From 319a65bd0b49e47fb4fcf2dd37be46f88fa29caa Mon Sep 17 00:00:00 2001
From: Gavin Colonese <gcolonese@kitchenbrains.com>
Date: Mon, 18 May 2026 13:39:26 -0400
Subject: [PATCH] Fix: IPC handlers now convert inch units to mm for position
 commands (#158)

The _ipc_move_component and _ipc_place_component handlers were ignoring
the unit field from position parameters, always treating values as mm.
When inches were specified, components would be placed at 1/25.4th of
the intended position. Now reads the unit field and converts to mm
before passing to the IPC backend.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 python/kicad_interface.py                  | 12 +++
 tests/test_ipc_position_inch_conversion.py | 89 ++++++++++++++++++++++
 2 files changed, 101 insertions(+)
 create mode 100644 tests/test_ipc_position_inch_conversion.py

diff --git a/python/kicad_interface.py b/python/kicad_interface.py
index 55334ca..88d69b9 100644
--- a/python/kicad_interface.py
+++ b/python/kicad_interface.py
@@ -5003,10 +5003,16 @@ print("ok")
             position = params.get("position", {})
             x = position.get("x", 0) if isinstance(position, dict) else params.get("x", 0)
             y = position.get("y", 0) if isinstance(position, dict) else params.get("y", 0)
+            unit = position.get("unit", "mm") if isinstance(position, dict) else "mm"
             rotation = params.get("rotation", 0)
             layer = params.get("layer", "F.Cu")
             value = params.get("value", "")
 
+            # Convert inches to mm since ipc_backend expects mm
+            if unit == "inch":
+                x = x * 25.4
+                y = y * 25.4
+
             success = self.ipc_board_api.place_component(
                 reference=reference,
                 footprint=footprint,
@@ -5043,8 +5049,14 @@ print("ok")
             position = params.get("position", {})
             x = position.get("x", 0) if isinstance(position, dict) else params.get("x", 0)
             y = position.get("y", 0) if isinstance(position, dict) else params.get("y", 0)
+            unit = position.get("unit", "mm") if isinstance(position, dict) else "mm"
             rotation = params.get("rotation")
 
+            # Convert inches to mm since ipc_backend.move_component expects mm
+            if unit == "inch":
+                x = x * 25.4
+                y = y * 25.4
+
             success = self.ipc_board_api.move_component(
                 reference=reference, x=x, y=y, rotation=rotation
             )
diff --git a/tests/test_ipc_position_inch_conversion.py b/tests/test_ipc_position_inch_conversion.py
new file mode 100644
index 0000000..f2ac6be
--- /dev/null
+++ b/tests/test_ipc_position_inch_conversion.py
@@ -0,0 +1,89 @@
+"""Regression test for inch-unit conversion in IPC place/move handlers.
+
+Bug: ``_ipc_place_component`` and ``_ipc_move_component`` ignored the
+``unit`` field in ``position`` and forwarded the values directly to the IPC
+backend, which expects mm. Calling with ``unit="inch"`` placed the part at
+1/25.4 of the intended position. The fix reads ``unit`` and converts inches
+→ mm before invoking ``self.ipc_board_api.*``.
+"""
+
+import sys
+from pathlib import Path
+from typing import Any
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "python"))
+
+
+def _make_iface() -> Any:
+    """Build a stripped-down KiCADInterface with a mock ipc_board_api."""
+    with patch("kicad_interface.USE_IPC_BACKEND", True):
+        from kicad_interface import KiCADInterface
+
+        iface = KiCADInterface.__new__(KiCADInterface)
+
+    iface.use_ipc = True
+    iface.board = None
+    iface.ipc_board_api = MagicMock()
+    iface.ipc_board_api.place_component.return_value = True
+    iface.ipc_board_api.move_component.return_value = True
+    return iface
+
+
+def test_place_component_converts_inches_to_mm():
+    iface = _make_iface()
+    iface._ipc_place_component(
+        {
+            "reference": "R1",
+            "footprint": "Resistor_SMD:R_0805",
+            "position": {"x": 1, "y": 2, "unit": "inch"},
+            "rotation": 0,
+            "layer": "F.Cu",
+            "value": "220",
+        }
+    )
+
+    args, kwargs = iface.ipc_board_api.place_component.call_args
+    assert kwargs["x"] == pytest.approx(25.4)
+    assert kwargs["y"] == pytest.approx(50.8)
+
+
+def test_place_component_passes_mm_unchanged():
+    iface = _make_iface()
+    iface._ipc_place_component(
+        {
+            "reference": "R1",
+            "footprint": "Resistor_SMD:R_0805",
+            "position": {"x": 25.4, "y": 50.8, "unit": "mm"},
+            "rotation": 0,
+            "layer": "F.Cu",
+            "value": "220",
+        }
+    )
+    args, kwargs = iface.ipc_board_api.place_component.call_args
+    assert kwargs["x"] == 25.4
+    assert kwargs["y"] == 50.8
+
+
+def test_move_component_converts_inches_to_mm():
+    iface = _make_iface()
+    iface._ipc_move_component(
+        {
+            "reference": "R1",
+            "position": {"x": 1, "y": 0.5, "unit": "inch"},
+        }
+    )
+    args, kwargs = iface.ipc_board_api.move_component.call_args
+    assert kwargs["x"] == pytest.approx(25.4)
+    assert kwargs["y"] == pytest.approx(12.7)
+
+
+def test_default_unit_is_mm():
+    """Omitting unit defaults to mm — values pass through unchanged."""
+    iface = _make_iface()
+    iface._ipc_move_component({"reference": "R1", "position": {"x": 10, "y": 20}})
+    args, kwargs = iface.ipc_board_api.move_component.call_args
+    assert kwargs["x"] == 10
+    assert kwargs["y"] == 20