Fix #17230: Dummy audio output class

OpenRA.Platforms.Default/DefaultPlatform.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System;
 using OpenRA.Primitives;
 
 namespace OpenRA.Platforms.Default
@@ -22,7 +23,15 @@ namespace OpenRA.Platforms.Default
 
 		public ISoundEngine CreateSound(string device)
 		{
-			return new OpenAlSoundEngine(device);
+			try
+			{
+				return new OpenAlSoundEngine(device);
+			}
+			catch (InvalidOperationException e)
+			{
+				Log.Write("sound", "Failed to initialize OpenAL device. Error was {0}", e);
+				return new DummySoundEngine(device);
+			}
 		}
 
 		public IFont CreateFont(byte[] data)

OpenRA.Platforms.Default/DummySoundEngine.cs

@@ -0,0 +1,75 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2019 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.IO;
+
+namespace OpenRA.Platforms.Default
+{
+	sealed class DummySoundEngine : ISoundEngine
+	{
+		public bool Dummy { get { return true; } }
+
+		public SoundDevice[] AvailableDevices()
+		{
+			var defaultDevices = new[]
+			{
+				new SoundDevice(null, "Default Output"),
+			};
+
+			return defaultDevices;
+		}
+
+		public DummySoundEngine(string deviceName) { }
+
+		public ISoundSource AddSoundSourceFromMemory(byte[] data, int channels, int sampleBits, int sampleRate)
+		{
+			return new NullSoundSource();
+		}
+
+		public ISound Play2D(ISoundSource soundSource, bool loop, bool relative, WPos pos, float volume, bool attenuateVolume)
+		{
+			return new NullSound();
+		}
+
+		public ISound Play2DStream(Stream stream, int channels, int sampleBits, int sampleRate, bool loop, bool relative, WPos pos, float volume)
+		{
+			return null;
+		}
+
+		public float Volume
+		{
+			get { return 0; }
+			set { }
+		}
+
+		public void PauseSound(ISound sound, bool paused) { }
+		public void SetAllSoundsPaused(bool paused) { }
+		public void SetSoundVolume(float volume, ISound music, ISound video) { }
+		public void StopSound(ISound sound) { }
+		public void StopAllSounds() { }
+		public void SetListenerPosition(WPos position) { }
+		public void Dispose() { }
+	}
+
+	class NullSoundSource : ISoundSource
+	{
+		public void Dispose() { }
+	}
+
+	class NullSound : ISound
+	{
+		public float Volume { get; set; }
+		public float SeekPosition { get { return 0; } }
+		public bool Complete { get { return false; } }
+
+		public void SetPosition(WPos position) { }
+	}
+}

OpenRA.Platforms.Default/OpenAlSoundEngine.cs

@@ -23,6 +23,8 @@ namespace OpenRA.Platforms.Default
 {
 	sealed class OpenAlSoundEngine : ISoundEngine
 	{
+		public bool Dummy { get { return false; } }
+
 		public SoundDevice[] AvailableDevices()
 		{
 			var defaultDevices = new[]