Split Locomotor trait from Mobile

Add GrantConditionOn*Layer traits

This allows to
- drop some booleans from Locomotor
- drop a good part of the subterranean- and jumpjet-specific code/hacks from Mobile
- grant more than 1 condition per layer type (via multiple traits)
- easily add more traits of this kind for other layers

OpenRA.Mods.Common/Traits/Conditions/GrantConditionOnLayer.cs

@@ -0,0 +1,73 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2018 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Linq;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits
+{
+	public abstract class GrantConditionOnLayerInfo : ConditionalTraitInfo
+	{
+		[FieldLoader.Require]
+		[GrantedConditionReference]
+		[Desc("The condition to grant to self when changing to specific custom layer.")]
+		public readonly string Condition = null;
+	}
+
+	public abstract class GrantConditionOnLayer<InfoType> : ConditionalTrait<InfoType>, INotifyCustomLayerChanged where InfoType : GrantConditionOnLayerInfo
+	{
+		protected readonly byte ValidLayerType;
+		protected ConditionManager conditionManager;
+		protected int conditionToken = ConditionManager.InvalidConditionToken;
+
+		public GrantConditionOnLayer(Actor self, InfoType info, byte validLayer)
+			: base(info)
+		{
+			ValidLayerType = validLayer;
+		}
+
+		protected override void Created(Actor self)
+		{
+			conditionManager = self.TraitOrDefault<ConditionManager>();
+			base.Created(self);
+		}
+
+		void INotifyCustomLayerChanged.CustomLayerChanged(Actor self, byte oldLayer, byte newLayer)
+		{
+			if (conditionManager == null)
+				return;
+
+			UpdateConditions(self, oldLayer, newLayer);
+		}
+
+		protected virtual void UpdateConditions(Actor self, byte oldLayer, byte newLayer)
+		{
+			if (newLayer == ValidLayerType && oldLayer != ValidLayerType && conditionToken == ConditionManager.InvalidConditionToken)
+				conditionToken = conditionManager.GrantCondition(self, Info.Condition);
+			else if (newLayer != ValidLayerType && oldLayer == ValidLayerType && conditionToken != ConditionManager.InvalidConditionToken)
+				conditionToken = conditionManager.RevokeCondition(self, conditionToken);
+		}
+
+		protected override void TraitEnabled(Actor self)
+		{
+			if (self.Location.Layer == ValidLayerType && conditionToken == ConditionManager.InvalidConditionToken)
+				conditionToken = conditionManager.GrantCondition(self, Info.Condition);
+		}
+
+		protected override void TraitDisabled(Actor self)
+		{
+			if (conditionToken == ConditionManager.InvalidConditionToken)
+				return;
+
+			conditionToken = conditionManager.RevokeCondition(self, conditionToken);
+		}
+	}
+}