windows程序求助

    case WM_PAINT:

            hdc = BeginPaint (hwnd, &ps) ;

                           // Get vertical scroll bar position

            si.cbSize             = sizeof (si) ;

            si.fMask              = SIF_POS ;

            GetScrollInfo (hwnd, SB_VERT, &si) ;

            iVertPos              = si.nPos ;



                           // Get horizontal scroll bar position



            GetScrollInfo (hwnd, SB_HORZ, &si) ;

            iHorzPos              = si.nPos ;   //现在的位置



                           // Find painting limits



            iPaintBeg    = max (0, iVertPos + ps.rcPaint.top / cyChar) ;							

            iPaintEnd    = min (NUMLINES - 1,iVertPos + ps.rcPaint.bottom /cyChar);				



            for (i = iPaintBeg ; i <= iPaintEnd ; i++)

            {

                   x = cxChar * (1-iHorzPos) ;   //1减去它是否小于0了呢？？？？？？

                   y = cyChar * (1-iVertPos) ;



            TextOut (hdc, x, y,

            sysmetrics[i].szLabel,

            lstrlen (sysmetrics[i].szLabel)) ;



            TextOut (hdc, x + 22 * cxCaps, y,

            sysmetrics[i].szDesc,

            lstrlen (sysmetrics[i].szDesc)) ;





            SetTextAlign (hdc, TA_RIGHT | TA_TOP) ;



            TextOut (hdc, x + 22 * cxCaps + 40 * cxChar, y, szBuffer,

           wsprintf (szBuffer, TEXT ("%5d"),

            GetSystemMetrics (sysmetrics[i].iIndex))) ;



            SetTextAlign (hdc, TA_LEFT | TA_TOP) ;

            }



            EndPaint (hwnd, &ps) ;

            return 0 ;