From a0c8f722d2a1e2192b7599bdc66fbdf1164fd4f6 Mon Sep 17 00:00:00 2001
From: YoshiRulz <OSSYoshiRulz@gmail.com>
Date: Fri, 26 Jun 2020 08:53:10 +1000
Subject: [PATCH] Use constraints for grouping, add new class for unconstrained
 pairs

e.g. for Intellivision `_controllerDeck.Definition.Axes["P1 Disc X"].PairedAxis`
gives "P1 Disc Y"
---
 .../Base Implementations/ControllerDefinition.cs      | 11 +++++++++++
 src/BizHawk.Emulation.Common/Extensions.cs            |  8 ++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/BizHawk.Emulation.Common/Base Implementations/ControllerDefinition.cs b/src/BizHawk.Emulation.Common/Base Implementations/ControllerDefinition.cs
index 0eb02839de..29268c8f19 100644
--- a/src/BizHawk.Emulation.Common/Base Implementations/ControllerDefinition.cs	
+++ b/src/BizHawk.Emulation.Common/Base Implementations/ControllerDefinition.cs	
@@ -113,6 +113,8 @@ namespace BizHawk.Emulation.Common
 
 			public int Min => Range.Start;
 
+			public string PairedAxis => Constraint?.PairedAxis;
+
 			public readonly Range<int> Range;
 
 			public AxisSpec(Range<int> range, int mid, bool isReversed = false, AxisConstraint constraint = null)
@@ -164,6 +166,15 @@ namespace BizHawk.Emulation.Common
 			public string PairedAxis { get; }
 		}
 
+		public sealed class NoOpAxisConstraint : AxisConstraint
+		{
+			public string Class { get; } = null;
+
+			public string PairedAxis { get; }
+
+			public NoOpAxisConstraint(string pairedAxis) => PairedAxis = pairedAxis;
+		}
+
 		public sealed class CircularAxisConstraint : AxisConstraint
 		{
 			public string Class { get; }
diff --git a/src/BizHawk.Emulation.Common/Extensions.cs b/src/BizHawk.Emulation.Common/Extensions.cs
index afca4013f7..46990dde17 100644
--- a/src/BizHawk.Emulation.Common/Extensions.cs
+++ b/src/BizHawk.Emulation.Common/Extensions.cs
@@ -420,8 +420,12 @@ namespace BizHawk.Emulation.Common
 		/// <param name="nameFormat">format string e.g. <c>"P1 Left {0}"</c> (will be used to interpolate <c>"X"</c> and <c>"Y"</c>)</param>
 		/// <returns>identical reference to <paramref name="def"/>; the object is mutated</returns>
 		public static ControllerDefinition AddXYPair(this ControllerDefinition def, string nameFormat, AxisPairOrientation pDir, Range<int> rangeX, int midX, Range<int> rangeY, int midY, AxisConstraint constraint = null)
-			=> def.AddAxis(string.Format(nameFormat, "X"), rangeX, midX, ((byte) pDir & 2) != 0, constraint)
-				.AddAxis(string.Format(nameFormat, "Y"), rangeY, midY, ((byte) pDir & 1) != 0);
+		{
+			var yAxisName = string.Format(nameFormat, "Y");
+			var finalConstraint = constraint ?? new NoOpAxisConstraint(yAxisName);
+			return def.AddAxis(string.Format(nameFormat, "X"), rangeX, midX, ((byte) pDir & 2) != 0, finalConstraint)
+				.AddAxis(yAxisName, rangeY, midY, ((byte) pDir & 1) != 0);
+		}
 
 		/// <summary>
 		/// Adds an X/Y pair of axes to the receiver <see cref="ControllerDefinition"/>, and returns it.