Add ScriptLobbyDropdown trait and lua API.

OpenRA.Mods.Common/OpenRA.Mods.Common.csproj

@@ -756,6 +756,7 @@
     <Compile Include="UtilityCommands\ListMSCabContentsCommand.cs" />
     <Compile Include="FileFormats\MSCabCompression.cs" />
     <Compile Include="UtilityCommands\OutputActorMiniYamlCommand.cs" />
+    <Compile Include="Traits\World\ScriptLobbyDropdown.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <PropertyGroup>

OpenRA.Mods.Common/Scripting/Global/MapGlobal.cs

@@ -107,6 +107,18 @@ namespace OpenRA.Mods.Common.Scripting
 		[Desc("Returns the difficulty selected by the player before starting the mission.")]
 		public string Difficulty { get { return Context.World.LobbyInfo.GlobalSettings.Difficulty; } }
 
+		[Desc("Returns the value of a `ScriptLobbyDropdown` selected in the game lobby.")]
+		public LuaValue LobbyOption(string id)
+		{
+			var option = Context.World.WorldActor.TraitsImplementing<ScriptLobbyDropdown>()
+				.FirstOrDefault(sld => sld.Info.ID == id);
+
+			if (option == null)
+				throw new YamlException("A ScriptLobbyDropdown with ID `" + id + "` was not found.");
+
+			return option.Value;
+		}
+
 		[Desc("Returns a table of all the actors that were specified in the map file.")]
 		public Actor[] NamedActors { get { return sma.Actors.Values.ToArray(); } }
 

OpenRA.Mods.Common/Traits/World/ScriptLobbyDropdown.cs

@@ -0,0 +1,66 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2016 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.Collections.Generic;
+using System.Linq;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits
+{
+	[Desc("Controls the map difficulty, tech level, and short game lobby options.")]
+	public class ScriptLobbyDropdownInfo : ITraitInfo, ILobbyOptions
+	{
+		[FieldLoader.Require]
+		[Desc("Internal id for this option.")]
+		public readonly string ID = null;
+
+		[FieldLoader.Require]
+		[Desc("Display name for this option.")]
+		public readonly string Label = null;
+
+		[FieldLoader.Require]
+		[Desc("Default option key in the `Values` list.")]
+		public readonly string Default = null;
+
+		[FieldLoader.Require]
+		[Desc("Difficulty levels supported by the map.")]
+		public readonly Dictionary<string, string> Values = null;
+
+		[Desc("Prevent the option from being changed from its default value.")]
+		public readonly bool Locked = false;
+
+		IEnumerable<LobbyOption> ILobbyOptions.LobbyOptions(Ruleset rules)
+		{
+			yield return new LobbyOption(ID, Label,
+				new ReadOnlyDictionary<string, string>(Values),
+					Default, Locked);
+		}
+
+		public object Create(ActorInitializer init) { return new ScriptLobbyDropdown(this); }
+	}
+
+	public class ScriptLobbyDropdown : INotifyCreated
+	{
+		public readonly ScriptLobbyDropdownInfo Info;
+
+		public string Value { get; private set; }
+
+		public ScriptLobbyDropdown(ScriptLobbyDropdownInfo info)
+		{
+			Info = info;
+		}
+
+		void INotifyCreated.Created(Actor self)
+		{
+			Value = self.World.LobbyInfo.GlobalSettings.OptionOrDefault(Info.ID, Info.Default);
+		}
+	}
+}