BUG: Assertion Failed When Opening a Second ActiveX Document (195033)

SYMPTOMS

When opening a second ActiveX document from an AppWizard-generated Active Document Container, you get an assertion failed in Olecli2.cpp line 104 (Visual C++ 6.0) or line 112 (Visual C++ 5.0):

   BOOL COleFrameHook::OnDocActivate(BOOL bActive)
   {
      ...
      COleFrameHook* pNotifyHook = m_pActiveItem->m_pInPlaceFrame;
      ...
         // Unhook top-level frame if not needed.
         if (pNotifyHook != this)
         {
            // Shouldn't be removing some other hook.
            ASSERT(pNotifyHook->m_pFrameWnd->m_pNotifyHook == pNotifyHook);
            pNotifyHook->m_pFrameWnd->m_pNotifyHook = NULL;
         }
      ...
   }

CAUSE

This problem occurs because AppWizard generates code to activate the Active document object from OnInitialUpdate [through DoVerb(OLEIVERB_SHOW)]. For many Active Document servers (or DocObject servers), this may be too early when considering that WM_INITIALUPDATE is posted to the view of the second document before WM_MDIACTIVATE is posted to the frame window of the first document.

RESOLUTION

Move the code in OnInitialUpdate() to OnMDIActivate() to make the appropriate modifications. The code should be called only once (during activation) for each Active document and it should be called before calling the base class OnMDIActivate():

   // CMyView is a CView-derived class.
   void CMyView::OnInitialUpdate()
   {
      CView::OnInitialUpdate();
      m_pSelection = NULL;  // Initialize selection.
   }

   // CChildFrame is a CMDIChildWnd-derived class.
   CChildFrame::CChildFrame()
   {
      // TODO: add member initialization code here.
      m_bFirstTime = TRUE;  // Add data member m_bFirstTime of BOOL type.
   }

   // Use ClassWizard to add this WM_MDIACTIVATE message handler to
   // the CMDIChildWnd-derived class.
   void CChildFrame::OnMDIActivate(
      BOOL bActivate, CWnd* pActivateWnd, CWnd* pDeactivateWnd)
   {
      if (m_bFirstTime && bActivate)
      {
         CView* pView = GetActiveView();
         ASSERT_VALID(pView);

         //Active documents should always be activated.
         COleDocument* pDoc = (COleDocument*) pView->GetDocument();;
         if (pDoc != NULL)
         {
            // Activate the first one...
            POSITION posItem = pDoc->GetStartPosition();
            if (posItem != NULL)
            {
               CDocItem* pItem = pDoc->GetNextItem(posItem);

               // only if it's an Active document.
               COleDocObjectItem *pDocObjectItem =
                  DYNAMIC_DOWNCAST(COleDocObjectItem, pItem);

               if (pDocObjectItem != NULL)
               {
                  pDocObjectItem->DoVerb(OLEIVERB_SHOW, pView);
               }
            }
         }

         m_bFirstTime = FALSE;
      }

      CMDIChildWnd::OnMDIActivate(bActivate, pActivateWnd, pDeactivateWnd);
   }

MORE INFORMATION

When DoVerb() is called, most Active Document servers end up calling COleClientItem::OnActivateUI(). This is responsible for setting the new value for m_pNotifyHook. The assertion check mentioned in this article occurs in COleFrameHook::OnDocActivate(), which is called from OnMDIActivate().

When a new MDI child frame window is created, the WM_INITIALUPDATE message is posted to the view window of the new MDI child frame before any WM_MDIACTIVATE message is posted. Because the given AppWizard code calls DoVerb() from OnInitialUpdate(), the m_pNotifyHook may be changed before OnMDIActivate() is called for the MDI child window being deactivated.

By forcing DoVerb() to be called from OnMDIActivate() only when being activated, we allow the deactivation of the first MDI child window to occur first.

NOTE: This assertion may appear due to other causes, so the workaround in this article may not always apply.

Steps to Reproduce Behavior

Generate an MDI AppWizard Active Document Container application.
Run the program and open two MDI child windows.
Insert a Word Active document object to both MDI child windows. Save and close the both documents.
Open the first document created in the MDI container application.
Open the second document created in the MDI container application. The assertion will occur.