Add a UnitUpgradeManager trait.

This introduces support for timed upgrades, starting with crate buffs.

OpenRA.Mods.RA/TimedUpgradeBar.cs

@@ -0,0 +1,58 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2014 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. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using System.Drawing;
+using System.Linq;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.RA
+{
+	[Desc("Visualizes the remaining time for an upgrade.")]
+	class TimedUpgradeBarInfo : ITraitInfo, Requires<UpgradeManagerInfo>
+	{
+		[Desc("Upgrade that this bar corresponds to")]
+		public readonly string Upgrade = null;
+
+		public readonly Color Color = Color.Red;
+
+		public object Create(ActorInitializer init) { return new TimedUpgradeBar(init.self, this); }
+	}
+
+	class TimedUpgradeBar : ISelectionBar
+	{
+		readonly TimedUpgradeBarInfo info;
+		readonly Actor self;
+		float value;
+
+		public TimedUpgradeBar(Actor self, TimedUpgradeBarInfo info)
+		{
+			this.self = self;
+			this.info = info;
+
+			self.Trait<UpgradeManager>().RegisterWatcher(info.Upgrade, Update);
+		}
+
+		public void Update(int duration, int remaining)
+		{
+			value = remaining * 1f / duration;
+		}
+
+		public float GetValue()
+		{
+			if (!self.Owner.IsAlliedWith(self.World.RenderPlayer))
+				return 0;
+
+			return value;
+		}
+
+		public Color GetColor() { return info.Color; }
+	}
+}