/// <summary>
        /// Will return the new root (unchanged except in start-up)
        /// </summary>
        /// <summary>
        /// Processes the data event.
        /// </summary>
        /// <returns>
        /// The data event.
        /// </returns>
        /// <param name='e'>
        /// E.
        /// </param>
        /// <param name='Root'>
        /// Root.
        /// </param>
        /// <param name='VG'>
        /// V.
        /// </param>
        /// <param name='ys'>
        /// Ys.
        /// </param>
        /// <param name='CircleCheckList'>
        /// Circle check list.
        /// </param>
        /// <exception cref='Exception'>
        /// Represents errors that occur during application execution.
        /// </exception>
        public static VNode ProcessDataEvent(VDataEvent e, VNode Root, VoronoiGraph VG, double ys, out VDataNode[] CircleCheckList)
        {
            if (Root == null)
            {
                Root            = new VDataNode(e.DataPoint);
                CircleCheckList = new VDataNode[] { Root as VDataNode };
                return(Root);
            }

            //1. Find the node to be replaced
            VNode     C     = VNode.FindDataNode(Root, ys, e.DataPoint.X);
            VDataNode cData = C as VDataNode;

            if (cData == null)
            {
                throw new Exception("Can't cast to data node");
            }

            //2. Create the subtree (ONE Edge, but two VEdgeNodes)
            VoronoiEdge VE = new VoronoiEdge();

            VE.LeftData  = cData.DataPoint;
            VE.RightData = e.DataPoint;
            VE.VVertexA  = Fortune.VVUnkown;
            VE.VVertexB  = Fortune.VVUnkown;
            VG.Edges.Add(VE);

            VNode SubRoot;

            if (Math.Abs(VE.LeftData.Y - VE.RightData.Y) < 1e-10)
            {
                if (VE.LeftData.X < VE.RightData.X)
                {
                    SubRoot       = new VEdgeNode(VE, false);
                    SubRoot.Left  = new VDataNode(VE.LeftData);
                    SubRoot.Right = new VDataNode(VE.RightData);
                }
                else
                {
                    SubRoot       = new VEdgeNode(VE, true);
                    SubRoot.Left  = new VDataNode(VE.RightData);
                    SubRoot.Right = new VDataNode(VE.LeftData);
                }

                CircleCheckList = new VDataNode[] { SubRoot.Left as VDataNode, SubRoot.Right as VDataNode };
            }
            else
            {
                SubRoot             = new VEdgeNode(VE, false);
                SubRoot.Left        = new VDataNode(VE.LeftData);
                SubRoot.Right       = new VEdgeNode(VE, true);
                SubRoot.Right.Left  = new VDataNode(VE.RightData);
                SubRoot.Right.Right = new VDataNode(VE.LeftData);
                CircleCheckList     = new VDataNode[] { SubRoot.Left as VDataNode, SubRoot.Right.Left as VDataNode, SubRoot.Right.Right as VDataNode };
            }

            //3. Apply subtree
            if (C.Parent == null)
            {
                return(SubRoot);
            }

            C.Parent.Replace(C, SubRoot);

            return(Root);
        }
        /// <summary>
        /// Processes the circle event.
        /// </summary>
        /// <returns>
        /// The circle event.
        /// </returns>
        /// <param name='e'>
        /// E.
        /// </param>
        /// <param name='Root'>
        /// Root.
        /// </param>
        /// <param name='VG'>
        /// V.
        /// </param>
        /// <param name='ys'>
        /// Ys.
        /// </param>
        /// <param name='CircleCheckList'>
        /// Circle check list.
        /// </param>
        public static VNode ProcessCircleEvent(VCircleEvent e, VNode Root, VoronoiGraph VG, double ys, out VDataNode[] CircleCheckList)
        {
            VDataNode a;
            VDataNode b;
            VDataNode c;
            VEdgeNode eu;
            VEdgeNode eo;

            b = e.NodeN;
            a = VNode.LeftDataNode(b);
            c = VNode.RightDataNode(b);
            if (a == null || b.Parent == null || c == null || !a.DataPoint.Equals(e.NodeL.DataPoint) || !c.DataPoint.Equals(e.NodeR.DataPoint))
            {
                CircleCheckList = new VDataNode[] {};

                return(Root); // Abbruch da sich der Graph ver 0/00ndert hat
            }

            eu = b.Parent as VEdgeNode;
            CircleCheckList = new VDataNode[] { a, c };

            //1. Create the new Vertex
            Vector2D VNew = new Vector2D(e.Center.X, e.Center.Y);

            VG.Vertizes.Add(VNew);

            //2. Find out if a or c are in a distand part of the tree (the other is then b's sibling) and assign the new vertex
            if (eu.Left == b)    // c is sibling
            {
                eo = VNode.EdgeToRightDataNode(a);

                // replace eu by eu's Right
                eu.Parent.Replace(eu, eu.Right);
            }
            else     // a is sibling
            {
                eo = VNode.EdgeToRightDataNode(b);

                // replace eu by eu's Left
                eu.Parent.Replace(eu, eu.Left);
            }

            eu.Edge.AddVertex(VNew);
            eo.Edge.AddVertex(VNew);

            //2. Replace eo by new Edge
            VoronoiEdge VE = new VoronoiEdge();

            VE.LeftData  = a.DataPoint;
            VE.RightData = c.DataPoint;
            VE.AddVertex(VNew);
            VG.Edges.Add(VE);

            VEdgeNode VEN = new VEdgeNode(VE, false);

            VEN.Left  = eo.Left;
            VEN.Right = eo.Right;
            if (eo.Parent == null)
            {
                return(VEN);
            }

            eo.Parent.Replace(eo, VEN);

            return(Root);
        }
        /// <summary>
        /// Circles the check data node.
        /// </summary>
        /// <returns>
        /// The check data node.
        /// </returns>
        /// <param name='n'>
        /// N.
        /// </param>
        /// <param name='ys'>
        /// Ys.
        /// </param>
        public static VCircleEvent CircleCheckDataNode( VDataNode n, double ys )
        {
            VDataNode l = VNode.LeftDataNode( n );
            VDataNode r = VNode.RightDataNode( n );
            if( l == null || r == null || l.DataPoint == r.DataPoint || l.DataPoint == n.DataPoint || n.DataPoint == r.DataPoint ) {
                return null;
            }

            if( MathTools.ccw( l.DataPoint.X, l.DataPoint.Y, n.DataPoint.X, n.DataPoint.Y, r.DataPoint.X, r.DataPoint.Y, false ) <= 0 ) {
                return null;
            }

            Vector2D Center = Fortune.CircumCircleCenter( l.DataPoint, n.DataPoint, r.DataPoint );
            VCircleEvent VC = new VCircleEvent();
            VC.NodeN = n;
            VC.NodeL = l;
            VC.NodeR = r;
            VC.Center = Center;
            VC.Valid = true;
            if( VC.Y >= ys ) {
                return VC;
            }

            return null;
        }
        /// <summary>
        /// Rights the data node.
        /// </summary>
        /// <returns>
        /// The data node.
        /// </returns>
        /// <param name='Current'>
        /// Current.
        /// </param>
        public static VDataNode RightDataNode( VDataNode Current )
        {
            VNode C = Current;

            //1. Up
            do {
                if( C.Parent == null ) {
                    return null;
                }
                if( C.Parent.Right == C ) {
                    C = C.Parent;
                    continue;
                } else {
                    C = C.Parent;
                    break;
                }
            } while(true);

            //2. One Right
            C = C.Right;

            //3. Down
            while( C.Left != null ) {
                C = C.Left;
            }

            return C as VDataNode; // Cast statt 'as' damit eine Exception kommt
        }
        /// <summary>
        /// Will return the new root (unchanged except in start-up)
        /// </summary>
        /// <summary>
        /// Processes the data event.
        /// </summary>
        /// <returns>
        /// The data event.
        /// </returns>
        /// <param name='e'>
        /// E.
        /// </param>
        /// <param name='Root'>
        /// Root.
        /// </param>
        /// <param name='VG'>
        /// V.
        /// </param>
        /// <param name='ys'>
        /// Ys.
        /// </param>
        /// <param name='CircleCheckList'>
        /// Circle check list.
        /// </param>
        /// <exception cref='Exception'>
        /// Represents errors that occur during application execution.
        /// </exception>
        public static VNode ProcessDataEvent( VDataEvent e, VNode Root, VoronoiGraph VG, double ys, out VDataNode[] CircleCheckList )
        {
            if( Root == null ) {
                Root = new VDataNode( e.DataPoint );
                CircleCheckList = new VDataNode[] {Root as VDataNode};
                return Root;
            }

            //1. Find the node to be replaced
            VNode C = VNode.FindDataNode( Root, ys, e.DataPoint.X );
            VDataNode cData = C as VDataNode;

            if( cData == null ) {
                throw new Exception( "Can't cast to data node" );
            }

            //2. Create the subtree (ONE Edge, but two VEdgeNodes)
            VoronoiEdge VE = new VoronoiEdge();
            VE.LeftData = cData.DataPoint;
            VE.RightData = e.DataPoint;
            VE.VVertexA = Fortune.VVUnkown;
            VE.VVertexB = Fortune.VVUnkown;
            VG.Edges.Add( VE );

            VNode SubRoot;
            if( Math.Abs( VE.LeftData.Y - VE.RightData.Y ) < 1e-10 ) {
                if( VE.LeftData.X < VE.RightData.X ) {
                    SubRoot = new VEdgeNode( VE, false );
                    SubRoot.Left = new VDataNode( VE.LeftData );
                    SubRoot.Right = new VDataNode( VE.RightData );
                } else {
                    SubRoot = new VEdgeNode( VE, true );
                    SubRoot.Left = new VDataNode( VE.RightData );
                    SubRoot.Right = new VDataNode( VE.LeftData );
                }

                CircleCheckList = new VDataNode[] {SubRoot.Left as VDataNode, SubRoot.Right as VDataNode};
            } else {
                SubRoot = new VEdgeNode( VE, false );
                SubRoot.Left = new VDataNode( VE.LeftData );
                SubRoot.Right = new VEdgeNode( VE, true );
                SubRoot.Right.Left = new VDataNode( VE.RightData );
                SubRoot.Right.Right = new VDataNode( VE.LeftData );
                CircleCheckList = new VDataNode[] {SubRoot.Left as VDataNode, SubRoot.Right.Left as VDataNode, SubRoot.Right.Right as VDataNode};
            }

            //3. Apply subtree
            if( C.Parent == null ) {
                return SubRoot;
            }

            C.Parent.Replace( C, SubRoot );

            return Root;
        }
        /// <summary>
        /// Processes the circle event.
        /// </summary>
        /// <returns>
        /// The circle event.
        /// </returns>
        /// <param name='e'>
        /// E.
        /// </param>
        /// <param name='Root'>
        /// Root.
        /// </param>
        /// <param name='VG'>
        /// V.
        /// </param>
        /// <param name='ys'>
        /// Ys.
        /// </param>
        /// <param name='CircleCheckList'>
        /// Circle check list.
        /// </param>
        public static VNode ProcessCircleEvent( VCircleEvent e, VNode Root, VoronoiGraph VG, double ys, out VDataNode[] CircleCheckList )
        {
            VDataNode a;
            VDataNode b;
            VDataNode c;
            VEdgeNode eu;
            VEdgeNode eo;

            b = e.NodeN;
            a = VNode.LeftDataNode( b );
            c = VNode.RightDataNode( b );
            if( a == null || b.Parent == null || c == null || !a.DataPoint.Equals( e.NodeL.DataPoint ) || !c.DataPoint.Equals( e.NodeR.DataPoint ) ) {
                CircleCheckList = new VDataNode[]{};

                return Root; // Abbruch da sich der Graph ver 0/00ndert hat
            }

            eu = b.Parent as VEdgeNode;
            CircleCheckList = new VDataNode[] {a,c};

            //1. Create the new Vertex
            Vector2D VNew = new Vector2D( e.Center.X, e.Center.Y );

            VG.Vertizes.Add( VNew );

            //2. Find out if a or c are in a distand part of the tree (the other is then b's sibling) and assign the new vertex
            if( eu.Left == b ) { // c is sibling
                eo = VNode.EdgeToRightDataNode( a );

                // replace eu by eu's Right
                eu.Parent.Replace( eu, eu.Right );
            } else { // a is sibling
                eo = VNode.EdgeToRightDataNode( b );

                // replace eu by eu's Left
                eu.Parent.Replace( eu, eu.Left );
            }

            eu.Edge.AddVertex( VNew );
            eo.Edge.AddVertex( VNew );

            //2. Replace eo by new Edge
            VoronoiEdge VE = new VoronoiEdge();
            VE.LeftData = a.DataPoint;
            VE.RightData = c.DataPoint;
            VE.AddVertex( VNew );
            VG.Edges.Add( VE );

            VEdgeNode VEN = new VEdgeNode( VE, false );
            VEN.Left = eo.Left;
            VEN.Right = eo.Right;
            if( eo.Parent == null ) {
                return VEN;
            }

            eo.Parent.Replace( eo, VEN );

            return Root;
        }
        /// <summary>
        /// Edges to right data node.
        /// </summary>
        /// <returns>
        /// The to right data node.
        /// </returns>
        /// <param name='Current'>
        /// Current.
        /// </param>
        /// <exception cref='Exception'>
        /// Represents errors that occur during application execution.
        /// </exception>
        public static VEdgeNode EdgeToRightDataNode( VDataNode Current )
        {
            VNode C = Current;

            //1. Up
            do {
                if( C.Parent == null ) {
                    throw new Exception( "No Left Leaf found!" );
                }
                if( C.Parent.Right == C ) {
                    C = C.Parent;
                    continue;
                } else {
                    C = C.Parent;
                    break;
                }
            } while(true);

            return C as VEdgeNode;
        }