Add "Spawn Child Actor" checkbox in the map editor actor properties.

OpenRA.Mods.Common/Traits/Buildings/FreeActor.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System.Collections.Generic;
 using OpenRA.Primitives;
 using OpenRA.Traits;
 
@@ -16,7 +17,7 @@ namespace OpenRA.Mods.Common.Traits
 {
 	[Desc("Player receives a unit for free once the building is placed. This also works for structures.",
 		"If you want more than one unit to appear copy this section and assign IDs like FreeActor@2, ...")]
-	public class FreeActorInfo : ConditionalTraitInfo
+	public class FreeActorInfo : ConditionalTraitInfo, IEditorActorOptions
 	{
 		[ActorReference]
 		[FieldLoader.Require]
@@ -32,6 +33,26 @@ namespace OpenRA.Mods.Common.Traits
 		[Desc("Whether another actor should spawn upon re-enabling the trait.")]
 		public readonly bool AllowRespawn = false;
 
+		[Desc("Display order for the free actor checkbox in the map editor")]
+		public readonly int EditorFreeActorDisplayOrder = 4;
+
+		IEnumerable<EditorActorOption> IEditorActorOptions.ActorOptions(ActorInfo ai, World world)
+		{
+			yield return new EditorActorCheckbox("Spawn Child Actor", EditorFreeActorDisplayOrder,
+				actor =>
+				{
+					var init = actor.Init<FreeActorInit>();
+					if (init != null)
+						return init.Value(world);
+
+					return true;
+				},
+				(actor, value) =>
+				{
+					actor.ReplaceInit(new FreeActorInit(value));
+				});
+		}
+
 		public override object Create(ActorInitializer init) { return new FreeActor(init, this); }
 	}