Q152074: PRB: COleMessageFilter Doesn’t Process WM_PAINT

Article: Q152074
Product(s): Microsoft C Compiler
Version(s): winnt:4.0,4.1
Operating System(s): 
Keyword(s): kbcode kbole kbMFC kbVC400 kbVC410 kbHWx86 kbGrpDSMFCATL
Last Modified: 06-MAY-2001

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

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

If an automation client calls a method of an automation server that brings up a
modal dialog, the client area below the dialog may not re-paint itself if the
dialog is moved over it.

CAUSE
=====

The painting problem occurs because the WM_PAINT messages are in the queue, but
are not dispatched.

RESOLUTION
==========

One solution is to retrieve and dispatch all WM_PAINT messages when
IMessageFilter::MessagePending is called. The sample code below demonstrates one
way for this resolution to be implemented.

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

To fix the problem with MFC, create a new class that overrides
COleMessageFilter::OnMessagePending() as described below. Then revoke the old
message filter and register this new one.

Sample Code
-----------

     // 
     // Definition of new COleMessageFilter-derived class.
     // 
     class CMyMessageFilter : public COleMessageFilter
     {
     public:
        virtual BOOL OnMessagePending(const MSG* pMsg);
     };

     // 
     // Add a member variable to the CWinApp-derived class.
     // 
     public:
        CMyMessageFilter MMF;

     // 
     // Add to the CWinApp::InitInstance after calling AfxOleInit.
     // 
        COleMessageFilter* OldFilter = AfxOleGetMessageFilter();
        OldFilter->Revoke();
        MMF.Register();

     // 
     // Definition of OnMessageFilter.
     // 
     BOOL CMyMessageFilter::OnMessagePending(const MSG* pMsg)

     {
        MSG msg;

        while (PeekMessage(&msg, NULL, WM_PAINT, WM_PAINT,
                           PM_REMOVE | PM_NOYIELD))
        {
           DispatchMessage(&msg);
        }

        if (pMsg->message == WM_PAINT) return TRUE;

        return FALSE;

     }

     // 
     // Add to CWinApp::ExitInstance.
     // 
        MMF.Revoke();
        return CWinApp::ExitInstance();

Additional query words: 2.00 2.10 2.20 4.00 4.10

======================================================================
Keywords          : kbcode kbole kbMFC kbVC400 kbVC410 kbHWx86 kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:4.0,4.1
Issue type        : kbprb

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