Check in patch from zeromus that provides back end support for custom Axis constraints for analog input

BizHawk.Client.Common/ControllerBinding.cs

@@ -132,6 +132,11 @@ namespace BizHawk.Client.Common
 			}
 		}
 
+		public void ApplyAxisConstraints(string constraintClass)
+		{
+			_type.ApplyAxisConstraints(constraintClass,_floatButtons);
+		}
+
 		/// <summary>
 		/// merges pressed logical buttons from the supplied controller, effectively ORing it with the current state
 		/// </summary>

BizHawk.Client.EmuHawk/MainForm.cs

@@ -427,8 +427,12 @@ namespace BizHawk.Client.EmuHawk
 				// handle events and dispatch as a hotkey action, or a hotkey button, or an input button
 				ProcessInput();
 				Global.ClientControls.LatchFromPhysical(GlobalWin.HotkeyCoalescer);
+
 				Global.ActiveController.LatchFromPhysical(Global.ControllerInputCoalescer);
 
+				//TODO - use preferences to apply this
+				Global.ActiveController.ApplyAxisConstraints("Natural Circle");
+
 				Global.ActiveController.OR_FromLogical(Global.ClickyVirtualPadController);
 				Global.ActiveController.Overrides(Global.LuaAndAdaptor);
 				Global.AutoFireController.LatchFromPhysical(Global.ControllerInputCoalescer);

BizHawk.Emulation.Common/Interfaces/IController.cs

@@ -17,6 +17,38 @@ namespace BizHawk.Emulation.Common
 
 	public class ControllerDefinition
 	{
+		public void ApplyAxisConstraints(string constraintClass, IDictionary<string, float> floatButtons)
+		{
+			if (AxisConstraints == null) return;
+
+			foreach (var constraint in AxisConstraints)
+			{
+				if (constraint.Class != constraintClass)
+					continue;
+				switch (constraint.Type)
+				{
+					case AxisConstraintType.Circular:
+					{
+						string xaxis = constraint.Params[0] as string;
+						string yaxis = constraint.Params[1] as string;
+						float range = (float)constraint.Params[2];
+						double xval = floatButtons[xaxis];
+						double yval = floatButtons[yaxis];
+						double length = Math.Sqrt(xval * xval + yval * yval);
+						if (length > range)
+						{
+							double ratio = range / length;
+							xval *= ratio;
+							yval *= ratio;
+						}
+						floatButtons[xaxis] = (float)xval;
+						floatButtons[yaxis] = (float)yval;
+						break;
+					}
+				}
+			}
+		}
+
 		public struct FloatRange
 		{
 			public readonly float Min;
@@ -46,11 +78,24 @@ namespace BizHawk.Emulation.Common
 			}
 		}
 
+		public enum AxisConstraintType
+		{
+			Circular
+		}
+
+		public struct AxisConstraint
+		{
+			public string Class;
+			public AxisConstraintType Type;
+			public object[] Params;
+		}
+
 		public string Name { get; set; }
 
 		public List<string> BoolButtons { get; set; }
 		public List<string> FloatControls { get; private set; }
 		public List<FloatRange> FloatRanges { get; private set; }
+		public List<AxisConstraint> AxisConstraints { get; private set; }
 		
 		public ControllerDefinition(ControllerDefinition source)
 			: this()
@@ -59,6 +104,7 @@ namespace BizHawk.Emulation.Common
 			BoolButtons.AddRange(source.BoolButtons);
 			FloatControls.AddRange(source.FloatControls);
 			FloatRanges.AddRange(source.FloatRanges);
+			AxisConstraints.AddRange(source.AxisConstraints);
 		}
 
 		public ControllerDefinition()
@@ -66,6 +112,7 @@ namespace BizHawk.Emulation.Common
 			BoolButtons = new List<string>();
 			FloatControls = new List<string>();
 			FloatRanges = new List<FloatRange>();
+			AxisConstraints = new List<AxisConstraint>();
 		}
 	}
 

BizHawk.Emulation.Cores/Consoles/Nintendo/N64/N64Input.cs

@@ -41,6 +41,10 @@ namespace BizHawk.Emulation.Cores.Nintendo.N64
 				new[] {127.0f, 0.0f, -128.0f},
 				new[] {-128.0f, 0.0f, 127.0f},
 				new[] {127.0f, 0.0f, -128.0f}
+			},
+			AxisConstraints =
+			{
+				new ControllerDefinition.AxisConstraint { Class = "Natural Circle", Type = ControllerDefinition.AxisConstraintType.Circular, Params = new object[] {"P1 X Axis", "P1 Y Axis", 127.0f} }
 			}
 		};