source: branches/3107_LearningALPS/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Document/TextAnchor.cs @ 18242

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using System;
using ICSharpCode.AvalonEdit.Utils;
using ICSharpCode.NRefactory;
using ICSharpCode.NRefactory.Editor;
using ICSharpCode.AvalonEdit.Document;

namespace ICSharpCode.AvalonEdit.Document
{
  /// <summary>
  /// The TextAnchor class references an offset (a position between two characters).
  /// It automatically updates the offset when text is inserted/removed in front of the anchor.
  /// </summary>
  /// <remarks>
  /// <para>Use the <see cref="Offset"/> property to get the offset from a text anchor.
  /// Use the <see cref="TextDocument.CreateAnchor"/> method to create an anchor from an offset.
  /// </para>
  /// <para>
  /// The document will automatically update all text anchors; and because it uses weak references to do so,
  /// the garbage collector can simply collect the anchor object when you don't need it anymore.
  /// </para>
  /// <para>Moreover, the document is able to efficiently update a large number of anchors without having to look
  /// at each anchor object individually. Updating the offsets of all anchors usually only takes time logarithmic
  /// to the number of anchors. Retrieving the <see cref="Offset"/> property also runs in O(lg N).</para>
  /// <inheritdoc cref="IsDeleted" />
  /// <inheritdoc cref="MovementType" />
  /// <para>If you want to track a segment, you can use the <see cref="AnchorSegment"/> class which
  /// implements <see cref="ISegment"/> using two text anchors.</para>
  /// </remarks>
  /// <example>
  /// Usage:
  /// <code>TextAnchor anchor = document.CreateAnchor(offset);
  /// ChangeMyDocument();
  /// int newOffset = anchor.Offset;
  /// </code>
  /// </example>
  public sealed class TextAnchor : ITextAnchor
  {
    readonly TextDocument document;
    internal TextAnchorNode node;
    
    internal TextAnchor(TextDocument document)
    {
      this.document = document;
    }
    
    /// <summary>
    /// Gets the document owning the anchor.
    /// </summary>
    public TextDocument Document {
      get { return document; }
    }
    
    /// <inheritdoc/>
    public AnchorMovementType MovementType { get; set; }
    
    /// <inheritdoc/>
    public bool SurviveDeletion { get; set; }
    
    /// <inheritdoc/>
    public bool IsDeleted {
      get {
        document.DebugVerifyAccess();
        return node == null;
      }
    }
    
    /// <inheritdoc/>
    public event EventHandler Deleted;
    
    internal void OnDeleted(DelayedEvents delayedEvents)
    {
      node = null;
      delayedEvents.DelayedRaise(Deleted, this, EventArgs.Empty);
    }
    
    /// <summary>
    /// Gets the offset of the text anchor.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
    public int Offset {
      get {
        document.DebugVerifyAccess();
        
        TextAnchorNode n = this.node;
        if (n == null)
          throw new InvalidOperationException();
        
        int offset = n.length;
        if (n.left != null)
          offset += n.left.totalLength;
        while (n.parent != null) {
          if (n == n.parent.right) {
            if (n.parent.left != null)
              offset += n.parent.left.totalLength;
            offset += n.parent.length;
          }
          n = n.parent;
        }
        return offset;
      }
    }
    
    /// <summary>
    /// Gets the line number of the anchor.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
    public int Line {
      get {
        return document.GetLineByOffset(this.Offset).LineNumber;
      }
    }
    
    /// <summary>
    /// Gets the column number of this anchor.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
    public int Column {
      get {
        int offset = this.Offset;
        return offset - document.GetLineByOffset(offset).Offset + 1;
      }
    }
    
    /// <summary>
    /// Gets the text location of this anchor.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
    public TextLocation Location {
      get {
        return document.GetLocation(this.Offset);
      }
    }
    
    /// <inheritdoc/>
    public override string ToString()
    {
      return "[TextAnchor Offset=" + Offset + "]";
    }
  }
}