "Cause" section of this article to the following:

      BOOL CMyApp::PreTranslateMessage(MSG* pMsg)
      {
       if (CSplashWnd::PreTranslateAppMessage(pMsg))
         return TRUE;

       return CWinApp::PreTranslateMessage(pMsg);
      }

2. Change the prototype and implementation of the
   CSplashWnd::PreTranslateAppMessage() function so that it returns a BOOL as
   follows:

   a. In the .h file, change the prototype so that it returns BOOL:

         BOOL PreTranslateAppMessage(MSG* pMsg);

   b. In the .cpp file, change the implementation of this function from what is
      shown in the "Cause" section of this article to this:

         BOOL CSplashWnd::PreTranslateAppMessage(MSG* pMsg)
         {
           if (c_pSplashWnd == NULL)
             return FALSE;

           if (pMsg->message == WM_KEYDOWN ||
               pMsg->message == WM_SYSKEYDOWN ||
               pMsg->message == WM_LBUTTONDOWN ||
               pMsg->message == WM_RBUTTONDOWN ||
               pMsg->message == WM_MBUTTONDOWN ||
               pMsg->message == WM_NCLBUTTONDOWN ||
               pMsg->message == WM_NCRBUTTONDOWN ||
               pMsg->message == WM_NCMBUTTONDOWN)
               {
                 c_pSplashWnd->HideSplashScreen(); // this destroys the window
                 return TRUE;  // You don't want to call
                               // CWinApp::PreTranslateMessage
               }
           return FALSE;
         }

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug was corrected in Visual C++ 4.1.

Additional query words: kbVC400bug 4.00 4.10

======================================================================
Keywords          : kbMFC KbUIDesign kbVC400bug kbVC410fix kbGrpDSMFCATL kbNoUpdate 
Technology        : kbVCsearch kbVC400 kbAudDeveloper kbVC32bitSearch
Version           : winnt:
Issue type        : kbbug
Solution Type     : kbfix

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

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 2001.