Avoid allocations when generating RadarSignatureCells.

OpenRA.Mods.Common/Traits/Radar/AppearsOnRadar.cs

@@ -30,12 +30,8 @@ public class AppearsOnRadarInfo : ConditionalTraitInfo
 
 	public class AppearsOnRadar : ConditionalTrait<AppearsOnRadarInfo>, IRadarSignature
 	{
-		static readonly IEnumerable<Pair<CPos, Color>> NoCells = Enumerable.Empty<Pair<CPos, Color>>();
 		IRadarColorModifier modifier;
 
-		Color currentColor = Color.Transparent;
-		Func<Pair<CPos, SubCell>, Pair<CPos, Color>> cellToSignature;
-
 		public AppearsOnRadar(AppearsOnRadarInfo info)
 			: base(info) { }
 
@@ -45,27 +41,24 @@ protected override void Created(Actor self)
 			modifier = self.TraitsImplementing<IRadarColorModifier>().FirstOrDefault();
 		}
 
-		public IEnumerable<Pair<CPos, Color>> RadarSignatureCells(Actor self)
+		public void PopulateRadarSignatureCells(Actor self, List<Pair<CPos, Color>> destinationBuffer)
 		{
 			var viewer = self.World.RenderPlayer ?? self.World.LocalPlayer;
 			if (IsTraitDisabled || (viewer != null && !Info.ValidStances.HasStance(self.Owner.Stances[viewer])))
-				return NoCells;
+				return;
 
 			var color = Game.Settings.Game.UsePlayerStanceColors ? self.Owner.PlayerStanceColor(self) : self.Owner.Color.RGB;
 			if (modifier != null)
 				color = modifier.RadarColorOverride(self, color);
 
 			if (Info.UseLocation)
-				return new[] { Pair.New(self.Location, color) };
-
-			// PERF: Cache cellToSignature delegate to avoid allocations as color does not change often.
-			if (currentColor != color)
 			{
-				currentColor = color;
-				cellToSignature = c => Pair.New(c.First, color);
+				destinationBuffer.Add(Pair.New(self.Location, color));
+				return;
 			}
 
-			return self.OccupiesSpace.OccupiedCells().Select(cellToSignature);
+			foreach (var cell in self.OccupiesSpace.OccupiedCells())
+				destinationBuffer.Add(Pair.New(cell.First, color));
 		}
 	}
 }

OpenRA.Mods.Common/Traits/World/EditorActorLayer.cs

@@ -266,9 +266,11 @@ public List<MiniYamlNode> Save()
 			return nodes;
 		}
 
-		public IEnumerable<Pair<CPos, Color>> RadarSignatureCells(Actor self)
+		public void PopulateRadarSignatureCells(Actor self, List<Pair<CPos, Color>> destinationBuffer)
 		{
-			return cellMap.SelectMany(c => c.Value.Select(p => Pair.New(c.Key, p.Owner.Color.RGB)));
+			foreach (var previewsForCell in cellMap)
+				foreach (var preview in previewsForCell.Value)
+					destinationBuffer.Add(Pair.New(previewsForCell.Key, preview.Owner.Color.RGB));
 		}
 	}
 }

OpenRA.Mods.Common/TraitsInterfaces.cs

@@ -354,7 +354,7 @@ public interface IMove
 
 	public interface IRadarSignature
 	{
-		IEnumerable<Pair<CPos, Color>> RadarSignatureCells(Actor self);
+		void PopulateRadarSignatureCells(Actor self, List<Pair<CPos, Color>> destinationBuffer);
 	}
 
 	public interface IRadarColorModifier { Color RadarColorOverride(Actor self, Color color); }

OpenRA.Mods.Common/Widgets/RadarWidget.cs

@@ -15,6 +15,7 @@
 using System.Linq;
 using OpenRA.Graphics;
 using OpenRA.Mods.Common.Traits;
+using OpenRA.Primitives;
 using OpenRA.Traits;
 using OpenRA.Widgets;
 
@@ -361,6 +362,8 @@ public override void Tick()
 				var stride = radarSheet.Size.Width;
 				Array.Clear(radarData, 4 * actorSprite.Bounds.Top * stride, 4 * actorSprite.Bounds.Height * stride);
 
+				var cells = new List<Pair<CPos, Color>>();
+
 				unsafe
 				{
 					fixed (byte* colorBytes = &radarData[0])
@@ -372,7 +375,9 @@ public override void Tick()
 							if (!t.Actor.IsInWorld || world.FogObscures(t.Actor))
 								continue;
 
-							foreach (var cell in t.Trait.RadarSignatureCells(t.Actor))
+							cells.Clear();
+							t.Trait.PopulateRadarSignatureCells(t.Actor, cells);
+							foreach (var cell in cells)
 							{
 								if (!world.Map.Contains(cell.First))
 									continue;