source: branches/RemoveBackwardsCompatibility/HeuristicLab.ExtLibs/HeuristicLab.AvalonEdit/5.0.1/AvalonEdit-5.0.1/Document/ITextAnchor.cs @ 14113

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// 
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using System;
using ICSharpCode.NRefactory;

namespace ICSharpCode.AvalonEdit.Document
{
  #if !NREFACTORY
  /// <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="ITextAnchor.Offset"/> property to get the offset from a text anchor.
  /// Use the <see cref="IDocument.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="ITextAnchor.Offset"/> property also runs in O(lg N).</para>
  /// </remarks>
  /// <example>
  /// Usage:
  /// <code>TextAnchor anchor = document.CreateAnchor(offset);
  /// ChangeMyDocument();
  /// int newOffset = anchor.Offset;
  /// </code>
  /// </example>
  public interface ITextAnchor
  {
    /// <summary>
    /// Gets the text location of this anchor.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
    TextLocation Location { get; }
    
    /// <summary>
    /// Gets the offset of the text anchor.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
    int Offset { get; }
    
    /// <summary>
    /// Controls how the anchor moves.
    /// </summary>
    /// <remarks>Anchor movement is ambiguous if text is inserted exactly at the anchor's location.
    /// Does the anchor stay before the inserted text, or does it move after it?
    /// The property <see cref="MovementType"/> will be used to determine which of these two options the anchor will choose.
    /// The default value is <see cref="AnchorMovementType.Default"/>.</remarks>
    AnchorMovementType MovementType { get; set; }
    
    /// <summary>
    /// <para>
    /// Specifies whether the anchor survives deletion of the text containing it.
    /// </para><para>
    /// <c>false</c>: The anchor is deleted when the a selection that includes the anchor is deleted.
    /// <c>true</c>: The anchor is not deleted.
    /// </para>
    /// </summary>
    /// <remarks><inheritdoc cref="IsDeleted" /></remarks>
    bool SurviveDeletion { get; set; }
    
    /// <summary>
    /// Gets whether the anchor was deleted.
    /// </summary>
    /// <remarks>
    /// <para>When a piece of text containing an anchor is removed, then that anchor will be deleted.
    /// First, the <see cref="IsDeleted"/> property is set to true on all deleted anchors,
    /// then the <see cref="Deleted"/> events are raised.
    /// You cannot retrieve the offset from an anchor that has been deleted.</para>
    /// <para>This deletion behavior might be useful when using anchors for building a bookmark feature,
    /// but in other cases you want to still be able to use the anchor. For those cases, set <c><see cref="SurviveDeletion"/> = true</c>.</para>
    /// </remarks>
    bool IsDeleted { get; }
    
    /// <summary>
    /// Occurs after the anchor was deleted.
    /// </summary>
    /// <remarks>
    /// <inheritdoc cref="IsDeleted" />
    /// <para>Due to the 'weak reference' nature of text anchors, you will receive
    /// the Deleted event only while your code holds a reference to the TextAnchor object.
    /// </para>
    /// </remarks>
    event EventHandler Deleted;
    
    /// <summary>
    /// Gets the line number of the anchor.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
    int Line { get; }
    
    /// <summary>
    /// Gets the column number of this anchor.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when trying to get the Offset from a deleted anchor.</exception>
    int Column { get; }
  }
  
  /// <summary>
  /// Defines how a text anchor moves.
  /// </summary>
  public enum AnchorMovementType
  {
    /// <summary>
    /// When text is inserted at the anchor position, the type of the insertion
    /// determines where the caret moves to. For normal insertions, the anchor will move
    /// after the inserted text.
    /// </summary>
    Default,
    /// <summary>
    /// Behaves like a start marker - when text is inserted at the anchor position, the anchor will stay
    /// before the inserted text.
    /// </summary>
    BeforeInsertion,
    /// <summary>
    /// Behave like an end marker - when text is insered at the anchor position, the anchor will move
    /// after the inserted text.
    /// </summary>
    AfterInsertion
  }
  #endif
}