protected override Geometry DefiningGeometry
        {
            get
            {
                StreamGeometry geometry = new StreamGeometry();
                geometry.FillRule = FillRule.EvenOdd;
                using (StreamGeometryContext context = geometry.Open())
                {
                    context.DrawGeometry(new EllipseGeometry(new Point(CentreX, CentreY), Radius, Radius));
                    DrawGeometry(context, 0);
                    DrawGeometry(context, 90);
                    DrawGeometry(context, 180);
                    DrawGeometry(context, 134);
                }


                geometry.Freeze();

                return geometry;
            }
        }

        private void DrawGeometry(StreamGeometryContext context, double angle)
        {
            var x = CentreX + Radius * Math.Cos(angle * (Math.PI / 180.0));
            var y = CentreY + Radius * Math.Sin(angle * (Math.PI / 180.0));
            Point startPoint = new Point(x, y);

            x = CentreX + (Radius - 10) * Math.Cos(angle * (Math.PI / 180.0));
            y = CentreY + (Radius - 10) * Math.Sin(angle * (Math.PI / 180.0));
            Point endPoint = new Point(x, y);

            context.BeginFigure(startPoint, true, true);
            context.LineTo(endPoint, true, true);
        }