MARKUS

        /// move control point has same location of given pt along given delta

        /// </summary>

        /// <author>humkyung</author>

        /// <date>2019.06.20</date>

        /// <param name="pt"></param>

        /// <param name="dx"></param>

        /// <param name="dy"></param>

        public override void OnMoveCtrlPoint(Point pt, double dx, double dy)

        {

            IPath path = (this as IPath);

            Point selected = MathSet.getNearPoint(path.PointSet, pt);

            selected.X += dx;

            selected.Y += dy;

            int i = 0;

            for (i = 0; i < (this as IPath).PointSet.Count; i++)

            {

                if (pt.Equals((this as IPath).PointSet[i]))

                {

                    (this as IPath).PointSet[i] = selected;

                    break;

                }

            }

            List<Point> newPointSet = new List<Point> { };

            Point middle = new Point(path.PathData.Bounds.X + path.PathData.Bounds.Width * 0.5, path.PathData.Bounds.Y + path.PathData.Bounds.Height * 0.5);

            foreach (Point _pt in path.PointSet)

            {

                newPointSet.Add(_pt);

            }

            var ReverseP = (i + newPointSet.Count() / 2) % newPointSet.Count();

            var PreviousP = (i + (newPointSet.Count() - 1)) % newPointSet.Count();

            var NextP = (i + 1) % newPointSet.Count();

            var distance = MathSet.DistanceTo(newPointSet[ReverseP], newPointSet[i]);

            var PreviousV = MathSet.GetNormVectorBetween(newPointSet[ReverseP], newPointSet[PreviousP]);

            var l = MathSet.DotProduct(PreviousV.X, PreviousV.Y, newPointSet[i].X - newPointSet[ReverseP].X,

                newPointSet[i].Y - newPointSet[ReverseP].Y);

            newPointSet[PreviousP] = new Point(newPointSet[ReverseP].X + PreviousV.X * l, newPointSet[ReverseP].Y

                + PreviousV.Y * l);

            var NextV = MathSet.GetNormVectorBetween(newPointSet[ReverseP], newPointSet[NextP]);

            l = MathSet.DotProduct(NextV.X, NextV.Y, newPointSet[i].X - newPointSet[ReverseP].X, newPointSet[i].Y

                - newPointSet[ReverseP].Y);

            newPointSet[NextP] = new Point(newPointSet[ReverseP].X + NextV.X * l, newPointSet[ReverseP].Y + NextV.Y * l);

            path.PointSet = newPointSet;

            this.updateControl();

        }

        /// <summary>