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2.10 2.20 4.00
WINDOWS NT
kbprg kbhowto kbcode
The information in this article applies to:
- The Microsoft Foundation Classes (MFC) included with:
Microsoft Visual C++, 32-bit Edition, versions 2.1, 2.2, 4.0
SUMMARY
To make the CToolTipCtrl class work correctly, you must call the
CToolTipCtrl::RelayEvent() function. This makes it possible for the
mouse messages to be passed to the tooltip control.
For a non-modal dialog box window in an MFC application, use the window's
CWnd::PreTranslateMessage() function to call CToolTipsCtrl::RelayEvent().
However, for a modal dialog box in MFC versions prior to 4.0, the
CDialog::PreTranslateMessage() function is not called because modal dialog
boxes have their own message loops.
In versions of MFC 4.0 and later, this is not a problem because of changes
to the implementation of DoModal. Therefore, to use CToolTipCtrl in a modal
dialog box, you need a different approach for versions prior to 4.0. This
article gives you step-by-step example that shows how to use the
CToolTipCtrl class in a MFC modal dialog box for 4.0 and prior versions.
MORE INFORMATION
Step-by-Step Examples
The following procedures generate a default MFC skeleton application and
add tooltips to the OK button on the About dialog box and the dialog box
itself.
For Versions of MFC 4.0 or Later Use These Steps:
- Use the Appwizard in Visual C++ to generate an MFC application. Call
it Tooltips, and use all the Appwizard default settings.
- Use ClassWizard to add a PreTranslateMessage override to CAboutDialog
as follows:
CAboutDialog::PreTranslateMessage(MSG* pMsg)
{
if (NULL != m_pToolTip)
m_pToolTip->RelayEvent(pMsg);
return CDialog::PreTranslateMessage(pMsg);
}
- Use ClassWizard to add a member variable for the OK button in the
CAboutDlg class, and call it m_btOK. Also, add a m_pToolTip pointer
to a CToolTipCtrl object:
class CAboutDlg : public CDialog
{
public:
CAboutDlg();
// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
CButton m_btOK;
//}}AFX_DATA
CToolTipCtrl* m_pToolTip;
//...
};
- Add code to the CAboutDlg class constructor and destructor to initialize
and release the tooltip object. You might also need to add a default
destructor first:
CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
m_pToolTip = NULL;
}
CAboutDlg::~CAboutDlg()
{
delete m_pToolTip;
}
- Override the OnInitDialog() function of the CAboutDlg class to set up
the tooltip control.
BOOL CAboutDlg::OnInitDialog()
{
CDialog::OnInitDialog();
//Set up the tooltip
m_pToolTip = new CToolTipCtrl;
if(!m_pToolTip->Create(this))
{
TRACE("Unable To create ToolTip\n");
return TRUE;
}
if(m_pToolTip->AddTool(this, "About Box"))
{
TRACE("Unable to add Dialog to the tooltip\n");
}
if (m_pToolTip->AddTool(&m_btOK,"OK Button"))
{
TRACE("Unable to add OK button to the tooltip\n");
}
m_pToolTip->Activate(TRUE);
return TRUE;
}
- Rebuild the application, and bring up the About dialog box, you will
see the tooltips.
For Versions of MFC Prior to 4.0 Use These Steps:
- Use the Appwizard in Visual C++ to generate an MFC application. Call it
Tooltips, and use all the Appwizard default settings.
- Include the <Afxcmn.h> header file in the Stdafx.h file.
- Add the following member variables to the CTooktipsApp class in the
Tooltips.h file:
class CTooltipsApp : public CWinApp
{
//...
public:
HWND m_hwndDialog;
CToolTipCtrl* m_gpToolTip;
//...
};
- Initialize the two variables in the application's constructor to NULL:
CTooltipsApp::CTooltipsApp()
{
m_hwndDialog = NULL;
m_gpToolTip = NULL;
}
- Override the CTooltipsApp::ProcessMessageFilter() function as follows:
BOOL CTooltipsApp::ProcessMessageFilter(int code, LPMSG lpMsg)
{
if (m_hwndDialog != NULL)
if (lpMsg->hwnd == m_hwndDialog ||
::IsChild(m_hwndDialog, lpMsg->hwnd))
{
if (NULL != m_gpToolTip)
m_gpToolTip->RelayEvent(lpMsg);
}
return CWinApp::ProcessMessageFilter(code, lpMsg);
}
- Use ClassWizard to add a member variable for the OK button in the
CAboutDlg class, and call it m_btOK. Also, add a m_pToolTip pointer
to a CToolTipCtrl object:
class CAboutDlg : public CDialog
{
public:
CAboutDlg();
// Dialog Data
//{{AFX_DATA(CAboutDlg)
enum { IDD = IDD_ABOUTBOX };
CButton m_btOK;
//}}AFX_DATA
CToolTipCtrl* m_pToolTip;
//...
};
- Add code to the CAboutDlg class constructor and destructor to initialize
and release the tooltip object. You might also need to add a default
destructor first:
CAboutDlg::CAboutDlg() : CDialog(CAboutDlg::IDD)
{
m_pToolTip = NULL;
}
CAboutDlg::~CAboutDlg()
{
delete m_pToolTip;
}
- Override the OnInitDialog() function of the CAboutDlg class to pass the
dialog's handle to the application:
BOOL CAboutDlg::OnInitDialog()
{
CDialog::OnInitDialog();
((CTooltipsApp*)AfxGetApp())->m_hwndDialog=m_hWnd;
if (!m_pToolTip)
{
m_pToolTip = new CToolTipCtrl;
if(!m_pToolTip->Create(this))
{
TRACE("Unable To create ToolTip\n");
return TRUE;
}
((CTooltipsApp*)AfxGetApp())->m_gpToolTip = m_pToolTip;
if(m_pToolTip->AddTool(this, "About Box"))
{
TRACE("Unable to add Dialog to the tooltip\n");
}
if (m_pToolTip->AddTool(&m_btOK,"OK Button"))
{
TRACE("Unable to add OK button to the tooltip\n");
}
m_pToolTip->Activate(TRUE);
}
return TRUE;//return TRUE unless you set the focus to a control
//EXCEPTION: OCX Property Pages should return FALSE
}
- Override the PostNcDestroy() function of the CAboutDlg class to reset
the variables in the application class:
void CAboutDlg::PostNcDestroy( )
{
CDialog::PostNcDestroy();
((CToolTipsApp*)AfxGetApp())->m_hwndDialog= NULL;
((CToolTipsApp*)AfxGetApp())->m_gpToolTip= NULL;
}
- Rebuild the application, and bring up the About dialog box, you will
see the tooltips.
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