Q133308

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page	Q133308: PRB: WM_HELP Message Not Received When F1 Pressed on Menu	/kb/133/Q133308/

Q133308: PRB: WM_HELP Message Not Received When F1 Pressed on Menu

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Article: Q133308
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbcode kbnokeyword kbMenu kbMFC kbVC210 kbVC220 kbprb kbGrpDSMFCATL
Last Modified: 29-AUG-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - *EDITOR Please do not choose this product*Microsoft Visual C++ 32-bit Edition* use 241, 265, 225, versions 2.1, 2.2 
-------------------------------------------------------------------------------

SYMPTOMS
========

Windows 95 and Windows NT version 3.51 support a new Windows message, WM_HELP.
If a menu is active when F1 is pressed, WM_HELP should be sent to the window
associated with the menu by Windows. However, with an MFC application, the
WM_HELP message never gets sent.

This problem does not occur in Visual C++ 4.0 or later

CAUSE
=====

MFC defines default handling of the F1 key to bring up help for menu items. For
more information about F1 help within an MFC application, please see MFC
Technote #28 and the Scribble Tutorial.

The F1 key is handled by the CWinThread::ProcessMessageFilter() function. It
causes the MFC function OnCommandHelp() to be called, which brings up help for
the currently selected menu item.

RESOLUTION
==========

To work around this behavior, either use the help system provided by MFC, or
override ProcessMessageFilter() for your CWinApp-derived class to by-pass the
MFC processing of the F1 key. For example, the code might look like this:

  static BOOL AFXAPI IsHelpKey(LPMSG lpMsg)
     // return TRUE only for non-repeat F1 keydowns.
  {
     return lpMsg->message == WM_KEYDOWN &&
  #ifndef _MAC
           lpMsg->wParam == VK_F1 &&
  #else
           lpMsg->wParam == VK_HELP &&
  #endif
           !(HIWORD(lpMsg->lParam) & KF_REPEAT) &&
           GetKeyState(VK_SHIFT) >= 0 &&
           GetKeyState(VK_CONTROL) >= 0 &&
           GetKeyState(VK_MENU) >= 0;
  }

  BOOL CYourApp::ProcessMessageFilter(int code, LPMSG lpMsg)
  {
     if (IsHelpKey(lpMsg))
        return FALSE;  // pass on to Windows to do WM_HELP
                             // processing - don't use default MFC
                             // help processing

     return CWinApp::ProcessMessageFilter(code, lpMsg);
  }

REFERENCES
==========

For more information about adding F1 help to your application, please see the
following references:

- MFC Technote#28 in the online documentation

- Scribble tutorial in the online documentation

- The MFC Encyclopedia under the "Help" topic

Additional query words: 2.10 2.20 3.1 3.10 3.2 3.20 4.00 Win95

======================================================================
Keywords          : kbcode kbnokeyword kbMenu kbMFC kbVC210 kbVC220 kbprb kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:
Issue type        : kbprb

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