UnityDispatcher.cs

// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the MIT license.
using System;
using System.Collections.Generic;
using UnityEngine;

namespace Microsoft.Unity
{
    /// <summary>
    /// A helper class for dispatching actions to run on various Unity threads.
    /// </summary>
    public class UnityDispatcher : MonoBehaviour
    {
        #region Member Variables
        static private UnityDispatcher instance;
        static private Queue<Action> queue = new Queue<Action>(8);
        static private volatile bool queued = false;
        #endregion // Member Variables

        #region Internal Methods
        [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)]
        static private void Initialize()
        {
            lock (queue)
            {
                if (instance == null)
                {
                    instance = new GameObject("Dispatcher").AddComponent<UnityDispatcher>();
                    DontDestroyOnLoad(instance.gameObject);
                }
            }
        }
        #endregion // Internal Methods

        #region Unity Overrides
        protected virtual void Update()
        {
            // Action placeholder
            Action action = null;

            // Do this as long as there's something in the queue
            while (queued)
            {
                // Lock only long enough to take an item
                lock (queue)
                {
                    // Get the next action
                    action = queue.Dequeue();

                    // Have we exhausted the queue?
                    if (queue.Count == 0) { queued = false; }
                }

                // Execute the action outside of the lock
                action();
            }
        }
        #endregion // Unity Overrides

        #region Public Methods
        /// <summary>
        /// Schedules the specified action to be run on Unity's main thread.
        /// </summary>
        /// <param name="action">
        /// The action to run.
        /// </param>
        static public void InvokeOnAppThread(Action action)
        {
            // Validate
            if (action == null) throw new ArgumentNullException(nameof(action));

            // Lock to be thread-safe
            lock (queue)
            {
                // Add the action
                queue.Enqueue(action);

                // Action is in the queue
                queued = true;
            }
        }
        #endregion // Public Methods
    }

    // #endif // Not using UWP-specific version anymore
}