Extend Target with world-coordinate range checks.

OpenRA.Game/Traits/Target.cs

@@ -8,11 +8,15 @@
  */
 #endregion
 
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
 namespace OpenRA.Traits
 {
-	public struct Target		// a target: either an actor, or a fixed location.
+	public struct Target
 	{
-		public static Target[] NoTargets = {};
+		public static readonly Target[] NoTargets = {};
 
 		Actor actor;
 		PPos pos;
@@ -43,6 +47,48 @@ namespace OpenRA.Traits
 		public PPos PxPosition { get { return IsActor ? actor.Trait<IHasLocation>().PxPosition : pos; } }
 		public PPos CenterLocation { get { return PxPosition; } }
 
+		// Representative position - see Positions for the full set of targetable positions.
+		public WPos CenterPosition
+		{
+			get
+			{
+				if (!IsValid)
+					throw new InvalidOperationException("Attempting to query the position of an invalid Target");
+
+				return actor != null ? actor.CenterPosition : pos.ToWPos(0);
+			}
+		}
+
+		// Positions available to target for range checks
+		static readonly WPos[] NoPositions = {};
+		public IEnumerable<WPos> Positions
+		{
+			get
+			{
+				if (!IsValid)
+					return NoPositions;
+
+				if (actor == null)
+					return new []{pos.ToWPos(0)};
+
+				var targetable = actor.TraitOrDefault<ITargetable>();
+				if (targetable == null)
+					return new []{actor.CenterPosition};
+
+				return targetable.TargetableCells(actor).Select(c => c.CenterPosition);
+			}
+		}
+
+		public bool IsInRange(WPos origin, WRange range)
+		{
+			if (!IsValid)
+				return false;
+
+			// Target ranges are calculated in 2D, so ignore height differences
+			return Positions.Any(t => (t.X - origin.X)*(t.X - origin.X) +
+				(t.Y - origin.Y)*(t.Y - origin.Y) <= range.Range*range.Range);
+		}
+
 		public Actor Actor { get { return IsActor ? actor : null; } }
 		public bool IsActor { get { return actor != null && !actor.Destroyed; } }
 	}