Extract load screen sheet handling into a superclass.

OpenRA.Mods.Common/LoadScreens/SheetLoadScreen.cs

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+#region Copyright & License Information
+/*
+ * Copyright 2007-2020 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.Diagnostics;
+using OpenRA.Graphics;
+
+namespace OpenRA.Mods.Common.LoadScreens
+{
+	public abstract class SheetLoadScreen : BlankLoadScreen
+	{
+		Stopwatch lastUpdate;
+
+		protected Dictionary<string, string> Info { get; private set; }
+		Sheet sheet;
+
+		public override void Init(ModData modData, Dictionary<string, string> info)
+		{
+			base.Init(modData, info);
+			Info = info;
+		}
+
+		public abstract void DisplayInner(Renderer r, Sheet s);
+
+		public override void Display()
+		{
+			// Limit load screens to at most 5 FPS
+			if (Game.Renderer == null || (lastUpdate != null && lastUpdate.Elapsed.TotalSeconds < 0.2))
+				return;
+
+			// Start the timer on the first render
+			if (lastUpdate == null)
+				lastUpdate = Stopwatch.StartNew();
+
+			if (sheet == null && Info.ContainsKey("Image"))
+				using (var stream = ModData.DefaultFileSystem.Open(Info["Image"]))
+					sheet = new Sheet(SheetType.BGRA, stream);
+
+			Game.Renderer.BeginUI();
+			DisplayInner(Game.Renderer, sheet);
+			Game.Renderer.EndFrame(new NullInputHandler());
+
+			lastUpdate.Restart();
+		}
+
+		protected override void Dispose(bool disposing)
+		{
+			if (disposing && sheet != null)
+				sheet.Dispose();
+
+			base.Dispose(disposing);
+		}
+	}
+}