source: branches/2913_MatlabScriptProblemInstanceProvider/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/TextEditor.cs @ 16752

// Copyright (c) 2014 AlphaSierraPapa for the SharpDevelop Team
// 
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
// without restriction, including without limitation the rights to use, copy, modify, merge,
// publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, subject to the following conditions:
// 
// The above copyright notice and this permission notice shall be included in all copies or
// substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
// INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
// PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
// FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

using System;
using System.ComponentModel;
using System.IO;
using System.Linq;
using System.Text;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Data;
using System.Windows.Input;
using System.Windows.Markup;
using System.Windows.Media;
using System.Windows.Shapes;
using System.Windows.Threading;

using ICSharpCode.AvalonEdit.Document;
using ICSharpCode.AvalonEdit.Editing;
using ICSharpCode.AvalonEdit.Highlighting;
using ICSharpCode.AvalonEdit.Rendering;
using ICSharpCode.AvalonEdit.Utils;

namespace ICSharpCode.AvalonEdit
{
  /// <summary>
  /// The text editor control.
  /// Contains a scrollable TextArea.
  /// </summary>
  [Localizability(LocalizationCategory.Text), ContentProperty("Text")]
  public class TextEditor : Control, ITextEditorComponent, IServiceProvider, IWeakEventListener
  {
    #region Constructors
    static TextEditor()
    {
      DefaultStyleKeyProperty.OverrideMetadata(typeof(TextEditor),
                                               new FrameworkPropertyMetadata(typeof(TextEditor)));
      FocusableProperty.OverrideMetadata(typeof(TextEditor),
                                         new FrameworkPropertyMetadata(Boxes.True));
    }
    
    /// <summary>
    /// Creates a new TextEditor instance.
    /// </summary>
    public TextEditor() : this(new TextArea())
    {
    }
    
    /// <summary>
    /// Creates a new TextEditor instance.
    /// </summary>
    protected TextEditor(TextArea textArea)
    {
      if (textArea == null)
        throw new ArgumentNullException("textArea");
      this.textArea = textArea;
      
      textArea.TextView.Services.AddService(typeof(TextEditor), this);
      
      SetCurrentValue(OptionsProperty, textArea.Options);
      SetCurrentValue(DocumentProperty, new TextDocument());
    }
    
    #if !DOTNET4
    void SetCurrentValue(DependencyProperty property, object value)
    {
      SetValue(property, value);
    }
    #endif
    #endregion
    
    /// <inheritdoc/>
    protected override System.Windows.Automation.Peers.AutomationPeer OnCreateAutomationPeer()
    {
      return new TextEditorAutomationPeer(this);
    }
    
    /// Forward focus to TextArea.
    /// <inheritdoc/>
    protected override void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
    {
      base.OnGotKeyboardFocus(e);
      if (e.NewFocus == this) {
        Keyboard.Focus(this.TextArea);
        e.Handled = true;
      }
    }
    
    #region Document property
    /// <summary>
    /// Document property.
    /// </summary>
    public static readonly DependencyProperty DocumentProperty
      = TextView.DocumentProperty.AddOwner(
        typeof(TextEditor), new FrameworkPropertyMetadata(OnDocumentChanged));
    
    /// <summary>
    /// Gets/Sets the document displayed by the text editor.
    /// This is a dependency property.
    /// </summary>
    public TextDocument Document {
      get { return (TextDocument)GetValue(DocumentProperty); }
      set { SetValue(DocumentProperty, value); }
    }
    
    /// <summary>
    /// Occurs when the document property has changed.
    /// </summary>
    public event EventHandler DocumentChanged;
    
    /// <summary>
    /// Raises the <see cref="DocumentChanged"/> event.
    /// </summary>
    protected virtual void OnDocumentChanged(EventArgs e)
    {
      if (DocumentChanged != null) {
        DocumentChanged(this, e);
      }
    }
    
    static void OnDocumentChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
    {
      ((TextEditor)dp).OnDocumentChanged((TextDocument)e.OldValue, (TextDocument)e.NewValue);
    }
    
    void OnDocumentChanged(TextDocument oldValue, TextDocument newValue)
    {
      if (oldValue != null) {
        TextDocumentWeakEventManager.TextChanged.RemoveListener(oldValue, this);
        PropertyChangedEventManager.RemoveListener(oldValue.UndoStack, this, "IsOriginalFile");
      }
      textArea.Document = newValue;
      if (newValue != null) {
        TextDocumentWeakEventManager.TextChanged.AddListener(newValue, this);
        PropertyChangedEventManager.AddListener(newValue.UndoStack, this, "IsOriginalFile");
      }
      OnDocumentChanged(EventArgs.Empty);
      OnTextChanged(EventArgs.Empty);
    }
    #endregion
    
    #region Options property
    /// <summary>
    /// Options property.
    /// </summary>
    public static readonly DependencyProperty OptionsProperty
      = TextView.OptionsProperty.AddOwner(typeof(TextEditor), new FrameworkPropertyMetadata(OnOptionsChanged));
    
    /// <summary>
    /// Gets/Sets the options currently 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);
      }
    }
    
    static void OnOptionsChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
    {
      ((TextEditor)dp).OnOptionsChanged((TextEditorOptions)e.OldValue, (TextEditorOptions)e.NewValue);
    }
    
    void OnOptionsChanged(TextEditorOptions oldValue, TextEditorOptions newValue)
    {
      if (oldValue != null) {
        PropertyChangedWeakEventManager.RemoveListener(oldValue, this);
      }
      textArea.Options = newValue;
      if (newValue != null) {
        PropertyChangedWeakEventManager.AddListener(newValue, this);
      }
      OnOptionChanged(new PropertyChangedEventArgs(null));
    }
    
    /// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
    protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
    {
      if (managerType == typeof(PropertyChangedWeakEventManager)) {
        OnOptionChanged((PropertyChangedEventArgs)e);
        return true;
      } else if (managerType == typeof(TextDocumentWeakEventManager.TextChanged)) {
        OnTextChanged(e);
        return true;
      } else if (managerType == typeof(PropertyChangedEventManager)) {
        return HandleIsOriginalChanged((PropertyChangedEventArgs)e);
      }
      return false;
    }
    
    bool IWeakEventListener.ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
    {
      return ReceiveWeakEvent(managerType, sender, e);
    }
    #endregion
    
    #region Text property
    /// <summary>
    /// Gets/Sets the text of the current document.
    /// </summary>
    [Localizability(LocalizationCategory.Text), DefaultValue("")]
    public string Text {
      get {
        TextDocument document = this.Document;
        return document != null ? document.Text : string.Empty;
      }
      set {
        TextDocument document = GetDocument();
        document.Text = value ?? string.Empty;
        // after replacing the full text, the caret is positioned at the end of the document
        // - reset it to the beginning.
        this.CaretOffset = 0;
        document.UndoStack.ClearAll();
      }
    }
    
    TextDocument GetDocument()
    {
      TextDocument document = this.Document;
      if (document == null)
        throw ThrowUtil.NoDocumentAssigned();
      return document;
    }
    
    /// <summary>
    /// Occurs when the Text property changes.
    /// </summary>
    public event EventHandler TextChanged;
    
    /// <summary>
    /// Raises the <see cref="TextChanged"/> event.
    /// </summary>
    protected virtual void OnTextChanged(EventArgs e)
    {
      if (TextChanged != null) {
        TextChanged(this, e);
      }
    }
    #endregion
    
    #region TextArea / ScrollViewer properties
    readonly TextArea textArea;
    ScrollViewer scrollViewer;
    
    /// <summary>
    /// Is called after the template was applied.
    /// </summary>
    public override void OnApplyTemplate()
    {
      base.OnApplyTemplate();
      scrollViewer = (ScrollViewer)Template.FindName("PART_ScrollViewer", this);
    }
    
    /// <summary>
    /// Gets the text area.
    /// </summary>
    public TextArea TextArea {
      get {
        return textArea;
      }
    }
    
    /// <summary>
    /// Gets the scroll viewer used by the text editor.
    /// This property can return null if the template has not been applied / does not contain a scroll viewer.
    /// </summary>
    internal ScrollViewer ScrollViewer {
      get { return scrollViewer; }
    }
    
    bool CanExecute(RoutedUICommand command)
    {
      TextArea textArea = this.TextArea;
      if (textArea == null)
        return false;
      else
        return command.CanExecute(null, textArea);
    }
    
    void Execute(RoutedUICommand command)
    {
      TextArea textArea = this.TextArea;
      if (textArea != null)
        command.Execute(null, textArea);
    }
    #endregion
    
    #region Syntax highlighting
    /// <summary>
    /// The <see cref="SyntaxHighlighting"/> property.
    /// </summary>
    public static readonly DependencyProperty SyntaxHighlightingProperty =
      DependencyProperty.Register("SyntaxHighlighting", typeof(IHighlightingDefinition), typeof(TextEditor),
                                  new FrameworkPropertyMetadata(OnSyntaxHighlightingChanged));
    
    
    /// <summary>
    /// Gets/sets the syntax highlighting definition used to colorize the text.
    /// </summary>
    public IHighlightingDefinition SyntaxHighlighting {
      get { return (IHighlightingDefinition)GetValue(SyntaxHighlightingProperty); }
      set { SetValue(SyntaxHighlightingProperty, value); }
    }
    
    IVisualLineTransformer colorizer;
    
    static void OnSyntaxHighlightingChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
      ((TextEditor)d).OnSyntaxHighlightingChanged(e.NewValue as IHighlightingDefinition);
    }
    
    void OnSyntaxHighlightingChanged(IHighlightingDefinition newValue)
    {
      if (colorizer != null) {
        this.TextArea.TextView.LineTransformers.Remove(colorizer);
        colorizer = null;
      }
      if (newValue != null) {
        colorizer = CreateColorizer(newValue);
        if (colorizer != null)
          this.TextArea.TextView.LineTransformers.Insert(0, colorizer);
      }
    }
    
    /// <summary>
    /// Creates the highlighting colorizer for the specified highlighting definition.
    /// Allows derived classes to provide custom colorizer implementations for special highlighting definitions.
    /// </summary>
    /// <returns></returns>
    protected virtual IVisualLineTransformer CreateColorizer(IHighlightingDefinition highlightingDefinition)
    {
      if (highlightingDefinition == null)
        throw new ArgumentNullException("highlightingDefinition");
      return new HighlightingColorizer(highlightingDefinition);
    }
    #endregion
    
    #region WordWrap
    /// <summary>
    /// Word wrap dependency property.
    /// </summary>
    public static readonly DependencyProperty WordWrapProperty =
      DependencyProperty.Register("WordWrap", typeof(bool), typeof(TextEditor),
                                  new FrameworkPropertyMetadata(Boxes.False));
    
    /// <summary>
    /// Specifies whether the text editor uses word wrapping.
    /// </summary>
    /// <remarks>
    /// Setting WordWrap=true has the same effect as setting HorizontalScrollBarVisibility=Disabled and will override the
    /// HorizontalScrollBarVisibility setting.
    /// </remarks>
    public bool WordWrap {
      get { return (bool)GetValue(WordWrapProperty); }
      set { SetValue(WordWrapProperty, Boxes.Box(value)); }
    }
    #endregion
    
    #region IsReadOnly
    /// <summary>
    /// IsReadOnly dependency property.
    /// </summary>
    public static readonly DependencyProperty IsReadOnlyProperty =
      DependencyProperty.Register("IsReadOnly", typeof(bool), typeof(TextEditor),
                                  new FrameworkPropertyMetadata(Boxes.False, OnIsReadOnlyChanged));
    
    /// <summary>
    /// Specifies whether the user can change the text editor content.
    /// Setting this property will replace the
    /// <see cref="Editing.TextArea.ReadOnlySectionProvider">TextArea.ReadOnlySectionProvider</see>.
    /// </summary>
    public bool IsReadOnly {
      get { return (bool)GetValue(IsReadOnlyProperty); }
      set { SetValue(IsReadOnlyProperty, Boxes.Box(value)); }
    }
    
    static void OnIsReadOnlyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
      TextEditor editor = d as TextEditor;
      if (editor != null) {
        if ((bool)e.NewValue)
          editor.TextArea.ReadOnlySectionProvider = ReadOnlySectionDocument.Instance;
        else
          editor.TextArea.ReadOnlySectionProvider = NoReadOnlySections.Instance;
        
        TextEditorAutomationPeer peer = TextEditorAutomationPeer.FromElement(editor) as TextEditorAutomationPeer;
        if (peer != null) {
          peer.RaiseIsReadOnlyChanged((bool)e.OldValue, (bool)e.NewValue);
        }
      }
    }
    #endregion
    
    #region IsModified
    /// <summary>
    /// Dependency property for <see cref="IsModified"/>
    /// </summary>
    public static readonly DependencyProperty IsModifiedProperty =
      DependencyProperty.Register("IsModified", typeof(bool), typeof(TextEditor),
                                  new FrameworkPropertyMetadata(Boxes.False, OnIsModifiedChanged));
    
    /// <summary>
    /// Gets/Sets the 'modified' flag.
    /// </summary>
    public bool IsModified {
      get { return (bool)GetValue(IsModifiedProperty); }
      set { SetValue(IsModifiedProperty, Boxes.Box(value)); }
    }
    
    static void OnIsModifiedChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
      TextEditor editor = d as TextEditor;
      if (editor != null) {
        TextDocument document = editor.Document;
        if (document != null) {
          UndoStack undoStack = document.UndoStack;
          if ((bool)e.NewValue) {
            if (undoStack.IsOriginalFile)
              undoStack.DiscardOriginalFileMarker();
          } else {
            undoStack.MarkAsOriginalFile();
          }
        }
      }
    }
    
    bool HandleIsOriginalChanged(PropertyChangedEventArgs e)
    {
      if (e.PropertyName == "IsOriginalFile") {
        TextDocument document = this.Document;
        if (document != null) {
          SetCurrentValue(IsModifiedProperty, Boxes.Box(!document.UndoStack.IsOriginalFile));
        }
        return true;
      } else {
        return false;
      }
    }
    #endregion
    
    #region ShowLineNumbers
    /// <summary>
    /// ShowLineNumbers dependency property.
    /// </summary>
    public static readonly DependencyProperty ShowLineNumbersProperty =
      DependencyProperty.Register("ShowLineNumbers", typeof(bool), typeof(TextEditor),
                                  new FrameworkPropertyMetadata(Boxes.False, OnShowLineNumbersChanged));
    
    /// <summary>
    /// Specifies whether line numbers are shown on the left to the text view.
    /// </summary>
    public bool ShowLineNumbers {
      get { return (bool)GetValue(ShowLineNumbersProperty); }
      set { SetValue(ShowLineNumbersProperty, Boxes.Box(value)); }
    }
    
    static void OnShowLineNumbersChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
      TextEditor editor = (TextEditor)d;
      var leftMargins = editor.TextArea.LeftMargins;
      if ((bool)e.NewValue) {
        LineNumberMargin lineNumbers = new LineNumberMargin();
        Line line = (Line)DottedLineMargin.Create();
        leftMargins.Insert(0, lineNumbers);
        leftMargins.Insert(1, line);
        var lineNumbersForeground = new Binding("LineNumbersForeground") { Source = editor };
        line.SetBinding(Line.StrokeProperty, lineNumbersForeground);
        lineNumbers.SetBinding(Control.ForegroundProperty, lineNumbersForeground);
      } else {
        for (int i = 0; i < leftMargins.Count; i++) {
          if (leftMargins[i] is LineNumberMargin) {
            leftMargins.RemoveAt(i);
            if (i < leftMargins.Count && DottedLineMargin.IsDottedLineMargin(leftMargins[i])) {
              leftMargins.RemoveAt(i);
            }
            break;
          }
        }
      }
    }
    #endregion
    
    #region LineNumbersForeground
    /// <summary>
    /// LineNumbersForeground dependency property.
    /// </summary>
    public static readonly DependencyProperty LineNumbersForegroundProperty =
      DependencyProperty.Register("LineNumbersForeground", typeof(Brush), typeof(TextEditor),
                                  new FrameworkPropertyMetadata(Brushes.Gray, OnLineNumbersForegroundChanged));
    
    /// <summary>
    /// Gets/sets the Brush used for displaying the foreground color of line numbers.
    /// </summary>
    public Brush LineNumbersForeground {
      get { return (Brush)GetValue(LineNumbersForegroundProperty); }
      set { SetValue(LineNumbersForegroundProperty, value); }
    }
    
    static void OnLineNumbersForegroundChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
    {
      TextEditor editor = (TextEditor)d;
      var lineNumberMargin = editor.TextArea.LeftMargins.FirstOrDefault(margin => margin is LineNumberMargin) as LineNumberMargin;;
      
      if (lineNumberMargin != null) {
        lineNumberMargin.SetValue(Control.ForegroundProperty, e.NewValue);
      }
    }
    #endregion
    
    #region TextBoxBase-like methods
    /// <summary>
    /// Appends text to the end of the document.
    /// </summary>
    public void AppendText(string textData)
    {
      var document = GetDocument();
      document.Insert(document.TextLength, textData);
    }
    
    /// <summary>
    /// Begins a group of document changes.
    /// </summary>
    public void BeginChange()
    {
      GetDocument().BeginUpdate();
    }
    
    /// <summary>
    /// Copies the current selection to the clipboard.
    /// </summary>
    public void Copy()
    {
      Execute(ApplicationCommands.Copy);
    }
    
    /// <summary>
    /// Removes the current selection and copies it to the clipboard.
    /// </summary>
    public void Cut()
    {
      Execute(ApplicationCommands.Cut);
    }
    
    /// <summary>
    /// Begins a group of document changes and returns an object that ends the group of document
    /// changes when it is disposed.
    /// </summary>
    public IDisposable DeclareChangeBlock()
    {
      return GetDocument().RunUpdate();
    }
    
    /// <summary>
    /// Ends the current group of document changes.
    /// </summary>
    public void EndChange()
    {
      GetDocument().EndUpdate();
    }
    
    /// <summary>
    /// Scrolls one line down.
    /// </summary>
    public void LineDown()
    {
      if (scrollViewer != null)
        scrollViewer.LineDown();
    }
    
    /// <summary>
    /// Scrolls to the left.
    /// </summary>
    public void LineLeft()
    {
      if (scrollViewer != null)
        scrollViewer.LineLeft();
    }
    
    /// <summary>
    /// Scrolls to the right.
    /// </summary>
    public void LineRight()
    {
      if (scrollViewer != null)
        scrollViewer.LineRight();
    }
    
    /// <summary>
    /// Scrolls one line up.
    /// </summary>
    public void LineUp()
    {
      if (scrollViewer != null)
        scrollViewer.LineUp();
    }
    
    /// <summary>
    /// Scrolls one page down.
    /// </summary>
    public void PageDown()
    {
      if (scrollViewer != null)
        scrollViewer.PageDown();
    }
    
    /// <summary>
    /// Scrolls one page up.
    /// </summary>
    public void PageUp()
    {
      if (scrollViewer != null)
        scrollViewer.PageUp();
    }
    
    /// <summary>
    /// Scrolls one page left.
    /// </summary>
    public void PageLeft()
    {
      if (scrollViewer != null)
        scrollViewer.PageLeft();
    }
    
    /// <summary>
    /// Scrolls one page right.
    /// </summary>
    public void PageRight()
    {
      if (scrollViewer != null)
        scrollViewer.PageRight();
    }
    
    /// <summary>
    /// Pastes the clipboard content.
    /// </summary>
    public void Paste()
    {
      Execute(ApplicationCommands.Paste);
    }
    
    /// <summary>
    /// Redoes the most recent undone command.
    /// </summary>
    /// <returns>True is the redo operation was successful, false is the redo stack is empty.</returns>
    public bool Redo()
    {
      if (CanExecute(ApplicationCommands.Redo)) {
        Execute(ApplicationCommands.Redo);
        return true;
      }
      return false;
    }
    
    /// <summary>
    /// Scrolls to the end of the document.
    /// </summary>
    public void ScrollToEnd()
    {
      ApplyTemplate(); // ensure scrollViewer is created
      if (scrollViewer != null)
        scrollViewer.ScrollToEnd();
    }
    
    /// <summary>
    /// Scrolls to the start of the document.
    /// </summary>
    public void ScrollToHome()
    {
      ApplyTemplate(); // ensure scrollViewer is created
      if (scrollViewer != null)
        scrollViewer.ScrollToHome();
    }
    
    /// <summary>
    /// Scrolls to the specified position in the document.
    /// </summary>
    public void ScrollToHorizontalOffset(double offset)
    {
      ApplyTemplate(); // ensure scrollViewer is created
      if (scrollViewer != null)
        scrollViewer.ScrollToHorizontalOffset(offset);
    }
    
    /// <summary>
    /// Scrolls to the specified position in the document.
    /// </summary>
    public void ScrollToVerticalOffset(double offset)
    {
      ApplyTemplate(); // ensure scrollViewer is created
      if (scrollViewer != null)
        scrollViewer.ScrollToVerticalOffset(offset);
    }
    
    /// <summary>
    /// Selects the entire text.
    /// </summary>
    public void SelectAll()
    {
      Execute(ApplicationCommands.SelectAll);
    }
    
    /// <summary>
    /// Undoes the most recent command.
    /// </summary>
    /// <returns>True is the undo operation was successful, false is the undo stack is empty.</returns>
    public bool Undo()
    {
      if (CanExecute(ApplicationCommands.Undo)) {
        Execute(ApplicationCommands.Undo);
        return true;
      }
      return false;
    }
    
    /// <summary>
    /// Gets if the most recent undone command can be redone.
    /// </summary>
    public bool CanRedo {
      get { return CanExecute(ApplicationCommands.Redo); }
    }
    
    /// <summary>
    /// Gets if the most recent command can be undone.
    /// </summary>
    public bool CanUndo {
      get { return CanExecute(ApplicationCommands.Undo); }
    }
    
    /// <summary>
    /// Gets the vertical size of the document.
    /// </summary>
    public double ExtentHeight {
      get {
        return scrollViewer != null ? scrollViewer.ExtentHeight : 0;
      }
    }
    
    /// <summary>
    /// Gets the horizontal size of the current document region.
    /// </summary>
    public double ExtentWidth {
      get {
        return scrollViewer != null ? scrollViewer.ExtentWidth : 0;
      }
    }
    
    /// <summary>
    /// Gets the horizontal size of the viewport.
    /// </summary>
    public double ViewportHeight {
      get {
        return scrollViewer != null ? scrollViewer.ViewportHeight : 0;
      }
    }
    
    /// <summary>
    /// Gets the horizontal size of the viewport.
    /// </summary>
    public double ViewportWidth {
      get {
        return scrollViewer != null ? scrollViewer.ViewportWidth : 0;
      }
    }
    
    /// <summary>
    /// Gets the vertical scroll position.
    /// </summary>
    public double VerticalOffset {
      get {
        return scrollViewer != null ? scrollViewer.VerticalOffset : 0;
      }
    }
    
    /// <summary>
    /// Gets the horizontal scroll position.
    /// </summary>
    public double HorizontalOffset {
      get {
        return scrollViewer != null ? scrollViewer.HorizontalOffset : 0;
      }
    }
    #endregion
    
    #region TextBox methods
    /// <summary>
    /// Gets/Sets the selected text.
    /// </summary>
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public string SelectedText {
      get {
        TextArea textArea = this.TextArea;
        // We'll get the text from the whole surrounding segment.
        // This is done to ensure that SelectedText.Length == SelectionLength.
        if (textArea != null && textArea.Document != null && !textArea.Selection.IsEmpty)
          return textArea.Document.GetText(textArea.Selection.SurroundingSegment);
        else
          return string.Empty;
      }
      set {
        if (value == null)
          throw new ArgumentNullException("value");
        TextArea textArea = this.TextArea;
        if (textArea != null && textArea.Document != null) {
          int offset = this.SelectionStart;
          int length = this.SelectionLength;
          textArea.Document.Replace(offset, length, value);
          // keep inserted text selected
          textArea.Selection = SimpleSelection.Create(textArea, offset, offset + value.Length);
        }
      }
    }
    
    /// <summary>
    /// Gets/sets the caret position.
    /// </summary>
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public int CaretOffset {
      get {
        TextArea textArea = this.TextArea;
        if (textArea != null)
          return textArea.Caret.Offset;
        else
          return 0;
      }
      set {
        TextArea textArea = this.TextArea;
        if (textArea != null)
          textArea.Caret.Offset = value;
      }
    }
    
    /// <summary>
    /// Gets/sets the start position of the selection.
    /// </summary>
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public int SelectionStart {
      get {
        TextArea textArea = this.TextArea;
        if (textArea != null) {
          if (textArea.Selection.IsEmpty)
            return textArea.Caret.Offset;
          else
            return textArea.Selection.SurroundingSegment.Offset;
        } else {
          return 0;
        }
      }
      set {
        Select(value, SelectionLength);
      }
    }
    
    /// <summary>
    /// Gets/sets the length of the selection.
    /// </summary>
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public int SelectionLength {
      get {
        TextArea textArea = this.TextArea;
        if (textArea != null && !textArea.Selection.IsEmpty)
          return textArea.Selection.SurroundingSegment.Length;
        else
          return 0;
      }
      set {
        Select(SelectionStart, value);
      }
    }
    
    /// <summary>
    /// Selects the specified text section.
    /// </summary>
    public void Select(int start, int length)
    {
      int documentLength = Document != null ? Document.TextLength : 0;
      if (start < 0 || start > documentLength)
        throw new ArgumentOutOfRangeException("start", start, "Value must be between 0 and " + documentLength);
      if (length < 0 || start + length > documentLength)
        throw new ArgumentOutOfRangeException("length", length, "Value must be between 0 and " + (documentLength - start));
      textArea.Selection = SimpleSelection.Create(textArea, start, start + length);
      textArea.Caret.Offset = start + length;
    }
    
    /// <summary>
    /// Gets the number of lines in the document.
    /// </summary>
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public int LineCount {
      get {
        TextDocument document = this.Document;
        if (document != null)
          return document.LineCount;
        else
          return 1;
      }
    }
    
    /// <summary>
    /// Clears the text.
    /// </summary>
    public void Clear()
    {
      this.Text = string.Empty;
    }
    #endregion
    
    #region Loading from stream
    /// <summary>
    /// Loads the text from the stream, auto-detecting the encoding.
    /// </summary>
    /// <remarks>
    /// This method sets <see cref="IsModified"/> to false.
    /// </remarks>
    public void Load(Stream stream)
    {
      using (StreamReader reader = FileReader.OpenStream(stream, this.Encoding ?? Encoding.UTF8)) {
        this.Text = reader.ReadToEnd();
        SetCurrentValue(EncodingProperty, reader.CurrentEncoding); // assign encoding after ReadToEnd() so that the StreamReader can autodetect the encoding
      }
      SetCurrentValue(IsModifiedProperty, Boxes.False);
    }
    
    /// <summary>
    /// Loads the text from the stream, auto-detecting the encoding.
    /// </summary>
    public void Load(string fileName)
    {
      if (fileName == null)
        throw new ArgumentNullException("fileName");
      using (FileStream fs = new FileStream(fileName, FileMode.Open, FileAccess.Read, FileShare.Read)) {
        Load(fs);
      }
    }
    
    /// <summary>
    /// Encoding dependency property.
    /// </summary>
    public static readonly DependencyProperty EncodingProperty =
      DependencyProperty.Register("Encoding", typeof(Encoding), typeof(TextEditor));
    
    /// <summary>
    /// Gets/sets the encoding used when the file is saved.
    /// </summary>
    /// <remarks>
    /// The <see cref="Load(Stream)"/> method autodetects the encoding of the file and sets this property accordingly.
    /// The <see cref="Save(Stream)"/> method uses the encoding specified in this property.
    /// </remarks>
    [DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
    public Encoding Encoding {
      get { return (Encoding)GetValue(EncodingProperty); }
      set { SetValue(EncodingProperty, value); }
    }
    
    /// <summary>
    /// Saves the text to the stream.
    /// </summary>
    /// <remarks>
    /// This method sets <see cref="IsModified"/> to false.
    /// </remarks>
    public void Save(Stream stream)
    {
      if (stream == null)
        throw new ArgumentNullException("stream");
      var encoding = this.Encoding;
      var document = this.Document;
      StreamWriter writer = encoding != null ? new StreamWriter(stream, encoding) : new StreamWriter(stream);
      if (document != null)
        document.WriteTextTo(writer);
      writer.Flush();
      // do not close the stream
      SetCurrentValue(IsModifiedProperty, Boxes.False);
    }
    
    /// <summary>
    /// Saves the text to the file.
    /// </summary>
    public void Save(string fileName)
    {
      if (fileName == null)
        throw new ArgumentNullException("fileName");
      using (FileStream fs = new FileStream(fileName, FileMode.Create, FileAccess.Write, FileShare.None)) {
        Save(fs);
      }
    }
    #endregion
    
    #region MouseHover events
    /// <summary>
    /// The PreviewMouseHover event.
    /// </summary>
    public static readonly RoutedEvent PreviewMouseHoverEvent =
      TextView.PreviewMouseHoverEvent.AddOwner(typeof(TextEditor));
    
    /// <summary>
    /// The MouseHover event.
    /// </summary>
    public static readonly RoutedEvent MouseHoverEvent =
      TextView.MouseHoverEvent.AddOwner(typeof(TextEditor));
    
    
    /// <summary>
    /// The PreviewMouseHoverStopped event.
    /// </summary>
    public static readonly RoutedEvent PreviewMouseHoverStoppedEvent =
      TextView.PreviewMouseHoverStoppedEvent.AddOwner(typeof(TextEditor));
    
    /// <summary>
    /// The MouseHoverStopped event.
    /// </summary>
    public static readonly RoutedEvent MouseHoverStoppedEvent =
      TextView.MouseHoverStoppedEvent.AddOwner(typeof(TextEditor));
    
    
    /// <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); }
    }
    #endregion
    
    #region ScrollBarVisibility
    /// <summary>
    /// Dependency property for <see cref="HorizontalScrollBarVisibility"/>
    /// </summary>
    public static readonly DependencyProperty HorizontalScrollBarVisibilityProperty = ScrollViewer.HorizontalScrollBarVisibilityProperty.AddOwner(typeof(TextEditor), new FrameworkPropertyMetadata(ScrollBarVisibility.Visible));
    
    /// <summary>
    /// Gets/Sets the horizontal scroll bar visibility.
    /// </summary>
    public ScrollBarVisibility HorizontalScrollBarVisibility {
      get { return (ScrollBarVisibility)GetValue(HorizontalScrollBarVisibilityProperty); }
      set { SetValue(HorizontalScrollBarVisibilityProperty, value); }
    }
    
    /// <summary>
    /// Dependency property for <see cref="VerticalScrollBarVisibility"/>
    /// </summary>
    public static readonly DependencyProperty VerticalScrollBarVisibilityProperty = ScrollViewer.VerticalScrollBarVisibilityProperty.AddOwner(typeof(TextEditor), new FrameworkPropertyMetadata(ScrollBarVisibility.Visible));
    
    /// <summary>
    /// Gets/Sets the vertical scroll bar visibility.
    /// </summary>
    public ScrollBarVisibility VerticalScrollBarVisibility {
      get { return (ScrollBarVisibility)GetValue(VerticalScrollBarVisibilityProperty); }
      set { SetValue(VerticalScrollBarVisibilityProperty, value); }
    }
    #endregion
    
    object IServiceProvider.GetService(Type serviceType)
    {
      return textArea.GetService(serviceType);
    }
    
    /// <summary>
    /// Gets the text view position from a point inside the editor.
    /// </summary>
    /// <param name="point">The position, relative to top left
    /// corner of TextEditor control</param>
    /// <returns>The text view position, or null if the point is outside the document.</returns>
    public TextViewPosition? GetPositionFromPoint(Point point)
    {
      if (this.Document == null)
        return null;
      TextView textView = this.TextArea.TextView;
      return textView.GetPosition(TranslatePoint(point, textView) + textView.ScrollOffset);
    }
    
    /// <summary>
    /// Scrolls to the specified line.
    /// This method requires that the TextEditor was already assigned a size (WPF layout must have run prior).
    /// </summary>
    public void ScrollToLine(int line)
    {
      ScrollTo(line, -1);
    }
    
    /// <summary>
    /// Scrolls to the specified line/column.
    /// This method requires that the TextEditor was already assigned a size (WPF layout must have run prior).
    /// </summary>
    public void ScrollTo(int line, int column)
    {
      const double MinimumScrollPercentage = 0.3;
      
      TextView textView = textArea.TextView;
      TextDocument document = textView.Document;
      if (scrollViewer != null && document != null) {
        if (line < 1)
          line = 1;
        if (line > document.LineCount)
          line = document.LineCount;
        
        IScrollInfo scrollInfo = textView;
        if (!scrollInfo.CanHorizontallyScroll) {
          // Word wrap is enabled. Ensure that we have up-to-date info about line height so that we scroll
          // to the correct position.
          // This avoids that the user has to repeat the ScrollTo() call several times when there are very long lines.
          VisualLine vl = textView.GetOrConstructVisualLine(document.GetLineByNumber(line));
          double remainingHeight = scrollViewer.ViewportHeight / 2;
          while (remainingHeight > 0) {
            DocumentLine prevLine = vl.FirstDocumentLine.PreviousLine;
            if (prevLine == null)
              break;
            vl = textView.GetOrConstructVisualLine(prevLine);
            remainingHeight -= vl.Height;
          }
        }
        
        Point p = textArea.TextView.GetVisualPosition(new TextViewPosition(line, Math.Max(1, column)), VisualYPosition.LineMiddle);
        double verticalPos = p.Y - scrollViewer.ViewportHeight / 2;
        if (Math.Abs(verticalPos - scrollViewer.VerticalOffset) > MinimumScrollPercentage * scrollViewer.ViewportHeight) {
          scrollViewer.ScrollToVerticalOffset(Math.Max(0, verticalPos));
        }
        if (column > 0) {
          if (p.X > scrollViewer.ViewportWidth - Caret.MinimumDistanceToViewBorder * 2) {
            double horizontalPos = Math.Max(0, p.X - scrollViewer.ViewportWidth / 2);
            if (Math.Abs(horizontalPos - scrollViewer.HorizontalOffset) > MinimumScrollPercentage * scrollViewer.ViewportWidth) {
              scrollViewer.ScrollToHorizontalOffset(horizontalPos);
            }
          } else {
            scrollViewer.ScrollToHorizontalOffset(0);
          }
        }
      }
    }
  }
}