//--------------------------------------------------------------------
        void Sort()
        {
            if (m_auto_close)
            {
                ClosePolygon();
            }

            m_cellAARas.SortCells();
        }
            /// <summary>
            /// sort cell, and return total cell count
            /// </summary>
            /// <returns></returns>
            public int SortCells()
            {
#if DEBUG
                if (_dbugLockSortCell)
                {
                    throw new NotSupportedException();
                }
#endif
                _cellAARas.SortCells();
                return(_cellAARas.TotalCells);
            }