From cfc026a1ac4667fc3a05fad9fef7681f852ad545 Mon Sep 17 00:00:00 2001
From: Gustas <37534529+PunkPun@users.noreply.github.com>
Date: Wed, 3 May 2023 10:39:45 +0300
Subject: [PATCH] Fix aircraft jittering

---
 OpenRA.Mods.Common/Activities/Air/Fly.cs  | 17 ++++++++++++++---
 OpenRA.Mods.Common/Traits/Air/Aircraft.cs |  3 +++
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/OpenRA.Mods.Common/Activities/Air/Fly.cs b/OpenRA.Mods.Common/Activities/Air/Fly.cs
index 87d444761d..40163f79e3 100644
--- a/OpenRA.Mods.Common/Activities/Air/Fly.cs
+++ b/OpenRA.Mods.Common/Activities/Air/Fly.cs
@@ -9,6 +9,7 @@
  */
 #endregion
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using OpenRA.Activities;
@@ -185,7 +186,19 @@ namespace OpenRA.Mods.Common.Activities
 				return true;
 
 			var isSlider = aircraft.Info.CanSlide;
-			var desiredFacing = delta.HorizontalLengthSquared != 0 ? delta.Yaw : aircraft.Facing;
+
+			var desiredFacing = aircraft.Facing;
+			if (delta.HorizontalLengthSquared != 0)
+			{
+				var facing = delta.Yaw;
+
+				// Prevent jittering.
+				var diff = Math.Abs(facing.Angle - desiredFacing.Angle);
+				var deadzone = aircraft.Info.TurnDeadzone.Angle;
+				if (diff > deadzone && diff < 1024 - deadzone)
+					desiredFacing = facing;
+			}
+
 			var move = isSlider ? aircraft.FlyStep(desiredFacing) : aircraft.FlyStep(aircraft.Facing);
 
 			// Inside the minimum range, so reverse if we CanSlide, otherwise face away from the target.
@@ -194,9 +207,7 @@ namespace OpenRA.Mods.Common.Activities
 				if (isSlider)
 					FlyTick(self, aircraft, desiredFacing, aircraft.Info.CruiseAltitude, -move);
 				else
-				{
 					FlyTick(self, aircraft, desiredFacing + new WAngle(512), aircraft.Info.CruiseAltitude, move);
-				}
 
 				return false;
 			}
diff --git a/OpenRA.Mods.Common/Traits/Air/Aircraft.cs b/OpenRA.Mods.Common/Traits/Air/Aircraft.cs
index 18c2074edb..7988f8cc08 100644
--- a/OpenRA.Mods.Common/Traits/Air/Aircraft.cs
+++ b/OpenRA.Mods.Common/Traits/Air/Aircraft.cs
@@ -56,6 +56,9 @@ namespace OpenRA.Mods.Common.Traits
 		[Desc("Turn speed to apply when aircraft flies in circles while idle. Defaults to TurnSpeed if undefined.")]
 		public readonly WAngle? IdleTurnSpeed = null;
 
+		[Desc("When flying if the difference between current facing and desired facing is less than this value, don't turn. This prevents visual jitter.")]
+		public readonly WAngle TurnDeadzone = new(2);
+
 		[Desc("Maximum flight speed when cruising.")]
 		public readonly int Speed = 1;