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 ;

问题：
1.x = cxChar * (1-iHorzPos) ; //1减去它是否小于0了呢？？？？？？ 求解释
[解决办法]
那个东西貌似是负数啊，所以-就变成正的啦