FIX: Dismissing Splash Screen from Component Causes Assertion

ID: Q138830

The information in this article applies to:

The Development Environment, included with:
- Microsoft Visual C++ 32-bit 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:

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);
   }

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

In the .h file, change the prototype so that it returns BOOL:
```
      BOOL PreTranslateAppMessage(MSG* pMsg); 
```

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 : kbcode kbMFC KbUIDesign kbVC kbVC410fix
Version : winnt:
Platform : winnt
Issue type :