Equation Calculator with Graphing

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Media;
using System.Windows;

namespace CommonUtils.GraphicalCanvas
{
	public interface ICanvasItem 
	{
		void Arrange();
	}

	public class CanvasVisualGroup : Visual, ICanvasItem
	{
		public virtual bool IsEnabled {get; set;}
		public Transform RenderTransform
		{
			get
			{
				return (Transform) base.GetValue(UIElement.RenderTransformProperty);
			}
			set
			{
				base.SetValue(UIElement.RenderTransformProperty, value);
			}
		}
		public List<ICanvasItem> Items {get; private set;}
		public CanvasVisualGroup()
		{
			Items = new List<ICanvasItem>();
			IsEnabled = true;
		}
		public void Clear()
		{
			foreach (Visual item in Items)
			{
				if (item is CanvasVisualGroup)
					((CanvasVisualGroup)item).Clear();
				RemoveVisualChild(item);
			}
		}
		protected override int VisualChildrenCount
		{
			get 
			{ 
				if (!IsEnabled)
					return 0;
				return Items.Count; 
			}
		}
		protected override Visual GetVisualChild(int index)
		{
			return Items[index] as Visual;
		}
		public void UpdateChildren()
		{
			foreach (Visual v in Items)
			{
				if (VisualTreeHelper.GetParent(v) != null)
				{
					continue;
					// skip ?
				}
				if (v is CanvasVisualGroup)
					((CanvasVisualGroup)v).UpdateChildren();
				else
					this.AddVisualChild(v);
			}
		}
		public void Arrange()
		{
			foreach (ICanvasItem v in Items)
			{
				if (v is CanvasVisualGroup)
					((CanvasVisualGroup)v).RenderTransform = RenderTransform;
				v.Arrange();
			}
		}
	}
	public class CanvasLayer : CanvasVisualGroup
	{
		public virtual void NotifyOnMouseMove(CanvasSurface surface, Point point)
		{
		}
		public virtual void OnRender(CanvasSurface surface, DrawingContext drawingContext)
		{
		}
	}
}