From 59f5e241898d834d7ef652b1e0f090155194f5b3 Mon Sep 17 00:00:00 2001
From: Paul Chote <pchote@users.noreply.github.com>
Date: Sat, 23 Apr 2016 17:14:04 +0100
Subject: [PATCH] Simplify and fix missile turnaround facing check.

---
 OpenRA.Mods.Common/Effects/Missile.cs | 3 ++-
 OpenRA.Mods.Common/Util.cs            | 8 ++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/OpenRA.Mods.Common/Effects/Missile.cs b/OpenRA.Mods.Common/Effects/Missile.cs
index 871db3501e..76781a0613 100644
--- a/OpenRA.Mods.Common/Effects/Missile.cs
+++ b/OpenRA.Mods.Common/Effects/Missile.cs
@@ -712,7 +712,8 @@ namespace OpenRA.Mods.Common.Effects
 			var velVec = tarDistVec + predVel;
 			var desiredHFacing = velVec.HorizontalLengthSquared != 0 ? velVec.Yaw.Facing : hFacing;
 
-			if (allowPassBy && Math.Abs((desiredHFacing - hFacing) & 0xFF) >= Math.Abs((desiredHFacing + 128 - hFacing) & 0xFF))
+			var delta = Util.NormalizeFacing(hFacing - desiredHFacing);
+			if (allowPassBy && delta > 64 && delta < 192)
 			{
 				desiredHFacing = (desiredHFacing + 128) & 0xFF;
 				targetPassedBy = true;
diff --git a/OpenRA.Mods.Common/Util.cs b/OpenRA.Mods.Common/Util.cs
index 926155a13c..54a3ccc538 100644
--- a/OpenRA.Mods.Common/Util.cs
+++ b/OpenRA.Mods.Common/Util.cs
@@ -73,6 +73,14 @@ namespace OpenRA.Mods.Common
 			}
 		}
 
+		public static int NormalizeFacing(int f)
+		{
+			if (f >= 0)
+				return f & 0xFF;
+
+			return 0xFF - (-f & 0xFF);
+		}
+
 		public static WPos BetweenCells(World w, CPos from, CPos to)
 		{
 			return WPos.Lerp(w.Map.CenterOfCell(from), w.Map.CenterOfCell(to), 1, 2);