Microsoft KB Archive/133308

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

Article ID: 133308

Article Last Modified on 11/21/2006

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APPLIES TO

 Microsoft Foundation Class Library 4.2, when used with:  Microsoft Visual C++ 2.1

 Microsoft Visual C++ 6.01 Professional Edition 

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This article was previously published under Q133308



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 && lpMsg->wParam == VK_F1 && lpMsg->wParam == VK_HELP && !(HIWORD(lpMsg->lParam) & KF_REPEAT) && GetKeyState(VK_SHIFT) >= 0 && GetKeyState(VK_CONTROL) >= 0 &&
 * 1) ifndef _MAC
 * 1) else
 * 1) endif

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); }

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