source: branches/2925_AutoDiffForDynamicalModels/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Editing/TextArea.cs @ 18242

// 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.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Diagnostics;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Controls.Primitives;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Threading;
using ICSharpCode.AvalonEdit.Document;
using ICSharpCode.AvalonEdit.Indentation;
using ICSharpCode.AvalonEdit.Rendering;
using ICSharpCode.AvalonEdit.Utils;
using ICSharpCode.NRefactory;
using ICSharpCode.NRefactory.Editor;

namespace ICSharpCode.AvalonEdit.Editing
{
  /// <summary>
  /// Control that wraps a TextView and adds support for user input and the caret.
  /// </summary>
  public class TextArea : Control, IScrollInfo, IWeakEventListener, ITextEditorComponent, IServiceProvider
  {
    internal readonly ImeSupport ime;
    
    #region Constructor
    static TextArea()
    {
      DefaultStyleKeyProperty.OverrideMetadata(typeof(TextArea),
                                               new FrameworkPropertyMetadata(typeof(TextArea)));
      KeyboardNavigation.IsTabStopProperty.OverrideMetadata(
        typeof(TextArea), new FrameworkPropertyMetadata(Boxes.True));
      KeyboardNavigation.TabNavigationProperty.OverrideMetadata(
        typeof(TextArea), new FrameworkPropertyMetadata(KeyboardNavigationMode.None));
      FocusableProperty.OverrideMetadata(
        typeof(TextArea), new FrameworkPropertyMetadata(Boxes.True));
    }
    
    /// <summary>
    /// Creates a new TextArea instance.
    /// </summary>
    public TextArea() : this(new TextView())
    {
    }
    
    /// <summary>
    /// Creates a new TextArea instance.
    /// </summary>
    protected TextArea(TextView textView)
    {
      if (textView == null)
        throw new ArgumentNullException("textView");
      this.textView = textView;
      this.Options = textView.Options;
      
      selection = emptySelection = new EmptySelection(this);
      
      textView.Services.AddService(typeof(TextArea), this);
      
      textView.LineTransformers.Add(new SelectionColorizer(this));
      textView.InsertLayer(new SelectionLayer(this), KnownLayer.Selection, LayerInsertionPosition.Replace);
      
      caret = new Caret(this);
      caret.PositionChanged += (sender, e) => RequestSelectionValidation();
      caret.PositionChanged += CaretPositionChanged;
      AttachTypingEvents();
      ime = new ImeSupport(this);
      
      leftMargins.CollectionChanged += leftMargins_CollectionChanged;
      
      this.DefaultInputHandler = new TextAreaDefaultInputHandler(this);
      this.ActiveInputHandler = this.DefaultInputHandler;
    }
    #endregion
    
    #region InputHandler management
    /// <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) {
          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);
        }
      }
    }
    
    /// <summary>
    /// Occurs when the ActiveInputHandler property changes.
    /// </summary>
    public event EventHandler ActiveInputHandlerChanged;
    
    ImmutableStack<TextAreaStackedInputHandler> stackedInputHandlers = ImmutableStack<TextAreaStackedInputHandler>.Empty;
    
    /// <summary>
    /// Gets the list of currently active stacked input handlers.
    /// </summary>
    /// <remarks><inheritdoc cref="ITextAreaInputHandler"/></remarks>
    public ImmutableStack<TextAreaStackedInputHandler> 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(TextAreaStackedInputHandler 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(TextAreaStackedInputHandler 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
    /// <summary>
    /// Document property.
    /// </summary>
    public static readonly DependencyProperty DocumentProperty
      = TextView.DocumentProperty.AddOwner(typeof(TextArea), new FrameworkPropertyMetadata(OnDocumentChanged));
    
    /// <summary>
    /// Gets/Sets the document displayed by the text editor.
    /// </summary>
    public TextDocument Document {
      get { return (TextDocument)GetValue(DocumentProperty); }
      set { SetValue(DocumentProperty, value); }
    }
    
    /// <inheritdoc/>
    public event EventHandler DocumentChanged;
    
    static void OnDocumentChanged(DependencyObject dp, DependencyPropertyChangedEventArgs e)
    {
      ((TextArea)dp).OnDocumentChanged((TextDocument)e.OldValue, (TextDocument)e.NewValue);
    }
    
    void OnDocumentChanged(TextDocument oldValue, TextDocument newValue)
    {
      if (oldValue != null) {
        TextDocumentWeakEventManager.Changing.RemoveListener(oldValue, this);
        TextDocumentWeakEventManager.Changed.RemoveListener(oldValue, this);
        TextDocumentWeakEventManager.UpdateStarted.RemoveListener(oldValue, this);
        TextDocumentWeakEventManager.UpdateFinished.RemoveListener(oldValue, this);
      }
      textView.Document = newValue;
      if (newValue != null) {
        TextDocumentWeakEventManager.Changing.AddListener(newValue, this);
        TextDocumentWeakEventManager.Changed.AddListener(newValue, this);
        TextDocumentWeakEventManager.UpdateStarted.AddListener(newValue, this);
        TextDocumentWeakEventManager.UpdateFinished.AddListener(newValue, this);
      }
      // Reset caret location and selection: this is necessary because the caret/selection might be invalid
      // in the new document (e.g. if new document is shorter than the old document).
      caret.Location = new TextLocation(1, 1);
      this.ClearSelection();
      if (DocumentChanged != null)
        DocumentChanged(this, EventArgs.Empty);
      CommandManager.InvalidateRequerySuggested();
    }
    #endregion
    
    #region Options property
    /// <summary>
    /// Options property.
    /// </summary>
    public static readonly DependencyProperty OptionsProperty
      = TextView.OptionsProperty.AddOwner(typeof(TextArea), new FrameworkPropertyMetadata(OnOptionsChanged));
    
    /// <summary>
    /// Gets/Sets the document displayed 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)
    {
      ((TextArea)dp).OnOptionsChanged((TextEditorOptions)e.OldValue, (TextEditorOptions)e.NewValue);
    }
    
    void OnOptionsChanged(TextEditorOptions oldValue, TextEditorOptions newValue)
    {
      if (oldValue != null) {
        PropertyChangedWeakEventManager.RemoveListener(oldValue, this);
      }
      textView.Options = newValue;
      if (newValue != null) {
        PropertyChangedWeakEventManager.AddListener(newValue, this);
      }
      OnOptionChanged(new PropertyChangedEventArgs(null));
    }
    #endregion
    
    #region ReceiveWeakEvent
    /// <inheritdoc cref="IWeakEventListener.ReceiveWeakEvent"/>
    protected virtual bool ReceiveWeakEvent(Type managerType, object sender, EventArgs e)
    {
      if (managerType == typeof(TextDocumentWeakEventManager.Changing)) {
        OnDocumentChanging();
        return true;
      } else if (managerType == typeof(TextDocumentWeakEventManager.Changed)) {
        OnDocumentChanged((DocumentChangeEventArgs)e);
        return true;
      } else if (managerType == typeof(TextDocumentWeakEventManager.UpdateStarted)) {
        OnUpdateStarted();
        return true;
      } else if (managerType == typeof(TextDocumentWeakEventManager.UpdateFinished)) {
        OnUpdateFinished();
        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 Caret handling on document changes
    void OnDocumentChanging()
    {
      caret.OnDocumentChanging();
    }
    
    void OnDocumentChanged(DocumentChangeEventArgs e)
    {
      caret.OnDocumentChanged(e);
      this.Selection = selection.UpdateOnDocumentChange(e);
    }
    
    void OnUpdateStarted()
    {
      Document.UndoStack.PushOptional(new RestoreCaretAndSelectionUndoAction(this));
    }
    
    void OnUpdateFinished()
    {
      caret.OnDocumentUpdateFinished();
    }
    
    sealed class RestoreCaretAndSelectionUndoAction : IUndoableOperation
    {
      // keep textarea in weak reference because the IUndoableOperation is stored with the document
      WeakReference textAreaReference;
      TextViewPosition caretPosition;
      Selection selection;
      
      public RestoreCaretAndSelectionUndoAction(TextArea textArea)
      {
        this.textAreaReference = new WeakReference(textArea);
        // Just save the old caret position, no need to validate here.
        // If we restore it, we'll validate it anyways.
        this.caretPosition = textArea.Caret.NonValidatedPosition;
        this.selection = textArea.Selection;
      }
      
      public void Undo()
      {
        TextArea textArea = (TextArea)textAreaReference.Target;
        if (textArea != null) {
          textArea.Caret.Position = caretPosition;
          textArea.Selection = selection;
        }
      }
      
      public void Redo()
      {
        // redo=undo: we just restore the caret/selection state
        Undo();
      }
    }
    #endregion
    
    #region TextView property
    readonly TextView textView;
    IScrollInfo scrollInfo;

    /// <summary>
    /// Gets the text view used to display text in this text area.
    /// </summary>
    public TextView TextView {
      get {
        return textView;
      }
    }
    /// <inheritdoc/>
    public override void OnApplyTemplate()
    {
      base.OnApplyTemplate();
      scrollInfo = textView;
      ApplyScrollInfo();
    }
    #endregion
    
    #region Selection property
    internal readonly Selection emptySelection;
    Selection selection;
    
    /// <summary>
    /// Occurs when the selection has changed.
    /// </summary>
    public event EventHandler SelectionChanged;
    
    /// <summary>
    /// Gets/Sets the selection in this text area.
    /// </summary>
    
    public Selection Selection {
      get { return selection; }
      set {
        if (value == null)
          throw new ArgumentNullException("value");
        if (value.textArea != this)
          throw new ArgumentException("Cannot use a Selection instance that belongs to another text area.");
        if (!object.Equals(selection, value)) {
//          Debug.WriteLine("Selection change from " + selection + " to " + value);
          if (textView != null) {
            ISegment oldSegment = selection.SurroundingSegment;
            ISegment newSegment = value.SurroundingSegment;
            if (!Selection.EnableVirtualSpace && (selection is SimpleSelection && value is SimpleSelection && oldSegment != null && newSegment != null)) {
              // perf optimization:
              // When a simple selection changes, don't redraw the whole selection, but only the changed parts.
              int oldSegmentOffset = oldSegment.Offset;
              int newSegmentOffset = newSegment.Offset;
              if (oldSegmentOffset != newSegmentOffset) {
                textView.Redraw(Math.Min(oldSegmentOffset, newSegmentOffset),
                                Math.Abs(oldSegmentOffset - newSegmentOffset),
                                DispatcherPriority.Background);
              }
              int oldSegmentEndOffset = oldSegment.EndOffset;
              int newSegmentEndOffset = newSegment.EndOffset;
              if (oldSegmentEndOffset != newSegmentEndOffset) {
                textView.Redraw(Math.Min(oldSegmentEndOffset, newSegmentEndOffset),
                                Math.Abs(oldSegmentEndOffset - newSegmentEndOffset),
                                DispatcherPriority.Background);
              }
            } else {
              textView.Redraw(oldSegment, DispatcherPriority.Background);
              textView.Redraw(newSegment, DispatcherPriority.Background);
            }
          }
          selection = value;
          if (SelectionChanged != null)
            SelectionChanged(this, EventArgs.Empty);
          // a selection change causes commands like copy/paste/etc. to change status
          CommandManager.InvalidateRequerySuggested();
        }
      }
    }
    
    /// <summary>
    /// Clears the current selection.
    /// </summary>
    public void ClearSelection()
    {
      this.Selection = emptySelection;
    }
    
    /// <summary>
    /// The <see cref="SelectionBrush"/> property.
    /// </summary>
    public static readonly DependencyProperty SelectionBrushProperty =
      DependencyProperty.Register("SelectionBrush", typeof(Brush), typeof(TextArea));
    
    /// <summary>
    /// Gets/Sets the background brush used for the selection.
    /// </summary>
    public Brush SelectionBrush {
      get { return (Brush)GetValue(SelectionBrushProperty); }
      set { SetValue(SelectionBrushProperty, value); }
    }
    
    /// <summary>
    /// The <see cref="SelectionForeground"/> property.
    /// </summary>
    public static readonly DependencyProperty SelectionForegroundProperty =
      DependencyProperty.Register("SelectionForeground", typeof(Brush), typeof(TextArea));
    
    /// <summary>
    /// Gets/Sets the foreground brush used selected text.
    /// </summary>
    public Brush SelectionForeground {
      get { return (Brush)GetValue(SelectionForegroundProperty); }
      set { SetValue(SelectionForegroundProperty, value); }
    }
    
    /// <summary>
    /// The <see cref="SelectionBorder"/> property.
    /// </summary>
    public static readonly DependencyProperty SelectionBorderProperty =
      DependencyProperty.Register("SelectionBorder", typeof(Pen), typeof(TextArea));
    
    /// <summary>
    /// Gets/Sets the background brush used for the selection.
    /// </summary>
    public Pen SelectionBorder {
      get { return (Pen)GetValue(SelectionBorderProperty); }
      set { SetValue(SelectionBorderProperty, value); }
    }
    
    /// <summary>
    /// The <see cref="SelectionCornerRadius"/> property.
    /// </summary>
    public static readonly DependencyProperty SelectionCornerRadiusProperty =
      DependencyProperty.Register("SelectionCornerRadius", typeof(double), typeof(TextArea),
                                  new FrameworkPropertyMetadata(3.0));
    
    /// <summary>
    /// Gets/Sets the corner radius of the selection.
    /// </summary>
    public double SelectionCornerRadius {
      get { return (double)GetValue(SelectionCornerRadiusProperty); }
      set { SetValue(SelectionCornerRadiusProperty, value); }
    }
    #endregion
    
    #region Force caret to stay inside selection
    bool ensureSelectionValidRequested;
    int allowCaretOutsideSelection;
    
    void RequestSelectionValidation()
    {
      if (!ensureSelectionValidRequested && allowCaretOutsideSelection == 0) {
        ensureSelectionValidRequested = true;
        Dispatcher.BeginInvoke(DispatcherPriority.Normal, new Action(EnsureSelectionValid));
      }
    }
    
    /// <summary>
    /// Code that updates only the caret but not the selection can cause confusion when
    /// keys like 'Delete' delete the (possibly invisible) selected text and not the
    /// text around the caret.
    /// 
    /// So we'll ensure that the caret is inside the selection.
    /// (when the caret is not in the selection, we'll clear the selection)
    /// 
    /// This method is invoked using the Dispatcher so that code may temporarily violate this rule
    /// (e.g. most 'extend selection' methods work by first setting the caret, then the selection),
    /// it's sufficient to fix it after any event handlers have run.
    /// </summary>
    void EnsureSelectionValid()
    {
      ensureSelectionValidRequested = false;
      if (allowCaretOutsideSelection == 0) {
        if (!selection.IsEmpty && !selection.Contains(caret.Offset)) {
          Debug.WriteLine("Resetting selection because caret is outside");
          this.ClearSelection();
        }
      }
    }
    
    /// <summary>
    /// Temporarily allows positioning the caret outside the selection.
    /// Dispose the returned IDisposable to revert the allowance.
    /// </summary>
    /// <remarks>
    /// The text area only forces the caret to be inside the selection when other events
    /// have finished running (using the dispatcher), so you don't have to use this method
    /// for temporarily positioning the caret in event handlers.
    /// This method is only necessary if you want to run the WPF dispatcher, e.g. if you
    /// perform a drag'n'drop operation.
    /// </remarks>
    public IDisposable AllowCaretOutsideSelection()
    {
      VerifyAccess();
      allowCaretOutsideSelection++;
      return new CallbackOnDispose(
        delegate {
          VerifyAccess();
          allowCaretOutsideSelection--;
          RequestSelectionValidation();
        });
    }
    #endregion
    
    #region Properties
    readonly Caret caret;
    
    /// <summary>
    /// Gets the Caret used for this text area.
    /// </summary>
    public Caret Caret {
      get { return caret; }
    }
    
    void CaretPositionChanged(object sender, EventArgs e)
    {
      if (textView == null)
        return;
      
      this.textView.HighlightedLine = this.Caret.Line;
    }
    
    ObservableCollection<UIElement> leftMargins = new ObservableCollection<UIElement>();
    
    /// <summary>
    /// Gets the collection of margins displayed to the left of the text view.
    /// </summary>
    public ObservableCollection<UIElement> LeftMargins {
      get {
        return leftMargins;
      }
    }
    
    void leftMargins_CollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
    {
      if (e.OldItems != null) {
        foreach (ITextViewConnect c in e.OldItems.OfType<ITextViewConnect>()) {
          c.RemoveFromTextView(textView);
        }
      }
      if (e.NewItems != null) {
        foreach (ITextViewConnect c in e.NewItems.OfType<ITextViewConnect>()) {
          c.AddToTextView(textView);
        }
      }
    }
    
    IReadOnlySectionProvider readOnlySectionProvider = NoReadOnlySections.Instance;
    
    /// <summary>
    /// Gets/Sets an object that provides read-only sections for the text area.
    /// </summary>
    public IReadOnlySectionProvider ReadOnlySectionProvider {
      get { return readOnlySectionProvider; }
      set {
        if (value == null)
          throw new ArgumentNullException("value");
        readOnlySectionProvider = value;
        CommandManager.InvalidateRequerySuggested(); // the read-only status effects Paste.CanExecute and the IME
      }
    }
    #endregion
    
    #region IScrollInfo implementation
    ScrollViewer scrollOwner;
    bool canVerticallyScroll, canHorizontallyScroll;
    
    void ApplyScrollInfo()
    {
      if (scrollInfo != null) {
        scrollInfo.ScrollOwner = scrollOwner;
        scrollInfo.CanVerticallyScroll = canVerticallyScroll;
        scrollInfo.CanHorizontallyScroll = canHorizontallyScroll;
        scrollOwner = null;
      }
    }
    
    bool IScrollInfo.CanVerticallyScroll {
      get { return scrollInfo != null ? scrollInfo.CanVerticallyScroll : false; }
      set {
        canVerticallyScroll = value;
        if (scrollInfo != null)
          scrollInfo.CanVerticallyScroll = value;
      }
    }
    
    bool IScrollInfo.CanHorizontallyScroll {
      get { return scrollInfo != null ? scrollInfo.CanHorizontallyScroll : false; }
      set {
        canHorizontallyScroll = value;
        if (scrollInfo != null)
          scrollInfo.CanHorizontallyScroll = value;
      }
    }
    
    double IScrollInfo.ExtentWidth {
      get { return scrollInfo != null ? scrollInfo.ExtentWidth : 0; }
    }
    
    double IScrollInfo.ExtentHeight {
      get { return scrollInfo != null ? scrollInfo.ExtentHeight : 0; }
    }
    
    double IScrollInfo.ViewportWidth {
      get { return scrollInfo != null ? scrollInfo.ViewportWidth : 0; }
    }
    
    double IScrollInfo.ViewportHeight {
      get { return scrollInfo != null ? scrollInfo.ViewportHeight : 0; }
    }
    
    double IScrollInfo.HorizontalOffset {
      get { return scrollInfo != null ? scrollInfo.HorizontalOffset : 0; }
    }
    
    double IScrollInfo.VerticalOffset {
      get { return scrollInfo != null ? scrollInfo.VerticalOffset : 0; }
    }
    
    ScrollViewer IScrollInfo.ScrollOwner {
      get { return scrollInfo != null ? scrollInfo.ScrollOwner : null; }
      set {
        if (scrollInfo != null)
          scrollInfo.ScrollOwner = value;
        else
          scrollOwner = value;
      }
    }
    
    void IScrollInfo.LineUp()
    {
      if (scrollInfo != null) scrollInfo.LineUp();
    }
    
    void IScrollInfo.LineDown()
    {
      if (scrollInfo != null) scrollInfo.LineDown();
    }
    
    void IScrollInfo.LineLeft()
    {
      if (scrollInfo != null) scrollInfo.LineLeft();
    }
    
    void IScrollInfo.LineRight()
    {
      if (scrollInfo != null) scrollInfo.LineRight();
    }
    
    void IScrollInfo.PageUp()
    {
      if (scrollInfo != null) scrollInfo.PageUp();
    }
    
    void IScrollInfo.PageDown()
    {
      if (scrollInfo != null) scrollInfo.PageDown();
    }
    
    void IScrollInfo.PageLeft()
    {
      if (scrollInfo != null) scrollInfo.PageLeft();
    }
    
    void IScrollInfo.PageRight()
    {
      if (scrollInfo != null) scrollInfo.PageRight();
    }
    
    void IScrollInfo.MouseWheelUp()
    {
      if (scrollInfo != null) scrollInfo.MouseWheelUp();
    }
    
    void IScrollInfo.MouseWheelDown()
    {
      if (scrollInfo != null) scrollInfo.MouseWheelDown();
    }
    
    void IScrollInfo.MouseWheelLeft()
    {
      if (scrollInfo != null) scrollInfo.MouseWheelLeft();
    }
    
    void IScrollInfo.MouseWheelRight()
    {
      if (scrollInfo != null) scrollInfo.MouseWheelRight();
    }
    
    void IScrollInfo.SetHorizontalOffset(double offset)
    {
      if (scrollInfo != null) scrollInfo.SetHorizontalOffset(offset);
    }
    
    void IScrollInfo.SetVerticalOffset(double offset)
    {
      if (scrollInfo != null) scrollInfo.SetVerticalOffset(offset);
    }
    
    Rect IScrollInfo.MakeVisible(System.Windows.Media.Visual visual, Rect rectangle)
    {
      if (scrollInfo != null)
        return scrollInfo.MakeVisible(visual, rectangle);
      else
        return Rect.Empty;
    }
    #endregion
    
    #region Focus Handling (Show/Hide Caret)
    /// <inheritdoc/>
    protected override void OnMouseDown(MouseButtonEventArgs e)
    {
      base.OnMouseDown(e);
      Focus();
    }
    
    /// <inheritdoc/>
    protected override void OnGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
    {
      base.OnGotKeyboardFocus(e);
      // First activate IME, then show caret
      ime.OnGotKeyboardFocus(e);
      caret.Show();
    }
    
    /// <inheritdoc/>
    protected override void OnLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
    {
      base.OnLostKeyboardFocus(e);
      caret.Hide();
      ime.OnLostKeyboardFocus(e);
    }
    #endregion
    
    #region OnTextInput / RemoveSelectedText / ReplaceSelectionWithText
    /// <summary>
    /// Occurs when the TextArea receives text input.
    /// This is like the <see cref="UIElement.TextInput"/> event,
    /// but occurs immediately before the TextArea handles the TextInput event.
    /// </summary>
    public event TextCompositionEventHandler TextEntering;
    
    /// <summary>
    /// Occurs when the TextArea receives text input.
    /// This is like the <see cref="UIElement.TextInput"/> event,
    /// but occurs immediately after the TextArea handles the TextInput event.
    /// </summary>
    public event TextCompositionEventHandler TextEntered;
    
    /// <summary>
    /// Raises the TextEntering event.
    /// </summary>
    protected virtual void OnTextEntering(TextCompositionEventArgs e)
    {
      if (TextEntering != null) {
        TextEntering(this, e);
      }
    }
    
    /// <summary>
    /// Raises the TextEntered event.
    /// </summary>
    protected virtual void OnTextEntered(TextCompositionEventArgs e)
    {
      if (TextEntered != null) {
        TextEntered(this, e);
      }
    }
    
    /// <inheritdoc/>
    protected override void OnTextInput(TextCompositionEventArgs e)
    {
      //Debug.WriteLine("TextInput: Text='" + e.Text + "' SystemText='" + e.SystemText + "' ControlText='" + e.ControlText + "'");
      base.OnTextInput(e);
      if (!e.Handled && this.Document != null) {
        if (string.IsNullOrEmpty(e.Text) || e.Text == "\x1b" || e.Text == "\b") {
          // ASCII 0x1b = ESC.
          // WPF produces a TextInput event with that old ASCII control char
          // when Escape is pressed. We'll just ignore it.
          
          // A deadkey followed by backspace causes a textinput event for the BS character.
          
          // Similarly, some shortcuts like Alt+Space produce an empty TextInput event.
          // We have to ignore those (not handle them) to keep the shortcut working.
          return;
        }
        HideMouseCursor();
        PerformTextInput(e);
        e.Handled = true;
      }
    }
    
    /// <summary>
    /// Performs text input.
    /// This raises the <see cref="TextEntering"/> event, replaces the selection with the text,
    /// and then raises the <see cref="TextEntered"/> event.
    /// </summary>
    public void PerformTextInput(string text)
    {
      TextComposition textComposition = new TextComposition(InputManager.Current, this, text);
      TextCompositionEventArgs e = new TextCompositionEventArgs(Keyboard.PrimaryDevice, textComposition);
      e.RoutedEvent = TextInputEvent;
      PerformTextInput(e);
    }
    
    /// <summary>
    /// Performs text input.
    /// This raises the <see cref="TextEntering"/> event, replaces the selection with the text,
    /// and then raises the <see cref="TextEntered"/> event.
    /// </summary>
    public void PerformTextInput(TextCompositionEventArgs e)
    {
      if (e == null)
        throw new ArgumentNullException("e");
      if (this.Document == null)
        throw ThrowUtil.NoDocumentAssigned();
      OnTextEntering(e);
      if (!e.Handled) {
        if (e.Text == "\n" || e.Text == "\r" || e.Text == "\r\n")
          ReplaceSelectionWithNewLine();
        else {
          if (OverstrikeMode && Selection.IsEmpty && Document.GetLineByNumber(Caret.Line).EndOffset > Caret.Offset)
            EditingCommands.SelectRightByCharacter.Execute(null, this);
          ReplaceSelectionWithText(e.Text);
        }
        OnTextEntered(e);
        caret.BringCaretToView();
      }
    }
    
    void ReplaceSelectionWithNewLine()
    {
      string newLine = TextUtilities.GetNewLineFromDocument(this.Document, this.Caret.Line);
      using (this.Document.RunUpdate()) {
        ReplaceSelectionWithText(newLine);
        if (this.IndentationStrategy != null) {
          DocumentLine line = this.Document.GetLineByNumber(this.Caret.Line);
          ISegment[] deletable = GetDeletableSegments(line);
          if (deletable.Length == 1 && deletable[0].Offset == line.Offset && deletable[0].Length == line.Length) {
            // use indentation strategy only if the line is not read-only
            this.IndentationStrategy.IndentLine(this.Document, line);
          }
        }
      }
    }
    
    internal void RemoveSelectedText()
    {
      if (this.Document == null)
        throw ThrowUtil.NoDocumentAssigned();
      selection.ReplaceSelectionWithText(string.Empty);
      #if DEBUG
      if (!selection.IsEmpty) {
        foreach (ISegment s in selection.Segments) {
          Debug.Assert(this.ReadOnlySectionProvider.GetDeletableSegments(s).Count() == 0);
        }
      }
      #endif
    }
    
    internal void ReplaceSelectionWithText(string newText)
    {
      if (newText == null)
        throw new ArgumentNullException("newText");
      if (this.Document == null)
        throw ThrowUtil.NoDocumentAssigned();
      selection.ReplaceSelectionWithText(newText);
    }
    
    internal ISegment[] GetDeletableSegments(ISegment segment)
    {
      var deletableSegments = this.ReadOnlySectionProvider.GetDeletableSegments(segment);
      if (deletableSegments == null)
        throw new InvalidOperationException("ReadOnlySectionProvider.GetDeletableSegments returned null");
      var array = deletableSegments.ToArray();
      int lastIndex = segment.Offset;
      for (int i = 0; i < array.Length; i++) {
        if (array[i].Offset < lastIndex)
          throw new InvalidOperationException("ReadOnlySectionProvider returned incorrect segments (outside of input segment / wrong order)");
        lastIndex = array[i].EndOffset;
      }
      if (lastIndex > segment.EndOffset)
        throw new InvalidOperationException("ReadOnlySectionProvider returned incorrect segments (outside of input segment / wrong order)");
      return array;
    }
    #endregion
    
    #region IndentationStrategy property
    /// <summary>
    /// IndentationStrategy property.
    /// </summary>
    public static readonly DependencyProperty IndentationStrategyProperty =
      DependencyProperty.Register("IndentationStrategy", typeof(IIndentationStrategy), typeof(TextArea),
                                  new FrameworkPropertyMetadata(new DefaultIndentationStrategy()));
    
    /// <summary>
    /// Gets/Sets the indentation strategy used when inserting new lines.
    /// </summary>
    public IIndentationStrategy IndentationStrategy {
      get { return (IIndentationStrategy)GetValue(IndentationStrategyProperty); }
      set { SetValue(IndentationStrategyProperty, value); }
    }
    #endregion
    
    #region OnKeyDown/OnKeyUp
    /// <inheritdoc/>
    protected override void OnPreviewKeyDown(KeyEventArgs e)
    {
      base.OnPreviewKeyDown(e);
      
      if (!e.Handled && e.Key == Key.Insert && this.Options.AllowToggleOverstrikeMode) {
        this.OverstrikeMode = !this.OverstrikeMode;
        e.Handled = true;
        return;
      }
      
      foreach (TextAreaStackedInputHandler h in stackedInputHandlers) {
        if (e.Handled)
          break;
        h.OnPreviewKeyDown(e);
      }
    }
    
    /// <inheritdoc/>
    protected override void OnPreviewKeyUp(KeyEventArgs e)
    {
      base.OnPreviewKeyUp(e);
      foreach (TextAreaStackedInputHandler h in stackedInputHandlers) {
        if (e.Handled)
          break;
        h.OnPreviewKeyUp(e);
      }
    }
    
    // Make life easier for text editor extensions that use a different cursor based on the pressed modifier keys.
    /// <inheritdoc/>
    protected override void OnKeyDown(KeyEventArgs e)
    {
      base.OnKeyDown(e);
      TextView.InvalidateCursorIfMouseWithinTextView();
    }
    
    /// <inheritdoc/>
    protected override void OnKeyUp(KeyEventArgs e)
    {
      base.OnKeyUp(e);
      TextView.InvalidateCursorIfMouseWithinTextView();
    }
    #endregion
    
    #region Hide Mouse Cursor While Typing
    
    bool isMouseCursorHidden;
    
    void AttachTypingEvents()
    {
      // Use the PreviewMouseMove event in case some other editor layer consumes the MouseMove event (e.g. SD's InsertionCursorLayer)
      this.MouseEnter += delegate { ShowMouseCursor(); };
      this.MouseLeave += delegate { ShowMouseCursor(); };
      this.PreviewMouseMove += delegate { ShowMouseCursor(); };
      #if DOTNET4
      this.TouchEnter += delegate { ShowMouseCursor(); };
      this.TouchLeave += delegate { ShowMouseCursor(); };
      this.PreviewTouchMove += delegate { ShowMouseCursor(); };
      #endif
    }
    
    void ShowMouseCursor()
    {
      if (this.isMouseCursorHidden) {
        System.Windows.Forms.Cursor.Show();
        this.isMouseCursorHidden = false;
      }
    }
    
    void HideMouseCursor() {
      if (Options.HideCursorWhileTyping && !this.isMouseCursorHidden && this.IsMouseOver) {
        this.isMouseCursorHidden = true;
        System.Windows.Forms.Cursor.Hide();
      }
    }
    
    #endregion
    
    #region Overstrike mode
    
    /// <summary>
    /// The <see cref="OverstrikeMode"/> dependency property.
    /// </summary>
    public static readonly DependencyProperty OverstrikeModeProperty =
      DependencyProperty.Register("OverstrikeMode", typeof(bool), typeof(TextArea),
                                  new FrameworkPropertyMetadata(Boxes.False));
    
    /// <summary>
    /// Gets/Sets whether overstrike mode is active.
    /// </summary>
    public bool OverstrikeMode {
      get { return (bool)GetValue(OverstrikeModeProperty); }
      set { SetValue(OverstrikeModeProperty, value); }
    }
    
    #endregion
    
    /// <inheritdoc/>
    protected override HitTestResult HitTestCore(PointHitTestParameters hitTestParameters)
    {
      // accept clicks even where the text area draws no background
      return new PointHitTestResult(this, hitTestParameters.HitPoint);
    }
    
    /// <inheritdoc/>
    protected override void OnPropertyChanged(DependencyPropertyChangedEventArgs e)
    {
      base.OnPropertyChanged(e);
      if (e.Property == SelectionBrushProperty
          || e.Property == SelectionBorderProperty
          || e.Property == SelectionForegroundProperty
          || e.Property == SelectionCornerRadiusProperty)
      {
        textView.Redraw();
      } else if (e.Property == OverstrikeModeProperty) {
        caret.UpdateIfVisible();
      }
    }
    
    /// <summary>
    /// Gets the requested service.
    /// </summary>
    /// <returns>Returns the requested service instance, or null if the service cannot be found.</returns>
    public virtual object GetService(Type serviceType)
    {
      return textView.GetService(serviceType);
    }
    
    /// <summary>
    /// Occurs when text inside the TextArea was copied.
    /// </summary>
    public event EventHandler<TextEventArgs> TextCopied;
    
    internal void OnTextCopied(TextEventArgs e)
    {
      if (TextCopied != null)
        TextCopied(this, e);
    }
  }
  
  /// <summary>
  /// EventArgs with text.
  /// </summary>
  [Serializable]
  public class TextEventArgs : EventArgs
  {
    string text;
    
    /// <summary>
    /// Gets the text.
    /// </summary>
    public string Text {
      get {
        return text;
      }
    }
    
    /// <summary>
    /// Creates a new TextEventArgs instance.
    /// </summary>
    public TextEventArgs(string text)
    {
      if (text == null)
        throw new ArgumentNullException("text");
      this.text = text;
    }
  }
}