Article: Q167961
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,2.1,2.2
Operating System(s):
Keyword(s): kbDocView kbMFC kbVC152bug kbVC200bug kbVC210bug kbVC220bug kbVC400fix kbGrpDSMFCATL kb
Last Modified: 17-JUL-2001
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The information in this article applies to:
- The Microsoft Foundation Classes (MFC), used with:
- Microsoft Visual C++ for Windows, 16-bit edition, version 1.52
- Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2
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SYMPTOMS
========
When you press the F1 key to display help for a window that is not a descendant
of the application's main window, it does not display the proper help text.
CAUSE
=====
MFC assumes that the currently active window is a descendant of the main window.
So, for windows that are children of the desktop, MFC routes WM_COMMANDHELP to
the mainframe instead of the active window.
RESOLUTION
==========
Add an ID_HELP command handler in the CMainFrame that searches for the active
window based on the window with the current focus and walks up the parent tree
sending the WM_COMMANDHELP message. Use the code shown in the sample code
section.
STATUS
======
Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem has been fixed in Visual C++ version
4.0.
MORE INFORMATION
================
When you press the F1 key, an ID_HELP command message is generated and is
usually routed and handled in the application's main frame message map using
CFrameWnd::OnHelp(). Then, the OnHelp functions (CFrameWnd and CWnd) finds the
active window using ::GetLastActivePopup(hWnd), thereby passing the handle to
the application's main frame. Unfortunately, this only returns windows handles
that are a descendant of hWnd. If another top-level window was active when you
pressed the F1 key, the main frame window is still used and the subsequent
WM_COMMANDHELP messages is never sent to the correct active window.
The sample code below fixes this bug by sending the message to the window with
the current focus before going through the default MFC logic.
Sample Code
-----------
//////////////////////////////////////
// HEADER file
class CMainFrame : public CMDIFrameWnd
{
afx_msg void OnHelp();
...
//////////////////////////////////////
// IMPLEMENTATION file
#include "afxpriv.h"
BEGIN_MESSAGE_MAP(CMainFrame, CMDIFrameWnd)
...
ON_COMMAND(ID_HELP, CMainFrame::OnHelp)
END_MESSAGE_MAP()
void CMainFrame::OnHelp()
{
if (m_dwPromptContext != 0)
{
if (m_dwPromptContext !=
HID_BASE_PROMPT + AFX_IDP_FAILED_TO_LAUNCH_HELP)
AfxGetApp()->WinHelp(m_dwPromptContext);
return;
}
// attempt to get help from whoever has the focus
HWND hWnd = ::GetFocus();
while (hWnd != NULL)
{
// attempt to process help
if (::SendMessage(hWnd, WM_COMMANDHELP, 0, 0))
return;
// check next parent/owner in the parent/owner chain
CWnd* pWnd = CWnd::FromHandlePermanent(hWnd);
if (pWnd != NULL)
hWnd = pWnd->GetOwner()->GetSafeHwnd();
else
// otherwise, return parent in the Windows sense
hWnd = ::GetParent(hWnd);
}
CWnd::OnHelp();
(c) Microsoft Corporation 1997, All Rights Reserved.
Contributions by Adam Kim, Microsoft Corporation
Additional query words:
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Keywords : kbDocView kbMFC kbVC152bug kbVC200bug kbVC210bug kbVC220bug kbVC400fix kbGrpDSMFCATL kbNoUpdate kbbuglist kbfixlist
Technology : kbAudDeveloper kbMFC
Version : winnt:2.0,2.1,2.2
Issue type : kbbug
Solution Type : kbfix
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