MERGE

26 files changed, 7277 insertions, 0 deletions

diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ChangeTrackingCheckpoint.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ChangeTrackingCheckpoint.cs
new file mode 100644
index 000000000..283731da8
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ChangeTrackingCheckpoint.cs
@@ -0,0 +1,140 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using Tango.Scripting.Editors.Utils;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// <para>A checkpoint that allows tracking changes to a TextDocument.</para>
+	/// <para>
+	/// Use <see cref="TextDocument.CreateSnapshot(out ChangeTrackingCheckpoint)"/> to create a checkpoint.
+	/// </para>
+	/// </summary>
+	/// <remarks>
+	/// <para>The <see cref="ChangeTrackingCheckpoint"/> class allows tracking document changes, even from background threads.</para>
+	/// <para>Once you have two checkpoints, you can call <see cref="ChangeTrackingCheckpoint.GetChangesTo"/> to retrieve the complete list
+	/// of document changes that happened between those versions of the document.</para>
+	/// </remarks>
+	public sealed class ChangeTrackingCheckpoint
+	{
+		// Object that is unique per document.
+		// Used to determine if two checkpoints belong to the same document.
+		// We don't use a reference to the document itself to allow the GC to reclaim the document memory
+		// even if there are still references to checkpoints.
+		readonly object documentIdentifier;
+		
+		// 'value' is the change from the previous checkpoint to this checkpoint
+		// TODO: store the change in the older checkpoint instead - if only a reference to the
+		// newest document version exists, the GC should be able to collect all DocumentChangeEventArgs.
+		readonly DocumentChangeEventArgs value;
+		readonly int id;
+		ChangeTrackingCheckpoint next;
+		
+		internal ChangeTrackingCheckpoint(object documentIdentifier)
+		{
+			this.documentIdentifier = documentIdentifier;
+		}
+		
+		internal ChangeTrackingCheckpoint(object documentIdentifier, DocumentChangeEventArgs value, int id)
+		{
+			this.documentIdentifier = documentIdentifier;
+			this.value = value;
+			this.id = id;
+		}
+		
+		internal ChangeTrackingCheckpoint Append(DocumentChangeEventArgs change)
+		{
+			Debug.Assert(this.next == null);
+			this.next = new ChangeTrackingCheckpoint(this.documentIdentifier, change, unchecked( this.id + 1 ));
+			return this.next;
+		}
+		
+		/// <summary>
+		/// Creates a change tracking checkpoint for the specified document.
+		/// This method is thread-safe.
+		/// If you need a ChangeTrackingCheckpoint that's consistent with a snapshot of the document,
+		/// use <see cref="TextDocument.CreateSnapshot(out ChangeTrackingCheckpoint)"/>.
+		/// </summary>
+		public static ChangeTrackingCheckpoint Create(TextDocument document)
+		{
+			if (document == null)
+				throw new ArgumentNullException("document");
+			return document.CreateChangeTrackingCheckpoint();
+		}
+		
+		/// <summary>
+		/// Gets whether this checkpoint belongs to the same document as the other checkpoint.
+		/// </summary>
+		public bool BelongsToSameDocumentAs(ChangeTrackingCheckpoint other)
+		{
+			if (other == null)
+				throw new ArgumentNullException("other");
+			return documentIdentifier == other.documentIdentifier;
+		}
+		
+		/// <summary>
+		/// Compares the age of this checkpoint to the other checkpoint.
+		/// </summary>
+		/// <remarks>This method is thread-safe.</remarks>
+		/// <exception cref="ArgumentException">Raised if 'other' belongs to a different document than this checkpoint.</exception>
+		/// <returns>-1 if this checkpoint is older than <paramref name="other"/>.
+		/// 0 if <c>this</c>==<paramref name="other"/>.
+		/// 1 if this checkpoint is newer than <paramref name="other"/>.</returns>
+		public int CompareAge(ChangeTrackingCheckpoint other)
+		{
+			if (other == null)
+				throw new ArgumentNullException("other");
+			if (other.documentIdentifier != this.documentIdentifier)
+				throw new ArgumentException("Checkpoints do not belong to the same document.");
+			// We will allow overflows, but assume that the maximum distance between checkpoints is 2^31-1.
+			// This is guaranteed on x86 because so many checkpoints don't fit into memory.
+			return Math.Sign(unchecked( this.id - other.id ));
+		}
+		
+		/// <summary>
+		/// Gets the changes from this checkpoint to the other checkpoint.
+		/// If 'other' is older than this checkpoint, reverse changes are calculated.
+		/// </summary>
+		/// <remarks>This method is thread-safe.</remarks>
+		/// <exception cref="ArgumentException">Raised if 'other' belongs to a different document than this checkpoint.</exception>
+		public IEnumerable<DocumentChangeEventArgs> GetChangesTo(ChangeTrackingCheckpoint other)
+		{
+			int result = CompareAge(other);
+			if (result < 0)
+				return GetForwardChanges(other);
+			else if (result > 0)
+				return other.GetForwardChanges(this).Reverse().Select(change => change.Invert());
+			else
+				return Empty<DocumentChangeEventArgs>.Array;
+		}
+		
+		IEnumerable<DocumentChangeEventArgs> GetForwardChanges(ChangeTrackingCheckpoint other)
+		{
+			// Return changes from this(exclusive) to other(inclusive).
+			ChangeTrackingCheckpoint node = this;
+			do {
+				node = node.next;
+				yield return node.value;
+			} while (node != other);
+		}
+		
+		/// <summary>
+		/// Calculates where the offset has moved in the other buffer version.
+		/// </summary>
+		/// <remarks>This method is thread-safe.</remarks>
+		/// <exception cref="ArgumentException">Raised if 'other' belongs to a different document than this checkpoint.</exception>
+		public int MoveOffsetTo(ChangeTrackingCheckpoint other, int oldOffset, AnchorMovementType movement)
+		{
+			int offset = oldOffset;
+			foreach (DocumentChangeEventArgs e in GetChangesTo(other)) {
+				offset = e.GetNewOffset(offset, movement);
+			}
+			return offset;
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentChangeEventArgs.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentChangeEventArgs.cs
new file mode 100644
index 000000000..17307680a
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentChangeEventArgs.cs
@@ -0,0 +1,131 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using Tango.Scripting.Editors.Utils;
+using System;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Describes a change of the document text.
+	/// This class is thread-safe.
+	/// </summary>
+	[Serializable]
+	public class DocumentChangeEventArgs : EventArgs
+	{
+		/// <summary>
+		/// The offset at which the change occurs.
+		/// </summary>
+		public int Offset { get; private set; }
+		
+		/// <summary>
+		/// The text that was removed.
+		/// </summary>
+		public string RemovedText { get; private set; }
+		
+		/// <summary>
+		/// The number of characters removed.
+		/// </summary>
+		public int RemovalLength {
+			get { return RemovedText.Length; }
+		}
+		
+		/// <summary>
+		/// The text that was inserted.
+		/// </summary>
+		public string InsertedText { get; private set; }
+		
+		/// <summary>
+		/// The number of characters inserted.
+		/// </summary>
+		public int InsertionLength {
+			get { return InsertedText.Length; }
+		}
+		
+		volatile OffsetChangeMap offsetChangeMap;
+		
+		/// <summary>
+		/// Gets the OffsetChangeMap associated with this document change.
+		/// </summary>
+		/// <remarks>The OffsetChangeMap instance is guaranteed to be frozen and thus thread-safe.</remarks>
+		public OffsetChangeMap OffsetChangeMap {
+			get {
+				OffsetChangeMap map = offsetChangeMap;
+				if (map == null) {
+					// create OffsetChangeMap on demand
+					map = OffsetChangeMap.FromSingleElement(CreateSingleChangeMapEntry());
+					offsetChangeMap = map;
+				}
+				return map;
+			}
+		}
+		
+		internal OffsetChangeMapEntry CreateSingleChangeMapEntry()
+		{
+			return new OffsetChangeMapEntry(this.Offset, this.RemovalLength, this.InsertionLength);
+		}
+		
+		/// <summary>
+		/// Gets the OffsetChangeMap, or null if the default offset map (=single replacement) is being used.
+		/// </summary>
+		internal OffsetChangeMap OffsetChangeMapOrNull {
+			get {
+				return offsetChangeMap;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the new offset where the specified offset moves after this document change.
+		/// </summary>
+		public int GetNewOffset(int offset, AnchorMovementType movementType)
+		{
+			if (offsetChangeMap != null)
+				return offsetChangeMap.GetNewOffset(offset, movementType);
+			else
+				return CreateSingleChangeMapEntry().GetNewOffset(offset, movementType);
+		}
+		
+		/// <summary>
+		/// Creates a new DocumentChangeEventArgs object.
+		/// </summary>
+		public DocumentChangeEventArgs(int offset, string removedText, string insertedText)
+			: this(offset, removedText, insertedText, null)
+		{
+		}
+		
+		/// <summary>
+		/// Creates a new DocumentChangeEventArgs object.
+		/// </summary>
+		public DocumentChangeEventArgs(int offset, string removedText, string insertedText, OffsetChangeMap offsetChangeMap)
+		{
+			ThrowUtil.CheckNotNegative(offset, "offset");
+			ThrowUtil.CheckNotNull(removedText, "removedText");
+			ThrowUtil.CheckNotNull(insertedText, "insertedText");
+			
+			this.Offset = offset;
+			this.RemovedText = removedText;
+			this.InsertedText = insertedText;
+			
+			if (offsetChangeMap != null) {
+				if (!offsetChangeMap.IsFrozen)
+					throw new ArgumentException("The OffsetChangeMap must be frozen before it can be used in DocumentChangeEventArgs");
+				if (!offsetChangeMap.IsValidForDocumentChange(offset, removedText.Length, insertedText.Length))
+					throw new ArgumentException("OffsetChangeMap is not valid for this document change", "offsetChangeMap");
+				this.offsetChangeMap = offsetChangeMap;
+			}
+		}
+		
+		/// <summary>
+		/// Creates DocumentChangeEventArgs for the reverse change.
+		/// </summary>
+		public DocumentChangeEventArgs Invert()
+		{
+			OffsetChangeMap map = this.OffsetChangeMapOrNull;
+			if (map != null) {
+				map = map.Invert();
+				map.Freeze();
+			}
+			return new DocumentChangeEventArgs(this.Offset, this.InsertedText, this.RemovedText, map);
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentChangeOperation.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentChangeOperation.cs
new file mode 100644
index 000000000..f24b7ed4d
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentChangeOperation.cs
@@ -0,0 +1,52 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Diagnostics;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Describes a change to a TextDocument.
+	/// </summary>
+	sealed class DocumentChangeOperation : IUndoableOperationWithContext
+	{
+		TextDocument document;
+		DocumentChangeEventArgs change;
+		
+		public DocumentChangeOperation(TextDocument document, DocumentChangeEventArgs change)
+		{
+			this.document = document;
+			this.change = change;
+		}
+		
+		public void Undo(UndoStack stack)
+		{
+			Debug.Assert(stack.state == UndoStack.StatePlayback);
+			stack.RegisterAffectedDocument(document);
+			stack.state = UndoStack.StatePlaybackModifyDocument;
+			this.Undo();
+			stack.state = UndoStack.StatePlayback;
+		}
+		
+		public void Redo(UndoStack stack)
+		{
+			Debug.Assert(stack.state == UndoStack.StatePlayback);
+			stack.RegisterAffectedDocument(document);
+			stack.state = UndoStack.StatePlaybackModifyDocument;
+			this.Redo();
+			stack.state = UndoStack.StatePlayback;
+		}
+		
+		public void Undo()
+		{
+			OffsetChangeMap map = change.OffsetChangeMapOrNull;
+			document.Replace(change.Offset, change.InsertionLength, change.RemovedText, map != null ? map.Invert() : null);
+		}
+		
+		public void Redo()
+		{
+			document.Replace(change.Offset, change.RemovalLength, change.InsertedText, change.OffsetChangeMapOrNull);
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentLine.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentLine.cs
new file mode 100644
index 000000000..746f31637
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentLine.cs
@@ -0,0 +1,242 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Diagnostics;
+using System.Globalization;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Represents a line inside a <see cref="TextDocument"/>.
+	/// </summary>
+	/// <remarks>
+	/// <para>
+	/// The <see cref="TextDocument.Lines"/> collection contains one DocumentLine instance
+	/// for every line in the document. This collection is read-only to user code and is automatically
+	/// updated to reflect the current document content.
+	/// </para>
+	/// <para>
+	/// Internally, the DocumentLine instances are arranged in a binary tree that allows for both efficient updates and lookup.
+	/// Converting between offset and line number is possible in O(lg N) time,
+	/// and the data structure also updates all offsets in O(lg N) whenever a line is inserted or removed.
+	/// </para>
+	/// </remarks>
+	public sealed partial class DocumentLine : ISegment
+	{
+		#region Constructor
+		#if DEBUG
+		// Required for thread safety check which is done only in debug builds.
+		// To save space, we don't store the document reference in release builds as we don't need it there.
+		readonly TextDocument document;
+		#endif
+		
+		internal bool isDeleted;
+		
+		internal DocumentLine(TextDocument document)
+		{
+			#if DEBUG
+			Debug.Assert(document != null);
+			this.document = document;
+			#endif
+		}
+		
+		[Conditional("DEBUG")]
+		void DebugVerifyAccess()
+		{
+			#if DEBUG
+			document.DebugVerifyAccess();
+			#endif
+		}
+		#endregion
+		
+		#region Events
+//		/// <summary>
+//		/// Is raised when the line is deleted.
+//		/// </summary>
+//		public event EventHandler Deleted;
+//
+//		/// <summary>
+//		/// Is raised when the line's text changes.
+//		/// </summary>
+//		public event EventHandler TextChanged;
+//
+//		/// <summary>
+//		/// Raises the Deleted or TextChanged event.
+//		/// </summary>
+//		internal void RaiseChanged()
+//		{
+//			if (IsDeleted) {
+//				if (Deleted != null)
+//					Deleted(this, EventArgs.Empty);
+//			} else {
+//				if (TextChanged != null)
+//					TextChanged(this, EventArgs.Empty);
+//			}
+//		}
+		#endregion
+		
+		#region Properties stored in tree
+		/// <summary>
+		/// Gets if this line was deleted from the document.
+		/// </summary>
+		public bool IsDeleted {
+			get {
+				DebugVerifyAccess();
+				return isDeleted;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the number of this line.
+		/// Runtime: O(log n)
+		/// </summary>
+		/// <exception cref="InvalidOperationException">The line was deleted.</exception>
+		public int LineNumber {
+			get {
+				if (IsDeleted)
+					throw new InvalidOperationException();
+				return DocumentLineTree.GetIndexFromNode(this) + 1;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the starting offset of the line in the document's text.
+		/// Runtime: O(log n)
+		/// </summary>
+		/// <exception cref="InvalidOperationException">The line was deleted.</exception>
+		public int Offset {
+			get {
+				if (IsDeleted)
+					throw new InvalidOperationException();
+				return DocumentLineTree.GetOffsetFromNode(this);
+			}
+		}
+		
+		/// <summary>
+		/// Gets the end offset of the line in the document's text (the offset before the line delimiter).
+		/// Runtime: O(log n)
+		/// </summary>
+		/// <exception cref="InvalidOperationException">The line was deleted.</exception>
+		/// <remarks>EndOffset = <see cref="Offset"/> + <see cref="Length"/>.</remarks>
+		public int EndOffset {
+			get { return this.Offset + this.Length; }
+		}
+		#endregion
+		
+		#region Length
+		int totalLength;
+		byte delimiterLength;
+		
+		/// <summary>
+		/// Gets the length of this line. The length does not include the line delimiter. O(1)
+		/// </summary>
+		/// <remarks>This property is still available even if the line was deleted;
+		/// in that case, it contains the line's length before the deletion.</remarks>
+		public int Length {
+			get {
+				DebugVerifyAccess();
+				return totalLength - delimiterLength;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the length of this line, including the line delimiter. O(1)
+		/// </summary>
+		/// <remarks>This property is still available even if the line was deleted;
+		/// in that case, it contains the line's length before the deletion.</remarks>
+		public int TotalLength {
+			get {
+				DebugVerifyAccess();
+				return totalLength;
+			}
+			internal set {
+				// this is set by DocumentLineTree
+				totalLength = value;
+			}
+		}
+		
+		/// <summary>
+		/// <para>Gets the length of the line delimiter.</para>
+		/// <para>The value is 1 for single <c>"\r"</c> or <c>"\n"</c>, 2 for the <c>"\r\n"</c> sequence;
+		/// and 0 for the last line in the document.</para>
+		/// </summary>
+		/// <remarks>This property is still available even if the line was deleted;
+		/// in that case, it contains the line delimiter's length before the deletion.</remarks>
+		public int DelimiterLength {
+			get {
+				DebugVerifyAccess();
+				return delimiterLength;
+			}
+			internal set {
+				Debug.Assert(value >= 0 && value <= 2);
+				delimiterLength = (byte)value;
+			}
+		}
+		#endregion
+		
+		#region Previous / Next Line
+		/// <summary>
+		/// Gets the next line in the document.
+		/// </summary>
+		/// <returns>The line following this line, or null if this is the last line.</returns>
+		public DocumentLine NextLine {
+			get {
+				DebugVerifyAccess();
+				
+				if (right != null) {
+					return right.LeftMost;
+				} else {
+					DocumentLine node = this;
+					DocumentLine oldNode;
+					do {
+						oldNode = node;
+						node = node.parent;
+						// we are on the way up from the right part, don't output node again
+					} while (node != null && node.right == oldNode);
+					return node;
+				}
+			}
+		}
+		
+		/// <summary>
+		/// Gets the previous line in the document.
+		/// </summary>
+		/// <returns>The line before this line, or null if this is the first line.</returns>
+		public DocumentLine PreviousLine {
+			get {
+				DebugVerifyAccess();
+				
+				if (left != null) {
+					return left.RightMost;
+				} else {
+					DocumentLine node = this;
+					DocumentLine oldNode;
+					do {
+						oldNode = node;
+						node = node.parent;
+						// we are on the way up from the left part, don't output node again
+					} while (node != null && node.left == oldNode);
+					return node;
+				}
+			}
+		}
+		#endregion
+		
+		#region ToString
+		/// <summary>
+		/// Gets a string with debug output showing the line number and offset.
+		/// Does not include the line's text.
+		/// </summary>
+		public override string ToString()
+		{
+			if (IsDeleted)
+				return "[DocumentLine deleted]";
+			else
+				return string.Format(
+					CultureInfo.InvariantCulture,
+					"[DocumentLine Number={0} Offset={1} Length={2}]", LineNumber, Offset, Length);
+		}
+		#endregion
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentLineTree.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentLineTree.cs
new file mode 100644
index 000000000..927dc3e01
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/DocumentLineTree.cs
@@ -0,0 +1,712 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+
+namespace Tango.Scripting.Editors.Document
+{
+	using LineNode = DocumentLine;
+	
+	/// <summary>
+	/// Data structure for efficient management of the document lines (most operations are O(lg n)).
+	/// This implements an augmented red-black tree.
+	/// See <see cref="LineNode"/> for the augmented data.
+	/// 
+	/// NOTE: The tree is never empty, initially it contains an empty line.
+	/// </summary>
+	sealed class DocumentLineTree : IList<DocumentLine>
+	{
+		#region Constructor
+		readonly TextDocument document;
+		LineNode root;
+		
+		public DocumentLineTree(TextDocument document)
+		{
+			this.document = document;
+			
+			DocumentLine emptyLine = new DocumentLine(document);
+			root = emptyLine.InitLineNode();
+		}
+		#endregion
+		
+		#region Rotation callbacks
+		internal static void UpdateAfterChildrenChange(LineNode node)
+		{
+			int totalCount = 1;
+			int totalLength = node.TotalLength;
+			if (node.left != null) {
+				totalCount += node.left.nodeTotalCount;
+				totalLength += node.left.nodeTotalLength;
+			}
+			if (node.right != null) {
+				totalCount += node.right.nodeTotalCount;
+				totalLength += node.right.nodeTotalLength;
+			}
+			if (totalCount != node.nodeTotalCount
+			    || totalLength != node.nodeTotalLength)
+			{
+				node.nodeTotalCount = totalCount;
+				node.nodeTotalLength = totalLength;
+				if (node.parent != null) UpdateAfterChildrenChange(node.parent);
+			}
+		}
+		
+		static void UpdateAfterRotateLeft(LineNode node)
+		{
+			UpdateAfterChildrenChange(node);
+			
+			// not required: rotations only happen on insertions/deletions
+			// -> totalCount changes -> the parent is always updated
+			//UpdateAfterChildrenChange(node.parent);
+		}
+		
+		static void UpdateAfterRotateRight(LineNode node)
+		{
+			UpdateAfterChildrenChange(node);
+			
+			// not required: rotations only happen on insertions/deletions
+			// -> totalCount changes -> the parent is always updated
+			//UpdateAfterChildrenChange(node.parent);
+		}
+		#endregion
+		
+		#region RebuildDocument
+		/// <summary>
+		/// Rebuild the tree, in O(n).
+		/// </summary>
+		public void RebuildTree(List<DocumentLine> documentLines)
+		{
+			LineNode[] nodes = new LineNode[documentLines.Count];
+			for (int i = 0; i < documentLines.Count; i++) {
+				DocumentLine ls = documentLines[i];
+				LineNode node = ls.InitLineNode();
+				nodes[i] = node;
+			}
+			Debug.Assert(nodes.Length > 0);
+			// now build the corresponding balanced tree
+			int height = GetTreeHeight(nodes.Length);
+			Debug.WriteLine("DocumentLineTree will have height: " + height);
+			root = BuildTree(nodes, 0, nodes.Length, height);
+			root.color = BLACK;
+			#if DEBUG
+			CheckProperties();
+			#endif
+		}
+		
+		internal static int GetTreeHeight(int size)
+		{
+			if (size == 0)
+				return 0;
+			else
+				return GetTreeHeight(size / 2) + 1;
+		}
+		
+		/// <summary>
+		/// build a tree from a list of nodes
+		/// </summary>
+		LineNode BuildTree(LineNode[] nodes, int start, int end, int subtreeHeight)
+		{
+			Debug.Assert(start <= end);
+			if (start == end) {
+				return null;
+			}
+			int middle = (start + end) / 2;
+			LineNode node = nodes[middle];
+			node.left = BuildTree(nodes, start, middle, subtreeHeight - 1);
+			node.right = BuildTree(nodes, middle + 1, end, subtreeHeight - 1);
+			if (node.left != null) node.left.parent = node;
+			if (node.right != null) node.right.parent = node;
+			if (subtreeHeight == 1)
+				node.color = RED;
+			UpdateAfterChildrenChange(node);
+			return node;
+		}
+		#endregion
+		
+		#region GetNodeBy... / Get...FromNode
+		LineNode GetNodeByIndex(int index)
+		{
+			Debug.Assert(index >= 0);
+			Debug.Assert(index < root.nodeTotalCount);
+			LineNode node = root;
+			while (true) {
+				if (node.left != null && index < node.left.nodeTotalCount) {
+					node = node.left;
+				} else {
+					if (node.left != null) {
+						index -= node.left.nodeTotalCount;
+					}
+					if (index == 0)
+						return node;
+					index--;
+					node = node.right;
+				}
+			}
+		}
+		
+		internal static int GetIndexFromNode(LineNode node)
+		{
+			int index = (node.left != null) ? node.left.nodeTotalCount : 0;
+			while (node.parent != null) {
+				if (node == node.parent.right) {
+					if (node.parent.left != null)
+						index += node.parent.left.nodeTotalCount;
+					index++;
+				}
+				node = node.parent;
+			}
+			return index;
+		}
+		
+		LineNode GetNodeByOffset(int offset)
+		{
+			Debug.Assert(offset >= 0);
+			Debug.Assert(offset <= root.nodeTotalLength);
+			if (offset == root.nodeTotalLength) {
+				return root.RightMost;
+			}
+			LineNode node = root;
+			while (true) {
+				if (node.left != null && offset < node.left.nodeTotalLength) {
+					node = node.left;
+				} else {
+					if (node.left != null) {
+						offset -= node.left.nodeTotalLength;
+					}
+					offset -= node.TotalLength;
+					if (offset < 0)
+						return node;
+					node = node.right;
+				}
+			}
+		}
+		
+		internal static int GetOffsetFromNode(LineNode node)
+		{
+			int offset = (node.left != null) ? node.left.nodeTotalLength : 0;
+			while (node.parent != null) {
+				if (node == node.parent.right) {
+					if (node.parent.left != null)
+						offset += node.parent.left.nodeTotalLength;
+					offset += node.parent.TotalLength;
+				}
+				node = node.parent;
+			}
+			return offset;
+		}
+		#endregion
+		
+		#region GetLineBy
+		public DocumentLine GetByNumber(int number)
+		{
+			return GetNodeByIndex(number - 1);
+		}
+		
+		public DocumentLine GetByOffset(int offset)
+		{
+			return GetNodeByOffset(offset);
+		}
+		#endregion
+		
+		#region LineCount
+		public int LineCount {
+			get {
+				return root.nodeTotalCount;
+			}
+		}
+		#endregion
+		
+		#region CheckProperties
+		#if DEBUG
+		[Conditional("DATACONSISTENCYTEST")]
+		internal void CheckProperties()
+		{
+			Debug.Assert(root.nodeTotalLength == document.TextLength);
+			CheckProperties(root);
+			
+			// check red-black property:
+			int blackCount = -1;
+			CheckNodeProperties(root, null, RED, 0, ref blackCount);
+		}
+		
+		void CheckProperties(LineNode node)
+		{
+			int totalCount = 1;
+			int totalLength = node.TotalLength;
+			if (node.left != null) {
+				CheckProperties(node.left);
+				totalCount += node.left.nodeTotalCount;
+				totalLength += node.left.nodeTotalLength;
+			}
+			if (node.right != null) {
+				CheckProperties(node.right);
+				totalCount += node.right.nodeTotalCount;
+				totalLength += node.right.nodeTotalLength;
+			}
+			Debug.Assert(node.nodeTotalCount == totalCount);
+			Debug.Assert(node.nodeTotalLength == totalLength);
+		}
+		
+		/*
+		1. A node is either red or black.
+		2. The root is black.
+		3. All leaves are black. (The leaves are the NIL children.)
+		4. Both children of every red node are black. (So every red node must have a black parent.)
+		5. Every simple path from a node to a descendant leaf contains the same number of black nodes. (Not counting the leaf node.)
+		 */
+		void CheckNodeProperties(LineNode node, LineNode parentNode, bool parentColor, int blackCount, ref int expectedBlackCount)
+		{
+			if (node == null) return;
+			
+			Debug.Assert(node.parent == parentNode);
+			
+			if (parentColor == RED) {
+				Debug.Assert(node.color == BLACK);
+			}
+			if (node.color == BLACK) {
+				blackCount++;
+			}
+			if (node.left == null && node.right == null) {
+				// node is a leaf node:
+				if (expectedBlackCount == -1)
+					expectedBlackCount = blackCount;
+				else
+					Debug.Assert(expectedBlackCount == blackCount);
+			}
+			CheckNodeProperties(node.left, node, node.color, blackCount, ref expectedBlackCount);
+			CheckNodeProperties(node.right, node, node.color, blackCount, ref expectedBlackCount);
+		}
+		
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+		public string GetTreeAsString()
+		{
+			StringBuilder b = new StringBuilder();
+			AppendTreeToString(root, b, 0);
+			return b.ToString();
+		}
+		
+		static void AppendTreeToString(LineNode node, StringBuilder b, int indent)
+		{
+			if (node.color == RED)
+				b.Append("RED   ");
+			else
+				b.Append("BLACK ");
+			b.AppendLine(node.ToString());
+			indent += 2;
+			if (node.left != null) {
+				b.Append(' ', indent);
+				b.Append("L: ");
+				AppendTreeToString(node.left, b, indent);
+			}
+			if (node.right != null) {
+				b.Append(' ', indent);
+				b.Append("R: ");
+				AppendTreeToString(node.right, b, indent);
+			}
+		}
+		#endif
+		#endregion
+		
+		#region Insert/Remove lines
+		public void RemoveLine(DocumentLine line)
+		{
+			RemoveNode(line);
+			line.isDeleted = true;
+		}
+		
+		public DocumentLine InsertLineAfter(DocumentLine line, int totalLength)
+		{
+			DocumentLine newLine = new DocumentLine(document);
+			newLine.TotalLength = totalLength;
+			
+			InsertAfter(line, newLine);
+			return newLine;
+		}
+		
+		void InsertAfter(LineNode node, DocumentLine newLine)
+		{
+			LineNode newNode = newLine.InitLineNode();
+			if (node.right == null) {
+				InsertAsRight(node, newNode);
+			} else {
+				InsertAsLeft(node.right.LeftMost, newNode);
+			}
+		}
+		#endregion
+		
+		#region Red/Black Tree
+		internal const bool RED = true;
+		internal const bool BLACK = false;
+		
+		void InsertAsLeft(LineNode parentNode, LineNode newNode)
+		{
+			Debug.Assert(parentNode.left == null);
+			parentNode.left = newNode;
+			newNode.parent = parentNode;
+			newNode.color = RED;
+			UpdateAfterChildrenChange(parentNode);
+			FixTreeOnInsert(newNode);
+		}
+		
+		void InsertAsRight(LineNode parentNode, LineNode newNode)
+		{
+			Debug.Assert(parentNode.right == null);
+			parentNode.right = newNode;
+			newNode.parent = parentNode;
+			newNode.color = RED;
+			UpdateAfterChildrenChange(parentNode);
+			FixTreeOnInsert(newNode);
+		}
+		
+		void FixTreeOnInsert(LineNode node)
+		{
+			Debug.Assert(node != null);
+			Debug.Assert(node.color == RED);
+			Debug.Assert(node.left == null || node.left.color == BLACK);
+			Debug.Assert(node.right == null || node.right.color == BLACK);
+			
+			LineNode parentNode = node.parent;
+			if (parentNode == null) {
+				// we inserted in the root -> the node must be black
+				// since this is a root node, making the node black increments the number of black nodes
+				// on all paths by one, so it is still the same for all paths.
+				node.color = BLACK;
+				return;
+			}
+			if (parentNode.color == BLACK) {
+				// if the parent node where we inserted was black, our red node is placed correctly.
+				// since we inserted a red node, the number of black nodes on each path is unchanged
+				// -> the tree is still balanced
+				return;
+			}
+			// parentNode is red, so there is a conflict here!
+			
+			// because the root is black, parentNode is not the root -> there is a grandparent node
+			LineNode grandparentNode = parentNode.parent;
+			LineNode uncleNode = Sibling(parentNode);
+			if (uncleNode != null && uncleNode.color == RED) {
+				parentNode.color = BLACK;
+				uncleNode.color = BLACK;
+				grandparentNode.color = RED;
+				FixTreeOnInsert(grandparentNode);
+				return;
+			}
+			// now we know: parent is red but uncle is black
+			// First rotation:
+			if (node == parentNode.right && parentNode == grandparentNode.left) {
+				RotateLeft(parentNode);
+				node = node.left;
+			} else if (node == parentNode.left && parentNode == grandparentNode.right) {
+				RotateRight(parentNode);
+				node = node.right;
+			}
+			// because node might have changed, reassign variables:
+			parentNode = node.parent;
+			grandparentNode = parentNode.parent;
+			
+			// Now recolor a bit:
+			parentNode.color = BLACK;
+			grandparentNode.color = RED;
+			// Second rotation:
+			if (node == parentNode.left && parentNode == grandparentNode.left) {
+				RotateRight(grandparentNode);
+			} else {
+				// because of the first rotation, this is guaranteed:
+				Debug.Assert(node == parentNode.right && parentNode == grandparentNode.right);
+				RotateLeft(grandparentNode);
+			}
+		}
+		
+		void RemoveNode(LineNode removedNode)
+		{
+			if (removedNode.left != null && removedNode.right != null) {
+				// replace removedNode with it's in-order successor
+				
+				LineNode leftMost = removedNode.right.LeftMost;
+				RemoveNode(leftMost); // remove leftMost from its current location
+				
+				// and overwrite the removedNode with it
+				ReplaceNode(removedNode, leftMost);
+				leftMost.left = removedNode.left;
+				if (leftMost.left != null) leftMost.left.parent = leftMost;
+				leftMost.right = removedNode.right;
+				if (leftMost.right != null) leftMost.right.parent = leftMost;
+				leftMost.color = removedNode.color;
+				
+				UpdateAfterChildrenChange(leftMost);
+				if (leftMost.parent != null) UpdateAfterChildrenChange(leftMost.parent);
+				return;
+			}
+			
+			// now either removedNode.left or removedNode.right is null
+			// get the remaining child
+			LineNode parentNode = removedNode.parent;
+			LineNode childNode = removedNode.left ?? removedNode.right;
+			ReplaceNode(removedNode, childNode);
+			if (parentNode != null) UpdateAfterChildrenChange(parentNode);
+			if (removedNode.color == BLACK) {
+				if (childNode != null && childNode.color == RED) {
+					childNode.color = BLACK;
+				} else {
+					FixTreeOnDelete(childNode, parentNode);
+				}
+			}
+		}
+		
+		void FixTreeOnDelete(LineNode node, LineNode parentNode)
+		{
+			Debug.Assert(node == null || node.parent == parentNode);
+			if (parentNode == null)
+				return;
+			
+			// warning: node may be null
+			LineNode sibling = Sibling(node, parentNode);
+			if (sibling.color == RED) {
+				parentNode.color = RED;
+				sibling.color = BLACK;
+				if (node == parentNode.left) {
+					RotateLeft(parentNode);
+				} else {
+					RotateRight(parentNode);
+				}
+				
+				sibling = Sibling(node, parentNode); // update value of sibling after rotation
+			}
+			
+			if (parentNode.color == BLACK
+			    && sibling.color == BLACK
+			    && GetColor(sibling.left) == BLACK
+			    && GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				FixTreeOnDelete(parentNode, parentNode.parent);
+				return;
+			}
+			
+			if (parentNode.color == RED
+			    && sibling.color == BLACK
+			    && GetColor(sibling.left) == BLACK
+			    && GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				parentNode.color = BLACK;
+				return;
+			}
+			
+			if (node == parentNode.left &&
+			    sibling.color == BLACK &&
+			    GetColor(sibling.left) == RED &&
+			    GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				sibling.left.color = BLACK;
+				RotateRight(sibling);
+			}
+			else if (node == parentNode.right &&
+			         sibling.color == BLACK &&
+			         GetColor(sibling.right) == RED &&
+			         GetColor(sibling.left) == BLACK)
+			{
+				sibling.color = RED;
+				sibling.right.color = BLACK;
+				RotateLeft(sibling);
+			}
+			sibling = Sibling(node, parentNode); // update value of sibling after rotation
+			
+			sibling.color = parentNode.color;
+			parentNode.color = BLACK;
+			if (node == parentNode.left) {
+				if (sibling.right != null) {
+					Debug.Assert(sibling.right.color == RED);
+					sibling.right.color = BLACK;
+				}
+				RotateLeft(parentNode);
+			} else {
+				if (sibling.left != null) {
+					Debug.Assert(sibling.left.color == RED);
+					sibling.left.color = BLACK;
+				}
+				RotateRight(parentNode);
+			}
+		}
+		
+		void ReplaceNode(LineNode replacedNode, LineNode newNode)
+		{
+			if (replacedNode.parent == null) {
+				Debug.Assert(replacedNode == root);
+				root = newNode;
+			} else {
+				if (replacedNode.parent.left == replacedNode)
+					replacedNode.parent.left = newNode;
+				else
+					replacedNode.parent.right = newNode;
+			}
+			if (newNode != null) {
+				newNode.parent = replacedNode.parent;
+			}
+			replacedNode.parent = null;
+		}
+		
+		void RotateLeft(LineNode p)
+		{
+			// let q be p's right child
+			LineNode q = p.right;
+			Debug.Assert(q != null);
+			Debug.Assert(q.parent == p);
+			// set q to be the new root
+			ReplaceNode(p, q);
+			
+			// set p's right child to be q's left child
+			p.right = q.left;
+			if (p.right != null) p.right.parent = p;
+			// set q's left child to be p
+			q.left = p;
+			p.parent = q;
+			UpdateAfterRotateLeft(p);
+		}
+		
+		void RotateRight(LineNode p)
+		{
+			// let q be p's left child
+			LineNode q = p.left;
+			Debug.Assert(q != null);
+			Debug.Assert(q.parent == p);
+			// set q to be the new root
+			ReplaceNode(p, q);
+			
+			// set p's left child to be q's right child
+			p.left = q.right;
+			if (p.left != null) p.left.parent = p;
+			// set q's right child to be p
+			q.right = p;
+			p.parent = q;
+			UpdateAfterRotateRight(p);
+		}
+		
+		static LineNode Sibling(LineNode node)
+		{
+			if (node == node.parent.left)
+				return node.parent.right;
+			else
+				return node.parent.left;
+		}
+		
+		static LineNode Sibling(LineNode node, LineNode parentNode)
+		{
+			Debug.Assert(node == null || node.parent == parentNode);
+			if (node == parentNode.left)
+				return parentNode.right;
+			else
+				return parentNode.left;
+		}
+		
+		static bool GetColor(LineNode node)
+		{
+			return node != null ? node.color : BLACK;
+		}
+		#endregion
+		
+		#region IList implementation
+		DocumentLine IList<DocumentLine>.this[int index] {
+			get {
+				document.VerifyAccess();
+				return GetByNumber(1 + index);
+			}
+			set {
+				throw new NotSupportedException();
+			}
+		}
+		
+		int ICollection<DocumentLine>.Count {
+			get {
+				document.VerifyAccess();
+				return LineCount;
+			}
+		}
+		
+		bool ICollection<DocumentLine>.IsReadOnly {
+			get { return true; }
+		}
+		
+		int IList<DocumentLine>.IndexOf(DocumentLine item)
+		{
+			document.VerifyAccess();
+			if (item == null || item.IsDeleted)
+				return -1;
+			int index = item.LineNumber - 1;
+			if (index < LineCount && GetNodeByIndex(index) == item)
+				return index;
+			else
+				return -1;
+		}
+		
+		void IList<DocumentLine>.Insert(int index, DocumentLine item)
+		{
+			throw new NotSupportedException();
+		}
+		
+		void IList<DocumentLine>.RemoveAt(int index)
+		{
+			throw new NotSupportedException();
+		}
+		
+		void ICollection<DocumentLine>.Add(DocumentLine item)
+		{
+			throw new NotSupportedException();
+		}
+		
+		void ICollection<DocumentLine>.Clear()
+		{
+			throw new NotSupportedException();
+		}
+		
+		bool ICollection<DocumentLine>.Contains(DocumentLine item)
+		{
+			IList<DocumentLine> self = this;
+			return self.IndexOf(item) >= 0;
+		}
+		
+		void ICollection<DocumentLine>.CopyTo(DocumentLine[] array, int arrayIndex)
+		{
+			if (array == null)
+				throw new ArgumentNullException("array");
+			if (array.Length < LineCount)
+				throw new ArgumentException("The array is too small", "array");
+			if (arrayIndex < 0 || arrayIndex + LineCount > array.Length)
+				throw new ArgumentOutOfRangeException("arrayIndex", arrayIndex, "Value must be between 0 and " + (array.Length - LineCount));
+			foreach (DocumentLine ls in this) {
+				array[arrayIndex++] = ls;
+			}
+		}
+		
+		bool ICollection<DocumentLine>.Remove(DocumentLine item)
+		{
+			throw new NotSupportedException();
+		}
+		
+		public IEnumerator<DocumentLine> GetEnumerator()
+		{
+			document.VerifyAccess();
+			return Enumerate();
+		}
+		
+		IEnumerator<DocumentLine> Enumerate()
+		{
+			document.VerifyAccess();
+			DocumentLine line = root.LeftMost;
+			while (line != null) {
+				yield return line;
+				line = line.NextLine;
+			}
+		}
+		
+		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
+		{
+			return this.GetEnumerator();
+		}
+		#endregion
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/GapTextBuffer.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/GapTextBuffer.cs
new file mode 100644
index 000000000..a617284a9
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/GapTextBuffer.cs
@@ -0,0 +1,192 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Diagnostics;
+using System.Text;
+
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/*
+	/// <summary>
+	/// Implementation of a gap text buffer.
+	/// </summary>
+	sealed class GapTextBuffer
+	{
+		char[] buffer = Empty<char>.Array;
+		
+		/// <summary>
+		/// The current text content.
+		/// Is set to null whenever the buffer changes, and gets a value only when the
+		/// full text content is requested.
+		/// </summary>
+		string textContent;
+		
+		/// <summary>
+		/// last GetText result
+		/// </summary>
+		string lastGetTextResult;
+		int lastGetTextRequestOffset;
+		
+		int gapBeginOffset;
+		int gapEndOffset;
+		int gapLength; // gapLength == gapEndOffset - gapBeginOffset
+		
+		/// <summary>
+		/// when gap is too small for inserted text or gap is too large (exceeds maxGapLength),
+		/// a new buffer is reallocated with a new gap of at least this size.
+		/// </summary>
+		const int minGapLength = 128;
+		
+		/// <summary>
+		/// when the gap exceeds this size, reallocate a smaller buffer
+		/// </summary>
+		const int maxGapLength = 4096;
+		
+		public int Length {
+			get {
+				return buffer.Length - gapLength;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the buffer content.
+		/// </summary>
+		public string Text {
+			get {
+				if (textContent == null)
+					textContent = GetText(0, Length);
+				return textContent;
+			}
+			set {
+				Debug.Assert(value != null);
+				textContent = value;  lastGetTextResult = null;
+				buffer = new char[value.Length + minGapLength];
+				value.CopyTo(0, buffer, 0, value.Length);
+				gapBeginOffset = value.Length;
+				gapEndOffset = buffer.Length;
+				gapLength = gapEndOffset - gapBeginOffset;
+			}
+		}
+		
+		public char GetCharAt(int offset)
+		{
+			return offset < gapBeginOffset ? buffer[offset] : buffer[offset + gapLength];
+		}
+		
+		public string GetText(int offset, int length)
+		{
+			if (length == 0)
+				return string.Empty;
+			if (lastGetTextRequestOffset == offset && lastGetTextResult != null && length == lastGetTextResult.Length)
+				return lastGetTextResult;
+			
+			int end = offset + length;
+			string result;
+			if (end < gapBeginOffset) {
+				result = new string(buffer, offset, length);
+			} else if (offset > gapBeginOffset) {
+				result = new string(buffer, offset + gapLength, length);
+			} else {
+				int block1Size = gapBeginOffset - offset;
+				int block2Size = end - gapBeginOffset;
+				
+				StringBuilder buf = new StringBuilder(block1Size + block2Size);
+				buf.Append(buffer, offset,       block1Size);
+				buf.Append(buffer, gapEndOffset, block2Size);
+				result = buf.ToString();
+			}
+			lastGetTextRequestOffset = offset;
+			lastGetTextResult = result;
+			return result;
+		}
+		
+		/// <summary>
+		/// Inserts text at the specified offset.
+		/// </summary>
+		public void Insert(int offset, string text)
+		{
+			Debug.Assert(offset >= 0 && offset <= Length);
+			
+			if (text.Length == 0)
+				return;
+			
+			textContent = null; lastGetTextResult = null;
+			PlaceGap(offset, text.Length);
+			text.CopyTo(0, buffer, gapBeginOffset, text.Length);
+			gapBeginOffset += text.Length;
+			gapLength = gapEndOffset - gapBeginOffset;
+		}
+		
+		/// <summary>
+		/// Remove <paramref name="length"/> characters at <paramref name="offset"/>.
+		/// Leave a gap of at least <paramref name="reserveGapSize"/>.
+		/// </summary>
+		public void Remove(int offset, int length, int reserveGapSize)
+		{
+			Debug.Assert(offset >= 0 && offset <= Length);
+			Debug.Assert(length >= 0 && offset + length <= Length);
+			Debug.Assert(reserveGapSize >= 0);
+			
+			if (length == 0)
+				return;
+			
+			textContent = null; lastGetTextResult = null;
+			PlaceGap(offset, reserveGapSize - length);
+			gapEndOffset += length; // delete removed text
+			gapLength = gapEndOffset - gapBeginOffset;
+			if (gapLength - reserveGapSize > maxGapLength && gapLength - reserveGapSize > buffer.Length / 4) {
+				// shrink gap
+				MakeNewBuffer(gapBeginOffset, reserveGapSize + minGapLength);
+			}
+		}
+		
+		void PlaceGap(int newGapOffset, int minRequiredGapLength)
+		{
+			if (gapLength < minRequiredGapLength) {
+				// enlarge gap
+				MakeNewBuffer(newGapOffset, minRequiredGapLength + Math.Max(minGapLength, buffer.Length / 8));
+			} else {
+				while (newGapOffset < gapBeginOffset) {
+					buffer[--gapEndOffset] = buffer[--gapBeginOffset];
+				}
+				while (newGapOffset > gapBeginOffset) {
+					buffer[gapBeginOffset++] = buffer[gapEndOffset++];
+				}
+			}
+		}
+		
+		void MakeNewBuffer(int newGapOffset, int newGapLength)
+		{
+			char[] newBuffer = new char[Length + newGapLength];
+			Debug.WriteLine("GapTextBuffer was reallocated, new size=" + newBuffer.Length);
+			if (newGapOffset < gapBeginOffset) {
+				// gap is moving backwards
+				
+				// first part:
+				Array.Copy(buffer, 0, newBuffer, 0, newGapOffset);
+				// moving middle part:
+				Array.Copy(buffer, newGapOffset, newBuffer, newGapOffset + newGapLength, gapBeginOffset - newGapOffset);
+				// last part:
+				Array.Copy(buffer, gapEndOffset, newBuffer, newBuffer.Length - (buffer.Length - gapEndOffset), buffer.Length - gapEndOffset);
+			} else {
+				// gap is moving forwards
+				// first part:
+				Array.Copy(buffer, 0, newBuffer, 0, gapBeginOffset);
+				// moving middle part:
+				Array.Copy(buffer, gapEndOffset, newBuffer, gapBeginOffset, newGapOffset - gapBeginOffset);
+				// last part:
+				int lastPartLength = newBuffer.Length - (newGapOffset + newGapLength);
+				Array.Copy(buffer, buffer.Length - lastPartLength, newBuffer, newGapOffset + newGapLength, lastPartLength);
+			}
+			
+			gapBeginOffset = newGapOffset;
+			gapEndOffset = newGapOffset + newGapLength;
+			gapLength = newGapLength;
+			buffer = newBuffer;
+		}
+	}
+	*/
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ILineTracker.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ILineTracker.cs
new file mode 100644
index 000000000..c16128d63
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ILineTracker.cs
@@ -0,0 +1,55 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Allows for low-level line tracking.
+	/// </summary>
+	/// <remarks>
+	/// The methods on this interface are called by the TextDocument's LineManager immediately after the document
+	/// has changed, *while* the DocumentLineTree is updating.
+	/// Thus, the DocumentLineTree may be in an invalid state when these methods are called.
+	/// This interface should only be used to update per-line data structures like the HeightTree.
+	/// Line trackers must not cause any events to be raised during an update to prevent other code from seeing
+	/// the invalid state.
+	/// Line trackers may be called while the TextDocument has taken a lock.
+	/// You must be careful not to dead-lock inside ILineTracker callbacks.
+	/// </remarks>
+	public interface ILineTracker
+	{
+		/// <summary>
+		/// Is called immediately before a document line is removed.
+		/// </summary>
+		void BeforeRemoveLine(DocumentLine line);
+		
+//		/// <summary>
+//		/// Is called immediately after a document line is removed.
+//		/// </summary>
+//		void AfterRemoveLine(DocumentLine line);
+		
+		/// <summary>
+		/// Is called immediately before a document line changes length.
+		/// This method will be called whenever the line is changed, even when the length stays as it is.
+		/// The method might be called multiple times for a single line because
+		/// a replacement is internally handled as removal followed by insertion.
+		/// </summary>
+		void SetLineLength(DocumentLine line, int newTotalLength);
+		
+		/// <summary>
+		/// Is called immediately after a line was inserted.
+		/// </summary>
+		/// <param name="newLine">The new line</param>
+		/// <param name="insertionPos">The existing line before the new line</param>
+		void LineInserted(DocumentLine insertionPos, DocumentLine newLine);
+		
+		/// <summary>
+		/// Indicates that there were changes to the document that the line tracker was not notified of.
+		/// The document is in a consistent state (but the line trackers aren't), and line trackers should
+		/// throw away their data and rebuild the document.
+		/// </summary>
+		void RebuildDocument();
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ISegment.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ISegment.cs
new file mode 100644
index 000000000..80eb63352
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ISegment.cs
@@ -0,0 +1,219 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Diagnostics;
+using Tango.Scripting.Editors.Utils;
+using System.Globalization;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// An (Offset,Length)-pair.
+	/// </summary>
+	/// <seealso cref="TextSegment"/>
+	/// <seealso cref="AnchorSegment"/>
+	public interface ISegment
+	{
+		/// <summary>
+		/// Gets the start offset of the segment.
+		/// </summary>
+		int Offset { get; }
+		
+		/// <summary>
+		/// Gets the length of the segment.
+		/// </summary>
+		/// <remarks>Must not be negative.</remarks>
+		int Length { get; }
+		
+		/// <summary>
+		/// Gets the end offset of the segment.
+		/// </summary>
+		/// <remarks>EndOffset = Offset + Length;</remarks>
+		int EndOffset { get; }
+	}
+	
+	static class SegmentExtensions
+	{
+		/// <summary>
+		/// Gets whether the segment contains the offset.
+		/// </summary>
+		/// <returns>
+		/// True, if offset is between segment.Start and segment.End (inclusive); otherwise, false.
+		/// </returns>
+		public static bool Contains(this ISegment segment, int offset)
+		{
+			int start = segment.Offset;
+			int end = start + segment.Length;
+			return offset >= start && offset <= end;
+		}
+		
+		/// <summary>
+		/// Gets the overlapping portion of the segments.
+		/// Returns SimpleSegment.Invalid if the segments don't overlap.
+		/// </summary>
+		public static SimpleSegment GetOverlap(this ISegment segment, ISegment other)
+		{
+			int start = Math.Max(segment.Offset, other.Offset);
+			int end = Math.Min(segment.EndOffset, other.EndOffset);
+			if (end < start)
+				return SimpleSegment.Invalid;
+			else
+				return new SimpleSegment(start, end - start);
+		}
+	}
+	
+	/// <summary>
+	/// Represents a simple segment (Offset,Length pair) that is not automatically updated
+	/// on document changes.
+	/// </summary>
+	struct SimpleSegment : IEquatable<SimpleSegment>, ISegment
+	{
+		public static readonly SimpleSegment Invalid = new SimpleSegment(-1, -1);
+		
+		public readonly int Offset, Length;
+		
+		int ISegment.Offset {
+			get { return Offset; }
+		}
+		
+		int ISegment.Length {
+			get { return Length; }
+		}
+		
+		public int EndOffset {
+			get {
+				return Offset + Length;
+			}
+		}
+		
+		public SimpleSegment(int offset, int length)
+		{
+			this.Offset = offset;
+			this.Length = length;
+		}
+		
+		public SimpleSegment(ISegment segment)
+		{
+			Debug.Assert(segment != null);
+			this.Offset = segment.Offset;
+			this.Length = segment.Length;
+		}
+		
+		public override int GetHashCode()
+		{
+			unchecked {
+				return Offset + 10301 * Length;
+			}
+		}
+		
+		public override bool Equals(object obj)
+		{
+			return (obj is SimpleSegment) && Equals((SimpleSegment)obj);
+		}
+		
+		public bool Equals(SimpleSegment other)
+		{
+			return this.Offset == other.Offset && this.Length == other.Length;
+		}
+		
+		public static bool operator ==(SimpleSegment left, SimpleSegment right)
+		{
+			return left.Equals(right);
+		}
+		
+		public static bool operator !=(SimpleSegment left, SimpleSegment right)
+		{
+			return !left.Equals(right);
+		}
+		
+		public override string ToString()
+		{
+			return "[Offset=" + Offset.ToString(CultureInfo.InvariantCulture) + ", Length=" + Length.ToString(CultureInfo.InvariantCulture) + "]";
+		}
+	}
+	
+	/// <summary>
+	/// A segment using <see cref="TextAnchor"/>s as start and end positions.
+	/// </summary>
+	/// <remarks>
+	/// <para>
+	/// For the constructors creating new anchors, the start position will be AfterInsertion and the end position will be BeforeInsertion.
+	/// Should the end position move before the start position, the segment will have length 0.
+	/// </para>
+	/// </remarks>
+	/// <seealso cref="ISegment"/>
+	/// <seealso cref="TextSegment"/>
+	public sealed class AnchorSegment : ISegment
+	{
+		readonly TextAnchor start, end;
+		
+		/// <inheritdoc/>
+		public int Offset {
+			get { return start.Offset; }
+		}
+		
+		/// <inheritdoc/>
+		public int Length {
+			get {
+				// Math.Max takes care of the fact that end.Offset might move before start.Offset.
+				return Math.Max(0, end.Offset - start.Offset);
+			}
+		}
+		
+		/// <inheritdoc/>
+		public int EndOffset {
+			get {
+				// Math.Max takes care of the fact that end.Offset might move before start.Offset.
+				return Math.Max(start.Offset, end.Offset);
+			}
+		}
+		
+		/// <summary>
+		/// Creates a new AnchorSegment using the specified anchors.
+		/// The anchors must have <see cref="TextAnchor.SurviveDeletion"/> set to true.
+		/// </summary>
+		public AnchorSegment(TextAnchor start, TextAnchor end)
+		{
+			if (start == null)
+				throw new ArgumentNullException("start");
+			if (end == null)
+				throw new ArgumentNullException("end");
+			if (!start.SurviveDeletion)
+				throw new ArgumentException("Anchors for AnchorSegment must use SurviveDeletion", "start");
+			if (!end.SurviveDeletion)
+				throw new ArgumentException("Anchors for AnchorSegment must use SurviveDeletion", "end");
+			this.start = start;
+			this.end = end;
+		}
+		
+		/// <summary>
+		/// Creates a new AnchorSegment that creates new anchors.
+		/// </summary>
+		public AnchorSegment(TextDocument document, ISegment segment)
+			: this(document, ThrowUtil.CheckNotNull(segment, "segment").Offset, segment.Length)
+		{
+		}
+		
+		/// <summary>
+		/// Creates a new AnchorSegment that creates new anchors.
+		/// </summary>
+		public AnchorSegment(TextDocument document, int offset, int length)
+		{
+			if (document == null)
+				throw new ArgumentNullException("document");
+			this.start = document.CreateAnchor(offset);
+			this.start.SurviveDeletion = true;
+			this.start.MovementType = AnchorMovementType.AfterInsertion;
+			this.end = document.CreateAnchor(offset + length);
+			this.end.SurviveDeletion = true;
+			this.end.MovementType = AnchorMovementType.BeforeInsertion;
+		}
+		
+		/// <inheritdoc/>
+		public override string ToString()
+		{
+			return "[Offset=" + Offset.ToString(CultureInfo.InvariantCulture) + ", EndOffset=" + EndOffset.ToString(CultureInfo.InvariantCulture) + "]";
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ITextSource.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ITextSource.cs
new file mode 100644
index 000000000..c52a333c5
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/ITextSource.cs
@@ -0,0 +1,320 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using Tango.Scripting.Editors.Utils;
+using System;
+using System.IO;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Interface for read-only access to a text source.
+	/// </summary>
+	/// <seealso cref="TextDocument"/>
+	/// <seealso cref="StringTextSource"/>
+	public interface ITextSource
+	{
+		/// <summary>
+		/// Gets the whole text as string.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1721:PropertyNamesShouldNotMatchGetMethods")]
+		string Text { get; }
+		
+		/// <summary>
+		/// Is raised when the Text property changes.
+		/// </summary>
+		event EventHandler TextChanged;
+		
+		/// <summary>
+		/// Gets the total text length.
+		/// </summary>
+		/// <returns>The length of the text, in characters.</returns>
+		/// <remarks>This is the same as Text.Length, but is more efficient because
+		///  it doesn't require creating a String object.</remarks>
+		int TextLength { get; }
+		
+		/// <summary>
+		/// Gets a character at the specified position in the document.
+		/// </summary>
+		/// <paramref name="offset">The index of the character to get.</paramref>
+		/// <exception cref="ArgumentOutOfRangeException">Offset is outside the valid range (0 to TextLength-1).</exception>
+		/// <returns>The character at the specified position.</returns>
+		/// <remarks>This is the same as Text[offset], but is more efficient because
+		/// it doesn't require creating a String object.</remarks>
+		char GetCharAt(int offset);
+		
+		/// <summary>
+		/// Gets the index of the first occurrence of any character in the specified array.
+		/// </summary>
+		/// <param name="anyOf"></param>
+		/// <param name="startIndex">Start index of the search.</param>
+		/// <param name="count">Length of the area to search.</param>
+		/// <returns>The first index where any character was found; or -1 if no occurrence was found.</returns>
+		int IndexOfAny(char[] anyOf, int startIndex, int count);
+		
+		/// <summary>
+		/// Retrieves the text for a portion of the document.
+		/// </summary>
+		/// <exception cref="ArgumentOutOfRangeException">offset or length is outside the valid range.</exception>
+		/// <remarks>This is the same as Text.Substring, but is more efficient because
+		///  it doesn't require creating a String object for the whole document.</remarks>
+		string GetText(int offset, int length);
+		
+		/// <summary>
+		/// Creates a snapshot of the current text.
+		/// </summary>
+		/// <remarks>
+		/// This method is generally not thread-safe when called on a mutable text buffer, but the resulting text buffer is immutable and thread-safe.
+		/// However, some implementing classes may provide additional thread-safety guarantees, see <see cref="TextDocument.CreateSnapshot()">TextDocument.CreateSnapshot</see>.
+		/// </remarks>
+		ITextSource CreateSnapshot();
+		
+		/// <summary>
+		/// Creates a snapshot of a part of the current text.
+		/// </summary>
+		/// <remarks>
+		/// This method is generally not thread-safe when called on a mutable text buffer, but the resulting text buffer is immutable and thread-safe.
+		/// However, some implementing classes may provide additional thread-safety guarantees, see <see cref="TextDocument.CreateSnapshot()">TextDocument.CreateSnapshot</see>.
+		/// </remarks>
+		ITextSource CreateSnapshot(int offset, int length);
+		
+		/// <summary>
+		/// Creates a text reader.
+		/// If the text is changed while a reader is active, the reader will continue to read from the old text version.
+		/// </summary>
+		TextReader CreateReader();
+	}
+	
+	/// <summary>
+	/// Implements the ITextSource interface by wrapping another TextSource
+	/// and viewing only a part of the text.
+	/// </summary>
+	[Obsolete("This class will be removed in a future version of AvalonEdit")]
+	public sealed class TextSourceView : ITextSource
+	{
+		readonly ITextSource baseTextSource;
+		readonly ISegment viewedSegment;
+		
+		/// <summary>
+		/// Creates a new TextSourceView object.
+		/// </summary>
+		/// <param name="baseTextSource">The base text source.</param>
+		/// <param name="viewedSegment">A text segment from the base text source</param>
+		public TextSourceView(ITextSource baseTextSource, ISegment viewedSegment)
+		{
+			if (baseTextSource == null)
+				throw new ArgumentNullException("baseTextSource");
+			if (viewedSegment == null)
+				throw new ArgumentNullException("viewedSegment");
+			this.baseTextSource = baseTextSource;
+			this.viewedSegment = viewedSegment;
+		}
+		
+		/// <inheritdoc/>
+		public event EventHandler TextChanged {
+			add { baseTextSource.TextChanged += value; }
+			remove { baseTextSource.TextChanged -= value; }
+		}
+		
+		/// <inheritdoc/>
+		public string Text {
+			get {
+				return baseTextSource.GetText(viewedSegment.Offset, viewedSegment.Length);
+			}
+		}
+		
+		/// <inheritdoc/>
+		public int TextLength {
+			get { return viewedSegment.Length; }
+		}
+		
+		/// <inheritdoc/>
+		public char GetCharAt(int offset)
+		{
+			return baseTextSource.GetCharAt(viewedSegment.Offset + offset);
+		}
+		
+		/// <inheritdoc/>
+		public string GetText(int offset, int length)
+		{
+			return baseTextSource.GetText(viewedSegment.Offset + offset, length);
+		}
+		
+		/// <inheritdoc/>
+		public ITextSource CreateSnapshot()
+		{
+			return baseTextSource.CreateSnapshot(viewedSegment.Offset, viewedSegment.Length);
+		}
+		
+		/// <inheritdoc/>
+		public ITextSource CreateSnapshot(int offset, int length)
+		{
+			return baseTextSource.CreateSnapshot(viewedSegment.Offset + offset, length);
+		}
+		
+		/// <inheritdoc/>
+		public TextReader CreateReader()
+		{
+			return CreateSnapshot().CreateReader();
+		}
+		
+		/// <inheritdoc/>
+		public int IndexOfAny(char[] anyOf, int startIndex, int count)
+		{
+			int offset = viewedSegment.Offset;
+			int result = baseTextSource.IndexOfAny(anyOf, startIndex + offset, count);
+			return result >= 0 ? result - offset : result;
+		}
+	}
+	
+	/// <summary>
+	/// Implements the ITextSource interface using a string.
+	/// </summary>
+	public sealed class StringTextSource : ITextSource
+	{
+		readonly string text;
+		
+		/// <summary>
+		/// Creates a new StringTextSource.
+		/// </summary>
+		public StringTextSource(string text)
+		{
+			if (text == null)
+				throw new ArgumentNullException("text");
+			this.text = text;
+		}
+		
+		// Text can never change
+		event EventHandler ITextSource.TextChanged { add {} remove {} }
+		
+		/// <inheritdoc/>
+		public string Text {
+			get { return text; }
+		}
+		
+		/// <inheritdoc/>
+		public int TextLength {
+			get { return text.Length; }
+		}
+		
+		/// <inheritdoc/>
+		public char GetCharAt(int offset)
+		{
+			// GetCharAt must throw ArgumentOutOfRangeException, not IndexOutOfRangeException
+			if (offset < 0 || offset >= text.Length)
+				throw new ArgumentOutOfRangeException("offset", offset, "offset must be between 0 and " + (text.Length - 1));
+			return text[offset];
+		}
+		
+		/// <inheritdoc/>
+		public string GetText(int offset, int length)
+		{
+			return text.Substring(offset, length);
+		}
+		
+		/// <inheritdoc/>
+		public TextReader CreateReader()
+		{
+			return new StringReader(text);
+		}
+		
+		/// <inheritdoc/>
+		public ITextSource CreateSnapshot()
+		{
+			return this; // StringTextSource already is immutable
+		}
+		
+		/// <inheritdoc/>
+		public ITextSource CreateSnapshot(int offset, int length)
+		{
+			return new StringTextSource(text.Substring(offset, length));
+		}
+		
+		/// <inheritdoc/>
+		public int IndexOfAny(char[] anyOf, int startIndex, int count)
+		{
+			return text.IndexOfAny(anyOf, startIndex, count);
+		}
+	}
+	
+	/// <summary>
+	/// Implements the ITextSource interface using a rope.
+	/// </summary>
+	public sealed class RopeTextSource : ITextSource
+	{
+		readonly Rope<char> rope;
+		
+		/// <summary>
+		/// Creates a new RopeTextSource.
+		/// </summary>
+		public RopeTextSource(Rope<char> rope)
+		{
+			if (rope == null)
+				throw new ArgumentNullException("rope");
+			this.rope = rope;
+		}
+		
+		/// <summary>
+		/// Returns a clone of the rope used for this text source.
+		/// </summary>
+		/// <remarks>
+		/// RopeTextSource only publishes a copy of the contained rope to ensure that the underlying rope cannot be modified.
+		/// Unless the creator of the RopeTextSource still has a reference on the rope, RopeTextSource is immutable.
+		/// </remarks>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate", Justification="Not a property because it creates a clone")]
+		public Rope<char> GetRope()
+		{
+			return rope.Clone();
+		}
+		
+		// Change event is not supported
+		event EventHandler ITextSource.TextChanged { add {} remove {} }
+		
+		/// <inheritdoc/>
+		public string Text {
+			get { return rope.ToString(); }
+		}
+		
+		/// <inheritdoc/>
+		public int TextLength {
+			get { return rope.Length; }
+		}
+		
+		/// <inheritdoc/>
+		public char GetCharAt(int offset)
+		{
+			return rope[offset];
+		}
+		
+		/// <inheritdoc/>
+		public string GetText(int offset, int length)
+		{
+			return rope.ToString(offset, length);
+		}
+		
+		/// <inheritdoc/>
+		public TextReader CreateReader()
+		{
+			return new RopeTextReader(rope);
+		}
+		
+		/// <inheritdoc/>
+		public ITextSource CreateSnapshot()
+		{
+			// we clone the underlying rope because the creator of the RopeTextSource might be modifying it
+			return new RopeTextSource(rope.Clone());
+		}
+		
+		/// <inheritdoc/>
+		public ITextSource CreateSnapshot(int offset, int length)
+		{
+			return new RopeTextSource(rope.GetRange(offset, length));
+		}
+		
+		/// <inheritdoc/>
+		public int IndexOfAny(char[] anyOf, int startIndex, int count)
+		{
+			return rope.IndexOfAny(anyOf, startIndex, count);
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/IUndoableOperation.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/IUndoableOperation.cs
new file mode 100644
index 000000000..2e19c462c
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/IUndoableOperation.cs
@@ -0,0 +1,30 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// This Interface describes a the basic Undo/Redo operation
+	/// all Undo Operations must implement this interface.
+	/// </summary>
+	public interface IUndoableOperation
+	{
+		/// <summary>
+		/// Undo the last operation
+		/// </summary>
+		void Undo();
+		
+		/// <summary>
+		/// Redo the last operation
+		/// </summary>
+		void Redo();
+	}
+	
+	interface IUndoableOperationWithContext : IUndoableOperation
+	{
+		void Undo(UndoStack stack);
+		void Redo(UndoStack stack);
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/LineManager.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/LineManager.cs
new file mode 100644
index 000000000..ecab1fa48
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/LineManager.cs
@@ -0,0 +1,288 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using Tango.Scripting.Editors.Utils;
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Linq;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Creates/Deletes lines when text is inserted/removed.
+	/// </summary>
+	sealed class LineManager
+	{
+		#region Constructor
+		readonly TextDocument document;
+		readonly DocumentLineTree documentLineTree;
+		
+		/// <summary>
+		/// A copy of the line trackers. We need a copy so that line trackers may remove themselves
+		/// while being notified (used e.g. by WeakLineTracker)
+		/// </summary>
+		ILineTracker[] lineTrackers;
+		
+		internal void UpdateListOfLineTrackers()
+		{
+			this.lineTrackers = document.LineTrackers.ToArray();
+		}
+		
+		public LineManager(DocumentLineTree documentLineTree, TextDocument document)
+		{
+			this.document = document;
+			this.documentLineTree = documentLineTree;
+			UpdateListOfLineTrackers();
+			
+			Rebuild();
+		}
+		#endregion
+		
+		#region Change events
+		/*
+		HashSet<DocumentLine> deletedLines = new HashSet<DocumentLine>();
+		readonly HashSet<DocumentLine> changedLines = new HashSet<DocumentLine>();
+		HashSet<DocumentLine> deletedOrChangedLines = new HashSet<DocumentLine>();
+		
+		/// <summary>
+		/// Gets the list of lines deleted since the last RetrieveChangedLines() call.
+		/// The returned list is unsorted.
+		/// </summary>
+		public ICollection<DocumentLine> RetrieveDeletedLines()
+		{
+			var r = deletedLines;
+			deletedLines = new HashSet<DocumentLine>();
+			return r;
+		}
+		
+		/// <summary>
+		/// Gets the list of lines changed since the last RetrieveChangedLines() call.
+		/// The returned list is sorted by line number and does not contain deleted lines.
+		/// </summary>
+		public List<DocumentLine> RetrieveChangedLines()
+		{
+			var list = (from line in changedLines
+			            where !line.IsDeleted
+			            let number = line.LineNumber
+			            orderby number
+			            select line).ToList();
+			changedLines.Clear();
+			return list;
+		}
+		
+		/// <summary>
+		/// Gets the list of lines changed since the last RetrieveDeletedOrChangedLines() call.
+		/// The returned list is not sorted.
+		/// </summary>
+		public ICollection<DocumentLine> RetrieveDeletedOrChangedLines()
+		{
+			var r = deletedOrChangedLines;
+			deletedOrChangedLines = new HashSet<DocumentLine>();
+			return r;
+		}
+		 */
+		#endregion
+		
+		#region Rebuild
+		public void Rebuild()
+		{
+			// keep the first document line
+			DocumentLine ls = documentLineTree.GetByNumber(1);
+			SimpleSegment ds = NewLineFinder.NextNewLine(document, 0);
+			List<DocumentLine> lines = new List<DocumentLine>();
+			int lastDelimiterEnd = 0;
+			while (ds != SimpleSegment.Invalid) {
+				ls.TotalLength = ds.Offset + ds.Length - lastDelimiterEnd;
+				ls.DelimiterLength = ds.Length;
+				lastDelimiterEnd = ds.Offset + ds.Length;
+				lines.Add(ls);
+				
+				ls = new DocumentLine(document);
+				ds = NewLineFinder.NextNewLine(document, lastDelimiterEnd);
+			}
+			ls.ResetLine();
+			ls.TotalLength = document.TextLength - lastDelimiterEnd;
+			lines.Add(ls);
+			documentLineTree.RebuildTree(lines);
+			foreach (ILineTracker lineTracker in lineTrackers)
+				lineTracker.RebuildDocument();
+		}
+		#endregion
+		
+		#region Remove
+		public void Remove(int offset, int length)
+		{
+			Debug.Assert(length >= 0);
+			if (length == 0) return;
+			DocumentLine startLine = documentLineTree.GetByOffset(offset);
+			int startLineOffset = startLine.Offset;
+			
+			Debug.Assert(offset < startLineOffset + startLine.TotalLength);
+			if (offset > startLineOffset + startLine.Length) {
+				Debug.Assert(startLine.DelimiterLength == 2);
+				// we are deleting starting in the middle of a delimiter
+				
+				// remove last delimiter part
+				SetLineLength(startLine, startLine.TotalLength - 1);
+				// remove remaining text
+				Remove(offset, length - 1);
+				return;
+			}
+			
+			if (offset + length < startLineOffset + startLine.TotalLength) {
+				// just removing a part of this line
+				//startLine.RemovedLinePart(ref deferredEventList, offset - startLineOffset, length);
+				SetLineLength(startLine, startLine.TotalLength - length);
+				return;
+			}
+			// merge startLine with another line because startLine's delimiter was deleted
+			// possibly remove lines in between if multiple delimiters were deleted
+			int charactersRemovedInStartLine = startLineOffset + startLine.TotalLength - offset;
+			Debug.Assert(charactersRemovedInStartLine > 0);
+			//startLine.RemovedLinePart(ref deferredEventList, offset - startLineOffset, charactersRemovedInStartLine);
+			
+			
+			DocumentLine endLine = documentLineTree.GetByOffset(offset + length);
+			if (endLine == startLine) {
+				// special case: we are removing a part of the last line up to the
+				// end of the document
+				SetLineLength(startLine, startLine.TotalLength - length);
+				return;
+			}
+			int endLineOffset = endLine.Offset;
+			int charactersLeftInEndLine = endLineOffset + endLine.TotalLength - (offset + length);
+			//endLine.RemovedLinePart(ref deferredEventList, 0, endLine.TotalLength - charactersLeftInEndLine);
+			//startLine.MergedWith(endLine, offset - startLineOffset);
+			
+			// remove all lines between startLine (excl.) and endLine (incl.)
+			DocumentLine tmp = startLine.NextLine;
+			DocumentLine lineToRemove;
+			do {
+				lineToRemove = tmp;
+				tmp = tmp.NextLine;
+				RemoveLine(lineToRemove);
+			} while (lineToRemove != endLine);
+			
+			SetLineLength(startLine, startLine.TotalLength - charactersRemovedInStartLine + charactersLeftInEndLine);
+		}
+
+		void RemoveLine(DocumentLine lineToRemove)
+		{
+			foreach (ILineTracker lt in lineTrackers)
+				lt.BeforeRemoveLine(lineToRemove);
+			documentLineTree.RemoveLine(lineToRemove);
+//			foreach (ILineTracker lt in lineTracker)
+//				lt.AfterRemoveLine(lineToRemove);
+//			deletedLines.Add(lineToRemove);
+//			deletedOrChangedLines.Add(lineToRemove);
+		}
+
+		#endregion
+		
+		#region Insert
+		public void Insert(int offset, string text)
+		{
+			DocumentLine line = documentLineTree.GetByOffset(offset);
+			int lineOffset = line.Offset;
+			
+			Debug.Assert(offset <= lineOffset + line.TotalLength);
+			if (offset > lineOffset + line.Length) {
+				Debug.Assert(line.DelimiterLength == 2);
+				// we are inserting in the middle of a delimiter
+				
+				// shorten line
+				SetLineLength(line, line.TotalLength - 1);
+				// add new line
+				line = InsertLineAfter(line, 1);
+				line = SetLineLength(line, 1);
+			}
+			
+			SimpleSegment ds = NewLineFinder.NextNewLine(text, 0);
+			if (ds == SimpleSegment.Invalid) {
+				// no newline is being inserted, all text is inserted in a single line
+				//line.InsertedLinePart(offset - line.Offset, text.Length);
+				SetLineLength(line, line.TotalLength + text.Length);
+				return;
+			}
+			//DocumentLine firstLine = line;
+			//firstLine.InsertedLinePart(offset - firstLine.Offset, ds.Offset);
+			int lastDelimiterEnd = 0;
+			while (ds != SimpleSegment.Invalid) {
+				// split line segment at line delimiter
+				int lineBreakOffset = offset + ds.Offset + ds.Length;
+				lineOffset = line.Offset;
+				int lengthAfterInsertionPos = lineOffset + line.TotalLength - (offset + lastDelimiterEnd);
+				line = SetLineLength(line, lineBreakOffset - lineOffset);
+				DocumentLine newLine = InsertLineAfter(line, lengthAfterInsertionPos);
+				newLine = SetLineLength(newLine, lengthAfterInsertionPos);
+				
+				line = newLine;
+				lastDelimiterEnd = ds.Offset + ds.Length;
+				
+				ds = NewLineFinder.NextNewLine(text, lastDelimiterEnd);
+			}
+			//firstLine.SplitTo(line);
+			// insert rest after last delimiter
+			if (lastDelimiterEnd != text.Length) {
+				//line.InsertedLinePart(0, text.Length - lastDelimiterEnd);
+				SetLineLength(line, line.TotalLength + text.Length - lastDelimiterEnd);
+			}
+		}
+		
+		DocumentLine InsertLineAfter(DocumentLine line, int length)
+		{
+			DocumentLine newLine = documentLineTree.InsertLineAfter(line, length);
+			foreach (ILineTracker lt in lineTrackers)
+				lt.LineInserted(line, newLine);
+			return newLine;
+		}
+		#endregion
+		
+		#region SetLineLength
+		/// <summary>
+		/// Sets the total line length and checks the delimiter.
+		/// This method can cause line to be deleted when it contains a single '\n' character
+		/// and the previous line ends with '\r'.
+		/// </summary>
+		/// <returns>Usually returns <paramref name="line"/>, but if line was deleted due to
+		/// the "\r\n" merge, returns the previous line.</returns>
+		DocumentLine SetLineLength(DocumentLine line, int newTotalLength)
+		{
+//			changedLines.Add(line);
+//			deletedOrChangedLines.Add(line);
+			int delta = newTotalLength - line.TotalLength;
+			if (delta != 0) {
+				foreach (ILineTracker lt in lineTrackers)
+					lt.SetLineLength(line, newTotalLength);
+				line.TotalLength = newTotalLength;
+				DocumentLineTree.UpdateAfterChildrenChange(line);
+			}
+			// determine new DelimiterLength
+			if (newTotalLength == 0) {
+				line.DelimiterLength = 0;
+			} else {
+				int lineOffset = line.Offset;
+				char lastChar = document.GetCharAt(lineOffset + newTotalLength - 1);
+				if (lastChar == '\r') {
+					line.DelimiterLength = 1;
+				} else if (lastChar == '\n') {
+					if (newTotalLength >= 2 && document.GetCharAt(lineOffset + newTotalLength - 2) == '\r') {
+						line.DelimiterLength = 2;
+					} else if (newTotalLength == 1 && lineOffset > 0 && document.GetCharAt(lineOffset - 1) == '\r') {
+						// we need to join this line with the previous line
+						DocumentLine previousLine = line.PreviousLine;
+						RemoveLine(line);
+						return SetLineLength(previousLine, previousLine.TotalLength + 1);
+					} else {
+						line.DelimiterLength = 1;
+					}
+				} else {
+					line.DelimiterLength = 0;
+				}
+			}
+			return line;
+		}
+		#endregion
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/LineNode.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/LineNode.cs
new file mode 100644
index 000000000..317202721
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/LineNode.cs
@@ -0,0 +1,83 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+
+namespace Tango.Scripting.Editors.Document
+{
+	using LineNode = DocumentLine;
+	
+	// A tree node in the document line tree.
+	// For the purpose of the invariants, "children", "descendents", "siblings" etc. include the DocumentLine object,
+	// it is treated as a third child node between left and right.
+	
+	// Originally, this was a separate class, with a reference to the documentLine. The documentLine had a reference
+	// back to the node. To save memory, the same object is used for both the documentLine and the line node.
+	// This saves 16 bytes per line (8 byte object overhead + two pointers).
+//	sealed class LineNode
+//	{
+//		internal readonly DocumentLine documentLine;
+	partial class DocumentLine
+	{
+		internal DocumentLine left, right, parent;
+		internal bool color;
+		// optimization note: I tried packing color and isDeleted into a single byte field, but that
+		// actually increased the memory requirements. The JIT packs two bools and a byte (delimiterSize)
+		// into a single DWORD, but two bytes get each their own DWORD. Three bytes end up in the same DWORD, so
+		// apparently the JIT only optimizes for memory when there are at least three small fields.
+		// Currently, DocumentLine takes 36 bytes on x86 (8 byte object overhead, 3 pointers, 3 ints, and another DWORD
+		// for the small fields).
+		// TODO: a possible optimization would be to combine 'totalLength' and the small fields into a single uint.
+		// delimiterSize takes only two bits, the two bools take another two bits; so there's still 
+		// 28 bits left for totalLength. 268435455 characters per line should be enough for everyone :)
+		
+		/// <summary>
+		/// Resets the line to enable its reuse after a document rebuild.
+		/// </summary>
+		internal void ResetLine()
+		{
+			totalLength = delimiterLength = 0;
+			isDeleted = color = false;
+			left = right = parent = null;
+		}
+		
+		internal LineNode InitLineNode()
+		{
+			this.nodeTotalCount = 1;
+			this.nodeTotalLength = this.TotalLength;
+			return this;
+		}
+		
+		internal LineNode LeftMost {
+			get {
+				LineNode node = this;
+				while (node.left != null)
+					node = node.left;
+				return node;
+			}
+		}
+		
+		internal LineNode RightMost {
+			get {
+				LineNode node = this;
+				while (node.right != null)
+					node = node.right;
+				return node;
+			}
+		}
+		
+		/// <summary>
+		/// The number of lines in this node and its child nodes.
+		/// Invariant:
+		///   nodeTotalCount = 1 + left.nodeTotalCount + right.nodeTotalCount
+		/// </summary>
+		internal int nodeTotalCount;
+		
+		/// <summary>
+		/// The total text length of this node and its child nodes.
+		/// Invariant:
+		///   nodeTotalLength = left.nodeTotalLength + documentLine.TotalLength + right.nodeTotalLength
+		/// </summary>
+		internal int nodeTotalLength;
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/NewLineFinder.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/NewLineFinder.cs
new file mode 100644
index 000000000..6ecf8c1e5
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/NewLineFinder.cs
@@ -0,0 +1,134 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+
+namespace Tango.Scripting.Editors.Document
+{
+	static class NewLineFinder
+	{
+		static readonly char[] newline = { '\r', '\n' };
+		
+		internal static readonly string[] NewlineStrings = { "\r\n", "\r", "\n" };
+		
+		/// <summary>
+		/// Gets the location of the next new line character, or SimpleSegment.Invalid
+		/// if none is found.
+		/// </summary>
+		internal static SimpleSegment NextNewLine(string text, int offset)
+		{
+			int pos = text.IndexOfAny(newline, offset);
+			if (pos >= 0) {
+				if (text[pos] == '\r') {
+					if (pos + 1 < text.Length && text[pos + 1] == '\n')
+						return new SimpleSegment(pos, 2);
+				}
+				return new SimpleSegment(pos, 1);
+			}
+			return SimpleSegment.Invalid;
+		}
+		
+		/// <summary>
+		/// Gets the location of the next new line character, or SimpleSegment.Invalid
+		/// if none is found.
+		/// </summary>
+		internal static SimpleSegment NextNewLine(ITextSource text, int offset)
+		{
+			int textLength = text.TextLength;
+			int pos = text.IndexOfAny(newline, offset, textLength - offset);
+			if (pos >= 0) {
+				if (text.GetCharAt(pos) == '\r') {
+					if (pos + 1 < textLength && text.GetCharAt(pos + 1) == '\n')
+						return new SimpleSegment(pos, 2);
+				}
+				return new SimpleSegment(pos, 1);
+			}
+			return SimpleSegment.Invalid;
+		}
+	}
+	
+	partial class TextUtilities
+	{
+		/// <summary>
+		/// Finds the next new line character starting at offset.
+		/// </summary>
+		/// <param name="text">The text source to search in.</param>
+		/// <param name="offset">The starting offset for the search.</param>
+		/// <param name="newLineType">The string representing the new line that was found, or null if no new line was found.</param>
+		/// <returns>The position of the first new line starting at or after <paramref name="offset"/>,
+		/// or -1 if no new line was found.</returns>
+		public static int FindNextNewLine(ITextSource text, int offset, out string newLineType)
+		{
+			if (text == null)
+				throw new ArgumentNullException("text");
+			if (offset < 0 || offset > text.TextLength)
+				throw new ArgumentOutOfRangeException("offset", offset, "offset is outside of text source");
+			SimpleSegment s = NewLineFinder.NextNewLine(text, offset);
+			if (s == SimpleSegment.Invalid) {
+				newLineType = null;
+				return -1;
+			} else {
+				if (s.Length == 2) {
+					newLineType = "\r\n";
+				} else if (text.GetCharAt(s.Offset) == '\n') {
+					newLineType = "\n";
+				} else {
+					newLineType = "\r";
+				}
+				return s.Offset;
+			}
+		}
+		
+		/// <summary>
+		/// Gets whether the specified string is a newline sequence.
+		/// </summary>
+		public static bool IsNewLine(string newLine)
+		{
+			return newLine == "\r\n" || newLine == "\n" || newLine == "\r";
+		}
+		
+		/// <summary>
+		/// Normalizes all new lines in <paramref name="input"/> to be <paramref name="newLine"/>.
+		/// </summary>
+		public static string NormalizeNewLines(string input, string newLine)
+		{
+			if (input == null)
+				return null;
+			if (!IsNewLine(newLine))
+				throw new ArgumentException("newLine must be one of the known newline sequences");
+			SimpleSegment ds = NewLineFinder.NextNewLine(input, 0);
+			if (ds == SimpleSegment.Invalid) // text does not contain any new lines
+				return input;
+			StringBuilder b = new StringBuilder(input.Length);
+			int lastEndOffset = 0;
+			do {
+				b.Append(input, lastEndOffset, ds.Offset - lastEndOffset);
+				b.Append(newLine);
+				lastEndOffset = ds.EndOffset;
+				ds = NewLineFinder.NextNewLine(input, lastEndOffset);
+			} while (ds != SimpleSegment.Invalid);
+			// remaining string (after last newline)
+			b.Append(input, lastEndOffset, input.Length - lastEndOffset);
+			return b.ToString();
+		}
+		
+		/// <summary>
+		/// Gets the newline sequence used in the document at the specified line.
+		/// </summary>
+		public static string GetNewLineFromDocument(TextDocument document, int lineNumber)
+		{
+			DocumentLine line = document.GetLineByNumber(lineNumber);
+			if (line.DelimiterLength == 0) {
+				// at the end of the document, there's no line delimiter, so use the delimiter
+				// from the previous line
+				line = line.PreviousLine;
+				if (line == null)
+					return Environment.NewLine;
+			}
+			return document.GetText(line.Offset + line.Length, line.DelimiterLength);
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/OffsetChangeMap.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/OffsetChangeMap.cs
new file mode 100644
index 000000000..9494af56b
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/OffsetChangeMap.cs
@@ -0,0 +1,347 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics.CodeAnalysis;
+
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Contains predefined offset change mapping types.
+	/// </summary>
+	public enum OffsetChangeMappingType
+	{
+		/// <summary>
+		/// Normal replace.
+		/// Anchors in front of the replaced region will stay in front, anchors after the replaced region will stay after.
+		/// Anchors in the middle of the removed region will be deleted. If they survive deletion,
+		/// they move depending on their AnchorMovementType.
+		/// </summary>
+		/// <remarks>
+		/// This is the default implementation of DocumentChangeEventArgs when OffsetChangeMap is null,
+		/// so using this option usually works without creating an OffsetChangeMap instance.
+		/// This is equivalent to an OffsetChangeMap with a single entry describing the replace operation.
+		/// </remarks>
+		Normal,
+		/// <summary>
+		/// First the old text is removed, then the new text is inserted.
+		/// Anchors immediately in front (or after) the replaced region may move to the other side of the insertion,
+		/// depending on the AnchorMovementType.
+		/// </summary>
+		/// <remarks>
+		/// This is implemented as an OffsetChangeMap with two entries: the removal, and the insertion.
+		/// </remarks>
+		RemoveAndInsert,
+		/// <summary>
+		/// The text is replaced character-by-character.
+		/// Anchors keep their position inside the replaced text.
+		/// Anchors after the replaced region will move accordingly if the replacement text has a different length than the replaced text.
+		/// If the new text is shorter than the old text, anchors inside the old text that would end up behind the replacement text
+		/// will be moved so that they point to the end of the replacement text.
+		/// </summary>
+		/// <remarks>
+		/// On the OffsetChangeMap level, growing text is implemented by replacing the last character in the replaced text
+		/// with itself and the additional text segment. A simple insertion of the additional text would have the undesired
+		/// effect of moving anchors immediately after the replaced text into the replacement text if they used
+		/// AnchorMovementStyle.BeforeInsertion.
+		/// Shrinking text is implemented by removing the text segment that's too long; but in a special mode that
+		/// causes anchors to always survive irrespective of their <see cref="TextAnchor.SurviveDeletion"/> setting.
+		/// If the text keeps its old size, this is implemented as OffsetChangeMap.Empty.
+		/// </remarks>
+		CharacterReplace,
+		/// <summary>
+		/// Like 'Normal', but anchors with <see cref="TextAnchor.MovementType"/> = Default will stay in front of the
+		/// insertion instead of being moved behind it.
+		/// </summary>
+		KeepAnchorBeforeInsertion
+	}
+	
+	/// <summary>
+	/// Describes a series of offset changes.
+	/// </summary>
+	[Serializable]
+	[SuppressMessage("Microsoft.Naming", "CA1710:IdentifiersShouldHaveCorrectSuffix",
+	                 Justification="It's a mapping old offsets -> new offsets")]
+	public sealed class OffsetChangeMap : Collection<OffsetChangeMapEntry>
+	{
+		/// <summary>
+		/// Immutable OffsetChangeMap that is empty.
+		/// </summary>
+		[SuppressMessage("Microsoft.Security", "CA2104:DoNotDeclareReadOnlyMutableReferenceTypes",
+		                 Justification="The Empty instance is immutable")]
+		public static readonly OffsetChangeMap Empty = new OffsetChangeMap(Empty<OffsetChangeMapEntry>.Array, true);
+		
+		/// <summary>
+		/// Creates a new OffsetChangeMap with a single element.
+		/// </summary>
+		/// <param name="entry">The entry.</param>
+		/// <returns>Returns a frozen OffsetChangeMap with a single entry.</returns>
+		public static OffsetChangeMap FromSingleElement(OffsetChangeMapEntry entry)
+		{
+			return new OffsetChangeMap(new OffsetChangeMapEntry[] { entry }, true);
+		}
+		
+		bool isFrozen;
+		
+		/// <summary>
+		/// Creates a new OffsetChangeMap instance.
+		/// </summary>
+		public OffsetChangeMap()
+		{
+		}
+		
+		internal OffsetChangeMap(int capacity)
+			: base(new List<OffsetChangeMapEntry>(capacity))
+		{
+		}
+		
+		private OffsetChangeMap(IList<OffsetChangeMapEntry> entries, bool isFrozen)
+			: base(entries)
+		{
+			this.isFrozen = isFrozen;
+		}
+		
+		/// <summary>
+		/// Gets the new offset where the specified offset moves after this document change.
+		/// </summary>
+		public int GetNewOffset(int offset, AnchorMovementType movementType)
+		{
+			IList<OffsetChangeMapEntry> items = this.Items;
+			int count = items.Count;
+			for (int i = 0; i < count; i++) {
+				offset = items[i].GetNewOffset(offset, movementType);
+			}
+			return offset;
+		}
+		
+		/// <summary>
+		/// Gets whether this OffsetChangeMap is a valid explanation for the specified document change.
+		/// </summary>
+		public bool IsValidForDocumentChange(int offset, int removalLength, int insertionLength)
+		{
+			int endOffset = offset + removalLength;
+			foreach (OffsetChangeMapEntry entry in this) {
+				// check that ChangeMapEntry is in valid range for this document change
+				if (entry.Offset < offset || entry.Offset + entry.RemovalLength > endOffset)
+					return false;
+				endOffset += entry.InsertionLength - entry.RemovalLength;
+			}
+			// check that the total delta matches
+			return endOffset == offset + insertionLength;
+		}
+		
+		/// <summary>
+		/// Calculates the inverted OffsetChangeMap (used for the undo operation).
+		/// </summary>
+		public OffsetChangeMap Invert()
+		{
+			if (this == Empty)
+				return this;
+			OffsetChangeMap newMap = new OffsetChangeMap(this.Count);
+			for (int i = this.Count - 1; i >= 0; i--) {
+				OffsetChangeMapEntry entry = this[i];
+				// swap InsertionLength and RemovalLength
+				newMap.Add(new OffsetChangeMapEntry(entry.Offset, entry.InsertionLength, entry.RemovalLength));
+			}
+			return newMap;
+		}
+		
+		/// <inheritdoc/>
+		protected override void ClearItems()
+		{
+			CheckFrozen();
+			base.ClearItems();
+		}
+		
+		/// <inheritdoc/>
+		protected override void InsertItem(int index, OffsetChangeMapEntry item)
+		{
+			CheckFrozen();
+			base.InsertItem(index, item);
+		}
+		
+		/// <inheritdoc/>
+		protected override void RemoveItem(int index)
+		{
+			CheckFrozen();
+			base.RemoveItem(index);
+		}
+		
+		/// <inheritdoc/>
+		protected override void SetItem(int index, OffsetChangeMapEntry item)
+		{
+			CheckFrozen();
+			base.SetItem(index, item);
+		}
+		
+		void CheckFrozen()
+		{
+			if (isFrozen)
+				throw new InvalidOperationException("This instance is frozen and cannot be modified.");
+		}
+		
+		/// <summary>
+		/// Gets if this instance is frozen. Frozen instances are immutable and thus thread-safe.
+		/// </summary>
+		public bool IsFrozen {
+			get { return isFrozen; }
+		}
+		
+		/// <summary>
+		/// Freezes this instance.
+		/// </summary>
+		public void Freeze()
+		{
+			isFrozen = true;
+		}
+	}
+	
+	/// <summary>
+	/// An entry in the OffsetChangeMap.
+	/// This represents the offset of a document change (either insertion or removal, not both at once).
+	/// </summary>
+	[Serializable]
+	public struct OffsetChangeMapEntry : IEquatable<OffsetChangeMapEntry>
+	{
+		readonly int offset;
+		
+		// MSB: DefaultAnchorMovementIsBeforeInsertion
+		readonly uint insertionLengthWithMovementFlag;
+		
+		// MSB: RemovalNeverCausesAnchorDeletion; other 31 bits: RemovalLength
+		readonly uint removalLengthWithDeletionFlag;
+		
+		/// <summary>
+		/// The offset at which the change occurs.
+		/// </summary>
+		public int Offset {
+			get { return offset; }
+		}
+		
+		/// <summary>
+		/// The number of characters inserted.
+		/// Returns 0 if this entry represents a removal.
+		/// </summary>
+		public int InsertionLength {
+			get { return (int)(insertionLengthWithMovementFlag & 0x7fffffff); }
+		}
+		
+		/// <summary>
+		/// The number of characters removed.
+		/// Returns 0 if this entry represents an insertion.
+		/// </summary>
+		public int RemovalLength {
+			get { return (int)(removalLengthWithDeletionFlag & 0x7fffffff); }
+		}
+		
+		/// <summary>
+		/// Gets whether the removal should not cause any anchor deletions.
+		/// </summary>
+		public bool RemovalNeverCausesAnchorDeletion {
+			get { return (removalLengthWithDeletionFlag & 0x80000000) != 0; }
+		}
+		
+		/// <summary>
+		/// Gets whether default anchor movement causes the anchor to stay in front of the caret.
+		/// </summary>
+		public bool DefaultAnchorMovementIsBeforeInsertion {
+			get { return (insertionLengthWithMovementFlag & 0x80000000) != 0; }
+		}
+		
+		/// <summary>
+		/// Gets the new offset where the specified offset moves after this document change.
+		/// </summary>
+		public int GetNewOffset(int oldOffset, AnchorMovementType movementType)
+		{
+			int insertionLength = this.InsertionLength;
+			int removalLength = this.RemovalLength;
+			if (!(removalLength == 0 && oldOffset == offset)) {
+				// we're getting trouble (both if statements in here would apply)
+				// if there's no removal and we insert at the offset
+				// -> we'd need to disambiguate by movementType, which is handled after the if
+				
+				// offset is before start of change: no movement
+				if (oldOffset <= offset)
+					return oldOffset;
+				// offset is after end of change: movement by normal delta
+				if (oldOffset >= offset + removalLength)
+					return oldOffset + insertionLength - removalLength;
+			}
+			// we reach this point if
+			// a) the oldOffset is inside the deleted segment
+			// b) there was no removal and we insert at the caret position
+			if (movementType == AnchorMovementType.AfterInsertion)
+				return offset + insertionLength;
+			else if (movementType == AnchorMovementType.BeforeInsertion)
+				return offset;
+			else
+				return this.DefaultAnchorMovementIsBeforeInsertion ? offset : offset + insertionLength;
+		}
+		
+		/// <summary>
+		/// Creates a new OffsetChangeMapEntry instance.
+		/// </summary>
+		public OffsetChangeMapEntry(int offset, int removalLength, int insertionLength)
+		{
+			ThrowUtil.CheckNotNegative(offset, "offset");
+			ThrowUtil.CheckNotNegative(removalLength, "removalLength");
+			ThrowUtil.CheckNotNegative(insertionLength, "insertionLength");
+			
+			this.offset = offset;
+			this.removalLengthWithDeletionFlag = (uint)removalLength;
+			this.insertionLengthWithMovementFlag = (uint)insertionLength;
+		}
+		
+		/// <summary>
+		/// Creates a new OffsetChangeMapEntry instance.
+		/// </summary>
+		public OffsetChangeMapEntry(int offset, int removalLength, int insertionLength, bool removalNeverCausesAnchorDeletion, bool defaultAnchorMovementIsBeforeInsertion)
+			: this(offset, removalLength, insertionLength)
+		{
+			if (removalNeverCausesAnchorDeletion)
+				this.removalLengthWithDeletionFlag |= 0x80000000;
+			if (defaultAnchorMovementIsBeforeInsertion)
+				this.insertionLengthWithMovementFlag |= 0x80000000;
+		}
+		
+		/// <inheritdoc/>
+		public override int GetHashCode()
+		{
+			unchecked {
+				return offset + 3559 * (int)insertionLengthWithMovementFlag + 3571 * (int)removalLengthWithDeletionFlag;
+			}
+		}
+		
+		/// <inheritdoc/>
+		public override bool Equals(object obj)
+		{
+			return obj is OffsetChangeMapEntry && this.Equals((OffsetChangeMapEntry)obj);
+		}
+		
+		/// <inheritdoc/>
+		public bool Equals(OffsetChangeMapEntry other)
+		{
+			return offset == other.offset && insertionLengthWithMovementFlag == other.insertionLengthWithMovementFlag && removalLengthWithDeletionFlag == other.removalLengthWithDeletionFlag;
+		}
+		
+		/// <summary>
+		/// Tests the two entries for equality.
+		/// </summary>
+		public static bool operator ==(OffsetChangeMapEntry left, OffsetChangeMapEntry right)
+		{
+			return left.Equals(right);
+		}
+		
+		/// <summary>
+		/// Tests the two entries for inequality.
+		/// </summary>
+		public static bool operator !=(OffsetChangeMapEntry left, OffsetChangeMapEntry right)
+		{
+			return !left.Equals(right);
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchor.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchor.cs
new file mode 100644
index 000000000..a65c276f9
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchor.cs
@@ -0,0 +1,194 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// The TextAnchor class references an offset (a position between two characters).
+	/// It automatically updates the offset when text is inserted/removed in front of the anchor.
+	/// </summary>
+	/// <remarks>
+	/// <para>Use the <see cref="Offset"/> property to get the offset from a text anchor.
+	/// Use the <see cref="TextDocument.CreateAnchor"/> method to create an anchor from an offset.
+	/// </para>
+	/// <para>
+	/// The document will automatically update all text anchors; and because it uses weak references to do so,
+	/// the garbage collector can simply collect the anchor object when you don't need it anymore.
+	/// </para>
+	/// <para>Moreover, the document is able to efficiently update a large number of anchors without having to look
+	/// at each anchor object individually. Updating the offsets of all anchors usually only takes time logarithmic
+	/// to the number of anchors. Retrieving the <see cref="Offset"/> property also runs in O(lg N).</para>
+	/// <inheritdoc cref="IsDeleted" />
+	/// <inheritdoc cref="MovementType" />
+	/// <para>If you want to track a segment, you can use the <see cref="AnchorSegment"/> class which
+	/// implements <see cref="ISegment"/> using two text anchors.</para>
+	/// </remarks>
+	/// <example>
+	/// Usage:
+	/// <code>TextAnchor anchor = document.CreateAnchor(offset);
+	/// ChangeMyDocument();
+	/// int newOffset = anchor.Offset;
+	/// </code>
+	/// </example>
+	public sealed class TextAnchor
+	{
+		readonly TextDocument document;
+		internal TextAnchorNode node;
+		
+		internal TextAnchor(TextDocument document)
+		{
+			this.document = document;
+		}
+		
+		/// <summary>
+		/// Gets the document owning the anchor.
+		/// </summary>
+		public TextDocument Document {
+			get { return document; }
+		}
+		
+		/// <summary>
+		/// Controls how the anchor moves.
+		/// </summary>
+		/// <remarks>Anchor movement is ambiguous if text is inserted exactly at the anchor's location.
+		/// Does the anchor stay before the inserted text, or does it move after it?
+		/// The property <see cref="MovementType"/> will be used to determine which of these two options the anchor will choose.
+		/// The default value is <see cref="AnchorMovementType.Default"/>.</remarks>
+		public AnchorMovementType MovementType { get; set; }
+		
+		/// <summary>
+		/// <para>
+		/// Specifies whether the anchor survives deletion of the text containing it.
+		/// </para><para>
+		/// <c>false</c>: The anchor is deleted when the a selection that includes the anchor is deleted.
+		/// <c>true</c>: The anchor is not deleted.
+		/// </para>
+		/// </summary>
+		/// <remarks><inheritdoc cref="IsDeleted" /></remarks>
+		public bool SurviveDeletion { get; set; }
+		
+		/// <summary>
+		/// Gets whether the anchor was deleted.
+		/// </summary>
+		/// <remarks>
+		/// <para>When a piece of text containing an anchor is removed, then that anchor will be deleted.
+		/// First, the <see cref="IsDeleted"/> property is set to true on all deleted anchors,
+		/// then the <see cref="Deleted"/> events are raised.
+		/// You cannot retrieve the offset from an anchor that has been deleted.</para>
+		/// <para>This deletion behavior might be useful when using anchors for building a bookmark feature,
+		/// but in other cases you want to still be able to use the anchor. For those cases, set <c><see cref="SurviveDeletion"/> = true</c>.</para>
+		/// </remarks>
+		public bool IsDeleted {
+			get {
+				document.DebugVerifyAccess();
+				return node == null;
+			}
+		}
+		
+		/// <summary>
+		/// Occurs after the anchor was deleted.
+		/// </summary>
+		/// <remarks>
+		/// <inheritdoc cref="IsDeleted" />
+		/// <para>Due to the 'weak reference' nature of TextAnchor, you will receive the Deleted event only
+		/// while your code holds a reference to the TextAnchor object.</para>
+		/// </remarks>
+		public event EventHandler Deleted;
+		
+		internal void OnDeleted(DelayedEvents delayedEvents)
+		{
+			node = null;
+			delayedEvents.DelayedRaise(Deleted, this, EventArgs.Empty);
+		}
+		
+		/// <summary>
+		/// Gets the offset of the text anchor.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
+		public int Offset {
+			get {
+				document.DebugVerifyAccess();
+				
+				TextAnchorNode n = this.node;
+				if (n == null)
+					throw new InvalidOperationException();
+				
+				int offset = n.length;
+				if (n.left != null)
+					offset += n.left.totalLength;
+				while (n.parent != null) {
+					if (n == n.parent.right) {
+						if (n.parent.left != null)
+							offset += n.parent.left.totalLength;
+						offset += n.parent.length;
+					}
+					n = n.parent;
+				}
+				return offset;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the line number of the anchor.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
+		public int Line {
+			get {
+				return document.GetLineByOffset(this.Offset).LineNumber;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the column number of this anchor.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
+		public int Column {
+			get {
+				int offset = this.Offset;
+				return offset - document.GetLineByOffset(offset).Offset + 1;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the text location of this anchor.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
+		public TextLocation Location {
+			get {
+				return document.GetLocation(this.Offset);
+			}
+		}
+		
+		/// <inheritdoc/>
+		public override string ToString()
+		{
+			return "[TextAnchor Offset=" + Offset + "]";
+		}
+	}
+	
+	/// <summary>
+	/// Defines how a text anchor moves.
+	/// </summary>
+	public enum AnchorMovementType
+	{
+		/// <summary>
+		/// When text is inserted at the anchor position, the type of the insertion
+		/// determines where the caret moves to. For normal insertions, the anchor will stay
+		/// behind the inserted text.
+		/// </summary>
+		Default,
+		/// <summary>
+		/// When text is inserted at the anchor position, the anchor will stay
+		/// before the inserted text.
+		/// </summary>
+		BeforeInsertion,
+		/// <summary>
+		/// When text is insered at the anchor position, the anchor will move
+		/// after the inserted text.
+		/// </summary>
+		AfterInsertion
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchorNode.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchorNode.cs
new file mode 100644
index 000000000..bfa7c4eef
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchorNode.cs
@@ -0,0 +1,87 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// A TextAnchorNode is placed in the TextAnchorTree.
+	/// It describes a section of text with a text anchor at the end of the section.
+	/// A weak reference is used to refer to the TextAnchor. (to save memory, we derive from WeakReference instead of referencing it)
+	/// </summary>
+	sealed class TextAnchorNode : WeakReference
+	{
+		internal TextAnchorNode left, right, parent;
+		internal bool color;
+		internal int length;
+		internal int totalLength; // totalLength = length + left.totalLength + right.totalLength
+		
+		public TextAnchorNode(TextAnchor anchor) : base(anchor)
+		{
+		}
+		
+		internal TextAnchorNode LeftMost {
+			get {
+				TextAnchorNode node = this;
+				while (node.left != null)
+					node = node.left;
+				return node;
+			}
+		}
+		
+		internal TextAnchorNode RightMost {
+			get {
+				TextAnchorNode node = this;
+				while (node.right != null)
+					node = node.right;
+				return node;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the inorder successor of the node.
+		/// </summary>
+		internal TextAnchorNode Successor {
+			get {
+				if (right != null) {
+					return right.LeftMost;
+				} else {
+					TextAnchorNode node = this;
+					TextAnchorNode oldNode;
+					do {
+						oldNode = node;
+						node = node.parent;
+						// go up until we are coming out of a left subtree
+					} while (node != null && node.right == oldNode);
+					return node;
+				}
+			}
+		}
+		
+		/// <summary>
+		/// Gets the inorder predecessor of the node.
+		/// </summary>
+		internal TextAnchorNode Predecessor {
+			get {
+				if (left != null) {
+					return left.RightMost;
+				} else {
+					TextAnchorNode node = this;
+					TextAnchorNode oldNode;
+					do {
+						oldNode = node;
+						node = node.parent;
+						// go up until we are coming out of a right subtree
+					} while (node != null && node.left == oldNode);
+					return node;
+				}
+			}
+		}
+		
+		public override string ToString()
+		{
+			return "[TextAnchorNode Length=" + length + " TotalLength=" + totalLength + " Target=" + Target + "]";
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchorTree.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchorTree.cs
new file mode 100644
index 000000000..d07a33b9d
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextAnchorTree.cs
@@ -0,0 +1,753 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Text;
+
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// A tree of TextAnchorNodes.
+	/// </summary>
+	sealed class TextAnchorTree
+	{
+		// The text anchor tree has difficult requirements:
+		// - it must QUICKLY update the offset in all anchors whenever there is a document change
+		// - it must not reference text anchors directly, using weak references instead
+		
+		// Clearly, we cannot afford updating an Offset property on all anchors (that would be O(N)).
+		// So instead, the anchors need to be able to calculate their offset from a data structure
+		// that can be efficiently updated.
+		
+		// This implementation is built using an augmented red-black-tree.
+		// There is a 'TextAnchorNode' for each text anchor.
+		// Such a node represents a section of text (just the length is stored) with a (weakly referenced) text anchor at the end.
+		
+		// Basically, you can imagine the list of text anchors as a sorted list of text anchors, where each anchor
+		// just stores the distance to the previous anchor.
+		// (next node = TextAnchorNode.Successor, distance = TextAnchorNode.length)
+		// Distances are never negative, so this representation means anchors are always sorted by offset
+		// (the order of anchors at the same offset is undefined)
+		
+		// Of course, a linked list of anchors would be way too slow (one would need to traverse the whole list
+		// every time the offset of an anchor is being looked up).
+		// Instead, we use a red-black-tree. We aren't actually using the tree for sorting - it's just a binary tree
+		// as storage format for what's conceptually a list, the red-black properties are used to keep the tree balanced.
+		// Other balanced binary trees would work, too.
+		
+		// What makes the tree-form efficient is that is augments the data by a 'totalLength'. Where 'length'
+		// represents the distance to the previous node, 'totalLength' is the sum of all 'length' values in the subtree
+		// under that node.
+		// This allows computing the Offset from an anchor by walking up the list of parent nodes instead of going
+		// through all predecessor nodes. So computing the Offset runs in O(log N).
+		
+		readonly TextDocument document;
+		readonly List<TextAnchorNode> nodesToDelete = new List<TextAnchorNode>();
+		TextAnchorNode root;
+		
+		public TextAnchorTree(TextDocument document)
+		{
+			this.document = document;
+		}
+		
+		[Conditional("DEBUG")]
+		static void Log(string text)
+		{
+			Debug.WriteLine("TextAnchorTree: " + text);
+		}
+		
+		#region Insert Text
+		void InsertText(int offset, int length, bool defaultAnchorMovementIsBeforeInsertion)
+		{
+			if (length == 0 || root == null || offset > root.totalLength)
+				return;
+			
+			// find the range of nodes that are placed exactly at offset
+			// beginNode is inclusive, endNode is exclusive
+			if (offset == root.totalLength) {
+				PerformInsertText(FindActualBeginNode(root.RightMost), null, length, defaultAnchorMovementIsBeforeInsertion);
+			} else {
+				TextAnchorNode endNode = FindNode(ref offset);
+				Debug.Assert(endNode.length > 0);
+				
+				if (offset > 0) {
+					// there are no nodes exactly at offset
+					endNode.length += length;
+					UpdateAugmentedData(endNode);
+				} else {
+					PerformInsertText(FindActualBeginNode(endNode.Predecessor), endNode, length, defaultAnchorMovementIsBeforeInsertion);
+				}
+			}
+			DeleteMarkedNodes();
+		}
+		
+		TextAnchorNode FindActualBeginNode(TextAnchorNode node)
+		{
+			// now find the actual beginNode
+			while (node != null && node.length == 0)
+				node = node.Predecessor;
+			if (node == null) {
+				// no predecessor = beginNode is first node in tree
+				node = root.LeftMost;
+			}
+			return node;
+		}
+		
+		// Sorts the nodes in the range [beginNode, endNode) by MovementType
+		// and inserts the length between the BeforeInsertion and the AfterInsertion nodes.
+		void PerformInsertText(TextAnchorNode beginNode, TextAnchorNode endNode, int length, bool defaultAnchorMovementIsBeforeInsertion)
+		{
+			Debug.Assert(beginNode != null);
+			// endNode may be null at the end of the anchor tree
+			
+			// now we need to sort the nodes in the range [beginNode, endNode); putting those with
+			// MovementType.BeforeInsertion in front of those with MovementType.AfterInsertion
+			List<TextAnchorNode> beforeInsert = new List<TextAnchorNode>();
+			//List<TextAnchorNode> afterInsert = new List<TextAnchorNode>();
+			TextAnchorNode temp = beginNode;
+			while (temp != endNode) {
+				TextAnchor anchor = (TextAnchor)temp.Target;
+				if (anchor == null) {
+					// afterInsert.Add(temp);
+					MarkNodeForDelete(temp);
+				} else if (defaultAnchorMovementIsBeforeInsertion
+				           ? anchor.MovementType != AnchorMovementType.AfterInsertion
+				           : anchor.MovementType == AnchorMovementType.BeforeInsertion)
+				{
+					beforeInsert.Add(temp);
+//				} else {
+//					afterInsert.Add(temp);
+				}
+				temp = temp.Successor;
+			}
+			// now again go through the range and swap the nodes with those in the beforeInsert list
+			temp = beginNode;
+			foreach (TextAnchorNode node in beforeInsert) {
+				SwapAnchors(node, temp);
+				temp = temp.Successor;
+			}
+			// now temp is pointing to the first node that is afterInsert,
+			// or to endNode, if there is no afterInsert node at the offset
+			// So add the length to temp
+			if (temp == null) {
+				// temp might be null if endNode==null and no afterInserts
+				Debug.Assert(endNode == null);
+			} else {
+				temp.length += length;
+				UpdateAugmentedData(temp);
+			}
+		}
+		
+		/// <summary>
+		/// Swaps the anchors stored in the two nodes.
+		/// </summary>
+		void SwapAnchors(TextAnchorNode n1, TextAnchorNode n2)
+		{
+			if (n1 != n2) {
+				TextAnchor anchor1 = (TextAnchor)n1.Target;
+				TextAnchor anchor2 = (TextAnchor)n2.Target;
+				if (anchor1 == null && anchor2 == null) {
+					// -> no swap required
+					return;
+				}
+				n1.Target = anchor2;
+				n2.Target = anchor1;
+				if (anchor1 == null) {
+					// unmark n1 from deletion, mark n2 for deletion
+					nodesToDelete.Remove(n1);
+					MarkNodeForDelete(n2);
+					anchor2.node = n1;
+				} else if (anchor2 == null) {
+					// unmark n2 from deletion, mark n1 for deletion
+					nodesToDelete.Remove(n2);
+					MarkNodeForDelete(n1);
+					anchor1.node = n2;
+				} else {
+					anchor1.node = n2;
+					anchor2.node = n1;
+				}
+			}
+		}
+		#endregion
+		
+		#region Remove or Replace text
+		public void HandleTextChange(OffsetChangeMapEntry entry, DelayedEvents delayedEvents)
+		{
+			//Log("HandleTextChange(" + entry + ")");
+			if (entry.RemovalLength == 0) {
+				// This is a pure insertion.
+				// Unlike a replace with removal, a pure insertion can result in nodes at the same location
+				// to split depending on their MovementType.
+				// Thus, we handle this case on a separate code path
+				// (the code below looks like it does something similar, but it can only split
+				// the set of deletion survivors, not all nodes at an offset)
+				InsertText(entry.Offset, entry.InsertionLength, entry.DefaultAnchorMovementIsBeforeInsertion);
+				return;
+			}
+			// When handling a replacing text change, we need to:
+			// - find all anchors in the deleted segment and delete them / move them to the appropriate
+			//   surviving side.
+			// - adjust the segment size between the left and right side
+			
+			int offset = entry.Offset;
+			int remainingRemovalLength = entry.RemovalLength;
+			// if the text change is happening after the last anchor, we don't have to do anything
+			if (root == null || offset >= root.totalLength)
+				return;
+			TextAnchorNode node = FindNode(ref offset);
+			TextAnchorNode firstDeletionSurvivor = null;
+			// go forward through the tree and delete all nodes in the removal segment
+			while (node != null && offset + remainingRemovalLength > node.length) {
+				TextAnchor anchor = (TextAnchor)node.Target;
+				if (anchor != null && (anchor.SurviveDeletion || entry.RemovalNeverCausesAnchorDeletion)) {
+					if (firstDeletionSurvivor == null)
+						firstDeletionSurvivor = node;
+					// This node should be deleted, but it wants to survive.
+					// We'll just remove the deleted length segment, so the node will be positioned
+					// in front of the removed segment.
+					remainingRemovalLength -= node.length - offset;
+					node.length = offset;
+					offset = 0;
+					UpdateAugmentedData(node);
+					node = node.Successor;
+				} else {
+					// delete node
+					TextAnchorNode s = node.Successor;
+					remainingRemovalLength -= node.length;
+					RemoveNode(node);
+					// we already deleted the node, don't delete it twice
+					nodesToDelete.Remove(node);
+					if (anchor != null)
+						anchor.OnDeleted(delayedEvents);
+					node = s;
+				}
+			}
+			// 'node' now is the first anchor after the deleted segment.
+			// If there are no anchors after the deleted segment, 'node' is null.
+			
+			// firstDeletionSurvivor was set to the first node surviving deletion.
+			// Because all non-surviving nodes up to 'node' were deleted, the node range
+			// [firstDeletionSurvivor, node) now refers to the set of all deletion survivors.
+			
+			// do the remaining job of the removal
+			if (node != null) {
+				node.length -= remainingRemovalLength;
+				Debug.Assert(node.length >= 0);
+			}
+			if (entry.InsertionLength > 0) {
+				// we are performing a replacement
+				if (firstDeletionSurvivor != null) {
+					// We got deletion survivors which need to be split into BeforeInsertion
+					// and AfterInsertion groups.
+					// Take care that we don't regroup everything at offset, but only the deletion
+					// survivors - from firstDeletionSurvivor (inclusive) to node (exclusive).
+					// This ensures that nodes immediately before or after the replaced segment
+					// stay where they are (independent from their MovementType)
+					PerformInsertText(firstDeletionSurvivor, node, entry.InsertionLength, entry.DefaultAnchorMovementIsBeforeInsertion);
+				} else if (node != null) {
+					// No deletion survivors:
+					// just perform the insertion
+					node.length += entry.InsertionLength;
+				}
+			}
+			if (node != null) {
+				UpdateAugmentedData(node);
+			}
+			DeleteMarkedNodes();
+		}
+		#endregion
+		
+		#region Node removal when TextAnchor was GC'ed
+		void MarkNodeForDelete(TextAnchorNode node)
+		{
+			if (!nodesToDelete.Contains(node))
+				nodesToDelete.Add(node);
+		}
+		
+		void DeleteMarkedNodes()
+		{
+			CheckProperties();
+			while (nodesToDelete.Count > 0) {
+				int pos = nodesToDelete.Count - 1;
+				TextAnchorNode n = nodesToDelete[pos];
+				// combine section of n with the following section
+				TextAnchorNode s = n.Successor;
+				if (s != null) {
+					s.length += n.length;
+				}
+				RemoveNode(n);
+				if (s != null) {
+					UpdateAugmentedData(s);
+				}
+				nodesToDelete.RemoveAt(pos);
+				CheckProperties();
+			}
+			CheckProperties();
+		}
+		#endregion
+		
+		#region FindNode
+		/// <summary>
+		/// Finds the node at the specified offset.
+		/// After the method has run, offset is relative to the beginning of the returned node.
+		/// </summary>
+		TextAnchorNode FindNode(ref int offset)
+		{
+			TextAnchorNode n = root;
+			while (true) {
+				if (n.left != null) {
+					if (offset < n.left.totalLength) {
+						n = n.left; // descend into left subtree
+						continue;
+					} else {
+						offset -= n.left.totalLength; // skip left subtree
+					}
+				}
+				if (!n.IsAlive)
+					MarkNodeForDelete(n);
+				if (offset < n.length) {
+					return n; // found correct node
+				} else {
+					offset -= n.length; // skip this node
+				}
+				if (n.right != null) {
+					n = n.right; // descend into right subtree
+				} else {
+					// didn't find any node containing the offset
+					return null;
+				}
+			}
+		}
+		#endregion
+		
+		#region UpdateAugmentedData
+		void UpdateAugmentedData(TextAnchorNode n)
+		{
+			if (!n.IsAlive)
+				MarkNodeForDelete(n);
+			
+			int totalLength = n.length;
+			if (n.left != null)
+				totalLength += n.left.totalLength;
+			if (n.right != null)
+				totalLength += n.right.totalLength;
+			if (n.totalLength != totalLength) {
+				n.totalLength = totalLength;
+				if (n.parent != null)
+					UpdateAugmentedData(n.parent);
+			}
+		}
+		#endregion
+		
+		#region CreateAnchor
+		public TextAnchor CreateAnchor(int offset)
+		{
+			Log("CreateAnchor(" + offset + ")");
+			TextAnchor anchor = new TextAnchor(document);
+			anchor.node = new TextAnchorNode(anchor);
+			if (root == null) {
+				// creating the first text anchor
+				root = anchor.node;
+				root.totalLength = root.length = offset;
+			} else if (offset >= root.totalLength) {
+				// append anchor at end of tree
+				anchor.node.totalLength = anchor.node.length = offset - root.totalLength;
+				InsertAsRight(root.RightMost, anchor.node);
+			} else {
+				// insert anchor in middle of tree
+				TextAnchorNode n = FindNode(ref offset);
+				Debug.Assert(offset < n.length);
+				// split segment 'n' at offset
+				anchor.node.totalLength = anchor.node.length = offset;
+				n.length -= offset;
+				InsertBefore(n, anchor.node);
+			}
+			DeleteMarkedNodes();
+			return anchor;
+		}
+		
+		void InsertBefore(TextAnchorNode node, TextAnchorNode newNode)
+		{
+			if (node.left == null) {
+				InsertAsLeft(node, newNode);
+			} else {
+				InsertAsRight(node.left.RightMost, newNode);
+			}
+		}
+		#endregion
+		
+		#region Red/Black Tree
+		internal const bool RED = true;
+		internal const bool BLACK = false;
+		
+		void InsertAsLeft(TextAnchorNode parentNode, TextAnchorNode newNode)
+		{
+			Debug.Assert(parentNode.left == null);
+			parentNode.left = newNode;
+			newNode.parent = parentNode;
+			newNode.color = RED;
+			UpdateAugmentedData(parentNode);
+			FixTreeOnInsert(newNode);
+		}
+		
+		void InsertAsRight(TextAnchorNode parentNode, TextAnchorNode newNode)
+		{
+			Debug.Assert(parentNode.right == null);
+			parentNode.right = newNode;
+			newNode.parent = parentNode;
+			newNode.color = RED;
+			UpdateAugmentedData(parentNode);
+			FixTreeOnInsert(newNode);
+		}
+		
+		void FixTreeOnInsert(TextAnchorNode node)
+		{
+			Debug.Assert(node != null);
+			Debug.Assert(node.color == RED);
+			Debug.Assert(node.left == null || node.left.color == BLACK);
+			Debug.Assert(node.right == null || node.right.color == BLACK);
+			
+			TextAnchorNode parentNode = node.parent;
+			if (parentNode == null) {
+				// we inserted in the root -> the node must be black
+				// since this is a root node, making the node black increments the number of black nodes
+				// on all paths by one, so it is still the same for all paths.
+				node.color = BLACK;
+				return;
+			}
+			if (parentNode.color == BLACK) {
+				// if the parent node where we inserted was black, our red node is placed correctly.
+				// since we inserted a red node, the number of black nodes on each path is unchanged
+				// -> the tree is still balanced
+				return;
+			}
+			// parentNode is red, so there is a conflict here!
+			
+			// because the root is black, parentNode is not the root -> there is a grandparent node
+			TextAnchorNode grandparentNode = parentNode.parent;
+			TextAnchorNode uncleNode = Sibling(parentNode);
+			if (uncleNode != null && uncleNode.color == RED) {
+				parentNode.color = BLACK;
+				uncleNode.color = BLACK;
+				grandparentNode.color = RED;
+				FixTreeOnInsert(grandparentNode);
+				return;
+			}
+			// now we know: parent is red but uncle is black
+			// First rotation:
+			if (node == parentNode.right && parentNode == grandparentNode.left) {
+				RotateLeft(parentNode);
+				node = node.left;
+			} else if (node == parentNode.left && parentNode == grandparentNode.right) {
+				RotateRight(parentNode);
+				node = node.right;
+			}
+			// because node might have changed, reassign variables:
+			parentNode = node.parent;
+			grandparentNode = parentNode.parent;
+			
+			// Now recolor a bit:
+			parentNode.color = BLACK;
+			grandparentNode.color = RED;
+			// Second rotation:
+			if (node == parentNode.left && parentNode == grandparentNode.left) {
+				RotateRight(grandparentNode);
+			} else {
+				// because of the first rotation, this is guaranteed:
+				Debug.Assert(node == parentNode.right && parentNode == grandparentNode.right);
+				RotateLeft(grandparentNode);
+			}
+		}
+		
+		void RemoveNode(TextAnchorNode removedNode)
+		{
+			if (removedNode.left != null && removedNode.right != null) {
+				// replace removedNode with it's in-order successor
+				
+				TextAnchorNode leftMost = removedNode.right.LeftMost;
+				RemoveNode(leftMost); // remove leftMost from its current location
+				
+				// and overwrite the removedNode with it
+				ReplaceNode(removedNode, leftMost);
+				leftMost.left = removedNode.left;
+				if (leftMost.left != null) leftMost.left.parent = leftMost;
+				leftMost.right = removedNode.right;
+				if (leftMost.right != null) leftMost.right.parent = leftMost;
+				leftMost.color = removedNode.color;
+				
+				UpdateAugmentedData(leftMost);
+				if (leftMost.parent != null) UpdateAugmentedData(leftMost.parent);
+				return;
+			}
+			
+			// now either removedNode.left or removedNode.right is null
+			// get the remaining child
+			TextAnchorNode parentNode = removedNode.parent;
+			TextAnchorNode childNode = removedNode.left ?? removedNode.right;
+			ReplaceNode(removedNode, childNode);
+			if (parentNode != null) UpdateAugmentedData(parentNode);
+			if (removedNode.color == BLACK) {
+				if (childNode != null && childNode.color == RED) {
+					childNode.color = BLACK;
+				} else {
+					FixTreeOnDelete(childNode, parentNode);
+				}
+			}
+		}
+		
+		void FixTreeOnDelete(TextAnchorNode node, TextAnchorNode parentNode)
+		{
+			Debug.Assert(node == null || node.parent == parentNode);
+			if (parentNode == null)
+				return;
+			
+			// warning: node may be null
+			TextAnchorNode sibling = Sibling(node, parentNode);
+			if (sibling.color == RED) {
+				parentNode.color = RED;
+				sibling.color = BLACK;
+				if (node == parentNode.left) {
+					RotateLeft(parentNode);
+				} else {
+					RotateRight(parentNode);
+				}
+				
+				sibling = Sibling(node, parentNode); // update value of sibling after rotation
+			}
+			
+			if (parentNode.color == BLACK
+			    && sibling.color == BLACK
+			    && GetColor(sibling.left) == BLACK
+			    && GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				FixTreeOnDelete(parentNode, parentNode.parent);
+				return;
+			}
+			
+			if (parentNode.color == RED
+			    && sibling.color == BLACK
+			    && GetColor(sibling.left) == BLACK
+			    && GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				parentNode.color = BLACK;
+				return;
+			}
+			
+			if (node == parentNode.left &&
+			    sibling.color == BLACK &&
+			    GetColor(sibling.left) == RED &&
+			    GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				sibling.left.color = BLACK;
+				RotateRight(sibling);
+			}
+			else if (node == parentNode.right &&
+			         sibling.color == BLACK &&
+			         GetColor(sibling.right) == RED &&
+			         GetColor(sibling.left) == BLACK)
+			{
+				sibling.color = RED;
+				sibling.right.color = BLACK;
+				RotateLeft(sibling);
+			}
+			sibling = Sibling(node, parentNode); // update value of sibling after rotation
+			
+			sibling.color = parentNode.color;
+			parentNode.color = BLACK;
+			if (node == parentNode.left) {
+				if (sibling.right != null) {
+					Debug.Assert(sibling.right.color == RED);
+					sibling.right.color = BLACK;
+				}
+				RotateLeft(parentNode);
+			} else {
+				if (sibling.left != null) {
+					Debug.Assert(sibling.left.color == RED);
+					sibling.left.color = BLACK;
+				}
+				RotateRight(parentNode);
+			}
+		}
+		
+		void ReplaceNode(TextAnchorNode replacedNode, TextAnchorNode newNode)
+		{
+			if (replacedNode.parent == null) {
+				Debug.Assert(replacedNode == root);
+				root = newNode;
+			} else {
+				if (replacedNode.parent.left == replacedNode)
+					replacedNode.parent.left = newNode;
+				else
+					replacedNode.parent.right = newNode;
+			}
+			if (newNode != null) {
+				newNode.parent = replacedNode.parent;
+			}
+			replacedNode.parent = null;
+		}
+		
+		void RotateLeft(TextAnchorNode p)
+		{
+			// let q be p's right child
+			TextAnchorNode q = p.right;
+			Debug.Assert(q != null);
+			Debug.Assert(q.parent == p);
+			// set q to be the new root
+			ReplaceNode(p, q);
+			
+			// set p's right child to be q's left child
+			p.right = q.left;
+			if (p.right != null) p.right.parent = p;
+			// set q's left child to be p
+			q.left = p;
+			p.parent = q;
+			UpdateAugmentedData(p);
+			UpdateAugmentedData(q);
+		}
+		
+		void RotateRight(TextAnchorNode p)
+		{
+			// let q be p's left child
+			TextAnchorNode q = p.left;
+			Debug.Assert(q != null);
+			Debug.Assert(q.parent == p);
+			// set q to be the new root
+			ReplaceNode(p, q);
+			
+			// set p's left child to be q's right child
+			p.left = q.right;
+			if (p.left != null) p.left.parent = p;
+			// set q's right child to be p
+			q.right = p;
+			p.parent = q;
+			UpdateAugmentedData(p);
+			UpdateAugmentedData(q);
+		}
+		
+		static TextAnchorNode Sibling(TextAnchorNode node)
+		{
+			if (node == node.parent.left)
+				return node.parent.right;
+			else
+				return node.parent.left;
+		}
+		
+		static TextAnchorNode Sibling(TextAnchorNode node, TextAnchorNode parentNode)
+		{
+			Debug.Assert(node == null || node.parent == parentNode);
+			if (node == parentNode.left)
+				return parentNode.right;
+			else
+				return parentNode.left;
+		}
+		
+		static bool GetColor(TextAnchorNode node)
+		{
+			return node != null ? node.color : BLACK;
+		}
+		#endregion
+		
+		#region CheckProperties
+		[Conditional("DATACONSISTENCYTEST")]
+		internal void CheckProperties()
+		{
+			#if DEBUG
+			if (root != null) {
+				CheckProperties(root);
+				
+				// check red-black property:
+				int blackCount = -1;
+				CheckNodeProperties(root, null, RED, 0, ref blackCount);
+			}
+			#endif
+		}
+		
+		#if DEBUG
+		void CheckProperties(TextAnchorNode node)
+		{
+			int totalLength = node.length;
+			if (node.left != null) {
+				CheckProperties(node.left);
+				totalLength += node.left.totalLength;
+			}
+			if (node.right != null) {
+				CheckProperties(node.right);
+				totalLength += node.right.totalLength;
+			}
+			Debug.Assert(node.totalLength == totalLength);
+		}
+		
+		/*
+		1. A node is either red or black.
+		2. The root is black.
+		3. All leaves are black. (The leaves are the NIL children.)
+		4. Both children of every red node are black. (So every red node must have a black parent.)
+		5. Every simple path from a node to a descendant leaf contains the same number of black nodes. (Not counting the leaf node.)
+		 */
+		void CheckNodeProperties(TextAnchorNode node, TextAnchorNode parentNode, bool parentColor, int blackCount, ref int expectedBlackCount)
+		{
+			if (node == null) return;
+			
+			Debug.Assert(node.parent == parentNode);
+			
+			if (parentColor == RED) {
+				Debug.Assert(node.color == BLACK);
+			}
+			if (node.color == BLACK) {
+				blackCount++;
+			}
+			if (node.left == null && node.right == null) {
+				// node is a leaf node:
+				if (expectedBlackCount == -1)
+					expectedBlackCount = blackCount;
+				else
+					Debug.Assert(expectedBlackCount == blackCount);
+			}
+			CheckNodeProperties(node.left, node, node.color, blackCount, ref expectedBlackCount);
+			CheckNodeProperties(node.right, node, node.color, blackCount, ref expectedBlackCount);
+		}
+		#endif
+		#endregion
+		
+		#region GetTreeAsString
+		#if DEBUG
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+		public string GetTreeAsString()
+		{
+			if (root == null)
+				return "<empty tree>";
+			StringBuilder b = new StringBuilder();
+			AppendTreeToString(root, b, 0);
+			return b.ToString();
+		}
+		
+		static void AppendTreeToString(TextAnchorNode node, StringBuilder b, int indent)
+		{
+			if (node.color == RED)
+				b.Append("RED   ");
+			else
+				b.Append("BLACK ");
+			b.AppendLine(node.ToString());
+			indent += 2;
+			if (node.left != null) {
+				b.Append(' ', indent);
+				b.Append("L: ");
+				AppendTreeToString(node.left, b, indent);
+			}
+			if (node.right != null) {
+				b.Append(' ', indent);
+				b.Append("R: ");
+				AppendTreeToString(node.right, b, indent);
+			}
+		}
+		#endif
+		#endregion
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextDocument.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextDocument.cs
new file mode 100644
index 000000000..84fc86f44
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextDocument.cs
@@ -0,0 +1,836 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.Linq;
+using System.Globalization;
+using System.Linq.Expressions;
+using System.Threading;
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// This class is the main class of the text model. Basically, it is a <see cref="System.Text.StringBuilder"/> with events.
+	/// </summary>
+	/// <remarks>
+	/// <b>Thread safety:</b>
+	/// <inheritdoc cref="VerifyAccess"/>
+	/// <para>However, there is a single method that is thread-safe: <see cref="CreateSnapshot()"/> (and its overloads).</para>
+	/// </remarks>
+	public sealed class TextDocument : ITextSource, INotifyPropertyChanged
+	{
+		#region Thread ownership
+		readonly object lockObject = new object();
+		Thread owner = Thread.CurrentThread;
+		
+		/// <summary>
+		/// Verifies that the current thread is the documents owner thread.
+		/// Throws an <see cref="InvalidOperationException"/> if the wrong thread accesses the TextDocument.
+		/// </summary>
+		/// <remarks>
+		/// <para>The TextDocument class is not thread-safe. A document instance expects to have a single owner thread
+		/// and will throw an <see cref="InvalidOperationException"/> when accessed from another thread.
+		/// It is possible to change the owner thread using the <see cref="SetOwnerThread"/> method.</para>
+		/// </remarks>
+		public void VerifyAccess()
+		{
+			if (Thread.CurrentThread != owner)
+				throw new InvalidOperationException("TextDocument can be accessed only from the thread that owns it.");
+		}
+		
+		/// <summary>
+		/// Transfers ownership of the document to another thread. This method can be used to load
+		/// a file into a TextDocument on a background thread and then transfer ownership to the UI thread
+		/// for displaying the document.
+		/// </summary>
+		/// <remarks>
+		/// <inheritdoc cref="VerifyAccess"/>
+		/// <para>
+		/// The owner can be set to null, which means that no thread can access the document. But, if the document
+		/// has no owner thread, any thread may take ownership by calling <see cref="SetOwnerThread"/>.
+		/// </para>
+		/// </remarks>
+		public void SetOwnerThread(Thread newOwner)
+		{
+			// We need to lock here to ensure that in the null owner case,
+			// only one thread succeeds in taking ownership.
+			lock (lockObject) {
+				if (owner != null) {
+					VerifyAccess();
+				}
+				owner = newOwner;
+			}
+		}
+		#endregion
+		
+		#region Fields + Constructor
+		readonly Rope<char> rope;
+		readonly DocumentLineTree lineTree;
+		readonly LineManager lineManager;
+		readonly TextAnchorTree anchorTree;
+		ChangeTrackingCheckpoint currentCheckpoint;
+		
+		/// <summary>
+		/// Create an empty text document.
+		/// </summary>
+		public TextDocument()
+			: this(string.Empty)
+		{
+		}
+		
+		/// <summary>
+		/// Create a new text document with the specified initial text.
+		/// </summary>
+		public TextDocument(IEnumerable<char> initialText)
+		{
+			if (initialText == null)
+				throw new ArgumentNullException("initialText");
+			rope = new Rope<char>(initialText);
+			lineTree = new DocumentLineTree(this);
+			lineManager = new LineManager(lineTree, this);
+			lineTrackers.CollectionChanged += delegate {
+				lineManager.UpdateListOfLineTrackers();
+			};
+			
+			anchorTree = new TextAnchorTree(this);
+			undoStack = new UndoStack();
+			FireChangeEvents();
+		}
+		
+		/// <summary>
+		/// Create a new text document with the specified initial text.
+		/// </summary>
+		public TextDocument(ITextSource initialText)
+			: this(GetTextFromTextSource(initialText))
+		{
+		}
+		
+		// gets the text from a text source, directly retrieving the underlying rope where possible
+		static IEnumerable<char> GetTextFromTextSource(ITextSource textSource)
+		{
+			if (textSource == null)
+				throw new ArgumentNullException("textSource");
+			
+			RopeTextSource rts = textSource as RopeTextSource;
+			if (rts != null)
+				return rts.GetRope();
+			
+			TextDocument doc = textSource as TextDocument;
+			if (doc != null)
+				return doc.rope;
+			
+			return textSource.Text;
+		}
+		#endregion
+		
+		#region Text
+		void ThrowIfRangeInvalid(int offset, int length)
+		{
+			if (offset < 0 || offset > rope.Length) {
+				throw new ArgumentOutOfRangeException("offset", offset, "0 <= offset <= " + rope.Length.ToString(CultureInfo.InvariantCulture));
+			}
+			if (length < 0 || offset + length > rope.Length) {
+				throw new ArgumentOutOfRangeException("length", length, "0 <= length, offset(" + offset + ")+length <= " + rope.Length.ToString(CultureInfo.InvariantCulture));
+			}
+		}
+		
+		/// <inheritdoc/>
+		public string GetText(int offset, int length)
+		{
+			VerifyAccess();
+			return rope.ToString(offset, length);
+		}
+		
+		/// <summary>
+		/// Retrieves the text for a portion of the document.
+		/// </summary>
+		public string GetText(ISegment segment)
+		{
+			if (segment == null)
+				throw new ArgumentNullException("segment");
+			return GetText(segment.Offset, segment.Length);
+		}
+		
+		int ITextSource.IndexOfAny(char[] anyOf, int startIndex, int count)
+		{
+			DebugVerifyAccess(); // frequently called (NewLineFinder), so must be fast in release builds
+			return rope.IndexOfAny(anyOf, startIndex, count);
+		}
+		
+		/// <inheritdoc/>
+		public char GetCharAt(int offset)
+		{
+			DebugVerifyAccess(); // frequently called, so must be fast in release builds
+			return rope[offset];
+		}
+		
+		WeakReference cachedText;
+		
+		/// <summary>
+		/// Gets/Sets the text of the whole document.
+		/// </summary>
+		public string Text {
+			get {
+				VerifyAccess();
+				string completeText = cachedText != null ? (cachedText.Target as string) : null;
+				if (completeText == null) {
+					completeText = rope.ToString();
+					cachedText = new WeakReference(completeText);
+				}
+				return completeText;
+			}
+			set {
+				VerifyAccess();
+				if (value == null)
+					throw new ArgumentNullException("value");
+				Replace(0, rope.Length, value);
+			}
+		}
+		
+		/// <inheritdoc/>
+		/// <remarks><inheritdoc cref="Changing"/></remarks>
+		public event EventHandler TextChanged;
+		
+		/// <inheritdoc/>
+		public int TextLength {
+			get {
+				VerifyAccess();
+				return rope.Length;
+			}
+		}
+		
+		/// <summary>
+		/// Is raised when the TextLength property changes.
+		/// </summary>
+		/// <remarks><inheritdoc cref="Changing"/></remarks>
+		[Obsolete("This event will be removed in a future version; use the PropertyChanged event instead")]
+		public event EventHandler TextLengthChanged;
+		
+		/// <summary>
+		/// Is raised when one of the properties <see cref="Text"/>, <see cref="TextLength"/>, <see cref="LineCount"/>,
+		/// <see cref="UndoStack"/> changes.
+		/// </summary>
+		/// <remarks><inheritdoc cref="Changing"/></remarks>
+		public event PropertyChangedEventHandler PropertyChanged;
+		
+		/// <summary>
+		/// Is raised before the document changes.
+		/// </summary>
+		/// <remarks>
+		/// <para>Here is the order in which events are raised during a document update:</para>
+		/// <list type="bullet">
+		/// <item><description><b><see cref="BeginUpdate">BeginUpdate()</see></b></description>
+		///   <list type="bullet">
+		///   <item><description>Start of change group (on undo stack)</description></item>
+		///   <item><description><see cref="UpdateStarted"/> event is raised</description></item>
+		///   </list></item>
+		/// <item><description><b><see cref="Insert(int,string)">Insert()</see> / <see cref="Remove(int,int)">Remove()</see> / <see cref="Replace(int,int,string)">Replace()</see></b></description>
+		///   <list type="bullet">
+		///   <item><description><see cref="Changing"/> event is raised</description></item>
+		///   <item><description>The document is changed</description></item>
+		///   <item><description><see cref="TextAnchor.Deleted">TextAnchor.Deleted</see> event is raised if anchors were
+		///     in the deleted text portion</description></item>
+		///   <item><description><see cref="Changed"/> event is raised</description></item>
+		///   </list></item>
+		/// <item><description><b><see cref="EndUpdate">EndUpdate()</see></b></description>
+		///   <list type="bullet">
+		///   <item><description><see cref="TextChanged"/> event is raised</description></item>
+		///   <item><description><see cref="PropertyChanged"/> event is raised (for the Text, TextLength, LineCount properties, in that order)</description></item>
+		///   <item><description>End of change group (on undo stack)</description></item>
+		///   <item><description><see cref="UpdateFinished"/> event is raised</description></item>
+		///   </list></item>
+		/// </list>
+		/// <para>
+		/// If the insert/remove/replace methods are called without a call to <c>BeginUpdate()</c>,
+		/// they will call <c>BeginUpdate()</c> and <c>EndUpdate()</c> to ensure no change happens outside of <c>UpdateStarted</c>/<c>UpdateFinished</c>.
+		/// </para><para>
+		/// There can be multiple document changes between the <c>BeginUpdate()</c> and <c>EndUpdate()</c> calls.
+		/// In this case, the events associated with EndUpdate will be raised only once after the whole document update is done.
+		/// </para><para>
+		/// The <see cref="UndoStack"/> listens to the <c>UpdateStarted</c> and <c>UpdateFinished</c> events to group all changes into a single undo step.
+		/// </para>
+		/// </remarks>
+		public event EventHandler<DocumentChangeEventArgs> Changing;
+		
+		/// <summary>
+		/// Is raised after the document has changed.
+		/// </summary>
+		/// <remarks><inheritdoc cref="Changing"/></remarks>
+		public event EventHandler<DocumentChangeEventArgs> Changed;
+		
+		/// <summary>
+		/// Creates a snapshot of the current text.
+		/// </summary>
+		/// <remarks>
+		/// <para>This method returns an immutable snapshot of the document, and may be safely called even when
+		/// the document's owner thread is concurrently modifying the document.
+		/// </para><para>
+		/// This special thread-safety guarantee is valid only for TextDocument.CreateSnapshot(), not necessarily for other
+		/// classes implementing ITextSource.CreateSnapshot().
+		/// </para><para>
+		/// </para>
+		/// </remarks>
+		public ITextSource CreateSnapshot()
+		{
+			lock (lockObject) {
+				return new RopeTextSource(rope.Clone());
+			}
+		}
+		
+		/// <summary>
+		/// Creates a snapshot of the current text.
+		/// Additionally, creates a checkpoint that allows tracking document changes.
+		/// </summary>
+		/// <remarks><inheritdoc cref="CreateSnapshot()"/><inheritdoc cref="ChangeTrackingCheckpoint"/></remarks>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1021:AvoidOutParameters", Justification = "Need to return snapshot and checkpoint together to ensure thread-safety")]
+		public ITextSource CreateSnapshot(out ChangeTrackingCheckpoint checkpoint)
+		{
+			lock (lockObject) {
+				if (currentCheckpoint == null)
+					currentCheckpoint = new ChangeTrackingCheckpoint(lockObject);
+				checkpoint = currentCheckpoint;
+				return new RopeTextSource(rope.Clone());
+			}
+		}
+		
+		internal ChangeTrackingCheckpoint CreateChangeTrackingCheckpoint()
+		{
+			lock (lockObject) {
+				if (currentCheckpoint == null)
+					currentCheckpoint = new ChangeTrackingCheckpoint(lockObject);
+				return currentCheckpoint;
+			}
+		}
+		
+		/// <summary>
+		/// Creates a snapshot of a part of the current text.
+		/// </summary>
+		/// <remarks><inheritdoc cref="CreateSnapshot()"/></remarks>
+		public ITextSource CreateSnapshot(int offset, int length)
+		{
+			lock (lockObject) {
+				return new RopeTextSource(rope.GetRange(offset, length));
+			}
+		}
+		
+		/// <inheritdoc/>
+		public System.IO.TextReader CreateReader()
+		{
+			lock (lockObject) {
+				return new RopeTextReader(rope);
+			}
+		}
+		#endregion
+		
+		#region BeginUpdate / EndUpdate
+		int beginUpdateCount;
+		
+		/// <summary>
+		/// Gets if an update is running.
+		/// </summary>
+		/// <remarks><inheritdoc cref="BeginUpdate"/></remarks>
+		public bool IsInUpdate {
+			get {
+				VerifyAccess();
+				return beginUpdateCount > 0;
+			}
+		}
+		
+		/// <summary>
+		/// Immediately calls <see cref="BeginUpdate()"/>,
+		/// and returns an IDisposable that calls <see cref="EndUpdate()"/>.
+		/// </summary>
+		/// <remarks><inheritdoc cref="BeginUpdate"/></remarks>
+		public IDisposable RunUpdate()
+		{
+			BeginUpdate();
+			return new CallbackOnDispose(EndUpdate);
+		}
+		
+		/// <summary>
+		/// <para>Begins a group of document changes.</para>
+		/// <para>Some events are suspended until EndUpdate is called, and the <see cref="UndoStack"/> will
+		/// group all changes into a single action.</para>
+		/// <para>Calling BeginUpdate several times increments a counter, only after the appropriate number
+		/// of EndUpdate calls the events resume their work.</para>
+		/// </summary>
+		/// <remarks><inheritdoc cref="Changing"/></remarks>
+		public void BeginUpdate()
+		{
+			VerifyAccess();
+			if (inDocumentChanging)
+				throw new InvalidOperationException("Cannot change document within another document change.");
+			beginUpdateCount++;
+			if (beginUpdateCount == 1) {
+				undoStack.StartUndoGroup();
+				if (UpdateStarted != null)
+					UpdateStarted(this, EventArgs.Empty);
+			}
+		}
+		
+		/// <summary>
+		/// Ends a group of document changes.
+		/// </summary>
+		/// <remarks><inheritdoc cref="Changing"/></remarks>
+		public void EndUpdate()
+		{
+			VerifyAccess();
+			if (inDocumentChanging)
+				throw new InvalidOperationException("Cannot end update within document change.");
+			if (beginUpdateCount == 0)
+				throw new InvalidOperationException("No update is active.");
+			if (beginUpdateCount == 1) {
+				// fire change events inside the change group - event handlers might add additional
+				// document changes to the change group
+				FireChangeEvents();
+				undoStack.EndUndoGroup();
+				beginUpdateCount = 0;
+				if (UpdateFinished != null)
+					UpdateFinished(this, EventArgs.Empty);
+			} else {
+				beginUpdateCount -= 1;
+			}
+		}
+		
+		/// <summary>
+		/// Occurs when a document change starts.
+		/// </summary>
+		/// <remarks><inheritdoc cref="Changing"/></remarks>
+		public event EventHandler UpdateStarted;
+		
+		/// <summary>
+		/// Occurs when a document change is finished.
+		/// </summary>
+		/// <remarks><inheritdoc cref="Changing"/></remarks>
+		public event EventHandler UpdateFinished;
+		#endregion
+		
+		#region Fire events after update
+		int oldTextLength;
+		int oldLineCount;
+		bool fireTextChanged;
+		
+		/// <summary>
+		/// Fires TextChanged, TextLengthChanged, LineCountChanged if required.
+		/// </summary>
+		internal void FireChangeEvents()
+		{
+			// it may be necessary to fire the event multiple times if the document is changed
+			// from inside the event handlers
+			while (fireTextChanged) {
+				fireTextChanged = false;
+				if (TextChanged != null)
+					TextChanged(this, EventArgs.Empty);
+				OnPropertyChanged("Text");
+				
+				int textLength = rope.Length;
+				if (textLength != oldTextLength) {
+					oldTextLength = textLength;
+					if (TextLengthChanged != null)
+						TextLengthChanged(this, EventArgs.Empty);
+					OnPropertyChanged("TextLength");
+				}
+				int lineCount = lineTree.LineCount;
+				if (lineCount != oldLineCount) {
+					oldLineCount = lineCount;
+					if (LineCountChanged != null)
+						LineCountChanged(this, EventArgs.Empty);
+					OnPropertyChanged("LineCount");
+				}
+			}
+		}
+		
+		void OnPropertyChanged(string propertyName)
+		{
+			if (PropertyChanged != null)
+				PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
+		}
+		#endregion
+		
+		#region Insert / Remove  / Replace
+		/// <summary>
+		/// Inserts text.
+		/// </summary>
+		public void Insert(int offset, string text)
+		{
+			Replace(offset, 0, text);
+		}
+		
+		/// <summary>
+		/// Removes text.
+		/// </summary>
+		public void Remove(ISegment segment)
+		{
+			Replace(segment, string.Empty);
+		}
+		
+		/// <summary>
+		/// Removes text.
+		/// </summary>
+		public void Remove(int offset, int length)
+		{
+			Replace(offset, length, string.Empty);
+		}
+		
+		internal bool inDocumentChanging;
+		
+		/// <summary>
+		/// Replaces text.
+		/// </summary>
+		public void Replace(ISegment segment, string text)
+		{
+			if (segment == null)
+				throw new ArgumentNullException("segment");
+			Replace(segment.Offset, segment.Length, text, null);
+		}
+		
+		/// <summary>
+		/// Replaces text.
+		/// </summary>
+		public void Replace(int offset, int length, string text)
+		{
+			Replace(offset, length, text, null);
+		}
+		
+		/// <summary>
+		/// Replaces text.
+		/// </summary>
+		/// <param name="offset">The starting offset of the text to be replaced.</param>
+		/// <param name="length">The length of the text to be replaced.</param>
+		/// <param name="text">The new text.</param>
+		/// <param name="offsetChangeMappingType">The offsetChangeMappingType determines how offsets inside the old text are mapped to the new text.
+		/// This affects how the anchors and segments inside the replaced region behave.</param>
+		public void Replace(int offset, int length, string text, OffsetChangeMappingType offsetChangeMappingType)
+		{
+			if (text == null)
+				throw new ArgumentNullException("text");
+			// Please see OffsetChangeMappingType XML comments for details on how these modes work.
+			switch (offsetChangeMappingType) {
+				case OffsetChangeMappingType.Normal:
+					Replace(offset, length, text, null);
+					break;
+				case OffsetChangeMappingType.KeepAnchorBeforeInsertion:
+					Replace(offset, length, text, OffsetChangeMap.FromSingleElement(
+						new OffsetChangeMapEntry(offset, length, text.Length, false, true)));
+					break;
+				case OffsetChangeMappingType.RemoveAndInsert:
+					if (length == 0 || text.Length == 0) {
+						// only insertion or only removal?
+						// OffsetChangeMappingType doesn't matter, just use Normal.
+						Replace(offset, length, text, null);
+					} else {
+						OffsetChangeMap map = new OffsetChangeMap(2);
+						map.Add(new OffsetChangeMapEntry(offset, length, 0));
+						map.Add(new OffsetChangeMapEntry(offset, 0, text.Length));
+						map.Freeze();
+						Replace(offset, length, text, map);
+					}
+					break;
+				case OffsetChangeMappingType.CharacterReplace:
+					if (length == 0 || text.Length == 0) {
+						// only insertion or only removal?
+						// OffsetChangeMappingType doesn't matter, just use Normal.
+						Replace(offset, length, text, null);
+					} else if (text.Length > length) {
+						// look at OffsetChangeMappingType.CharacterReplace XML comments on why we need to replace
+						// the last character
+						OffsetChangeMapEntry entry = new OffsetChangeMapEntry(offset + length - 1, 1, 1 + text.Length - length);
+						Replace(offset, length, text, OffsetChangeMap.FromSingleElement(entry));
+					} else if (text.Length < length) {
+						OffsetChangeMapEntry entry = new OffsetChangeMapEntry(offset + text.Length, length - text.Length, 0, true, false);
+						Replace(offset, length, text, OffsetChangeMap.FromSingleElement(entry));
+					} else {
+						Replace(offset, length, text, OffsetChangeMap.Empty);
+					}
+					break;
+				default:
+					throw new ArgumentOutOfRangeException("offsetChangeMappingType", offsetChangeMappingType, "Invalid enum value");
+			}
+		}
+		
+		/// <summary>
+		/// Replaces text.
+		/// </summary>
+		/// <param name="offset">The starting offset of the text to be replaced.</param>
+		/// <param name="length">The length of the text to be replaced.</param>
+		/// <param name="text">The new text.</param>
+		/// <param name="offsetChangeMap">The offsetChangeMap determines how offsets inside the old text are mapped to the new text.
+		/// This affects how the anchors and segments inside the replaced region behave.
+		/// If you pass null (the default when using one of the other overloads), the offsets are changed as
+		/// in OffsetChangeMappingType.Normal mode.
+		/// If you pass OffsetChangeMap.Empty, then everything will stay in its old place (OffsetChangeMappingType.CharacterReplace mode).
+		/// The offsetChangeMap must be a valid 'explanation' for the document change. See <see cref="OffsetChangeMap.IsValidForDocumentChange"/>.
+		/// Passing an OffsetChangeMap to the Replace method will automatically freeze it to ensure the thread safety of the resulting
+		/// DocumentChangeEventArgs instance.
+		/// </param>
+		public void Replace(int offset, int length, string text, OffsetChangeMap offsetChangeMap)
+		{
+			if (text == null)
+				throw new ArgumentNullException("text");
+			
+			if (offsetChangeMap != null)
+				offsetChangeMap.Freeze();
+			
+			// Ensure that all changes take place inside an update group.
+			// Will also take care of throwing an exception if inDocumentChanging is set.
+			BeginUpdate();
+			try {
+				// protect document change against corruption by other changes inside the event handlers
+				inDocumentChanging = true;
+				try {
+					// The range verification must wait until after the BeginUpdate() call because the document
+					// might be modified inside the UpdateStarted event.
+					ThrowIfRangeInvalid(offset, length);
+					
+					DoReplace(offset, length, text, offsetChangeMap);
+				} finally {
+					inDocumentChanging = false;
+				}
+			} finally {
+				EndUpdate();
+			}
+		}
+		
+		void DoReplace(int offset, int length, string newText, OffsetChangeMap offsetChangeMap)
+		{
+			if (length == 0 && newText.Length == 0)
+				return;
+			
+			// trying to replace a single character in 'Normal' mode?
+			// for single characters, 'CharacterReplace' mode is equivalent, but more performant
+			// (we don't have to touch the anchorTree at all in 'CharacterReplace' mode)
+			if (length == 1 && newText.Length == 1 && offsetChangeMap == null)
+				offsetChangeMap = OffsetChangeMap.Empty;
+			
+			string removedText = rope.ToString(offset, length);
+			DocumentChangeEventArgs args = new DocumentChangeEventArgs(offset, removedText, newText, offsetChangeMap);
+			
+			// fire DocumentChanging event
+			if (Changing != null)
+				Changing(this, args);
+			
+			undoStack.Push(this, args);
+			
+			cachedText = null; // reset cache of complete document text
+			fireTextChanged = true;
+			DelayedEvents delayedEvents = new DelayedEvents();
+			
+			lock (lockObject) {
+				// create linked list of checkpoints, if required
+				if (currentCheckpoint != null) {
+					currentCheckpoint = currentCheckpoint.Append(args);
+				}
+				
+				// now update the textBuffer and lineTree
+				if (offset == 0 && length == rope.Length) {
+					// optimize replacing the whole document
+					rope.Clear();
+					rope.InsertText(0, newText);
+					lineManager.Rebuild();
+				} else {
+					rope.RemoveRange(offset, length);
+					lineManager.Remove(offset, length);
+					#if DEBUG
+					lineTree.CheckProperties();
+					#endif
+					rope.InsertText(offset, newText);
+					lineManager.Insert(offset, newText);
+					#if DEBUG
+					lineTree.CheckProperties();
+					#endif
+				}
+			}
+			
+			// update text anchors
+			if (offsetChangeMap == null) {
+				anchorTree.HandleTextChange(args.CreateSingleChangeMapEntry(), delayedEvents);
+			} else {
+				foreach (OffsetChangeMapEntry entry in offsetChangeMap) {
+					anchorTree.HandleTextChange(entry, delayedEvents);
+				}
+			}
+			
+			// raise delayed events after our data structures are consistent again
+			delayedEvents.RaiseEvents();
+			
+			// fire DocumentChanged event
+			if (Changed != null)
+				Changed(this, args);
+		}
+		#endregion
+		
+		#region GetLineBy...
+		/// <summary>
+		/// Gets a read-only list of lines.
+		/// </summary>
+		/// <remarks><inheritdoc cref="DocumentLine"/></remarks>
+		public IList<DocumentLine> Lines {
+			get { return lineTree; }
+		}
+		
+		/// <summary>
+		/// Gets a line by the line number: O(log n)
+		/// </summary>
+		public DocumentLine GetLineByNumber(int number)
+		{
+			VerifyAccess();
+			if (number < 1 || number > lineTree.LineCount)
+				throw new ArgumentOutOfRangeException("number", number, "Value must be between 1 and " + lineTree.LineCount);
+			return lineTree.GetByNumber(number);
+		}
+		
+		/// <summary>
+		/// Gets a document lines by offset.
+		/// Runtime: O(log n)
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Globalization", "CA1305:SpecifyIFormatProvider", MessageId = "System.Int32.ToString")]
+		public DocumentLine GetLineByOffset(int offset)
+		{
+			VerifyAccess();
+			if (offset < 0 || offset > rope.Length) {
+				throw new ArgumentOutOfRangeException("offset", offset, "0 <= offset <= " + rope.Length.ToString());
+			}
+			return lineTree.GetByOffset(offset);
+		}
+		#endregion
+		
+		/// <summary>
+		/// Gets the offset from a text location.
+		/// </summary>
+		/// <seealso cref="GetLocation"/>
+		public int GetOffset(TextLocation location)
+		{
+			return GetOffset(location.Line, location.Column);
+		}
+		
+		/// <summary>
+		/// Gets the offset from a text location.
+		/// </summary>
+		/// <seealso cref="GetLocation"/>
+		public int GetOffset(int line, int column)
+		{
+			DocumentLine docLine = GetLineByNumber(line);
+			if (column <= 0)
+				return docLine.Offset;
+			if (column > docLine.Length)
+				return docLine.EndOffset;
+			return docLine.Offset + column - 1;
+		}
+		
+		/// <summary>
+		/// Gets the location from an offset.
+		/// </summary>
+		/// <seealso cref="GetOffset(TextLocation)"/>
+		public TextLocation GetLocation(int offset)
+		{
+			DocumentLine line = GetLineByOffset(offset);
+			return new TextLocation(line.LineNumber, offset - line.Offset + 1);
+		}
+		
+		readonly ObservableCollection<ILineTracker> lineTrackers = new ObservableCollection<ILineTracker>();
+		
+		/// <summary>
+		/// Gets the list of <see cref="ILineTracker"/>s attached to this document.
+		/// You can add custom line trackers to this list.
+		/// </summary>
+		public IList<ILineTracker> LineTrackers {
+			get {
+				VerifyAccess();
+				return lineTrackers;
+			}
+		}
+		
+		UndoStack undoStack;
+		
+		/// <summary>
+		/// Gets the <see cref="UndoStack"/> of the document.
+		/// </summary>
+		/// <remarks>This property can also be used to set the undo stack, e.g. for sharing a common undo stack between multiple documents.</remarks>
+		public UndoStack UndoStack {
+			get { return undoStack; }
+			set {
+				if (value == null)
+					throw new ArgumentNullException();
+				if (value != undoStack) {
+					undoStack.ClearAll(); // first clear old undo stack, so that it can't be used to perform unexpected changes on this document
+					// ClearAll() will also throw an exception when it's not safe to replace the undo stack (e.g. update is currently in progress)
+					undoStack = value;
+					OnPropertyChanged("UndoStack");
+				}
+			}
+		}
+		
+		/// <summary>
+		/// Creates a new <see cref="TextAnchor"/> at the specified offset.
+		/// </summary>
+		/// <inheritdoc cref="TextAnchor" select="remarks|example"/>
+		public TextAnchor CreateAnchor(int offset)
+		{
+			VerifyAccess();
+			if (offset < 0 || offset > rope.Length) {
+				throw new ArgumentOutOfRangeException("offset", offset, "0 <= offset <= " + rope.Length.ToString(CultureInfo.InvariantCulture));
+			}
+			return anchorTree.CreateAnchor(offset);
+		}
+		
+		#region LineCount
+		/// <summary>
+		/// Gets the total number of lines in the document.
+		/// Runtime: O(1).
+		/// </summary>
+		public int LineCount {
+			get {
+				VerifyAccess();
+				return lineTree.LineCount;
+			}
+		}
+		
+		/// <summary>
+		/// Is raised when the LineCount property changes.
+		/// </summary>
+		[Obsolete("This event will be removed in a future version; use the PropertyChanged event instead")]
+		public event EventHandler LineCountChanged;
+		#endregion
+		
+		#region Debugging
+		[Conditional("DEBUG")]
+		internal void DebugVerifyAccess()
+		{
+			VerifyAccess();
+		}
+		
+		/// <summary>
+		/// Gets the document lines tree in string form.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate")]
+		internal string GetLineTreeAsString()
+		{
+			#if DEBUG
+			return lineTree.GetTreeAsString();
+			#else
+			return "Not available in release build.";
+			#endif
+		}
+		
+		/// <summary>
+		/// Gets the text anchor tree in string form.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode")]
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1024:UsePropertiesWhereAppropriate")]
+		internal string GetTextAnchorTreeAsString()
+		{
+			#if DEBUG
+			return anchorTree.GetTreeAsString();
+			#else
+			return "Not available in release build.";
+			#endif
+		}
+		#endregion
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextDocumentWeakEventManager.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextDocumentWeakEventManager.cs
new file mode 100644
index 000000000..de304b722
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextDocumentWeakEventManager.cs
@@ -0,0 +1,149 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Contains weak event managers for the TextDocument events.
+	/// </summary>
+	public static class TextDocumentWeakEventManager
+	{
+		/// <summary>
+		/// Weak event manager for the <see cref="TextDocument.UpdateStarted"/> event.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible")]
+		public sealed class UpdateStarted : WeakEventManagerBase<UpdateStarted, TextDocument>
+		{
+			/// <inheritdoc/>
+			protected override void StartListening(TextDocument source)
+			{
+				source.UpdateStarted += DeliverEvent;
+			}
+			
+			/// <inheritdoc/>
+			protected override void StopListening(TextDocument source)
+			{
+				source.UpdateStarted -= DeliverEvent;
+			}
+		}
+		
+		/// <summary>
+		/// Weak event manager for the <see cref="TextDocument.UpdateFinished"/> event.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible")]
+		public sealed class UpdateFinished : WeakEventManagerBase<UpdateFinished, TextDocument>
+		{
+			/// <inheritdoc/>
+			protected override void StartListening(TextDocument source)
+			{
+				source.UpdateFinished += DeliverEvent;
+			}
+			
+			/// <inheritdoc/>
+			protected override void StopListening(TextDocument source)
+			{
+				source.UpdateFinished -= DeliverEvent;
+			}
+		}
+		
+		/// <summary>
+		/// Weak event manager for the <see cref="TextDocument.Changing"/> event.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible")]
+		public sealed class Changing : WeakEventManagerBase<Changing, TextDocument>
+		{
+			/// <inheritdoc/>
+			protected override void StartListening(TextDocument source)
+			{
+				source.Changing += DeliverEvent;
+			}
+			
+			/// <inheritdoc/>
+			protected override void StopListening(TextDocument source)
+			{
+				source.Changing -= DeliverEvent;
+			}
+		}
+		
+		/// <summary>
+		/// Weak event manager for the <see cref="TextDocument.Changed"/> event.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible")]
+		public sealed class Changed : WeakEventManagerBase<Changed, TextDocument>
+		{
+			/// <inheritdoc/>
+			protected override void StartListening(TextDocument source)
+			{
+				source.Changed += DeliverEvent;
+			}
+			
+			/// <inheritdoc/>
+			protected override void StopListening(TextDocument source)
+			{
+				source.Changed -= DeliverEvent;
+			}
+		}
+		
+		/// <summary>
+		/// Weak event manager for the <see cref="TextDocument.LineCountChanged"/> event.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible")]
+		[Obsolete("The TextDocument.LineCountChanged event will be removed in a future version. Use PropertyChangedEventManager instead.")]
+		public sealed class LineCountChanged : WeakEventManagerBase<LineCountChanged, TextDocument>
+		{
+			/// <inheritdoc/>
+			protected override void StartListening(TextDocument source)
+			{
+				source.LineCountChanged += DeliverEvent;
+			}
+			
+			/// <inheritdoc/>
+			protected override void StopListening(TextDocument source)
+			{
+				source.LineCountChanged -= DeliverEvent;
+			}
+		}
+		
+		/// <summary>
+		/// Weak event manager for the <see cref="TextDocument.TextLengthChanged"/> event.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible")]
+		[Obsolete("The TextDocument.TextLengthChanged event will be removed in a future version. Use PropertyChangedEventManager instead.")]
+		public sealed class TextLengthChanged : WeakEventManagerBase<TextLengthChanged, TextDocument>
+		{
+			/// <inheritdoc/>
+			protected override void StartListening(TextDocument source)
+			{
+				source.TextLengthChanged += DeliverEvent;
+			}
+			
+			/// <inheritdoc/>
+			protected override void StopListening(TextDocument source)
+			{
+				source.TextLengthChanged -= DeliverEvent;
+			}
+		}
+		
+		/// <summary>
+		/// Weak event manager for the <see cref="TextDocument.TextChanged"/> event.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible")]
+		public sealed class TextChanged : WeakEventManagerBase<TextChanged, TextDocument>
+		{
+			/// <inheritdoc/>
+			protected override void StartListening(TextDocument source)
+			{
+				source.TextChanged += DeliverEvent;
+			}
+			
+			/// <inheritdoc/>
+			protected override void StopListening(TextDocument source)
+			{
+				source.TextChanged -= DeliverEvent;
+			}
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextLocation.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextLocation.cs
new file mode 100644
index 000000000..1d3c2564c
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextLocation.cs
@@ -0,0 +1,166 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Globalization;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// A line/column position.
+	/// Text editor lines/columns are counted started from one.
+	/// </summary>
+	/// <remarks>
+	/// The document provides the methods <see cref="TextDocument.GetLocation"/> and
+	/// <see cref="TextDocument.GetOffset(TextLocation)"/> to convert between offsets and TextLocations.
+	/// </remarks>
+	public struct TextLocation : IComparable<TextLocation>, IEquatable<TextLocation>
+	{
+		/// <summary>
+		/// Represents no text location (0, 0).
+		/// </summary>
+		public static readonly TextLocation Empty = new TextLocation(0, 0);
+		
+		/// <summary>
+		/// Creates a TextLocation instance.
+		/// <para>
+		/// Warning: the parameters are (line, column).
+		/// Not (column, line) as in ICSharpCode.TextEditor!
+		/// </para>
+		/// </summary>
+		public TextLocation(int line, int column)
+		{
+			y = line;
+			x = column;
+		}
+		
+		int x, y;
+		
+		/// <summary>
+		/// Gets the line number.
+		/// </summary>
+		public int Line {
+			get { return y; }
+		}
+		
+		/// <summary>
+		/// Gets the column number.
+		/// </summary>
+		public int Column {
+			get { return x; }
+		}
+		
+		/// <summary>
+		/// Gets whether the TextLocation instance is empty.
+		/// </summary>
+		public bool IsEmpty {
+			get {
+				return x <= 0 && y <= 0;
+			}
+		}
+		
+		/// <summary>
+		/// Gets a string representation for debugging purposes.
+		/// </summary>
+		public override string ToString()
+		{
+			return string.Format(CultureInfo.InvariantCulture, "(Line {1}, Col {0})", this.x, this.y);
+		}
+		
+		/// <summary>
+		/// Gets a hash code.
+		/// </summary>
+		public override int GetHashCode()
+		{
+			return unchecked (87 * x.GetHashCode() ^ y.GetHashCode());
+		}
+		
+		/// <summary>
+		/// Equality test.
+		/// </summary>
+		public override bool Equals(object obj)
+		{
+			if (!(obj is TextLocation)) return false;
+			return (TextLocation)obj == this;
+		}
+		
+		/// <summary>
+		/// Equality test.
+		/// </summary>
+		public bool Equals(TextLocation other)
+		{
+			return this == other;
+		}
+		
+		/// <summary>
+		/// Equality test.
+		/// </summary>
+		public static bool operator ==(TextLocation left, TextLocation right)
+		{
+			return left.x == right.x && left.y == right.y;
+		}
+		
+		/// <summary>
+		/// Inequality test.
+		/// </summary>
+		public static bool operator !=(TextLocation left, TextLocation right)
+		{
+			return left.x != right.x || left.y != right.y;
+		}
+		
+		/// <summary>
+		/// Compares two text locations.
+		/// </summary>
+		public static bool operator <(TextLocation left, TextLocation right)
+		{
+			if (left.y < right.y)
+				return true;
+			else if (left.y == right.y)
+				return left.x < right.x;
+			else
+				return false;
+		}
+		
+		/// <summary>
+		/// Compares two text locations.
+		/// </summary>
+		public static bool operator >(TextLocation left, TextLocation right)
+		{
+			if (left.y > right.y)
+				return true;
+			else if (left.y == right.y)
+				return left.x > right.x;
+			else
+				return false;
+		}
+		
+		/// <summary>
+		/// Compares two text locations.
+		/// </summary>
+		public static bool operator <=(TextLocation left, TextLocation right)
+		{
+			return !(left > right);
+		}
+		
+		/// <summary>
+		/// Compares two text locations.
+		/// </summary>
+		public static bool operator >=(TextLocation left, TextLocation right)
+		{
+			return !(left < right);
+		}
+		
+		/// <summary>
+		/// Compares two text locations.
+		/// </summary>
+		public int CompareTo(TextLocation other)
+		{
+			if (this == other)
+				return 0;
+			if (this < other)
+				return -1;
+			else
+				return 1;
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextSegment.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextSegment.cs
new file mode 100644
index 000000000..d1834c214
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextSegment.cs
@@ -0,0 +1,248 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Diagnostics;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// A segment that can be put into a <see cref="TextSegmentCollection{T}"/>.
+	/// </summary>
+	/// <remarks>
+	/// <para>
+	/// A <see cref="TextSegment"/> can be stand-alone or part of a <see cref="TextSegmentCollection{T}"/>.
+	/// If the segment is stored inside a TextSegmentCollection, its Offset and Length will be updated by that collection.
+	/// </para>
+	/// <para>
+	/// When the document changes, the offsets of all text segments in the TextSegmentCollection will be adjusted accordingly.
+	/// Start offsets move like <see cref="AnchorMovementType">AnchorMovementType.AfterInsertion</see>,
+	/// end offsets move like <see cref="AnchorMovementType">AnchorMovementType.BeforeInsertion</see>
+	/// (i.e. the segment will always stay as small as possible).</para>
+	/// <para>
+	/// If a document change causes a segment to be deleted completely, it will be reduced to length 0, but segments are
+	/// never automatically removed from the collection.
+	/// Segments with length 0 will never expand due to document changes, and they move as <c>AfterInsertion</c>.
+	/// </para>
+	/// <para>
+	/// Thread-safety: a TextSegmentCollection that is connected to a <see cref="TextDocument"/> may only be used on that document's owner thread.
+	/// A disconnected TextSegmentCollection is safe for concurrent reads, but concurrent access is not safe when there are writes.
+	/// Keep in mind that reading the Offset properties of a text segment inside the collection is a read access on the
+	/// collection; and setting an Offset property of a text segment is a write access on the collection.
+	/// </para>
+	/// </remarks>
+	/// <seealso cref="ISegment"/>
+	/// <seealso cref="AnchorSegment"/>
+	/// <seealso cref="TextSegmentCollection{T}"/>
+	public class TextSegment : ISegment
+	{
+		internal ISegmentTree ownerTree;
+		internal TextSegment left, right, parent;
+		
+		/// <summary>
+		/// The color of the segment in the red/black tree.
+		/// </summary>
+		internal bool color;
+		
+		/// <summary>
+		/// The "length" of the node (distance to previous node)
+		/// </summary>
+		internal int nodeLength;
+		
+		/// <summary>
+		/// The total "length" of this subtree.
+		/// </summary>
+		internal int totalNodeLength; // totalNodeLength = nodeLength + left.totalNodeLength + right.totalNodeLength
+		
+		/// <summary>
+		/// The length of the segment (do not confuse with nodeLength).
+		/// </summary>
+		internal int segmentLength;
+		
+		/// <summary>
+		/// distanceToMaxEnd = Max(segmentLength,
+		///                        left.distanceToMaxEnd + left.Offset - Offset,
+		///                        left.distanceToMaxEnd + right.Offset - Offset)
+		/// </summary>
+		internal int distanceToMaxEnd;
+		
+		int ISegment.Offset {
+			get { return StartOffset; }
+		}
+		
+		/// <summary>
+		/// Gets whether this segment is connected to a TextSegmentCollection and will automatically
+		/// update its offsets.
+		/// </summary>
+		protected bool IsConnectedToCollection {
+			get {
+				return ownerTree != null;
+			}
+		}
+		
+		/// <summary>
+		/// Gets/Sets the start offset of the segment.
+		/// </summary>
+		/// <remarks>
+		/// When setting the start offset, the end offset will change, too: the Length of the segment will stay constant.
+		/// </remarks>
+		public int StartOffset {
+			get {
+				// If the segment is not connected to a tree, we store the offset in "nodeLength".
+				// Otherwise, "nodeLength" contains the distance to the start offset of the previous node
+				Debug.Assert(!(ownerTree == null && parent != null));
+				Debug.Assert(!(ownerTree == null && left != null));
+				
+				TextSegment n = this;
+				int offset = n.nodeLength;
+				if (n.left != null)
+					offset += n.left.totalNodeLength;
+				while (n.parent != null) {
+					if (n == n.parent.right) {
+						if (n.parent.left != null)
+							offset += n.parent.left.totalNodeLength;
+						offset += n.parent.nodeLength;
+					}
+					n = n.parent;
+				}
+				return offset;
+			}
+			set {
+				if (value < 0)
+					throw new ArgumentOutOfRangeException("value", "Offset must not be negative");
+				if (this.StartOffset != value) {
+					// need a copy of the variable because ownerTree.Remove() sets this.ownerTree to null
+					ISegmentTree ownerTree = this.ownerTree;
+					if (ownerTree != null) {
+						ownerTree.Remove(this);
+						nodeLength = value;
+						ownerTree.Add(this);
+					} else {
+						nodeLength = value;
+					}
+					OnSegmentChanged();
+				}
+			}
+		}
+		
+		/// <summary>
+		/// Gets/Sets the end offset of the segment.
+		/// </summary>
+		/// <remarks>
+		/// Setting the end offset will change the length, the start offset will stay constant.
+		/// </remarks>
+		public int EndOffset {
+			get {
+				return StartOffset + Length;
+			}
+			set {
+				int newLength = value - StartOffset;
+				if (newLength < 0)
+					throw new ArgumentOutOfRangeException("value", "EndOffset must be greater or equal to StartOffset");
+				Length = newLength;
+			}
+		}
+		
+		/// <summary>
+		/// Gets/Sets the length of the segment.
+		/// </summary>
+		/// <remarks>
+		/// Setting the length will change the end offset, the start offset will stay constant.
+		/// </remarks>
+		public int Length {
+			get {
+				return segmentLength;
+			}
+			set {
+				if (value < 0)
+					throw new ArgumentOutOfRangeException("value", "Length must not be negative");
+				if (segmentLength != value) {
+					segmentLength = value;
+					if (ownerTree != null)
+						ownerTree.UpdateAugmentedData(this);
+					OnSegmentChanged();
+				}
+			}
+		}
+		
+		/// <summary>
+		/// This method gets called when the StartOffset/Length/EndOffset properties are set.
+		/// It is not called when StartOffset/Length/EndOffset change due to document changes
+		/// </summary>
+		protected virtual void OnSegmentChanged()
+		{
+		}
+		
+		internal TextSegment LeftMost {
+			get {
+				TextSegment node = this;
+				while (node.left != null)
+					node = node.left;
+				return node;
+			}
+		}
+		
+		internal TextSegment RightMost {
+			get {
+				TextSegment node = this;
+				while (node.right != null)
+					node = node.right;
+				return node;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the inorder successor of the node.
+		/// </summary>
+		internal TextSegment Successor {
+			get {
+				if (right != null) {
+					return right.LeftMost;
+				} else {
+					TextSegment node = this;
+					TextSegment oldNode;
+					do {
+						oldNode = node;
+						node = node.parent;
+						// go up until we are coming out of a left subtree
+					} while (node != null && node.right == oldNode);
+					return node;
+				}
+			}
+		}
+		
+		/// <summary>
+		/// Gets the inorder predecessor of the node.
+		/// </summary>
+		internal TextSegment Predecessor {
+			get {
+				if (left != null) {
+					return left.RightMost;
+				} else {
+					TextSegment node = this;
+					TextSegment oldNode;
+					do {
+						oldNode = node;
+						node = node.parent;
+						// go up until we are coming out of a right subtree
+					} while (node != null && node.left == oldNode);
+					return node;
+				}
+			}
+		}
+		
+		#if DEBUG
+		internal string ToDebugString()
+		{
+			return "[nodeLength=" + nodeLength + " totalNodeLength=" + totalNodeLength
+				+ " distanceToMaxEnd=" + distanceToMaxEnd + " MaxEndOffset=" + (StartOffset + distanceToMaxEnd) + "]";
+		}
+		#endif
+		
+		/// <inheritdoc/>
+		public override string ToString()
+		{
+			return "[" + GetType().Name + " Offset=" + StartOffset + " Length=" + Length + " EndOffset=" + EndOffset + "]";
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextSegmentCollection.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextSegmentCollection.cs
new file mode 100644
index 000000000..549dbb77d
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextSegmentCollection.cs
@@ -0,0 +1,971 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using Tango.Scripting.Editors.Utils;
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics;
+using System.Linq;
+using System.Text;
+using System.Windows;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Interface to allow TextSegments to access the TextSegmentCollection - we cannot use a direct reference
+	/// because TextSegmentCollection is generic.
+	/// </summary>
+	interface ISegmentTree
+	{
+		void Add(TextSegment s);
+		void Remove(TextSegment s);
+		void UpdateAugmentedData(TextSegment s);
+	}
+	
+	/// <summary>
+	/// <para>
+	/// A collection of text segments that supports efficient lookup of segments
+	/// intersecting with another segment.
+	/// </para>
+	/// </summary>
+	/// <remarks><inheritdoc cref="TextSegment"/></remarks>
+	/// <see cref="TextSegment"/>
+	public sealed class TextSegmentCollection<T> : ICollection<T>, ISegmentTree, IWeakEventListener where T : TextSegment
+	{
+		// Implementation: this is basically a mixture of an augmented interval tree
+		// and the TextAnchorTree.
+		
+		// WARNING: you need to understand interval trees (the version with the augmented 'high'/'max' field)
+		// and how the TextAnchorTree works before you have any chance of understanding this code.
+		
+		// This means that every node holds two "segments":
+		// one like the segments in the text anchor tree to support efficient offset changes
+		// and another that is the interval as seen by the user
+		
+		// So basically, the tree contains a list of contiguous node segments of the first kind,
+		// with interval segments starting at the end of every node segment.
+		
+		// Performance:
+		// Add is O(lg n)
+		// Remove is O(lg n)
+		// DocumentChanged is O(m * lg n), with m the number of segments that intersect with the changed document section
+		// FindFirstSegmentWithStartAfter is O(m + lg n) with m being the number of segments at the same offset as the result segment
+		// FindIntersectingSegments is O(m + lg n) with m being the number of intersecting segments.
+		
+		int count;
+		TextSegment root;
+		bool isConnectedToDocument;
+		
+		#region Constructor
+		/// <summary>
+		/// Creates a new TextSegmentCollection that needs manual calls to <see cref="UpdateOffsets(DocumentChangeEventArgs)"/>.
+		/// </summary>
+		public TextSegmentCollection()
+		{
+		}
+		
+		/// <summary>
+		/// Creates a new TextSegmentCollection that updates the offsets automatically.
+		/// </summary>
+		/// <param name="textDocument">The document to which the text segments
+		/// that will be added to the tree belong. When the document changes, the
+		/// position of the text segments will be updated accordingly.</param>
+		public TextSegmentCollection(TextDocument textDocument)
+		{
+			if (textDocument == null)
+				throw new ArgumentNullException("textDocument");
+			
+			textDocument.VerifyAccess();
+			isConnectedToDocument = true;
+			TextDocumentWeakEventManager.Changed.AddListener(textDocument, this);
+		}
+		#endregion
+		
+		#region OnDocumentChanged / UpdateOffsets
+		bool IWeakEventListener.ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+		{
+			if (managerType == typeof(TextDocumentWeakEventManager.Changed)) {
+				OnDocumentChanged((DocumentChangeEventArgs)e);
+				return true;
+			}
+			return false;
+		}
+		
+		/// <summary>
+		/// Updates the start and end offsets of all segments stored in this collection.
+		/// </summary>
+		/// <param name="e">DocumentChangeEventArgs instance describing the change to the document.</param>
+		public void UpdateOffsets(DocumentChangeEventArgs e)
+		{
+			if (e == null)
+				throw new ArgumentNullException("e");
+			if (isConnectedToDocument)
+				throw new InvalidOperationException("This TextSegmentCollection will automatically update offsets; do not call UpdateOffsets manually!");
+			OnDocumentChanged(e);
+			CheckProperties();
+		}
+		
+		void OnDocumentChanged(DocumentChangeEventArgs e)
+		{
+			OffsetChangeMap map = e.OffsetChangeMapOrNull;
+			if (map != null) {
+				foreach (OffsetChangeMapEntry entry in map) {
+					UpdateOffsetsInternal(entry);
+				}
+			} else {
+				UpdateOffsetsInternal(e.CreateSingleChangeMapEntry());
+			}
+		}
+		
+		/// <summary>
+		/// Updates the start and end offsets of all segments stored in this collection.
+		/// </summary>
+		/// <param name="change">OffsetChangeMapEntry instance describing the change to the document.</param>
+		public void UpdateOffsets(OffsetChangeMapEntry change)
+		{
+			if (isConnectedToDocument)
+				throw new InvalidOperationException("This TextSegmentCollection will automatically update offsets; do not call UpdateOffsets manually!");
+			UpdateOffsetsInternal(change);
+			CheckProperties();
+		}
+		#endregion
+		
+		#region UpdateOffsets (implementation)
+		void UpdateOffsetsInternal(OffsetChangeMapEntry change)
+		{
+			// Special case pure insertions, because they don't always cause a text segment to increase in size when the replaced region
+			// is inside a segment (when offset is at start or end of a text semgent).
+			if (change.RemovalLength == 0) {
+				InsertText(change.Offset, change.InsertionLength);
+			} else {
+				ReplaceText(change);
+			}
+		}
+		
+		void InsertText(int offset, int length)
+		{
+			if (length == 0)
+				return;
+			
+			// enlarge segments that contain offset (excluding those that have offset as endpoint)
+			foreach (TextSegment segment in FindSegmentsContaining(offset)) {
+				if (segment.StartOffset < offset && offset < segment.EndOffset) {
+					segment.Length += length;
+				}
+			}
+			
+			// move start offsets of all segments >= offset
+			TextSegment node = FindFirstSegmentWithStartAfter(offset);
+			if (node != null) {
+				node.nodeLength += length;
+				UpdateAugmentedData(node);
+			}
+		}
+		
+		void ReplaceText(OffsetChangeMapEntry change)
+		{
+			Debug.Assert(change.RemovalLength > 0);
+			int offset = change.Offset;
+			foreach (TextSegment segment in FindOverlappingSegments(offset, change.RemovalLength)) {
+				if (segment.StartOffset <= offset) {
+					if (segment.EndOffset >= offset + change.RemovalLength) {
+						// Replacement inside segment: adjust segment length
+						segment.Length += change.InsertionLength - change.RemovalLength;
+					} else {
+						// Replacement starting inside segment and ending after segment end: set segment end to removal position
+						//segment.EndOffset = offset;
+						segment.Length = offset - segment.StartOffset;
+					}
+				} else {
+					// Replacement starting in front of text segment and running into segment.
+					// Keep segment.EndOffset constant and move segment.StartOffset to the end of the replacement
+					int remainingLength = segment.EndOffset - (offset + change.RemovalLength);
+					RemoveSegment(segment);
+					segment.StartOffset = offset + change.RemovalLength;
+					segment.Length = Math.Max(0, remainingLength);
+					AddSegment(segment);
+				}
+			}
+			// move start offsets of all segments > offset
+			TextSegment node = FindFirstSegmentWithStartAfter(offset + 1);
+			if (node != null) {
+				Debug.Assert(node.nodeLength >= change.RemovalLength);
+				node.nodeLength += change.InsertionLength - change.RemovalLength;
+				UpdateAugmentedData(node);
+			}
+		}
+		#endregion
+		
+		#region Add
+		/// <summary>
+		/// Adds the specified segment to the tree. This will cause the segment to update when the
+		/// document changes.
+		/// </summary>
+		public void Add(T item)
+		{
+			if (item == null)
+				throw new ArgumentNullException("item");
+			if (item.ownerTree != null)
+				throw new ArgumentException("The segment is already added to a SegmentCollection.");
+			AddSegment(item);
+		}
+		
+		void ISegmentTree.Add(TextSegment s)
+		{
+			AddSegment(s);
+		}
+		
+		void AddSegment(TextSegment node)
+		{
+			int insertionOffset = node.StartOffset;
+			node.distanceToMaxEnd = node.segmentLength;
+			if (root == null) {
+				root = node;
+				node.totalNodeLength = node.nodeLength;
+			} else if (insertionOffset >= root.totalNodeLength) {
+				// append segment at end of tree
+				node.nodeLength = node.totalNodeLength = insertionOffset - root.totalNodeLength;
+				InsertAsRight(root.RightMost, node);
+			} else {
+				// insert in middle of tree
+				TextSegment n = FindNode(ref insertionOffset);
+				Debug.Assert(insertionOffset < n.nodeLength);
+				// split node segment 'n' at offset
+				node.totalNodeLength = node.nodeLength = insertionOffset;
+				n.nodeLength -= insertionOffset;
+				InsertBefore(n, node);
+			}
+			node.ownerTree = this;
+			count++;
+			CheckProperties();
+		}
+		
+		void InsertBefore(TextSegment node, TextSegment newNode)
+		{
+			if (node.left == null) {
+				InsertAsLeft(node, newNode);
+			} else {
+				InsertAsRight(node.left.RightMost, newNode);
+			}
+		}
+		#endregion
+		
+		#region GetNextSegment / GetPreviousSegment
+		/// <summary>
+		/// Gets the next segment after the specified segment.
+		/// Segments are sorted by their start offset.
+		/// Returns null if segment is the last segment.
+		/// </summary>
+		public T GetNextSegment(T segment)
+		{
+			if (!Contains(segment))
+				throw new ArgumentException("segment is not inside the segment tree");
+			return (T)segment.Successor;
+		}
+		
+		/// <summary>
+		/// Gets the previous segment before the specified segment.
+		/// Segments are sorted by their start offset.
+		/// Returns null if segment is the first segment.
+		/// </summary>
+		public T GetPreviousSegment(T segment)
+		{
+			if (!Contains(segment))
+				throw new ArgumentException("segment is not inside the segment tree");
+			return (T)segment.Predecessor;
+		}
+		#endregion
+		
+		#region FirstSegment/LastSegment
+		/// <summary>
+		/// Returns the first segment in the collection or null, if the collection is empty.
+		/// </summary>
+		public T FirstSegment {
+			get {
+				return root == null ? null : (T)root.LeftMost;
+			}
+		}
+		
+		/// <summary>
+		/// Returns the last segment in the collection or null, if the collection is empty.
+		/// </summary>
+		public T LastSegment {
+			get {
+				return root == null ? null : (T)root.RightMost;
+			}
+		}
+		#endregion
+		
+		#region FindFirstSegmentWithStartAfter
+		/// <summary>
+		/// Gets the first segment with a start offset greater or equal to <paramref name="startOffset"/>.
+		/// Returns null if no such segment is found.
+		/// </summary>
+		public T FindFirstSegmentWithStartAfter(int startOffset)
+		{
+			if (root == null)
+				return null;
+			if (startOffset <= 0)
+				return (T)root.LeftMost;
+			TextSegment s = FindNode(ref startOffset);
+			// startOffset means that the previous segment is starting at the offset we were looking for
+			while (startOffset == 0) {
+				TextSegment p = (s == null) ? root.RightMost : s.Predecessor;
+				// There must always be a predecessor: if we were looking for the first node, we would have already
+				// returned it as root.LeftMost above.
+				Debug.Assert(p != null);
+				startOffset += p.nodeLength;
+				s = p;
+			}
+			return (T)s;
+		}
+		
+		/// <summary>
+		/// Finds the node at the specified offset.
+		/// After the method has run, offset is relative to the beginning of the returned node.
+		/// </summary>
+		TextSegment FindNode(ref int offset)
+		{
+			TextSegment n = root;
+			while (true) {
+				if (n.left != null) {
+					if (offset < n.left.totalNodeLength) {
+						n = n.left; // descend into left subtree
+						continue;
+					} else {
+						offset -= n.left.totalNodeLength; // skip left subtree
+					}
+				}
+				if (offset < n.nodeLength) {
+					return n; // found correct node
+				} else {
+					offset -= n.nodeLength; // skip this node
+				}
+				if (n.right != null) {
+					n = n.right; // descend into right subtree
+				} else {
+					// didn't find any node containing the offset
+					return null;
+				}
+			}
+		}
+		#endregion
+		
+		#region FindOverlappingSegments
+		/// <summary>
+		/// Finds all segments that contain the given offset.
+		/// (StartOffset &lt;= offset &lt;= EndOffset)
+		/// Segments are returned in the order given by GetNextSegment/GetPreviousSegment.
+		/// </summary>
+		/// <returns>Returns a new collection containing the results of the query.
+		/// This means it is safe to modify the TextSegmentCollection while iterating through the result collection.</returns>
+		public ReadOnlyCollection<T> FindSegmentsContaining(int offset)
+		{
+			return FindOverlappingSegments(offset, 0);
+		}
+		
+		/// <summary>
+		/// Finds all segments that overlap with the given segment (including touching segments).
+		/// </summary>
+		/// <returns>Returns a new collection containing the results of the query.
+		/// This means it is safe to modify the TextSegmentCollection while iterating through the result collection.</returns>
+		public ReadOnlyCollection<T> FindOverlappingSegments(ISegment segment)
+		{
+			if (segment == null)
+				throw new ArgumentNullException("segment");
+			return FindOverlappingSegments(segment.Offset, segment.Length);
+		}
+		
+		/// <summary>
+		/// Finds all segments that overlap with the given segment (including touching segments).
+		/// Segments are returned in the order given by GetNextSegment/GetPreviousSegment.
+		/// </summary>
+		/// <returns>Returns a new collection containing the results of the query.
+		/// This means it is safe to modify the TextSegmentCollection while iterating through the result collection.</returns>
+		public ReadOnlyCollection<T> FindOverlappingSegments(int offset, int length)
+		{
+			ThrowUtil.CheckNotNegative(length, "length");
+			List<T> results = new List<T>();
+			if (root != null) {
+				FindOverlappingSegments(results, root, offset, offset + length);
+			}
+			return results.AsReadOnly();
+		}
+		
+		void FindOverlappingSegments(List<T> results, TextSegment node, int low, int high)
+		{
+			// low and high are relative to node.LeftMost startpos (not node.LeftMost.Offset)
+			if (high < 0) {
+				// node is irrelevant for search because all intervals in node are after high
+				return;
+			}
+			
+			// find values relative to node.Offset
+			int nodeLow = low - node.nodeLength;
+			int nodeHigh = high - node.nodeLength;
+			if (node.left != null) {
+				nodeLow -= node.left.totalNodeLength;
+				nodeHigh -= node.left.totalNodeLength;
+			}
+			
+			if (node.distanceToMaxEnd < nodeLow) {
+				// node is irrelevant for search because all intervals in node are before low
+				return;
+			}
+			
+			if (node.left != null)
+				FindOverlappingSegments(results, node.left, low, high);
+			
+			if (nodeHigh < 0) {
+				// node and everything in node.right is before low
+				return;
+			}
+			
+			if (nodeLow <= node.segmentLength) {
+				results.Add((T)node);
+			}
+			
+			if (node.right != null)
+				FindOverlappingSegments(results, node.right, nodeLow, nodeHigh);
+		}
+		#endregion
+		
+		#region UpdateAugmentedData
+		void UpdateAugmentedData(TextSegment node)
+		{
+			int totalLength = node.nodeLength;
+			int distanceToMaxEnd = node.segmentLength;
+			if (node.left != null) {
+				totalLength += node.left.totalNodeLength;
+				
+				int leftDTME = node.left.distanceToMaxEnd;
+				// dtme is relative, so convert it to the coordinates of node:
+				if (node.left.right != null)
+					leftDTME -= node.left.right.totalNodeLength;
+				leftDTME -= node.nodeLength;
+				if (leftDTME > distanceToMaxEnd)
+					distanceToMaxEnd = leftDTME;
+			}
+			if (node.right != null) {
+				totalLength += node.right.totalNodeLength;
+				
+				int rightDTME = node.right.distanceToMaxEnd;
+				// dtme is relative, so convert it to the coordinates of node:
+				rightDTME += node.right.nodeLength;
+				if (node.right.left != null)
+					rightDTME += node.right.left.totalNodeLength;
+				if (rightDTME > distanceToMaxEnd)
+					distanceToMaxEnd = rightDTME;
+			}
+			if (node.totalNodeLength != totalLength
+			    || node.distanceToMaxEnd != distanceToMaxEnd)
+			{
+				node.totalNodeLength = totalLength;
+				node.distanceToMaxEnd = distanceToMaxEnd;
+				if (node.parent != null)
+					UpdateAugmentedData(node.parent);
+			}
+		}
+		
+		void ISegmentTree.UpdateAugmentedData(TextSegment node)
+		{
+			UpdateAugmentedData(node);
+		}
+		#endregion
+		
+		#region Remove
+		/// <summary>
+		/// Removes the specified segment from the tree. This will cause the segment to not update
+		/// anymore when the document changes.
+		/// </summary>
+		public bool Remove(T item)
+		{
+			if (!Contains(item))
+				return false;
+			RemoveSegment(item);
+			return true;
+		}
+		
+		void ISegmentTree.Remove(TextSegment s)
+		{
+			RemoveSegment(s);
+		}
+		
+		void RemoveSegment(TextSegment s)
+		{
+			int oldOffset = s.StartOffset;
+			TextSegment successor = s.Successor;
+			if (successor != null)
+				successor.nodeLength += s.nodeLength;
+			RemoveNode(s);
+			if (successor != null)
+				UpdateAugmentedData(successor);
+			Disconnect(s, oldOffset);
+			CheckProperties();
+		}
+		
+		void Disconnect(TextSegment s, int offset)
+		{
+			s.left = s.right = s.parent = null;
+			s.ownerTree = null;
+			s.nodeLength = offset;
+			count--;
+		}
+		
+		/// <summary>
+		/// Removes all segments from the tree.
+		/// </summary>
+		public void Clear()
+		{
+			T[] segments = this.ToArray();
+			root = null;
+			int offset = 0;
+			foreach (TextSegment s in segments) {
+				offset += s.nodeLength;
+				Disconnect(s, offset);
+			}
+			CheckProperties();
+		}
+		#endregion
+		
+		#region CheckProperties
+		[Conditional("DATACONSISTENCYTEST")]
+		internal void CheckProperties()
+		{
+			#if DEBUG
+			if (root != null) {
+				CheckProperties(root);
+				
+				// check red-black property:
+				int blackCount = -1;
+				CheckNodeProperties(root, null, RED, 0, ref blackCount);
+			}
+			
+			int expectedCount = 0;
+			// we cannot trust LINQ not to call ICollection.Count, so we need this loop
+			// to count the elements in the tree
+			using (IEnumerator<T> en = GetEnumerator()) {
+				while (en.MoveNext()) expectedCount++;
+			}
+			Debug.Assert(count == expectedCount);
+			#endif
+		}
+		
+		#if DEBUG
+		void CheckProperties(TextSegment node)
+		{
+			int totalLength = node.nodeLength;
+			int distanceToMaxEnd = node.segmentLength;
+			if (node.left != null) {
+				CheckProperties(node.left);
+				totalLength += node.left.totalNodeLength;
+				distanceToMaxEnd = Math.Max(distanceToMaxEnd,
+				                            node.left.distanceToMaxEnd + node.left.StartOffset - node.StartOffset);
+			}
+			if (node.right != null) {
+				CheckProperties(node.right);
+				totalLength += node.right.totalNodeLength;
+				distanceToMaxEnd = Math.Max(distanceToMaxEnd,
+				                            node.right.distanceToMaxEnd + node.right.StartOffset - node.StartOffset);
+			}
+			Debug.Assert(node.totalNodeLength == totalLength);
+			Debug.Assert(node.distanceToMaxEnd == distanceToMaxEnd);
+		}
+		
+		/*
+		1. A node is either red or black.
+		2. The root is black.
+		3. All leaves are black. (The leaves are the NIL children.)
+		4. Both children of every red node are black. (So every red node must have a black parent.)
+		5. Every simple path from a node to a descendant leaf contains the same number of black nodes. (Not counting the leaf node.)
+		 */
+		void CheckNodeProperties(TextSegment node, TextSegment parentNode, bool parentColor, int blackCount, ref int expectedBlackCount)
+		{
+			if (node == null) return;
+			
+			Debug.Assert(node.parent == parentNode);
+			
+			if (parentColor == RED) {
+				Debug.Assert(node.color == BLACK);
+			}
+			if (node.color == BLACK) {
+				blackCount++;
+			}
+			if (node.left == null && node.right == null) {
+				// node is a leaf node:
+				if (expectedBlackCount == -1)
+					expectedBlackCount = blackCount;
+				else
+					Debug.Assert(expectedBlackCount == blackCount);
+			}
+			CheckNodeProperties(node.left, node, node.color, blackCount, ref expectedBlackCount);
+			CheckNodeProperties(node.right, node, node.color, blackCount, ref expectedBlackCount);
+		}
+		
+		static void AppendTreeToString(TextSegment node, StringBuilder b, int indent)
+		{
+			if (node.color == RED)
+				b.Append("RED   ");
+			else
+				b.Append("BLACK ");
+			b.AppendLine(node.ToString() + node.ToDebugString());
+			indent += 2;
+			if (node.left != null) {
+				b.Append(' ', indent);
+				b.Append("L: ");
+				AppendTreeToString(node.left, b, indent);
+			}
+			if (node.right != null) {
+				b.Append(' ', indent);
+				b.Append("R: ");
+				AppendTreeToString(node.right, b, indent);
+			}
+		}
+		#endif
+		
+		internal string GetTreeAsString()
+		{
+			#if DEBUG
+			StringBuilder b = new StringBuilder();
+			if (root != null)
+				AppendTreeToString(root, b, 0);
+			return b.ToString();
+			#else
+			return "Not available in release build.";
+			#endif
+		}
+		#endregion
+		
+		#region Red/Black Tree
+		internal const bool RED = true;
+		internal const bool BLACK = false;
+		
+		void InsertAsLeft(TextSegment parentNode, TextSegment newNode)
+		{
+			Debug.Assert(parentNode.left == null);
+			parentNode.left = newNode;
+			newNode.parent = parentNode;
+			newNode.color = RED;
+			UpdateAugmentedData(parentNode);
+			FixTreeOnInsert(newNode);
+		}
+		
+		void InsertAsRight(TextSegment parentNode, TextSegment newNode)
+		{
+			Debug.Assert(parentNode.right == null);
+			parentNode.right = newNode;
+			newNode.parent = parentNode;
+			newNode.color = RED;
+			UpdateAugmentedData(parentNode);
+			FixTreeOnInsert(newNode);
+		}
+		
+		void FixTreeOnInsert(TextSegment node)
+		{
+			Debug.Assert(node != null);
+			Debug.Assert(node.color == RED);
+			Debug.Assert(node.left == null || node.left.color == BLACK);
+			Debug.Assert(node.right == null || node.right.color == BLACK);
+			
+			TextSegment parentNode = node.parent;
+			if (parentNode == null) {
+				// we inserted in the root -> the node must be black
+				// since this is a root node, making the node black increments the number of black nodes
+				// on all paths by one, so it is still the same for all paths.
+				node.color = BLACK;
+				return;
+			}
+			if (parentNode.color == BLACK) {
+				// if the parent node where we inserted was black, our red node is placed correctly.
+				// since we inserted a red node, the number of black nodes on each path is unchanged
+				// -> the tree is still balanced
+				return;
+			}
+			// parentNode is red, so there is a conflict here!
+			
+			// because the root is black, parentNode is not the root -> there is a grandparent node
+			TextSegment grandparentNode = parentNode.parent;
+			TextSegment uncleNode = Sibling(parentNode);
+			if (uncleNode != null && uncleNode.color == RED) {
+				parentNode.color = BLACK;
+				uncleNode.color = BLACK;
+				grandparentNode.color = RED;
+				FixTreeOnInsert(grandparentNode);
+				return;
+			}
+			// now we know: parent is red but uncle is black
+			// First rotation:
+			if (node == parentNode.right && parentNode == grandparentNode.left) {
+				RotateLeft(parentNode);
+				node = node.left;
+			} else if (node == parentNode.left && parentNode == grandparentNode.right) {
+				RotateRight(parentNode);
+				node = node.right;
+			}
+			// because node might have changed, reassign variables:
+			parentNode = node.parent;
+			grandparentNode = parentNode.parent;
+			
+			// Now recolor a bit:
+			parentNode.color = BLACK;
+			grandparentNode.color = RED;
+			// Second rotation:
+			if (node == parentNode.left && parentNode == grandparentNode.left) {
+				RotateRight(grandparentNode);
+			} else {
+				// because of the first rotation, this is guaranteed:
+				Debug.Assert(node == parentNode.right && parentNode == grandparentNode.right);
+				RotateLeft(grandparentNode);
+			}
+		}
+		
+		void RemoveNode(TextSegment removedNode)
+		{
+			if (removedNode.left != null && removedNode.right != null) {
+				// replace removedNode with it's in-order successor
+				
+				TextSegment leftMost = removedNode.right.LeftMost;
+				RemoveNode(leftMost); // remove leftMost from its current location
+				
+				// and overwrite the removedNode with it
+				ReplaceNode(removedNode, leftMost);
+				leftMost.left = removedNode.left;
+				if (leftMost.left != null) leftMost.left.parent = leftMost;
+				leftMost.right = removedNode.right;
+				if (leftMost.right != null) leftMost.right.parent = leftMost;
+				leftMost.color = removedNode.color;
+				
+				UpdateAugmentedData(leftMost);
+				if (leftMost.parent != null) UpdateAugmentedData(leftMost.parent);
+				return;
+			}
+			
+			// now either removedNode.left or removedNode.right is null
+			// get the remaining child
+			TextSegment parentNode = removedNode.parent;
+			TextSegment childNode = removedNode.left ?? removedNode.right;
+			ReplaceNode(removedNode, childNode);
+			if (parentNode != null) UpdateAugmentedData(parentNode);
+			if (removedNode.color == BLACK) {
+				if (childNode != null && childNode.color == RED) {
+					childNode.color = BLACK;
+				} else {
+					FixTreeOnDelete(childNode, parentNode);
+				}
+			}
+		}
+		
+		void FixTreeOnDelete(TextSegment node, TextSegment parentNode)
+		{
+			Debug.Assert(node == null || node.parent == parentNode);
+			if (parentNode == null)
+				return;
+			
+			// warning: node may be null
+			TextSegment sibling = Sibling(node, parentNode);
+			if (sibling.color == RED) {
+				parentNode.color = RED;
+				sibling.color = BLACK;
+				if (node == parentNode.left) {
+					RotateLeft(parentNode);
+				} else {
+					RotateRight(parentNode);
+				}
+				
+				sibling = Sibling(node, parentNode); // update value of sibling after rotation
+			}
+			
+			if (parentNode.color == BLACK
+			    && sibling.color == BLACK
+			    && GetColor(sibling.left) == BLACK
+			    && GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				FixTreeOnDelete(parentNode, parentNode.parent);
+				return;
+			}
+			
+			if (parentNode.color == RED
+			    && sibling.color == BLACK
+			    && GetColor(sibling.left) == BLACK
+			    && GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				parentNode.color = BLACK;
+				return;
+			}
+			
+			if (node == parentNode.left &&
+			    sibling.color == BLACK &&
+			    GetColor(sibling.left) == RED &&
+			    GetColor(sibling.right) == BLACK)
+			{
+				sibling.color = RED;
+				sibling.left.color = BLACK;
+				RotateRight(sibling);
+			}
+			else if (node == parentNode.right &&
+			         sibling.color == BLACK &&
+			         GetColor(sibling.right) == RED &&
+			         GetColor(sibling.left) == BLACK)
+			{
+				sibling.color = RED;
+				sibling.right.color = BLACK;
+				RotateLeft(sibling);
+			}
+			sibling = Sibling(node, parentNode); // update value of sibling after rotation
+			
+			sibling.color = parentNode.color;
+			parentNode.color = BLACK;
+			if (node == parentNode.left) {
+				if (sibling.right != null) {
+					Debug.Assert(sibling.right.color == RED);
+					sibling.right.color = BLACK;
+				}
+				RotateLeft(parentNode);
+			} else {
+				if (sibling.left != null) {
+					Debug.Assert(sibling.left.color == RED);
+					sibling.left.color = BLACK;
+				}
+				RotateRight(parentNode);
+			}
+		}
+		
+		void ReplaceNode(TextSegment replacedNode, TextSegment newNode)
+		{
+			if (replacedNode.parent == null) {
+				Debug.Assert(replacedNode == root);
+				root = newNode;
+			} else {
+				if (replacedNode.parent.left == replacedNode)
+					replacedNode.parent.left = newNode;
+				else
+					replacedNode.parent.right = newNode;
+			}
+			if (newNode != null) {
+				newNode.parent = replacedNode.parent;
+			}
+			replacedNode.parent = null;
+		}
+		
+		void RotateLeft(TextSegment p)
+		{
+			// let q be p's right child
+			TextSegment q = p.right;
+			Debug.Assert(q != null);
+			Debug.Assert(q.parent == p);
+			// set q to be the new root
+			ReplaceNode(p, q);
+			
+			// set p's right child to be q's left child
+			p.right = q.left;
+			if (p.right != null) p.right.parent = p;
+			// set q's left child to be p
+			q.left = p;
+			p.parent = q;
+			UpdateAugmentedData(p);
+			UpdateAugmentedData(q);
+		}
+		
+		void RotateRight(TextSegment p)
+		{
+			// let q be p's left child
+			TextSegment q = p.left;
+			Debug.Assert(q != null);
+			Debug.Assert(q.parent == p);
+			// set q to be the new root
+			ReplaceNode(p, q);
+			
+			// set p's left child to be q's right child
+			p.left = q.right;
+			if (p.left != null) p.left.parent = p;
+			// set q's right child to be p
+			q.right = p;
+			p.parent = q;
+			UpdateAugmentedData(p);
+			UpdateAugmentedData(q);
+		}
+		
+		static TextSegment Sibling(TextSegment node)
+		{
+			if (node == node.parent.left)
+				return node.parent.right;
+			else
+				return node.parent.left;
+		}
+		
+		static TextSegment Sibling(TextSegment node, TextSegment parentNode)
+		{
+			Debug.Assert(node == null || node.parent == parentNode);
+			if (node == parentNode.left)
+				return parentNode.right;
+			else
+				return parentNode.left;
+		}
+		
+		static bool GetColor(TextSegment node)
+		{
+			return node != null ? node.color : BLACK;
+		}
+		#endregion
+		
+		#region ICollection<T> implementation
+		/// <summary>
+		/// Gets the number of segments in the tree.
+		/// </summary>
+		public int Count {
+			get { return count; }
+		}
+		
+		bool ICollection<T>.IsReadOnly {
+			get { return false; }
+		}
+		
+		/// <summary>
+		/// Gets whether this tree contains the specified item.
+		/// </summary>
+		public bool Contains(T item)
+		{
+			return item != null && item.ownerTree == this;
+		}
+		
+		/// <summary>
+		/// Copies all segments in this SegmentTree to the specified array.
+		/// </summary>
+		public void CopyTo(T[] array, int arrayIndex)
+		{
+			if (array == null)
+				throw new ArgumentNullException("array");
+			if (array.Length < this.Count)
+				throw new ArgumentException("The array is too small", "array");
+			if (arrayIndex < 0 || arrayIndex + count > array.Length)
+				throw new ArgumentOutOfRangeException("arrayIndex", arrayIndex, "Value must be between 0 and " + (array.Length - count));
+			foreach (T s in this) {
+				array[arrayIndex++] = s;
+			}
+		}
+		
+		/// <summary>
+		/// Gets an enumerator to enumerate the segments.
+		/// </summary>
+		public IEnumerator<T> GetEnumerator()
+		{
+			if (root != null) {
+				TextSegment current = root.LeftMost;
+				while (current != null) {
+					yield return (T)current;
+					// TODO: check if collection was modified during enumeration
+					current = current.Successor;
+				}
+			}
+		}
+		
+		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
+		{
+			return this.GetEnumerator();
+		}
+		#endregion
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextUtilities.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextUtilities.cs
new file mode 100644
index 000000000..a0428c4e3
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/TextUtilities.cs
@@ -0,0 +1,332 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Globalization;
+using System.Windows.Documents;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Specifies the mode for getting the next caret position.
+	/// </summary>
+	public enum CaretPositioningMode
+	{
+		/// <summary>
+		/// Normal positioning (stop at every caret position)
+		/// </summary>
+		Normal,
+		/// <summary>
+		/// Stop only on word borders.
+		/// </summary>
+		WordBorder,
+		/// <summary>
+		/// Stop only at the beginning of words. This is used for Ctrl+Left/Ctrl+Right.
+		/// </summary>
+		WordStart,
+		/// <summary>
+		/// Stop only at the beginning of words, and anywhere in the middle of symbols.
+		/// </summary>
+		WordStartOrSymbol,
+		/// <summary>
+		/// Stop only on word borders, and anywhere in the middle of symbols.
+		/// </summary>
+		WordBorderOrSymbol
+	}
+	
+	/// <summary>
+	/// Static helper methods for working with text.
+	/// </summary>
+	public static partial class TextUtilities
+	{
+		#region GetControlCharacterName
+		// the names of the first 32 ASCII characters = Unicode C0 block
+		static readonly string[] c0Table = {
+			"NUL", "SOH", "STX", "ETX", "EOT", "ENQ", "ACK", "BEL", "BS", "HT",
+			"LF", "VT", "FF", "CR", "SO", "SI", "DLE", "DC1", "DC2", "DC3",
+			"DC4", "NAK", "SYN", "ETB", "CAN", "EM", "SUB", "ESC", "FS", "GS",
+			"RS", "US"
+		};
+		
+		// DEL (ASCII 127) and
+		// the names of the control characters in the C1 block (Unicode 128 to 159)
+		static readonly string[] delAndC1Table = {
+			"DEL",
+			"PAD", "HOP", "BPH", "NBH", "IND", "NEL", "SSA", "ESA", "HTS", "HTJ",
+			"VTS", "PLD", "PLU", "RI", "SS2", "SS3", "DCS", "PU1", "PU2", "STS",
+			"CCH", "MW", "SPA", "EPA", "SOS", "SGCI", "SCI", "CSI", "ST", "OSC",
+			"PM", "APC"
+		};
+		
+		/// <summary>
+		/// Gets the name of the control character.
+		/// For unknown characters, the unicode codepoint is returned as 4-digit hexadecimal value.
+		/// </summary>
+		public static string GetControlCharacterName(char controlCharacter)
+		{
+			int num = (int)controlCharacter;
+			if (num < c0Table.Length)
+				return c0Table[num];
+			else if (num >= 127 && num <= 159)
+				return delAndC1Table[num - 127];
+			else
+				return num.ToString("x4", CultureInfo.InvariantCulture);
+		}
+		#endregion
+		
+		#region GetWhitespace
+		/// <summary>
+		/// Gets all whitespace (' ' and '\t', but no newlines) after offset.
+		/// </summary>
+		/// <param name="textSource">The text source.</param>
+		/// <param name="offset">The offset where the whitespace starts.</param>
+		/// <returns>The segment containing the whitespace.</returns>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
+		                                                 Justification = "WPF uses 'Whitespace'")]
+		public static ISegment GetWhitespaceAfter(ITextSource textSource, int offset)
+		{
+			if (textSource == null)
+				throw new ArgumentNullException("textSource");
+			int pos;
+			for (pos = offset; pos < textSource.TextLength; pos++) {
+				char c = textSource.GetCharAt(pos);
+				if (c != ' ' && c != '\t')
+					break;
+			}
+			return new SimpleSegment(offset, pos - offset);
+		}
+		
+		/// <summary>
+		/// Gets all whitespace (' ' and '\t', but no newlines) before offset.
+		/// </summary>
+		/// <param name="textSource">The text source.</param>
+		/// <param name="offset">The offset where the whitespace ends.</param>
+		/// <returns>The segment containing the whitespace.</returns>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
+		                                                 Justification = "WPF uses 'Whitespace'")]
+		public static ISegment GetWhitespaceBefore(ITextSource textSource, int offset)
+		{
+			if (textSource == null)
+				throw new ArgumentNullException("textSource");
+			int pos;
+			for (pos = offset - 1; pos >= 0; pos--) {
+				char c = textSource.GetCharAt(pos);
+				if (c != ' ' && c != '\t')
+					break;
+			}
+			pos++; // go back the one character that isn't whitespace
+			return new SimpleSegment(pos, offset - pos);
+		}
+		
+		/// <summary>
+		/// Gets the leading whitespace segment on the document line.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
+		                                                 Justification = "WPF uses 'Whitespace'")]
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters",
+		                                                 Justification = "Parameter cannot be ITextSource because it must belong to the DocumentLine")]
+		public static ISegment GetLeadingWhitespace(TextDocument document, DocumentLine documentLine)
+		{
+			if (documentLine == null)
+				throw new ArgumentNullException("documentLine");
+			return GetWhitespaceAfter(document, documentLine.Offset);
+		}
+		
+		/// <summary>
+		/// Gets the trailing whitespace segment on the document line.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
+		                                                 Justification = "WPF uses 'Whitespace'")]
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1011:ConsiderPassingBaseTypesAsParameters",
+		                                                 Justification = "Parameter cannot be ITextSource because it must belong to the DocumentLine")]
+		public static ISegment GetTrailingWhitespace(TextDocument document, DocumentLine documentLine)
+		{
+			if (documentLine == null)
+				throw new ArgumentNullException("documentLine");
+			ISegment segment = GetWhitespaceBefore(document, documentLine.EndOffset);
+			// If the whole line consists of whitespace, we consider all of it as leading whitespace,
+			// so return an empty segment as trailing whitespace.
+			if (segment.Offset == documentLine.Offset)
+				return new SimpleSegment(documentLine.EndOffset, 0);
+			else
+				return segment;
+		}
+		#endregion
+		
+		#region GetSingleIndentationSegment
+		/// <summary>
+		/// Gets a single indentation segment starting at <paramref name="offset"/> - at most one tab
+		/// or <paramref name="indentationSize"/> spaces.
+		/// </summary>
+		/// <param name="textSource">The text source.</param>
+		/// <param name="offset">The offset where the indentation segment starts.</param>
+		/// <param name="indentationSize">The size of an indentation unit. See <see cref="TextEditorOptions.IndentationSize"/>.</param>
+		/// <returns>The indentation segment.
+		/// If there is no indentation character at the specified <paramref name="offset"/>,
+		/// an empty segment is returned.</returns>
+		public static ISegment GetSingleIndentationSegment(ITextSource textSource, int offset, int indentationSize)
+		{
+			if (textSource == null)
+				throw new ArgumentNullException("textSource");
+			int pos = offset;
+			while (pos < textSource.TextLength) {
+				char c = textSource.GetCharAt(pos);
+				if (c == '\t') {
+					if (pos == offset)
+						return new SimpleSegment(offset, 1);
+					else
+						break;
+				} else if (c == ' ') {
+					if (pos - offset >= indentationSize)
+						break;
+				} else {
+					break;
+				}
+				// continue only if c==' ' and (pos-offset)<tabSize
+				pos++;
+			}
+			return new SimpleSegment(offset, pos - offset);
+		}
+		#endregion
+		
+		#region GetCharacterClass
+		/// <summary>
+		/// Gets whether the character is whitespace, part of an identifier, or line terminator.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "c")]
+		public static CharacterClass GetCharacterClass(char c)
+		{
+			if (c == '\r' || c == '\n')
+				return CharacterClass.LineTerminator;
+			else if (char.IsWhiteSpace(c))
+				return CharacterClass.Whitespace;
+			else if (char.IsLetterOrDigit(c) || c == '_')
+				return CharacterClass.IdentifierPart;
+			else
+				return CharacterClass.Other;
+		}
+		#endregion
+		
+		#region GetNextCaretPosition
+		/// <summary>
+		/// Gets the next caret position.
+		/// </summary>
+		/// <param name="textSource">The text source.</param>
+		/// <param name="offset">The start offset inside the text source.</param>
+		/// <param name="direction">The search direction (forwards or backwards).</param>
+		/// <param name="mode">The mode for caret positioning.</param>
+		/// <returns>The offset of the next caret position, or -1 if there is no further caret position
+		/// in the text source.</returns>
+		/// <remarks>
+		/// This method is NOT equivalent to the actual caret movement when using VisualLine.GetNextCaretPosition.
+		/// In real caret movement, there are additional caret stops at line starts and ends. This method
+		/// treats linefeeds as simple whitespace.
+		/// </remarks>
+		public static int GetNextCaretPosition(ITextSource textSource, int offset, LogicalDirection direction, CaretPositioningMode mode)
+		{
+			if (textSource == null)
+				throw new ArgumentNullException("textSource");
+			if (mode != CaretPositioningMode.Normal
+			    && mode != CaretPositioningMode.WordBorder
+			    && mode != CaretPositioningMode.WordStart
+			    && mode != CaretPositioningMode.WordBorderOrSymbol
+			    && mode != CaretPositioningMode.WordStartOrSymbol)
+			{
+				throw new ArgumentException("Unsupported CaretPositioningMode: " + mode, "mode");
+			}
+			if (direction != LogicalDirection.Backward
+			    && direction != LogicalDirection.Forward)
+			{
+				throw new ArgumentException("Invalid LogicalDirection: " + direction, "direction");
+			}
+			int textLength = textSource.TextLength;
+			if (textLength <= 0) {
+				// empty document? has a normal caret position at 0, though no word borders
+				if (mode == CaretPositioningMode.Normal) {
+					if (offset > 0 && direction == LogicalDirection.Backward) return 0;
+					if (offset < 0 && direction == LogicalDirection.Forward) return 0;
+				}
+				return -1;
+			}
+			while (true) {
+				int nextPos = (direction == LogicalDirection.Backward) ? offset - 1 : offset + 1;
+				
+				// return -1 if there is no further caret position in the text source
+				// we also need this to handle offset values outside the valid range
+				if (nextPos < 0 || nextPos > textLength)
+					return -1;
+				
+				// stop at every caret position? we can stop immediately.
+				if (mode == CaretPositioningMode.Normal)
+					return nextPos;
+				// not normal mode? we're looking for word borders...
+				
+				// check if we've run against the textSource borders.
+				// a 'textSource' usually isn't the whole document, but a single VisualLineElement.
+				if (nextPos == 0) {
+					// at the document start, there's only a word border
+					// if the first character is not whitespace
+					if (!char.IsWhiteSpace(textSource.GetCharAt(0)))
+						return nextPos;
+				} else if (nextPos == textLength) {
+					// at the document end, there's never a word start
+					if (mode != CaretPositioningMode.WordStart && mode != CaretPositioningMode.WordStartOrSymbol) {
+						// at the document end, there's only a word border
+						// if the last character is not whitespace
+						if (!char.IsWhiteSpace(textSource.GetCharAt(textLength - 1)))
+							return nextPos;
+					}
+				} else {
+					CharacterClass charBefore = GetCharacterClass(textSource.GetCharAt(nextPos - 1));
+					CharacterClass charAfter = GetCharacterClass(textSource.GetCharAt(nextPos));
+					if (charBefore == charAfter) {
+						if (charBefore == CharacterClass.Other &&
+						    (mode == CaretPositioningMode.WordBorderOrSymbol || mode == CaretPositioningMode.WordStartOrSymbol))
+						{
+							// With the "OrSymbol" modes, there's a word border and start between any two unknown characters
+							return nextPos;
+						}
+					} else {
+						// this looks like a possible border
+						
+						// if we're looking for word starts, check that this is a word start (and not a word end)
+						// if we're just checking for word borders, accept unconditionally
+						if (!((mode == CaretPositioningMode.WordStart || mode == CaretPositioningMode.WordStartOrSymbol)
+						      && (charAfter == CharacterClass.Whitespace || charAfter == CharacterClass.LineTerminator)))
+						{
+							return nextPos;
+						}
+					}
+				}
+				// we'll have to continue searching...
+				offset = nextPos;
+			}
+		}
+		#endregion
+	}
+	
+	/// <summary>
+	/// Classifies a character as whitespace, line terminator, part of an identifier, or other.
+	/// </summary>
+	public enum CharacterClass
+	{
+		/// <summary>
+		/// The character is not whitespace, line terminator or part of an identifier.
+		/// </summary>
+		Other,
+		/// <summary>
+		/// The character is whitespace (but not line terminator).
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1702:CompoundWordsShouldBeCasedCorrectly", MessageId = "Whitespace",
+		                                                 Justification = "WPF uses 'Whitespace'")]
+		Whitespace,
+		/// <summary>
+		/// The character can be part of an identifier (Letter, digit or underscore).
+		/// </summary>
+		IdentifierPart,
+		/// <summary>
+		/// The character is line terminator (\r or \n).
+		/// </summary>
+		LineTerminator
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/UndoOperationGroup.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/UndoOperationGroup.cs
new file mode 100644
index 000000000..12afe3838
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/UndoOperationGroup.cs
@@ -0,0 +1,61 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Diagnostics;
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// This class stacks the last x operations from the undostack and makes
+	/// one undo/redo operation from it.
+	/// </summary>
+	sealed class UndoOperationGroup : IUndoableOperationWithContext
+	{
+		IUndoableOperation[] undolist;
+		
+		public UndoOperationGroup(Deque<IUndoableOperation> stack, int numops)
+		{
+			if (stack == null)  {
+				throw new ArgumentNullException("stack");
+			}
+			
+			Debug.Assert(numops > 0 , "UndoOperationGroup : numops should be > 0");
+			Debug.Assert(numops <= stack.Count);
+			
+			undolist = new IUndoableOperation[numops];
+			for (int i = 0; i < numops; ++i) {
+				undolist[i] = stack.PopBack();
+			}
+		}
+		
+		public void Undo()
+		{
+			for (int i = 0; i < undolist.Length; ++i) {
+				undolist[i].Undo();
+			}
+		}
+		
+		public void Undo(UndoStack stack)
+		{
+			for (int i = 0; i < undolist.Length; ++i) {
+				stack.RunUndo(undolist[i]);
+			}
+		}
+		
+		public void Redo()
+		{
+			for (int i = undolist.Length - 1; i >= 0; --i) {
+				undolist[i].Redo();
+			}
+		}
+		
+		public void Redo(UndoStack stack)
+		{
+			for (int i = undolist.Length - 1; i >= 0; --i) {
+				stack.RunRedo(undolist[i]);
+			}
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/UndoStack.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/UndoStack.cs
new file mode 100644
index 000000000..f0a759b23
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/UndoStack.cs
@@ -0,0 +1,450 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel;
+using System.Diagnostics;
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Undo stack implementation.
+	/// </summary>
+	[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Naming", "CA1711:IdentifiersShouldNotHaveIncorrectSuffix")]
+	public sealed class UndoStack : INotifyPropertyChanged
+	{
+		/// undo stack is listening for changes
+		internal const int StateListen = 0;
+		/// undo stack is reverting/repeating a set of changes
+		internal const int StatePlayback = 1;
+		// undo stack is reverting/repeating a set of changes and modifies the document to do this
+		internal const int StatePlaybackModifyDocument = 2;
+		/// state is used for checking that noone but the UndoStack performs changes
+		/// during Undo events
+		internal int state = StateListen;
+		
+		Deque<IUndoableOperation> undostack = new Deque<IUndoableOperation>();
+		Deque<IUndoableOperation> redostack = new Deque<IUndoableOperation>();
+		int sizeLimit = int.MaxValue;
+		
+		int undoGroupDepth;
+		int actionCountInUndoGroup;
+		int optionalActionCount;
+		object lastGroupDescriptor;
+		bool allowContinue;
+		
+		#region IsOriginalFile implementation
+		// implements feature request SD2-784 - File still considered dirty after undoing all changes
+		
+		/// <summary>
+		/// Number of times undo must be executed until the original state is reached.
+		/// Negative: number of times redo must be executed until the original state is reached.
+		/// Special case: int.MinValue == original state is unreachable
+		/// </summary>
+		int elementsOnUndoUntilOriginalFile;
+		
+		bool isOriginalFile = true;
+		
+		/// <summary>
+		/// Gets whether the document is currently in its original state (no modifications).
+		/// </summary>
+		public bool IsOriginalFile {
+			get { return isOriginalFile; }
+		}
+		
+		void RecalcIsOriginalFile()
+		{
+			bool newIsOriginalFile = (elementsOnUndoUntilOriginalFile == 0);
+			if (newIsOriginalFile != isOriginalFile) {
+				isOriginalFile = newIsOriginalFile;
+				NotifyPropertyChanged("IsOriginalFile");
+			}
+		}
+		
+		/// <summary>
+		/// Marks the current state as original. Discards any previous "original" markers.
+		/// </summary>
+		public void MarkAsOriginalFile()
+		{
+			elementsOnUndoUntilOriginalFile = 0;
+			RecalcIsOriginalFile();
+		}
+		
+		/// <summary>
+		/// Discards the current "original" marker.
+		/// </summary>
+		public void DiscardOriginalFileMarker()
+		{
+			elementsOnUndoUntilOriginalFile = int.MinValue;
+			RecalcIsOriginalFile();
+		}
+		
+		void FileModified(int newElementsOnUndoStack)
+		{
+			if (elementsOnUndoUntilOriginalFile == int.MinValue)
+				return;
+			
+			elementsOnUndoUntilOriginalFile += newElementsOnUndoStack;
+			if (elementsOnUndoUntilOriginalFile > undostack.Count)
+				elementsOnUndoUntilOriginalFile = int.MinValue;
+			
+			// don't call RecalcIsOriginalFile(): wait until end of undo group
+		}
+		#endregion
+		
+		/// <summary>
+		/// Gets if the undo stack currently accepts changes.
+		/// Is false while an undo action is running.
+		/// </summary>
+		public bool AcceptChanges {
+			get { return state == StateListen; }
+		}
+		
+		/// <summary>
+		/// Gets if there are actions on the undo stack.
+		/// Use the PropertyChanged event to listen to changes of this property.
+		/// </summary>
+		public bool CanUndo {
+			get { return undostack.Count > 0; }
+		}
+		
+		/// <summary>
+		/// Gets if there are actions on the redo stack.
+		/// Use the PropertyChanged event to listen to changes of this property.
+		/// </summary>
+		public bool CanRedo {
+			get { return redostack.Count > 0; }
+		}
+		
+		/// <summary>
+		/// Gets/Sets the limit on the number of items on the undo stack.
+		/// </summary>
+		/// <remarks>The size limit is enforced only on the number of stored top-level undo groups.
+		/// Elements within undo groups do not count towards the size limit.</remarks>
+		public int SizeLimit {
+			get { return sizeLimit; }
+			set {
+				if (value < 0)
+					ThrowUtil.CheckNotNegative(value, "value");
+				if (sizeLimit != value) {
+					sizeLimit = value;
+					NotifyPropertyChanged("SizeLimit");
+					if (undoGroupDepth == 0)
+						EnforceSizeLimit();
+				}
+			}
+		}
+		
+		void EnforceSizeLimit()
+		{
+			Debug.Assert(undoGroupDepth == 0);
+			while (undostack.Count > sizeLimit)
+				undostack.PopFront();
+			while (redostack.Count > sizeLimit)
+				redostack.PopFront();
+		}
+		
+		/// <summary>
+		/// If an undo group is open, gets the group descriptor of the current top-level
+		/// undo group.
+		/// If no undo group is open, gets the group descriptor from the previous undo group.
+		/// </summary>
+		/// <remarks>The group descriptor can be used to join adjacent undo groups:
+		/// use a group descriptor to mark your changes, and on the second action,
+		/// compare LastGroupDescriptor and use <see cref="StartContinuedUndoGroup"/> if you
+		/// want to join the undo groups.</remarks>
+		public object LastGroupDescriptor {
+			get { return lastGroupDescriptor; }
+		}
+		
+		/// <summary>
+		/// Starts grouping changes.
+		/// Maintains a counter so that nested calls are possible.
+		/// </summary>
+		public void StartUndoGroup()
+		{
+			StartUndoGroup(null);
+		}
+		
+		/// <summary>
+		/// Starts grouping changes.
+		/// Maintains a counter so that nested calls are possible.
+		/// </summary>
+		/// <param name="groupDescriptor">An object that is stored with the undo group.
+		/// If this is not a top-level undo group, the parameter is ignored.</param>
+		public void StartUndoGroup(object groupDescriptor)
+		{
+			if (undoGroupDepth == 0) {
+				actionCountInUndoGroup = 0;
+				optionalActionCount = 0;
+				lastGroupDescriptor = groupDescriptor;
+			}
+			undoGroupDepth++;
+			//Util.LoggingService.Debug("Open undo group (new depth=" + undoGroupDepth + ")");
+		}
+		
+		/// <summary>
+		/// Starts grouping changes, continuing with the previously closed undo group if possible.
+		/// Maintains a counter so that nested calls are possible.
+		/// If the call to StartContinuedUndoGroup is a nested call, it behaves exactly
+		/// as <see cref="StartUndoGroup()"/>, only top-level calls can continue existing undo groups.
+		/// </summary>
+		/// <param name="groupDescriptor">An object that is stored with the undo group.
+		/// If this is not a top-level undo group, the parameter is ignored.</param>
+		public void StartContinuedUndoGroup(object groupDescriptor)
+		{
+			if (undoGroupDepth == 0) {
+				actionCountInUndoGroup = (allowContinue && undostack.Count > 0) ? 1 : 0;
+				optionalActionCount = 0;
+				lastGroupDescriptor = groupDescriptor;
+			}
+			undoGroupDepth++;
+			//Util.LoggingService.Debug("Continue undo group (new depth=" + undoGroupDepth + ")");
+		}
+		
+		/// <summary>
+		/// Stops grouping changes.
+		/// </summary>
+		public void EndUndoGroup()
+		{
+			if (undoGroupDepth == 0) return;
+			undoGroupDepth--;
+			//Util.LoggingService.Debug("Close undo group (new depth=" + undoGroupDepth + ")");
+			if (undoGroupDepth == 0) {
+				Debug.Assert(state == StateListen || actionCountInUndoGroup == 0);
+				if (actionCountInUndoGroup == optionalActionCount) {
+					// only optional actions: don't store them
+					for (int i = 0; i < optionalActionCount; i++) {
+						undostack.PopBack();
+					}
+				} else if (actionCountInUndoGroup > 1) {
+					// combine all actions within the group into a single grouped action
+					undostack.PushBack(new UndoOperationGroup(undostack, actionCountInUndoGroup));
+					FileModified(-actionCountInUndoGroup + 1 + optionalActionCount);
+				}
+				//if (state == StateListen) {
+				EnforceSizeLimit();
+				allowContinue = true;
+				RecalcIsOriginalFile(); // can raise event
+				//}
+			}
+		}
+		
+		/// <summary>
+		/// Throws an InvalidOperationException if an undo group is current open.
+		/// </summary>
+		void ThrowIfUndoGroupOpen()
+		{
+            try
+            {
+                if (undoGroupDepth != 0)
+                {
+                    undoGroupDepth = 0;
+                    throw new InvalidOperationException("No undo group should be open at this point");
+                }
+                if (state != StateListen)
+                {
+                    throw new InvalidOperationException("This method cannot be called while an undo operation is being performed");
+                }
+            }
+            catch
+            {
+            }
+		}
+		
+		List<TextDocument> affectedDocuments;
+		
+		internal void RegisterAffectedDocument(TextDocument document)
+		{
+			if (affectedDocuments == null)
+				affectedDocuments = new List<TextDocument>();
+			if (!affectedDocuments.Contains(document)) {
+				affectedDocuments.Add(document);
+				document.BeginUpdate();
+			}
+		}
+		
+		void CallEndUpdateOnAffectedDocuments()
+		{
+			if (affectedDocuments != null) {
+				foreach (TextDocument doc in affectedDocuments) {
+					doc.EndUpdate();
+				}
+				affectedDocuments = null;
+			}
+		}
+		
+		/// <summary>
+		/// Call this method to undo the last operation on the stack
+		/// </summary>
+		public void Undo()
+		{
+			ThrowIfUndoGroupOpen();
+			if (undostack.Count > 0) {
+				// disallow continuing undo groups after undo operation
+				lastGroupDescriptor = null; allowContinue = false;
+				// fetch operation to undo and move it to redo stack
+				IUndoableOperation uedit = undostack.PopBack();
+				redostack.PushBack(uedit);
+				state = StatePlayback;
+				try {
+					RunUndo(uedit);
+				} finally {
+					state = StateListen;
+					FileModified(-1);
+					CallEndUpdateOnAffectedDocuments();
+				}
+				RecalcIsOriginalFile();
+				if (undostack.Count == 0)
+					NotifyPropertyChanged("CanUndo");
+				if (redostack.Count == 1)
+					NotifyPropertyChanged("CanRedo");
+			}
+		}
+		
+		internal void RunUndo(IUndoableOperation op)
+		{
+			IUndoableOperationWithContext opWithCtx = op as IUndoableOperationWithContext;
+			if (opWithCtx != null)
+				opWithCtx.Undo(this);
+			else
+				op.Undo();
+		}
+		
+		/// <summary>
+		/// Call this method to redo the last undone operation
+		/// </summary>
+		public void Redo()
+		{
+			ThrowIfUndoGroupOpen();
+			if (redostack.Count > 0) {
+				lastGroupDescriptor = null; allowContinue = false;
+				IUndoableOperation uedit = redostack.PopBack();
+				undostack.PushBack(uedit);
+				state = StatePlayback;
+				try {
+					RunRedo(uedit);
+				} finally {
+					state = StateListen;
+					FileModified(1);
+					CallEndUpdateOnAffectedDocuments();
+				}
+				RecalcIsOriginalFile();
+				if (redostack.Count == 0)
+					NotifyPropertyChanged("CanRedo");
+				if (undostack.Count == 1)
+					NotifyPropertyChanged("CanUndo");
+			}
+		}
+		
+		internal void RunRedo(IUndoableOperation op)
+		{
+			IUndoableOperationWithContext opWithCtx = op as IUndoableOperationWithContext;
+			if (opWithCtx != null)
+				opWithCtx.Redo(this);
+			else
+				op.Redo();
+		}
+		
+		/// <summary>
+		/// Call this method to push an UndoableOperation on the undostack.
+		/// The redostack will be cleared if you use this method.
+		/// </summary>
+		public void Push(IUndoableOperation operation)
+		{
+			Push(operation, false);
+		}
+		
+		/// <summary>
+		/// Call this method to push an UndoableOperation on the undostack.
+		/// However, the operation will be only stored if the undo group contains a
+		/// non-optional operation.
+		/// Use this method to store the caret position/selection on the undo stack to
+		/// prevent having only actions that affect only the caret and not the document.
+		/// </summary>
+		public void PushOptional(IUndoableOperation operation)
+		{
+			if (undoGroupDepth == 0)
+				throw new InvalidOperationException("Cannot use PushOptional outside of undo group");
+			Push(operation, true);
+		}
+		
+		void Push(IUndoableOperation operation, bool isOptional)
+		{
+			if (operation == null) {
+				throw new ArgumentNullException("operation");
+			}
+			
+			if (state == StateListen && sizeLimit > 0) {
+				bool wasEmpty = undostack.Count == 0;
+				
+				bool needsUndoGroup = undoGroupDepth == 0;
+				if (needsUndoGroup) StartUndoGroup();
+				undostack.PushBack(operation);
+				actionCountInUndoGroup++;
+				if (isOptional)
+					optionalActionCount++;
+				else
+					FileModified(1);
+				if (needsUndoGroup) EndUndoGroup();
+				if (wasEmpty)
+					NotifyPropertyChanged("CanUndo");
+				ClearRedoStack();
+			}
+		}
+		
+		/// <summary>
+		/// Call this method, if you want to clear the redo stack
+		/// </summary>
+		public void ClearRedoStack()
+		{
+			if (redostack.Count != 0) {
+				redostack.Clear();
+				NotifyPropertyChanged("CanRedo");
+				// if the "original file" marker is on the redo stack: remove it
+				if (elementsOnUndoUntilOriginalFile < 0)
+					elementsOnUndoUntilOriginalFile = int.MinValue;
+			}
+		}
+		
+		/// <summary>
+		/// Clears both the undo and redo stack.
+		/// </summary>
+		public void ClearAll()
+		{
+			ThrowIfUndoGroupOpen();
+			actionCountInUndoGroup = 0;
+			optionalActionCount = 0;
+			if (undostack.Count != 0) {
+				lastGroupDescriptor = null;
+				allowContinue = false;
+				undostack.Clear();
+				NotifyPropertyChanged("CanUndo");
+			}
+			ClearRedoStack();
+		}
+		
+		internal void Push(TextDocument document, DocumentChangeEventArgs e)
+		{
+			if (state == StatePlayback)
+				throw new InvalidOperationException("Document changes during undo/redo operations are not allowed.");
+			if (state == StatePlaybackModifyDocument)
+				state = StatePlayback; // allow only 1 change per expected modification
+			else
+				Push(new DocumentChangeOperation(document, e));
+		}
+		
+		/// <summary>
+		/// Is raised when a property (CanUndo, CanRedo) changed.
+		/// </summary>
+		public event PropertyChangedEventHandler PropertyChanged;
+		
+		void NotifyPropertyChanged(string propertyName)
+		{
+			if (PropertyChanged != null)
+				PropertyChanged(this, new PropertyChangedEventArgs(propertyName));
+		}
+	}
+}
diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/WeakLineTracker.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/WeakLineTracker.cs
new file mode 100644
index 000000000..a70874645
--- /dev/null
+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/WeakLineTracker.cs
@@ -0,0 +1,85 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+
+namespace Tango.Scripting.Editors.Document
+{
+	/// <summary>
+	/// Allows registering a line tracker on a TextDocument using a weak reference from the document to the line tracker.
+	/// </summary>
+	public sealed class WeakLineTracker : ILineTracker
+	{
+		TextDocument textDocument;
+		WeakReference targetObject;
+		
+		private WeakLineTracker(TextDocument textDocument, ILineTracker targetTracker)
+		{
+			this.textDocument = textDocument;
+			this.targetObject = new WeakReference(targetTracker);
+		}
+		
+		/// <summary>
+		/// Registers the <paramref name="targetTracker"/> as line tracker for the <paramref name="textDocument"/>.
+		/// A weak reference to the target tracker will be used, and the WeakLineTracker will deregister itself
+		/// when the target tracker is garbage collected.
+		/// </summary>
+		public static WeakLineTracker Register(TextDocument textDocument, ILineTracker targetTracker)
+		{
+			if (textDocument == null)
+				throw new ArgumentNullException("textDocument");
+			if (targetTracker == null)
+				throw new ArgumentNullException("targetTracker");
+			WeakLineTracker wlt = new WeakLineTracker(textDocument, targetTracker);
+			textDocument.LineTrackers.Add(wlt);
+			return wlt;
+		}
+		
+		/// <summary>
+		/// Deregisters the weak line tracker.
+		/// </summary>
+		public void Deregister()
+		{
+			if (textDocument != null) {
+				textDocument.LineTrackers.Remove(this);
+				textDocument = null;
+			}
+		}
+		
+		void ILineTracker.BeforeRemoveLine(DocumentLine line)
+		{
+			ILineTracker targetTracker = targetObject.Target as ILineTracker;
+			if (targetTracker != null)
+				targetTracker.BeforeRemoveLine(line);
+			else
+				Deregister();
+		}
+		
+		void ILineTracker.SetLineLength(DocumentLine line, int newTotalLength)
+		{
+			ILineTracker targetTracker = targetObject.Target as ILineTracker;
+			if (targetTracker != null)
+				targetTracker.SetLineLength(line, newTotalLength);
+			else
+				Deregister();
+		}
+		
+		void ILineTracker.LineInserted(DocumentLine insertionPos, DocumentLine newLine)
+		{
+			ILineTracker targetTracker = targetObject.Target as ILineTracker;
+			if (targetTracker != null)
+				targetTracker.LineInserted(insertionPos, newLine);
+			else
+				Deregister();
+		}
+		
+		void ILineTracker.RebuildDocument()
+		{
+			ILineTracker targetTracker = targetObject.Target as ILineTracker;
+			if (targetTracker != null)
+				targetTracker.RebuildDocument();
+			else
+				Deregister();
+		}
+	}
+}