WIP of porting radegast viewer source code

Assets/UnityMainThreadDispatcher.cs

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+/*
+Copyright 2015 Pim de Witte All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+using UnityEngine;
+using System.Collections;
+using System.Collections.Generic;
+using System;
+using System.Threading.Tasks;
+
+/// Author: Pim de Witte (pimdewitte.com) and contributors, https://github.com/PimDeWitte/UnityMainThreadDispatcher
+/// <summary>
+/// A thread-safe class which holds a queue with actions to execute on the next Update() method. It can be used to make calls to the main thread for
+/// things such as UI Manipulation in Unity. It was developed for use in combination with the Firebase Unity plugin, which uses separate threads for event handling
+/// </summary>
+public class UnityMainThreadDispatcher : MonoBehaviour
+{
+
+	private static readonly Queue<Action> _executionQueue = new Queue<Action>();
+
+	public void Update()
+	{
+		lock (_executionQueue)
+		{
+			while (_executionQueue.Count > 0)
+			{
+				_executionQueue.Dequeue().Invoke();
+			}
+		}
+	}
+
+	/// <summary>
+	/// Locks the queue and adds the IEnumerator to the queue
+	/// </summary>
+	/// <param name="action">IEnumerator function that will be executed from the main thread.</param>
+	public void Enqueue(IEnumerator action)
+	{
+		lock (_executionQueue)
+		{
+			_executionQueue.Enqueue(() => {
+				StartCoroutine(action);
+			});
+		}
+	}
+
+	/// <summary>
+	/// Locks the queue and adds the Action to the queue
+	/// </summary>
+	/// <param name="action">function that will be executed from the main thread.</param>
+	public void Enqueue(Action action)
+	{
+		Enqueue(ActionWrapper(action));
+	}
+
+	/// <summary>
+	/// Locks the queue and adds the Action to the queue, returning a Task which is completed when the action completes
+	/// </summary>
+	/// <param name="action">function that will be executed from the main thread.</param>
+	/// <returns>A Task that can be awaited until the action completes</returns>
+	public Task EnqueueAsync(Action action)
+	{
+		var tcs = new TaskCompletionSource<bool>();
+
+		void WrappedAction()
+		{
+			try
+			{
+				action();
+				tcs.TrySetResult(true);
+			}
+			catch (Exception ex)
+			{
+				tcs.TrySetException(ex);
+			}
+		}
+
+		Enqueue(ActionWrapper(WrappedAction));
+		return tcs.Task;
+	}
+
+
+	IEnumerator ActionWrapper(Action a)
+	{
+		a();
+		yield return null;
+	}
+
+
+	private static UnityMainThreadDispatcher _instance = null;
+
+	public static bool Exists()
+	{
+		return _instance != null;
+	}
+
+	public static UnityMainThreadDispatcher Instance()
+	{
+		if (!Exists())
+		{
+			throw new Exception("UnityMainThreadDispatcher could not find the UnityMainThreadDispatcher object. Please ensure you have added the MainThreadExecutor Prefab to your scene.");
+		}
+		return _instance;
+	}
+
+
+	void Awake()
+	{
+		if (_instance == null)
+		{
+			_instance = this;
+			DontDestroyOnLoad(this.gameObject);
+		}
+	}
+
+	void OnDestroy()
+	{
+		_instance = null;
+	}
+
+
+}