Fly, use rotating buffer over list to store last 5 positions.

OpenRA.Game/Primitives/RingBuffer.cs

@@ -0,0 +1,146 @@
+#region Copyright & License Information
+/*
+ * Copyright (c) The OpenRA Developers and Contributors
+ * 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;
+using System.Collections.Generic;
+
+namespace OpenRA.Primitives
+{
+	/// <summary>Fixed size rorating buffer backed by an array.</summary>
+	public class RingBuffer<T> : ICollection<T>, IEnumerable<T>
+	{
+		readonly IComparer<T> comparer;
+		readonly T[] values;
+		int start;
+
+		public int Capacity => values.Length;
+		public int Count { get; private set; }
+		public bool IsReadOnly => false;
+
+		public RingBuffer(int capacity, IComparer<T> comparer)
+		{
+			this.comparer = comparer;
+			values = new T[capacity];
+			start = 0;
+			Count = 0;
+		}
+
+		public RingBuffer(int capacity)
+			: this(capacity, Comparer<T>.Default) { }
+
+		public void Add(T value)
+		{
+			values[(start + Count) % values.Length] = value;
+			if (Count < values.Length)
+				Count++;
+			else
+				start = (start + 1) % values.Length;
+		}
+
+		public void Clear()
+		{
+			Array.Clear(values, 0, values.Length);
+			start = 0;
+			Count = 0;
+		}
+
+		public bool Contains(T value)
+		{
+			var capacity = values.Length;
+			var end = start + Count;
+			for (var i = start; i < end; ++i)
+				if (comparer.Compare(values[i % capacity], value) == 0)
+					return true;
+
+			return false;
+		}
+
+		public void CopyTo(T[] array, int arrayIndex)
+		{
+			if (array == null)
+				throw new ArgumentNullException(nameof(array));
+
+			if (arrayIndex < 0)
+				throw new ArgumentNullException(nameof(arrayIndex));
+
+			if (arrayIndex + Count >= array.Length)
+				throw new ArgumentException("Invalid array capacity");
+
+			var destinationIndex = arrayIndex;
+			var end = start + Count;
+			var capacity = values.Length;
+			for (var i = start; i < end; ++i)
+				array[destinationIndex++] = values[i % capacity];
+		}
+
+		public bool Remove(T value)
+		{
+			var capacity = values.Length;
+			var end = start + Count;
+			for (var i = start; i < end; ++i)
+			{
+				if (comparer.Compare(values[i % capacity], value) == 0)
+				{
+					end--;
+					for (var j = i; j < end; ++j)
+						values[j % capacity] = values[(j + 1) % capacity];
+
+					Count--;
+					return true;
+				}
+			}
+
+			return false;
+		}
+
+		public T this[int pos]
+		{
+			get => values[(start + pos) % values.Length];
+
+			set
+			{
+				if (pos >= Count)
+					throw new ArgumentException($"Index out of bounds: {pos}");
+
+				values[(start + pos) % values.Length] = value;
+			}
+		}
+
+		public T First()
+		{
+			if (Count == 0)
+				throw new ArgumentException("Empty buffer");
+
+			return values[start];
+		}
+
+		public T Last()
+		{
+			if (Count == 0)
+				throw new ArgumentException("Empty buffer");
+
+			return values[(start + Count - 1) % values.Length];
+		}
+
+		public IEnumerator<T> GetEnumerator()
+		{
+			var initState = start + Count;
+			for (var i = 0; i < Count; i++)
+			{
+				if (start + Count != initState)
+					throw new InvalidOperationException("Collection was modified; enumeration operation may not execute");
+				yield return values[(start + i) % values.Length];
+			}
+		}
+
+		System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { return GetEnumerator(); }
+	}
+}

OpenRA.Game/WAngle.cs

@@ -39,7 +39,7 @@ public WAngle(int a)
 		public static WAngle operator -(WAngle a) { return new WAngle(-a.Angle); }
 
 		public static bool operator ==(WAngle me, WAngle other) { return me.Angle == other.Angle; }
-		public static bool operator !=(WAngle me, WAngle other) { return !(me == other); }
+		public static bool operator !=(WAngle me, WAngle other) { return me.Angle != other.Angle; }
 
 		public override int GetHashCode() { return Angle.GetHashCode(); }
 

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

@@ -10,7 +10,6 @@
 #endregion
 
 using System.Collections.Generic;
-using System.Linq;
 using OpenRA.Activities;
 using OpenRA.Mods.Common.Traits;
 using OpenRA.Primitives;
@@ -29,7 +28,7 @@ public class Fly : Activity
 		Target target;
 		Target lastVisibleTarget;
 		bool useLastVisibleTarget;
-		readonly List<WPos> positionBuffer = new();
+		readonly RingBuffer<WPos> previousPositions = new(5);
 
 		public Fly(Actor self, in Target t, WDist nearEnough, WPos? initialTargetPosition = null, Color? targetLineColor = null)
 			: this(self, t, initialTargetPosition, targetLineColor)
@@ -63,13 +62,10 @@ public Fly(Actor self, in Target t, WPos? initialTargetPosition = null, Color? t
 		public static void FlyTick(Actor self, Aircraft aircraft, WAngle desiredFacing, WDist desiredAltitude, in WVec moveOverride, bool idleTurn = false)
 		{
 			var dat = self.World.Map.DistanceAboveTerrain(aircraft.CenterPosition);
-			var move = aircraft.Info.CanSlide ? aircraft.FlyStep(desiredFacing) : aircraft.FlyStep(aircraft.Facing);
-			if (moveOverride != WVec.Zero)
-				move = moveOverride;
+			var move = moveOverride != WVec.Zero ? moveOverride : (aircraft.Info.CanSlide ? aircraft.FlyStep(desiredFacing) : aircraft.FlyStep(aircraft.Facing));
 
 			var oldFacing = aircraft.Facing;
-			var turnSpeed = aircraft.GetTurnSpeed(idleTurn);
-			aircraft.Facing = Util.TickFacing(aircraft.Facing, desiredFacing, turnSpeed);
+			aircraft.Facing = Util.TickFacing(aircraft.Facing, desiredFacing, aircraft.GetTurnSpeed(idleTurn));
 
 			var roll = idleTurn ? aircraft.Info.IdleRoll ?? aircraft.Info.Roll : aircraft.Info.Roll;
 			if (roll != WAngle.Zero)
@@ -104,22 +100,16 @@ public static void FlyTick(Actor self, Aircraft aircraft, WAngle desiredFacing,
 		// Should only be used for vertical-only movement, usually VTOL take-off or land. Terrain-induced altitude changes should always be handled by FlyTick.
 		public static bool VerticalTakeOffOrLandTick(Actor self, Aircraft aircraft, WAngle desiredFacing, WDist desiredAltitude, bool idleTurn = false)
 		{
-			var dat = self.World.Map.DistanceAboveTerrain(aircraft.CenterPosition);
-			var move = WVec.Zero;
-
 			var turnSpeed = idleTurn ? aircraft.IdleTurnSpeed ?? aircraft.TurnSpeed : aircraft.TurnSpeed;
 			aircraft.Facing = Util.TickFacing(aircraft.Facing, desiredFacing, turnSpeed);
 
-			if (dat != desiredAltitude)
-			{
-				var maxDelta = aircraft.Info.AltitudeVelocity.Length;
-				var deltaZ = (desiredAltitude.Length - dat.Length).Clamp(-maxDelta, maxDelta);
-				move += new WVec(0, 0, deltaZ);
-			}
-			else
+			var dat = self.World.Map.DistanceAboveTerrain(aircraft.CenterPosition);
+			if (dat == desiredAltitude)
 				return false;
 
-			aircraft.SetPosition(self, aircraft.CenterPosition + move);
+			var maxDelta = aircraft.Info.AltitudeVelocity.Length;
+			var deltaZ = (desiredAltitude.Length - dat.Length).Clamp(-maxDelta, maxDelta);
+			aircraft.SetPosition(self, aircraft.CenterPosition + new WVec(0, 0, deltaZ));
 			return true;
 		}
 
@@ -203,8 +193,7 @@ public override bool Tick(Actor self)
 
 			// HACK: Consider ourselves blocked if we have moved by less than 64 WDist in the last five ticks
 			// Stop if we are blocked and close enough
-			if (positionBuffer.Count >= 5 && (positionBuffer.Last() - positionBuffer[0]).LengthSquared < 4096 &&
-				delta.HorizontalLengthSquared <= nearEnough.LengthSquared)
+			if (previousPositions.Count == previousPositions.Capacity && (previousPositions.First() - previousPositions.Last()).LengthSquared < 4096 && delta.HorizontalLengthSquared <= nearEnough.LengthSquared)
 				return true;
 
 			// The next move would overshoot, so consider it close enough or set final position if we CanSlide
@@ -253,11 +242,8 @@ public override bool Tick(Actor self)
 					desiredFacing = aircraft.Facing;
 			}
 
-			positionBuffer.Add(self.CenterPosition);
-			if (positionBuffer.Count > 5)
-				positionBuffer.RemoveAt(0);
-
-			FlyTick(self, aircraft, desiredFacing, aircraft.Info.CruiseAltitude);
+			previousPositions.Add(self.CenterPosition);
+			FlyTick(self, aircraft, desiredFacing, aircraft.Info.CruiseAltitude, WVec.Zero);
 
 			return false;
 		}

OpenRA.Mods.Common/Util.cs

@@ -29,13 +29,17 @@ public static class Util
 		public static int TickFacing(int facing, int desiredFacing, int rot)
 		{
 			var leftTurn = (facing - desiredFacing) & 0xFF;
+			if (leftTurn < rot)
+				return desiredFacing & 0xFF;
+
 			var rightTurn = (desiredFacing - facing) & 0xFF;
-			if (Math.Min(leftTurn, rightTurn) < rot)
+			if (rightTurn < rot)
 				return desiredFacing & 0xFF;
-			else if (rightTurn < leftTurn)
+
+			if (rightTurn < leftTurn)
 				return (facing + rot) & 0xFF;
-			else
-				return (facing - rot) & 0xFF;
+
+			return (facing - rot) & 0xFF;
 		}
 
 		/// <summary>
@@ -46,8 +50,11 @@ public static int TickFacing(int facing, int desiredFacing, int rot)
 		public static WAngle TickFacing(WAngle facing, WAngle desiredFacing, WAngle step)
 		{
 			var leftTurn = (facing - desiredFacing).Angle;
+			if (leftTurn < step.Angle)
+				return desiredFacing;
+
 			var rightTurn = (desiredFacing - facing).Angle;
-			if (leftTurn < step.Angle || rightTurn < step.Angle)
+			if (rightTurn < step.Angle)
 				return desiredFacing;
 
 			return rightTurn < leftTurn ? facing + step : facing - step;