When a render method has nothing to render, eagerly return.

By eagerly returning an empty enumerable in these cases, this avoids allocating an enumerable for the whole render method if nothing will be drawn.

OpenRA.Mods.Common/Traits/CombatDebugOverlay.cs

@@ -55,13 +55,18 @@ namespace OpenRA.Mods.Common.Traits
 		IEnumerable<IRenderable> IRenderAnnotations.RenderAnnotations(Actor self, WorldRenderer wr)
 		{
 			if (debugVis == null || !debugVis.CombatGeometry || self.World.FogObscures(self))
-				yield break;
+				return Enumerable.Empty<IRenderable>();
 
+			return RenderAnnotations(self, wr);
+		}
+
+		IEnumerable<IRenderable> RenderAnnotations(Actor self, WorldRenderer wr)
+		{
 			var blockers = allBlockers.Where(Exts.IsTraitEnabled).ToList();
 			if (blockers.Count > 0)
 			{
 				var height = new WVec(0, 0, blockers.Max(b => b.BlockingHeight.Length));
-				yield return new LineAnnotationRenderable(self.CenterPosition, self.CenterPosition + height, 1,  Color.Orange);
+				yield return new LineAnnotationRenderable(self.CenterPosition, self.CenterPosition + height, 1, Color.Orange);
 			}
 
 			var activeShapes = shapes.Where(Exts.IsTraitEnabled);

OpenRA.Mods.Common/Traits/HitShape.cs

@@ -90,8 +90,13 @@ namespace OpenRA.Mods.Common.Traits
 		IEnumerable<WPos> ITargetablePositions.TargetablePositions(Actor self)
 		{
 			if (IsTraitDisabled)
-				yield break;
+				return Enumerable.Empty<WPos>();
 
+			return TargetablePositions(self);
+		}
+
+		IEnumerable<WPos> TargetablePositions(Actor self)
+		{
 			if (Info.UseTargetableCellsOffsets && targetableCells != null)
 				foreach (var c in targetableCells.TargetableCells())
 					yield return self.World.Map.CenterOfCell(c.Cell);

OpenRA.Mods.Common/Traits/Render/DrawLineToTarget.cs

@@ -63,17 +63,27 @@ namespace OpenRA.Mods.Common.Traits
 			ShowTargetLines(self);
 		}
 
-		IEnumerable<IRenderable> IRenderAboveShroud.RenderAboveShroud(Actor self, WorldRenderer wr)
+		bool ShouldRender(Actor self)
 		{
 			if (!self.Owner.IsAlliedWith(self.World.LocalPlayer) || Game.Settings.Game.TargetLines == TargetLinesType.Disabled)
-				yield break;
+				return false;
 
 			// Players want to see the lines when in waypoint mode.
 			var force = Game.GetModifierKeys().HasModifier(Modifiers.Shift) || self.World.OrderGenerator is ForceModifiersOrderGenerator;
 
-			if (Game.RunTime > lifetime && !force)
+			return force || Game.RunTime <= lifetime;
-				yield break;
+		}
 
+		IEnumerable<IRenderable> IRenderAboveShroud.RenderAboveShroud(Actor self, WorldRenderer wr)
+		{
+			if (!ShouldRender(self))
+				return Enumerable.Empty<IRenderable>();
+
+			return RenderAboveShroud(self, wr);
+		}
+
+		IEnumerable<IRenderable> RenderAboveShroud(Actor self, WorldRenderer wr)
+		{
 			var pal = wr.Palette(TileSet.TerrainPaletteInternalName);
 			var a = self.CurrentActivity;
 			for (; a != null; a = a.NextActivity)
@@ -87,13 +97,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		IEnumerable<IRenderable> IRenderAnnotationsWhenSelected.RenderAnnotations(Actor self, WorldRenderer wr)
 		{
-			if (!self.Owner.IsAlliedWith(self.World.LocalPlayer) || Game.Settings.Game.TargetLines == TargetLinesType.Disabled)
+			if (!ShouldRender(self))
-				return Enumerable.Empty<IRenderable>();
-
-			// Players want to see the lines when in waypoint mode.
-			var force = Game.GetModifierKeys().HasModifier(Modifiers.Shift) || self.World.OrderGenerator is ForceModifiersOrderGenerator;
-
-			if (Game.RunTime > lifetime && !force)
 				return Enumerable.Empty<IRenderable>();
 
 			renderableCache.Clear();
@@ -108,8 +112,8 @@ namespace OpenRA.Mods.Common.Traits
 				{
 					if (n.Target.Type != TargetType.Invalid && n.Tile == null)
 					{
-						var lineWidth = renderableCache.Any() ? info.QueuedLineWidth : info.LineWidth;
+						var lineWidth = renderableCache.Count > 0 ? info.QueuedLineWidth : info.LineWidth;
-						var markerWidth = renderableCache.Any() ? info.QueuedMarkerWidth : info.MarkerWidth;
+						var markerWidth = renderableCache.Count > 0 ? info.QueuedMarkerWidth : info.MarkerWidth;
 
 						var pos = n.Target.CenterPosition;
 						renderableCache.Add(new TargetLineRenderable(new[] { prev, pos }, n.Color, lineWidth, markerWidth));
@@ -118,9 +122,12 @@ namespace OpenRA.Mods.Common.Traits
 				}
 			}
 
+			if (renderableCache.Count == 0)
+				return Enumerable.Empty<IRenderable>();
+
 			// Reverse draw order so target markers are drawn on top of the next line
 			renderableCache.Reverse();
-			return renderableCache;
+			return renderableCache.ToArray();
 		}
 
 		bool IRenderAnnotationsWhenSelected.SpatiallyPartitionable { get { return false; } }