Work around harvester unloading activity queue issues.

To make sure it kills veteran Tanya as well as Drop Zone shok troopers.

OpenRA.Game/Actor.cs

@@ -336,6 +336,8 @@ namespace OpenRA
 			foreach (var t in TraitsImplementing<INotifyOwnerChanged>())
 				t.OnOwnerChanged(this, oldOwner, newOwner);
 
+			World.Selection.OnOwnerChanged(this, oldOwner, newOwner);
+
 			if (wasInWorld)
 				World.Add(this);
 		}

OpenRA.Game/GameRules/MusicInfo.cs

@@ -19,6 +19,7 @@ namespace OpenRA.GameRules
 		public readonly string Filename;
 		public readonly string Title;
 		public readonly bool Hidden;
+		public readonly float VolumeModifier = 1f;
 
 		public int Length { get; private set; } // seconds
 		public bool Exists { get; private set; }
@@ -31,6 +32,9 @@ namespace OpenRA.GameRules
 			if (nd.ContainsKey("Hidden"))
 				bool.TryParse(nd["Hidden"].Value, out Hidden);
 
+			if (nd.ContainsKey("VolumeModifier"))
+				VolumeModifier = FieldLoader.GetValue<float>("VolumeModifier", nd["VolumeModifier"].Value);
+
 			var ext = nd.ContainsKey("Extension") ? nd["Extension"].Value : "aud";
 			Filename = (nd.ContainsKey("Filename") ? nd["Filename"].Value : key) + "." + ext;
 		}

OpenRA.Game/GameRules/SoundInfo.cs

@@ -33,7 +33,7 @@ namespace OpenRA.GameRules
 		{
 			FieldLoader.Load(this, y);
 
-			VoicePools = Exts.Lazy(() => Voices.ToDictionary(a => a.Key, a => new SoundPool(0, a.Value)));
+			VoicePools = Exts.Lazy(() => Voices.ToDictionary(a => a.Key, a => new SoundPool(1f, a.Value)));
 			NotificationsPools = Exts.Lazy(() => ParseSoundPool(y, "Notifications"));
 		}
 
@@ -43,13 +43,13 @@ namespace OpenRA.GameRules
 			var classifiction = y.Nodes.First(x => x.Key == key);
 			foreach (var t in classifiction.Value.Nodes)
 			{
-				var rateLimit = 0;
-				var rateLimitNode = t.Value.Nodes.FirstOrDefault(x => x.Key == "RateLimit");
-				if (rateLimitNode != null)
-					rateLimit = FieldLoader.GetValue<int>(rateLimitNode.Key, rateLimitNode.Value.Value);
+				var volumeModifier = 1f;
+				var volumeModifierNode = t.Value.Nodes.FirstOrDefault(x => x.Key == "VolumeModifier");
+				if (volumeModifierNode != null)
+					volumeModifier = FieldLoader.GetValue<float>(volumeModifierNode.Key, volumeModifierNode.Value.Value);
 
 				var names = FieldLoader.GetValue<string[]>(t.Key, t.Value.Value);
-				var sp = new SoundPool(rateLimit, names);
+				var sp = new SoundPool(volumeModifier, names);
 				ret.Add(t.Key, sp);
 			}
 
@@ -59,15 +59,14 @@ namespace OpenRA.GameRules
 
 	public class SoundPool
 	{
+		public readonly float VolumeModifier;
 		readonly string[] clips;
-		readonly int rateLimit;
 		readonly List<string> liveclips = new List<string>();
-		long lastPlayed = 0;
 
-		public SoundPool(int rateLimit, params string[] clips)
+		public SoundPool(float volumeModifier, params string[] clips)
 		{
+			VolumeModifier = volumeModifier;
 			this.clips = clips;
-			this.rateLimit = rateLimit;
 		}
 
 		public string GetNext()
@@ -79,16 +78,6 @@ namespace OpenRA.GameRules
 			if (liveclips.Count == 0)
 				return null;
 
-			// Perform rate limiting if necessary
-			if (rateLimit != 0)
-			{
-				var now = Game.RunTime;
-				if (lastPlayed != 0 && now < lastPlayed + rateLimit)
-					return null;
-
-				lastPlayed = now;
-			}
-
 			var i = Game.CosmeticRandom.Next(liveclips.Count);
 			var s = liveclips[i];
 			liveclips.RemoveAt(i);

OpenRA.Game/Selection.cs

@@ -21,7 +21,14 @@ namespace OpenRA
 	{
 		public int Hash { get; private set; }
 		public IEnumerable<Actor> Actors { get { return actors; } }
+
 		readonly HashSet<Actor> actors = new HashSet<Actor>();
+		readonly INotifySelection[] worldNotifySelection;
+
+		internal Selection(IEnumerable<INotifySelection> worldNotifySelection)
+		{
+			this.worldNotifySelection = worldNotifySelection.ToArray();
+		}
 
 		void UpdateHash()
 		{
@@ -31,17 +38,41 @@ namespace OpenRA
 			Hash += 1;
 		}
 
-		public void Add(World w, Actor a)
+		public void Add(Actor a)
 		{
 			actors.Add(a);
 			UpdateHash();
 
 			foreach (var sel in a.TraitsImplementing<INotifySelected>())
 				sel.Selected(a);
-			foreach (var ns in w.WorldActor.TraitsImplementing<INotifySelection>())
+
+			foreach (var ns in worldNotifySelection)
 				ns.SelectionChanged();
 		}
 
+		public void Remove(Actor a)
+		{
+			if (actors.Remove(a))
+			{
+				UpdateHash();
+				foreach (var ns in worldNotifySelection)
+					ns.SelectionChanged();
+			}
+		}
+
+		internal void OnOwnerChanged(Actor a, Player oldOwner, Player newOwner)
+		{
+			if (!actors.Contains(a))
+				return;
+
+			// Remove the actor from the original owners selection
+			// Call UpdateHash directly for everyone else so watchers can account for the owner change if needed
+			if (oldOwner == a.World.LocalPlayer)
+				Remove(a);
+			else
+				UpdateHash();
+		}
+
 		public bool Contains(Actor a)
 		{
 			return actors.Contains(a);
@@ -77,7 +108,7 @@ namespace OpenRA
 				foreach (var sel in a.TraitsImplementing<INotifySelected>())
 					sel.Selected(a);
 
-			foreach (var ns in world.WorldActor.TraitsImplementing<INotifySelection>())
+			foreach (var ns in worldNotifySelection)
 				ns.SelectionChanged();
 
 			if (world.IsGameOver)

OpenRA.Game/Sound/Sound.cs

@@ -214,7 +214,7 @@ namespace OpenRA
 
 			Func<ISoundFormat, ISound> stream = soundFormat => soundEngine.Play2DStream(
 				soundFormat.GetPCMInputStream(), soundFormat.Channels, soundFormat.SampleBits, soundFormat.SampleRate,
-				false, true, WPos.Zero, MusicVolume);
+				false, true, WPos.Zero, MusicVolume * m.VolumeModifier);
 			music = LoadSound(m.Filename, stream);
 
 			if (music == null)
@@ -352,7 +352,7 @@ namespace OpenRA
 
 			var id = voicedActor != null ? voicedActor.ActorID : 0;
 
-			string clip;
+			SoundPool pool;
 			var suffix = rules.DefaultVariant;
 			var prefix = rules.DefaultPrefix;
 
@@ -361,16 +361,17 @@ namespace OpenRA
 				if (!rules.VoicePools.Value.ContainsKey(definition))
 					throw new InvalidOperationException("Can't find {0} in voice pool.".F(definition));
 
-				clip = rules.VoicePools.Value[definition].GetNext();
+				pool = rules.VoicePools.Value[definition];
 			}
 			else
 			{
 				if (!rules.NotificationsPools.Value.ContainsKey(definition))
 					throw new InvalidOperationException("Can't find {0} in notification pool.".F(definition));
 
-				clip = rules.NotificationsPools.Value[definition].GetNext();
+				pool = rules.NotificationsPools.Value[definition];
 			}
 
+			var clip = pool.GetNext();
 			if (string.IsNullOrEmpty(clip))
 				return false;
 
@@ -388,7 +389,7 @@ namespace OpenRA
 			{
 				var sound = soundEngine.Play2D(sounds[name],
 					false, relative, pos,
-					InternalSoundVolume * volumeModifier, attenuateVolume);
+					InternalSoundVolume * volumeModifier * pool.VolumeModifier, attenuateVolume);
 				if (id != 0)
 				{
 					if (currentSounds.ContainsKey(id))

OpenRA.Game/Traits/Player/FrozenActorLayer.cs

@@ -18,6 +18,11 @@ using OpenRA.Primitives;
 
 namespace OpenRA.Traits
 {
+	public interface ICreatesFrozenActors
+	{
+		void OnVisibilityChanged(FrozenActor frozen);
+	}
+
 	[Desc("Required for FrozenUnderFog to work. Attach this to the player actor.")]
 	public class FrozenActorLayerInfo : Requires<ShroudInfo>, ITraitInfo
 	{
@@ -32,11 +37,13 @@ namespace OpenRA.Traits
 		public readonly PPos[] Footprint;
 		public readonly WPos CenterPosition;
 		readonly Actor actor;
+		readonly ICreatesFrozenActors frozenTrait;
 		readonly Player viewer;
 		readonly Shroud shroud;
 
 		public Player Owner { get; private set; }
 		public BitSet<TargetableType> TargetTypes { get; private set; }
+		public WPos[] TargetablePositions { get; private set; }
 
 		public ITooltipInfo TooltipInfo { get; private set; }
 		public Player TooltipOwner { get; private set; }
@@ -70,9 +77,10 @@ namespace OpenRA.Traits
 
 		int flashTicks;
 
-		public FrozenActor(Actor actor, PPos[] footprint, Player viewer, bool startsRevealed)
+		public FrozenActor(Actor actor, ICreatesFrozenActors frozenTrait, PPos[] footprint, Player viewer, bool startsRevealed)
 		{
 			this.actor = actor;
+			this.frozenTrait = frozenTrait;
 			this.viewer = viewer;
 			shroud = viewer.Shroud;
 			NeedRenderables = startsRevealed;
@@ -111,6 +119,7 @@ namespace OpenRA.Traits
 		{
 			Owner = actor.Owner;
 			TargetTypes = actor.GetEnabledTargetTypes();
+			TargetablePositions = actor.GetTargetablePositions().ToArray();
 			Hidden = !actor.CanBeViewedByPlayer(viewer);
 
 			if (health != null)
@@ -153,6 +162,11 @@ namespace OpenRA.Traits
 					Shrouded = false;
 			}
 
+			// Force the backing trait to update so other actors can't
+			// query inconsistent state (both hidden or both visible)
+			if (Visible != wasVisible)
+				frozenTrait.OnVisibilityChanged(this);
+
 			NeedRenderables |= Visible && !wasVisible;
 		}
 

OpenRA.Game/Traits/Target.cs

@@ -19,42 +19,74 @@ namespace OpenRA.Traits
 	public struct Target
 	{
 		public static readonly Target[] None = { };
-		public static readonly Target Invalid = new Target { type = TargetType.Invalid };
+		public static readonly Target Invalid = new Target();
 
-		TargetType type;
-		Actor actor;
-		FrozenActor frozen;
-		WPos pos;
-		CPos? cell;
-		SubCell? subCell;
-		int generation;
+		readonly TargetType type;
+		readonly Actor actor;
+		readonly FrozenActor frozen;
+		readonly WPos terrainCenterPosition;
+		readonly WPos[] terrainPositions;
+		readonly CPos? cell;
+		readonly SubCell? subCell;
+		readonly int generation;
 
-		public static Target FromPos(WPos p) { return new Target { pos = p, type = TargetType.Terrain }; }
-		public static Target FromCell(World w, CPos c, SubCell subCell = SubCell.FullCell)
+		Target(WPos terrainCenterPosition, WPos[] terrainPositions = null)
 		{
-			return new Target
-			{
-				pos = w.Map.CenterOfSubCell(c, subCell),
-				cell = c,
-				subCell = subCell,
-				type = TargetType.Terrain
-			};
+			type = TargetType.Terrain;
+			this.terrainCenterPosition = terrainCenterPosition;
+			this.terrainPositions = terrainPositions ?? new[] { terrainCenterPosition };
+
+			actor = null;
+			frozen = null;
+			cell = null;
+			subCell = null;
+			generation = 0;
 		}
 
-		public static Target FromActor(Actor a)
+		Target(World w, CPos c, SubCell subCell)
 		{
-			if (a == null)
-				return Invalid;
+			type = TargetType.Terrain;
+			terrainCenterPosition = w.Map.CenterOfSubCell(c, subCell);
+			terrainPositions = new[] { terrainCenterPosition };
+			cell = c;
+			this.subCell = subCell;
 
-			return new Target
-			{
-				actor = a,
-				type = TargetType.Actor,
-				generation = a.Generation,
-			};
+			actor = null;
+			frozen = null;
+			generation = 0;
 		}
 
-		public static Target FromFrozenActor(FrozenActor a) { return new Target { frozen = a, type = TargetType.FrozenActor }; }
+		Target(Actor a)
+		{
+			type = TargetType.Actor;
+			actor = a;
+			generation = a.Generation;
+
+			terrainCenterPosition = WPos.Zero;
+			terrainPositions = null;
+			frozen = null;
+			cell = null;
+			subCell = null;
+		}
+
+		Target(FrozenActor fa)
+		{
+			type = TargetType.FrozenActor;
+			frozen = fa;
+
+			terrainCenterPosition = WPos.Zero;
+			terrainPositions = null;
+			actor = null;
+			cell = null;
+			subCell = null;
+			generation = 0;
+		}
+
+		public static Target FromPos(WPos p) { return new Target(p); }
+		public static Target FromTargetPositions(Target t) { return new Target(t.CenterPosition, t.Positions.ToArray()); }
+		public static Target FromCell(World w, CPos c, SubCell subCell = SubCell.FullCell) { return new Target(w, c, subCell); }
+		public static Target FromActor(Actor a) { return a != null ? new Target(a) : Invalid; }
+		public static Target FromFrozenActor(FrozenActor fa) { return new Target(fa); }
 
 		public Actor Actor { get { return actor; } }
 		public FrozenActor FrozenActor { get { return frozen; } }
@@ -134,7 +166,7 @@ namespace OpenRA.Traits
 					case TargetType.FrozenActor:
 						return frozen.CenterPosition;
 					case TargetType.Terrain:
-						return pos;
+						return terrainCenterPosition;
 					default:
 					case TargetType.Invalid:
 						throw new InvalidOperationException("Attempting to query the position of an invalid Target");
@@ -151,14 +183,11 @@ namespace OpenRA.Traits
 				switch (Type)
 				{
 					case TargetType.Actor:
-						if (!actor.Targetables.Any(Exts.IsTraitEnabled))
-							return new[] { actor.CenterPosition };
-
 						return actor.GetTargetablePositions();
 					case TargetType.FrozenActor:
-						return new[] { frozen.CenterPosition };
+						return frozen.TargetablePositions;
 					case TargetType.Terrain:
-						return new[] { pos };
+						return terrainPositions;
 					default:
 					case TargetType.Invalid:
 						return NoPositions;
@@ -186,7 +215,7 @@ namespace OpenRA.Traits
 					return frozen.ToString();
 
 				case TargetType.Terrain:
-					return pos.ToString();
+					return terrainCenterPosition.ToString();
 
 				default:
 				case TargetType.Invalid:
@@ -199,6 +228,6 @@ namespace OpenRA.Traits
 		internal Actor SerializableActor { get { return actor; } }
 		internal CPos? SerializableCell { get { return cell; } }
 		internal SubCell? SerializableSubCell { get { return subCell; } }
-		internal WPos SerializablePos { get { return pos; } }
+		internal WPos SerializablePos { get { return terrainCenterPosition; } }
 	}
 }

OpenRA.Game/World.cs

@@ -142,7 +142,7 @@ namespace OpenRA
 			}
 		}
 
-		public readonly Selection Selection = new Selection();
+		public readonly Selection Selection;
 
 		public void CancelInputMode() { OrderGenerator = new UnitOrderGenerator(); }
 
@@ -179,6 +179,8 @@ namespace OpenRA
 			ActorMap = WorldActor.Trait<IActorMap>();
 			ScreenMap = WorldActor.Trait<ScreenMap>();
 
+			Selection = new Selection(WorldActor.TraitsImplementing<INotifySelection>());
+
 			// Add players
 			foreach (var cmp in WorldActor.TraitsImplementing<ICreatePlayers>())
 				cmp.CreatePlayers(this);

OpenRA.Mods.Cnc/Activities/Infiltrate.cs

@@ -9,8 +9,9 @@
  */
 #endregion
 
+using System;
+using System.Drawing;
 using System.Linq;
-using OpenRA.Activities;
 using OpenRA.Mods.Cnc.Traits;
 using OpenRA.Mods.Common.Activities;
 using OpenRA.Mods.Common.Traits;
@@ -20,32 +21,49 @@ namespace OpenRA.Mods.Cnc.Activities
 {
 	class Infiltrate : Enter
 	{
-		readonly Actor target;
 		readonly Infiltrates infiltrates;
 		readonly INotifyInfiltration[] notifiers;
+		Actor enterActor;
 
-		public Infiltrate(Actor self, Actor target, Infiltrates infiltrate)
-			: base(self, target, infiltrate.Info.EnterBehaviour)
+		public Infiltrate(Actor self, Target target, Infiltrates infiltrates)
+			: base(self, target, Color.Red)
 		{
-			this.target = target;
-			infiltrates  = infiltrate;
+			this.infiltrates = infiltrates;
 			notifiers = self.TraitsImplementing<INotifyInfiltration>().ToArray();
 		}
 
-		protected override void OnInside(Actor self)
+		protected override void TickInner(Actor self, Target target, bool targetIsDeadOrHiddenActor)
 		{
-			if (target.IsDead)
-				return;
+			if (infiltrates.IsTraitDisabled)
+				Cancel(self, true);
+		}
 
-			var stance = self.Owner.Stances[target.Owner];
-			if (!infiltrates.Info.ValidStances.HasStance(stance))
+		protected override bool TryStartEnter(Actor self, Actor targetActor)
+		{
+			// Make sure we can still demolish the target before entering
+			// (but not before, because this may stop the actor in the middle of nowhere)
+			if (!infiltrates.CanInfiltrateTarget(self, Target.FromActor(targetActor)))
+			{
+				Cancel(self, true);
+				return false;
+			}
+
+			enterActor = targetActor;
+			return true;
+		}
+
+		protected override void OnEnterComplete(Actor self, Actor targetActor)
+		{
+			// Make sure the target hasn't changed while entering
+			// OnEnterComplete is only called if targetActor is alive
+			if (targetActor != enterActor || !infiltrates.CanInfiltrateTarget(self, Target.FromActor(targetActor)))
 				return;
 
 			foreach (var ini in notifiers)
 				ini.Infiltrating(self);
 
-			foreach (var t in target.TraitsImplementing<INotifyInfiltrated>())
-				t.Infiltrated(target, self, infiltrates.Info.Types);
+			foreach (var t in targetActor.TraitsImplementing<INotifyInfiltrated>())
+				t.Infiltrated(targetActor, self, infiltrates.Info.Types);
 
 			var exp = self.Owner.PlayerActor.TraitOrDefault<PlayerExperience>();
 			if (exp != null)
@@ -54,14 +72,11 @@ namespace OpenRA.Mods.Cnc.Activities
 			if (!string.IsNullOrEmpty(infiltrates.Info.Notification))
 				Game.Sound.PlayNotification(self.World.Map.Rules, self.Owner, "Speech",
 					infiltrates.Info.Notification, self.Owner.Faction.InternalName);
-		}
 
-		public override Activity Tick(Actor self)
-		{
-			if (infiltrates.IsTraitDisabled)
-				Cancel(self);
-
-			return base.Tick(self);
+			if (infiltrates.Info.EnterBehaviour == EnterBehaviour.Dispose)
+				self.Dispose();
+			else if (infiltrates.Info.EnterBehaviour == EnterBehaviour.Suicide)
+				self.Kill(self);
 		}
 	}
 }

OpenRA.Mods.Cnc/Activities/LeapAttack.cs

@@ -10,9 +10,11 @@
 #endregion
 
 using System;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Cnc.Traits;
+using OpenRA.Mods.Common;
 using OpenRA.Mods.Common.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
@@ -21,13 +23,17 @@ namespace OpenRA.Mods.Cnc.Activities
 {
 	public class LeapAttack : Activity
 	{
-		readonly Target target;
 		readonly AttackLeapInfo info;
 		readonly AttackLeap attack;
-		readonly Mobile mobile, targetMobile;
-		readonly EdibleByLeap edible;
+		readonly Mobile mobile;
 		readonly bool allowMovement;
-		readonly IFacing facing;
+
+		Target target;
+		Target lastVisibleTarget;
+		bool useLastVisibleTarget;
+		WDist lastVisibleMinRange;
+		WDist lastVisibleMaxRange;
+		Activity inner;
 
 		public LeapAttack(Actor self, Target target, bool allowMovement, AttackLeap attack, AttackLeapInfo info)
 		{
@@ -35,61 +41,99 @@ namespace OpenRA.Mods.Cnc.Activities
 			this.info = info;
 			this.attack = attack;
 			this.allowMovement = allowMovement;
-
 			mobile = self.Trait<Mobile>();
-			facing = self.TraitOrDefault<IFacing>();
 
-			if (target.Type == TargetType.Actor)
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
 			{
-				targetMobile = target.Actor.TraitOrDefault<Mobile>();
-				edible = target.Actor.TraitOrDefault<EdibleByLeap>();
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+				lastVisibleMinRange = attack.GetMinimumRangeVersusTarget(target);
+				lastVisibleMaxRange = attack.GetMaximumRangeVersusTarget(target);
 			}
+		}
 
+		protected override void OnFirstRun(Actor self)
+		{
 			attack.IsAiming = true;
 		}
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || edible == null)
-				return NextActivity;
-
 			// Run this even if the target became invalid to avoid visual glitches
-			if (ChildActivity != null)
+			if (inner != null)
 			{
-				ChildActivity = ActivityUtils.RunActivity(self, ChildActivity);
+				inner = ActivityUtils.RunActivity(self, inner);
 				return this;
 			}
 
-			if (target.Type != TargetType.Actor || !edible.CanLeap(self) || !target.IsValidFor(self) || !attack.HasAnyValidWeapons(target))
+			if (IsCanceled)
 				return NextActivity;
 
-			var minRange = attack.GetMinimumRangeVersusTarget(target);
-			var maxRange = attack.GetMaximumRangeVersusTarget(target);
-			if (!target.IsInRange(self.CenterPosition, maxRange) || target.IsInRange(self.CenterPosition, minRange))
+			bool targetIsHiddenActor;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
 			{
-				if (!allowMovement)
+				lastVisibleTarget = Target.FromTargetPositions(target);
+				lastVisibleMinRange = attack.GetMinimumRangeVersusTarget(target);
+				lastVisibleMaxRange = attack.GetMaximumRangeVersusTarget(target);
+			}
+
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, Color.Red, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				return NextActivity;
+
+			var pos = self.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+
+			if (!checkTarget.IsInRange(pos, lastVisibleMaxRange) || checkTarget.IsInRange(pos, lastVisibleMinRange))
+			{
+				if (!allowMovement || lastVisibleMaxRange == WDist.Zero || lastVisibleMaxRange < lastVisibleMinRange)
 					return NextActivity;
 
-				QueueChild(new MoveWithinRange(self, target, minRange, maxRange));
+				inner = mobile.MoveWithinRange(target, lastVisibleMinRange, lastVisibleMaxRange, checkTarget.CenterPosition, Color.Red);
 				return this;
 			}
 
+			// Ready to leap, but target isn't visible
+			if (targetIsHiddenActor || target.Type != TargetType.Actor)
+				return NextActivity;
+
+			// Target is not valid
+			if (!target.IsValidFor(self) || !attack.HasAnyValidWeapons(target))
+				return NextActivity;
+
+			var edible = target.Actor.TraitOrDefault<EdibleByLeap>();
+			if (edible == null || !edible.CanLeap(self))
+				return NextActivity;
+
+			// Can't leap yet
 			if (attack.Armaments.All(a => a.IsReloading))
 				return this;
 
 			// Use CenterOfSubCell with ToSubCell instead of target.Centerposition
 			// to avoid continuous facing adjustments as the target moves
+			var targetMobile = target.Actor.TraitOrDefault<Mobile>();
 			var targetSubcell = targetMobile != null ? targetMobile.ToSubCell : SubCell.Any;
+
 			var destination = self.World.Map.CenterOfSubCell(target.Actor.Location, targetSubcell);
 			var origin = self.World.Map.CenterOfSubCell(self.Location, mobile.FromSubCell);
 			var desiredFacing = (destination - origin).Yaw.Facing;
-			if (facing != null && facing.Facing != desiredFacing)
+			if (mobile.Facing != desiredFacing)
 			{
-				QueueChild(new Turn(self, desiredFacing));
+				inner = new Turn(self, desiredFacing);
 				return this;
 			}
 
-			QueueChild(new Leap(self, target, mobile, targetMobile, info.Speed.Length, attack, edible));
+			inner = new Leap(self, target, mobile, targetMobile, info.Speed.Length, attack, edible);
 
 			// Re-queue the child activities to kill the target if it didn't die in one go
 			return this;
@@ -98,7 +142,14 @@ namespace OpenRA.Mods.Cnc.Activities
 		protected override void OnLastRun(Actor self)
 		{
 			attack.IsAiming = false;
-			base.OnLastRun(self);
+		}
+
+		public override bool Cancel(Actor self, bool keepQueue = false)
+		{
+			if (!IsCanceled && inner != null && !inner.Cancel(self))
+				return false;
+
+			return base.Cancel(self, keepQueue);
 		}
 	}
 }

OpenRA.Mods.Cnc/Scripting/Properties/InfiltrateProperties.cs

@@ -37,7 +37,7 @@ namespace OpenRA.Mods.Cnc.Scripting
 			if (infiltrates == null)
 				throw new LuaException("{0} tried to infiltrate invalid target {1}!".F(Self, target));
 
-			Self.QueueActivity(new Infiltrate(Self, target, infiltrates));
+			Self.QueueActivity(new Infiltrate(Self, Target.FromActor(target), infiltrates));
 		}
 	}
 }

OpenRA.Mods.Cnc/Traits/Attack/AttackTDGunboatTurreted.cs

@@ -59,10 +59,10 @@ namespace OpenRA.Mods.Cnc.Traits
 				{
 					// Check that AttackTDGunboatTurreted hasn't cancelled the target by modifying attack.Target
 					// Having both this and AttackTDGunboatTurreted modify that field is a horrible hack.
-					if (hasTicked && attack.Target.Type == TargetType.Invalid)
+					if (hasTicked && attack.requestedTarget.Type == TargetType.Invalid)
 						return NextActivity;
 
-					attack.Target = target;
+					attack.requestedTarget = target;
 					hasTicked = true;
 				}
 

OpenRA.Mods.Cnc/Traits/ConyardChronoReturn.cs

@@ -193,7 +193,7 @@ namespace OpenRA.Mods.Cnc.Traits
 				nt.AfterTransform(a);
 
 			if (selected)
-				self.World.Selection.Add(self.World, a);
+				self.World.Selection.Add(a);
 
 			if (controlgroup.HasValue)
 				self.World.Selection.AddToControlGroup(a, controlgroup.Value);

OpenRA.Mods.Cnc/Traits/FrozenUnderFogUpdatedByGps.cs

@@ -32,7 +32,11 @@ namespace OpenRA.Mods.Cnc.Traits
 			// This only makes sense if the frozen actor has already been revealed (i.e. has renderables)
 			if (fa.HasRenderables)
 			{
+				// HACK: RefreshState updated *all* actor state, not just the owner
+				// This is generally bogus, and specifically breaks cursors and tooltips by setting Hidden to false
+				var hidden = fa.Hidden;
 				fa.RefreshState();
+				fa.Hidden = hidden;
 				fa.NeedRenderables = true;
 			}
 		};

OpenRA.Mods.Cnc/Traits/GpsDot.cs

@@ -28,7 +28,7 @@ namespace OpenRA.Mods.Cnc.Traits
 		public object Create(ActorInitializer init) { return new GpsDot(this); }
 	}
 
-	class GpsDot : INotifyAddedToWorld, INotifyRemovedFromWorld
+	class GpsDot : INotifyCreated, INotifyAddedToWorld, INotifyRemovedFromWorld
 	{
 		readonly GpsDotInfo info;
 		GpsDotEffect effect;
@@ -38,9 +38,13 @@ namespace OpenRA.Mods.Cnc.Traits
 			this.info = info;
 		}
 
-		void INotifyAddedToWorld.AddedToWorld(Actor self)
+		void INotifyCreated.Created(Actor self)
 		{
 			effect = new GpsDotEffect(self, info);
+		}
+
+		void INotifyAddedToWorld.AddedToWorld(Actor self)
+		{
 			self.World.AddFrameEndTask(w => w.Add(effect));
 		}
 

OpenRA.Mods.Cnc/Traits/Infiltration/Infiltrates.cs

@@ -92,21 +92,34 @@ namespace OpenRA.Mods.Cnc.Traits
 				? Info.Voice : null;
 		}
 
+		public bool CanInfiltrateTarget(Actor self, Target target)
+		{
+			switch (target.Type)
+			{
+				case TargetType.Actor:
+					return Info.Types.Overlaps(target.Actor.GetEnabledTargetTypes()) &&
+					       Info.ValidStances.HasStance(self.Owner.Stances[target.Actor.Owner]);
+				case TargetType.FrozenActor:
+					return target.FrozenActor.IsValid && Info.Types.Overlaps(target.FrozenActor.TargetTypes) &&
+					       Info.ValidStances.HasStance(self.Owner.Stances[target.FrozenActor.Owner]);
+				default:
+					return false;
+			}
+		}
+
 		public void ResolveOrder(Actor self, Order order)
 		{
 			if (order.OrderString != "Infiltrate" || !IsValidOrder(self, order) || IsTraitDisabled)
 				return;
 
-			var target = self.ResolveFrozenActorOrder(order, Color.Red);
-			if (target.Type != TargetType.Actor
-				|| !Info.Types.Overlaps(target.Actor.GetAllTargetTypes()))
+			if (!CanInfiltrateTarget(self, order.Target))
 				return;
 
 			if (!order.Queued)
 				self.CancelActivity();
 
-			self.SetTargetLine(target, Color.Red);
-			self.QueueActivity(new Infiltrate(self, target.Actor, this));
+			self.SetTargetLine(order.Target, Color.Red);
+			self.QueueActivity(new Infiltrate(self, order.Target, this));
 		}
 	}
 

OpenRA.Mods.Cnc/Traits/MadTank.cs

@@ -197,21 +197,18 @@ namespace OpenRA.Mods.Cnc.Traits
 		{
 			if (order.OrderString == "DetonateAttack")
 			{
-				var target = self.ResolveFrozenActorOrder(order, Color.Red);
-				if (target.Type != TargetType.Actor)
-					return;
-
 				if (!order.Queued)
 					self.CancelActivity();
 
-				self.SetTargetLine(target, Color.Red);
-				self.QueueActivity(new MoveAdjacentTo(self, target));
+				self.SetTargetLine(order.Target, Color.Red);
+				self.QueueActivity(new MoveAdjacentTo(self, order.Target, targetLineColor: Color.Red));
 				self.QueueActivity(new CallFunc(StartDetonationSequence));
 			}
 			else if (order.OrderString == "Detonate")
 			{
 				if (!order.Queued)
 					self.CancelActivity();
+
 				self.QueueActivity(new CallFunc(StartDetonationSequence));
 			}
 		}

OpenRA.Mods.Cnc/Traits/TDGunboat.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Common;
@@ -181,11 +182,15 @@ namespace OpenRA.Mods.Cnc.Traits
 
 		public Activity MoveTo(CPos cell, int nearEnough) { return null; }
 		public Activity MoveTo(CPos cell, Actor ignoreActor) { return null; }
-		public Activity MoveWithinRange(Target target, WDist range) { return null; }
-		public Activity MoveWithinRange(Target target, WDist minRange, WDist maxRange) { return null; }
-		public Activity MoveFollow(Actor self, Target target, WDist minRange, WDist maxRange) { return null; }
+		public Activity MoveWithinRange(Target target, WDist range,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null) { return null; }
+		public Activity MoveWithinRange(Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null) { return null; }
+		public Activity MoveFollow(Actor self, Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null) { return null; }
 		public Activity MoveIntoWorld(Actor self, CPos cell, SubCell subCell = SubCell.Any) { return null; }
-		public Activity MoveToTarget(Actor self, Target target) { return null; }
+		public Activity MoveToTarget(Actor self, Target target,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null) { return null; }
 		public Activity MoveIntoTarget(Actor self, Target target) { return null; }
 		public Activity VisualMove(Actor self, WPos fromPos, WPos toPos) { return null; }
 

OpenRA.Mods.Common/AIUtils.cs

@@ -20,23 +20,6 @@ namespace OpenRA.Mods.Common
 
 	public enum WaterCheck { NotChecked, EnoughWater, NotEnoughWater }
 
-	public class CaptureTarget<TInfoType> where TInfoType : class, ITraitInfoInterface
-	{
-		internal readonly Actor Actor;
-		internal readonly TInfoType Info;
-
-		/// <summary>The order string given to the capturer so they can capture this actor.</summary>
-		/// <example>ExternalCaptureActor</example>
-		internal readonly string OrderString;
-
-		internal CaptureTarget(Actor actor, string orderString)
-		{
-			Actor = actor;
-			Info = actor.Info.TraitInfoOrDefault<TInfoType>();
-			OrderString = orderString;
-		}
-	}
-
 	public static class AIUtils
 	{
 		public static bool IsAreaAvailable<T>(World world, Player player, Map map, int radius, HashSet<string> terrainTypes)

OpenRA.Mods.Common/Activities/Air/Fly.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using System.Drawing;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
@@ -19,19 +20,32 @@ namespace OpenRA.Mods.Common.Activities
 	public class Fly : Activity
 	{
 		readonly Aircraft aircraft;
-		readonly Target target;
 		readonly WDist maxRange;
 		readonly WDist minRange;
+		readonly Color? targetLineColor;
+		Target target;
+		Target lastVisibleTarget;
+		bool useLastVisibleTarget;
 		bool soundPlayed;
 
-		public Fly(Actor self, Target t)
+		public Fly(Actor self, Target t, WPos? initialTargetPosition = null, Color? targetLineColor = null)
 		{
 			aircraft = self.Trait<Aircraft>();
 			target = t;
+			this.targetLineColor = targetLineColor;
+
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+			else if (initialTargetPosition.HasValue)
+				lastVisibleTarget = Target.FromPos(initialTargetPosition.Value);
 		}
 
-		public Fly(Actor self, Target t, WDist minRange, WDist maxRange)
-			: this(self, t)
+		public Fly(Actor self, Target t, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
+			: this(self, t, initialTargetPosition, targetLineColor)
 		{
 			this.maxRange = maxRange;
 			this.minRange = minRange;
@@ -61,14 +75,30 @@ namespace OpenRA.Mods.Common.Activities
 		{
 			// Refuse to take off if it would land immediately again.
 			if (aircraft.ForceLanding)
-			{
 				Cancel(self);
-				return NextActivity;
-			}
 
-			if (IsCanceled || !target.IsValidFor(self))
+			if (IsCanceled)
 				return NextActivity;
 
+			bool targetIsHiddenActor;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
+				lastVisibleTarget = Target.FromTargetPositions(target);
+
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget && targetLineColor.HasValue)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, targetLineColor.Value, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				return NextActivity;
+
+			var pos = self.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+
 			if (!soundPlayed && aircraft.Info.TakeoffSounds.Length > 0 && self.IsAtGroundLevel())
 			{
 				Game.Sound.Play(SoundType.World, aircraft.Info.TakeoffSounds.Random(self.World.SharedRandom), aircraft.CenterPosition);
@@ -76,23 +106,43 @@ namespace OpenRA.Mods.Common.Activities
 			}
 
 			// Inside the target annulus, so we're done
-			var insideMaxRange = maxRange.Length > 0 && target.IsInRange(aircraft.CenterPosition, maxRange);
-			var insideMinRange = minRange.Length > 0 && target.IsInRange(aircraft.CenterPosition, minRange);
+			var insideMaxRange = maxRange.Length > 0 && checkTarget.IsInRange(aircraft.CenterPosition, maxRange);
+			var insideMinRange = minRange.Length > 0 && checkTarget.IsInRange(aircraft.CenterPosition, minRange);
 			if (insideMaxRange && !insideMinRange)
 				return NextActivity;
 
-			var d = target.CenterPosition - self.CenterPosition;
+			var delta = checkTarget.CenterPosition - self.CenterPosition;
 
 			// The next move would overshoot, so consider it close enough
 			var move = aircraft.FlyStep(aircraft.Facing);
-			if (d.HorizontalLengthSquared < move.HorizontalLengthSquared)
+			if (delta.HorizontalLengthSquared < move.HorizontalLengthSquared)
 				return NextActivity;
 
 			// Don't turn until we've reached the cruise altitude
-			var desiredFacing = d.Yaw.Facing;
+			var desiredFacing = delta.Yaw.Facing;
 			var targetAltitude = aircraft.CenterPosition.Z + aircraft.Info.CruiseAltitude.Length - self.World.Map.DistanceAboveTerrain(aircraft.CenterPosition).Length;
 			if (aircraft.CenterPosition.Z < targetAltitude)
 				desiredFacing = aircraft.Facing;
+			else
+			{
+				// Using the turn rate, compute a hypothetical circle traced by a continuous turn.
+				// If it contains the destination point, it's unreachable without more complex manuvering.
+				var turnRadius = CalculateTurnRadius(aircraft.MovementSpeed, aircraft.TurnSpeed);
+
+				// The current facing is a tangent of the minimal turn circle.
+				// Make a perpendicular vector, and use it to locate the turn's center.
+				var turnCenterFacing = aircraft.Facing;
+				turnCenterFacing += Util.GetNearestFacing(aircraft.Facing, desiredFacing) > 0 ? 64 : -64;
+
+				var turnCenterDir = new WVec(0, -1024, 0).Rotate(WRot.FromFacing(turnCenterFacing));
+				turnCenterDir *= turnRadius;
+				turnCenterDir /= 1024;
+
+				// Compare with the target point, and keep flying away if it's inside the circle.
+				var turnCenter = aircraft.CenterPosition + turnCenterDir;
+				if ((checkTarget.CenterPosition - turnCenter).HorizontalLengthSquared < turnRadius * turnRadius)
+					desiredFacing = aircraft.Facing;
+			}
 
 			FlyToward(self, aircraft, desiredFacing, aircraft.Info.CruiseAltitude);
 
@@ -103,5 +153,13 @@ namespace OpenRA.Mods.Common.Activities
 		{
 			yield return target;
 		}
+
+		public static int CalculateTurnRadius(int speed, int turnSpeed)
+		{
+			// turnSpeed -> divide into 256 to get the number of ticks per complete rotation
+			// speed -> multiply to get distance travelled per rotation (circumference)
+			// 45 -> divide by 2*pi to get the turn radius: 45==256/(2*pi), with some extra leeway
+			return 45 * speed / turnSpeed;
+		}
 	}
 }

OpenRA.Mods.Common/Activities/Air/FlyAttack.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System.Drawing;
 using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
@@ -22,6 +23,9 @@ namespace OpenRA.Mods.Common.Activities
 		readonly AttackAircraft attackAircraft;
 		readonly Rearmable rearmable;
 		Target target;
+		Target lastVisibleTarget;
+		WDist lastVisibleMaximumRange;
+		bool useLastVisibleTarget;
 
 		int ticksUntilTurn;
 
@@ -32,38 +36,81 @@ namespace OpenRA.Mods.Common.Activities
 			attackAircraft = self.Trait<AttackAircraft>();
 			rearmable = self.TraitOrDefault<Rearmable>();
 			ticksUntilTurn = attackAircraft.AttackAircraftInfo.AttackTurnDelay;
+
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+			{
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+				lastVisibleMaximumRange = attackAircraft.GetMaximumRangeVersusTarget(target);
+			}
 		}
 
 		public override Activity Tick(Actor self)
 		{
 			// Refuse to take off if it would land immediately again.
 			if (aircraft.ForceLanding)
-			{
 				Cancel(self);
+
+			if (IsCanceled)
 				return NextActivity;
+
+			bool targetIsHiddenActor;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
+			{
+				lastVisibleTarget = Target.FromTargetPositions(target);
+				lastVisibleMaximumRange = attackAircraft.GetMaximumRangeVersusTarget(target);
 			}
 
-			target = target.Recalculate(self.Owner);
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
 
-			if (!target.IsValidFor(self))
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, Color.Red, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
 				return NextActivity;
 
 			// If all valid weapons have depleted their ammo and Rearmable trait exists, return to RearmActor to reload and then resume the activity
-			if (rearmable != null && attackAircraft.Armaments.All(x => x.IsTraitPaused || !x.Weapon.IsValidAgainst(target, self.World, self)))
+			if (rearmable != null && !useLastVisibleTarget && attackAircraft.Armaments.All(x => x.IsTraitPaused || !x.Weapon.IsValidAgainst(target, self.World, self)))
 				return ActivityUtils.SequenceActivities(new ReturnToBase(self, aircraft.Info.AbortOnResupply), this);
 
+			var pos = self.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+
+			// We don't know where the target actually is, so move to where we last saw it
+			if (useLastVisibleTarget)
+			{
+				// We've reached the assumed position but it is not there - give up
+				if (checkTarget.IsInRange(pos, lastVisibleMaximumRange))
+					return NextActivity;
+
+				// Fly towards the last known position
+				return ActivityUtils.SequenceActivities(
+					new Fly(self, target, WDist.Zero, lastVisibleMaximumRange, checkTarget.CenterPosition, Color.Red),
+					this);
+			}
+
+			// If we reach here the target is guaranteed to be both visible and alive, so use target instead of checkTarget.
+			// The target may not be in range, but try attacking anyway...
 			attackAircraft.DoAttack(self, target);
 
 			if (ChildActivity == null)
 			{
-				if (IsCanceled)
-					return NextActivity;
-
 				// TODO: This should fire each weapon at its maximum range
-				if (attackAircraft != null && target.IsInRange(self.CenterPosition, attackAircraft.Armaments.Where(Exts.IsTraitEnabled).Select(a => a.Weapon.MinRange).Min()))
-					ChildActivity = ActivityUtils.SequenceActivities(new FlyTimed(ticksUntilTurn, self), new Fly(self, target), new FlyTimed(ticksUntilTurn, self));
+				if (attackAircraft != null && target.IsInRange(self.CenterPosition, attackAircraft.GetMinimumRange()))
+					ChildActivity = ActivityUtils.SequenceActivities(
+						new FlyTimed(ticksUntilTurn, self),
+						new Fly(self, target, checkTarget.CenterPosition, Color.Red),
+						new FlyTimed(ticksUntilTurn, self));
 				else
-					ChildActivity = ActivityUtils.SequenceActivities(new Fly(self, target), new FlyTimed(ticksUntilTurn, self));
+					ChildActivity = ActivityUtils.SequenceActivities(
+						new Fly(self, target, checkTarget.CenterPosition, Color.Red),
+						new FlyTimed(ticksUntilTurn, self));
 
 				// HACK: This needs to be done in this round-about way because TakeOff doesn't behave as expected when it doesn't have a NextActivity.
 				if (self.World.Map.DistanceAboveTerrain(self.CenterPosition).Length < aircraft.Info.MinAirborneAltitude)

OpenRA.Mods.Common/Activities/Air/FlyCircle.cs

@@ -29,6 +29,9 @@ namespace OpenRA.Mods.Common.Activities
 
 		public override Activity Tick(Actor self)
 		{
+			if (NextActivity != null && remainingTicks <= 0)
+				return NextActivity;
+
 			// Refuse to take off if it would land immediately again.
 			if (aircraft.ForceLanding)
 			{
@@ -41,8 +44,6 @@ namespace OpenRA.Mods.Common.Activities
 
 			if (remainingTicks > 0)
 				remainingTicks--;
-			else if (remainingTicks == 0)
-				return NextActivity;
 
 			// We can't possibly turn this fast
 			var desiredFacing = aircraft.Facing + 64;

OpenRA.Mods.Common/Activities/Air/FlyFollow.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System.Drawing;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
@@ -17,38 +18,80 @@ namespace OpenRA.Mods.Common.Activities
 {
 	public class FlyFollow : Activity
 	{
+		readonly Aircraft aircraft;
+		readonly WDist minRange;
+		readonly WDist maxRange;
+		readonly Color? targetLineColor;
 		Target target;
-		Aircraft aircraft;
-		WDist minRange;
-		WDist maxRange;
+		Target lastVisibleTarget;
+		bool useLastVisibleTarget;
+		bool wasMovingWithinRange;
 
-		public FlyFollow(Actor self, Target target, WDist minRange, WDist maxRange)
+		public FlyFollow(Actor self, Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition, Color? targetLineColor = null)
 		{
 			this.target = target;
 			aircraft = self.Trait<Aircraft>();
 			this.minRange = minRange;
 			this.maxRange = maxRange;
+			this.targetLineColor = targetLineColor;
+
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+			else if (initialTargetPosition.HasValue)
+				lastVisibleTarget = Target.FromPos(initialTargetPosition.Value);
 		}
 
 		public override Activity Tick(Actor self)
 		{
 			// Refuse to take off if it would land immediately again.
 			if (aircraft.ForceLanding)
-			{
 				Cancel(self);
-				return NextActivity;
-			}
 
-			if (IsCanceled || !target.IsValidFor(self))
+			if (IsCanceled)
 				return NextActivity;
 
-			if (target.IsInRange(self.CenterPosition, maxRange) && !target.IsInRange(self.CenterPosition, minRange))
+			bool targetIsHiddenActor;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
+				lastVisibleTarget = Target.FromTargetPositions(target);
+
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// If we are ticking again after previously sequencing a MoveWithRange then that move must have completed
+			// Either we are in range and can see the target, or we've lost track of it and should give up
+			if (wasMovingWithinRange && targetIsHiddenActor)
+				return NextActivity;
+
+			wasMovingWithinRange = false;
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget && targetLineColor.HasValue)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, targetLineColor.Value, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				return NextActivity;
+
+			var pos = self.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+
+			// We've reached the required range - if the target is visible and valid then we wait
+			// otherwise if it is hidden or dead we give up
+			if (checkTarget.IsInRange(pos, maxRange) && !checkTarget.IsInRange(pos, minRange))
 			{
 				Fly.FlyToward(self, aircraft, aircraft.Facing, aircraft.Info.CruiseAltitude);
-				return this;
+				return useLastVisibleTarget ? NextActivity : this;
 			}
 
-			return ActivityUtils.SequenceActivities(new Fly(self, target, minRange, maxRange), this);
+			wasMovingWithinRange = true;
+			return ActivityUtils.SequenceActivities(
+				aircraft.MoveWithinRange(target, minRange, maxRange, checkTarget.CenterPosition, targetLineColor),
+				this);
 		}
 	}
 }

OpenRA.Mods.Common/Activities/Air/HeliAttack.cs

@@ -21,72 +21,84 @@ namespace OpenRA.Mods.Common.Activities
 	{
 		readonly Aircraft aircraft;
 		readonly AttackAircraft attackAircraft;
-		readonly bool attackOnlyVisibleTargets;
 		readonly Rearmable rearmable;
 
 		Target target;
-		bool canHideUnderFog;
-		protected Target Target
-		{
-			get
-			{
-				return target;
-			}
+		Target lastVisibleTarget;
+		WDist lastVisibleMaximumRange;
+		bool useLastVisibleTarget;
 
-			private set
-			{
-				target = value;
-				if (target.Type == TargetType.Actor)
-					canHideUnderFog = target.Actor.Info.HasTraitInfo<HiddenUnderFogInfo>();
-			}
-		}
-
-		public HeliAttack(Actor self, Target target, bool attackOnlyVisibleTargets = true)
+		public HeliAttack(Actor self, Target target)
 		{
-			Target = target;
+			this.target = target;
 			aircraft = self.Trait<Aircraft>();
 			attackAircraft = self.Trait<AttackAircraft>();
-			this.attackOnlyVisibleTargets = attackOnlyVisibleTargets;
 			rearmable = self.TraitOrDefault<Rearmable>();
+
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+			{
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+				lastVisibleMaximumRange = attackAircraft.GetMaximumRangeVersusTarget(target);
+			}
 		}
 
 		public override Activity Tick(Actor self)
 		{
 			// Refuse to take off if it would land immediately again.
 			if (aircraft.ForceLanding)
-			{
 				Cancel(self);
-				return NextActivity;
-			}
 
-			if (IsCanceled || !target.IsValidFor(self))
+			if (IsCanceled)
 				return NextActivity;
 
-			var pos = self.CenterPosition;
-			var targetPos = attackAircraft.GetTargetPosition(pos, target);
-			if (attackOnlyVisibleTargets && target.Type == TargetType.Actor && canHideUnderFog
-				&& !target.Actor.CanBeViewedByPlayer(self.Owner))
+			bool targetIsHiddenActor;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
 			{
-				var newTarget = Target.FromCell(self.World, self.World.Map.CellContaining(targetPos));
-
-				Cancel(self);
-				self.SetTargetLine(newTarget, Color.Green);
-				return new HeliFly(self, newTarget);
+				lastVisibleTarget = Target.FromTargetPositions(target);
+				lastVisibleMaximumRange = attackAircraft.GetMaximumRangeVersusTarget(target);
 			}
 
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, Color.Red, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				return NextActivity;
+
 			// If all valid weapons have depleted their ammo and Rearmable trait exists, return to RearmActor to reload and then resume the activity
-			if (rearmable != null && attackAircraft.Armaments.All(x => x.IsTraitPaused || !x.Weapon.IsValidAgainst(target, self.World, self)))
+			if (rearmable != null && !useLastVisibleTarget && attackAircraft.Armaments.All(x => x.IsTraitPaused || !x.Weapon.IsValidAgainst(target, self.World, self)))
 				return ActivityUtils.SequenceActivities(new HeliReturnToBase(self, aircraft.Info.AbortOnResupply), this);
 
-			var dist = targetPos - pos;
+			var pos = self.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
 
-			// Can rotate facing while ascending
-			var desiredFacing = dist.HorizontalLengthSquared != 0 ? dist.Yaw.Facing : aircraft.Facing;
+			// Update facing
+			var delta = attackAircraft.GetTargetPosition(pos, checkTarget) - pos;
+			var desiredFacing = delta.HorizontalLengthSquared != 0 ? delta.Yaw.Facing : aircraft.Facing;
 			aircraft.Facing = Util.TickFacing(aircraft.Facing, desiredFacing, aircraft.TurnSpeed);
-
 			if (HeliFly.AdjustAltitude(self, aircraft, aircraft.Info.CruiseAltitude))
 				return this;
 
+			// We don't know where the target actually is, so move to where we last saw it
+			if (useLastVisibleTarget)
+			{
+				// We've reached the assumed position but it is not there - give up
+				if (checkTarget.IsInRange(pos, lastVisibleMaximumRange))
+					return NextActivity;
+
+				// Fly towards the last known position
+				aircraft.SetPosition(self, aircraft.CenterPosition + aircraft.FlyStep(desiredFacing));
+				return this;
+			}
+
 			// Fly towards the target
 			if (!target.IsInRange(pos, attackAircraft.GetMaximumRangeVersusTarget(target)))
 				aircraft.SetPosition(self, aircraft.CenterPosition + aircraft.FlyStep(desiredFacing));

OpenRA.Mods.Common/Activities/Air/HeliFly.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using System.Drawing;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
@@ -19,19 +20,33 @@ namespace OpenRA.Mods.Common.Activities
 	public class HeliFly : Activity
 	{
 		readonly Aircraft aircraft;
-		readonly Target target;
 		readonly WDist maxRange;
 		readonly WDist minRange;
+		readonly Color? targetLineColor;
 		bool soundPlayed;
 
-		public HeliFly(Actor self, Target t)
+		Target target;
+		Target lastVisibleTarget;
+		bool useLastVisibleTarget;
+
+		public HeliFly(Actor self, Target t, WPos? initialTargetPosition = null, Color? targetLineColor = null)
 		{
 			aircraft = self.Trait<Aircraft>();
 			target = t;
+			this.targetLineColor = targetLineColor;
+
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+			else if (initialTargetPosition.HasValue)
+				lastVisibleTarget = Target.FromPos(initialTargetPosition.Value);
 		}
 
-		public HeliFly(Actor self, Target t, WDist minRange, WDist maxRange)
-			: this(self, t)
+		public HeliFly(Actor self, Target t, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
+			: this(self, t, initialTargetPosition, targetLineColor)
 		{
 			this.maxRange = maxRange;
 			this.minRange = minRange;
@@ -56,12 +71,25 @@ namespace OpenRA.Mods.Common.Activities
 		{
 			// Refuse to take off if it would land immediately again.
 			if (aircraft.ForceLanding)
-			{
 				Cancel(self);
-				return NextActivity;
-			}
 
-			if (IsCanceled || !target.IsValidFor(self))
+			if (IsCanceled)
+				return NextActivity;
+
+			bool targetIsHiddenActor;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
+				lastVisibleTarget = Target.FromTargetPositions(target);
+
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget && targetLineColor.HasValue)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, targetLineColor.Value, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
 				return NextActivity;
 
 			if (!soundPlayed && aircraft.Info.TakeoffSounds.Length > 0 && self.IsAtGroundLevel())
@@ -73,30 +101,33 @@ namespace OpenRA.Mods.Common.Activities
 			if (AdjustAltitude(self, aircraft, aircraft.Info.CruiseAltitude))
 				return this;
 
-			var pos = target.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
 
-			// Rotate towards the target
-			var dist = pos - self.CenterPosition;
-			var desiredFacing = dist.HorizontalLengthSquared != 0 ? dist.Yaw.Facing : aircraft.Facing;
+			// Update facing
+			var delta = checkTarget.CenterPosition - aircraft.CenterPosition;
+			var desiredFacing = delta.HorizontalLengthSquared != 0 ? delta.Yaw.Facing : aircraft.Facing;
 			aircraft.Facing = Util.TickFacing(aircraft.Facing, desiredFacing, aircraft.TurnSpeed);
+			if (AdjustAltitude(self, aircraft, aircraft.Info.CruiseAltitude))
+				return this;
+
 			var move = aircraft.FlyStep(desiredFacing);
 
 			// Inside the minimum range, so reverse
-			if (minRange.Length > 0 && target.IsInRange(aircraft.CenterPosition, minRange))
+			if (minRange.Length > 0 && checkTarget.IsInRange(aircraft.CenterPosition, minRange))
 			{
 				aircraft.SetPosition(self, aircraft.CenterPosition - move);
 				return this;
 			}
 
 			// Inside the maximum range, so we're done
-			if (maxRange.Length > 0 && target.IsInRange(aircraft.CenterPosition, maxRange))
+			if (maxRange.Length > 0 && checkTarget.IsInRange(aircraft.CenterPosition, maxRange))
 				return NextActivity;
 
 			// The next move would overshoot, so just set the final position
-			if (dist.HorizontalLengthSquared < move.HorizontalLengthSquared)
+			if (delta.HorizontalLengthSquared < move.HorizontalLengthSquared)
 			{
 				var targetAltitude = aircraft.CenterPosition.Z + aircraft.Info.CruiseAltitude.Length - self.World.Map.DistanceAboveTerrain(aircraft.CenterPosition).Length;
-				aircraft.SetPosition(self, pos + new WVec(0, 0, targetAltitude - pos.Z));
+				aircraft.SetPosition(self, checkTarget.CenterPosition + new WVec(0, 0, targetAltitude - checkTarget.CenterPosition.Z));
 				return NextActivity;
 			}
 

OpenRA.Mods.Common/Activities/Air/HeliReturnToBase.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
@@ -89,7 +90,9 @@ namespace OpenRA.Mods.Common.Activities
 
 						var target = Target.FromPos(nearestResupplier.CenterPosition + randomPosition);
 
-						return ActivityUtils.SequenceActivities(new HeliFly(self, target, WDist.Zero, aircraft.Info.WaitDistanceFromResupplyBase), this);
+						return ActivityUtils.SequenceActivities(
+							new HeliFly(self, target, WDist.Zero, aircraft.Info.WaitDistanceFromResupplyBase, targetLineColor: Color.Green),
+							this);
 					}
 
 					return this;

OpenRA.Mods.Common/Activities/Air/ResupplyAircraft.cs

@@ -38,12 +38,10 @@ namespace OpenRA.Mods.Common.Activities
 			}
 			else
 			{
-				// HACK: Append NextInQueue to TakeOff to avoid moving to the Rallypoint (if NextInQueue is non-null).
 				ChildActivity = ActivityUtils.SequenceActivities(
 					aircraft.GetResupplyActivities(host)
 					.Append(new AllowYieldingReservation(self))
-					.Append(new TakeOff(self))
-					.Append(NextInQueue)
+					.Append(new TakeOff(self, (a, b, c) => NextInQueue == null && b.NextInQueue == null))
 					.ToArray());
 			}
 		}

OpenRA.Mods.Common/Activities/Air/ReturnToBase.cs

@@ -11,6 +11,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
@@ -52,11 +53,6 @@ namespace OpenRA.Mods.Common.Activities
 				.ClosestTo(self);
 		}
 
-		int CalculateTurnRadius(int speed)
-		{
-			return 45 * speed / aircraft.Info.TurnSpeed;
-		}
-
 		void Calculate(Actor self)
 		{
 			if (dest == null || dest.IsDead || Reservable.IsReserved(dest))
@@ -76,7 +72,7 @@ namespace OpenRA.Mods.Common.Activities
 
 			// Add 10% to the turning radius to ensure we have enough room
 			var speed = aircraft.MovementSpeed * 32 / 35;
-			var turnRadius = CalculateTurnRadius(speed);
+			var turnRadius = Fly.CalculateTurnRadius(speed, aircraft.Info.TurnSpeed);
 
 			// Find the center of the turning circles for clockwise and counterclockwise turns
 			var angle = WAngle.FromFacing(aircraft.Facing);
@@ -140,7 +136,7 @@ namespace OpenRA.Mods.Common.Activities
 
 				if (nearestResupplier != null)
 					return ActivityUtils.SequenceActivities(
-						new Fly(self, Target.FromActor(nearestResupplier), WDist.Zero, aircraft.Info.WaitDistanceFromResupplyBase),
+						new Fly(self, Target.FromActor(nearestResupplier), WDist.Zero, aircraft.Info.WaitDistanceFromResupplyBase, targetLineColor: Color.Green),
 						new FlyCircle(self, aircraft.Info.NumberOfTicksToVerifyAvailableAirport),
 						this);
 				else
@@ -153,7 +149,7 @@ namespace OpenRA.Mods.Common.Activities
 
 			List<Activity> landingProcedures = new List<Activity>();
 
-			var turnRadius = CalculateTurnRadius(aircraft.Info.Speed);
+			var turnRadius = Fly.CalculateTurnRadius(aircraft.Info.Speed, aircraft.Info.TurnSpeed);
 
 			landingProcedures.Add(new Fly(self, Target.FromPos(w1), WDist.Zero, new WDist(turnRadius * 3)));
 			landingProcedures.Add(new Fly(self, Target.FromPos(w2)));

OpenRA.Mods.Common/Activities/Air/TakeOff.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 
@@ -18,11 +19,19 @@ namespace OpenRA.Mods.Common.Activities
 	{
 		readonly Aircraft aircraft;
 		readonly IMove move;
+		Func<Actor, Activity, CPos, bool> moveToRallyPoint;
 
 		public TakeOff(Actor self)
 		{
 			aircraft = self.Trait<Aircraft>();
 			move = self.Trait<IMove>();
+			moveToRallyPoint = (actor, activity, pos) => NextActivity == null;
+		}
+
+		public TakeOff(Actor self, Func<Actor, Activity, CPos, bool> moveToRallyPoint)
+			: this(self)
+		{
+			this.moveToRallyPoint = moveToRallyPoint;
 		}
 
 		public override Activity Tick(Actor self)
@@ -43,10 +52,10 @@ namespace OpenRA.Mods.Common.Activities
 			var destination = rp != null ? rp.Location :
 				(hasHost ? self.World.Map.CellContaining(host.CenterPosition) : self.Location);
 
-			if (NextInQueue == null)
+			if (moveToRallyPoint(self, this, destination))
 				return new AttackMoveActivity(self, move.MoveTo(destination, 1));
 			else
-				return NextInQueue;
+				return NextActivity;
 		}
 	}
 }

OpenRA.Mods.Common/Activities/Attack.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
@@ -29,7 +30,12 @@ namespace OpenRA.Mods.Common.Activities
 		readonly IFacing facing;
 		readonly IPositionable positionable;
 		readonly bool forceAttack;
+
 		protected Target target;
+		Target lastVisibleTarget;
+		WDist lastVisibleMaximumRange;
+		bool useLastVisibleTarget;
+		bool wasMovingWithinRange;
 
 		WDist minRange;
 		WDist maxRange;
@@ -48,16 +54,71 @@ namespace OpenRA.Mods.Common.Activities
 			positionable = self.Trait<IPositionable>();
 
 			move = allowMovement ? self.TraitOrDefault<IMove>() : null;
+
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+			{
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+				lastVisibleMaximumRange = attackTraits.Where(x => !x.IsTraitDisabled)
+					.Min(x => x.GetMaximumRangeVersusTarget(target));
+			}
 		}
 
-		protected virtual Target RecalculateTarget(Actor self)
+		protected virtual Target RecalculateTarget(Actor self, out bool targetIsHiddenActor)
 		{
-			return target.Recalculate(self.Owner);
+			return target.Recalculate(self.Owner, out targetIsHiddenActor);
 		}
 
 		public override Activity Tick(Actor self)
 		{
-			target = RecalculateTarget(self);
+			if (IsCanceled)
+				return NextActivity;
+
+			bool targetIsHiddenActor;
+			target = RecalculateTarget(self, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
+			{
+				lastVisibleTarget = Target.FromTargetPositions(target);
+				lastVisibleMaximumRange = attackTraits.Where(x => !x.IsTraitDisabled)
+					.Min(x => x.GetMaximumRangeVersusTarget(target));
+			}
+
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// If we are ticking again after previously sequencing a MoveWithRange then that move must have completed
+			// Either we are in range and can see the target, or we've lost track of it and should give up
+			if (wasMovingWithinRange && targetIsHiddenActor)
+				return NextActivity;
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, Color.Red, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				return NextActivity;
+
+			wasMovingWithinRange = false;
+			var pos = self.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+
+			// We don't know where the target actually is, so move to where we last saw it
+			if (useLastVisibleTarget)
+			{
+				// We've reached the assumed position but it is not there or we can't move any further - give up
+				if (checkTarget.IsInRange(pos, lastVisibleMaximumRange) || move == null || lastVisibleMaximumRange == WDist.Zero)
+					return NextActivity;
+
+				// Move towards the last known position
+				wasMovingWithinRange = true;
+				return ActivityUtils.SequenceActivities(
+					move.MoveWithinRange(target, WDist.Zero, lastVisibleMaximumRange, checkTarget.CenterPosition, Color.Red),
+					this);
+			}
+
 			turnActivity = moveActivity = null;
 			attackStatus = AttackStatus.UnableToAttack;
 
@@ -74,7 +135,10 @@ namespace OpenRA.Mods.Common.Activities
 				return turnActivity;
 
 			if (attackStatus.HasFlag(AttackStatus.NeedsToMove))
+			{
+				wasMovingWithinRange = true;
 				return moveActivity;
+			}
 
 			return NextActivity;
 		}
@@ -104,7 +168,10 @@ namespace OpenRA.Mods.Common.Activities
 				var sightRange = rs != null ? rs.Range : WDist.FromCells(2);
 
 				attackStatus |= AttackStatus.NeedsToMove;
-				moveActivity = ActivityUtils.SequenceActivities(move.MoveWithinRange(target, sightRange), this);
+				moveActivity = ActivityUtils.SequenceActivities(
+					move.MoveWithinRange(target, sightRange, target.CenterPosition, Color.Red),
+					this);
+
 				return AttackStatus.NeedsToMove;
 			}
 
@@ -128,7 +195,12 @@ namespace OpenRA.Mods.Common.Activities
 					return AttackStatus.UnableToAttack;
 
 				attackStatus |= AttackStatus.NeedsToMove;
-				moveActivity = ActivityUtils.SequenceActivities(move.MoveWithinRange(target, minRange, maxRange), this);
+
+				var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+				moveActivity = ActivityUtils.SequenceActivities(
+					move.MoveWithinRange(target, minRange, maxRange, checkTarget.CenterPosition, Color.Red),
+					this);
+
 				return AttackStatus.NeedsToMove;
 			}
 
@@ -147,47 +219,4 @@ namespace OpenRA.Mods.Common.Activities
 			return AttackStatus.Attacking;
 		}
 	}
-
-	public static class TargetExts
-	{
-		/// <summary>Update (Frozen)Actor targets to account for visibility changes or actor replacement</summary>
-		public static Target Recalculate(this Target t, Player viewer)
-		{
-			// Check whether the target has transformed into something else
-			// HACK: This relies on knowing the internal implementation details of Target
-			if (t.Type == TargetType.Invalid && t.Actor != null && t.Actor.ReplacedByActor != null)
-				t = Target.FromActor(t.Actor.ReplacedByActor);
-
-			// Bot-controlled units aren't yet capable of understanding visibility changes
-			if (viewer.IsBot)
-				return t;
-
-			if (t.Type == TargetType.Actor)
-			{
-				// Actor has been hidden under the fog
-				if (!t.Actor.CanBeViewedByPlayer(viewer))
-				{
-					// Replace with FrozenActor if applicable, otherwise drop the target
-					var frozen = viewer.FrozenActorLayer.FromID(t.Actor.ActorID);
-					return frozen != null ? Target.FromFrozenActor(frozen) : Target.Invalid;
-				}
-			}
-			else if (t.Type == TargetType.FrozenActor)
-			{
-				// Frozen actor has been revealed
-				if (!t.FrozenActor.Visible || !t.FrozenActor.IsValid)
-				{
-					// Original actor is still alive
-					if (t.FrozenActor.Actor != null && t.FrozenActor.Actor.CanBeViewedByPlayer(viewer))
-						return Target.FromActor(t.FrozenActor.Actor);
-
-					// Original actor was killed while hidden
-					if (t.Actor == null)
-						return Target.Invalid;
-				}
-			}
-
-			return t;
-		}
-	}
 }

OpenRA.Mods.Common/Activities/CaptureActor.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System.Drawing;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
@@ -17,49 +18,62 @@ namespace OpenRA.Mods.Common.Activities
 {
 	public class CaptureActor : Enter
 	{
-		readonly Actor actor;
-		readonly CaptureManager targetManager;
 		readonly CaptureManager manager;
 
-		public CaptureActor(Actor self, Actor target)
-			: base(self, target, EnterBehaviour.Exit)
+		Actor enterActor;
+		CaptureManager enterCaptureManager;
+
+		public CaptureActor(Actor self, Target target)
+			: base(self, target, Color.Red)
 		{
-			actor = target;
 			manager = self.Trait<CaptureManager>();
-			targetManager = target.Trait<CaptureManager>();
 		}
 
-		protected override bool CanReserve(Actor self)
+		protected override bool TryStartEnter(Actor self, Actor targetActor)
 		{
-			return !actor.IsDead && !targetManager.BeingCaptured && targetManager.CanBeTargetedBy(actor, self, manager);
-		}
+			if (enterActor != targetActor)
+			{
+				enterActor = targetActor;
+				enterCaptureManager = targetActor.TraitOrDefault<CaptureManager>();
+			}
+
+			// Make sure we can still capture the target before entering
+			// (but not before, because this may stop the actor in the middle of nowhere)
+			if (enterCaptureManager == null || !enterCaptureManager.CanBeTargetedBy(enterActor, self, manager))
+			{
+				Cancel(self, true);
+				return false;
+			}
 
-		protected override bool TryStartEnter(Actor self)
-		{
 			// StartCapture returns false when a capture delay is enabled
 			// We wait until it returns true before allowing entering the target
 			Captures captures;
-			if (!manager.StartCapture(self, actor, targetManager, out captures))
+			if (!manager.StartCapture(self, enterActor, enterCaptureManager, out captures))
 				return false;
 
 			if (!captures.Info.ConsumedByCapture)
 			{
 				// Immediately capture without entering or disposing the actor
 				DoCapture(self, captures);
-				AbortOrExit(self);
+				Cancel(self, true);
 				return false;
 			}
 
 			return true;
 		}
 
-		protected override void OnInside(Actor self)
+		protected override void OnEnterComplete(Actor self, Actor targetActor)
 		{
-			if (!CanReserve(self))
+			// Make sure the target hasn't changed while entering
+			// OnEnterComplete is only called if targetActor is alive
+			if (enterActor != targetActor)
+				return;
+
+			if (enterCaptureManager.BeingCaptured || !enterCaptureManager.CanBeTargetedBy(enterActor, self, manager))
 				return;
 
 			// Prioritize capturing over sabotaging
-			var captures = manager.ValidCapturesWithLowestSabotageThreshold(self, actor, targetManager);
+			var captures = manager.ValidCapturesWithLowestSabotageThreshold(self, enterActor, enterCaptureManager);
 			if (captures == null)
 				return;
 
@@ -68,23 +82,23 @@ namespace OpenRA.Mods.Common.Activities
 
 		void DoCapture(Actor self, Captures captures)
 		{
-			var oldOwner = actor.Owner;
+			var oldOwner = enterActor.Owner;
 			self.World.AddFrameEndTask(w =>
 			{
 				// The target died or was already captured during this tick
-				if (actor.IsDead || oldOwner != actor.Owner)
+				if (enterActor.IsDead || oldOwner != enterActor.Owner)
 					return;
 
 				// Sabotage instead of capture
-				if (captures.Info.SabotageThreshold > 0 && !actor.Owner.NonCombatant)
+				if (captures.Info.SabotageThreshold > 0 && !enterActor.Owner.NonCombatant)
 				{
-					var health = actor.Trait<IHealth>();
+					var health = enterActor.Trait<IHealth>();
 
 					// Cast to long to avoid overflow when multiplying by the health
 					if (100 * (long)health.HP > captures.Info.SabotageThreshold * (long)health.MaxHP)
 					{
 						var damage = (int)((long)health.MaxHP * captures.Info.SabotageHPRemoval / 100);
-						actor.InflictDamage(self, new Damage(damage, captures.Info.SabotageDamageTypes));
+						enterActor.InflictDamage(self, new Damage(damage, captures.Info.SabotageDamageTypes));
 
 						if (captures.Info.ConsumedByCapture)
 							self.Dispose();
@@ -94,10 +108,10 @@ namespace OpenRA.Mods.Common.Activities
 				}
 
 				// Do the capture
-				actor.ChangeOwnerSync(self.Owner);
+				enterActor.ChangeOwnerSync(self.Owner);
 
-				foreach (var t in actor.TraitsImplementing<INotifyCapture>())
-					t.OnCapture(actor, self, oldOwner, self.Owner, captures.Info.CaptureTypes);
+				foreach (var t in enterActor.TraitsImplementing<INotifyCapture>())
+					t.OnCapture(enterActor, self, oldOwner, self.Owner, captures.Info.CaptureTypes);
 
 				if (self.Owner.Stances[oldOwner].HasStance(captures.Info.PlayerExperienceStances))
 				{
@@ -123,17 +137,14 @@ namespace OpenRA.Mods.Common.Activities
 			base.OnActorDispose(self);
 		}
 
-		void CancelCapture(Actor self)
+		protected override void OnCancel(Actor self)
 		{
-			manager.CancelCapture(self, actor, targetManager);
+			CancelCapture(self);
 		}
 
-		public override Activity Tick(Actor self)
+		void CancelCapture(Actor self)
 		{
-			if (!targetManager.CanBeTargetedBy(actor, self, manager))
-				Cancel(self);
-
-			return base.Tick(self);
+			manager.CancelCapture(self, enterActor, enterCaptureManager);
 		}
 	}
 }

OpenRA.Mods.Common/Activities/Demolish.cs

@@ -9,54 +9,79 @@
  */
 #endregion
 
+using System;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Mods.Common.Effects;
 using OpenRA.Mods.Common.Traits;
+using OpenRA.Traits;
 
 namespace OpenRA.Mods.Common.Activities
 {
 	class Demolish : Enter
 	{
-		readonly Actor target;
-		readonly IDemolishable[] demolishables;
 		readonly int delay;
 		readonly int flashes;
 		readonly int flashesDelay;
 		readonly int flashInterval;
 		readonly INotifyDemolition[] notifiers;
+		readonly EnterBehaviour enterBehaviour;
 
-		public Demolish(Actor self, Actor target, EnterBehaviour enterBehaviour, int delay,
+		Actor enterActor;
+		IDemolishable[] enterDemolishables;
+
+		public Demolish(Actor self, Target target, EnterBehaviour enterBehaviour, int delay,
 			int flashes, int flashesDelay, int flashInterval)
-			: base(self, target, enterBehaviour)
+			: base(self, target, Color.Red)
 		{
-			this.target = target;
-			demolishables = target.TraitsImplementing<IDemolishable>().ToArray();
 			notifiers = self.TraitsImplementing<INotifyDemolition>().ToArray();
 			this.delay = delay;
 			this.flashes = flashes;
 			this.flashesDelay = flashesDelay;
 			this.flashInterval = flashInterval;
+			this.enterBehaviour = enterBehaviour;
 		}
 
-		protected override bool CanReserve(Actor self)
+		protected override bool TryStartEnter(Actor self, Actor targetActor)
 		{
-			return demolishables.Any(i => i.IsValidTarget(target, self));
+			enterActor = targetActor;
+			enterDemolishables = targetActor.TraitsImplementing<IDemolishable>().ToArray();
+
+			// Make sure we can still demolish the target before entering
+			// (but not before, because this may stop the actor in the middle of nowhere)
+			if (!enterDemolishables.Any(i => i.IsValidTarget(enterActor, self)))
+			{
+				Cancel(self, true);
+				return false;
+			}
+
+			return true;
 		}
 
-		protected override void OnInside(Actor self)
+		protected override void OnEnterComplete(Actor self, Actor targetActor)
 		{
 			self.World.AddFrameEndTask(w =>
 			{
-				if (target.IsDead)
+				// Make sure the target hasn't changed while entering
+				// OnEnterComplete is only called if targetActor is alive
+				if (targetActor != enterActor)
 					return;
 
-				w.Add(new FlashTarget(target, count: flashes, delay: flashesDelay, interval: flashInterval));
+				if (!enterDemolishables.Any(i => i.IsValidTarget(enterActor, self)))
+					return;
+
+				w.Add(new FlashTarget(enterActor, count: flashes, delay: flashesDelay, interval: flashInterval));
 
 				foreach (var ind in notifiers)
 					ind.Demolishing(self);
 
-				foreach (var d in demolishables)
-					d.Demolish(target, self, delay);
+				foreach (var d in enterDemolishables)
+					d.Demolish(enterActor, self, delay);
+
+				if (enterBehaviour == EnterBehaviour.Dispose)
+					self.Dispose();
+				else if (enterBehaviour == EnterBehaviour.Suicide)
+					self.Kill(self);
 			});
 		}
 	}

OpenRA.Mods.Common/Activities/DonateCash.cs

@@ -9,44 +9,44 @@
  */
 #endregion
 
+using System.Drawing;
 using OpenRA.Mods.Common.Effects;
 using OpenRA.Mods.Common.Traits;
+using OpenRA.Traits;
 
 namespace OpenRA.Mods.Common.Activities
 {
 	class DonateCash : Enter
 	{
-		readonly Actor target;
 		readonly int payload;
-		readonly int experience;
+		readonly int playerExperience;
 
-		public DonateCash(Actor self, Actor target, int payload, int playerExperience)
-			: base(self, target, EnterBehaviour.Dispose)
+		public DonateCash(Actor self, Target target, int payload, int playerExperience)
+			: base(self, target, Color.Yellow)
 		{
-			this.target = target;
 			this.payload = payload;
-			this.experience = playerExperience;
+			this.playerExperience = playerExperience;
 		}
 
-		protected override void OnInside(Actor self)
+		protected override void OnEnterComplete(Actor self, Actor targetActor)
 		{
-			if (target.IsDead)
-				return;
-
-			var donated = target.Owner.PlayerActor.Trait<PlayerResources>().ChangeCash(payload);
+			var targetOwner = targetActor.Owner;
+			var donated = targetOwner.PlayerActor.Trait<PlayerResources>().ChangeCash(payload);
 
 			var exp = self.Owner.PlayerActor.TraitOrDefault<PlayerExperience>();
-			if (exp != null && target.Owner != self.Owner)
-				exp.GiveExperience(experience);
+			if (exp != null && targetOwner != self.Owner)
+				exp.GiveExperience(playerExperience);
 
 			if (self.Owner.IsAlliedWith(self.World.RenderPlayer))
-				self.World.AddFrameEndTask(w => w.Add(new FloatingText(target.CenterPosition, target.Owner.Color.RGB, FloatingText.FormatCashTick(donated), 30)));
+				self.World.AddFrameEndTask(w => w.Add(new FloatingText(targetActor.CenterPosition, targetOwner.Color.RGB, FloatingText.FormatCashTick(donated), 30)));
 
-			foreach (var nct in target.TraitsImplementing<INotifyCashTransfer>())
-				nct.OnAcceptingCash(target, self);
+			foreach (var nct in targetActor.TraitsImplementing<INotifyCashTransfer>())
+				nct.OnAcceptingCash(targetActor, self);
 
 			foreach (var nct in self.TraitsImplementing<INotifyCashTransfer>())
-				nct.OnDeliveringCash(self, target);
+				nct.OnDeliveringCash(self, targetActor);
+
+			self.Dispose();
 		}
 	}
 }

OpenRA.Mods.Common/Activities/DonateExperience.cs

@@ -9,45 +9,60 @@
  */
 #endregion
 
+using System.Drawing;
 using OpenRA.Activities;
+using OpenRA.Mods.Common.Effects;
 using OpenRA.Mods.Common.Traits;
+using OpenRA.Traits;
 
 namespace OpenRA.Mods.Common.Activities
 {
 	class DonateExperience : Enter
 	{
-		readonly Actor target;
-		readonly GainsExperience targetGainsExperience;
 		readonly int level;
 		readonly int playerExperience;
 
-		public DonateExperience(Actor self, Actor target, int level, int playerExperience, GainsExperience targetGainsExperience)
-			: base(self, target, EnterBehaviour.Dispose)
+		Actor enterActor;
+		GainsExperience enterGainsExperience;
+
+		public DonateExperience(Actor self, Target target, int level, int playerExperience)
+			: base(self, target, Color.Yellow)
 		{
-			this.target = target;
 			this.level = level;
 			this.playerExperience = playerExperience;
-			this.targetGainsExperience = targetGainsExperience;
 		}
 
-		protected override void OnInside(Actor self)
+		protected override bool TryStartEnter(Actor self, Actor targetActor)
 		{
-			if (target.IsDead)
+			enterActor = targetActor;
+			enterGainsExperience = targetActor.TraitOrDefault<GainsExperience>();
+
+			if (enterGainsExperience == null || enterGainsExperience.Level == enterGainsExperience.MaxLevel)
+			{
+				Cancel(self, true);
+				return false;
+			}
+
+			return true;
+		}
+
+		protected override void OnEnterComplete(Actor self, Actor targetActor)
+		{
+			// Make sure the target hasn't changed while entering
+			// OnEnterComplete is only called if targetActor is alive
+			if (targetActor != enterActor)
 				return;
 
-			targetGainsExperience.GiveLevels(level);
+			if (enterGainsExperience.Level == enterGainsExperience.MaxLevel)
+				return;
+
+			enterGainsExperience.GiveLevels(level);
 
 			var exp = self.Owner.PlayerActor.TraitOrDefault<PlayerExperience>();
-			if (exp != null && target.Owner != self.Owner)
+			if (exp != null && enterActor.Owner != self.Owner)
 				exp.GiveExperience(playerExperience);
-		}
 
-		public override Activity Tick(Actor self)
-		{
-			if (target.IsDead || targetGainsExperience.Level == targetGainsExperience.MaxLevel)
-				Cancel(self);
-
-			return base.Tick(self);
+			self.Dispose();
 		}
 	}
 }

OpenRA.Mods.Common/Activities/Enter.cs

@@ -1,6 +1,6 @@
 #region Copyright & License Information
 /*
- * Copyright 2007-2018 The OpenRA Developers (see AUTHORS)
+ * Copyright 2007-2019 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
@@ -10,6 +10,7 @@
 #endregion
 
 using System;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
@@ -21,287 +22,154 @@ namespace OpenRA.Mods.Common.Activities
 
 	public abstract class Enter : Activity
 	{
-		public enum ReserveStatus { None, TooFar, Pending, Ready }
-		enum EnterState { ApproachingOrEntering, WaitingToEnter, Inside, Exiting, Done }
+		enum EnterState { Approaching, Waiting, Entering, Exiting }
 
 		readonly IMove move;
-		readonly int maxTries = 0;
-		readonly EnterBehaviour enterBehaviour;
-		readonly bool repathWhileMoving;
+		readonly Color? targetLineColor;
 
-		public Target Target { get { return target; } }
 		Target target;
-		EnterState nextState = EnterState.ApproachingOrEntering; // Hint/starting point for next state
-		bool isEnteringOrInside = false; // Used to know if exiting should be used
-		WPos savedPos; // Position just before entering
-		Activity inner;
-		bool firstApproach = true;
+		Target lastVisibleTarget;
+		bool useLastVisibleTarget;
+		EnterState lastState = EnterState.Approaching;
 
-		protected Enter(Actor self, Actor target, EnterBehaviour enterBehaviour, int maxTries = 1, bool repathWhileMoving = true)
+		protected Enter(Actor self, Target target, Color? targetLineColor = null)
 		{
 			move = self.Trait<IMove>();
-			this.target = Target.FromActor(target);
-			this.maxTries = maxTries;
-			this.enterBehaviour = enterBehaviour;
-			this.repathWhileMoving = repathWhileMoving;
+			this.target = target;
+			this.targetLineColor = targetLineColor;
 		}
 
-		// CanEnter(target) should to be true; otherwise, Enter may abort.
-		// Tries counter starts at 1 (reset every tick)
-		protected virtual bool TryGetAlternateTarget(Actor self, int tries, ref Target target) { return false; }
-		protected virtual bool CanReserve(Actor self) { return true; }
-		protected virtual ReserveStatus Reserve(Actor self)
-		{
-			return !CanReserve(self) ? ReserveStatus.None : move.CanEnterTargetNow(self, target) ? ReserveStatus.Ready : ReserveStatus.TooFar;
-		}
-
-		protected virtual void Unreserve(Actor self, bool abort) { }
-		protected virtual void OnInside(Actor self) { }
-
 		/// <summary>
-		/// Called when the actor is ready to transition from approaching to entering the target.
-		/// Return true to start entering, or false to wait in the WaitingToEnter state.
+		/// Called early in the activity tick to allow subclasses to update state.
+		/// Call Cancel(self, true) if it is no longer valid to enter
 		/// </summary>
-		protected virtual bool TryStartEnter(Actor self) { return true; }
+		protected virtual void TickInner(Actor self, Target target, bool targetIsDeadOrHiddenActor) { }
 
-		protected bool TryGetAlternateTargetInCircle(
-			Actor self, WDist radius, Action<Target> update, Func<Actor, bool> primaryFilter, Func<Actor, bool>[] preferenceFilters = null)
+		/// <summary>
+		/// Called when the actor is ready to transition from approaching to entering the target actor.
+		/// Return true to start entering, or false to wait in the WaitingToEnter state.
+		/// Call Cancel(self, true) before returning false if it is no longer valid to enter
+		/// </summary>
+		protected virtual bool TryStartEnter(Actor self, Actor targetActor) { return true; }
+
+		/// <summary>
+		/// Called when the actor has entered the target actor
+		/// Return true if the action succeeded and the actor should be Killed/Disposed
+		/// (assuming the relevant EnterBehaviour), or false if the actor should exit unharmed
+		/// </summary>
+		protected virtual void OnEnterComplete(Actor self, Actor targetActor) { }
+
+		/// <summary>
+		/// Called when the activity is cancelled to allow subclasses to clean up their own state.
+		/// </summary>
+		protected virtual void OnCancel(Actor self) { }
+
+		Activity moveActivity;
+		public override Activity Tick(Actor self)
 		{
-			var diff = new WVec(radius, radius, WDist.Zero);
-			var candidates = self.World.ActorMap.ActorsInBox(self.CenterPosition - diff, self.CenterPosition + diff)
-				.Where(primaryFilter).Select(a => new { Actor = a, Ls = (self.CenterPosition - a.CenterPosition).HorizontalLengthSquared })
-				.Where(p => p.Ls <= radius.LengthSquared).OrderBy(p => p.Ls).Select(p => p.Actor);
-			if (preferenceFilters != null)
-				foreach (var filter in preferenceFilters)
+			// Update our view of the target
+			bool targetIsHiddenActor;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
+				lastVisibleTarget = Target.FromTargetPositions(target);
+
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// Cancel immediately if the target died while we were entering it
+			if (!IsCanceled && useLastVisibleTarget && lastState == EnterState.Entering)
+				Cancel(self, true);
+
+			TickInner(self, target, useLastVisibleTarget);
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget && targetLineColor.HasValue)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, targetLineColor.Value, false);
+
+			// We need to wait for movement to finish before transitioning to
+			// the next state or next activity
+			if (moveActivity != null)
+			{
+				moveActivity = ActivityUtils.RunActivity(self, moveActivity);
+				if (moveActivity != null)
+					return this;
+			}
+
+			// Note that lastState refers to what we have just *finished* doing
+			switch (lastState)
+			{
+				case EnterState.Approaching:
+				case EnterState.Waiting:
 				{
-					var preferredCandidate = candidates.FirstOrDefault(filter);
-					if (preferredCandidate == null)
-						continue;
-					target = Target.FromActor(preferredCandidate);
-					update(target);
-					return true;
+					// NOTE: We can safely cancel in this case because we know the
+					// actor has finished any in-progress move activities
+					if (IsCanceled)
+						return NextActivity;
+
+					// Lost track of the target
+					if (useLastVisibleTarget && lastVisibleTarget.Type == TargetType.Invalid)
+						return NextActivity;
+
+					// We are not next to the target - lets fix that
+					if (target.Type != TargetType.Invalid && !move.CanEnterTargetNow(self, target))
+					{
+						lastState = EnterState.Approaching;
+
+						// Target lines are managed by this trait, so we do not pass targetLineColor
+						var initialTargetPosition = (useLastVisibleTarget ? lastVisibleTarget : target).CenterPosition;
+						moveActivity = ActivityUtils.RunActivity(self, move.MoveToTarget(self, target, initialTargetPosition));
+						break;
+					}
+
+					// We are next to where we thought the target should be, but it isn't here
+					// There's not much more we can do here
+					if (useLastVisibleTarget || target.Type != TargetType.Actor)
+						return NextActivity;
+
+					// Are we ready to move into the target?
+					if (TryStartEnter(self, target.Actor))
+					{
+						lastState = EnterState.Entering;
+						moveActivity = ActivityUtils.RunActivity(self, move.MoveIntoTarget(self, target));
+						return this;
+					}
+
+					// Subclasses can cancel the activity during TryStartEnter
+					// Return immediately to avoid an extra tick's delay
+					if (IsCanceled)
+						return NextActivity;
+
+					lastState = EnterState.Waiting;
+					break;
 				}
 
-			var candidate = candidates.FirstOrDefault();
-			if (candidate == null)
-				return false;
-			target = Target.FromActor(candidate);
-			update(target);
-			return true;
-		}
+				case EnterState.Entering:
+				{
+					// Check that we reached the requested position
+					var targetPos = target.Positions.PositionClosestTo(self.CenterPosition);
+					if (!IsCanceled && self.CenterPosition == targetPos && target.Type == TargetType.Actor)
+						OnEnterComplete(self, target.Actor);
 
-		// Called when inner activity is this and returns inner activity for next tick.
-		protected virtual Activity InsideTick(Actor self) { return null; }
+					lastState = EnterState.Exiting;
+					moveActivity = ActivityUtils.RunActivity(self, move.MoveIntoWorld(self, self.Location));
+					break;
+				}
 
-		// Abort entering and/or leave if necessary
-		protected virtual void AbortOrExit(Actor self)
-		{
-			if (nextState == EnterState.Done)
-				return;
-			nextState = isEnteringOrInside ? EnterState.Exiting : EnterState.Done;
-			if (inner == this)
-				inner = null;
-			else if (inner != null)
-				inner.Cancel(self);
-			if (isEnteringOrInside)
-				Unreserve(self, true);
-		}
+				case EnterState.Exiting:
+					return NextActivity;
+			}
 
-		// Cancel inner activity and mark as done unless already leaving or done
-		protected void Done(Actor self)
-		{
-			if (nextState == EnterState.Done)
-				return;
-			nextState = EnterState.Done;
-			if (inner == this)
-				inner = null;
-			else if (inner != null)
-				inner.Cancel(self);
+			return this;
 		}
 
 		public override bool Cancel(Actor self, bool keepQueue = false)
 		{
-			AbortOrExit(self);
-			if (nextState < EnterState.Exiting)
-				return base.Cancel(self);
-			else
-				NextActivity = null;
+			OnCancel(self);
 
-			return true;
-		}
+			if (!IsCanceled && moveActivity != null && !moveActivity.Cancel(self))
+				return false;
 
-		ReserveStatus TryReserveElseTryAlternateReserve(Actor self)
-		{
-			for (var tries = 0;;)
-			{
-				switch (Reserve(self))
-				{
-					case ReserveStatus.None:
-						if (++tries > maxTries || !TryGetAlternateTarget(self, tries, ref target))
-							return ReserveStatus.None;
-						continue;
-					case ReserveStatus.TooFar:
-						// Always goto to transport on first approach
-						if (firstApproach)
-						{
-							firstApproach = false;
-							return ReserveStatus.TooFar;
-						}
-
-						if (++tries > maxTries)
-							return ReserveStatus.TooFar;
-						Target t = target;
-						if (!TryGetAlternateTarget(self, tries, ref t))
-							return ReserveStatus.TooFar;
-
-						var targetPosition = target.Positions.PositionClosestTo(self.CenterPosition);
-						var alternatePosition = t.Positions.PositionClosestTo(self.CenterPosition);
-						if ((targetPosition - self.CenterPosition).HorizontalLengthSquared <= (alternatePosition - self.CenterPosition).HorizontalLengthSquared)
-							return ReserveStatus.TooFar;
-						target = t;
-						continue;
-					case ReserveStatus.Pending:
-						return ReserveStatus.Pending;
-					case ReserveStatus.Ready:
-						return ReserveStatus.Ready;
-				}
-			}
-		}
-
-		EnterState FindAndTransitionToNextState(Actor self)
-		{
-			switch (nextState)
-			{
-				case EnterState.ApproachingOrEntering:
-
-					// Reserve to enter or approach
-					isEnteringOrInside = false;
-					switch (TryReserveElseTryAlternateReserve(self))
-					{
-						case ReserveStatus.None:
-							return EnterState.Done; // No available target -> abort to next activity
-						case ReserveStatus.TooFar:
-						{
-							var moveTarget = repathWhileMoving ? target : Target.FromPos(target.Positions.PositionClosestTo(self.CenterPosition));
-							inner = move.MoveToTarget(self, moveTarget); // Approach
-							return EnterState.ApproachingOrEntering;
-						}
-
-						case ReserveStatus.Pending:
-							return EnterState.ApproachingOrEntering; // Retry next tick
-						case ReserveStatus.Ready:
-							break; // Reserved target -> start entering target
-					}
-
-					// Can we enter yet?
-					if (!TryStartEnter(self))
-						return EnterState.WaitingToEnter;
-
-					// Entering
-					isEnteringOrInside = true;
-					savedPos = self.CenterPosition; // Save position of self, before entering, for returning on exit
-
-					inner = move.MoveIntoTarget(self, target); // Enter
-
-					if (inner != null)
-					{
-						nextState = EnterState.Inside; // Should be inside once inner activity is null
-						return EnterState.ApproachingOrEntering;
-					}
-
-					// Can enter but there is no activity for it, so go inside without one
-					goto case EnterState.Inside;
-
-				case EnterState.Inside:
-					// Might as well teleport into target if there is no MoveIntoTarget activity
-					if (nextState == EnterState.ApproachingOrEntering)
-						nextState = EnterState.Inside;
-
-					// Otherwise, try to recover from moving target
-					else if (target.Positions.PositionClosestTo(self.CenterPosition) != self.CenterPosition)
-					{
-						nextState = EnterState.ApproachingOrEntering;
-						Unreserve(self, false);
-						if (Reserve(self) == ReserveStatus.Ready)
-						{
-							inner = move.MoveIntoTarget(self, target); // Enter
-							if (inner != null)
-								return EnterState.ApproachingOrEntering;
-
-							nextState = EnterState.ApproachingOrEntering;
-							goto case EnterState.ApproachingOrEntering;
-						}
-
-						nextState = EnterState.ApproachingOrEntering;
-						isEnteringOrInside = false;
-						inner = move.MoveIntoWorld(self, self.World.Map.CellContaining(savedPos));
-
-						return EnterState.ApproachingOrEntering;
-					}
-
-					OnInside(self);
-
-					if (enterBehaviour == EnterBehaviour.Suicide)
-						self.Kill(self);
-					else if (enterBehaviour == EnterBehaviour.Dispose)
-						self.Dispose();
-
-					// Return if Abort(Actor) or Done(self) was called from OnInside.
-					if (nextState >= EnterState.Exiting)
-						return EnterState.Inside;
-
-					inner = this; // Start inside activity
-					nextState = EnterState.Exiting; // Exit once inner activity is null (unless Done(self) is called)
-					return EnterState.Inside;
-
-				// TODO: Handle target moved while inside or always call done for movable targets and use a separate exit activity
-				case EnterState.Exiting:
-					inner = move.MoveIntoWorld(self, self.World.Map.CellContaining(savedPos));
-
-					// If not successfully exiting, retry on next tick
-					if (inner == null)
-						return EnterState.Exiting;
-					isEnteringOrInside = false;
-					nextState = EnterState.Done;
-					return EnterState.Exiting;
-
-				case EnterState.Done:
-					return EnterState.Done;
-			}
-
-			return EnterState.Done; // dummy to quiet dumb compiler
-		}
-
-		Activity CanceledTick(Actor self)
-		{
-			if (inner == null)
-				return ActivityUtils.RunActivity(self, NextActivity);
-			inner.Cancel(self);
-			inner.Queue(NextActivity);
-			return ActivityUtils.RunActivity(self, inner);
-		}
-
-		public override Activity Tick(Actor self)
-		{
-			if (IsCanceled)
-				return CanceledTick(self);
-
-			// Check target validity if not exiting or done
-			if (nextState != EnterState.Done && (target.Type != TargetType.Actor || !target.IsValidFor(self)))
-				AbortOrExit(self);
-
-			// If no current activity, tick next activity
-			if (inner == null && FindAndTransitionToNextState(self) == EnterState.Done)
-				return CanceledTick(self);
-
-			// Run inner activity/InsideTick
-			inner = inner == this ? InsideTick(self) : ActivityUtils.RunActivity(self, inner);
-
-			// If we are finished, move on to next activity
-			if (inner == null && nextState == EnterState.Done)
-				return NextActivity;
-
-			return this;
+			return base.Cancel(self, keepQueue);
 		}
 	}
 }

OpenRA.Mods.Common/Activities/EnterTransport.cs

@@ -10,6 +10,9 @@
 #endregion
 
 using System;
+using System.Drawing;
+using System.Linq;
+using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
 
@@ -18,59 +21,124 @@ namespace OpenRA.Mods.Common.Activities
 	class EnterTransport : Enter
 	{
 		readonly Passenger passenger;
-		readonly int maxTries;
-		Actor transport;
-		Cargo cargo;
 
-		public EnterTransport(Actor self, Actor transport, int maxTries = 0, bool repathWhileMoving = true)
-			: base(self, transport, EnterBehaviour.Exit, maxTries, repathWhileMoving)
+		Actor enterActor;
+		Cargo enterCargo;
+
+		public EnterTransport(Actor self, Target target)
+			: base(self, target, Color.Green)
 		{
-			this.transport = transport;
-			this.maxTries = maxTries;
-			cargo = transport.Trait<Cargo>();
 			passenger = self.Trait<Passenger>();
 		}
 
-		protected override void Unreserve(Actor self, bool abort) { passenger.Unreserve(self); }
-		protected override bool CanReserve(Actor self) { return cargo.Unloading || cargo.CanLoad(transport, self); }
-		protected override ReserveStatus Reserve(Actor self)
+		protected override bool TryStartEnter(Actor self, Actor targetActor)
 		{
-			var status = base.Reserve(self);
-			if (status != ReserveStatus.Ready)
-				return status;
-			if (passenger.Reserve(self, cargo))
-				return ReserveStatus.Ready;
-			return ReserveStatus.Pending;
+			enterActor = targetActor;
+			enterCargo = targetActor.TraitOrDefault<Cargo>();
+
+			// Make sure we can still enter the transport
+			// (but not before, because this may stop the actor in the middle of nowhere)
+			if (enterCargo == null || !passenger.Reserve(self, enterCargo))
+			{
+				Cancel(self, true);
+				return false;
+			}
+
+			return true;
 		}
 
-		protected override void OnInside(Actor self)
+		protected override void OnEnterComplete(Actor self, Actor targetActor)
 		{
 			self.World.AddFrameEndTask(w =>
 			{
-				if (self.IsDead || transport.IsDead || !cargo.CanLoad(transport, self))
+				// Make sure the target hasn't changed while entering
+				// OnEnterComplete is only called if targetActor is alive
+				if (targetActor != enterActor)
 					return;
 
-				cargo.Load(transport, self);
+				if (!enterCargo.CanLoad(enterActor, self))
+					return;
+
+				enterCargo.Load(enterActor, self);
 				w.Remove(self);
+
+				// Preemptively cancel any activities to avoid an edge-case where successively queued
+				// EnterTransports corrupt the actor state. Activities are cancelled again on unload
+				self.CancelActivity();
 			});
-
-			Done(self);
-
-			// Preemptively cancel any activities to avoid an edge-case where successively queued
-			// EnterTransports corrupt the actor state. Activities are cancelled again on unload
-			self.CancelActivity();
 		}
 
-		protected override bool TryGetAlternateTarget(Actor self, int tries, ref Target target)
+		protected override void OnCancel(Actor self)
 		{
-			if (tries > maxTries)
+			passenger.Unreserve(self);
+		}
+
+		protected override void OnLastRun(Actor self)
+		{
+			passenger.Unreserve(self);
+		}
+	}
+
+	class EnterTransports : Activity
+	{
+		readonly string type;
+		readonly Passenger passenger;
+
+		Activity enterTransport;
+
+		public EnterTransports(Actor self, Target primaryTarget)
+		{
+			passenger = self.Trait<Passenger>();
+			if (primaryTarget.Type == TargetType.Actor)
+				type = primaryTarget.Actor.Info.Name;
+
+			enterTransport = new EnterTransport(self, primaryTarget);
+		}
+
+		public override Activity Tick(Actor self)
+		{
+			if (enterTransport != null)
+			{
+				enterTransport = ActivityUtils.RunActivity(self, enterTransport);
+				if (enterTransport != null)
+					return this;
+			}
+
+			// Try and find a new transport nearby
+			if (IsCanceled || string.IsNullOrEmpty(type))
+				return NextActivity;
+
+			Func<Actor, bool> isValidTransport = a =>
+			{
+				var c = a.TraitOrDefault<Cargo>();
+				return c != null && c.Info.Types.Contains(passenger.Info.CargoType) &&
+				       (c.Unloading || c.CanLoad(a, self));
+			};
+
+			var candidates = self.World.FindActorsInCircle(self.CenterPosition, passenger.Info.AlternateTransportScanRange)
+				.Where(isValidTransport)
+				.ToList();
+
+			// Prefer transports of the same type as the primary
+			var transport = candidates.Where(a => a.Info.Name == type).ClosestTo(self);
+			if (transport == null)
+				transport = candidates.ClosestTo(self);
+
+			if (transport != null)
+			{
+				enterTransport = ActivityUtils.RunActivity(self, new EnterTransport(self, Target.FromActor(transport)));
+				return this;
+			}
+
+			return NextActivity;
+		}
+
+		public override bool Cancel(Actor self, bool keepQueue = false)
+		{
+			if (!IsCanceled && enterTransport != null && !enterTransport.Cancel(self))
 				return false;
-			var type = target.Actor.Info.Name;
-			return TryGetAlternateTargetInCircle(
-				self, passenger.Info.AlternateTransportScanRange,
-				t => { transport = t.Actor; cargo = t.Actor.Trait<Cargo>(); }, // update transport and cargo
-				a => { var c = a.TraitOrDefault<Cargo>(); return c != null && c.Info.Types.Contains(passenger.Info.CargoType) && (c.Unloading || c.CanLoad(a, self)); },
-				new Func<Actor, bool>[] { a => a.Info.Name == type }); // Prefer transports of the same type
+
+			return base.Cancel(self, keepQueue);
 		}
 	}
 }

OpenRA.Mods.Common/Activities/FindResources.cs

@@ -53,7 +53,10 @@ namespace OpenRA.Mods.Common.Activities
 				return NextActivity;
 
 			if (harv.IsFull)
-				return ActivityUtils.SequenceActivities(new DeliverResources(self), NextActivity);
+			{
+				// HACK: DeliverResources is ignored if there are queued activities, so discard NextActivity
+				return ActivityUtils.SequenceActivities(new DeliverResources(self));
+			}
 
 			var closestHarvestablePosition = ClosestHarvestablePos(self);
 

OpenRA.Mods.Common/Activities/Move/Follow.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System.Drawing;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
@@ -17,36 +18,74 @@ namespace OpenRA.Mods.Common.Activities
 {
 	public class Follow : Activity
 	{
-		readonly Target target;
 		readonly WDist minRange;
 		readonly WDist maxRange;
 		readonly IMove move;
+		readonly Color? targetLineColor;
+		Target target;
+		Target lastVisibleTarget;
+		bool useLastVisibleTarget;
+		bool wasMovingWithinRange;
 
-		public Follow(Actor self, Target target, WDist minRange, WDist maxRange)
+		public Follow(Actor self, Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition, Color? targetLineColor = null)
 		{
 			this.target = target;
 			this.minRange = minRange;
 			this.maxRange = maxRange;
-
+			this.targetLineColor = targetLineColor;
 			move = self.Trait<IMove>();
+
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+			else if (initialTargetPosition.HasValue)
+				lastVisibleTarget = Target.FromPos(initialTargetPosition.Value);
 		}
 
 		public override Activity Tick(Actor self)
 		{
-			if (IsCanceled || !target.IsValidFor(self))
+			if (IsCanceled)
 				return NextActivity;
 
-			var cachedPosition = target.CenterPosition;
-			var path = move.MoveWithinRange(target, minRange, maxRange);
+			bool targetIsHiddenActor;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
+				lastVisibleTarget = Target.FromTargetPositions(target);
 
-			// We are already in range, so wait until the target moves before doing anything
-			if (target.IsInRange(self.CenterPosition, maxRange) && !target.IsInRange(self.CenterPosition, minRange))
-			{
-				var wait = new WaitFor(() => !target.IsValidFor(self) || target.CenterPosition != cachedPosition);
-				return ActivityUtils.SequenceActivities(wait, path, this);
-			}
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
 
-			return ActivityUtils.SequenceActivities(path, this);
+			// If we are ticking again after previously sequencing a MoveWithRange then that move must have completed
+			// Either we are in range and can see the target, or we've lost track of it and should give up
+			if (wasMovingWithinRange && targetIsHiddenActor)
+				return NextActivity;
+
+			wasMovingWithinRange = false;
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget && targetLineColor.HasValue)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, targetLineColor.Value, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				return NextActivity;
+
+			var pos = self.CenterPosition;
+			var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+
+			// We've reached the required range - if the target is visible and valid then we wait
+			// otherwise if it is hidden or dead we give up
+			if (checkTarget.IsInRange(pos, maxRange) && !checkTarget.IsInRange(pos, minRange))
+				return useLastVisibleTarget ? NextActivity : this;
+
+			// Move into range
+			wasMovingWithinRange = true;
+			return ActivityUtils.SequenceActivities(
+				move.MoveWithinRange(target, minRange, maxRange, checkTarget.CenterPosition, targetLineColor),
+				this);
 		}
 	}
 }

OpenRA.Mods.Common/Activities/Move/Move.cs

@@ -386,6 +386,9 @@ namespace OpenRA.Mods.Common.Activities
 
 			public override Activity Tick(Actor self)
 			{
+				if (Move.mobile.IsTraitDisabled)
+					return this;
+
 				var ret = InnerTick(self, Move.mobile);
 				Move.mobile.IsMoving = ret is MovePart;
 

OpenRA.Mods.Common/Activities/Move/MoveAdjacentTo.cs

@@ -26,38 +26,45 @@ namespace OpenRA.Mods.Common.Activities
 		protected readonly Mobile Mobile;
 		readonly IPathFinder pathFinder;
 		readonly DomainIndex domainIndex;
+		readonly Color? targetLineColor;
 
-		Target target;
-		bool canHideUnderFog;
 		protected Target Target
 		{
 			get
 			{
-				return target;
-			}
-
-			private set
-			{
-				target = value;
-				if (target.Type == TargetType.Actor)
-					canHideUnderFog = target.Actor.Info.HasTraitInfo<HiddenUnderFogInfo>();
+				return useLastVisibleTarget ? lastVisibleTarget : target;
 			}
 		}
 
-		protected CPos targetPosition;
+		Target target;
+		Target lastVisibleTarget;
+		protected CPos lastVisibleTargetLocation;
+		bool useLastVisibleTarget;
+
 		Activity inner;
 		bool repath;
 
-		public MoveAdjacentTo(Actor self, Target target)
+		public MoveAdjacentTo(Actor self, Target target, WPos? initialTargetPosition = null, Color? targetLineColor = null)
 		{
-			Target = target;
-
+			this.target = target;
+			this.targetLineColor = targetLineColor;
 			Mobile = self.Trait<Mobile>();
 			pathFinder = self.World.WorldActor.Trait<IPathFinder>();
 			domainIndex = self.World.WorldActor.Trait<DomainIndex>();
 
-			if (target.IsValidFor(self))
-				targetPosition = self.World.Map.CellContaining(target.CenterPosition);
+			// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+			// Moving to any position (even if quite stale) is still better than immediately giving up
+			if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+			    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+			{
+				lastVisibleTarget = Target.FromPos(target.CenterPosition);
+				lastVisibleTargetLocation = self.World.Map.CellContaining(target.CenterPosition);
+			}
+			else if (initialTargetPosition.HasValue)
+			{
+				lastVisibleTarget = Target.FromPos(initialTargetPosition.Value);
+				lastVisibleTargetLocation = self.World.Map.CellContaining(initialTargetPosition.Value);
+			}
 
 			repath = true;
 		}
@@ -67,9 +74,9 @@ namespace OpenRA.Mods.Common.Activities
 			return false;
 		}
 
-		protected virtual bool ShouldRepath(Actor self, CPos oldTargetPosition)
+		protected virtual bool ShouldRepath(Actor self, CPos targetLocation)
 		{
-			return targetPosition != oldTargetPosition;
+			return lastVisibleTargetLocation != targetLocation;
 		}
 
 		protected virtual IEnumerable<CPos> CandidateMovementCells(Actor self)
@@ -79,19 +86,30 @@ namespace OpenRA.Mods.Common.Activities
 
 		public override Activity Tick(Actor self)
 		{
-			var targetIsValid = Target.IsValidFor(self);
-
-			// Target moved under the fog. Move to its last known position.
-			if (Target.Type == TargetType.Actor && canHideUnderFog
-				&& !Target.Actor.CanBeViewedByPlayer(self.Owner))
+			bool targetIsHiddenActor;
+			var oldTargetLocation = lastVisibleTargetLocation;
+			target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+			if (!targetIsHiddenActor && target.Type == TargetType.Actor)
 			{
-				if (inner != null)
-					inner.Cancel(self);
-
-				self.SetTargetLine(Target.FromCell(self.World, targetPosition), Color.Green);
-				return ActivityUtils.RunActivity(self, new AttackMoveActivity(self, Mobile.MoveTo(targetPosition, 0)));
+				lastVisibleTarget = Target.FromTargetPositions(target);
+				lastVisibleTargetLocation = self.World.Map.CellContaining(target.CenterPosition);
 			}
 
+			var oldUseLastVisibleTarget = useLastVisibleTarget;
+			useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
+
+			// Update target lines if required
+			if (useLastVisibleTarget != oldUseLastVisibleTarget && targetLineColor.HasValue)
+				self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, targetLineColor.Value, false);
+
+			// Target is hidden or dead, and we don't have a fallback position to move towards
+			if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				return NextActivity;
+
+			// Target is equivalent to checkTarget variable in other activities
+			// value is either lastVisibleTarget or target based on visibility and validity
+			var targetIsValid = Target.IsValidFor(self);
+
 			// Inner move order has completed.
 			if (inner == null)
 			{
@@ -105,26 +123,16 @@ namespace OpenRA.Mods.Common.Activities
 				repath = false;
 			}
 
-			if (targetIsValid)
+			// Cancel the current path if the activity asks to stop, or asks to repath
+			// The repath happens once the move activity stops in the next cell
+			var shouldStop = ShouldStop(self, oldTargetLocation);
+			var shouldRepath = targetIsValid && !repath && ShouldRepath(self, oldTargetLocation);
+			if (shouldStop || shouldRepath)
 			{
-				// Check if the target has moved
-				var oldTargetPosition = targetPosition;
-				targetPosition = self.World.Map.CellContaining(Target.CenterPosition);
+				if (inner != null)
+					inner.Cancel(self);
 
-				var shouldStop = ShouldStop(self, oldTargetPosition);
-				if (shouldStop || (!repath && ShouldRepath(self, oldTargetPosition)))
-				{
-					// Finish moving into the next cell and then repath.
-					if (inner != null)
-						inner.Cancel(self);
-
-					repath = !shouldStop;
-				}
-			}
-			else
-			{
-				// Target became invalid. Move to its last known position.
-				Target = Target.FromCell(self.World, targetPosition);
+				repath = shouldRepath;
 			}
 
 			// Ticks the inner move activity to actually move the actor.
@@ -147,7 +155,7 @@ namespace OpenRA.Mods.Common.Activities
 				return NoPath;
 
 			using (var fromSrc = PathSearch.FromPoints(self.World, Mobile.Info.LocomotorInfo, self, searchCells, loc, true))
-			using (var fromDest = PathSearch.FromPoint(self.World, Mobile.Info.LocomotorInfo, self, loc, targetPosition, true).Reverse())
+			using (var fromDest = PathSearch.FromPoint(self.World, Mobile.Info.LocomotorInfo, self, loc, lastVisibleTargetLocation, true).Reverse())
 				return pathFinder.FindBidiPath(fromSrc, fromDest);
 		}
 

OpenRA.Mods.Common/Activities/Move/MoveWithinRange.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Traits;
 
@@ -20,8 +21,9 @@ namespace OpenRA.Mods.Common.Activities
 		readonly WDist maxRange;
 		readonly WDist minRange;
 
-		public MoveWithinRange(Actor self, Target target, WDist minRange, WDist maxRange)
-			: base(self, target)
+		public MoveWithinRange(Actor self, Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
+			: base(self, target, initialTargetPosition, targetLineColor)
 		{
 			this.minRange = minRange;
 			this.maxRange = maxRange;
@@ -36,7 +38,7 @@ namespace OpenRA.Mods.Common.Activities
 
 		protected override bool ShouldRepath(Actor self, CPos oldTargetPosition)
 		{
-			return targetPosition != oldTargetPosition && (!AtCorrectRange(self.CenterPosition)
+			return lastVisibleTargetLocation != oldTargetPosition && (!AtCorrectRange(self.CenterPosition)
 				|| !Mobile.CanInteractWithGroundLayer(self));
 		}
 
@@ -46,7 +48,7 @@ namespace OpenRA.Mods.Common.Activities
 			var maxCells = (maxRange.Length + 1023) / 1024;
 			var minCells = minRange.Length / 1024;
 
-			return map.FindTilesInAnnulus(targetPosition, minCells, maxCells)
+			return map.FindTilesInAnnulus(lastVisibleTargetLocation, minCells, maxCells)
 				.Where(c => AtCorrectRange(map.CenterOfSubCell(c, Mobile.FromSubCell)));
 		}
 

OpenRA.Mods.Common/Activities/Move/VisualMoveIntoTarget.cs

@@ -0,0 +1,97 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2019 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 OpenRA.Activities;
+using OpenRA.Mods.Common.Traits;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Activities
+{
+	public class VisualMoveIntoTarget : Activity
+	{
+		readonly Mobile mobile;
+		readonly Target target;
+		readonly WDist targetMovementThreshold;
+		WPos targetStartPos;
+
+		public VisualMoveIntoTarget(Actor self, Target target, WDist targetMovementThreshold)
+		{
+			mobile = self.Trait<Mobile>();
+			this.target = target;
+			this.targetMovementThreshold = targetMovementThreshold;
+		}
+
+		protected override void OnFirstRun(Actor self)
+		{
+			targetStartPos = target.Positions.PositionClosestTo(self.CenterPosition);
+			mobile.IsMoving = true;
+		}
+
+		public override Activity Tick(Actor self)
+		{
+			if (ChildActivity != null)
+			{
+				ChildActivity = ActivityUtils.RunActivity(self, ChildActivity);
+				if (ChildActivity != null)
+					return this;
+			}
+
+			if (IsCanceled || target.Type == TargetType.Invalid)
+				return NextActivity;
+
+			if (mobile.IsTraitDisabled)
+				return this;
+
+			var currentPos = self.CenterPosition;
+			var targetPos = target.Positions.PositionClosestTo(currentPos);
+
+			// Give up if the target has moved too far
+			if (targetMovementThreshold > WDist.Zero && (targetPos - targetStartPos).LengthSquared > targetMovementThreshold.LengthSquared)
+				return NextActivity;
+
+			// Turn if required
+			var delta = targetPos - currentPos;
+			var facing = delta.HorizontalLengthSquared != 0 ? delta.Yaw.Facing : mobile.Facing;
+			if (facing != mobile.Facing)
+			{
+				var turn = ActivityUtils.RunActivity(self, new Turn(self, facing));
+				if (turn != null)
+					QueueChild(turn);
+
+				return this;
+			}
+
+			// Can complete the move in this step
+			var speed = mobile.MovementSpeedForCell(self, self.Location);
+			if (delta.LengthSquared <= speed * speed)
+			{
+				mobile.SetVisualPosition(self, targetPos);
+				return NextActivity;
+			}
+
+			// Move towards the target
+			mobile.SetVisualPosition(self, currentPos + delta * speed / delta.Length);
+
+			return this;
+		}
+
+		protected override void OnLastRun(Actor self)
+		{
+			mobile.IsMoving = false;
+		}
+
+		public override IEnumerable<Target> GetTargets(Actor self)
+		{
+			yield return target;
+		}
+	}
+}

OpenRA.Mods.Common/Activities/PickupUnit.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System.Drawing;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
@@ -72,7 +73,8 @@ namespace OpenRA.Mods.Common.Activities
 			switch (state)
 			{
 				case PickupState.Intercept:
-					innerActivity = movement.MoveWithinRange(Target.FromActor(cargo), WDist.FromCells(4));
+					innerActivity = movement.MoveWithinRange(Target.FromActor(cargo), WDist.FromCells(4),
+						targetLineColor: Color.Yellow);
 					state = PickupState.LockCarryable;
 					return this;
 

OpenRA.Mods.Common/Activities/RepairBridge.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System.Drawing;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Traits;
 
@@ -16,49 +17,70 @@ namespace OpenRA.Mods.Common.Activities
 {
 	class RepairBridge : Enter
 	{
-		readonly Actor target;
-		readonly LegacyBridgeHut legacyHut;
-		readonly BridgeHut hut;
+		readonly EnterBehaviour enterBehaviour;
 		readonly string notification;
 
-		public RepairBridge(Actor self, Actor target, EnterBehaviour enterBehaviour, string notification)
-			: base(self, target, enterBehaviour)
+		Actor enterActor;
+		BridgeHut enterHut;
+		LegacyBridgeHut enterLegacyHut;
+
+		public RepairBridge(Actor self, Target target, EnterBehaviour enterBehaviour, string notification)
+			: base(self, target, Color.Yellow)
 		{
-			this.target = target;
-			legacyHut = target.TraitOrDefault<LegacyBridgeHut>();
-			hut = target.TraitOrDefault<BridgeHut>();
+			this.enterBehaviour = enterBehaviour;
 			this.notification = notification;
 		}
 
-		protected override bool CanReserve(Actor self)
+		bool CanEnterHut()
 		{
-			if (legacyHut != null)
-				return legacyHut.BridgeDamageState != DamageState.Undamaged && !legacyHut.Repairing && legacyHut.Bridge.GetHut(0) != null && legacyHut.Bridge.GetHut(1) != null;
+			if (enterLegacyHut != null)
+				return enterLegacyHut.BridgeDamageState != DamageState.Undamaged && !enterLegacyHut.Repairing &&
+					enterLegacyHut.Bridge.GetHut(0) != null && enterLegacyHut.Bridge.GetHut(1) != null;
 
-			if (hut != null)
-				return hut.BridgeDamageState != DamageState.Undamaged && !hut.Repairing;
+			if (enterHut != null)
+				return enterHut.BridgeDamageState != DamageState.Undamaged && !enterHut.Repairing;
 
 			return false;
 		}
 
-		protected override void OnInside(Actor self)
+		protected override bool TryStartEnter(Actor self, Actor targetActor)
 		{
-			if (legacyHut != null)
-			{
-				if (legacyHut.BridgeDamageState == DamageState.Undamaged || legacyHut.Repairing || legacyHut.Bridge.GetHut(0) == null || legacyHut.Bridge.GetHut(1) == null)
-					return;
+			enterActor = targetActor;
+			enterLegacyHut = enterActor.TraitOrDefault<LegacyBridgeHut>();
+			enterHut = enterActor.TraitOrDefault<BridgeHut>();
 
-				legacyHut.Repair(self);
-			}
-			else if (hut != null)
+			// Make sure we can still repair the target before entering
+			// (but not before, because this may stop the actor in the middle of nowhere)
+			if (!CanEnterHut())
 			{
-				if (hut.BridgeDamageState == DamageState.Undamaged || hut.Repairing)
-					return;
-
-				hut.Repair(target, self);
+				Cancel(self, true);
+				return false;
 			}
 
+			return true;
+		}
+
+		protected override void OnEnterComplete(Actor self, Actor targetActor)
+		{
+			// Make sure the target hasn't changed while entering
+			// OnEnterComplete is only called if targetActor is alive
+			if (targetActor != enterActor)
+				return;
+
+			if (!CanEnterHut())
+				return;
+
+			if (enterLegacyHut != null)
+				enterLegacyHut.Repair(self);
+			else if (enterHut != null)
+				enterHut.Repair(enterActor, self);
+
 			Game.Sound.PlayNotification(self.World.Map.Rules, self.Owner, "Speech", notification, self.Owner.Faction.InternalName);
+
+			if (enterBehaviour == EnterBehaviour.Dispose)
+				self.Dispose();
+			else if (enterBehaviour == EnterBehaviour.Suicide)
+				self.Kill(self);
 		}
 	}
 }

OpenRA.Mods.Common/Activities/RepairBuilding.cs

@@ -9,39 +9,66 @@
  */
 #endregion
 
+using System.Drawing;
 using OpenRA.Traits;
 
 namespace OpenRA.Mods.Common.Activities
 {
 	class RepairBuilding : Enter
 	{
-		readonly Actor target;
-		readonly IHealth health;
+		readonly EnterBehaviour enterBehaviour;
 		readonly Stance validStances;
 
-		public RepairBuilding(Actor self, Actor target, EnterBehaviour enterBehaviour, Stance validStances)
-			: base(self, target, enterBehaviour)
+		Actor enterActor;
+		IHealth enterHealth;
+
+		public RepairBuilding(Actor self, Target target, EnterBehaviour enterBehaviour, Stance validStances)
+			: base(self, target, Color.Yellow)
 		{
-			this.target = target;
+			this.enterBehaviour = enterBehaviour;
 			this.validStances = validStances;
-			health = target.Trait<IHealth>();
 		}
 
-		protected override bool CanReserve(Actor self)
+		protected override bool TryStartEnter(Actor self, Actor targetActor)
 		{
-			return health.DamageState != DamageState.Undamaged;
+			enterActor = targetActor;
+			enterHealth = targetActor.TraitOrDefault<IHealth>();
+
+			// Make sure we can still repair the target before entering
+			// (but not before, because this may stop the actor in the middle of nowhere)
+			var stance = self.Owner.Stances[enterActor.Owner];
+			if (enterHealth == null || enterHealth.DamageState == DamageState.Undamaged || !stance.HasStance(validStances))
+			{
+				Cancel(self, true);
+				return false;
+			}
+
+			return true;
 		}
 
-		protected override void OnInside(Actor self)
+		protected override void OnEnterComplete(Actor self, Actor targetActor)
 		{
-			var stance = self.Owner.Stances[target.Owner];
+			// Make sure the target hasn't changed while entering
+			// OnEnterComplete is only called if targetActor is alive
+			if (targetActor != enterActor)
+				return;
+
+			if (enterHealth.DamageState == DamageState.Undamaged)
+				return;
+
+			var stance = self.Owner.Stances[enterActor.Owner];
 			if (!stance.HasStance(validStances))
 				return;
 
-			if (health.DamageState == DamageState.Undamaged)
+			if (enterHealth.DamageState == DamageState.Undamaged)
 				return;
 
-			target.InflictDamage(self, new Damage(-health.MaxHP));
+			enterActor.InflictDamage(self, new Damage(-enterHealth.MaxHP));
+
+			if (enterBehaviour == EnterBehaviour.Dispose)
+				self.Dispose();
+			else if (enterBehaviour == EnterBehaviour.Suicide)
+				self.Kill(self);
 		}
 	}
 }

OpenRA.Mods.Common/Activities/Transform.cs

@@ -135,7 +135,7 @@ namespace OpenRA.Mods.Common.Activities
 				self.ReplacedByActor = a;
 
 				if (selected)
-					w.Selection.Add(w, a);
+					w.Selection.Add(a);
 
 				if (controlgroup.HasValue)
 					w.Selection.AddToControlGroup(a, controlgroup.Value);

OpenRA.Mods.Common/Activities/Turn.cs

@@ -61,7 +61,7 @@ namespace OpenRA.Mods.Common.Activities
 		protected override void OnLastRun(Actor self)
 		{
 			// If Mobile.IsMoving was set to 'true' earlier, we want to reset it to 'false' before the next tick.
-			if (mobile != null && mobile.IsMoving)
+			if (setIsMoving && mobile != null && mobile.IsMoving)
 				mobile.IsMoving = false;
 		}
 	}

OpenRA.Mods.Common/ActorExts.cs

@@ -59,42 +59,6 @@ namespace OpenRA.Mods.Common
 			return stance == Stance.Enemy;
 		}
 
-		/// <summary>
-		/// DEPRECATED: Write code that can handle FrozenActors correctly instead.
-		/// </summary>
-		public static Target ResolveFrozenActorOrder(this Actor self, Order order, Color targetLine)
-		{
-			// Not targeting a frozen actor
-			if (order.Target.Type != TargetType.FrozenActor)
-				return order.Target;
-
-			var frozen = order.Target.FrozenActor;
-
-			self.SetTargetLine(order.Target, targetLine, true);
-
-			// Target is still alive - resolve the real order
-			if (frozen.Actor != null && frozen.Actor.IsInWorld)
-				return Target.FromActor(frozen.Actor);
-
-			if (!order.Queued)
-				self.CancelActivity();
-
-			var move = self.TraitOrDefault<IMove>();
-			if (move != null)
-			{
-				// Move within sight range of the frozen actor
-				var range = self.TraitsImplementing<RevealsShroud>()
-					.Where(s => !s.IsTraitDisabled)
-					.Select(s => s.Range)
-					.Append(WDist.FromCells(2))
-					.Max();
-
-				self.QueueActivity(move.MoveWithinRange(Target.FromPos(frozen.CenterPosition), range));
-			}
-
-			return Target.Invalid;
-		}
-
 		public static void NotifyBlocker(this Actor self, IEnumerable<Actor> blockers)
 		{
 			foreach (var blocker in blockers)

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

@@ -103,6 +103,7 @@
     <Compile Include="Activities\Move\Move.cs" />
     <Compile Include="Activities\Move\MoveAdjacentTo.cs" />
     <Compile Include="Activities\Move\MoveWithinRange.cs" />
+    <Compile Include="Activities\Move\VisualMoveIntoTarget.cs" />
     <Compile Include="Activities\Parachute.cs" />
     <Compile Include="Activities\Rearm.cs" />
     <Compile Include="Activities\RemoveSelf.cs" />
@@ -120,6 +121,7 @@
     <Compile Include="Activities\WaitForTransport.cs" />
     <Compile Include="ActorExts.cs" />
     <Compile Include="AIUtils.cs" />
+    <Compile Include="TargetExtensions.cs" />
     <Compile Include="Traits\BotModules\Squads\AttackOrFleeFuzzy.cs" />
     <Compile Include="Traits\BotModules\BotModuleLogic\BaseBuilderQueueManager.cs" />
     <Compile Include="Traits\Player\ModularBot.cs" />
@@ -288,7 +290,6 @@
     <Compile Include="Traits\Attack\AttackFrontal.cs" />
     <Compile Include="Traits\Attack\AttackGarrisoned.cs" />
     <Compile Include="Traits\Attack\AttackOmni.cs" />
-    <Compile Include="Traits\Attack\AttackSuicides.cs" />
     <Compile Include="Traits\Attack\AttackTurreted.cs" />
     <Compile Include="Traits\AttackWander.cs" />
     <Compile Include="Traits\AutoTarget.cs" />
@@ -599,6 +600,7 @@
     <Compile Include="Traits\World\ActorSpawnManager.cs" />
     <Compile Include="Traits\ActorSpawner.cs" />
     <Compile Include="UpdateRules\Rules\20181215\RemoveAttackIgnoresVisibility.cs" />
+    <Compile Include="UpdateRules\Rules\20181215\RemoveAttackSuicides.cs" />
     <Compile Include="UpdateRules\Rules\20181215\RemovedDemolishLocking.cs" />
     <Compile Include="UpdateRules\Rules\20181215\RemoveNegativeDamageFullHealthCheck.cs" />
     <Compile Include="UpdateRules\Rules\20181215\RemoveResourceExplodeModifier.cs" />

OpenRA.Mods.Common/Scripting/Global/TriggerGlobal.cs

@@ -211,8 +211,27 @@ namespace OpenRA.Mods.Common.Scripting
 						return;
 
 					if (!group.Any())
-						using (f)
-							f.Call().Dispose();
+					{
+						// Functions can only be .Call()ed once, so operate on a copy so we can reuse it later
+						var temp = (LuaFunction)f.CopyReference();
+						using (temp)
+							temp.Call().Dispose();
+					}
+				}
+				catch (Exception e)
+				{
+					Context.FatalError(e.Message);
+				}
+			};
+
+			Action<Actor> onMemberAdded = m =>
+			{
+				try
+				{
+					if (!actors.Contains(m) || group.Contains(m))
+						return;
+
+					group.Add(m);
 				}
 				catch (Exception e)
 				{
@@ -221,7 +240,10 @@ namespace OpenRA.Mods.Common.Scripting
 			};
 
 			foreach (var a in group)
+			{
 				GetScriptTriggers(a).OnRemovedInternal += onMemberRemoved;
+				GetScriptTriggers(a).OnAddedInternal += onMemberAdded;
+			}
 		}
 
 		[Desc("Call a function when this actor is captured. The callback function " +

OpenRA.Mods.Common/Scripting/Properties/CaptureProperties.cs

@@ -35,7 +35,7 @@ namespace OpenRA.Mods.Common.Scripting
 			if (targetManager == null || !targetManager.CanBeTargetedBy(target, Self, captureManager))
 				throw new LuaException("Actor '{0}' cannot capture actor '{1}'!".F(Self, target));
 
-			Self.QueueActivity(new CaptureActor(Self, target));
+			Self.QueueActivity(new CaptureActor(Self, Target.FromActor(target)));
 		}
 	}
 }

OpenRA.Mods.Common/Scripting/Properties/DeliveryProperties.cs

@@ -33,8 +33,9 @@ namespace OpenRA.Mods.Common.Scripting
 		[Desc("Deliver cash to the target actor.")]
 		public void DeliverCash(Actor target)
 		{
-			Self.SetTargetLine(Target.FromActor(target), Color.Yellow);
-			Self.QueueActivity(new DonateCash(Self, target, info.Payload, info.PlayerExperience));
+			var t = Target.FromActor(target);
+			Self.SetTargetLine(t, Color.Yellow);
+			Self.QueueActivity(new DonateCash(Self, t, info.Payload, info.PlayerExperience));
 		}
 	}
 
@@ -64,8 +65,9 @@ namespace OpenRA.Mods.Common.Scripting
 
 			var level = gainsExperience.Level;
 
-			Self.SetTargetLine(Target.FromActor(target), Color.Yellow);
-			Self.QueueActivity(new DonateExperience(Self, target, level, deliversExperience.PlayerExperience, targetGainsExperience));
+			var t = Target.FromActor(target);
+			Self.SetTargetLine(t, Color.Yellow);
+			Self.QueueActivity(new DonateExperience(Self, t, level, deliversExperience.PlayerExperience));
 		}
 	}
 }

OpenRA.Mods.Common/Scripting/Properties/DemolitionProperties.cs

@@ -31,7 +31,7 @@ namespace OpenRA.Mods.Common.Scripting
 		[Desc("Demolish the target actor.")]
 		public void Demolish(Actor target)
 		{
-			Self.QueueActivity(new Demolish(Self, target, info.EnterBehaviour, info.DetonationDelay,
+			Self.QueueActivity(new Demolish(Self, Target.FromActor(target), info.EnterBehaviour, info.DetonationDelay,
 				info.Flashes, info.FlashesDelay, info.FlashInterval));
 		}
 	}

OpenRA.Mods.Common/Scripting/Properties/MobileProperties.cs

@@ -60,7 +60,7 @@ namespace OpenRA.Mods.Common.Scripting
 		[Desc("Move to and enter the transport.")]
 		public void EnterTransport(Actor transport)
 		{
-			Self.QueueActivity(new EnterTransport(Self, transport, 1, false));
+			Self.QueueActivity(new EnterTransport(Self, Target.FromActor(transport)));
 		}
 
 		[Desc("Whether the actor can move (false if immobilized).")]

OpenRA.Mods.Common/Scripting/ScriptTriggers.cs

@@ -43,6 +43,7 @@ namespace OpenRA.Mods.Common.Scripting
 		public event Action<Actor> OnKilledInternal = _ => { };
 		public event Action<Actor> OnCapturedInternal = _ => { };
 		public event Action<Actor> OnRemovedInternal = _ => { };
+		public event Action<Actor> OnAddedInternal = _ => { };
 		public event Action<Actor, Actor> OnProducedInternal = (a, b) => { };
 		public event Action<Actor, Actor> OnOtherProducedInternal = (a, b) => { };
 
@@ -340,6 +341,9 @@ namespace OpenRA.Mods.Common.Scripting
 					return;
 				}
 			}
+
+			// Run any internally bound callbacks
+			OnAddedInternal(self);
 		}
 
 		void INotifyRemovedFromWorld.RemovedFromWorld(Actor self)

OpenRA.Mods.Common/ServerTraits/LobbyCommands.cs

@@ -654,6 +654,7 @@ namespace OpenRA.Mods.Common.Server
 			targetClient.SpawnPoint = 0;
 			targetClient.Team = 0;
 			targetClient.Color = HSLColor.FromRGB(255, 255, 255);
+			targetClient.State = Session.ClientState.NotReady;
 			server.SendMessage("{0} moved {1} to spectators.".F(client.Name, targetClient.Name));
 			Log.Write("server", "{0} moved {1} to spectators.".F(client.Name, targetClient.Name));
 			server.SyncLobbyClients();

OpenRA.Mods.Common/TargetExtensions.cs

@@ -0,0 +1,79 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2019 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 OpenRA.Traits;
+
+namespace OpenRA.Mods.Common
+{
+	public static class TargetExtensions
+	{
+		/// <summary>
+		/// Update (Frozen)Actor targets to account for visibility changes or actor replacement.
+		/// If the target actor becomes hidden without a FrozenActor, the target is invalidated.
+		/// /// </summary>
+		public static Target RecalculateInvalidatingHiddenTargets(this Target t, Player viewer)
+		{
+			bool targetIsHiddenActor;
+			var updated = t.Recalculate(viewer, out targetIsHiddenActor);
+			return targetIsHiddenActor ? Target.Invalid : updated;
+		}
+
+		/// <summary>
+		/// Update (Frozen)Actor targets to account for visibility changes or actor replacement.
+		/// If the target actor becomes hidden without a FrozenActor, the target actor is kept
+		/// and the actorHidden flag is set to true.
+		/// </summary>
+		public static Target Recalculate(this Target t, Player viewer, out bool targetIsHiddenActor)
+		{
+			targetIsHiddenActor = false;
+
+			// Check whether the target has transformed into something else
+			// HACK: This relies on knowing the internal implementation details of Target
+			if (t.Type == TargetType.Invalid && t.Actor != null && t.Actor.ReplacedByActor != null)
+				t = Target.FromActor(t.Actor.ReplacedByActor);
+
+			// Bot-controlled units aren't yet capable of understanding visibility changes
+			if (viewer.IsBot)
+				return t;
+
+			if (t.Type == TargetType.Actor)
+			{
+				// Actor has been hidden under the fog
+				if (!t.Actor.CanBeViewedByPlayer(viewer))
+				{
+					// Replace with FrozenActor if applicable, otherwise return target unmodified
+					var frozen = viewer.FrozenActorLayer.FromID(t.Actor.ActorID);
+					if (frozen != null)
+						return Target.FromFrozenActor(frozen);
+
+					targetIsHiddenActor = true;
+					return t;
+				}
+			}
+			else if (t.Type == TargetType.FrozenActor)
+			{
+				// Frozen actor has been revealed
+				if (!t.FrozenActor.Visible || !t.FrozenActor.IsValid)
+				{
+					// Original actor is still alive
+					if (t.FrozenActor.Actor != null && t.FrozenActor.Actor.CanBeViewedByPlayer(viewer))
+						return Target.FromActor(t.FrozenActor.Actor);
+
+					// Original actor was killed while hidden
+					if (t.Actor == null)
+						return Target.Invalid;
+				}
+			}
+
+			return t;
+		}
+	}
+}

OpenRA.Mods.Common/Traits/Air/Aircraft.cs

@@ -174,6 +174,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		RepairableInfo repairableInfo;
 		RearmableInfo rearmableInfo;
+		AttackMove attackMove;
 		ConditionManager conditionManager;
 		IDisposable reservation;
 		IEnumerable<int> speedModifiers;
@@ -231,6 +232,7 @@ namespace OpenRA.Mods.Common.Traits
 		{
 			repairableInfo = self.Info.TraitInfoOrDefault<RepairableInfo>();
 			rearmableInfo = self.Info.TraitInfoOrDefault<RearmableInfo>();
+			attackMove = self.TraitOrDefault<AttackMove>();
 			conditionManager = self.TraitOrDefault<ConditionManager>();
 			speedModifiers = self.TraitsImplementing<ISpeedModifier>().ToArray().Select(sm => sm.GetSpeedModifier());
 			cachedPosition = self.CenterPosition;
@@ -522,7 +524,12 @@ namespace OpenRA.Mods.Common.Traits
 
 		void INotifyBecomingIdle.OnBecomingIdle(Actor self)
 		{
-			OnBecomingIdle(self);
+			// HACK: Work around AttackMove relying on INotifyIdle.TickIdle to continue its path
+			// AttackMoveActivity needs to be rewritten to use child activities instead!
+			if (attackMove != null && attackMove.TargetLocation.HasValue)
+				((INotifyIdle)attackMove).TickIdle(self);
+			else
+				OnBecomingIdle(self);
 		}
 
 		protected virtual void OnBecomingIdle(Actor self)
@@ -605,28 +612,35 @@ namespace OpenRA.Mods.Common.Traits
 			return new HeliFly(self, Target.FromCell(self.World, cell));
 		}
 
-		public Activity MoveWithinRange(Target target, WDist range)
+		public Activity MoveWithinRange(Target target, WDist range,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
 		{
 			if (!Info.CanHover)
-				return new Fly(self, target, WDist.Zero, range);
+				return new Fly(self, target, WDist.Zero, range, initialTargetPosition, targetLineColor);
 
-			return new HeliFly(self, target, WDist.Zero, range);
+			return new HeliFly(self, target, WDist.Zero, range, initialTargetPosition, targetLineColor);
 		}
 
-		public Activity MoveWithinRange(Target target, WDist minRange, WDist maxRange)
+		public Activity MoveWithinRange(Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
 		{
 			if (!Info.CanHover)
-				return new Fly(self, target, minRange, maxRange);
+				return new Fly(self, target, minRange, maxRange,
+					initialTargetPosition, targetLineColor);
 
-			return new HeliFly(self, target, minRange, maxRange);
+			return new HeliFly(self, target, minRange, maxRange,
+				initialTargetPosition, targetLineColor);
 		}
 
-		public Activity MoveFollow(Actor self, Target target, WDist minRange, WDist maxRange)
+		public Activity MoveFollow(Actor self, Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
 		{
 			if (!Info.CanHover)
-				return new FlyFollow(self, target, minRange, maxRange);
+				return new FlyFollow(self, target, minRange, maxRange,
+					initialTargetPosition, targetLineColor);
 
-			return new Follow(self, target, minRange, maxRange);
+			return new Follow(self, target, minRange, maxRange,
+				initialTargetPosition, targetLineColor);
 		}
 
 		public Activity MoveIntoWorld(Actor self, CPos cell, SubCell subCell = SubCell.Any)
@@ -637,12 +651,16 @@ namespace OpenRA.Mods.Common.Traits
 			return new HeliFly(self, Target.FromCell(self.World, cell, subCell));
 		}
 
-		public Activity MoveToTarget(Actor self, Target target)
+		public Activity MoveToTarget(Actor self, Target target,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
 		{
 			if (!Info.CanHover)
-				return new Fly(self, target, WDist.FromCells(3), WDist.FromCells(5));
+				return new Fly(self, target, WDist.FromCells(3), WDist.FromCells(5),
+					initialTargetPosition, targetLineColor);
 
-			return ActivityUtils.SequenceActivities(new HeliFly(self, target), new Turn(self, Info.InitialFacing));
+			return ActivityUtils.SequenceActivities(
+				new HeliFly(self, target, initialTargetPosition, targetLineColor),
+				new Turn(self, Info.InitialFacing));
 		}
 
 		public Activity MoveIntoTarget(Actor self, Target target)

OpenRA.Mods.Common/Traits/Attack/AttackBase.cs

@@ -34,6 +34,9 @@ namespace OpenRA.Mods.Common.Traits
 		[Desc("Allow firing into the fog to target frozen actors without requiring force-fire.")]
 		public readonly bool TargetFrozenActors = false;
 
+		[Desc("Force-fire mode ignores actors and targets the ground instead.")]
+		public readonly bool ForceFireIgnoresActors = false;
+
 		[VoiceReference] public readonly string Voice = "Action";
 
 		public override abstract object Create(ActorInitializer init);
@@ -139,8 +142,7 @@ namespace OpenRA.Mods.Common.Traits
 				if (armament == null)
 					yield break;
 
-				var negativeDamage = (armament.Weapon.Warheads.FirstOrDefault(w => (w is DamageWarhead)) as DamageWarhead).Damage < 0;
-				yield return new AttackOrderTargeter(this, 6, negativeDamage);
+				yield return new AttackOrderTargeter(this, 6);
 			}
 		}
 
@@ -358,8 +360,11 @@ namespace OpenRA.Mods.Common.Traits
 				self.CancelActivity();
 
 			self.QueueActivity(GetAttackActivity(self, target, allowMove, forceAttack));
+			OnQueueAttackActivity(self, target, queued, allowMove, forceAttack);
 		}
 
+		public virtual void OnQueueAttackActivity(Actor self, Target target, bool queued, bool allowMove, bool forceAttack) { }
+
 		public bool IsReachableTarget(Target target, bool allowMove)
 		{
 			return HasAnyValidWeapons(target)
@@ -381,7 +386,7 @@ namespace OpenRA.Mods.Common.Traits
 		{
 			readonly AttackBase ab;
 
-			public AttackOrderTargeter(AttackBase ab, int priority, bool negativeDamage)
+			public AttackOrderTargeter(AttackBase ab, int priority)
 			{
 				this.ab = ab;
 				OrderID = ab.attackOrderName;
@@ -399,6 +404,9 @@ namespace OpenRA.Mods.Common.Traits
 				if (modifiers.HasModifier(TargetModifiers.ForceMove))
 					return false;
 
+				if (ab.Info.ForceFireIgnoresActors && modifiers.HasModifier(TargetModifiers.ForceAttack))
+					return false;
+
 				// Disguised actors are revealed by the attack cursor
 				// HACK: works around limitations in the targeting code that force the
 				// targeting and attacking logic (which should be logically separate)

OpenRA.Mods.Common/Traits/Attack/AttackFollow.cs

@@ -10,9 +10,9 @@
 #endregion
 
 using System;
+using System.Drawing;
 using System.Linq;
 using OpenRA.Activities;
-using OpenRA.Mods.Common.Activities;
 using OpenRA.Traits;
 
 namespace OpenRA.Mods.Common.Traits
@@ -20,27 +20,92 @@ namespace OpenRA.Mods.Common.Traits
 	[Desc("Actor will follow units until in range to attack them.")]
 	public class AttackFollowInfo : AttackBaseInfo
 	{
+		[Desc("Automatically acquire and fire on targets of opportunity when not actively attacking.")]
+		public readonly bool OpportunityFire = true;
+
 		public override object Create(ActorInitializer init) { return new AttackFollow(init.Self, this); }
 	}
 
 	public class AttackFollow : AttackBase, INotifyOwnerChanged
 	{
-		public Target Target { get; protected set; }
+		protected Target requestedTarget;
+		protected bool requestedForceAttack;
+		protected int requestedTargetLastTick;
+		protected Target opportunityTarget;
+		protected bool opportunityForceAttack;
+		Mobile mobile;
+		AutoTarget autoTarget;
 
 		public AttackFollow(Actor self, AttackFollowInfo info)
 			: base(self, info) { }
 
+		protected override void Created(Actor self)
+		{
+			mobile = self.TraitOrDefault<Mobile>();
+			autoTarget = self.TraitOrDefault<AutoTarget>();
+			base.Created(self);
+		}
+
+		protected bool CanAimAtTarget(Actor self, Target target, bool forceAttack)
+		{
+			if (target.Type == TargetType.Actor && !target.Actor.CanBeViewedByPlayer(self.Owner))
+				return false;
+
+			if (target.Type == TargetType.FrozenActor && !target.FrozenActor.IsValid)
+				return false;
+
+			var pos = self.CenterPosition;
+			var armaments = ChooseArmamentsForTarget(target, forceAttack);
+			foreach (var a in armaments)
+				if (target.IsInRange(pos, a.MaxRange()) && (a.Weapon.MinRange == WDist.Zero || !target.IsInRange(pos, a.Weapon.MinRange)))
+					return true;
+
+			return false;
+		}
+
 		protected override void Tick(Actor self)
 		{
-			Target = Target.Recalculate(self.Owner);
 			if (IsTraitDisabled)
+				requestedTarget = opportunityTarget = Target.Invalid;
+
+			if (requestedTargetLastTick != self.World.WorldTick)
 			{
-				Target = Target.Invalid;
-				return;
+				// Activities tick before traits, so if we are here it means the activity didn't run
+				// (either queued next or already cancelled) and we need to recalculate the target ourself
+				bool targetIsHiddenActor;
+				requestedTarget = requestedTarget.Recalculate(self.Owner, out targetIsHiddenActor);
 			}
 
-			DoAttack(self, Target);
-			IsAiming = Target.IsValidFor(self);
+			// Can't fire on anything
+			if (mobile != null && !mobile.CanInteractWithGroundLayer(self))
+				return;
+
+			if (requestedTarget.Type != TargetType.Invalid)
+			{
+				IsAiming = CanAimAtTarget(self, requestedTarget, requestedForceAttack);
+				if (IsAiming)
+					DoAttack(self, requestedTarget);
+			}
+			else
+			{
+				IsAiming = false;
+
+				if (opportunityTarget.Type != TargetType.Invalid)
+					IsAiming = CanAimAtTarget(self, opportunityTarget, opportunityForceAttack);
+
+				if (!IsAiming && ((AttackFollowInfo)Info).OpportunityFire && autoTarget != null &&
+				    !autoTarget.IsTraitDisabled && autoTarget.Stance >= UnitStance.Defend)
+				{
+					opportunityTarget = autoTarget.ScanForTarget(self, false);
+					opportunityForceAttack = false;
+
+					if (opportunityTarget.Type != TargetType.Invalid)
+						IsAiming = CanAimAtTarget(self, opportunityTarget, opportunityForceAttack);
+				}
+
+				if (IsAiming)
+					DoAttack(self, opportunityTarget);
+			}
 
 			base.Tick(self);
 		}
@@ -50,15 +115,28 @@ namespace OpenRA.Mods.Common.Traits
 			return new AttackActivity(self, newTarget, allowMove, forceAttack);
 		}
 
+		public override void OnQueueAttackActivity(Actor self, Target target, bool queued, bool allowMove, bool forceAttack)
+		{
+			// If not queued we know that the attack activity will run next
+			// We can improve responsiveness for turreted actors by preempting
+			// the last order (usually a move) and set the target immediately
+			if (!queued)
+			{
+				requestedTarget = target;
+				requestedForceAttack = forceAttack;
+				requestedTargetLastTick = self.World.WorldTick;
+			}
+		}
+
 		public override void OnStopOrder(Actor self)
 		{
-			Target = Target.Invalid;
+			requestedTarget = opportunityTarget = Target.Invalid;
 			base.OnStopOrder(self);
 		}
 
-		public void OnOwnerChanged(Actor self, Player oldOwner, Player newOwner)
+		void INotifyOwnerChanged.OnOwnerChanged(Actor self, Player oldOwner, Player newOwner)
 		{
-			Target = Target.Invalid;
+			requestedTarget = opportunityTarget = Target.Invalid;
 		}
 
 		class AttackActivity : Activity
@@ -67,7 +145,13 @@ namespace OpenRA.Mods.Common.Traits
 			readonly RevealsShroud[] revealsShroud;
 			readonly IMove move;
 			readonly bool forceAttack;
+
 			Target target;
+			Target lastVisibleTarget;
+			bool useLastVisibleTarget;
+			WDist lastVisibleMaximumRange;
+			WDist lastVisibleMinimumRange;
+			bool wasMovingWithinRange;
 			bool hasTicked;
 
 			public AttackActivity(Actor self, Target target, bool allowMove, bool forceAttack)
@@ -78,59 +162,122 @@ namespace OpenRA.Mods.Common.Traits
 
 				this.target = target;
 				this.forceAttack = forceAttack;
+
+				// The target may become hidden between the initial order request and the first tick (e.g. if queued)
+				// Moving to any position (even if quite stale) is still better than immediately giving up
+				if ((target.Type == TargetType.Actor && target.Actor.CanBeViewedByPlayer(self.Owner))
+				    || target.Type == TargetType.FrozenActor || target.Type == TargetType.Terrain)
+				{
+					lastVisibleTarget = Target.FromPos(target.CenterPosition);
+					lastVisibleMaximumRange = attack.GetMaximumRangeVersusTarget(target);
+					lastVisibleMinimumRange = attack.GetMinimumRangeVersusTarget(target);
+				}
 			}
 
 			public override Activity Tick(Actor self)
 			{
-				target = target.Recalculate(self.Owner);
-				if (IsCanceled || !target.IsValidFor(self))
+				if (IsCanceled)
+				{
+					// Cancel the requested target, but keep firing on it while in range
+					attack.opportunityTarget = attack.requestedTarget;
+					attack.opportunityForceAttack = attack.requestedForceAttack;
+					attack.requestedTarget = Target.Invalid;
+					return NextActivity;
+				}
+
+				// Check that AttackFollow hasn't cancelled the target by modifying attack.Target
+				// Having both this and AttackFollow modify that field is a horrible hack.
+				if (hasTicked && attack.requestedTarget.Type == TargetType.Invalid)
 					return NextActivity;
 
 				if (attack.IsTraitPaused)
 					return this;
 
-				var weapon = attack.ChooseArmamentsForTarget(target, forceAttack).FirstOrDefault();
-				if (weapon != null)
+				bool targetIsHiddenActor;
+				attack.requestedForceAttack = forceAttack;
+				attack.requestedTarget = target = target.Recalculate(self.Owner, out targetIsHiddenActor);
+				attack.requestedTargetLastTick = self.World.WorldTick;
+				hasTicked = true;
+
+				if (!targetIsHiddenActor && target.Type == TargetType.Actor)
 				{
-					// Check that AttackFollow hasn't cancelled the target by modifying attack.Target
-					// Having both this and AttackFollow modify that field is a horrible hack.
-					if (hasTicked && attack.Target.Type == TargetType.Invalid)
-						return NextActivity;
+					lastVisibleTarget = Target.FromTargetPositions(target);
+					lastVisibleMaximumRange = attack.GetMaximumRangeVersusTarget(target);
+					lastVisibleMinimumRange = attack.GetMinimumRange();
 
-					var targetIsMobile = (target.Type == TargetType.Actor && target.Actor.Info.HasTraitInfo<IMoveInfo>())
-						|| (target.Type == TargetType.FrozenActor && target.FrozenActor.Info.HasTraitInfo<IMoveInfo>());
-
-					// Try and sit at least one cell closer than the max range to give some leeway if the target starts moving.
-					var modifiedRange = weapon.MaxRange();
-					var maxRange = targetIsMobile ? new WDist(Math.Max(weapon.Weapon.MinRange.Length, modifiedRange.Length - 1024))
-						: modifiedRange;
-
-					// Most actors want to be able to see their target before shooting
-					if (!attack.Info.TargetFrozenActors && !forceAttack && target.Type == TargetType.FrozenActor)
+					// Try and sit at least one cell away from the min or max ranges to give some leeway if the target starts moving.
+					if (move != null && target.Actor.Info.HasTraitInfo<IMoveInfo>())
 					{
-						var rs = revealsShroud
-							.Where(Exts.IsTraitEnabled)
-							.MaxByOrDefault(s => s.Range);
-
-						// Default to 2 cells if there are no active traits
-						var sightRange = rs != null ? rs.Range : WDist.FromCells(2);
-						if (sightRange < maxRange)
-							maxRange = sightRange;
+						var preferMinRange = Math.Min(lastVisibleMinimumRange.Length + 1024, lastVisibleMaximumRange.Length);
+						var preferMaxRange = Math.Max(lastVisibleMaximumRange.Length - 1024, lastVisibleMinimumRange.Length);
+						lastVisibleMaximumRange = new WDist((lastVisibleMaximumRange.Length - 1024).Clamp(preferMinRange, preferMaxRange));
 					}
-
-					attack.Target = target;
-					hasTicked = true;
-
-					if (move != null)
-						return ActivityUtils.SequenceActivities(move.MoveFollow(self, target, weapon.Weapon.MinRange, maxRange), this);
-					if (target.IsInRange(self.CenterPosition, weapon.MaxRange()) &&
-						!target.IsInRange(self.CenterPosition, weapon.Weapon.MinRange))
-						return this;
 				}
 
-				attack.Target = Target.Invalid;
+				var oldUseLastVisibleTarget = useLastVisibleTarget;
+				var maxRange = lastVisibleMaximumRange;
+				var minRange = lastVisibleMinimumRange;
+				useLastVisibleTarget = targetIsHiddenActor || !target.IsValidFor(self);
 
-				return NextActivity;
+				// Most actors want to be able to see their target before shooting
+				if (target.Type == TargetType.FrozenActor && !attack.Info.TargetFrozenActors && !forceAttack)
+				{
+					var rs = revealsShroud
+						.Where(Exts.IsTraitEnabled)
+						.MaxByOrDefault(s => s.Range);
+
+					// Default to 2 cells if there are no active traits
+					var sightRange = rs != null ? rs.Range : WDist.FromCells(2);
+					if (sightRange < maxRange)
+						maxRange = sightRange;
+				}
+
+				// If we are ticking again after previously sequencing a MoveWithRange then that move must have completed
+				// Either we are in range and can see the target, or we've lost track of it and should give up
+				if (wasMovingWithinRange && targetIsHiddenActor)
+				{
+					attack.requestedTarget = Target.Invalid;
+					return NextActivity;
+				}
+
+				// Update target lines if required
+				if (useLastVisibleTarget != oldUseLastVisibleTarget)
+					self.SetTargetLine(useLastVisibleTarget ? lastVisibleTarget : target, Color.Red, false);
+
+				// Target is hidden or dead, and we don't have a fallback position to move towards
+				if (useLastVisibleTarget && !lastVisibleTarget.IsValidFor(self))
+				{
+					attack.requestedTarget = Target.Invalid;
+					return NextActivity;
+				}
+
+				var pos = self.CenterPosition;
+				var checkTarget = useLastVisibleTarget ? lastVisibleTarget : target;
+
+				// We've reached the required range - if the target is visible and valid then we wait
+				// otherwise if it is hidden or dead we give up
+				if (checkTarget.IsInRange(pos, maxRange) && !checkTarget.IsInRange(pos, minRange))
+				{
+					if (useLastVisibleTarget)
+					{
+						attack.requestedTarget = Target.Invalid;
+						return NextActivity;
+					}
+
+					return this;
+				}
+
+				// We can't move into range, so give up
+				if (move == null || maxRange == WDist.Zero || maxRange < minRange)
+				{
+					attack.requestedTarget = Target.Invalid;
+					return NextActivity;
+				}
+
+				wasMovingWithinRange = true;
+				return ActivityUtils.SequenceActivities(
+					move.MoveWithinRange(target, minRange, maxRange, checkTarget.CenterPosition, Color.Red),
+					this);
 			}
 		}
 	}

OpenRA.Mods.Common/Traits/Attack/AttackOmni.cs

@@ -46,7 +46,9 @@ namespace OpenRA.Mods.Common.Traits
 
 			public override Activity Tick(Actor self)
 			{
-				target = target.Recalculate(self.Owner);
+				// This activity can't move to reacquire hidden targets, so use the
+				// Recalculate overload that invalidates hidden targets.
+				target = target.RecalculateInvalidatingHiddenTargets(self.Owner);
 				if (IsCanceled || !target.IsValidFor(self) || !attack.IsReachableTarget(target, allowMove))
 					return NextActivity;
 

OpenRA.Mods.Common/Traits/Attack/AttackSuicides.cs

@@ -1,98 +0,0 @@
-#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.Collections.Generic;
-using System.Drawing;
-using OpenRA.Activities;
-using OpenRA.Mods.Common.Orders;
-using OpenRA.Primitives;
-using OpenRA.Traits;
-
-namespace OpenRA.Mods.Common.Traits
-{
-	[Desc("Does a suicide attack where it moves next to the target when used in combination with `Explodes`.")]
-	class AttackSuicidesInfo : ConditionalTraitInfo, Requires<IMoveInfo>
-	{
-		[Desc("Types defined by `Targetable:` trait that this actor can target.")]
-		public readonly BitSet<TargetableType> TargetTypes = new BitSet<TargetableType>("DetonateAttack");
-
-		[Desc("Types of damage that this trait causes to self while suiciding. Leave empty for no damage types.")]
-		public readonly BitSet<DamageType> DamageTypes = default(BitSet<DamageType>);
-
-		[VoiceReference] public readonly string Voice = "Action";
-
-		public override object Create(ActorInitializer init) { return new AttackSuicides(init.Self, this); }
-	}
-
-	class AttackSuicides : ConditionalTrait<AttackSuicidesInfo>, IIssueOrder, IResolveOrder, IOrderVoice, IIssueDeployOrder
-	{
-		readonly IMove move;
-
-		public AttackSuicides(Actor self, AttackSuicidesInfo info)
-			: base(info)
-		{
-			move = self.Trait<IMove>();
-		}
-
-		public IEnumerable<IOrderTargeter> Orders
-		{
-			get
-			{
-				if (IsTraitDisabled)
-					yield break;
-
-				yield return new TargetTypeOrderTargeter(Info.TargetTypes, "DetonateAttack", 5, "attack", true, false) { ForceAttack = false };
-				yield return new DeployOrderTargeter("Detonate", 5);
-			}
-		}
-
-		public Order IssueOrder(Actor self, IOrderTargeter order, Target target, bool queued)
-		{
-			if (order.OrderID != "DetonateAttack" && order.OrderID != "Detonate")
-				return null;
-
-			return new Order(order.OrderID, self, target, queued);
-		}
-
-		Order IIssueDeployOrder.IssueDeployOrder(Actor self, bool queued)
-		{
-			return new Order("Detonate", self, queued);
-		}
-
-		bool IIssueDeployOrder.CanIssueDeployOrder(Actor self) { return true; }
-
-		public string VoicePhraseForOrder(Actor self, Order order)
-		{
-			return Info.Voice;
-		}
-
-		public void ResolveOrder(Actor self, Order order)
-		{
-			if (order.OrderString == "DetonateAttack")
-			{
-				var target = self.ResolveFrozenActorOrder(order, Color.Red);
-				if (target.Type != TargetType.Actor)
-					return;
-
-				if (!order.Queued)
-					self.CancelActivity();
-
-				self.SetTargetLine(target, Color.Red);
-
-				self.QueueActivity(move.MoveToTarget(self, target));
-
-				self.QueueActivity(new CallFunc(() => self.Kill(self, Info.DamageTypes)));
-			}
-			else if (order.OrderString == "Detonate")
-				self.Kill(self, Info.DamageTypes);
-		}
-	}
-}

OpenRA.Mods.Common/Traits/AutoTarget.cs

@@ -109,10 +109,9 @@ namespace OpenRA.Mods.Common.Traits
 		}
 	}
 
-	public class AutoTarget : ConditionalTrait<AutoTargetInfo>, INotifyIdle, INotifyDamage, ITick, IResolveOrder, ISync, INotifyCreated
+	public class AutoTarget : ConditionalTrait<AutoTargetInfo>, INotifyIdle, INotifyDamage, ITick, IResolveOrder, ISync, INotifyCreated, INotifyOwnerChanged
 	{
 		readonly IEnumerable<AttackBase> activeAttackBases;
-		readonly AttackFollow[] attackFollows;
 		[Sync] int nextScanTime = 0;
 
 		public UnitStance Stance { get { return stance; } }
@@ -161,7 +160,6 @@ namespace OpenRA.Mods.Common.Traits
 				stance = self.Owner.IsBot || !self.Owner.Playable ? info.InitialStanceAI : info.InitialStance;
 
 			PredictedStance = stance;
-			attackFollows = self.TraitsImplementing<AttackFollow>().ToArray();
 		}
 
 		void INotifyCreated.Created(Actor self)
@@ -177,6 +175,12 @@ namespace OpenRA.Mods.Common.Traits
 			ApplyStanceCondition(self);
 		}
 
+		void INotifyOwnerChanged.OnOwnerChanged(Actor self, Player oldOwner, Player newOwner)
+		{
+			PredictedStance = self.Owner.IsBot || !self.Owner.Playable ? Info.InitialStanceAI : Info.InitialStance;
+			SetStance(self, PredictedStance);
+		}
+
 		void IResolveOrder.ResolveOrder(Actor self, Order order)
 		{
 			if (order.OrderString == "SetUnitStance" && Info.EnableStances)
@@ -215,9 +219,8 @@ namespace OpenRA.Mods.Common.Traits
 
 			Aggressor = attacker;
 
-			bool allowMove;
-			if (ShouldAttack(out allowMove))
-				Attack(self, Target.FromActor(Aggressor), allowMove);
+			var allowMove = Info.AllowMovement && Stance > UnitStance.Defend;
+			Attack(self, Target.FromActor(Aggressor), allowMove);
 		}
 
 		void INotifyIdle.TickIdle(Actor self)
@@ -225,21 +228,8 @@ namespace OpenRA.Mods.Common.Traits
 			if (IsTraitDisabled || Stance < UnitStance.Defend)
 				return;
 
-			bool allowMove;
-			if (ShouldAttack(out allowMove))
-				ScanAndAttack(self, allowMove);
-		}
-
-		bool ShouldAttack(out bool allowMove)
-		{
-			allowMove = Info.AllowMovement && Stance > UnitStance.Defend;
-
-			// PERF: Avoid LINQ.
-			foreach (var attackFollow in attackFollows)
-				if (!attackFollow.IsTraitDisabled && attackFollow.IsReachableTarget(attackFollow.Target, allowMove))
-					return false;
-
-			return true;
+			var allowMove = Info.AllowMovement && Stance > UnitStance.Defend;
+			ScanAndAttack(self, allowMove);
 		}
 
 		void ITick.Tick(Actor self)

OpenRA.Mods.Common/Traits/BotModules/BuildingRepairBotModule.cs

@@ -26,6 +26,12 @@ namespace OpenRA.Mods.Common.Traits
 
 		void IBotRespondToAttack.RespondToAttack(IBot bot, Actor self, AttackInfo e)
 		{
+			// HACK: We don't want D2k bots to repair all their buildings on placement
+			// where half their HP is removed via neutral terrain damage.
+			// TODO: Implement concrete placement for D2k bots and remove this hack.
+			if (e.Attacker.Owner.Stances[self.Owner] == Stance.Neutral)
+				return;
+
 			var rb = self.TraitOrDefault<RepairableBuilding>();
 			if (rb != null)
 			{

OpenRA.Mods.Common/Traits/BotModules/CaptureManagerBotModule.cs

@@ -48,7 +48,7 @@ namespace OpenRA.Mods.Common.Traits
 		readonly World world;
 		readonly Player player;
 		readonly Func<Actor, bool> isEnemyUnit;
-		readonly Predicate<Actor> unitCannotBeOrdered;
+		readonly Predicate<Actor> unitCannotBeOrderedOrIsIdle;
 		readonly int maximumCaptureTargetOptions;
 		int minCaptureDelayTicks;
 
@@ -69,7 +69,7 @@ namespace OpenRA.Mods.Common.Traits
 					&& !unit.Info.HasTraitInfo<HuskInfo>()
 					&& unit.Info.HasTraitInfo<ITargetableInfo>();
 
-			unitCannotBeOrdered = a => a.Owner != player || a.IsDead || !a.IsInWorld;
+			unitCannotBeOrderedOrIsIdle = a => a.Owner != player || a.IsDead || !a.IsInWorld || a.IsIdle;
 
 			maximumCaptureTargetOptions = Math.Max(1, Info.MaximumCaptureTargetOptions);
 		}
@@ -118,13 +118,13 @@ namespace OpenRA.Mods.Common.Traits
 			if (!Info.CapturingActorTypes.Any() || player.WinState != WinState.Undefined)
 				return;
 
-			activeCapturers.RemoveAll(unitCannotBeOrdered);
+			activeCapturers.RemoveAll(unitCannotBeOrderedOrIsIdle);
 
 			var newUnits = world.ActorsHavingTrait<IPositionable>()
 				.Where(a => a.Owner == player && !activeCapturers.Contains(a));
 
 			var capturers = newUnits
-				.Where(a => a.IsIdle && Info.CapturingActorTypes.Contains(a.Info.Name))
+				.Where(a => a.IsIdle && Info.CapturingActorTypes.Contains(a.Info.Name) && a.Info.HasTraitInfo<CapturesInfo>())
 				.Select(a => new TraitPair<CaptureManager>(a, a.TraitOrDefault<CaptureManager>()))
 				.Where(tp => tp.Trait != null)
 				.ToArray();
@@ -140,52 +140,33 @@ namespace OpenRA.Mods.Common.Traits
 				: GetActorsThatCanBeOrderedByPlayer(randPlayer);
 
 			var capturableTargetOptions = targetOptions
-				.Select(a => new CaptureTarget<CapturableInfo>(a, "CaptureActor"))
 				.Where(target =>
 				{
-					if (target.Info == null)
-						return false;
-
-					var captureManager = target.Actor.TraitOrDefault<CaptureManager>();
+					var captureManager = target.TraitOrDefault<CaptureManager>();
 					if (captureManager == null)
 						return false;
 
-					return capturers.Any(tp => captureManager.CanBeTargetedBy(target.Actor, tp.Actor, tp.Trait));
+					return capturers.Any(tp => captureManager.CanBeTargetedBy(target, tp.Actor, tp.Trait));
 				})
-				.OrderByDescending(target => target.Actor.GetSellValue())
+				.OrderByDescending(target => target.GetSellValue())
 				.Take(maximumCaptureTargetOptions);
 
 			if (Info.CapturableActorTypes.Any())
-				capturableTargetOptions = capturableTargetOptions.Where(target => Info.CapturableActorTypes.Contains(target.Actor.Info.Name.ToLowerInvariant()));
+				capturableTargetOptions = capturableTargetOptions.Where(target => Info.CapturableActorTypes.Contains(target.Info.Name.ToLowerInvariant()));
 
 			if (!capturableTargetOptions.Any())
 				return;
 
-			var capturesCapturers = capturers.Where(tp => tp.Actor.Info.HasTraitInfo<CapturesInfo>());
-			foreach (var tp in capturesCapturers)
-				QueueCaptureOrderFor(bot, tp.Actor, GetCapturerTargetClosestToOrDefault(tp.Actor, capturableTargetOptions));
-		}
+			foreach (var capturer in capturers)
+			{
+				var targetActor = capturableTargetOptions.MinByOrDefault(target => (target.CenterPosition - capturer.Actor.CenterPosition).LengthSquared);
+				if (targetActor == null)
+					continue;
 
-		void QueueCaptureOrderFor<TTargetType>(IBot bot, Actor capturer, CaptureTarget<TTargetType> target) where TTargetType : class, ITraitInfoInterface
-		{
-			if (capturer == null)
-				return;
-
-			if (target == null)
-				return;
-
-			if (target.Actor == null)
-				return;
-
-			bot.QueueOrder(new Order(target.OrderString, capturer, Target.FromActor(target.Actor), true));
-			AIUtils.BotDebug("AI ({0}): Ordered {1} to capture {2}", player.ClientIndex, capturer, target.Actor);
-			activeCapturers.Add(capturer);
-		}
-
-		CaptureTarget<TTargetType> GetCapturerTargetClosestToOrDefault<TTargetType>(Actor capturer, IEnumerable<CaptureTarget<TTargetType>> targets)
-			where TTargetType : class, ITraitInfoInterface
-		{
-			return targets.MinByOrDefault(target => (target.Actor.CenterPosition - capturer.CenterPosition).LengthSquared);
+				bot.QueueOrder(new Order("CaptureActor", capturer.Actor, Target.FromActor(targetActor), true));
+				AIUtils.BotDebug("AI ({0}): Ordered {1} to capture {2}", player.ClientIndex, capturer.Actor, targetActor);
+				activeCapturers.Add(capturer.Actor);
+			}
 		}
 	}
 }

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

@@ -50,7 +50,7 @@ namespace OpenRA.Mods.Common.Traits
 			: base(info)
 		{
 			self = init.Self;
-			OpenPosition = Info.TransitionDelay;
+			Position = OpenPosition = Info.TransitionDelay;
 			building = self.Trait<Building>();
 			blockedPositions = building.Info.Tiles(self.Location);
 			Footprint = blockedPositions;

OpenRA.Mods.Common/Traits/Captures.cs

@@ -95,15 +95,11 @@ namespace OpenRA.Mods.Common.Traits
 			if (order.OrderString != "CaptureActor" || IsTraitDisabled)
 				return;
 
-			var target = self.ResolveFrozenActorOrder(order, Color.Red);
-			if (target.Type != TargetType.Actor)
-				return;
-
 			if (!order.Queued)
 				self.CancelActivity();
 
-			self.SetTargetLine(target, Color.Red);
-			self.QueueActivity(new CaptureActor(self, target.Actor));
+			self.SetTargetLine(order.Target, Color.Red);
+			self.QueueActivity(new CaptureActor(self, order.Target));
 		}
 
 		protected override void TraitEnabled(Actor self) { captureManager.RefreshCaptures(self); }

OpenRA.Mods.Common/Traits/Carryall.cs

@@ -265,18 +265,17 @@ namespace OpenRA.Mods.Common.Traits
 			{
 				if (order.OrderString == "PickupUnit")
 				{
-					var target = self.ResolveFrozenActorOrder(order, Color.Yellow);
-					if (target.Type != TargetType.Actor)
+					if (order.Target.Type != TargetType.Actor)
 						return;
 
-					if (!ReserveCarryable(self, target.Actor))
+					if (!ReserveCarryable(self, order.Target.Actor))
 						return;
 
 					if (!order.Queued)
 						self.CancelActivity();
 
-					self.SetTargetLine(target, Color.Yellow);
-					self.QueueActivity(order.Queued, new PickupUnit(self, target.Actor, Info.LoadingDelay));
+					self.SetTargetLine(order.Target, Color.Yellow);
+					self.QueueActivity(order.Queued, new PickupUnit(self, order.Target.Actor, Info.LoadingDelay));
 				}
 			}
 		}

OpenRA.Mods.Common/Traits/DeliversCash.cs

@@ -69,15 +69,11 @@ namespace OpenRA.Mods.Common.Traits
 			if (order.OrderString != "DeliverCash")
 				return;
 
-			var target = self.ResolveFrozenActorOrder(order, Color.Yellow);
-			if (target.Type != TargetType.Actor)
-				return;
-
 			if (!order.Queued)
 				self.CancelActivity();
 
-			self.SetTargetLine(target, Color.Yellow);
-			self.QueueActivity(new DonateCash(self, target.Actor, info.Payload, info.PlayerExperience));
+			self.SetTargetLine(order.Target, Color.Yellow);
+			self.QueueActivity(new DonateCash(self, order.Target, info.Payload, info.PlayerExperience));
 		}
 
 		void INotifyCashTransfer.OnAcceptingCash(Actor self, Actor donor) { }

OpenRA.Mods.Common/Traits/DeliversExperience.cs

@@ -71,21 +71,20 @@ namespace OpenRA.Mods.Common.Traits
 			if (order.OrderString != "DeliverExperience")
 				return;
 
-			var target = self.ResolveFrozenActorOrder(order, Color.Yellow);
-			if (target.Type != TargetType.Actor)
-				return;
-
-			var targetGainsExperience = target.Actor.Trait<GainsExperience>();
-			if (targetGainsExperience.Level == targetGainsExperience.MaxLevel)
+			if (order.Target.Type == TargetType.Actor)
+			{
+				var targetGainsExperience = order.Target.Actor.Trait<GainsExperience>();
+				if (targetGainsExperience.Level == targetGainsExperience.MaxLevel)
+					return;
+			}
+			else if (order.Target.Type != TargetType.FrozenActor)
 				return;
 
 			if (!order.Queued)
 				self.CancelActivity();
 
-			var level = gainsExperience.Level;
-
-			self.SetTargetLine(target, Color.Yellow);
-			self.QueueActivity(new DonateExperience(self, target.Actor, level, info.PlayerExperience, targetGainsExperience));
+			self.SetTargetLine(order.Target, Color.Yellow);
+			self.QueueActivity(new DonateExperience(self, order.Target, gainsExperience.Level, info.PlayerExperience));
 		}
 
 		public class DeliversExperienceOrderTargeter : UnitOrderTargeter

OpenRA.Mods.Common/Traits/Demolishable.cs

@@ -45,6 +45,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		ConditionManager conditionManager;
 		List<DemolishAction> actions = new List<DemolishAction>();
+		List<DemolishAction> removeActions = new List<DemolishAction>();
 
 		public Demolishable(DemolishableInfo info)
 			: base(info) { }
@@ -88,9 +89,18 @@ namespace OpenRA.Mods.Common.Traits
 					if (Util.ApplyPercentageModifiers(100, modifiers) > 0)
 						self.Kill(a.Saboteur);
 					else if (a.Token != ConditionManager.InvalidConditionToken)
+					{
 						conditionManager.RevokeCondition(self, a.Token);
+						removeActions.Add(a);
+					}
 				}
 			}
+
+			// Remove expired actions to avoid double-revoking
+			foreach (var a in removeActions)
+				actions.Remove(a);
+
+			removeActions.Clear();
 		}
 	}
 }

OpenRA.Mods.Common/Traits/Demolition.cs

@@ -75,19 +75,18 @@ namespace OpenRA.Mods.Common.Traits
 			if (order.OrderString != "C4")
 				return;
 
-			var target = self.ResolveFrozenActorOrder(order, Color.Red);
-			if (target.Type != TargetType.Actor)
-				return;
-
-			var demolishable = target.Actor.TraitOrDefault<IDemolishable>();
-			if (demolishable == null || !demolishable.IsValidTarget(target.Actor, self))
-				return;
+			if (order.Target.Type == TargetType.Actor)
+			{
+				var demolishables = order.Target.Actor.TraitsImplementing<IDemolishable>();
+				if (!demolishables.Any(i => i.IsValidTarget(order.Target.Actor, self)))
+					return;
+			}
 
 			if (!order.Queued)
 				self.CancelActivity();
 
-			self.SetTargetLine(target, Color.Red);
-			self.QueueActivity(new Demolish(self, target.Actor, info.EnterBehaviour, info.DetonationDelay,
+			self.SetTargetLine(order.Target, Color.Red);
+			self.QueueActivity(new Demolish(self, order.Target, info.EnterBehaviour, info.DetonationDelay,
 				info.Flashes, info.FlashesDelay, info.FlashInterval));
 		}
 

OpenRA.Mods.Common/Traits/EngineerRepair.cs

@@ -76,15 +76,11 @@ namespace OpenRA.Mods.Common.Traits
 			if (order.OrderString != "EngineerRepair" || !IsValidOrder(self, order))
 				return;
 
-			var target = self.ResolveFrozenActorOrder(order, Color.Yellow);
-			if (target.Type != TargetType.Actor)
-				return;
-
 			if (!order.Queued)
 				self.CancelActivity();
 
-			self.SetTargetLine(target, Color.Yellow);
-			self.QueueActivity(new RepairBuilding(self, target.Actor, info.EnterBehaviour, info.ValidStances));
+			self.SetTargetLine(order.Target, Color.Yellow);
+			self.QueueActivity(new RepairBuilding(self, order.Target, info.EnterBehaviour, info.ValidStances));
 		}
 
 		class EngineerRepairOrderTargeter : UnitOrderTargeter

OpenRA.Mods.Common/Traits/EntersTunnels.cs

@@ -62,15 +62,11 @@ namespace OpenRA.Mods.Common.Traits
 
 		public void ResolveOrder(Actor self, Order order)
 		{
-			if (order.OrderString != "EnterTunnel")
+			if (order.OrderString != "EnterTunnel" || order.Target.Type != TargetType.Actor)
 				return;
 
-			var target = self.ResolveFrozenActorOrder(order, Color.Red);
-			if (target.Type != TargetType.Actor)
-				return;
-
-			var tunnel = target.Actor.TraitOrDefault<TunnelEntrance>();
-			if (!tunnel.Exit.HasValue)
+			var tunnel = order.Target.Actor.TraitOrDefault<TunnelEntrance>();
+			if (tunnel == null || !tunnel.Exit.HasValue)
 				return;
 
 			if (!order.Queued)

OpenRA.Mods.Common/Traits/GivesBounty.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Mods.Common.Effects;
 using OpenRA.Primitives;
@@ -35,20 +36,13 @@ namespace OpenRA.Mods.Common.Traits
 		public override object Create(ActorInitializer init) { return new GivesBounty(this); }
 	}
 
-	class GivesBounty : ConditionalTrait<GivesBountyInfo>, INotifyKilled
+	class GivesBounty : ConditionalTrait<GivesBountyInfo>, INotifyKilled, INotifyPassengerEntered, INotifyPassengerExited
 	{
-		Cargo cargo;
+		Dictionary<Actor, GivesBounty[]> passengerBounties = new Dictionary<Actor, GivesBounty[]>();
 
 		public GivesBounty(GivesBountyInfo info)
 			: base(info) { }
 
-		protected override void Created(Actor self)
-		{
-			base.Created(self);
-
-			cargo = self.TraitOrDefault<Cargo>();
-		}
-
 		int GetBountyValue(Actor self)
 		{
 			return self.GetSellValue() * Info.Percentage / 100;
@@ -57,15 +51,10 @@ namespace OpenRA.Mods.Common.Traits
 		int GetDisplayedBountyValue(Actor self)
 		{
 			var bounty = GetBountyValue(self);
-			if (cargo == null)
-				return bounty;
-
-			foreach (var a in cargo.Passengers)
-			{
-				var givesBounties = a.TraitsImplementing<GivesBounty>().Where(gb => !gb.IsTraitDisabled);
-				foreach (var givesBounty in givesBounties)
-					bounty += givesBounty.GetDisplayedBountyValue(a);
-			}
+			foreach (var pb in passengerBounties)
+				foreach (var b in pb.Value)
+					if (!b.IsTraitDisabled)
+						bounty += b.GetDisplayedBountyValue(pb.Key);
 
 			return bounty;
 		}
@@ -87,5 +76,15 @@ namespace OpenRA.Mods.Common.Traits
 
 			e.Attacker.Owner.PlayerActor.Trait<PlayerResources>().ChangeCash(GetBountyValue(self));
 		}
+
+		void INotifyPassengerEntered.OnPassengerEntered(Actor self, Actor passenger)
+		{
+			passengerBounties.Add(passenger, passenger.TraitsImplementing<GivesBounty>().ToArray());
+		}
+
+		void INotifyPassengerExited.OnPassengerExited(Actor self, Actor passenger)
+		{
+			passengerBounties.Remove(passenger);
+		}
 	}
 }

OpenRA.Mods.Common/Traits/Guard.cs

@@ -55,7 +55,7 @@ namespace OpenRA.Mods.Common.Traits
 			self.SetTargetLine(target, Color.Yellow);
 
 			var range = target.Actor.Info.TraitInfo<GuardableInfo>().Range;
-			self.QueueActivity(new AttackMoveActivity(self, move.MoveFollow(self, target, WDist.Zero, range)));
+			self.QueueActivity(new AttackMoveActivity(self, move.MoveFollow(self, target, WDist.Zero, range, targetLineColor: Color.Yellow)));
 		}
 
 		public string VoicePhraseForOrder(Actor self, Order order)

OpenRA.Mods.Common/Traits/Mobile.cs

@@ -457,11 +457,33 @@ namespace OpenRA.Mods.Common.Traits
 
 		#region IMove
 
-		public Activity MoveTo(CPos cell, int nearEnough) { return new Move(self, cell, WDist.FromCells(nearEnough)); }
-		public Activity MoveTo(CPos cell, Actor ignoreActor) { return new Move(self, cell, WDist.Zero, ignoreActor); }
-		public Activity MoveWithinRange(Target target, WDist range) { return new MoveWithinRange(self, target, WDist.Zero, range); }
-		public Activity MoveWithinRange(Target target, WDist minRange, WDist maxRange) { return new MoveWithinRange(self, target, minRange, maxRange); }
-		public Activity MoveFollow(Actor self, Target target, WDist minRange, WDist maxRange) { return new Follow(self, target, minRange, maxRange); }
+		public Activity MoveTo(CPos cell, int nearEnough)
+		{
+			return new Move(self, cell, WDist.FromCells(nearEnough));
+		}
+
+		public Activity MoveTo(CPos cell, Actor ignoreActor)
+		{
+			return new Move(self, cell, WDist.Zero, ignoreActor);
+		}
+
+		public Activity MoveWithinRange(Target target, WDist range,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
+		{
+			return new MoveWithinRange(self, target, WDist.Zero, range, initialTargetPosition, targetLineColor);
+		}
+
+		public Activity MoveWithinRange(Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
+		{
+			return new MoveWithinRange(self, target, minRange, maxRange, initialTargetPosition, targetLineColor);
+		}
+
+		public Activity MoveFollow(Actor self, Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
+		{
+			return new Follow(self, target, minRange, maxRange, initialTargetPosition, targetLineColor);
+		}
 
 		public Activity MoveIntoWorld(Actor self, CPos cell, SubCell subCell = SubCell.Any)
 		{
@@ -481,12 +503,13 @@ namespace OpenRA.Mods.Common.Traits
 			return VisualMove(self, pos, self.World.Map.CenterOfSubCell(cell, subCell), cell);
 		}
 
-		public Activity MoveToTarget(Actor self, Target target)
+		public Activity MoveToTarget(Actor self, Target target,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null)
 		{
 			if (target.Type == TargetType.Invalid)
 				return null;
 
-			return new MoveAdjacentTo(self, target);
+			return new MoveAdjacentTo(self, target, initialTargetPosition, targetLineColor);
 		}
 
 		public Activity MoveIntoTarget(Actor self, Target target)
@@ -494,7 +517,9 @@ namespace OpenRA.Mods.Common.Traits
 			if (target.Type == TargetType.Invalid)
 				return null;
 
-			return VisualMove(self, self.CenterPosition, target.Positions.PositionClosestTo(self.CenterPosition));
+			// Activity cancels if the target moves by more than half a cell
+			// to avoid problems with the cell grid
+			return new VisualMoveIntoTarget(self, target, new WDist(512));
 		}
 
 		public Activity VisualMove(Actor self, WPos fromPos, WPos toPos)

OpenRA.Mods.Common/Traits/Modifiers/FrozenUnderFog.cs

@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System;
 using System.Collections.Generic;
 using System.Drawing;
 using System.Linq;
@@ -27,7 +28,7 @@ namespace OpenRA.Mods.Common.Traits
 		public object Create(ActorInitializer init) { return new FrozenUnderFog(init, this); }
 	}
 
-	public class FrozenUnderFog : IRenderModifier, IDefaultVisibility, ITick, ITickRender, ISync, INotifyCreated
+	public class FrozenUnderFog : ICreatesFrozenActors, IRenderModifier, IDefaultVisibility, ITick, ITickRender, ISync, INotifyCreated, INotifyOwnerChanged, INotifyActorDisposing
 	{
 		[Sync] public int VisibilityHash;
 
@@ -37,6 +38,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		PlayerDictionary<FrozenState> frozenStates;
 		bool isRendering;
+		bool created;
 
 		class FrozenState
 		{
@@ -67,14 +69,10 @@ namespace OpenRA.Mods.Common.Traits
 		{
 			frozenStates = new PlayerDictionary<FrozenState>(self.World, (player, playerIndex) =>
 			{
-				var frozenActor = new FrozenActor(self, footprint, player, startsRevealed);
+				var frozenActor = new FrozenActor(self, this, footprint, player, startsRevealed);
 				player.PlayerActor.Trait<FrozenActorLayer>().Add(frozenActor);
 				return new FrozenState(frozenActor) { IsVisible = startsRevealed };
 			});
-
-			if (startsRevealed)
-				for (var playerIndex = 0; playerIndex < frozenStates.Count; playerIndex++)
-					UpdateFrozenActor(self, frozenStates[playerIndex].FrozenActor, playerIndex);
 		}
 
 		void UpdateFrozenActor(Actor self, FrozenActor frozenActor, int playerIndex)
@@ -83,6 +81,17 @@ namespace OpenRA.Mods.Common.Traits
 			frozenActor.RefreshState();
 		}
 
+		void ICreatesFrozenActors.OnVisibilityChanged(FrozenActor frozen)
+		{
+			// Ignore callbacks during initial setup
+			if (!created)
+				return;
+
+			// Update state visibility to match the frozen actor to ensure consistency within the tick
+			// The rest of the state will be updated by ITick.Tick below
+			frozenStates[frozen.Viewer].IsVisible = !frozen.Visible;
+		}
+
 		bool IsVisibleInner(Actor self, Player byPlayer)
 		{
 			// If fog is disabled visibility is determined by shroud
@@ -106,6 +115,18 @@ namespace OpenRA.Mods.Common.Traits
 			if (self.Disposed)
 				return;
 
+			// Set the initial visibility state
+			// This relies on actor.GetTargetablePositions(), which is not safe to use from Created
+			// so we defer until the first real tick.
+			if (!created && startsRevealed)
+			{
+				for (var playerIndex = 0; playerIndex < frozenStates.Count; playerIndex++)
+					UpdateFrozenActor(self, frozenStates[playerIndex].FrozenActor, playerIndex);
+
+				created = true;
+				return;
+			}
+
 			VisibilityHash = 0;
 
 			for (var playerIndex = 0; playerIndex < frozenStates.Count; playerIndex++)
@@ -158,6 +179,20 @@ namespace OpenRA.Mods.Common.Traits
 		{
 			return bounds;
 		}
+
+		void INotifyOwnerChanged.OnOwnerChanged(Actor self, Player oldOwner, Player newOwner)
+		{
+			// Force a state update for the old owner so the tooltip etc doesn't show them as the owner
+			var oldOwnerIndex = self.World.Players.IndexOf(oldOwner);
+			UpdateFrozenActor(self, frozenStates[oldOwnerIndex].FrozenActor, oldOwnerIndex);
+		}
+
+		void INotifyActorDisposing.Disposing(Actor self)
+		{
+			// Invalidate the frozen actor (which exists if this actor was captured from an enemy)
+			// for the current owner
+			frozenStates[self.Owner].FrozenActor.Invalidate();
+		}
 	}
 
 	public class HiddenUnderFogInit : IActorInit { }

OpenRA.Mods.Common/Traits/Passenger.cs

@@ -32,9 +32,6 @@ namespace OpenRA.Mods.Common.Traits
 			"Default - use force move modifier (Alt) to disable.")]
 		public readonly AlternateTransportsMode AlternateTransportsMode = AlternateTransportsMode.Force;
 
-		[Desc("Number of retries using alternate transports.")]
-		public readonly int MaxAlternateTransportAttempts = 1;
-
 		[Desc("Range from self for looking for an alternate transport (default: 5.5 cells).")]
 		public readonly WDist AlternateTransportScanRange = WDist.FromCells(11) / 2;
 
@@ -161,9 +158,11 @@ namespace OpenRA.Mods.Common.Traits
 			if (!order.Queued)
 				self.CancelActivity();
 
-			var transports = order.OrderString == "EnterTransports";
 			self.SetTargetLine(order.Target, Color.Green);
-			self.QueueActivity(new EnterTransport(self, targetActor, transports ? Info.MaxAlternateTransportAttempts : 0, !transports));
+			if (order.OrderString == "EnterTransports")
+				self.QueueActivity(new EnterTransports(self, order.Target));
+			else
+				self.QueueActivity(new EnterTransport(self, order.Target));
 		}
 
 		public bool Reserve(Actor self, Cargo cargo)

OpenRA.Mods.Common/Traits/Player/ModularBot.cs

@@ -63,6 +63,11 @@ namespace OpenRA.Mods.Common.Traits
 		// Called by the host's player creation code
 		public void Activate(Player p)
 		{
+			// Bot logic is not allowed to affect world state, and can only act by issuing orders
+			// These orders are recorded in the replay, so bots shouldn't be enabled during replays
+			if (p.World.IsReplay)
+				return;
+
 			IsEnabled = true;
 			player = p;
 			tickModules = p.PlayerActor.TraitsImplementing<IBotTick>().ToArray();

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

@@ -85,7 +85,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		bool IRenderAboveShroudWhenSelected.SpatiallyPartitionable { get { return false; } }
 
-		void INotifyBecomingIdle.OnBecomingIdle(Actor a)
+		void INotifyBecomingIdle.OnBecomingIdle(Actor self)
 		{
 			targets = null;
 		}
@@ -115,15 +115,12 @@ namespace OpenRA.Mods.Common.Traits
 			if (!self.Owner.IsAlliedWith(self.World.LocalPlayer))
 				return;
 
-			self.World.AddFrameEndTask(w =>
-			{
-				if (self.Disposed)
-					return;
+			if (self.Disposed)
+				return;
 
-				var line = self.TraitOrDefault<DrawLineToTarget>();
-				if (line != null)
-					line.SetTarget(self, target, color, display);
-			});
+			var line = self.TraitOrDefault<DrawLineToTarget>();
+			if (line != null)
+				line.SetTarget(self, target, color, display);
 		}
 	}
 }

OpenRA.Mods.Common/Traits/Repairable.cs

@@ -112,8 +112,12 @@ namespace OpenRA.Mods.Common.Traits
 					self.CancelActivity();
 
 				self.SetTargetLine(order.Target, Color.Green);
-				self.QueueActivity(new WaitForTransport(self, ActivityUtils.SequenceActivities(movement.MoveToTarget(self, order.Target),
-					new CallFunc(() => AfterReachActivities(self, order, movement)))));
+
+				var activities = ActivityUtils.SequenceActivities(
+					movement.MoveToTarget(self, order.Target, targetLineColor: Color.Green),
+					new CallFunc(() => AfterReachActivities(self, order, movement)));
+
+				self.QueueActivity(new WaitForTransport(self, activities));
 
 				TryCallTransport(self, order.Target, new CallFunc(() => AfterReachActivities(self, order, movement)));
 			}

OpenRA.Mods.Common/Traits/RepairableNear.cs

@@ -85,7 +85,7 @@ namespace OpenRA.Mods.Common.Traits
 			if (!order.Queued)
 				self.CancelActivity();
 
-			self.QueueActivity(movement.MoveWithinRange(order.Target, info.CloseEnough));
+			self.QueueActivity(movement.MoveWithinRange(order.Target, info.CloseEnough, targetLineColor: Color.Green));
 			self.QueueActivity(new Repair(self, order.Target.Actor, info.CloseEnough));
 
 			self.SetTargetLine(order.Target, Color.Green, false);

OpenRA.Mods.Common/Traits/RepairsBridges.cs

@@ -82,6 +82,7 @@ namespace OpenRA.Mods.Common.Traits
 		public void ResolveOrder(Actor self, Order order)
 		{
 			// TODO: Add support for FrozenActors
+			// The activity supports it, but still missing way to freeze bridge state on the hut
 			if (order.OrderString == "RepairBridge" && order.Target.Type == TargetType.Actor)
 			{
 				var targetActor = order.Target.Actor;
@@ -104,7 +105,7 @@ namespace OpenRA.Mods.Common.Traits
 					self.CancelActivity();
 
 				self.SetTargetLine(order.Target, Color.Yellow);
-				self.QueueActivity(new RepairBridge(self, targetActor, info.EnterBehaviour, info.RepairNotification));
+				self.QueueActivity(new RepairBridge(self, order.Target, info.EnterBehaviour, info.RepairNotification));
 			}
 		}
 

OpenRA.Mods.Common/Traits/SupportPowers/AirstrikePower.cs

@@ -106,6 +106,8 @@ namespace OpenRA.Mods.Common.Traits
 
 			Action<Actor> onRemovedFromWorld = a =>
 			{
+				aircraftInRange[a] = false;
+
 				// Checking for attack range is not relevant here because
 				// aircraft may be shot down before entering. Thus we remove
 				// the camera and beacon only if the whole squad is dead.

OpenRA.Mods.Common/Traits/SupportPowers/ParatroopersPower.cs

@@ -133,6 +133,8 @@ namespace OpenRA.Mods.Common.Traits
 
 			Action<Actor> onRemovedFromWorld = a =>
 			{
+				aircraftInRange[a] = false;
+
 				// Checking for attack range is not relevant here because
 				// aircraft may be shot down before entering. Thus we remove
 				// the camera and beacon only if the whole squad is dead.

OpenRA.Mods.Common/Traits/Turreted.cs

@@ -255,12 +255,6 @@ namespace OpenRA.Mods.Common.Traits
 			if (attack != null && attack.IsAiming)
 				attack.OnStopOrder(self);
 		}
-
-		protected override void TraitResumed(Actor self)
-		{
-			if (attack != null)
-				FaceTarget(self, attack.Target);
-		}
 	}
 
 	public class TurretFacingInit : IActorInit<int>

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

@@ -283,5 +283,10 @@ namespace OpenRA.Mods.Common.Traits
 				foreach (var preview in previewsForCell.Value)
 					destinationBuffer.Add(Pair.New(previewsForCell.Key, preview.Owner.Color.RGB));
 		}
+
+		public EditorActorPreview this[string id]
+		{
+			get { return previews.FirstOrDefault(p => p.ID.ToLowerInvariant() == id); }
+		}
 	}
 }

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

@@ -29,18 +29,17 @@ namespace OpenRA.Mods.Common.Traits
 
 			if (subjectClient == null)
 			{
-				Game.Debug("Order sent to {0}: resolved ClientIndex `{1}` doesn't exist", order.Subject.Owner.PlayerName, subjectClientId);
+				Log.Write("debug", "Order sent to {0}: resolved ClientIndex `{1}` doesn't exist", order.Subject.Owner.PlayerName, subjectClientId);
 				return false;
 			}
 
 			var isBotOrder = subjectClient.Bot != null && clientId == subjectClient.BotControllerClientIndex;
 
-			// Drop exploiting orders
+			// Drop orders from players who shouldn't be able to control this actor
+			// This may be because the owner changed within the last net tick,
+			// or, less likely, the client may be trying to do something malicious.
 			if (subjectClientId != clientId && !isBotOrder)
-			{
-				Game.Debug("Detected exploit order from client {0}: {1}", clientId, order.OrderString);
 				return false;
-			}
 
 			return order.Subject.AcceptsOrder(order.OrderString);
 		}

OpenRA.Mods.Common/TraitsInterfaces.cs

@@ -397,11 +397,15 @@ namespace OpenRA.Mods.Common.Traits
 	{
 		Activity MoveTo(CPos cell, int nearEnough);
 		Activity MoveTo(CPos cell, Actor ignoreActor);
-		Activity MoveWithinRange(Target target, WDist range);
-		Activity MoveWithinRange(Target target, WDist minRange, WDist maxRange);
-		Activity MoveFollow(Actor self, Target target, WDist minRange, WDist maxRange);
+		Activity MoveWithinRange(Target target, WDist range,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null);
+		Activity MoveWithinRange(Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null);
+		Activity MoveFollow(Actor self, Target target, WDist minRange, WDist maxRange,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null);
+		Activity MoveToTarget(Actor self, Target target,
+			WPos? initialTargetPosition = null, Color? targetLineColor = null);
 		Activity MoveIntoWorld(Actor self, CPos cell, SubCell subCell = SubCell.Any);
-		Activity MoveToTarget(Actor self, Target target);
 		Activity MoveIntoTarget(Actor self, Target target);
 		Activity VisualMove(Actor self, WPos fromPos, WPos toPos);
 		int EstimatedMoveDuration(Actor self, WPos fromPos, WPos toPos);

OpenRA.Mods.Common/UpdateRules/Rules/20181215/RemoveAttackSuicides.cs

@@ -0,0 +1,51 @@
+#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.Collections.Generic;
+using System.Linq;
+
+namespace OpenRA.Mods.Common.UpdateRules.Rules
+{
+	public class RemoveAttackSuicides : UpdateRule
+	{
+		public override string Name { get { return "AttackSuicides trait has been removed."; } }
+		public override string Description
+		{
+			get
+			{
+				return "The AttackSuicides trait has been removed, and should be replaced by\n" +
+				       "AttackFrontal + GrantConditionOnAttack + GrantConditionOnDeploy + a dummy\n" +
+				       "weapon for targeting. Affected actors are listed so that these traits can be defined.";
+			}
+		}
+
+		readonly List<string> locations = new List<string>();
+
+		public override IEnumerable<string> AfterUpdate(ModData modData)
+		{
+			if (locations.Any())
+				yield return "The AttackSuicides trait has been removed from the following actors.\n" +
+				             "You must manually define AttackFrontal, GrantConditionOnAttack, GrantConditionOnDeploy\n" +
+				             "traits and create a dummy weapon to use for targeting:\n" +
+				             UpdateUtils.FormatMessageList(locations);
+
+			locations.Clear();
+		}
+
+		public override IEnumerable<string> UpdateActorNode(ModData modData, MiniYamlNode actorNode)
+		{
+			if (actorNode.RemoveNodes("AttackSuicides") > 0)
+				locations.Add("{0} ({1})".F(actorNode.Key, actorNode.Location.Filename));
+
+			yield break;
+		}
+	}
+}

OpenRA.Mods.Common/UpdateRules/UpdatePath.cs

@@ -86,7 +86,7 @@ namespace OpenRA.Mods.Common.UpdateRules
 
 			new UpdatePath("release-20180923", "release-20181215", new UpdateRule[0]),
 
-			new UpdatePath("release-20181215", new UpdateRule[]
+			new UpdatePath("release-20181215", "playtest-20190106", new UpdateRule[]
 			{
 				// Bleed only changes here
 				new AddCarryableHarvester(),
@@ -113,6 +113,11 @@ namespace OpenRA.Mods.Common.UpdateRules
 				new RemoveAttackIgnoresVisibility(),
 				new ReplacedWithChargeAnimation(),
 				new RefactorResourceLevelAnimating(),
+			}),
+
+			new UpdatePath("playtest-20190106", new UpdateRule[]
+			{
+				new RemoveAttackSuicides(),
 			})
 		};
 

OpenRA.Mods.Common/Warheads/Warhead.cs

@@ -82,6 +82,9 @@ namespace OpenRA.Mods.Common.Warheads
 		/// <summary>Checks if the warhead is valid against (can do something to) the frozen actor.</summary>
 		public bool IsValidAgainst(FrozenActor victim, Actor firedBy)
 		{
+			if (!victim.IsValid)
+				return false;
+
 			// AffectsParent checks do not make sense for FrozenActors, so skip to stance checks
 			var stance = firedBy.Owner.Stances[victim.Owner];
 			if (!ValidStances.HasStance(stance))

OpenRA.Mods.Common/Widgets/Logic/Editor/ActorEditLogic.cs

@@ -122,8 +122,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				var actorId = actorIDField.Text.ToLowerInvariant();
 				if (CurrentActor.ID.ToLowerInvariant() != actorId)
 				{
-					var found = world.Map.ActorDefinitions.Any(x => x.Key.ToLowerInvariant() == actorId);
-					if (found)
+					if (editorActorLayer[actorId] != null)
 					{
 						nextActorIDStatus = ActorIDStatus.Duplicate;
 						return;
@@ -143,8 +142,6 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 
 		void SetActorID(World world, string actorId)
 		{
-			var actorDef = world.Map.ActorDefinitions.First(x => x.Key == CurrentActor.ID);
-			actorDef.Key = actorId;
 			CurrentActor.ID = actorId;
 			nextActorIDStatus = ActorIDStatus.Normal;
 		}

OpenRA.Mods.Common/Widgets/Logic/Editor/MapEditorLogic.cs

@@ -88,6 +88,16 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			var copypasteButton = widget.GetOrNull<ButtonWidget>("COPYPASTE_BUTTON");
 			if (copypasteButton != null)
 			{
+				// HACK: Replace Ctrl with Cmd on macOS
+				// TODO: Add platform-specific override support to HotkeyManager
+				// and then port the editor hotkeys to this system.
+				var copyPasteKey = copypasteButton.Key.GetValue();
+				if (Platform.CurrentPlatform == PlatformType.OSX && copyPasteKey.Modifiers.HasModifier(Modifiers.Ctrl))
+				{
+					var modified = new Hotkey(copyPasteKey.Key, copyPasteKey.Modifiers & ~Modifiers.Ctrl | Modifiers.Meta);
+					copypasteButton.Key = FieldLoader.GetValue<HotkeyReference>("Key", modified.ToString());
+				}
+
 				copypasteButton.OnClick = () => editorViewport.SetBrush(new EditorCopyPasteBrush(editorViewport, worldRenderer, () => copyFilters));
 				copypasteButton.IsHighlighted = () => editorViewport.CurrentBrush is EditorCopyPasteBrush;
 			}

OpenRA.Mods.Common/Widgets/Logic/Ingame/IngameChatLogic.cs

@@ -85,8 +85,9 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 					else if (chatTraits != null)
 					{
 						var text = chatText.Text.Trim();
+						var from = world.IsReplay ? null : orderManager.LocalClient.Name;
 						foreach (var trait in chatTraits)
-							trait.OnChat(orderManager.LocalClient.Name, text);
+							trait.OnChat(from, text);
 					}
 				}
 

OpenRA.Mods.Common/Widgets/Logic/Lobby/LobbyUtils.cs

@@ -70,11 +70,11 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				return item;
 			};
 
-			dropdown.ShowDropDown("LABEL_DROPDOWN_TEMPLATE", 167, options, setupItem);
+			dropdown.ShowDropDown("LABEL_DROPDOWN_TEMPLATE", 180, options, setupItem);
 		}
 
 		public static void ShowPlayerActionDropDown(DropDownButtonWidget dropdown, Session.Slot slot,
-			Session.Client c, OrderManager orderManager, Widget lobby,  Action before, Action after)
+			Session.Client c, OrderManager orderManager, Widget lobby, Action before, Action after)
 		{
 			Action<bool> okPressed = tempBan => { orderManager.IssueOrder(Order.Command("kick {0} {1}".F(c.Index, tempBan))); after(); };
 			var onClick = new Action(() =>
@@ -194,7 +194,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 			var options = factions.Where(f => f.Value.Selectable).GroupBy(f => f.Value.Side)
 				.ToDictionary(g => g.Key ?? "", g => g.Select(f => f.Key));
 
-			dropdown.ShowDropDown("FACTION_DROPDOWN_TEMPLATE", 150, options, setupItem);
+			dropdown.ShowDropDown("FACTION_DROPDOWN_TEMPLATE", 154, options, setupItem);
 		}
 
 		public static void ShowColorDropDown(DropDownButtonWidget color, Session.Client client,
@@ -419,7 +419,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 		}
 
 		public static void SetupPlayerActionWidget(Widget parent, Session.Slot s, Session.Client c, OrderManager orderManager,
-			WorldRenderer worldRenderer,  Widget lobby, Action before, Action after)
+			WorldRenderer worldRenderer, Widget lobby, Action before, Action after)
 		{
 			var slot = parent.Get<DropDownButtonWidget>("PLAYER_ACTION");
 			slot.IsVisible = () => Game.IsHost && c.Index != orderManager.LocalClient.Index;

OpenRA.Mods.Common/Widgets/Logic/MissionBrowserLogic.cs

@@ -11,6 +11,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Threading;
 using OpenRA.Graphics;
@@ -106,11 +107,11 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 					var missionMapPaths = kv.Value.Nodes.Select(n => n.Key).ToList();
 
 					var previews = modData.MapCache
-						.Where(p => p.Status == MapStatus.Available)
+						.Where(p => p.Class == MapClassification.System && p.Status == MapStatus.Available)
 						.Select(p => new
 						{
 							Preview = p,
-							Index = missionMapPaths.IndexOf(Platform.UnresolvePath(p.Package.Name))
+							Index = missionMapPaths.IndexOf(Path.GetFileName(p.Package.Name))
 						})
 						.Where(x => x.Index != -1)
 						.OrderBy(x => x.Index)

OpenRA.Mods.Common/Widgets/ProductionPaletteWidget.cs

@@ -47,8 +47,8 @@ namespace OpenRA.Mods.Common.Widgets
 		public readonly int2 IconMargin = int2.Zero;
 		public readonly int2 IconSpriteOffset = int2.Zero;
 
-		public readonly string TabClick = null;
-		public readonly string DisabledTabClick = null;
+		public readonly string ClickSound = ChromeMetrics.Get<string>("ClickSound");
+		public readonly string ClickDisabledSound = ChromeMetrics.Get<string>("ClickDisabledSound");
 		public readonly string TooltipContainer;
 		public readonly string TooltipTemplate = "PRODUCTION_TOOLTIP";
 
@@ -267,14 +267,15 @@ namespace OpenRA.Mods.Common.Widgets
 		{
 			if (PickUpCompletedBuildingIcon(icon, item))
 			{
-				Game.Sound.Play(SoundType.UI, TabClick);
+				Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Sounds", ClickSound, null);
 				return true;
 			}
 
 			if (item != null && item.Paused)
 			{
 				// Resume a paused item
-				Game.Sound.Play(SoundType.UI, TabClick);
+				Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Sounds", ClickSound, null);
+				Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Speech", CurrentQueue.Info.QueuedAudio, World.LocalPlayer.Faction.InternalName);
 				World.IssueOrder(Order.PauseProduction(CurrentQueue.Actor, icon.Name, false));
 				return true;
 			}
@@ -284,11 +285,11 @@ namespace OpenRA.Mods.Common.Widgets
 			if (buildable != null)
 			{
 				// Queue a new item
-				Game.Sound.Play(SoundType.UI, TabClick);
+				Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Sounds", ClickSound, null);
 				string notification;
 				var canQueue = CurrentQueue.CanQueue(buildable, out notification);
 
-				if (!CurrentQueue.AllQueued().Any(qi => qi.Item == icon.Name && !qi.Paused && qi.Infinite))
+				if (!CurrentQueue.AllQueued().Any())
 					Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Speech", notification, World.LocalPlayer.Faction.InternalName);
 
 				if (canQueue)
@@ -307,7 +308,7 @@ namespace OpenRA.Mods.Common.Widgets
 			if (item == null)
 				return false;
 
-			Game.Sound.Play(SoundType.UI, TabClick);
+			Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Sounds", ClickSound, null);
 
 			if (CurrentQueue.Info.DisallowPaused || item.Paused || item.Done || item.TotalCost == item.RemainingCost)
 			{
@@ -331,7 +332,7 @@ namespace OpenRA.Mods.Common.Widgets
 				return false;
 
 			// Directly cancel, skipping "on-hold"
-			Game.Sound.Play(SoundType.UI, TabClick);
+			Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Sounds", ClickSound, null);
 			Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Speech", CurrentQueue.Info.CancelledAudio, World.LocalPlayer.Faction.InternalName);
 			World.IssueOrder(Order.CancelProduction(CurrentQueue.Actor, icon.Name, handleCount));
 
@@ -351,7 +352,7 @@ namespace OpenRA.Mods.Common.Widgets
 				: false;
 
 			if (!handled)
-				Game.Sound.Play(SoundType.UI, DisabledTabClick);
+				Game.Sound.PlayNotification(World.Map.Rules, World.LocalPlayer, "Sounds", ClickDisabledSound, null);
 
 			return true;
 		}

OpenRA.Mods.D2k/Traits/AttackSwallow.cs

@@ -80,9 +80,10 @@ namespace OpenRA.Mods.D2k.Traits
 			public SwallowTarget(Actor self, Target target, bool allowMovement, bool forceAttack)
 				: base(self, target, allowMovement, forceAttack) { }
 
-			protected override Target RecalculateTarget(Actor self)
+			protected override Target RecalculateTarget(Actor self, out bool targetIsHiddenActor)
 			{
 				// Worms ignore visibility, so don't need to recalculate targets
+				targetIsHiddenActor = false;
 				return target;
 			}
 		}