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diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/OffsetChangeMap.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Document/OffsetChangeMap.cs
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+// 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);
+		}
+	}
+}