WeakLineTracker.cs

// 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;

namespace Unity.CodeEditor.Document
{
    /// <summary>
    /// Allows registering a line tracker on a TextDocument using a weak reference from the document to the line tracker.
    /// </summary>
    internal sealed class WeakLineTracker : ILineTracker
    {
        private TextDocument _textDocument;
        private readonly WeakReference _targetObject;

        private WeakLineTracker(TextDocument textDocument, ILineTracker targetTracker)
        {
            _textDocument = textDocument;
            _targetObject = new WeakReference(targetTracker);
        }

        /// <summary>
        /// Registers the <paramref name="targetTracker"/> as line tracker for the <paramref name="textDocument"/>.
        /// A weak reference to the target tracker will be used, and the WeakLineTracker will deregister itself
        /// when the target tracker is garbage collected.
        /// </summary>
        internal static WeakLineTracker Register(TextDocument textDocument, ILineTracker targetTracker)
        {
            if (textDocument == null)
                throw new ArgumentNullException(nameof(textDocument));
            if (targetTracker == null)
                throw new ArgumentNullException(nameof(targetTracker));
            var wlt = new WeakLineTracker(textDocument, targetTracker);
            textDocument.LineTrackers.Add(wlt);
            return wlt;
        }

        /// <summary>
        /// Deregisters the weak line tracker.
        /// </summary>
        internal void Deregister()
        {
            if (_textDocument != null)
            {
                _textDocument.LineTrackers.Remove(this);
                _textDocument = null;
            }
        }

        void ILineTracker.BeforeRemoveLine(DocumentLine line)
        {
            if (_targetObject.Target is ILineTracker targetTracker)
                targetTracker.BeforeRemoveLine(line);
            else
                Deregister();
        }

        void ILineTracker.SetLineLength(DocumentLine line, int newTotalLength)
        {
            if (_targetObject.Target is ILineTracker targetTracker)
                targetTracker.SetLineLength(line, newTotalLength);
            else
                Deregister();
        }

        void ILineTracker.LineInserted(DocumentLine insertionPos, DocumentLine newLine)
        {
            if (_targetObject.Target is ILineTracker targetTracker)
                targetTracker.LineInserted(insertionPos, newLine);
            else
                Deregister();
        }

        void ILineTracker.RebuildDocument()
        {
            if (_targetObject.Target is ILineTracker targetTracker)
                targetTracker.RebuildDocument();
            else
                Deregister();
        }

        void ILineTracker.ChangeComplete(DocumentChangeEventArgs e)
        {
            if (_targetObject.Target is ILineTracker targetTracker)
                targetTracker.ChangeComplete(e);
            else
                Deregister();
        }
    }
}