Microsoft KB Archive/172276

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Article ID: 172276

Article Last Modified on 11/21/2006



APPLIES TO

  • Microsoft Foundation Class Library 4.2



This article was previously published under Q172276

SYMPTOMS

Applications that use CWnd::EnableTooltips to use a default CToolTipCtrl do not display the tooltip text for child windows after the Visual Studio Service Pack 1 (SP1) or Service Pack 2 (SP2) has been installed.

Other CToolTipCtrls and Tooltips inside of CToolBars work correctly.

CAUSE

The cbSize parameter of the TOOLINFO struct was changed to be of size AfxOldTOOLINFO to be compatible with older versions of the COMCTL32.DLL.

CWnd::OnToolHitTest() was not changed, and is dependent on the cbSize to be equal to the size of the new TOOLINFO struct. Since cbSize is always set to AfxOldTOOLINFO, this function fails.

RESOLUTION

Override the virtual function CWnd::OnToolHitTest() to take into account the new cbSize value.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been fixed in Visual Studio 97 Service Pack 3.

For more information, please see the following article in the Microsoft Knowledge Base:

170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why


MORE INFORMATION

Here is a sample OnToolHitTest() that implements the workaround:

   #include <WTYPES.H>
   #include "..\src\afximpl.h"

   int CSuperTipFormView::OnToolHitTest(CPoint point, TOOLINFO* pTI) const
   {

      HWND hWndChild = NULL;
      // find child window which hits the point
      // (don't use WindowFromPoint, because it ignores disabled windows)
      // see _AfxChildWindowFromPoint(m_hWnd, point);
      ::ClientToScreen(m_hWnd, &point);
      HWND hChild = ::GetWindow(m_hWnd, GW_CHILD);
      for (; hChild != NULL; hChild = ::GetWindow(hChild, GW_HWNDNEXT))
      {
         if (_AfxGetDlgCtrlID(hChild) != (WORD)-1 &&
               (::GetWindowLong(hChild, GWL_STYLE) & WS_VISIBLE))
         {
            // see if point hits the child window
            CRect rect;
            ::GetWindowRect(hChild, rect);
            if (rect.PtInRect(point))
            {
               hWndChild = hChild;
               break;
            }
         }
      }

      if (hWndChild != NULL)
      {
         // return positive hit if control ID isn't -1
         int nHit = _AfxGetDlgCtrlID(hWndChild);

         // hits against child windows always center the tip
         if (pTI != NULL && pTI->cbSize >= sizeof(AfxOldTOOLINFO))
         {
            // setup the TOOLINFO structure
            pTI->hwnd = m_hWnd;
            pTI->uId = (UINT)hWndChild;
            pTI->uFlags |= TTF_IDISHWND;
            pTI->lpszText = LPSTR_TEXTCALLBACK;

       // set TTF_NOTBUTTON and TTF_CENTERTIP if it isn't a button
       if (!(::SendMessage(hWndChild, WM_GETDLGCODE, 0, 0) &
                  DLGC_BUTTON))
               pTI->uFlags |= TTF_NOTBUTTON|TTF_CENTERTIP;
         }
         return nHit;
      }
      return -1;  // not found
   }
                

REFERENCES

For additional information, please see the following article in the Microsoft Knowledge Base:

167650 FIX: Problems with ToolTips on Windows 95


Keywords: kbbug kbfix kbnoupdate kbtooltip kbuidesign kbvs97sp3fix KB172276