Unhardcode modchooser mod for content installation.

OpenRA.Game/Game.cs

@@ -379,16 +379,12 @@ namespace OpenRA
 			ModData = new ModData(Mods[mod], Mods, true);
 			ExternalMods.Register(ModData.Manifest);
 
+			if (!ModData.LoadScreen.BeforeLoad())
+				return;
+
 			using (new PerfTimer("LoadMaps"))
 				ModData.MapCache.LoadMaps();
 
-			// Mod assets are missing!
-			if (!ModData.LoadScreen.RequiredContentIsInstalled())
-			{
-				InitializeMod("modchooser", new Arguments());
-				return;
-			}
-
 			ModData.InitializeLoaders(ModData.DefaultFileSystem);
 			Renderer.InitializeFonts(ModData);
 

OpenRA.Game/ModData.cs

@@ -222,9 +222,19 @@ namespace OpenRA
 
 	public interface ILoadScreen : IDisposable
 	{
+		/// <summary>Initializes the loadscreen with yaml data from the LoadScreen block in mod.yaml.</summary>
 		void Init(ModData m, Dictionary<string, string> info);
+
+		/// <summary>Called at arbitrary times during mod load to rerender the loadscreen.</summary>
 		void Display();
-		bool RequiredContentIsInstalled();
+
+		/// <summary>
+		/// Called before loading the mod assets.
+		/// Returns false if mod loading should be aborted (e.g. switching to another mod instead).
+		/// </summary>
+		bool BeforeLoad();
+
+		/// <summary>Called when the engine expects to connect to a server/replay or load the shellmap.</summary>
 		void StartGame(Arguments args);
 	}
 }

OpenRA.Mods.Common/LoadScreens/BlankLoadScreen.cs

@@ -109,12 +109,23 @@ namespace OpenRA.Mods.Common.LoadScreens
 			GC.SuppressFinalize(this);
 		}
 
-		public bool RequiredContentIsInstalled()
+		public bool BeforeLoad()
 		{
+			// If a ModContent section is defined then we need to make sure that the
+			// required content is installed or switch to the defined content installer.
+			if (!modData.Manifest.Contains<ModContent>())
+				return true;
+
 			var content = modData.Manifest.Get<ModContent>();
-			return content.Packages
+			var contentInstalled = content.Packages
 				.Where(p => p.Value.Required)
 				.All(p => p.Value.TestFiles.All(f => File.Exists(Platform.ResolvePath(f))));
+
+			if (contentInstalled)
+				return true;
+
+			Game.InitializeMod(content.ContentInstallerMod, new Arguments());
+			return false;
 		}
 	}
 }

OpenRA.Mods.Common/LoadScreens/ModChooserLoadScreen.cs

@@ -58,7 +58,7 @@ namespace OpenRA.Mods.Common.LoadScreens
 				sprite.Sheet.Dispose();
 		}
 
-		public bool RequiredContentIsInstalled()
+		public bool BeforeLoad()
 		{
 			return true;
 		}

OpenRA.Mods.Common/ModContent.cs

@@ -85,6 +85,7 @@ namespace OpenRA
 		public readonly string InstallPromptMessage;
 		public readonly string QuickDownload;
 		public readonly string HeaderMessage;
+		public readonly string ContentInstallerMod = "modchooser";
 
 		[FieldLoader.LoadUsing("LoadPackages")]
 		public readonly Dictionary<string, ModPackage> Packages = new Dictionary<string, ModPackage>();