CodeBox for Windows Forms

using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
using TextUtils;
using WinFormsCodeBox.Decorations;
using System.Diagnostics;
namespace WinFormsCodeBox
{
    class PreparedDecorationCollection
    {

        private List<Decoration> mDecorations = new List<Decoration>();
        private List<TextIndexList> mIndexes = new List<TextIndexList>();
        private bool mAreDecorationsChanged;


        public bool AreDecorationsChanged
        {
            get { return mAreDecorationsChanged; }

        }
      public void  Add(Decoration decoration, TextIndexList index)
      {
          mDecorations.Add(decoration);
          mIndexes.Add(index);

      }

      public void Shift(int start, int amount)
      {
          foreach (TextIndexList tl in mIndexes)
          {
              tl.Shift(start, amount);

          }

      }

      public static PreparedDecorationCollection Merge(PreparedDecorationCollection previous, PreparedDecorationCollection current)
      {
          if (AreDecorationsSame(previous, current))
          {
              PreparedDecorationCollection merged = new PreparedDecorationCollection();
              TextIndexList differenceRanges = new TextIndexList();
              for (int i = 0; i < previous.Count; i++)
              {
                 TextIndexList previousIndex = previous.Index(i);
                 TextIndexList currentIndex = current.Index(i);
                TextIndex differenceRange =currentIndex.RangeDifferentFrom( previousIndex);
                  if (differenceRange != null && differenceRange.Length > 0)
                  {
                    differenceRanges.Add(differenceRange);
                  }
               
              }
              merged.mDifferenceRange = differenceRanges.Bounds;
              TextIndex activeArea = differenceRanges.Bounds;
              if (activeArea != null)
              {
                  for (int i = 0; i < previous.Count; i++)
                  {
                 TextIndexList currentIndex =  current.Index(i);
                 TextIndexList projected = currentIndex.Projection(activeArea);

                  if (projected.IndexLengthUpperBound() > 0)// Are there and textindexes in projected that have a length > 0
                  {
                      merged.Add(current.Decoration(i), projected);
                  }
                  }
              }

              return merged;

          }
          else
          {
              current.mAreDecorationsChanged = true;
            return current;

          }
          
      }
      private static  bool AreDecorationsSame(PreparedDecorationCollection previous, PreparedDecorationCollection current)
      {
          //please note that my comparison is by references to the Decorations
          //Though a more thourough comparison could be made the trade off aginst this quicker comparison
          //does not seem worhwhile
          if (previous.Count  == current.Count)
          {
              for (int i = 0; i < previous.Count; i++)
              {
                  if (previous.Decoration(i) != current.Decoration(i) )
                  {
                      return false;
                  }
              }
              return true;
          }
          else
          {

              return false;

          }


      }


      public Decoration Decoration(int position)
      {
          return mDecorations[position];

      }

      public TextIndexList Index(int position)
      {
          return mIndexes[position];

      }

      public int Count 
      {
          get
          {
              return mDecorations.Count;
          }

      }

      public bool HasDecorations
      {
          get
          {
              return mIndexes.Count  > 0;
          }
      }

      private TextIndex mDifferenceRange;
      public TextIndex DifferenceRange
      {
          get { return mDifferenceRange; }

      }
   public  TextIndex Bounds()
      {
          TextIndexList  boundlist = new  TextIndexList();
          foreach (TextIndexList t in this.mIndexes)
          {
              if (t!= null && t.Count > 0  )
              {
                  boundlist.Add(t.Bounds);
              }

          }
          if (boundlist.Count > 0)
          {
              return boundlist.Bounds;
          }
          else
          {
              return null;
          }

      }
    }
}