DOCUMENT:Q177641  05-MAY-2001  [visualc]
TITLE   :FIX: Assertion with an Insertable OLE Control
PRODUCT :Microsoft C Compiler
PROD/VER:winnt:4.0
OPER/SYS:
KEYWORDS:kbole kbMFC kbVC400 kbVC410fix kbNoUpdatekbbuglist kbfixlist

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

 - Microsoft Visual C++, version 4.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

If you try to handle a WM_LBUTTONDOWN message to get access to the IOleContainer
interface for an insertable OLE Control, the following Assertion Error occurs:

   

   Debug Assertion Failed!
   Program: ...
   File: wincore.cpp
   Line: 871

CAUSE
=====

This problem is cause by COleClientItem::XOleClientSite::GetContainer not
pushing the container's module state. As a result, the container attempts to
assert that the container's view window is present in the control module's HWND
map.

RESOLUTION
==========

To correct this problem, include the following in the call to
COleClientItem::XOleClientSite::GetContainer function: "

      STDMETHODIMP COleClientItem::XOleClientSite::GetContainer
        (LPOLECONTAINER **ppContainer)
      {
         #ifdef _DEBUG
             METHOD_PROLOGUE_EX(COleClientItem, OleClientSite)
         #else
             METHOD_PROLOGUE_EX_(COleClientItem, OleClientSite)
         #endif
      }

" (without the quotation marks)

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++, 32- bit Edition
version 4.1.

MORE INFORMATION
================

The assertion error is caused by the following sequence:

 - GetContainer calls GetDocument on the client item.

 - The client item asserts that it is valid.

 - The client item's AssertValid asserts that its document is valid.

 - The document's AssertValid asserts that its view is valid.

 - The view's AssertValid asserts that the window is valid.

 - The window asserts that its HWND is in the current module's HWND map.

Steps To Reproduce the Problem
------------------------------

1. Create a Control using the ControlWizard in Visual C++ 4.0. Make sure you set
   the "Available in InsertObject Dialog" option.

2. To this control, add a WM_LBUTTONDOWN handler as follows: "

         void CYourCtrl::OnLButtonDown(UINT nFlags, Cpoint point)
         {
            LPOLECONTAINER pContainer;
            if(SUCCEEDED(GetClientSite()->GetContainer(&pContainer)))
            {
               AfxMessageBox("We have access to IOleContainer interface");
            }
            if(pContainer)pContainer->Release();
               COleControl::OnLButtonDown(nFlags,point);
         }

   " (without the quotation marks)

3. Build the control.

4. Create a default MFC OLE Container application.

5. Build and run the container.

6. Click InsertObject on the Edit menu to insert your OLE Control.

7. Click on the control. The assertion error occurs.

Additional query words: 4.10

======================================================================
Keywords          : kbole kbMFC kbVC400 kbVC410fix kbNoUpdate kbbuglist kbfixlist
Technology        : kbVCsearch kbVC400 kbAudDeveloper
Version           : winnt:4.0
Issue type        : kbbug
Solution Type     : kbfix

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

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