Re: tooltip for controls on a dialog application

I try to add tooltips for my controls on a dialog application.

in OnInitDialog(), I add :

EnableToolTips(TRUE);

Then I add ON_NOTIFY_EX(TTN_NEEDTEXT, 0, OnToolTipNotify) in message
map:

BEGIN_MESSAGE_MAP(CMFC_ZoomDlg, CDialog)
...
ON_NOTIFY_EX(TTN_NEEDTEXT, 0, OnToolTipNotify)
...
END_MESSAGE_MAP()

and:

BOOL CMFC_TestDlg::OnToolTipNotify( UINT unId, NMHDR *pstNMHDR,
LRESULT *pstResult )
{
        UNUSED_ALWAYS (pstResult);
        UNUSED_ALWAYS (unId);
        TOOLTIPTEXT* pstTTT = (TOOLTIPTEXT * )pstNMHDR;
        UINT nID = pstNMHDR->idFrom;
        if ((pstTTT->uFlags & TTF_IDISHWND))
        {
                // idFrom is actually the HWND of the too=

                nID = ::GetDlgCtrlID((HWND)nID);

                pstTTT->lpszText = _T("Hello");
                pstTTT->hinst = AfxGetResourceHandle();
                return(TRUE);
        }
        return (FALSE);

}

On my dialog, I have some EditBox, RadioButton, Button ComboBox. But
some control show tooltips and others not. Could someone tell me why?