Introduce a Targetable trait; Subs can attack bridges; May introduce subtle bugs due to previous stupid assumption that !selectable == !attackable.

OpenRA.Game/Actor.cs

@@ -119,8 +119,8 @@ namespace OpenRA
 				return null;
 
 			var underCursor = World.FindUnitsAtMouse(mi.Location)
-				.Where(a => a.Info.Traits.Contains<SelectableInfo>())
-				.OrderByDescending(a => a.Info.Traits.Get<SelectableInfo>().Priority)
+				//.Where(a => a.Info.Traits.Contains<SelectableInfo>())
+				.OrderByDescending(a => a.Info.Traits.Contains<SelectableInfo>() ? a.Info.Traits.Get<SelectableInfo>().Priority : int.MinValue)
 				.FirstOrDefault();
 			
 			return traits.WithInterface<IIssueOrder>()

OpenRA.Game/OpenRA.Game.csproj

@@ -228,6 +228,7 @@
     <Compile Include="Widgets\ViewportScrollControllerWidget.cs" />
     <Compile Include="Traits\Player\DeveloperMode.cs" />
     <Compile Include="Traits\RevealsShroud.cs" />
+    <Compile Include="Traits\Targetable.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\OpenRA.FileFormats\OpenRA.FileFormats.csproj">

OpenRA.Game/Traits/Building.cs

@@ -22,7 +22,6 @@ namespace OpenRA.Traits
 	{
 		public readonly int HP = 0;
 		public readonly ArmorType Armor = ArmorType.none;
-		public readonly string[] TargetType = {"Ground"};
 	}
 
 	public class BuildingInfo : OwnedActorInfo, ITraitInfo

OpenRA.Game/Traits/Targetable.cs

@@ -0,0 +1,26 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2010 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 LICENSE.
+ */
+#endregion
+
+using System.Drawing;
+using OpenRA.Graphics;
+using System.Linq;
+
+namespace OpenRA.Traits
+{
+	public class TargetableInfo : TraitInfo<Targetable>
+	{
+		public readonly string[] TargetTypes = {};
+	}
+
+	public class Targetable
+	{
+		
+	}
+}

OpenRA.Game/Widgets/WorldInteractionControllerWidget.cs

@@ -14,6 +14,7 @@ using System.Linq;
 using OpenRA.FileFormats;
 using OpenRA.Orders;
 using OpenRA.Traits;
+using System.Collections.Generic;
 
 namespace OpenRA.Widgets
 {
@@ -36,7 +37,7 @@ namespace OpenRA.Widgets
 			Game.Renderer.LineRenderer.DrawLine(a + b + c, a + c, Color.White, Color.White);
 			Game.Renderer.LineRenderer.DrawLine(a, a + c, Color.White, Color.White);
 
-			foreach (var u in world.SelectActorsInBox(selbox.Value.First, selbox.Value.Second))
+			foreach (var u in SelectActorsInBox(world, selbox.Value.First, selbox.Value.Second))
 				world.WorldRenderer.DrawSelectionBox(u, Color.Yellow);
 			
 			Game.Renderer.LineRenderer.Flush();
@@ -60,7 +61,7 @@ namespace OpenRA.Widgets
 			{
 				if (world.OrderGenerator is UnitOrderGenerator)
 				{
-					var newSelection = Game.world.SelectActorsInBox(Game.CellSize * dragStart, Game.CellSize * xy);
+					var newSelection = SelectActorsInBox(world, Game.CellSize * dragStart, Game.CellSize * xy);
 					world.Selection.Combine(world, newSelection, mi.Modifiers.HasModifier(Modifiers.Shift), dragStart == xy);
 				}
 
@@ -170,6 +171,17 @@ namespace OpenRA.Widgets
 			Game.viewport.Center(world.Selection.Actors);
 		}
 		
+		IEnumerable<Actor> SelectActorsInBox(World world, float2 a, float2 b)
+		{
+			return world.FindUnits(a, b)
+				.Where( x => x.traits.Contains<Selectable>() && x.IsVisible() )
+				.GroupBy(x => (x.Owner == world.LocalPlayer) ? x.Info.Traits.Get<SelectableInfo>().Priority : 0)
+				.OrderByDescending(g => g.Key)
+				.Select( g => g.AsEnumerable() )
+				.DefaultIfEmpty( new Actor[] {} )
+				.FirstOrDefault();
+		}
+		
 		public override Widget Clone() { return new WorldInteractionControllerWidget(this); }
 	}
 }

OpenRA.Game/WorldUtils.cs

@@ -81,17 +81,6 @@ namespace OpenRA
 					if (r * r >= (new int2(i, j) - a).LengthSquared)
 						yield return new int2(i, j);
 		}
-
-		public static IEnumerable<Actor> SelectActorsInBox(this World world, float2 a, float2 b)
-		{
-			return world.FindUnits(a, b)
-				.Where( x => x.traits.Contains<Selectable>() && x.IsVisible() )
-				.GroupBy(x => (x.Owner == world.LocalPlayer) ? x.Info.Traits.Get<SelectableInfo>().Priority : 0)
-				.OrderByDescending(g => g.Key)
-				.Select( g => g.AsEnumerable() )
-				.DefaultIfEmpty( new Actor[] {} )
-				.FirstOrDefault();
-		}
 		
 		public static string GetTerrainType(this World world, int2 cell)
 		{