added infantry taking cover behavior

OpenRa.Game/Traits/TakeCover.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using OpenRa.Game.GameRules;
+
+namespace OpenRa.Game.Traits
+{
+	// infantry prone behavior
+	class TakeCover : ITick, INotifyDamageEx, IDamageModifier, ISpeedModifier
+	{
+		const int defaultProneTime = 100;	/* ticks, =4s */
+		const float proneDamage = .5f;
+		const float proneSpeed = .5f;
+
+		int remainingProneTime = 0;
+
+		public bool IsProne { get { return remainingProneTime > 0; } }
+
+		public TakeCover(Actor self) {}
+
+		public void Damaged(Actor self, int damage, WarheadInfo warhead)
+		{
+			remainingProneTime = defaultProneTime;
+		}
+
+		public void Tick(Actor self)
+		{
+			if (IsProne)
+				--remainingProneTime;
+		}
+
+		public float GetDamageModifier()
+		{
+			return IsProne ? proneDamage : 1f;
+		}
+
+		public float GetSpeedModifier()
+		{
+			return IsProne ? proneSpeed : 1f;
+		}
+	}
+}