Code snippets: implemented input handling and background renderer.

Added support for "stacked" input handlers.

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@5065 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/TextMarkerService.cs

@@ -155,6 +155,7 @@ namespace ICSharpCode.AvalonEdit.AddIn
 			foreach (TextMarker marker in markers.FindOverlappingSegments(viewStart, viewEnd - viewStart)) {
 				if (marker.BackgroundColor != null) {
 					BackgroundGeometryBuilder geoBuilder = new BackgroundGeometryBuilder();
+					geoBuilder.CornerRadius = 3;
 					geoBuilder.AddSegment(textView, marker);
 					Geometry geometry = geoBuilder.CreateGeometry();
 					if (geometry != null) {

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/CodeCompletion/CompletionWindow.cs

@@ -106,7 +106,7 @@ namespace ICSharpCode.AvalonEdit.CodeCompletion
 			this.TextArea.MouseWheel += textArea_MouseWheel;
 			this.TextArea.PreviewTextInput += textArea_PreviewTextInput;
 			myInputHandler = new InputHandler(this);
-			this.TextArea.ActiveInputHandler = myInputHandler;
+			this.TextArea.PushStackedInputHandler(myInputHandler);
 		}
 		
 		/// <inheritdoc/>
@@ -116,8 +116,7 @@ namespace ICSharpCode.AvalonEdit.CodeCompletion
 			this.TextArea.MouseWheel -= textArea_MouseWheel;
 			this.TextArea.PreviewTextInput -= textArea_PreviewTextInput;
 			base.DetachEvents();
-			if (this.TextArea.ActiveInputHandler == myInputHandler)
-				this.TextArea.ActiveInputHandler = this.TextArea.DefaultInputHandler;
+			this.TextArea.PopStackedInputHandler(myInputHandler);
 		}
 		
 		#region InputHandler
@@ -142,14 +141,11 @@ namespace ICSharpCode.AvalonEdit.CodeCompletion
 			
 			public void Attach()
 			{
-				this.TextArea.DefaultInputHandler.Attach();
 			}
 			
 			public void Detach()
 			{
-				this.TextArea.DefaultInputHandler.Detach();
-				// close with dispatcher so we don't get reentrance problems in input handler Detach/Attach
-				window.Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(window.Close));
+				window.Close();
 			}
 		}
 		#endregion

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/LineNumberMargin.cs

@@ -104,7 +104,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 			OnDocumentLineCountChanged();
 		}
 		
-		/// <inheritdoc/>
+		/// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
 		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
 		{
 			if (managerType == typeof(TextDocumentWeakEventManager.LineCountChanged)) {

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/TextArea.cs

@@ -6,6 +6,7 @@
 // </file>
 
 using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.ComponentModel;
@@ -83,24 +84,39 @@ namespace ICSharpCode.AvalonEdit.Editing
 		/// <summary>
 		/// Gets the default input handler.
 		/// </summary>
+		/// <remarks><inheritdoc cref="ITextAreaInputHandler"/></remarks>
 		public TextAreaDefaultInputHandler DefaultInputHandler { get; private set; }
 		
 		ITextAreaInputHandler activeInputHandler;
+		bool isChangingInputHandler;
 		
 		/// <summary>
 		/// Gets/Sets the active input handler.
+		/// This property does not return currently active stacked input handlers. Setting this property detached all stacked input handlers.
 		/// </summary>
+		/// <remarks><inheritdoc cref="ITextAreaInputHandler"/></remarks>
 		public ITextAreaInputHandler ActiveInputHandler {
 			get { return activeInputHandler; }
 			set {
 				if (value != null && value.TextArea != this)
 					throw new ArgumentException("The input handler was created for a different text area than this one.");
+				if (isChangingInputHandler)
+					throw new InvalidOperationException("Cannot set ActiveInputHandler recursively");
 				if (activeInputHandler != value) {
-					if (activeInputHandler != null)
-						activeInputHandler.Detach();
-					activeInputHandler = value;
-					if (value != null)
-						value.Attach();
+					isChangingInputHandler = true;
+					try {
+						// pop the whole stack
+						PopStackedInputHandler(stackedInputHandlers.LastOrDefault());
+						Debug.Assert(stackedInputHandlers.IsEmpty);
+						
+						if (activeInputHandler != null)
+							activeInputHandler.Detach();
+						activeInputHandler = value;
+						if (value != null)
+							value.Attach();
+					} finally {
+						isChangingInputHandler = false;
+					}
 					if (ActiveInputHandlerChanged != null)
 						ActiveInputHandlerChanged(this, EventArgs.Empty);
 				}
@@ -111,6 +127,46 @@ namespace ICSharpCode.AvalonEdit.Editing
 		/// Occurs when the ActiveInputHandler property changes.
 		/// </summary>
 		public event EventHandler ActiveInputHandlerChanged;
+		
+		ImmutableStack<ITextAreaInputHandler> stackedInputHandlers = ImmutableStack<ITextAreaInputHandler>.Empty;
+		
+		/// <summary>
+		/// Gets the list of currently active stacked input handlers.
+		/// </summary>
+		/// <remarks><inheritdoc cref="ITextAreaInputHandler"/></remarks>
+		public ImmutableStack<ITextAreaInputHandler> StackedInputHandlers {
+			get { return stackedInputHandlers; }
+		}
+		
+		/// <summary>
+		/// Pushes an input handler onto the list of stacked input handlers.
+		/// </summary>
+		/// <remarks><inheritdoc cref="ITextAreaInputHandler"/></remarks>
+		public void PushStackedInputHandler(ITextAreaInputHandler inputHandler)
+		{
+			if (inputHandler == null)
+				throw new ArgumentNullException("inputHandler");
+			stackedInputHandlers = stackedInputHandlers.Push(inputHandler);
+			inputHandler.Attach();
+		}
+		
+		/// <summary>
+		/// Pops the stacked input handler (and all input handlers above it).
+		/// If <paramref name="inputHandler"/> is not found in the currently stacked input handlers, or is null, this method
+		/// does nothing.
+		/// </summary>
+		/// <remarks><inheritdoc cref="ITextAreaInputHandler"/></remarks>
+		public void PopStackedInputHandler(ITextAreaInputHandler inputHandler)
+		{
+			if (stackedInputHandlers.Any(i => i == inputHandler)) {
+				ITextAreaInputHandler oldHandler;
+				do {
+					oldHandler = stackedInputHandlers.Peek();
+					stackedInputHandlers = stackedInputHandlers.Pop();
+					oldHandler.Detach();
+				} while (oldHandler != inputHandler);
+			}
+		}
 		#endregion
 		
 		#region Document property
@@ -202,7 +258,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 		#endregion
 		
 		#region ReceiveWeakEvent
-		/// <inheritdoc/>
+		/// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
 		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
 		{
 			if (managerType == typeof(TextDocumentWeakEventManager.Changing)) {

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Editing/TextAreaInputHandler.cs

@@ -16,6 +16,19 @@ namespace ICSharpCode.AvalonEdit.Editing
 	/// <summary>
 	/// A set of input bindings and event handlers for the text area.
 	/// </summary>
+	/// <remarks>
+	/// <para>
+	/// There is one active input handler per text area (<see cref="Editing.TextArea.ActiveInputHandler"/>), plus
+	/// a number of active stacked input handlers.
+	/// </para>
+	/// <para>
+	/// The text area also stores a reference to a default input handler, but that is not necessarily active.
+	/// </para>
+	/// <para>
+	/// Stacked input handlers work in addition to the set of currently active handlers (without detaching them).
+	/// They are detached in the reverse order of being attached.
+	/// </para>
+	/// </remarks>
 	public interface ITextAreaInputHandler
 	{
 		/// <summary>
@@ -39,6 +52,7 @@ namespace ICSharpCode.AvalonEdit.Editing
 	/// <summary>
 	/// Default-implementation of <see cref="ITextAreaInputHandler"/>.
 	/// </summary>
+	/// <remarks><inheritdoc cref="ITextAreaInputHandler"/></remarks>
 	public class TextAreaInputHandler : ITextAreaInputHandler
 	{
 		readonly ObserveAddRemoveCollection<CommandBinding> commandBindings;

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Folding/FoldingManager.cs

@@ -48,7 +48,7 @@ namespace ICSharpCode.AvalonEdit.Folding
 		#endregion
 		
 		#region ReceiveWeakEvent
-		/// <inheritdoc/>
+		/// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
 		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
 		{
 			if (managerType == typeof(TextDocumentWeakEventManager.Changed)) {

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Highlighting/HighlightingColorizer.cs

@@ -43,7 +43,7 @@ namespace ICSharpCode.AvalonEdit.Highlighting
 			OnDocumentChanged();
 		}
 		
-		/// <inheritdoc/>
+		/// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
 		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
 		{
 			if (managerType == typeof(TextViewWeakEventManager.DocumentChanged)) {

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/ICSharpCode.AvalonEdit.csproj

@@ -278,6 +278,7 @@
       <DependentUpon>VisualLine.cs</DependentUpon>
     </Compile>
     <Compile Include="Snippets\IActiveElement.cs" />
+    <Compile Include="Snippets\SnippetInputHandler.cs" />
     <Compile Include="Snippets\Snippet.cs" />
     <Compile Include="Snippets\SnippetBoundElement.cs" />
     <Compile Include="Snippets\SnippetCaretElement.cs" />
@@ -318,7 +319,6 @@
     <Compile Include="Utils\Empty.cs" />
     <Compile Include="Utils\ExtensionMethods.cs" />
     <Compile Include="Utils\FileReader.cs" />
-    <Compile Include="Utils\IFreezable.cs" />
     <Compile Include="Utils\ImmutableStack.cs" />
     <Compile Include="Utils\NullSafeCollection.cs" />
     <Compile Include="Utils\ObserveAddRemoveCollection.cs" />

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Rendering/BackgroundGeometryBuilder.cs

@@ -22,7 +22,7 @@ namespace ICSharpCode.AvalonEdit.Rendering
 	/// </summary>
 	public sealed class BackgroundGeometryBuilder
 	{
-		double cornerRadius = 3;
+		double cornerRadius;
 		
 		/// <summary>
 		/// Gets/sets the radius of the rounded corners.

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/IActiveElement.cs

@@ -6,6 +6,8 @@
 // </file>
 
 using System;
+using System.Windows.Media;
+using ICSharpCode.AvalonEdit.Document;
 
 namespace ICSharpCode.AvalonEdit.Snippets
 {
@@ -23,5 +25,15 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		/// Called when the interactive mode is deactivated.
 		/// </summary>
 		void Deactivate();
+		
+		/// <summary>
+		/// Gets whether this element is editable (the user will be able to select it with Tab).
+		/// </summary>
+		bool IsEditable { get; }
+		
+		/// <summary>
+		/// Gets the segment associated with this element. May be null.
+		/// </summary>
+		ISegment Segment { get; }
 	}
 }

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/InsertionContext.cs

@@ -7,6 +7,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Windows;
 using System.Windows.Input;
 
 using ICSharpCode.AvalonEdit.Document;
@@ -18,8 +19,19 @@ namespace ICSharpCode.AvalonEdit.Snippets
 	/// <summary>
 	/// Represents the context of a snippet insertion.
 	/// </summary>
-	public class InsertionContext
+	public class InsertionContext : IWeakEventListener
 	{
+		enum Status
+		{
+			Insertion,
+			RaisingInsertionCompleted,
+			Interactive,
+			RaisingDeactivated,
+			Deactivated
+		}
+		
+		Status currentStatus = Status.Insertion;
+		
 		/// <summary>
 		/// Creates a new InsertionContext instance.
 		/// </summary>
@@ -30,10 +42,12 @@ namespace ICSharpCode.AvalonEdit.Snippets
 			this.TextArea = textArea;
 			this.Document = textArea.Document;
 			this.InsertionPosition = insertionPosition;
+			this.startPosition = insertionPosition;
 			
 			DocumentLine startLine = this.Document.GetLineByOffset(insertionPosition);
 			ISegment indentation = TextUtilities.GetWhitespaceAfter(this.Document, startLine.Offset);
 			this.Indentation = Document.GetText(indentation.Offset, Math.Min(indentation.EndOffset, insertionPosition) - indentation.Offset);
+			this.Tab = textArea.Options.IndentationString;
 			
 			this.LineTerminator = NewLineFinder.GetNewLineFromDocument(this.Document, startLine.LineNumber);
 		}
@@ -53,6 +67,11 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		/// </summary>
 		public string Indentation { get; private set; }
 		
+		/// <summary>
+		/// Gets the indentation string for a single indentation level.
+		/// </summary>
+		public string Tab { get; private set; }
+		
 		/// <summary>
 		/// Gets the line terminator at the insertion position.
 		/// </summary>
@@ -63,6 +82,9 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		/// </summary>
 		public int InsertionPosition { get; set; }
 		
+		readonly int startPosition;
+		AnchorSegment wholeSnippetAnchor;
+		
 		/// <summary>
 		/// Inserts text at the insertion position and advances the insertion position.
 		/// </summary>
@@ -70,18 +92,25 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		{
 			if (text == null)
 				throw new ArgumentNullException("text");
-			int textOffset = 0;
-			SimpleSegment segment;
-			while ((segment = NewLineFinder.NextNewLine(text, textOffset)) != SimpleSegment.Invalid) {
-				string insertString = text.Substring(textOffset, segment.Offset - textOffset)
-					+ this.LineTerminator + this.Indentation;
-				this.Document.Insert(InsertionPosition, insertString);
-				this.InsertionPosition += insertString.Length;
-				textOffset = segment.EndOffset;
+			if (currentStatus != Status.Insertion)
+				throw new InvalidOperationException();
+			
+			text = text.Replace("\t", this.Tab);
+			
+			using (this.Document.RunUpdate()) {
+				int textOffset = 0;
+				SimpleSegment segment;
+				while ((segment = NewLineFinder.NextNewLine(text, textOffset)) != SimpleSegment.Invalid) {
+					string insertString = text.Substring(textOffset, segment.Offset - textOffset)
+						+ this.LineTerminator + this.Indentation;
+					this.Document.Insert(InsertionPosition, insertString);
+					this.InsertionPosition += insertString.Length;
+					textOffset = segment.EndOffset;
+				}
+				string remainingInsertString = text.Substring(textOffset);
+				this.Document.Insert(InsertionPosition, remainingInsertString);
+				this.InsertionPosition += remainingInsertString.Length;
 			}
-			string remainingInsertString = text.Substring(textOffset);
-			this.Document.Insert(InsertionPosition, remainingInsertString);
-			this.InsertionPosition += remainingInsertString.Length;
 		}
 		
 		Dictionary<SnippetElement, IActiveElement> elementMap = new Dictionary<SnippetElement, IActiveElement>();
@@ -99,6 +128,8 @@ namespace ICSharpCode.AvalonEdit.Snippets
 				throw new ArgumentNullException("owner");
 			if (element == null)
 				throw new ArgumentNullException("element");
+			if (currentStatus != Status.Insertion)
+				throw new InvalidOperationException();
 			elementMap.Add(owner, element);
 			registeredElements.Add(element);
 		}
@@ -117,39 +148,53 @@ namespace ICSharpCode.AvalonEdit.Snippets
 				return null;
 		}
 		
-		bool insertionCompleted;
+		/// <summary>
+		/// Gets the list of active elements.
+		/// </summary>
+		public IEnumerable<IActiveElement> ActiveElements {
+			get { return registeredElements; }
+		}
 		
 		/// <summary>
 		/// Calls the <see cref="IActiveElement.OnInsertionCompleted"/> method on all registered active elements
 		/// and raises the <see cref="InsertionCompleted"/> event.
 		/// </summary>
+		/// <param name="e">The EventArgs to use</param>
 		[System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Design", "CA1030:UseEventsWhereAppropriate",
 		                                                 Justification="There is an event and this method is raising it.")]
-		public void RaiseInsertionCompleted()
+		public void RaiseInsertionCompleted(EventArgs e)
 		{
+			if (currentStatus != Status.Insertion)
+				throw new InvalidOperationException();
+			if (e == null)
+				e = EventArgs.Empty;
+			
+			currentStatus = Status.RaisingInsertionCompleted;
+			int endPosition = this.InsertionPosition;
+			this.wholeSnippetAnchor = new AnchorSegment(Document, startPosition, endPosition - startPosition);
+			TextDocumentWeakEventManager.UpdateFinished.AddListener(Document, this);
+			
 			foreach (IActiveElement element in registeredElements) {
 				element.OnInsertionCompleted();
 			}
 			if (InsertionCompleted != null)
-				InsertionCompleted(this, EventArgs.Empty);
-			insertionCompleted = true;
+				InsertionCompleted(this, e);
+			currentStatus = Status.Interactive;
 			if (registeredElements.Count == 0) {
 				// deactivate immediately if there are no interactive elements
-				Deactivate();
+				Deactivate(EventArgs.Empty);
 			} else {
-				// register Escape key handler
-				TextArea.KeyDown += TextArea_KeyDown;
-			}
-		}
-
-		void TextArea_KeyDown(object sender, KeyEventArgs e)
-		{
-			if (e.Key == Key.Escape) {
-				Deactivate();
-				e.Handled = true;
+				myInputHandler = new SnippetInputHandler(this);
+				foreach (ITextAreaInputHandler h in TextArea.StackedInputHandlers) {
+					if (h is SnippetInputHandler)
+						TextArea.PopStackedInputHandler(h);
+				}
+				TextArea.PushStackedInputHandler(myInputHandler);
 			}
 		}
 		
+		SnippetInputHandler myInputHandler;
+		
 		/// <summary>
 		/// Occurs when the all snippet elements have been inserted.
 		/// </summary>
@@ -158,21 +203,48 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		/// <summary>
 		/// Calls the <see cref="IActiveElement.Deactivate"/> method on all registered active elements.
 		/// </summary>
-		public void Deactivate()
+		/// <param name="e">The EventArgs to use</param>
+		public void Deactivate(EventArgs e)
 		{
-			if (!insertionCompleted)
+			if (currentStatus == Status.Deactivated || currentStatus == Status.RaisingDeactivated)
+				return;
+			if (currentStatus != Status.Interactive)
 				throw new InvalidOperationException("Cannot call Deactivate() until RaiseInsertionCompleted() has finished.");
-			TextArea.KeyDown -= TextArea_KeyDown;
+			if (e == null)
+				e = EventArgs.Empty;
+			
+			TextDocumentWeakEventManager.UpdateFinished.RemoveListener(Document, this);
+			currentStatus = Status.RaisingDeactivated;
+			TextArea.PopStackedInputHandler(myInputHandler);
 			foreach (IActiveElement element in registeredElements) {
 				element.Deactivate();
 			}
 			if (Deactivated != null)
-				Deactivated(this, EventArgs.Empty);
+				Deactivated(this, e);
+			currentStatus = Status.Deactivated;
 		}
 		
 		/// <summary>
 		/// Occurs when the interactive mode is deactivated.
 		/// </summary>
 		public event EventHandler Deactivated;
+		
+		bool IWeakEventListener.ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+		{
+			return ReceiveWeakEvent(managerType, sender, e);
+		}
+		
+		/// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
+		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
+		{
+			if (managerType == typeof(TextDocumentWeakEventManager.UpdateFinished)) {
+				// Deactivate if snippet is deleted. This is necessary for correctly leaving interactive
+				// mode if Undo is pressed after a snippet insertion.
+				if (wholeSnippetAnchor.Length == 0)
+					Deactivate(e);
+				return true;
+			}
+			return false;
+		}
 	}
 }

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/Snippet.cs

@@ -25,11 +25,10 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		{
 			if (textArea == null)
 				throw new ArgumentNullException("textArea");
-			Freeze();
 			InsertionContext context = new InsertionContext(textArea, textArea.Caret.Offset);
 			using (context.Document.RunUpdate()) {
 				Insert(context);
-				context.RaiseInsertionCompleted();
+				context.RaiseInsertionCompleted(EventArgs.Empty);
 			}
 		}
 	}

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/SnippetBoundElement.cs

@@ -23,10 +23,7 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		/// </summary>
 		public SnippetReplaceableTextElement TargetElement {
 			get { return targetElement; }
-			set {
-				CheckBeforeMutation();
-				targetElement = value;
-			}
+			set { targetElement = value; }
 		}
 		
 		/// <summary>
@@ -58,7 +55,7 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		InsertionContext context;
 		SnippetReplaceableTextElement targetSnippetElement;
 		SnippetBoundElement boundElement;
-		IReplaceableActiveElement targetElement;
+		internal IReplaceableActiveElement targetElement;
 		AnchorSegment segment;
 		
 		public BoundActiveElement(InsertionContext context, SnippetReplaceableTextElement targetSnippetElement, SnippetBoundElement boundElement, AnchorSegment segment)
@@ -79,18 +76,31 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		
 		void targetElement_TextChanged(object sender, EventArgs e)
 		{
-			int offset = segment.Offset;
-			int length = segment.Length;
-			string text = boundElement.ConvertText(targetElement.Text);
-			context.Document.Replace(offset, length, text);
-			if (length == 0) {
-				// replacing an empty anchor segment with text won't enlarge it, so we have to recreate it
-				segment = new AnchorSegment(context.Document,  offset, text.Length);
+			// Don't copy text if the segments overlap (we would get an endless loop).
+			// This can happen if the user deletes the text between the replaceable element and the bound element.
+			if (segment.GetOverlap(targetElement.Segment) == SimpleSegment.Invalid) {
+				int offset = segment.Offset;
+				int length = segment.Length;
+				string text = boundElement.ConvertText(targetElement.Text);
+				context.Document.Replace(offset, length, text);
+				if (length == 0) {
+					// replacing an empty anchor segment with text won't enlarge it, so we have to recreate it
+					segment = new AnchorSegment(context.Document, offset, text.Length);
+				}
 			}
 		}
 		
 		public void Deactivate()
 		{
 		}
+		
+		
+		public bool IsEditable {
+			get { return false; }
+		}
+		
+		public ISegment Segment {
+			get { return segment; }
+		}
 	}
 }

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/SnippetCaretElement.cs

@@ -6,6 +6,7 @@
 // </file>
 
 using System;
+using System.Windows.Input;
 using ICSharpCode.AvalonEdit.Document;
 
 namespace ICSharpCode.AvalonEdit.Snippets
@@ -13,6 +14,7 @@ namespace ICSharpCode.AvalonEdit.Snippets
 	/// <summary>
 	/// Sets the caret position after interactive mode has finished.
 	/// </summary>
+	[Serializable]
 	public class SnippetCaretElement : SnippetElement
 	{
 		/// <inheritdoc/>
@@ -20,8 +22,11 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		{
 			TextAnchor pos = context.Document.CreateAnchor(context.InsertionPosition);
 			pos.SurviveDeletion = true;
-			context.Deactivated += delegate {
-				context.TextArea.Caret.Offset = pos.Offset;
+			context.Deactivated += (sender, e) => {
+				KeyEventArgs ke = e as KeyEventArgs;
+				if (ke != null && ke.Key == Key.Return) {
+					context.TextArea.Caret.Offset = pos.Offset;
+				}
 			};
 		}
 	}

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/SnippetContainerElement.cs

@@ -18,7 +18,7 @@ namespace ICSharpCode.AvalonEdit.Snippets
 	[Serializable]
 	public class SnippetContainerElement : SnippetElement
 	{
-		FreezableNullSafeCollection<SnippetElement> elements = new FreezableNullSafeCollection<SnippetElement>();
+		NullSafeCollection<SnippetElement> elements = new NullSafeCollection<SnippetElement>();
 		
 		/// <summary>
 		/// Gets the list of child elements.
@@ -27,13 +27,6 @@ namespace ICSharpCode.AvalonEdit.Snippets
 			get { return elements; }
 		}
 		
-		/// <inheritdoc/>
-		protected override void FreezeInternal()
-		{
-			elements.Freeze();
-			base.FreezeInternal();
-		}
-		
 		/// <inheritdoc/>
 		public override void Insert(InsertionContext context)
 		{

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/SnippetElement.cs

@@ -16,48 +16,8 @@ namespace ICSharpCode.AvalonEdit.Snippets
 	/// An element inside a snippet.
 	/// </summary>
 	[Serializable]
-	public abstract class SnippetElement : IFreezable
+	public abstract class SnippetElement
 	{
-		// TODO: think about removing IFreezable, it may not be required after all
-		
-		#region IFreezable infrastructure
-		bool isFrozen;
-		
-		/// <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()
-		{
-			if (!isFrozen) {
-				FreezeInternal();
-				isFrozen = true;
-			}
-		}
-		
-		/// <summary>
-		/// Override this method to freeze child elements.
-		/// </summary>
-		protected virtual void FreezeInternal()
-		{
-		}
-		
-		/// <summary>
-		/// Throws an exception if this instance is frozen.
-		/// </summary>
-		protected void CheckBeforeMutation()
-		{
-			if (isFrozen)
-				throw new InvalidOperationException("Cannot mutate frozen " + GetType().Name);
-		}
-		#endregion
-		
 		/// <summary>
 		/// Performs insertion of the snippet.
 		/// </summary>

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/SnippetInputHandler.cs

@@ -0,0 +1,83 @@
+// <file>
+//     <copyright see="prj:///doc/copyright.txt"/>
+//     <license see="prj:///doc/license.txt"/>
+//     <owner name="Daniel Grunwald"/>
+//     <version>$Revision$</version>
+// </file>
+
+using System;
+using System.Linq;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Windows.Input;
+
+using ICSharpCode.AvalonEdit.Document;
+using ICSharpCode.AvalonEdit.Editing;
+
+namespace ICSharpCode.AvalonEdit.Snippets
+{
+	sealed class SnippetInputHandler : ITextAreaInputHandler
+	{
+		readonly InsertionContext context;
+		
+		public SnippetInputHandler(InsertionContext context)
+		{
+			this.context = context;
+		}
+		
+		public TextArea TextArea {
+			get { return context.TextArea; }
+		}
+		
+		public void Attach()
+		{
+			TextArea.PreviewKeyDown += TextArea_PreviewKeyDown;
+			
+			SelectElement(FindNextEditableElement(-1, false));
+		}
+		
+		void SelectElement(IActiveElement element)
+		{
+			if (element != null) {
+				TextArea.Selection = new SimpleSelection(element.Segment);
+				TextArea.Caret.Offset = element.Segment.EndOffset;
+			}
+		}
+		
+		public void Detach()
+		{
+			TextArea.PreviewKeyDown -= TextArea_PreviewKeyDown;
+			context.Deactivate(EventArgs.Empty);
+		}
+		
+		void TextArea_PreviewKeyDown(object sender, KeyEventArgs e)
+		{
+			if (e.Key == Key.Escape || e.Key == Key.Return) {
+				context.Deactivate(e);
+				e.Handled = true;
+			} else if (e.Key == Key.Tab) {
+				bool backwards = e.KeyboardDevice.Modifiers == ModifierKeys.Shift;
+				SelectElement(FindNextEditableElement(TextArea.Caret.Offset, backwards));
+				e.Handled = true;
+			}
+		}
+		
+		IActiveElement FindNextEditableElement(int offset, bool backwards)
+		{
+			IEnumerable<IActiveElement> elements = context.ActiveElements.Where(e => e.IsEditable && e.Segment != null);
+			if (backwards) {
+				elements = elements.Reverse();
+				foreach (IActiveElement element in elements) {
+					if (offset > element.Segment.EndOffset)
+						return element;
+				}
+			} else {
+				foreach (IActiveElement element in elements) {
+					if (offset < element.Segment.Offset)
+						return element;
+				}
+			}
+			return elements.FirstOrDefault();
+		}
+	}
+}

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/SnippetReplaceableTextElement.cs

@@ -7,9 +7,12 @@
 
 using System;
 using System.Windows;
+using System.Windows.Media;
 using System.Windows.Threading;
+using System.Linq;
 
 using ICSharpCode.AvalonEdit.Document;
+using ICSharpCode.AvalonEdit.Rendering;
 
 namespace ICSharpCode.AvalonEdit.Snippets
 {
@@ -61,7 +64,7 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		
 		void AnchorDeleted(object sender, EventArgs e)
 		{
-			context.Deactivate();
+			context.Deactivate(EventArgs.Empty);
 		}
 		
 		public void OnInsertionCompleted()
@@ -76,18 +79,44 @@ namespace ICSharpCode.AvalonEdit.Snippets
 			end.Deleted += AnchorDeleted;
 			
 			// Be careful with references from the document to the editing/snippet layer - use weak events
-			// to prevent memory leaks when text areas get dropped from the UI while the snippet is active.
+			// to prevent memory leaks when the text area control gets dropped from the UI while the snippet is active.
 			// The InsertionContext will keep us alive as long as the snippet is in interactive mode.
 			TextDocumentWeakEventManager.TextChanged.AddListener(context.Document, this);
 			
+			background = new Renderer { Layer = KnownLayer.Background, element = this };
+			foreground = new Renderer { Layer = KnownLayer.Text, element = this };
+			context.TextArea.TextView.BackgroundRenderers.Add(background);
+			context.TextArea.TextView.BackgroundRenderers.Add(foreground);
+			context.TextArea.Caret.PositionChanged += Caret_PositionChanged;
+			Caret_PositionChanged(null, null);
+			
 			this.Text = GetText();
 		}
-		
+
 		public void Deactivate()
 		{
 			TextDocumentWeakEventManager.TextChanged.RemoveListener(context.Document, this);
+			context.TextArea.TextView.BackgroundRenderers.Remove(background);
+			context.TextArea.TextView.BackgroundRenderers.Remove(foreground);
+			context.TextArea.Caret.PositionChanged -= Caret_PositionChanged;
+		}
+		
+		bool isCaretInside;
+		
+		void Caret_PositionChanged(object sender, EventArgs e)
+		{
+			ISegment s = this.Segment;
+			if (s != null) {
+				bool newIsCaretInside = s.Contains(context.TextArea.Caret.Offset);
+				if (newIsCaretInside != isCaretInside) {
+					isCaretInside = newIsCaretInside;
+					context.TextArea.TextView.InvalidateLayer(foreground.Layer);
+				}
+			}
 		}
 		
+		Renderer background, foreground;
+		
 		public string Text { get; private set; }
 		
 		string GetText()
@@ -113,5 +142,68 @@ namespace ICSharpCode.AvalonEdit.Snippets
 			}
 			return false;
 		}
+		
+		public bool IsEditable {
+			get { return true; }
+		}
+		
+		public ISegment Segment {
+			get {
+				if (start.IsDeleted || end.IsDeleted)
+					return null;
+				else
+					return new SimpleSegment(start.Offset, Math.Max(0, end.Offset - start.Offset));
+			}
+		}
+		
+		sealed class Renderer : IBackgroundRenderer
+		{
+			static readonly Brush backgroundBrush = CreateBackgroundBrush();
+			static readonly Pen activeBorderPen = CreateBorderPen();
+			
+			static Brush CreateBackgroundBrush()
+			{
+				SolidColorBrush b = new SolidColorBrush(Colors.LimeGreen);
+				b.Opacity = 0.4;
+				b.Freeze();
+				return b;
+			}
+			
+			static Pen CreateBorderPen()
+			{
+				Pen p = new Pen(Brushes.Black, 1);
+				p.DashStyle = DashStyles.Dot;
+				p.Freeze();
+				return p;
+			}
+			
+			internal ReplaceableActiveElement element;
+			
+			public KnownLayer Layer { get; set; }
+			
+			public void Draw(TextView textView, System.Windows.Media.DrawingContext drawingContext)
+			{
+				ISegment s = element.Segment;
+				if (s != null) {
+					BackgroundGeometryBuilder geoBuilder = new BackgroundGeometryBuilder();
+					if (Layer == KnownLayer.Background) {
+						geoBuilder.AddSegment(textView, s);
+						drawingContext.DrawGeometry(backgroundBrush, null, geoBuilder.CreateGeometry());
+					} else {
+						// draw foreground only if active
+						if (element.isCaretInside) {
+							geoBuilder.AddSegment(textView, s);
+							foreach (BoundActiveElement boundElement in element.context.ActiveElements.OfType<BoundActiveElement>()) {
+								if (boundElement.targetElement == element) {
+									geoBuilder.AddSegment(textView, boundElement.Segment);
+									geoBuilder.CloseFigure();
+								}
+							}
+							drawingContext.DrawGeometry(null, activeBorderPen, geoBuilder.CreateGeometry());
+						}
+					}
+				}
+			}
+		}
 	}
 }

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Snippets/SnippetTextElement.cs

@@ -23,10 +23,7 @@ namespace ICSharpCode.AvalonEdit.Snippets
 		/// </summary>
 		public string Text {
 			get { return text; }
-			set {
-				CheckBeforeMutation();
-				text = value;
-			}
+			set { text = value; }
 		}
 		
 		/// <inheritdoc/>

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/TextEditor.cs

@@ -178,7 +178,7 @@ namespace ICSharpCode.AvalonEdit
 			OnOptionChanged(new PropertyChangedEventArgs(null));
 		}
 		
-		/// <inheritdoc/>
+		/// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
 		protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
 		{
 			if (managerType == typeof(PropertyChangedWeakEventManager)) {

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/Utils/IFreezable.cs

@@ -1,72 +0,0 @@
-// <file>
-//     <copyright see="prj:///doc/copyright.txt"/>
-//     <license see="prj:///doc/license.txt"/>
-//     <owner name="Daniel Grunwald"/>
-//     <version>$Revision$</version>
-// </file>
-
-using System;
-
-namespace ICSharpCode.AvalonEdit.Utils
-{
-	interface IFreezable
-	{
-		/// <summary>
-		/// Gets if this instance is frozen. Frozen instances are immutable and thus thread-safe.
-		/// </summary>
-		bool IsFrozen { get; }
-		
-		/// <summary>
-		/// Freezes this instance.
-		/// </summary>
-		void Freeze();
-	}
-	
-	[Serializable]
-	sealed class FreezableNullSafeCollection<T> : NullSafeCollection<T>, IFreezable where T : class, IFreezable
-	{
-		bool isFrozen;
-		
-		public bool IsFrozen { get { return isFrozen; } }
-		
-		public void Freeze()
-		{
-			if (!isFrozen) {
-				foreach (T item in this) {
-					item.Freeze();
-				}
-				isFrozen = true;
-			}
-		}
-		
-		void CheckBeforeMutation()
-		{
-			if (isFrozen)
-				throw new InvalidOperationException("Cannot mutate frozen " + GetType().Name);
-		}
-		
-		protected override void ClearItems()
-		{
-			this.CheckBeforeMutation();
-			base.ClearItems();
-		}
-		
-		protected override void InsertItem(int index, T item)
-		{
-			this.CheckBeforeMutation();
-			base.InsertItem(index, item);
-		}
-		
-		protected override void RemoveItem(int index)
-		{
-			this.CheckBeforeMutation();
-			base.RemoveItem(index);
-		}
-		
-		protected override void SetItem(int index, T item)
-		{
-			this.CheckBeforeMutation();
-			base.SetItem(index, item);
-		}
-	}
-}