PRB: CScrollView Scroll Range Limited to 32K

RESOLUTION

You can work around the problem easily by adding support to handle scroll ranges greater than 32K to a CScrollView derived class. Override the function as follows:

   BOOL CMyScrollView::OnScroll(UINT nScrollCode, UINT nPos, BOOL
                                bDoScroll)
   {
      SCROLLINFO info;
      info.cbSize = sizeof(SCROLLINFO);
      info.fMask = SIF_TRACKPOS;

      if (LOBYTE(nScrollCode) == SB_THUMBTRACK)
      {
         GetScrollInfo(SB_HORZ, &info);
         nPos = info.nTrackPos;
      }

      if (HIBYTE(nScrollCode) == SB_THUMBTRACK)
      {
         GetScrollInfo(SB_VERT, &info);
         nPos = info.nTrackPos;
      }

      return CScrollView::OnScroll(nScrollCode, nPos, bDoScroll);
   }
				

In the code sample above, note that you can not depend on the value of nPos that is sent to the handler. It will be invalid for positions greater than 32K. Instead, use GetScrollInfo() to assign the correct position to nPos.

For additional information on this problem, click the article number below to view the article in the Microsoft Knowledge Base: NOTE: If you are trying to programatically scroll the contents in CscrollView, use the SetScrollInfo to correctly set the scroll bar information and then send or post the WM_xSCROLL message.

NOTE: Windows 95, Windows 98, Windows Millennium Edition (Me) and Win32s only support logical and device coordinates up to 32K. Because CScrollView uses logical units in SetScrollSizes(), you should specify a scroll range < 32K on when using CSrollView derived classes on these operating systems.

(c) Microsoft Corporation 1997, All Rights Reserved. Contributions by Sridhar S. Madhugiri, Microsoft Corporation