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Microsoft KB Archive/175502

From BetaArchive Wiki

Article ID: 175502

Article Last Modified on 5/2/2001



APPLIES TO

  • Microsoft Internet Explorer 3.0
  • Microsoft Internet Explorer 3.01
  • Microsoft Internet Explorer 3.02
  • Microsoft Internet Explorer 4.0 128-Bit Edition
  • Microsoft Foundation Class Library 4.2, when used with:
    • Microsoft Visual C++ 4.0 Standard Edition
    • Microsoft Visual C++ 4.0 Standard Edition
    • Microsoft Visual C++ 4.1 Subscription
    • Microsoft Visual C++ 4.2 Professional Edition
    • Microsoft Visual C++ 4.2 Enterprise Edition
    • Microsoft Visual C++ 4.2 Professional Edition
    • Microsoft Visual C++ 5.0 Enterprise Edition
    • Microsoft Visual C++ 5.0 Professional Edition



This article was previously published under Q175502

SYMPTOMS

When an application creates the WebBrowser control in an MFC Regular DLL, tabbing within the WebBrowser control does not function correctly.

CAUSE

The TAB key and other dialog navigation keys are not getting processed in the context of the DLL by the IsDialogMessage function. Consequently, the proper dialog events are not being generated for the WebBrowser control.

RESOLUTION

In the DLL that is hosting the WebBrowser control, override the PreTranslateMessage for the CWnd-derived class as follows:

BOOL CDllWnd::PreTranslateMessage(MSG* pMsg)
{
   if (IsDialogMessage(pMsg))
      return TRUE;

     return CWnd::PreTranslateMessage(pMsg);
}
                

Next, export a function that can be used by a controlling application to call PreTranslateMessage as follows:

extern "C" DllExport BOOL FAR PASCAL FilterDllMsg(LPMSG lpMsg)
{
   AFX_MANAGE_STATE(AfxGetStaticModuleState())
   TRY
   {
      return AfxGetApp()->PreTranslateMessage(lpMsg);
   }
   END_TRY

   return FALSE;
}
                

In the controlling application, override the PreTranslateMessage method of your CView-derived class and call the FilterDllMsg as follows:

BOOL CWBView::PreTranslateMessage(MSG* pMsg)
{
   if (CView::PreTranslateMessage(pMsg))
      return TRUE;

   return FilterDllMsg(pMsg);
}
                

STATUS

This behavior is by design.

MORE INFORMATION

Typically, the Web Browser Control is embedded in a dialog box or CView- derived class that resides as part of a standard application. When moving WebBrowser control hosting code into an MFC Regular DLL, certain problems related to messages may occur.

A MFC Regular DLL does not have a main message pump, as does the CWinApp object of an application. When the DLL contains code that creates and hosts the WebBrowser control, dialog messages are not automatically translated for the WebBrowser control. If IsDialogMessage() is not called for these messages by the DLL, the WebBrowser control will not properly handle tabbing-related messages.

REFERENCES

For additional information, please see the following article in the Microsoft Knowledge Base:

165074 PRB: Keystroke Problems in CView/CWnd Web Browser Control


The MFC sample that demonstrates this technique is called DLLTRACE and can be found at:

Visual C++ Online Documentation: Developer Products; Visual C++; Visual C++ Samples; MFC Samples; Advanced MFC Samples; DLLTRACE

Keywords: kbprb kbcode KB175502