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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using MS.Internal;
//
// Description: A pair of TextPositions used to denote a run of TextContainer content.
//
namespace System.Windows.Documents
{
/// <summary>
/// A pair of TextPositions used to denote a run of TextContainer content.
/// </summary>
// make this public when we finish the work for
// grouping TextEditor/TextContainer change events.
internal struct TextSegment
{
//------------------------------------------------------
//
// Constructors
//
//------------------------------------------------------
#region Constructors
/// <summary>
/// Constructor.
/// </summary>
/// <param name="startPosition">
/// Position preceeding the TextSegment's content.
/// </param>
/// <param name="endPosition">
/// Position following the TextSegment's content.
/// </param>
/// <remarks>
/// If startPosition or endPosition are TextNavigators (derived from
/// TextPointer), the TextSegment constructor will store new TextPointer
/// instances internally. The values returned by the Start and End
/// properties are always immutable TextPositions.
/// </remarks>
internal TextSegment(ITextPointer startPosition, ITextPointer endPosition) :
this(startPosition, endPosition, false)
{
}
/// <summary>
/// Constructor.
/// </summary>
/// <param name="startPosition">
/// Position preceeding the TextSegment's content.
/// </param>
/// <param name="endPosition">
/// Position following the TextSegment's content.
/// </param>
/// <param name="preserveLogicalDirection">
/// Whether preserves LogicalDirection of start and end positions.
/// </param>
internal TextSegment(ITextPointer startPosition, ITextPointer endPosition, bool preserveLogicalDirection)
{
ValidationHelper.VerifyPositionPair(startPosition, endPosition);
if (startPosition.CompareTo(endPosition) == 0)
{
// To preserve segment emptiness
// we use the same instance of a pointer
// for both segment ends.
_start = startPosition.GetFrozenPointer(startPosition.LogicalDirection);
_end = _start;
}
else
{
Invariant.Assert(startPosition.CompareTo(endPosition) < 0);
_start = startPosition.GetFrozenPointer(preserveLogicalDirection ? startPosition.LogicalDirection : LogicalDirection.Backward);
_end = endPosition.GetFrozenPointer(preserveLogicalDirection ? endPosition.LogicalDirection : LogicalDirection.Forward);
}
}
#endregion Constructors
//------------------------------------------------------
//
// Internal Methods
//
//------------------------------------------------------
#region Internal Methods
/// <summary>
/// returns true if the segment contains a given position
/// </summary>
// need to accound for position.LogicalDirection.
internal bool Contains(ITextPointer position)
{
return (!this.IsNull && this._start.CompareTo(position) <= 0 && position.CompareTo(this._end) <= 0);
}
#endregion Internal Methods
//------------------------------------------------------
//
// Internal Properties
//
//------------------------------------------------------
#region Internal Properties
/// <summary>
/// Position preceeding the TextSegment's content.
/// </summary>
internal ITextPointer Start
{
get
{
return _start;
}
}
/// <summary>
/// Position following the TextSegment's content.
/// </summary>
internal ITextPointer End
{
get
{
return _end;
}
}
internal bool IsNull
{
get
{
return _start == null || _end == null;
}
}
#endregion Internal Properties
/// <summary>
/// The "TextSegment.Null" value.
/// </summary>
/// <remarks>
/// TextSegtemt.Null is used in contexts where text segment is missing.
/// </remarks>
internal static readonly TextSegment Null = new TextSegment();
//------------------------------------------------------
//
// Private Fields
//
//------------------------------------------------------
#region Private Fields
// Position preceeding the TextSegment's content.
private readonly ITextPointer _start;
// Position following the TextSegment's content.
private readonly ITextPointer _end;
#endregion Private Fields
}
}
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