Introduce ExplosionOnDamageTransition

And use it for TS cyborgs.

OpenRA.Mods.Common/OpenRA.Mods.Common.csproj

@@ -332,6 +332,7 @@
     <Compile Include="Traits\EmitInfantryOnSell.cs" />
     <Compile Include="Traits\EngineerRepair.cs" />
     <Compile Include="Traits\Explodes.cs" />
+    <Compile Include="Traits\ExplosionOnDamageTransition.cs" />
     <Compile Include="Traits\ExternalCapturable.cs" />
     <Compile Include="Traits\ExternalCapturableBar.cs" />
     <Compile Include="Traits\ExternalCaptures.cs" />

OpenRA.Mods.Common/Traits/ExplosionOnDamageTransition.cs

@@ -0,0 +1,70 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2016 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.Collections.Generic;
+using System.Linq;
+using OpenRA.GameRules;
+using OpenRA.Mods.Common.Warheads;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits
+{
+	[Desc("This actor triggers an explosion on itself when transitioning to a specific damage state.")]
+	public class ExplosionOnDamageTransitionInfo : ITraitInfo, IRulesetLoaded, Requires<HealthInfo>
+	{
+		[WeaponReference, FieldLoader.Require, Desc("Weapon to use for explosion.")]
+		public readonly string Weapon = null;
+
+		[Desc("At which damage state explosion will trigger.")]
+		public readonly DamageState DamageState = DamageState.Heavy;
+
+		[Desc("Should the explosion only be triggered once?")]
+		public readonly bool TriggerOnlyOnce = false;
+
+		public WeaponInfo WeaponInfo { get; private set; }
+
+		public object Create(ActorInitializer init) { return new ExplosionOnDamageTransition(this, init.Self); }
+
+		public void RulesetLoaded(Ruleset rules, ActorInfo ai)
+		{
+			WeaponInfo = string.IsNullOrEmpty(Weapon) ? null : rules.Weapons[Weapon.ToLowerInvariant()];
+		}
+	}
+
+	public class ExplosionOnDamageTransition : INotifyDamageStateChanged
+	{
+		readonly ExplosionOnDamageTransitionInfo info;
+		bool triggered;
+
+		public ExplosionOnDamageTransition(ExplosionOnDamageTransitionInfo info, Actor self)
+		{
+			this.info = info;
+		}
+
+		public void DamageStateChanged(Actor self, AttackInfo e)
+		{
+			if (!self.IsInWorld)
+				return;
+
+			if (triggered)
+				return;
+
+			if (e.DamageState >= info.DamageState && e.PreviousDamageState < info.DamageState)
+			{
+				if (info.TriggerOnlyOnce)
+					triggered = true;
+
+				// Use .FromPos since the actor might have been killed, don't use Target.FromActor
+				info.WeaponInfo.Impact(Target.FromPos(self.CenterPosition), e.Attacker, Enumerable.Empty<int>());
+			}
+		}
+	}
+}

mods/ts/rules/defaults.yaml

@@ -365,6 +365,10 @@
 ^Cyborg:
 	Inherits@1: ^Infantry
 	Inherits@2: ^EmpDisableMobile
+	ExplosionOnDamageTransition:
+		Weapon: CyborgExplode
+		DamageState: Critical
+		TriggerOnlyOnce: true
 	Explodes:
 		Weapon: CyborgExplode
 		EmptyWeapon: CyborgExplode