HOWTO: Add Tooltips for Controls on an MFC Modal Dialog Box

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++, 32-bit Editions, versions 2.1, 2.2, 4.0, 4.1, 4.2, 4.2b, 5.0, 6.0

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, the CDialog::PreTranslateMessage() function is not called because modal dialog boxes have their own message loops. Therefore, to use CToolTipCtrl in a modal dialog box, you need a different approach. This article gives a step-by-step example that shows how to use the CToolTipCtrl class in a MFC modal dialog box, it involves adding two additional member variables to the application class and overwriting the CWinApp::ProcessMessageFilter() function for the application class.

MORE INFORMATION

Step-by-Step Example

1. Use the Appwizard in Visual C++ to generate an MFC application, call it Tooltips, and use all the Appwizard default settings.



2. Include the <afxcmn.h> header file in the stdafx.h file.



3. 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;
   
         //...
      }; 




4. Initiate the two variables in the application's constructor to NULL:

   
      CTooltipsApp::CTooltipsApp()
      {
         m_hwndDialog = NULL;
         m_gpToolTip = NULL;
      } 




5. Overwrite 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);
      } 




6. 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;
   
         //...
      }; 




7. 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;
      } 




8. Overwrite the OnMouseMove() function of the CAboutDlg class to set up the tooltip control:

   
      void CAboutDlg::OnMouseMove(UINT nFlags, CPoint point)
      {
          //Set up the tooltip
          if (!m_pTooltip)
          {
             int rt;
              m_pTooltip = new CToolTipCtrl;
            rt = m_pTooltip->Create(this);
            ASSERT(rt!=0);
   
            ((CTooltipsApp*)AfxGetApp())->m_gpToolTip= m_pTooltip;
   
            rt = m_pTooltip->AddTool(this, "About Box");
            ASSERT(rt!=0);
            rt = m_pTooltip->AddTool(&m_btOK,"OK Button");
            ASSERT(rt!=0);
   
             m_pTooltip->Activate(TRUE);
          }
   
         CDialog::OnMouseMove(nFlags, point);
      } 




9. Overwrite 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;
   
         return TRUE;  // return TRUE unless you set the focus to a control
                       // EXCEPTION: OCX Property Pages should return FALSE
      } 




10. Overwrite 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;
       } 




11. Rebuild the application and bring up the About dialog box, you will see the tooltips.

Keywords : kbprg kbMFC KbUIDesign kbVC kbVC210 kbVC220 kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 kbfaq
Version : 2.1 2.2 4.0 4.1 4.2 4.2b 5.0 6.0
Platform : NT WINDOWS
Issue type : kbhowto