C / C++ / MFC

void CMainFrame::WinHelp(DWORD dwData, UINT nCmd) 
{
	// original MFC implementation
	
	CWinApp* pApp = AfxGetApp();
	ASSERT_VALID(pApp);
	ASSERT(pApp->m_pszHelpFilePath != NULL);

	CWaitCursor wait;
	if (IsFrameWnd())
	{
		// CFrameWnd windows should be allowed to exit help mode first
		CFrameWnd* pFrameWnd = (CFrameWnd*)this;
		pFrameWnd->ExitHelpMode();
	}

	// cancel any tracking modes
	SendMessage(WM_CANCELMODE);
	SendMessageToDescendants(WM_CANCELMODE, 0, 0, TRUE, TRUE);

	// need to use top level parent (for the case where m_hWnd is in DLL)
	CWnd* pWnd = GetTopLevelParent();
	pWnd->SendMessage(WM_CANCELMODE);
	pWnd->SendMessageToDescendants(WM_CANCELMODE, 0, 0, TRUE, TRUE);

	// attempt to cancel capture
	HWND hWndCapture = ::GetCapture();
	if (hWndCapture != NULL)
		::SendMessage(hWndCapture, WM_CANCELMODE, 0, 0);

	//TRACE3("WinHelp: pszHelpFile = '%s', dwData: $%lx, fuCommand: %d.\n",
	//	pApp->m_pszHelpFilePath, dwData, nCmd);

	// finally, run the Windows Help engine
	//if (!::WinHelp(pWnd->m_hWnd, pApp->m_pszHelpFilePath, nCmd, dwData))
	//	AfxMessageBox(AFX_IDP_FAILED_TO_LAUNCH_HELP);

	TRACE0("*** HtmlHelp(");
	DWORD dwHtmlData = 0;
	UINT nHtmlCmd;
	switch (nCmd)
	{
	case HELP_CONTEXT:
		TRACE0("Context");
		nHtmlCmd = HH_HELP_CONTEXT;
		dwHtmlData = dwData;
		break;
	case HELP_CONTENTS:
		TRACE0("TOC");
		nHtmlCmd = HH_DISPLAY_TOC;
		break;
	default:
		TRACE0("other");
		nHtmlCmd = HH_DISPLAY_TOC;
	}

    // get the html help filename here
    CString strHelpFile = ...;

	TRACE("): %s %x %d (wh:%d)\n", strHelpFile, dwHtmlData, nHtmlCmd, nCmd);
	if (NULL == ::HtmlHelp(m_hWnd, strHelpFile, nHtmlCmd, dwHtmlData))
	{
		AfxMessageBox(AFX_IDP_FAILED_TO_LAUNCH_HELP);
	}
}

// @cmember Get help file name from instance

static void GetHtmlHelpFileName (HINSTANCE hInstance,
    LPTSTR pszHelpFile, int nMaxChar)
{

    //
    // Get the module name
    //

    TCHAR szBuff [_MAX_PATH];
    ::GetModuleFileName (hInstance, szBuff, _MAX_PATH);

    //
    // Remove extension
    //

    LPTSTR pszExt = _tcsrchr (szBuff, '.');
    _ASSERTE (pszExt != NULL);
    _ASSERTE (*pszExt == '.');
    *pszExt = 0;

    //
    // Add extension
    //

    _tcscat (pszExt, _T (".chm"));

    //
    // Copy to destination
    //

    _tcsncpy (pszHelpFile, szBuff, nMaxChar);
    pszHelpFile [nMaxChar - 1] = 0;
    return;
}