Zedgraph悬停时显示内容闪烁的解决

        // weng modified on 20170531 1016
        private Point lastMovedPoint;
        private Point HandleCursorValues( Point mousePt )
        {
            GraphPane pane = _masterPane.FindPane( mousePt );
            if (pane != null && pane.Chart._rect.Contains(mousePt) && !mousePt.Equals(lastMovedPoint))
            {
                double x, x2, y, y2;
                bool isShowYAxis2Value;

                pane.ReverseTransform( mousePt, out x, out x2, out y, out y2 );
                string xStr = MakeValueLabel( pane.XAxis, x, -1, true );
                string yStr = MakeValueLabel( pane.YAxis, y, -1, true );
                string y2Str = MakeValueLabel( pane.Y2Axis, y2, -1, true );
                isShowYAxis2Value = GraphPane.Y2Axis.IsVisible;

                this.pointToolTip.AutomaticDelay = 500;
                this.pointToolTip.SetToolTip( this, "( " + xStr + ", " + yStr + (isShowYAxis2Value?(", " + y2Str):"") + " )" );
                this.pointToolTip.Active = true;
                lastMovedPoint = mousePt;
            }
            else if (pane == null || !pane.Chart._rect.Contains(mousePt))
                this.pointToolTip.Active = false;

            return mousePt;
        }