Invert Y on the wire, not in the router: the panel keeps tracking the stick

InputRouter.InvertJoystickY flipped the stored axis, so the X/Y dot and
readout moved opposite the physical stick. The toggle now lives on
VRioDevice and negates joystick Y only while building AnalogReply: local
state keeps the physical direction for every source (pad, keys, panel
drags) and only the host sees the flip. Negating a full -8192 deflection
lands one past the 14-bit Max, so the reply clamps it to 8191.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/VRio.App/MainForm.cs

@@ -190,8 +190,8 @@ internal sealed class MainForm : Form
             if (!_kbInput.Checked)
                 _router.ReleaseAllKeys();
         };
-        _invertY.CheckedChanged += (_, _) => _router.InvertJoystickY = _invertY.Checked;
+        _invertY.CheckedChanged += (_, _) => _device.InvertJoystickY = _invertY.Checked;
-        _router.InvertJoystickY = _invertY.Checked; // the field initializer raises no event
+        _device.InvertJoystickY = _invertY.Checked; // the field initializer raises no event
         _kbLights.CheckedChanged += (_, _) =>
         {
             _lampMirror.Enabled = _kbLights.Checked;

src/VRio.Core/Device/VRioDevice.cs

@@ -57,6 +57,13 @@ public sealed class VRioDevice
     /// <summary>Firmware version reported by VersionReply (real boards run 4.2).</summary>
     public byte VersionMinor { get; set; } = 2;
 
+    /// <summary>
+    /// Negate joystick Y in AnalogReply. Only the host sees the flip — local
+    /// state (<see cref="GetAxis"/>, the panel's dot and readout) keeps the
+    /// physical stick direction.
+    /// </summary>
+    public bool InvertJoystickY { get; set; }
+
     /// <summary>
     /// When true, retry exhaustion leaves the analog reply path wedged (the
     /// v4.2 latch-leak bug) until a host ResetRequest clears it.
@@ -274,6 +281,8 @@ public sealed class VRioDevice
                     y = _axes[(int)RioAxis.JoystickY];
                     x = _axes[(int)RioAxis.JoystickX];
                 }
+                if (InvertJoystickY) // clamp: -Min (8192) is one past the 14-bit Max
+                    y = (short)Math.Min(AnalogCodec.Max, -y);
                 Send(PacketBuilder.AnalogReply(t, l, r, y, x));
                 break;
 

src/VRio.Core/Input/InputRouter.cs

@@ -57,13 +57,6 @@ public sealed class InputRouter
     /// <summary>A routed address went down (true) or came back up (false) — for panel highlighting.</summary>
     public event Action<int, bool>? AddressHeldChanged;
 
-    /// <summary>
-    /// Flip the sign of the composed joystick Y before it reaches the device.
-    /// Applies to all routed sources (keys and pad) alike; panel drags write
-    /// the device directly and are unaffected.
-    /// </summary>
-    public bool InvertJoystickY { get; set; }
-
     /// <summary>
     /// The active bindings. Assigning releases everything currently held
     /// (keys, toggles, pad buttons) so a reload never strands a pressed input.
@@ -223,8 +216,6 @@ public sealed class InputRouter
                 if (b.Rate <= 0f)
                     total += Shape(_pad.Axis(b.Source), b);
             }
-            if (InvertJoystickY && axis == RioAxis.JoystickY)
-                total = -total;
             total = ClampNorm(axis, total);
 
             short raw = (short)Math.Round(total * RioAxisRange.Full(axis));

tests/VRio.Core.Tests/InputRouterTests.cs

@@ -191,26 +191,6 @@ public class InputRouterTests
         Assert.Equal(0, _device.GetAxis(RioAxis.JoystickY));
     }
 
-    [Fact]
-    public void InvertJoystickY_flips_the_composed_value_for_all_sources()
-    {
-        UseProfile("key Up axis JoystickY deflect 1\npadaxis LeftStickY axis JoystickY");
-        _router.InvertJoystickY = true;
-
-        _router.KeyDown("Up");
-        _router.Tick(0.016);
-        Assert.Equal(-RioAxisRange.JoystickExtent, _device.GetAxis(RioAxis.JoystickY));
-        _router.KeyUp("Up");
-
-        _router.SetPadState(new PadState(PadButtons.None, 0, 0.5f, 0, 0, 0, 0));
-        _router.Tick(0.016);
-        Assert.Equal(-RioAxisRange.JoystickExtent / 2, _device.GetAxis(RioAxis.JoystickY));
-
-        _router.InvertJoystickY = false; // toggling back re-sends the upright value
-        _router.Tick(0.016);
-        Assert.Equal(RioAxisRange.JoystickExtent / 2, _device.GetAxis(RioAxis.JoystickY));
-    }
-
     [Fact]
     public void Rate_key_walks_the_throttle_and_position_sticks()
     {

tests/VRio.Core.Tests/VRioDeviceTests.cs

@@ -66,6 +66,27 @@ public class VRioDeviceTests
         Assert.Equal(1, device.AnalogRequests);
     }
 
+    [Fact]
+    public void InvertJoystickY_flips_the_wire_but_not_local_state()
+    {
+        var device = new VRioDevice { InvertJoystickY = true };
+        var wire = new Wire(device);
+        device.SetAxis(RioAxis.JoystickY, 3000);
+
+        Send(device, PacketBuilder.Build(RioCommand.AnalogRequest));
+
+        byte[] p = Assert.Single(wire.Packets).Payload;
+        Assert.Equal(-3000, AnalogCodec.Combine(p[6], p[7]));
+        Assert.Equal(3000, device.GetAxis(RioAxis.JoystickY)); // the panel's view is unflipped
+
+        // Full negative deflection: -Min is one past Max, so it clamps rather than throws.
+        device.SetAxis(RioAxis.JoystickY, AnalogCodec.Min);
+        wire.Clear();
+        Send(device, PacketBuilder.Build(RioCommand.AnalogRequest));
+        p = Assert.Single(wire.Packets).Payload;
+        Assert.Equal(AnalogCodec.Max, AnalogCodec.Combine(p[6], p[7]));
+    }
+
     [Fact]
     public void VersionRequest_reports_configured_firmware()
     {