MERGE

1 files changed, 2009 insertions, 0 deletions

diff --git a/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Rendering/TextView.cs b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Rendering/TextView.cs
new file mode 100644
index 000000000..3dabb6b7a
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+++ b/Software/Visual_Studio/Scripting/Tango.Scripting.Editors/Rendering/TextView.cs
@@ -0,0 +1,2009 @@
+// 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.ComponentModel.Design;
+using System.Diagnostics;
+using System.Globalization;
+using System.Linq;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Controls.Primitives;
+using System.Windows.Input;
+using System.Windows.Media;
+using System.Windows.Media.TextFormatting;
+using System.Windows.Threading;
+using Tango.Scripting.Editors.Document;
+using Tango.Scripting.Editors.Editing;
+using Tango.Scripting.Editors.Utils;
+
+namespace Tango.Scripting.Editors.Rendering
+{
+	/// <summary>
+	/// A virtualizing panel producing+showing <see cref="VisualLine"/>s for a <see cref="TextDocument"/>.
+	/// 
+	/// This is the heart of the text editor, this class controls the text rendering process.
+	/// 
+	/// Taken as a standalone control, it's a text viewer without any editing capability.
+	/// </summary>
+	[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1001:TypesThatOwnDisposableFieldsShouldBeDisposable",
+	                                                 Justification = "The user usually doesn't work with TextView but with TextEditor; and nulling the Document property is sufficient to dispose everything.")]
+	public class TextView : FrameworkElement, IScrollInfo, IWeakEventListener, ITextEditorComponent, IServiceProvider
+	{
+		#region Constructor
+		static TextView()
+		{
+			ClipToBoundsProperty.OverrideMetadata(typeof(TextView), new FrameworkPropertyMetadata(Boxes.True));
+			FocusableProperty.OverrideMetadata(typeof(TextView), new FrameworkPropertyMetadata(Boxes.False));
+		}
+		
+		ColumnRulerRenderer columnRulerRenderer;
+		
+		/// <summary>
+		/// Creates a new TextView instance.
+		/// </summary>
+		public TextView()
+		{
+			services.AddService(typeof(TextView), this);
+			textLayer = new TextLayer(this);
+			elementGenerators = new ObserveAddRemoveCollection<VisualLineElementGenerator>(ElementGenerator_Added, ElementGenerator_Removed);
+			lineTransformers = new ObserveAddRemoveCollection<IVisualLineTransformer>(LineTransformer_Added, LineTransformer_Removed);
+			backgroundRenderers = new ObserveAddRemoveCollection<IBackgroundRenderer>(BackgroundRenderer_Added, BackgroundRenderer_Removed);
+			columnRulerRenderer = new ColumnRulerRenderer(this);
+			this.Options = new TextEditorOptions();
+			
+			Debug.Assert(singleCharacterElementGenerator != null); // assert that the option change created the builtin element generators
+			
+			layers = new LayerCollection(this);
+			InsertLayer(textLayer, KnownLayer.Text, LayerInsertionPosition.Replace);
+			
+			this.hoverLogic = new MouseHoverLogic(this);
+			this.hoverLogic.MouseHover += (sender, e) => RaiseHoverEventPair(e, PreviewMouseHoverEvent, MouseHoverEvent);
+			this.hoverLogic.MouseHoverStopped += (sender, e) => RaiseHoverEventPair(e, PreviewMouseHoverStoppedEvent, MouseHoverStoppedEvent);
+		}
+
+		#endregion
+		
+		#region Document Property
+		/// <summary>
+		/// Document property.
+		/// </summary>
+		public static readonly DependencyProperty DocumentProperty =
+			DependencyProperty.Register("Document", typeof(TextDocument), typeof(TextView),
+			                            new FrameworkPropertyMetadata(OnDocumentChanged));
+		
+		TextDocument document;
+		HeightTree heightTree;
+		
+		/// <summary>
+		/// Gets/Sets the document displayed by the text editor.
+		/// </summary>
+		public TextDocument Document {
+			get { return (TextDocument)GetValue(DocumentProperty); }
+			set { SetValue(DocumentProperty, value); }
+		}
+		
+		static void OnDocumentChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
+		{
+			((TextView)dp).OnDocumentChanged((TextDocument)e.OldValue, (TextDocument)e.NewValue);
+		}
+		
+		internal double FontSize {
+			get {
+				return (double)GetValue(TextBlock.FontSizeProperty);
+			}
+		}
+		
+		/// <summary>
+		/// Occurs when the document property has changed.
+		/// </summary>
+		public event EventHandler DocumentChanged;
+		
+		void OnDocumentChanged(TextDocument oldValue, TextDocument newValue)
+		{
+			if (oldValue != null) {
+				heightTree.Dispose();
+				heightTree = null;
+				formatter.Dispose();
+				formatter = null;
+				cachedElements.Dispose();
+				cachedElements = null;
+				TextDocumentWeakEventManager.Changing.RemoveListener(oldValue, this);
+			}
+			this.document = newValue;
+			ClearScrollData();
+			ClearVisualLines();
+			if (newValue != null) {
+				TextDocumentWeakEventManager.Changing.AddListener(newValue, this);
+				formatter = TextFormatterFactory.Create(this);
+				InvalidateDefaultTextMetrics(); // measuring DefaultLineHeight depends on formatter
+				heightTree = new HeightTree(newValue, DefaultLineHeight);
+				cachedElements = new TextViewCachedElements();
+			}
+			InvalidateMeasure(DispatcherPriority.Normal);
+			if (DocumentChanged != null)
+				DocumentChanged(this, EventArgs.Empty);
+		}
+		
+		/// <summary>
+		/// Recreates the text formatter that is used internally
+		/// by calling <see cref="TextFormatterFactory.Create"/>.
+		/// </summary>
+		void RecreateTextFormatter()
+		{
+			if (formatter != null) {
+				formatter.Dispose();
+				formatter = TextFormatterFactory.Create(this);
+				Redraw();
+			}
+		}
+		
+		void RecreateCachedElements()
+		{
+			if (cachedElements != null) {
+				cachedElements.Dispose();
+				cachedElements = new TextViewCachedElements();
+			}
+		}
+		
+		/// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
+		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+		{
+			if (managerType == typeof(TextDocumentWeakEventManager.Changing)) {
+				// TODO: put redraw into background so that other input events can be handled before the redraw.
+				// Unfortunately the "easy" approach (just use DispatcherPriority.Background) here makes the editor twice as slow because
+				// the caret position change forces an immediate redraw, and the text input then forces a background redraw.
+				// When fixing this, make sure performance on the SharpDevelop "type text in C# comment" stress test doesn't get significantly worse.
+				DocumentChangeEventArgs change = (DocumentChangeEventArgs)e;
+				Redraw(change.Offset, change.RemovalLength, DispatcherPriority.Normal);
+				return true;
+			} else if (managerType == typeof(PropertyChangedWeakEventManager)) {
+				OnOptionChanged((PropertyChangedEventArgs)e);
+				return true;
+			}
+			return false;
+		}
+		
+		bool IWeakEventListener.ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+		{
+			return ReceiveWeakEvent(managerType, sender, e);
+		}
+		#endregion
+		
+		#region Options property
+		/// <summary>
+		/// Options property.
+		/// </summary>
+		public static readonly DependencyProperty OptionsProperty =
+			DependencyProperty.Register("Options", typeof(TextEditorOptions), typeof(TextView),
+			                            new FrameworkPropertyMetadata(OnOptionsChanged));
+		
+		/// <summary>
+		/// Gets/Sets the options used by the text editor.
+		/// </summary>
+		public TextEditorOptions Options {
+			get { return (TextEditorOptions)GetValue(OptionsProperty); }
+			set { SetValue(OptionsProperty, value); }
+		}
+		
+		/// <summary>
+		/// Occurs when a text editor option has changed.
+		/// </summary>
+		public event PropertyChangedEventHandler OptionChanged;
+		
+		/// <summary>
+		/// Raises the <see cref="OptionChanged"/> event.
+		/// </summary>
+		protected virtual void OnOptionChanged(PropertyChangedEventArgs e)
+		{
+			if (OptionChanged != null) {
+				OptionChanged(this, e);
+			}
+			
+			if (Options.ShowColumnRuler)
+				columnRulerRenderer.SetRuler(Options.ColumnRulerPosition, ColumnRulerPen);
+			else
+				columnRulerRenderer.SetRuler(-1, ColumnRulerPen);
+			
+			UpdateBuiltinElementGeneratorsFromOptions();
+			Redraw();
+		}
+		
+		static void OnOptionsChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
+		{
+			((TextView)dp).OnOptionsChanged((TextEditorOptions)e.OldValue, (TextEditorOptions)e.NewValue);
+		}
+		
+		void OnOptionsChanged(TextEditorOptions oldValue, TextEditorOptions newValue)
+		{
+			if (oldValue != null) {
+				PropertyChangedWeakEventManager.RemoveListener(oldValue, this);
+			}
+			if (newValue != null) {
+				PropertyChangedWeakEventManager.AddListener(newValue, this);
+			}
+			OnOptionChanged(new PropertyChangedEventArgs(null));
+		}
+		#endregion
+		
+		#region ElementGenerators+LineTransformers Properties
+		readonly ObserveAddRemoveCollection<VisualLineElementGenerator> elementGenerators;
+		
+		/// <summary>
+		/// Gets a collection where element generators can be registered.
+		/// </summary>
+		public IList<VisualLineElementGenerator> ElementGenerators {
+			get { return elementGenerators; }
+		}
+		
+		void ElementGenerator_Added(VisualLineElementGenerator generator)
+		{
+			ConnectToTextView(generator);
+			Redraw();
+		}
+		
+		void ElementGenerator_Removed(VisualLineElementGenerator generator)
+		{
+			DisconnectFromTextView(generator);
+			Redraw();
+		}
+		
+		readonly ObserveAddRemoveCollection<IVisualLineTransformer> lineTransformers;
+		
+		/// <summary>
+		/// Gets a collection where line transformers can be registered.
+		/// </summary>
+		public IList<IVisualLineTransformer> LineTransformers {
+			get { return lineTransformers; }
+		}
+		
+		void LineTransformer_Added(IVisualLineTransformer lineTransformer)
+		{
+			ConnectToTextView(lineTransformer);
+			Redraw();
+		}
+		
+		void LineTransformer_Removed(IVisualLineTransformer lineTransformer)
+		{
+			DisconnectFromTextView(lineTransformer);
+			Redraw();
+		}
+		#endregion
+		
+		#region Builtin ElementGenerators
+//		NewLineElementGenerator newLineElementGenerator;
+		SingleCharacterElementGenerator singleCharacterElementGenerator;
+		LinkElementGenerator linkElementGenerator;
+		MailLinkElementGenerator mailLinkElementGenerator;
+		
+		void UpdateBuiltinElementGeneratorsFromOptions()
+		{
+			TextEditorOptions options = this.Options;
+			
+//			AddRemoveDefaultElementGeneratorOnDemand(ref newLineElementGenerator, options.ShowEndOfLine);
+			AddRemoveDefaultElementGeneratorOnDemand(ref singleCharacterElementGenerator, options.ShowBoxForControlCharacters || options.ShowSpaces || options.ShowTabs);
+			AddRemoveDefaultElementGeneratorOnDemand(ref linkElementGenerator, options.EnableHyperlinks);
+			AddRemoveDefaultElementGeneratorOnDemand(ref mailLinkElementGenerator, options.EnableEmailHyperlinks);
+		}
+		
+		void AddRemoveDefaultElementGeneratorOnDemand<T>(ref T generator, bool demand)
+			where T : VisualLineElementGenerator, IBuiltinElementGenerator, new()
+		{
+			bool hasGenerator = generator != null;
+			if (hasGenerator != demand) {
+				if (demand) {
+					generator = new T();
+					this.ElementGenerators.Add(generator);
+				} else {
+					this.ElementGenerators.Remove(generator);
+					generator = null;
+				}
+			}
+			if (generator != null)
+				generator.FetchOptions(this.Options);
+		}
+		#endregion
+		
+		#region Layers
+		internal readonly TextLayer textLayer;
+		readonly LayerCollection layers;
+		
+		/// <summary>
+		/// Gets the list of layers displayed in the text view.
+		/// </summary>
+		public UIElementCollection Layers {
+			get { return layers; }
+		}
+		
+		sealed class LayerCollection : UIElementCollection
+		{
+			readonly TextView textView;
+			
+			public LayerCollection(TextView textView)
+				: base(textView, textView)
+			{
+				this.textView = textView;
+			}
+			
+			public override void Clear()
+			{
+				base.Clear();
+				textView.LayersChanged();
+			}
+			
+			public override int Add(UIElement element)
+			{
+				int r = base.Add(element);
+				textView.LayersChanged();
+				return r;
+			}
+			
+			public override void RemoveAt(int index)
+			{
+				base.RemoveAt(index);
+				textView.LayersChanged();
+			}
+			
+			public override void RemoveRange(int index, int count)
+			{
+				base.RemoveRange(index, count);
+				textView.LayersChanged();
+			}
+		}
+		
+		void LayersChanged()
+		{
+			textLayer.index = layers.IndexOf(textLayer);
+		}
+		
+		/// <summary>
+		/// Inserts a new layer at a position specified relative to an existing layer.
+		/// </summary>
+		/// <param name="layer">The new layer to insert.</param>
+		/// <param name="referencedLayer">The existing layer</param>
+		/// <param name="position">Specifies whether the layer is inserted above,below, or replaces the referenced layer</param>
+		public void InsertLayer(UIElement layer, KnownLayer referencedLayer, LayerInsertionPosition position)
+		{
+			if (layer == null)
+				throw new ArgumentNullException("layer");
+			if (!Enum.IsDefined(typeof(KnownLayer), referencedLayer))
+				throw new InvalidEnumArgumentException("referencedLayer", (int)referencedLayer, typeof(KnownLayer));
+			if (!Enum.IsDefined(typeof(LayerInsertionPosition), position))
+				throw new InvalidEnumArgumentException("position", (int)position, typeof(LayerInsertionPosition));
+			if (referencedLayer == KnownLayer.Background && position != LayerInsertionPosition.Above)
+				throw new InvalidOperationException("Cannot replace or insert below the background layer.");
+			
+			LayerPosition newPosition = new LayerPosition(referencedLayer, position);
+			LayerPosition.SetLayerPosition(layer, newPosition);
+			for (int i = 0; i < layers.Count; i++) {
+				LayerPosition p = LayerPosition.GetLayerPosition(layers[i]);
+				if (p != null) {
+					if (p.KnownLayer == referencedLayer && p.Position == LayerInsertionPosition.Replace) {
+						// found the referenced layer
+						switch (position) {
+							case LayerInsertionPosition.Below:
+								layers.Insert(i, layer);
+								return;
+							case LayerInsertionPosition.Above:
+								layers.Insert(i + 1, layer);
+								return;
+							case LayerInsertionPosition.Replace:
+								layers[i] = layer;
+								return;
+						}
+					} else if (p.KnownLayer == referencedLayer && p.Position == LayerInsertionPosition.Above
+					           || p.KnownLayer > referencedLayer) {
+						// we skipped the insertion position (referenced layer does not exist?)
+						layers.Insert(i, layer);
+						return;
+					}
+				}
+			}
+			// inserting after all existing layers:
+			layers.Add(layer);
+		}
+		
+		/// <inheritdoc/>
+		protected override int VisualChildrenCount {
+			get { return layers.Count + inlineObjects.Count; }
+		}
+		
+		/// <inheritdoc/>
+		protected override Visual GetVisualChild(int index)
+		{
+			int cut = textLayer.index + 1;
+			if (index < cut)
+				return layers[index];
+			else if (index < cut + inlineObjects.Count)
+				return inlineObjects[index - cut].Element;
+			else
+				return layers[index - inlineObjects.Count];
+		}
+		
+		/// <inheritdoc/>
+		protected override System.Collections.IEnumerator LogicalChildren {
+			get {
+				return inlineObjects.Select(io => io.Element).Concat(layers.Cast<UIElement>()).GetEnumerator();
+			}
+		}
+		#endregion
+		
+		#region Inline object handling
+		List<InlineObjectRun> inlineObjects = new List<InlineObjectRun>();
+		
+		/// <summary>
+		/// Adds a new inline object.
+		/// </summary>
+		internal void AddInlineObject(InlineObjectRun inlineObject)
+		{
+			Debug.Assert(inlineObject.VisualLine != null);
+			
+			// Remove inline object if its already added, can happen e.g. when recreating textrun for word-wrapping
+			bool alreadyAdded = false;
+			for (int i = 0; i < inlineObjects.Count; i++) {
+				if (inlineObjects[i].Element == inlineObject.Element) {
+					RemoveInlineObjectRun(inlineObjects[i], true);
+					inlineObjects.RemoveAt(i);
+					alreadyAdded = true;
+					break;
+				}
+			}
+			
+			inlineObjects.Add(inlineObject);
+			if (!alreadyAdded) {
+				AddVisualChild(inlineObject.Element);
+			}
+			inlineObject.Element.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
+			inlineObject.desiredSize = inlineObject.Element.DesiredSize;
+		}
+		
+		void MeasureInlineObjects()
+		{
+			// As part of MeasureOverride(), re-measure the inline objects
+			foreach (InlineObjectRun inlineObject in inlineObjects) {
+				if (inlineObject.VisualLine.IsDisposed) {
+					// Don't re-measure inline objects that are going to be removed anyways.
+					// If the inline object will be reused in a different VisualLine, we'll measure it in the AddInlineObject() call.
+					continue;
+				}
+				inlineObject.Element.Measure(new Size(double.PositiveInfinity, double.PositiveInfinity));
+				if (!inlineObject.Element.DesiredSize.IsClose(inlineObject.desiredSize)) {
+					// the element changed size -> recreate its parent visual line
+					inlineObject.desiredSize = inlineObject.Element.DesiredSize;
+					if (allVisualLines.Remove(inlineObject.VisualLine)) {
+						DisposeVisualLine(inlineObject.VisualLine);
+					}
+				}
+			}
+		}
+		
+		List<VisualLine> visualLinesWithOutstandingInlineObjects = new List<VisualLine>();
+		
+		void RemoveInlineObjects(VisualLine visualLine)
+		{
+			// Delay removing inline objects:
+			// A document change immediately invalidates affected visual lines, but it does not
+			// cause an immediate redraw.
+			// To prevent inline objects from flickering when they are recreated, we delay removing
+			// inline objects until the next redraw.
+			if (visualLine.hasInlineObjects) {
+				visualLinesWithOutstandingInlineObjects.Add(visualLine);
+			}
+		}
+		
+		/// <summary>
+		/// Remove the inline objects that were marked for removal.
+		/// </summary>
+		void RemoveInlineObjectsNow()
+		{
+			if (visualLinesWithOutstandingInlineObjects.Count == 0)
+				return;
+			inlineObjects.RemoveAll(
+				ior => {
+					if (visualLinesWithOutstandingInlineObjects.Contains(ior.VisualLine)) {
+						RemoveInlineObjectRun(ior, false);
+						return true;
+					}
+					return false;
+				});
+			visualLinesWithOutstandingInlineObjects.Clear();
+		}
+
+		// Remove InlineObjectRun.Element from TextLayer.
+		// Caller of RemoveInlineObjectRun will remove it from inlineObjects collection.
+		void RemoveInlineObjectRun(InlineObjectRun ior, bool keepElement)
+		{
+			if (!keepElement && ior.Element.IsKeyboardFocusWithin) {
+				// When the inline element that has the focus is removed, WPF will reset the
+				// focus to the main window without raising appropriate LostKeyboardFocus events.
+				// To work around this, we manually set focus to the next focusable parent.
+				UIElement element = this;
+				while (element != null && !element.Focusable) {
+					element = VisualTreeHelper.GetParent(element) as UIElement;
+				}
+				if (element != null)
+					Keyboard.Focus(element);
+			}
+			ior.VisualLine = null;
+			if (!keepElement)
+				RemoveVisualChild(ior.Element);
+		}
+		#endregion
+		
+		#region Brushes
+		/// <summary>
+		/// NonPrintableCharacterBrush dependency property.
+		/// </summary>
+		public static readonly DependencyProperty NonPrintableCharacterBrushProperty =
+			DependencyProperty.Register("NonPrintableCharacterBrush", typeof(Brush), typeof(TextView),
+			                            new FrameworkPropertyMetadata(Brushes.LightGray));
+		
+		/// <summary>
+		/// Gets/sets the Brush used for displaying non-printable characters.
+		/// </summary>
+		public Brush NonPrintableCharacterBrush {
+			get { return (Brush)GetValue(NonPrintableCharacterBrushProperty); }
+			set { SetValue(NonPrintableCharacterBrushProperty, value); }
+		}
+		
+		/// <summary>
+		/// LinkTextForegroundBrush dependency property.
+		/// </summary>
+		public static readonly DependencyProperty LinkTextForegroundBrushProperty =
+			DependencyProperty.Register("LinkTextForegroundBrush", typeof(Brush), typeof(TextView),
+			                            new FrameworkPropertyMetadata(Brushes.Blue));
+		
+		/// <summary>
+		/// Gets/sets the Brush used for displaying link texts.
+		/// </summary>
+		public Brush LinkTextForegroundBrush {
+			get { return (Brush)GetValue(LinkTextForegroundBrushProperty); }
+			set { SetValue(LinkTextForegroundBrushProperty, value); }
+		}
+		
+		/// <summary>
+		/// LinkTextBackgroundBrush dependency property.
+		/// </summary>
+		public static readonly DependencyProperty LinkTextBackgroundBrushProperty =
+			DependencyProperty.Register("LinkTextBackgroundBrush", typeof(Brush), typeof(TextView),
+			                            new FrameworkPropertyMetadata(Brushes.Transparent));
+		
+		/// <summary>
+		/// Gets/sets the Brush used for the background of link texts.
+		/// </summary>
+		public Brush LinkTextBackgroundBrush {
+			get { return (Brush)GetValue(LinkTextBackgroundBrushProperty); }
+			set { SetValue(LinkTextBackgroundBrushProperty, value); }
+		}
+		#endregion
+		
+		#region Redraw methods / VisualLine invalidation
+		/// <summary>
+		/// Causes the text editor to regenerate all visual lines.
+		/// </summary>
+		public void Redraw()
+		{
+			Redraw(DispatcherPriority.Normal);
+		}
+		
+		/// <summary>
+		/// Causes the text editor to regenerate all visual lines.
+		/// </summary>
+		public void Redraw(DispatcherPriority redrawPriority)
+		{
+			VerifyAccess();
+			ClearVisualLines();
+			InvalidateMeasure(redrawPriority);
+		}
+		
+		/// <summary>
+		/// Causes the text editor to regenerate the specified visual line.
+		/// </summary>
+		public void Redraw(VisualLine visualLine, DispatcherPriority redrawPriority = DispatcherPriority.Normal)
+		{
+			VerifyAccess();
+			if (allVisualLines.Remove(visualLine)) {
+				DisposeVisualLine(visualLine);
+				InvalidateMeasure(redrawPriority);
+			}
+		}
+		
+		/// <summary>
+		/// Causes the text editor to redraw all lines overlapping with the specified segment.
+		/// </summary>
+		public void Redraw(int offset, int length, DispatcherPriority redrawPriority = DispatcherPriority.Normal)
+		{
+			VerifyAccess();
+			bool changedSomethingBeforeOrInLine = false;
+			for (int i = 0; i < allVisualLines.Count; i++) {
+				VisualLine visualLine = allVisualLines[i];
+				int lineStart = visualLine.FirstDocumentLine.Offset;
+				int lineEnd = visualLine.LastDocumentLine.Offset + visualLine.LastDocumentLine.TotalLength;
+				if (offset <= lineEnd) {
+					changedSomethingBeforeOrInLine = true;
+					if (offset + length >= lineStart) {
+						allVisualLines.RemoveAt(i--);
+						DisposeVisualLine(visualLine);
+					}
+				}
+			}
+			if (changedSomethingBeforeOrInLine) {
+				// Repaint not only when something in visible area was changed, but also when anything in front of it
+				// was changed. We might have to redraw the line number margin. Or the highlighting changed.
+				// However, we'll try to reuse the existing VisualLines.
+				InvalidateMeasure(redrawPriority);
+			}
+		}
+		
+		/// <summary>
+		/// Causes a known layer to redraw.
+		/// This method does not invalidate visual lines;
+		/// use the <see cref="Redraw()"/> method to do that.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA1801:ReviewUnusedParameters", MessageId = "knownLayer",
+		                                                 Justification="This method is meant to invalidate only a specific layer - I just haven't figured out how to do that, yet.")]
+		public void InvalidateLayer(KnownLayer knownLayer)
+		{
+			InvalidateMeasure(DispatcherPriority.Normal);
+		}
+		
+		/// <summary>
+		/// Causes a known layer to redraw.
+		/// This method does not invalidate visual lines;
+		/// use the <see cref="Redraw()"/> method to do that.
+		/// </summary>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA1801:ReviewUnusedParameters", MessageId = "knownLayer",
+		                                                 Justification="This method is meant to invalidate only a specific layer - I just haven't figured out how to do that, yet.")]
+		public void InvalidateLayer(KnownLayer knownLayer, DispatcherPriority priority)
+		{
+			InvalidateMeasure(priority);
+		}
+		
+		/// <summary>
+		/// Causes the text editor to redraw all lines overlapping with the specified segment.
+		/// Does nothing if segment is null.
+		/// </summary>
+		public void Redraw(ISegment segment, DispatcherPriority redrawPriority = DispatcherPriority.Normal)
+		{
+			if (segment != null) {
+				Redraw(segment.Offset, segment.Length, redrawPriority);
+			}
+		}
+		
+		/// <summary>
+		/// Invalidates all visual lines.
+		/// The caller of ClearVisualLines() must also call InvalidateMeasure() to ensure
+		/// that the visual lines will be recreated.
+		/// </summary>
+		void ClearVisualLines()
+		{
+			visibleVisualLines = null;
+			if (allVisualLines.Count != 0) {
+				foreach (VisualLine visualLine in allVisualLines) {
+					DisposeVisualLine(visualLine);
+				}
+				allVisualLines.Clear();
+			}
+		}
+		
+		void DisposeVisualLine(VisualLine visualLine)
+		{
+			if (newVisualLines != null && newVisualLines.Contains(visualLine)) {
+				throw new ArgumentException("Cannot dispose visual line because it is in construction!");
+			}
+			visibleVisualLines = null;
+			visualLine.Dispose();
+			RemoveInlineObjects(visualLine);
+		}
+		#endregion
+		
+		#region InvalidateMeasure(DispatcherPriority)
+		DispatcherOperation invalidateMeasureOperation;
+		
+		void InvalidateMeasure(DispatcherPriority priority)
+		{
+			if (priority >= DispatcherPriority.Render) {
+				if (invalidateMeasureOperation != null) {
+					invalidateMeasureOperation.Abort();
+					invalidateMeasureOperation = null;
+				}
+				base.InvalidateMeasure();
+			} else {
+				if (invalidateMeasureOperation != null) {
+					invalidateMeasureOperation.Priority = priority;
+				} else {
+					invalidateMeasureOperation = Dispatcher.BeginInvoke(
+						priority,
+						new Action(
+							delegate {
+								invalidateMeasureOperation = null;
+								base.InvalidateMeasure();
+							}
+						)
+					);
+				}
+			}
+		}
+		#endregion
+		
+		#region Get(OrConstruct)VisualLine
+		/// <summary>
+		/// Gets the visual line that contains the document line with the specified number.
+		/// Returns null if the document line is outside the visible range.
+		/// </summary>
+		public VisualLine GetVisualLine(int documentLineNumber)
+		{
+			// TODO: EnsureVisualLines() ?
+			foreach (VisualLine visualLine in allVisualLines) {
+				Debug.Assert(visualLine.IsDisposed == false);
+				int start = visualLine.FirstDocumentLine.LineNumber;
+				int end = visualLine.LastDocumentLine.LineNumber;
+				if (documentLineNumber >= start && documentLineNumber <= end)
+					return visualLine;
+			}
+			return null;
+		}
+		
+		/// <summary>
+		/// Gets the visual line that contains the document line with the specified number.
+		/// If that line is outside the visible range, a new VisualLine for that document line is constructed.
+		/// </summary>
+		public VisualLine GetOrConstructVisualLine(DocumentLine documentLine)
+		{
+			if (documentLine == null)
+				throw new ArgumentNullException("documentLine");
+			if (!this.Document.Lines.Contains(documentLine))
+				throw new InvalidOperationException("Line belongs to wrong document");
+			VerifyAccess();
+			
+			VisualLine l = GetVisualLine(documentLine.LineNumber);
+			if (l == null) {
+				TextRunProperties globalTextRunProperties = CreateGlobalTextRunProperties();
+				VisualLineTextParagraphProperties paragraphProperties = CreateParagraphProperties(globalTextRunProperties);
+				
+				while (heightTree.GetIsCollapsed(documentLine.LineNumber)) {
+					documentLine = documentLine.PreviousLine;
+				}
+				
+				l = BuildVisualLine(documentLine,
+				                    globalTextRunProperties, paragraphProperties,
+				                    elementGenerators.ToArray(), lineTransformers.ToArray(),
+				                    lastAvailableSize);
+				allVisualLines.Add(l);
+				// update all visual top values (building the line might have changed visual top of other lines due to word wrapping)
+				foreach (var line in allVisualLines) {
+					line.VisualTop = heightTree.GetVisualPosition(line.FirstDocumentLine);
+				}
+			}
+			return l;
+		}
+		#endregion
+		
+		#region Visual Lines (fields and properties)
+		List<VisualLine> allVisualLines = new List<VisualLine>();
+		ReadOnlyCollection<VisualLine> visibleVisualLines;
+		double clippedPixelsOnTop;
+		List<VisualLine> newVisualLines;
+		
+		/// <summary>
+		/// Gets the currently visible visual lines.
+		/// </summary>
+		/// <exception cref="VisualLinesInvalidException">
+		/// Gets thrown if there are invalid visual lines when this property is accessed.
+		/// You can use the <see cref="VisualLinesValid"/> property to check for this case,
+		/// or use the <see cref="EnsureVisualLines()"/> method to force creating the visual lines
+		/// when they are invalid.
+		/// </exception>
+		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1065:DoNotRaiseExceptionsInUnexpectedLocations")]
+		public ReadOnlyCollection<VisualLine> VisualLines {
+			get {
+                if (visibleVisualLines == null)
+                {
+                    return new ReadOnlyCollection<VisualLine>(new List<VisualLine>());
+                }
+                else
+                {
+                    return visibleVisualLines;
+                }
+			}
+		}
+		
+		/// <summary>
+		/// Gets whether the visual lines are valid.
+		/// Will return false after a call to Redraw().
+		/// Accessing the visual lines property will cause a <see cref="VisualLinesInvalidException"/>
+		/// if this property is <c>false</c>.
+		/// </summary>
+		public bool VisualLinesValid {
+			get { return visibleVisualLines != null; }
+		}
+		
+		/// <summary>
+		/// Occurs when the TextView is about to be measured and will regenerate its visual lines.
+		/// This event may be used to mark visual lines as invalid that would otherwise be reused.
+		/// </summary>
+		public event EventHandler<VisualLineConstructionStartEventArgs> VisualLineConstructionStarting;
+		
+		/// <summary>
+		/// Occurs when the TextView was measured and changed its visual lines.
+		/// </summary>
+		public event EventHandler VisualLinesChanged;
+		
+		/// <summary>
+		/// If the visual lines are invalid, creates new visual lines for the visible part
+		/// of the document.
+		/// If all visual lines are valid, this method does nothing.
+		/// </summary>
+		/// <exception cref="InvalidOperationException">The visual line build process is already running.
+		/// It is not allowed to call this method during the construction of a visual line.</exception>
+		public void EnsureVisualLines()
+		{
+			Dispatcher.VerifyAccess();
+			if (inMeasure)
+				throw new InvalidOperationException("The visual line build process is already running! Cannot EnsureVisualLines() during Measure!");
+			if (!VisualLinesValid) {
+				// increase priority for re-measure
+				InvalidateMeasure(DispatcherPriority.Normal);
+				// force immediate re-measure
+				UpdateLayout();
+			}
+			// Sometimes we still have invalid lines after UpdateLayout - work around the problem
+			// by calling MeasureOverride directly.
+			if (!VisualLinesValid) {
+				//Debug.WriteLine("UpdateLayout() failed in EnsureVisualLines");
+				//MeasureOverride(lastAvailableSize);
+    //            UpdateLayout();
+            }
+			//if (!VisualLinesValid)
+				//throw new VisualLinesInvalidException("Internal error: visual lines invalid after EnsureVisualLines call");
+		}
+		#endregion
+		
+		#region Measure
+		/// <summary>
+		/// Additonal amount that allows horizontal scrolling past the end of the longest line.
+		/// This is necessary to ensure the caret always is visible, even when it is at the end of the longest line.
+		/// </summary>
+		const double AdditionalHorizontalScrollAmount = 3;
+		
+		Size lastAvailableSize;
+		bool inMeasure;
+		
+		/// <inheritdoc/>
+		protected override Size MeasureOverride(Size availableSize)
+		{
+			// We don't support infinite available width, so we'll limit it to 32000 pixels.
+			if (availableSize.Width > 32000)
+				availableSize.Width = 32000;
+			
+			if (!canHorizontallyScroll && !availableSize.Width.IsClose(lastAvailableSize.Width))
+				ClearVisualLines();
+			lastAvailableSize = availableSize;
+			
+			foreach (UIElement layer in layers) {
+				layer.Measure(availableSize);
+			}
+			MeasureInlineObjects();
+			
+			InvalidateVisual(); // = InvalidateArrange+InvalidateRender
+			
+			double maxWidth;
+			if (document == null) {
+				// no document -> create empty list of lines
+				allVisualLines = new List<VisualLine>();
+				visibleVisualLines = allVisualLines.AsReadOnly();
+				maxWidth = 0;
+			} else {
+				inMeasure = true;
+				try {
+					maxWidth = CreateAndMeasureVisualLines(availableSize);
+				} finally {
+					inMeasure = false;
+				}
+			}
+			
+			// remove inline objects only at the end, so that inline objects that were re-used are not removed from the editor
+			RemoveInlineObjectsNow();
+			
+			maxWidth += AdditionalHorizontalScrollAmount;
+			double heightTreeHeight = this.DocumentHeight;
+			TextEditorOptions options = this.Options;
+			if (options.AllowScrollBelowDocument) {
+				if (!double.IsInfinity(scrollViewport.Height)) {
+					heightTreeHeight = Math.Max(heightTreeHeight, Math.Min(heightTreeHeight - 50, scrollOffset.Y) + scrollViewport.Height);
+				}
+			}
+			
+			textLayer.SetVisualLines(visibleVisualLines);
+			
+			SetScrollData(availableSize,
+			              new Size(maxWidth, heightTreeHeight),
+			              scrollOffset);
+			if (VisualLinesChanged != null)
+				VisualLinesChanged(this, EventArgs.Empty);
+			
+			return new Size(Math.Min(availableSize.Width, maxWidth), Math.Min(availableSize.Height, heightTreeHeight));
+		}
+		
+		/// <summary>
+		/// Build all VisualLines in the visible range.
+		/// </summary>
+		/// <returns>Width the longest line</returns>
+		double CreateAndMeasureVisualLines(Size availableSize)
+		{
+			TextRunProperties globalTextRunProperties = CreateGlobalTextRunProperties();
+			VisualLineTextParagraphProperties paragraphProperties = CreateParagraphProperties(globalTextRunProperties);
+			
+			//Debug.WriteLine("Measure availableSize=" + availableSize + ", scrollOffset=" + scrollOffset);
+			var firstLineInView = heightTree.GetLineByVisualPosition(scrollOffset.Y);
+			
+			// number of pixels clipped from the first visual line(s)
+			clippedPixelsOnTop = scrollOffset.Y - heightTree.GetVisualPosition(firstLineInView);
+			// clippedPixelsOnTop should be >= 0, except for floating point inaccurracy.
+			Debug.Assert(clippedPixelsOnTop >= -ExtensionMethods.Epsilon);
+			
+			newVisualLines = new List<VisualLine>();
+			
+			if (VisualLineConstructionStarting != null)
+				VisualLineConstructionStarting(this, new VisualLineConstructionStartEventArgs(firstLineInView));
+			
+			var elementGeneratorsArray = elementGenerators.ToArray();
+			var lineTransformersArray = lineTransformers.ToArray();
+			var nextLine = firstLineInView;
+			double maxWidth = 0;
+			double yPos = -clippedPixelsOnTop;
+			while (yPos < availableSize.Height && nextLine != null) {
+				VisualLine visualLine = GetVisualLine(nextLine.LineNumber);
+				if (visualLine == null) {
+					visualLine = BuildVisualLine(nextLine,
+					                             globalTextRunProperties, paragraphProperties,
+					                             elementGeneratorsArray, lineTransformersArray,
+					                             availableSize);
+				}
+				
+				visualLine.VisualTop = scrollOffset.Y + yPos;
+				
+				nextLine = visualLine.LastDocumentLine.NextLine;
+				
+				yPos += visualLine.Height;
+				
+				foreach (TextLine textLine in visualLine.TextLines) {
+					if (textLine.WidthIncludingTrailingWhitespace > maxWidth)
+						maxWidth = textLine.WidthIncludingTrailingWhitespace;
+				}
+				
+				newVisualLines.Add(visualLine);
+			}
+			
+			foreach (VisualLine line in allVisualLines) {
+				Debug.Assert(line.IsDisposed == false);
+				if (!newVisualLines.Contains(line))
+					DisposeVisualLine(line);
+			}
+			
+			allVisualLines = newVisualLines;
+			// visibleVisualLines = readonly copy of visual lines
+			visibleVisualLines = new ReadOnlyCollection<VisualLine>(newVisualLines.ToArray());
+			newVisualLines = null;
+			
+			if (allVisualLines.Any(line => line.IsDisposed)) {
+				throw new InvalidOperationException("A visual line was disposed even though it is still in use.\n" +
+				                                    "This can happen when Redraw() is called during measure for lines " +
+				                                    "that are already constructed.");
+			}
+			return maxWidth;
+		}
+		#endregion
+		
+		#region BuildVisualLine
+		TextFormatter formatter;
+		internal TextViewCachedElements cachedElements;
+		
+		TextRunProperties CreateGlobalTextRunProperties()
+		{
+			var p = new GlobalTextRunProperties();
+			p.typeface = this.CreateTypeface();
+			p.fontRenderingEmSize = FontSize;
+			p.foregroundBrush = (Brush)GetValue(Control.ForegroundProperty);
+			ExtensionMethods.CheckIsFrozen(p.foregroundBrush);
+			p.cultureInfo = CultureInfo.CurrentCulture;
+			return p;
+		}
+		
+		VisualLineTextParagraphProperties CreateParagraphProperties(TextRunProperties defaultTextRunProperties)
+		{
+			return new VisualLineTextParagraphProperties {
+				defaultTextRunProperties = defaultTextRunProperties,
+				textWrapping = canHorizontallyScroll ? TextWrapping.NoWrap : TextWrapping.Wrap,
+				tabSize = Options.IndentationSize * WideSpaceWidth
+			};
+		}
+		
+		VisualLine BuildVisualLine(DocumentLine documentLine,
+		                           TextRunProperties globalTextRunProperties,
+		                           VisualLineTextParagraphProperties paragraphProperties,
+		                           VisualLineElementGenerator[] elementGeneratorsArray,
+		                           IVisualLineTransformer[] lineTransformersArray,
+		                           Size availableSize)
+		{
+			if (heightTree.GetIsCollapsed(documentLine.LineNumber))
+				throw new InvalidOperationException("Trying to build visual line from collapsed line");
+			
+			//Debug.WriteLine("Building line " + documentLine.LineNumber);
+			
+			VisualLine visualLine = new VisualLine(this, documentLine);
+			VisualLineTextSource textSource = new VisualLineTextSource(visualLine) {
+				Document = document,
+				GlobalTextRunProperties = globalTextRunProperties,
+				TextView = this
+			};
+			
+			visualLine.ConstructVisualElements(textSource, elementGeneratorsArray);
+			
+			if (visualLine.FirstDocumentLine != visualLine.LastDocumentLine) {
+				// Check whether the lines are collapsed correctly:
+				double firstLinePos = heightTree.GetVisualPosition(visualLine.FirstDocumentLine.NextLine);
+				double lastLinePos = heightTree.GetVisualPosition(visualLine.LastDocumentLine.NextLine ?? visualLine.LastDocumentLine);
+				if (!firstLinePos.IsClose(lastLinePos)) {
+					for (int i = visualLine.FirstDocumentLine.LineNumber + 1; i <= visualLine.LastDocumentLine.LineNumber; i++) {
+						if (!heightTree.GetIsCollapsed(i))
+							throw new InvalidOperationException("Line " + i + " was skipped by a VisualLineElementGenerator, but it is not collapsed.");
+					}
+					throw new InvalidOperationException("All lines collapsed but visual pos different - height tree inconsistency?");
+				}
+			}
+			
+			visualLine.RunTransformers(textSource, lineTransformersArray);
+			
+			// now construct textLines:
+			int textOffset = 0;
+			TextLineBreak lastLineBreak = null;
+			var textLines = new List<TextLine>();
+			paragraphProperties.indent = 0;
+			paragraphProperties.firstLineInParagraph = true;
+			while (textOffset <= visualLine.VisualLengthWithEndOfLineMarker) {
+				TextLine textLine = formatter.FormatLine(
+					textSource,
+					textOffset,
+					availableSize.Width,
+					paragraphProperties,
+					lastLineBreak
+				);
+				textLines.Add(textLine);
+				textOffset += textLine.Length;
+				
+				// exit loop so that we don't do the indentation calculation if there's only a single line
+				if (textOffset >= visualLine.VisualLengthWithEndOfLineMarker)
+					break;
+				
+				if (paragraphProperties.firstLineInParagraph) {
+					paragraphProperties.firstLineInParagraph = false;
+					
+					TextEditorOptions options = this.Options;
+					double indentation = 0;
+					if (options.InheritWordWrapIndentation) {
+						// determine indentation for next line:
+						int indentVisualColumn = GetIndentationVisualColumn(visualLine);
+						if (indentVisualColumn > 0 && indentVisualColumn < textOffset) {
+							indentation = textLine.GetDistanceFromCharacterHit(new CharacterHit(indentVisualColumn, 0));
+						}
+					}
+					indentation += options.WordWrapIndentation;
+					// apply the calculated indentation unless it's more than half of the text editor size:
+					if (indentation > 0 && indentation * 2 < availableSize.Width)
+						paragraphProperties.indent = indentation;
+				}
+				lastLineBreak = textLine.GetTextLineBreak();
+			}
+			visualLine.SetTextLines(textLines);
+			heightTree.SetHeight(visualLine.FirstDocumentLine, visualLine.Height);
+			return visualLine;
+		}
+		
+		static int GetIndentationVisualColumn(VisualLine visualLine)
+		{
+			if (visualLine.Elements.Count == 0)
+				return 0;
+			int column = 0;
+			int elementIndex = 0;
+			VisualLineElement element = visualLine.Elements[elementIndex];
+			while (element.IsWhitespace(column)) {
+				column++;
+				if (column == element.VisualColumn + element.VisualLength) {
+					elementIndex++;
+					if (elementIndex == visualLine.Elements.Count)
+						break;
+					element = visualLine.Elements[elementIndex];
+				}
+			}
+			return column;
+		}
+		#endregion
+		
+		#region Arrange
+		/// <summary>
+		/// Arrange implementation.
+		/// </summary>
+		protected override Size ArrangeOverride(Size finalSize)
+		{
+			EnsureVisualLines();
+			
+			foreach (UIElement layer in layers) {
+				layer.Arrange(new Rect(new Point(0, 0), finalSize));
+			}
+			
+			if (document == null || allVisualLines.Count == 0)
+				return finalSize;
+			
+			// validate scroll position
+			Vector newScrollOffset = scrollOffset;
+			if (scrollOffset.X + finalSize.Width > scrollExtent.Width) {
+				newScrollOffset.X = Math.Max(0, scrollExtent.Width - finalSize.Width);
+			}
+			if (scrollOffset.Y + finalSize.Height > scrollExtent.Height) {
+				newScrollOffset.Y = Math.Max(0, scrollExtent.Height - finalSize.Height);
+			}
+			if (SetScrollData(scrollViewport, scrollExtent, newScrollOffset))
+				InvalidateMeasure(DispatcherPriority.Normal);
+			
+			//Debug.WriteLine("Arrange finalSize=" + finalSize + ", scrollOffset=" + scrollOffset);
+			
+//			double maxWidth = 0;
+			
+			if (visibleVisualLines != null) {
+				Point pos = new Point(-scrollOffset.X, -clippedPixelsOnTop);
+				foreach (VisualLine visualLine in visibleVisualLines) {
+					int offset = 0;
+					foreach (TextLine textLine in visualLine.TextLines) {
+						foreach (var span in textLine.GetTextRunSpans()) {
+							InlineObjectRun inline = span.Value as InlineObjectRun;
+							if (inline != null && inline.VisualLine != null) {
+								Debug.Assert(inlineObjects.Contains(inline));
+								double distance = textLine.GetDistanceFromCharacterHit(new CharacterHit(offset, 0));
+								inline.Element.Arrange(new Rect(new Point(pos.X + distance, pos.Y), inline.Element.DesiredSize));
+							}
+							offset += span.Length;
+						}
+						pos.Y += textLine.Height;
+					}
+				}
+			}
+			InvalidateCursor();
+			
+			return finalSize;
+		}
+		#endregion
+		
+		#region Render
+		readonly ObserveAddRemoveCollection<IBackgroundRenderer> backgroundRenderers;
+		
+		/// <summary>
+		/// Gets the list of background renderers.
+		/// </summary>
+		public IList<IBackgroundRenderer> BackgroundRenderers {
+			get { return backgroundRenderers; }
+		}
+		
+		void BackgroundRenderer_Added(IBackgroundRenderer renderer)
+		{
+			ConnectToTextView(renderer);
+			InvalidateLayer(renderer.Layer);
+		}
+		
+		void BackgroundRenderer_Removed(IBackgroundRenderer renderer)
+		{
+			DisconnectFromTextView(renderer);
+			InvalidateLayer(renderer.Layer);
+		}
+		
+		/// <inheritdoc/>
+		protected override void OnRender(DrawingContext drawingContext)
+		{
+			RenderBackground(drawingContext, KnownLayer.Background);
+			foreach (var line in visibleVisualLines) {
+				Brush currentBrush = null;
+				int startVC = 0;
+				int length = 0;
+				foreach (var element in line.Elements) {
+					if (currentBrush == null || !currentBrush.Equals(element.BackgroundBrush)) {
+						if (currentBrush != null) {
+							BackgroundGeometryBuilder builder = new BackgroundGeometryBuilder();
+							builder.AlignToWholePixels = true;
+							builder.CornerRadius = 3;
+							foreach (var rect in BackgroundGeometryBuilder.GetRectsFromVisualSegment(this, line, startVC, startVC + length))
+								builder.AddRectangle(this, rect);
+							Geometry geometry = builder.CreateGeometry();
+							if (geometry != null) {
+								drawingContext.DrawGeometry(currentBrush, null, geometry);
+							}
+						}
+						startVC = element.VisualColumn;
+						length = element.DocumentLength;
+						currentBrush = element.BackgroundBrush;
+					} else {
+						length += element.VisualLength;
+					}
+				}
+				if (currentBrush != null) {
+					BackgroundGeometryBuilder builder = new BackgroundGeometryBuilder();
+					builder.AlignToWholePixels = true;
+					builder.CornerRadius = 3;
+					foreach (var rect in BackgroundGeometryBuilder.GetRectsFromVisualSegment(this, line, startVC, startVC + length))
+						builder.AddRectangle(this, rect);
+					Geometry geometry = builder.CreateGeometry();
+					if (geometry != null) {
+						drawingContext.DrawGeometry(currentBrush, null, geometry);
+					}
+				}
+			}
+		}
+		
+		internal void RenderBackground(DrawingContext drawingContext, KnownLayer layer)
+		{
+			foreach (IBackgroundRenderer bg in backgroundRenderers) {
+				if (bg.Layer == layer) {
+					bg.Draw(this, drawingContext);
+				}
+			}
+		}
+		
+		internal void ArrangeTextLayer(IList<VisualLineDrawingVisual> visuals)
+		{
+			Point pos = new Point(-scrollOffset.X, -clippedPixelsOnTop);
+			foreach (VisualLineDrawingVisual visual in visuals) {
+				TranslateTransform t = visual.Transform as TranslateTransform;
+				if (t == null || t.X != pos.X || t.Y != pos.Y) {
+					visual.Transform = new TranslateTransform(pos.X, pos.Y);
+					visual.Transform.Freeze();
+				}
+				pos.Y += visual.Height;
+			}
+		}
+		#endregion
+		
+		#region IScrollInfo implementation
+		/// <summary>
+		/// Size of the document, in pixels.
+		/// </summary>
+		Size scrollExtent;
+		
+		/// <summary>
+		/// Offset of the scroll position.
+		/// </summary>
+		Vector scrollOffset;
+		
+		/// <summary>
+		/// Size of the viewport.
+		/// </summary>
+		Size scrollViewport;
+		
+		void ClearScrollData()
+		{
+			SetScrollData(new Size(), new Size(), new Vector());
+		}
+		
+		bool SetScrollData(Size viewport, Size extent, Vector offset)
+		{
+			if (!(viewport.IsClose(this.scrollViewport)
+			      && extent.IsClose(this.scrollExtent)
+			      && offset.IsClose(this.scrollOffset)))
+			{
+				this.scrollViewport = viewport;
+				this.scrollExtent = extent;
+				SetScrollOffset(offset);
+				this.OnScrollChange();
+				return true;
+			}
+			return false;
+		}
+		
+		void OnScrollChange()
+		{
+			ScrollViewer scrollOwner = ((IScrollInfo)this).ScrollOwner;
+			if (scrollOwner != null) {
+				scrollOwner.InvalidateScrollInfo();
+			}
+		}
+		
+		bool canVerticallyScroll;
+		bool IScrollInfo.CanVerticallyScroll {
+			get { return canVerticallyScroll; }
+			set {
+				if (canVerticallyScroll != value) {
+					canVerticallyScroll = value;
+					InvalidateMeasure(DispatcherPriority.Normal);
+				}
+			}
+		}
+		bool canHorizontallyScroll;
+		bool IScrollInfo.CanHorizontallyScroll {
+			get { return canHorizontallyScroll; }
+			set {
+				if (canHorizontallyScroll != value) {
+					canHorizontallyScroll = value;
+					ClearVisualLines();
+					InvalidateMeasure(DispatcherPriority.Normal);
+				}
+			}
+		}
+		
+		double IScrollInfo.ExtentWidth {
+			get { return scrollExtent.Width; }
+		}
+		
+		double IScrollInfo.ExtentHeight {
+			get { return scrollExtent.Height; }
+		}
+		
+		double IScrollInfo.ViewportWidth {
+			get { return scrollViewport.Width; }
+		}
+		
+		double IScrollInfo.ViewportHeight {
+			get { return scrollViewport.Height; }
+		}
+		
+		/// <summary>
+		/// Gets the horizontal scroll offset.
+		/// </summary>
+		public double HorizontalOffset {
+			get { return scrollOffset.X; }
+		}
+		
+		/// <summary>
+		/// Gets the vertical scroll offset.
+		/// </summary>
+		public double VerticalOffset {
+			get { return scrollOffset.Y; }
+		}
+		
+		/// <summary>
+		/// Gets the scroll offset;
+		/// </summary>
+		public Vector ScrollOffset {
+			get { return scrollOffset; }
+		}
+		
+		/// <summary>
+		/// Occurs when the scroll offset has changed.
+		/// </summary>
+		public event EventHandler ScrollOffsetChanged;
+		
+		void SetScrollOffset(Vector vector)
+		{
+			if (!canHorizontallyScroll)
+				vector.X = 0;
+			if (!canVerticallyScroll)
+				vector.Y = 0;
+			
+			if (!scrollOffset.IsClose(vector)) {
+				scrollOffset = vector;
+				if (ScrollOffsetChanged != null)
+					ScrollOffsetChanged(this, EventArgs.Empty);
+			}
+		}
+		
+		ScrollViewer IScrollInfo.ScrollOwner { get; set; }
+		
+		void IScrollInfo.LineUp()
+		{
+			((IScrollInfo)this).SetVerticalOffset(scrollOffset.Y - DefaultLineHeight);
+		}
+		
+		void IScrollInfo.LineDown()
+		{
+			((IScrollInfo)this).SetVerticalOffset(scrollOffset.Y + DefaultLineHeight);
+		}
+		
+		void IScrollInfo.LineLeft()
+		{
+			((IScrollInfo)this).SetHorizontalOffset(scrollOffset.X - WideSpaceWidth);
+		}
+		
+		void IScrollInfo.LineRight()
+		{
+			((IScrollInfo)this).SetHorizontalOffset(scrollOffset.X + WideSpaceWidth);
+		}
+		
+		void IScrollInfo.PageUp()
+		{
+			((IScrollInfo)this).SetVerticalOffset(scrollOffset.Y - scrollViewport.Height);
+		}
+		
+		void IScrollInfo.PageDown()
+		{
+			((IScrollInfo)this).SetVerticalOffset(scrollOffset.Y + scrollViewport.Height);
+		}
+		
+		void IScrollInfo.PageLeft()
+		{
+			((IScrollInfo)this).SetHorizontalOffset(scrollOffset.X - scrollViewport.Width);
+		}
+		
+		void IScrollInfo.PageRight()
+		{
+			((IScrollInfo)this).SetHorizontalOffset(scrollOffset.X + scrollViewport.Width);
+		}
+		
+		void IScrollInfo.MouseWheelUp()
+		{
+			((IScrollInfo)this).SetVerticalOffset(
+				scrollOffset.Y - (SystemParameters.WheelScrollLines * DefaultLineHeight));
+			OnScrollChange();
+		}
+		
+		void IScrollInfo.MouseWheelDown()
+		{
+			((IScrollInfo)this).SetVerticalOffset(
+				scrollOffset.Y + (SystemParameters.WheelScrollLines * DefaultLineHeight));
+			OnScrollChange();
+		}
+		
+		void IScrollInfo.MouseWheelLeft()
+		{
+			((IScrollInfo)this).SetHorizontalOffset(
+				scrollOffset.X - (SystemParameters.WheelScrollLines * WideSpaceWidth));
+			OnScrollChange();
+		}
+		
+		void IScrollInfo.MouseWheelRight()
+		{
+			((IScrollInfo)this).SetHorizontalOffset(
+				scrollOffset.X + (SystemParameters.WheelScrollLines * WideSpaceWidth));
+			OnScrollChange();
+		}
+		
+		bool defaultTextMetricsValid;
+		double wideSpaceWidth; // Width of an 'x'. Used as basis for the tab width, and for scrolling.
+		double defaultLineHeight; // Height of a line containing 'x'. Used for scrolling.
+		double defaultBaseline; // Baseline of a line containing 'x'. Used for TextTop/TextBottom calculation.
+		
+		/// <summary>
+		/// Gets the width of a 'wide space' (the space width used for calculating the tab size).
+		/// </summary>
+		/// <remarks>
+		/// This is the width of an 'x' in the current font.
+		/// We do not measure the width of an actual space as that would lead to tiny tabs in
+		/// some proportional fonts.
+		/// For monospaced fonts, this property will return the expected value, as 'x' and ' ' have the same width.
+		/// </remarks>
+		public double WideSpaceWidth {
+			get {
+				CalculateDefaultTextMetrics();
+				return wideSpaceWidth;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the default line height. This is the height of an empty line or a line containing regular text.
+		/// Lines that include formatted text or custom UI elements may have a different line height.
+		/// </summary>
+		public double DefaultLineHeight {
+			get {
+				CalculateDefaultTextMetrics();
+				return defaultLineHeight;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the default baseline position. This is the difference between <see cref="VisualYPosition.TextTop"/>
+		/// and <see cref="VisualYPosition.Baseline"/> for a line containing regular text.
+		/// Lines that include formatted text or custom UI elements may have a different baseline.
+		/// </summary>
+		public double DefaultBaseline {
+			get {
+				CalculateDefaultTextMetrics();
+				return defaultBaseline;
+			}
+		}
+		
+		void InvalidateDefaultTextMetrics()
+		{
+			defaultTextMetricsValid = false;
+			if (heightTree != null) {
+				// calculate immediately so that height tree gets updated
+				CalculateDefaultTextMetrics();
+			}
+		}
+		
+		void CalculateDefaultTextMetrics()
+		{
+			if (defaultTextMetricsValid)
+				return;
+			defaultTextMetricsValid = true;
+			if (formatter != null) {
+				var textRunProperties = CreateGlobalTextRunProperties();
+				using (var line = formatter.FormatLine(
+					new SimpleTextSource("x", textRunProperties),
+					0, 32000,
+					new VisualLineTextParagraphProperties { defaultTextRunProperties = textRunProperties },
+					null))
+				{
+					wideSpaceWidth = Math.Max(1, line.WidthIncludingTrailingWhitespace);
+					defaultBaseline = Math.Max(1, line.Baseline);
+					defaultLineHeight = Math.Max(1, line.Height);
+				}
+			} else {
+				wideSpaceWidth = FontSize / 2;
+				defaultBaseline = FontSize;
+				defaultLineHeight = FontSize + 3;
+			}
+			// Update heightTree.DefaultLineHeight, if a document is loaded.
+			if (heightTree != null)
+				heightTree.DefaultLineHeight = defaultLineHeight;
+		}
+		
+		static double ValidateVisualOffset(double offset)
+		{
+			if (double.IsNaN(offset))
+				throw new ArgumentException("offset must not be NaN");
+			if (offset < 0)
+				return 0;
+			else
+				return offset;
+		}
+		
+		void IScrollInfo.SetHorizontalOffset(double offset)
+		{
+			offset = ValidateVisualOffset(offset);
+			if (!scrollOffset.X.IsClose(offset)) {
+				SetScrollOffset(new Vector(offset, scrollOffset.Y));
+				InvalidateVisual();
+				textLayer.InvalidateVisual();
+			}
+		}
+		
+		void IScrollInfo.SetVerticalOffset(double offset)
+		{
+			offset = ValidateVisualOffset(offset);
+			if (!scrollOffset.Y.IsClose(offset)) {
+				SetScrollOffset(new Vector(scrollOffset.X, offset));
+				InvalidateMeasure(DispatcherPriority.Normal);
+			}
+		}
+		
+		Rect IScrollInfo.MakeVisible(Visual visual, Rect rectangle)
+		{
+			if (rectangle.IsEmpty || visual == null || visual == this || !this.IsAncestorOf(visual)) {
+				return Rect.Empty;
+			}
+			// Convert rectangle into our coordinate space.
+			GeneralTransform childTransform = visual.TransformToAncestor(this);
+			rectangle = childTransform.TransformBounds(rectangle);
+			
+			MakeVisible(Rect.Offset(rectangle, scrollOffset));
+			
+			return rectangle;
+		}
+		
+		/// <summary>
+		/// Scrolls the text view so that the specified rectangle gets visible.
+		/// </summary>
+		public void MakeVisible(Rect rectangle)
+		{
+			Rect visibleRectangle = new Rect(scrollOffset.X, scrollOffset.Y,
+			                                 scrollViewport.Width, scrollViewport.Height);
+			Vector newScrollOffset = scrollOffset;
+			if (rectangle.Left < visibleRectangle.Left) {
+				if (rectangle.Right > visibleRectangle.Right) {
+					newScrollOffset.X = rectangle.Left + rectangle.Width / 2;
+				} else {
+					newScrollOffset.X = rectangle.Left;
+				}
+			} else if (rectangle.Right > visibleRectangle.Right) {
+				newScrollOffset.X = rectangle.Right - scrollViewport.Width;
+			}
+			if (rectangle.Top < visibleRectangle.Top) {
+				if (rectangle.Bottom > visibleRectangle.Bottom) {
+					newScrollOffset.Y = rectangle.Top + rectangle.Height / 2;
+				} else {
+					newScrollOffset.Y = rectangle.Top;
+				}
+			} else if (rectangle.Bottom > visibleRectangle.Bottom) {
+				newScrollOffset.Y = rectangle.Bottom - scrollViewport.Height;
+			}
+			newScrollOffset.X = ValidateVisualOffset(newScrollOffset.X);
+			newScrollOffset.Y = ValidateVisualOffset(newScrollOffset.Y);
+			if (!scrollOffset.IsClose(newScrollOffset)) {
+				SetScrollOffset(newScrollOffset);
+				this.OnScrollChange();
+				InvalidateMeasure(DispatcherPriority.Normal);
+			}
+		}
+		#endregion
+		
+		#region Visual element mouse handling
+		/// <inheritdoc/>
+		protected override HitTestResult HitTestCore(PointHitTestParameters hitTestParameters)
+		{
+			// accept clicks even where the text area draws no background
+			return new PointHitTestResult(this, hitTestParameters.HitPoint);
+		}
+		
+		[ThreadStatic] static bool invalidCursor;
+		
+		/// <summary>
+		/// Updates the mouse cursor by calling <see cref="Mouse.UpdateCursor"/>, but with input priority.
+		/// </summary>
+		public static void InvalidateCursor()
+		{
+			if (!invalidCursor) {
+				invalidCursor = true;
+				Dispatcher.CurrentDispatcher.BeginInvoke(
+					DispatcherPriority.Input,
+					new Action(
+						delegate {
+							invalidCursor = false;
+							Mouse.UpdateCursor();
+						}));
+			}
+		}
+		
+		/// <inheritdoc/>
+		protected override void OnQueryCursor(QueryCursorEventArgs e)
+		{
+			VisualLineElement element = GetVisualLineElementFromPosition(e.GetPosition(this) + scrollOffset);
+			if (element != null) {
+				element.OnQueryCursor(e);
+			}
+		}
+		
+		/// <inheritdoc/>
+		protected override void OnMouseDown(MouseButtonEventArgs e)
+		{
+			base.OnMouseDown(e);
+			if (!e.Handled) {
+				EnsureVisualLines();
+				VisualLineElement element = GetVisualLineElementFromPosition(e.GetPosition(this) + scrollOffset);
+				if (element != null) {
+					element.OnMouseDown(e);
+				}
+			}
+		}
+		
+		/// <inheritdoc/>
+		protected override void OnMouseUp(MouseButtonEventArgs e)
+		{
+			base.OnMouseUp(e);
+			if (!e.Handled) {
+				EnsureVisualLines();
+				VisualLineElement element = GetVisualLineElementFromPosition(e.GetPosition(this) + scrollOffset);
+				if (element != null) {
+					element.OnMouseUp(e);
+				}
+			}
+		}
+		#endregion
+		
+		#region Getting elements from Visual Position
+		/// <summary>
+		/// Gets the visual line at the specified document position (relative to start of document).
+		/// Returns null if there is no visual line for the position (e.g. the position is outside the visible
+		/// text area).
+		/// </summary>
+		public VisualLine GetVisualLineFromVisualTop(double visualTop)
+		{
+			// TODO: change this method to also work outside the visible range -
+			// required to make GetPosition work as expected!
+			EnsureVisualLines();
+			foreach (VisualLine vl in this.VisualLines) {
+				if (visualTop < vl.VisualTop)
+					continue;
+				if (visualTop < vl.VisualTop + vl.Height)
+					return vl;
+			}
+			return null;
+		}
+		
+		/// <summary>
+		/// Gets the visual top position (relative to start of document) from a document line number.
+		/// </summary>
+		public double GetVisualTopByDocumentLine(int line)
+		{
+			VerifyAccess();
+			if (heightTree == null)
+				throw ThrowUtil.NoDocumentAssigned();
+			return heightTree.GetVisualPosition(heightTree.GetLineByNumber(line));
+		}
+		
+		VisualLineElement GetVisualLineElementFromPosition(Point visualPosition)
+		{
+			VisualLine vl = GetVisualLineFromVisualTop(visualPosition.Y);
+			if (vl != null) {
+				int column = vl.GetVisualColumnFloor(visualPosition);
+//				Debug.WriteLine(vl.FirstDocumentLine.LineNumber + " vc " + column);
+				foreach (VisualLineElement element in vl.Elements) {
+					if (element.VisualColumn + element.VisualLength <= column)
+						continue;
+					return element;
+				}
+			}
+			return null;
+		}
+		#endregion
+		
+		#region Visual Position <-> TextViewPosition
+		/// <summary>
+		/// Gets the visual position from a text view position.
+		/// </summary>
+		/// <param name="position">The text view position.</param>
+		/// <param name="yPositionMode">The mode how to retrieve the Y position.</param>
+		/// <returns>The position in WPF device-independent pixels relative
+		/// to the top left corner of the document.</returns>
+		public Point GetVisualPosition(TextViewPosition position, VisualYPosition yPositionMode)
+		{
+			VerifyAccess();
+			if (this.Document == null)
+				throw ThrowUtil.NoDocumentAssigned();
+			DocumentLine documentLine = this.Document.GetLineByNumber(position.Line);
+			VisualLine visualLine = GetOrConstructVisualLine(documentLine);
+			int visualColumn = position.VisualColumn;
+			if (visualColumn < 0) {
+				int offset = documentLine.Offset + position.Column - 1;
+				visualColumn = visualLine.GetVisualColumn(offset - visualLine.FirstDocumentLine.Offset);
+			}
+			return visualLine.GetVisualPosition(visualColumn, yPositionMode);
+		}
+		
+		/// <summary>
+		/// Gets the text view position from the specified visual position.
+		/// If the position is within a character, it is rounded to the next character boundary.
+		/// </summary>
+		/// <param name="visualPosition">The position in WPF device-independent pixels relative
+		/// to the top left corner of the document.</param>
+		/// <returns>The logical position, or null if the position is outside the document.</returns>
+		public TextViewPosition? GetPosition(Point visualPosition)
+		{
+			VerifyAccess();
+			if (this.Document == null)
+				throw ThrowUtil.NoDocumentAssigned();
+			VisualLine line = GetVisualLineFromVisualTop(visualPosition.Y);
+			if (line == null)
+				return null;
+			int visualColumn = line.GetVisualColumn(visualPosition);
+			int documentOffset = line.GetRelativeOffset(visualColumn) + line.FirstDocumentLine.Offset;
+			return new TextViewPosition(document.GetLocation(documentOffset), visualColumn);
+		}
+		
+		/// <summary>
+		/// Gets the text view position from the specified visual position.
+		/// If the position is inside a character, the position in front of the character is returned.
+		/// </summary>
+		/// <param name="visualPosition">The position in WPF device-independent pixels relative
+		/// to the top left corner of the document.</param>
+		/// <returns>The logical position, or null if the position is outside the document.</returns>
+		public TextViewPosition? GetPositionFloor(Point visualPosition)
+		{
+			VerifyAccess();
+			if (this.Document == null)
+				throw ThrowUtil.NoDocumentAssigned();
+			VisualLine line = GetVisualLineFromVisualTop(visualPosition.Y);
+			if (line == null)
+				return null;
+			int visualColumn = line.GetVisualColumnFloor(visualPosition);
+			int documentOffset = line.GetRelativeOffset(visualColumn) + line.FirstDocumentLine.Offset;
+			return new TextViewPosition(document.GetLocation(documentOffset), visualColumn);
+		}
+		#endregion
+		
+		#region Service Provider
+		readonly ServiceContainer services = new ServiceContainer();
+		
+		/// <summary>
+		/// Gets a service container used to associate services with the text view.
+		/// </summary>
+		public ServiceContainer Services {
+			get { return services; }
+		}
+		
+		object IServiceProvider.GetService(Type serviceType)
+		{
+			return services.GetService(serviceType);
+		}
+		
+		void ConnectToTextView(object obj)
+		{
+			ITextViewConnect c = obj as ITextViewConnect;
+			if (c != null)
+				c.AddToTextView(this);
+		}
+		
+		void DisconnectFromTextView(object obj)
+		{
+			ITextViewConnect c = obj as ITextViewConnect;
+			if (c != null)
+				c.RemoveFromTextView(this);
+		}
+		#endregion
+		
+		#region MouseHover
+		/// <summary>
+		/// The PreviewMouseHover event.
+		/// </summary>
+		public static readonly RoutedEvent PreviewMouseHoverEvent =
+			EventManager.RegisterRoutedEvent("PreviewMouseHover", RoutingStrategy.Tunnel,
+			                                 typeof(MouseEventHandler), typeof(TextView));
+		/// <summary>
+		/// The MouseHover event.
+		/// </summary>
+		public static readonly RoutedEvent MouseHoverEvent =
+			EventManager.RegisterRoutedEvent("MouseHover", RoutingStrategy.Bubble,
+			                                 typeof(MouseEventHandler), typeof(TextView));
+		
+		/// <summary>
+		/// The PreviewMouseHoverStopped event.
+		/// </summary>
+		public static readonly RoutedEvent PreviewMouseHoverStoppedEvent =
+			EventManager.RegisterRoutedEvent("PreviewMouseHoverStopped", RoutingStrategy.Tunnel,
+			                                 typeof(MouseEventHandler), typeof(TextView));
+		/// <summary>
+		/// The MouseHoverStopped event.
+		/// </summary>
+		public static readonly RoutedEvent MouseHoverStoppedEvent =
+			EventManager.RegisterRoutedEvent("MouseHoverStopped", RoutingStrategy.Bubble,
+			                                 typeof(MouseEventHandler), typeof(TextView));
+		
+		
+		/// <summary>
+		/// Occurs when the mouse has hovered over a fixed location for some time.
+		/// </summary>
+		public event MouseEventHandler PreviewMouseHover {
+			add { AddHandler(PreviewMouseHoverEvent, value); }
+			remove { RemoveHandler(PreviewMouseHoverEvent, value); }
+		}
+		
+		/// <summary>
+		/// Occurs when the mouse has hovered over a fixed location for some time.
+		/// </summary>
+		public event MouseEventHandler MouseHover {
+			add { AddHandler(MouseHoverEvent, value); }
+			remove { RemoveHandler(MouseHoverEvent, value); }
+		}
+		
+		/// <summary>
+		/// Occurs when the mouse had previously hovered but now started moving again.
+		/// </summary>
+		public event MouseEventHandler PreviewMouseHoverStopped {
+			add { AddHandler(PreviewMouseHoverStoppedEvent, value); }
+			remove { RemoveHandler(PreviewMouseHoverStoppedEvent, value); }
+		}
+		
+		/// <summary>
+		/// Occurs when the mouse had previously hovered but now started moving again.
+		/// </summary>
+		public event MouseEventHandler MouseHoverStopped {
+			add { AddHandler(MouseHoverStoppedEvent, value); }
+			remove { RemoveHandler(MouseHoverStoppedEvent, value); }
+		}
+		
+		MouseHoverLogic hoverLogic;
+		
+		void RaiseHoverEventPair(MouseEventArgs e, RoutedEvent tunnelingEvent, RoutedEvent bubblingEvent)
+		{
+			var mouseDevice = e.MouseDevice;
+			var stylusDevice = e.StylusDevice;
+			int inputTime = Environment.TickCount;
+			var args1 = new MouseEventArgs(mouseDevice, inputTime, stylusDevice) {
+				RoutedEvent = tunnelingEvent,
+				Source = this
+			};
+			RaiseEvent(args1);
+			var args2 = new MouseEventArgs(mouseDevice, inputTime, stylusDevice) {
+				RoutedEvent = bubblingEvent,
+				Source = this,
+				Handled = args1.Handled
+			};
+			RaiseEvent(args2);
+		}
+		#endregion
+		
+		/// <summary>
+		/// Collapses lines for the purpose of scrolling. <see cref="DocumentLine"/>s marked as collapsed will be hidden
+		/// and not used to start the generation of a <see cref="VisualLine"/>.
+		/// </summary>
+		/// <remarks>
+		/// This method is meant for <see cref="VisualLineElementGenerator"/>s that cause <see cref="VisualLine"/>s to span
+		/// multiple <see cref="DocumentLine"/>s. Do not call it without providing a corresponding
+		/// <see cref="VisualLineElementGenerator"/>.
+		/// If you want to create collapsible text sections, see <see cref="Folding.FoldingManager"/>.
+		/// 
+		/// Note that if you want a VisualLineElement to span from line N to line M, then you need to collapse only the lines
+		/// N+1 to M. Do not collapse line N itself.
+		/// 
+		/// When you no longer need the section to be collapsed, call <see cref="CollapsedLineSection.Uncollapse()"/> on the
+		/// <see cref="CollapsedLineSection"/> returned from this method.
+		/// </remarks>
+		public CollapsedLineSection CollapseLines(DocumentLine start, DocumentLine end)
+		{
+			VerifyAccess();
+			if (heightTree == null)
+				throw ThrowUtil.NoDocumentAssigned();
+			return heightTree.CollapseText(start, end);
+		}
+		
+		/// <summary>
+		/// Gets the height of the document.
+		/// </summary>
+		public double DocumentHeight {
+			get {
+				// return 0 if there is no document = no heightTree
+				return heightTree != null ? heightTree.TotalHeight : 0;
+			}
+		}
+		
+		/// <summary>
+		/// Gets the document line at the specified visual position.
+		/// </summary>
+		public DocumentLine GetDocumentLineByVisualTop(double visualTop)
+		{
+			VerifyAccess();
+			if (heightTree == null)
+				throw ThrowUtil.NoDocumentAssigned();
+			return heightTree.GetLineByVisualPosition(visualTop);
+		}
+		
+		/// <inheritdoc/>
+		protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
+		{
+			base.OnPropertyChanged(e);
+			if (TextFormatterFactory.PropertyChangeAffectsTextFormatter(e.Property)) {
+				// first, create the new text formatter:
+				RecreateTextFormatter();
+				// changing text formatter requires recreating the cached elements
+				RecreateCachedElements();
+				// and we need to re-measure the font metrics:
+				InvalidateDefaultTextMetrics();
+			} else if (e.Property == Control.ForegroundProperty
+			           || e.Property == TextView.NonPrintableCharacterBrushProperty
+			           || e.Property == TextView.LinkTextBackgroundBrushProperty
+			           || e.Property == TextView.LinkTextForegroundBrushProperty)
+			{
+				// changing brushes requires recreating the cached elements
+				RecreateCachedElements();
+				Redraw();
+			}
+			if (e.Property == Control.FontFamilyProperty
+			    || e.Property == Control.FontSizeProperty
+			    || e.Property == Control.FontStretchProperty
+			    || e.Property == Control.FontStyleProperty
+			    || e.Property == Control.FontWeightProperty)
+			{
+				// changing font properties requires recreating cached elements
+				RecreateCachedElements();
+				// and we need to re-measure the font metrics:
+				InvalidateDefaultTextMetrics();
+				Redraw();
+			}
+			if (e.Property == ColumnRulerPenProperty) {
+				columnRulerRenderer.SetRuler(this.Options.ColumnRulerPosition, this.ColumnRulerPen);
+			}
+		}
+		
+		/// <summary>
+		/// The pen used to draw the column ruler.
+		/// <seealso cref="TextEditorOptions.ShowColumnRuler"/>
+		/// </summary>
+		public static readonly DependencyProperty ColumnRulerPenProperty =
+			DependencyProperty.Register("ColumnRulerBrush", typeof(Pen), typeof(TextView),
+			                            new FrameworkPropertyMetadata(CreateFrozenPen(Brushes.LightGray)));
+		
+		static Pen CreateFrozenPen(SolidColorBrush brush)
+		{
+			Pen pen = new Pen(brush, 1);
+			pen.Freeze();
+			return pen;
+		}
+		
+		/// <summary>
+		/// Gets/Sets the pen used to draw the column ruler.
+		/// <seealso cref="TextEditorOptions.ShowColumnRuler"/>
+		/// </summary>
+		public Pen ColumnRulerPen {
+			get { return (Pen)GetValue(ColumnRulerPenProperty); }
+			set { SetValue(ColumnRulerPenProperty, value); }
+		}
+	}
+}