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This commit is contained in:
Jason Stedwell
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"""
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loader.py — STEP file loading with build123d primary and FreeCAD fallback.
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Returns a StepModel dataclass used by all other modules.
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FreeCAD fallback invokes the signed app bundle Python to avoid
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Gatekeeper issues on macOS 15 Sequoia.
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"""
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import json
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import logging
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import subprocess
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import tempfile
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from dataclasses import dataclass, field
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from pathlib import Path
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from typing import Any, Optional
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logger = logging.getLogger("step_processor.loader")
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FREECAD_PYTHON = "/Applications/FreeCAD.app/Contents/Resources/bin/python"
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FREECAD_LIB = "/Applications/FreeCAD.app/Contents/Resources/lib"
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FREECAD_CMD = "/Applications/FreeCAD.app/Contents/Resources/bin/freecadcmd"
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@dataclass
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class StepModel:
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"""Unified model object returned by load_step(). Used by all modules."""
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shape: Any
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backend: str # "build123d" | "freecad"
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path: Path
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parts: list = field(default_factory=list)
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face_count: int = 0
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metadata: dict = field(default_factory=dict)
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def load_step(filepath) -> Optional["StepModel"]:
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"""Load a STEP file. Tries build123d first; falls back to FreeCAD."""
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step_path = Path(filepath).expanduser().resolve()
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if not step_path.exists():
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logger.error(f"File not found: {step_path}")
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return None
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try:
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return _load_via_build123d(step_path)
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except ImportError:
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logger.warning("build123d not available — falling back to FreeCAD")
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return _load_via_freecad(step_path)
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except Exception as e:
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logger.warning(f"build123d failed ({type(e).__name__}: {e}) — falling back to FreeCAD")
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return _load_via_freecad(step_path)
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def _load_via_build123d(step_path: Path) -> "StepModel":
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"""Load using build123d. Raises on failure."""
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from build123d import import_step
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logger.info(f"[build123d] Loading: {step_path.name}")
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shape = import_step(str(step_path))
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face_count = 0
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try:
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face_count = sum(1 for _ in shape.faces())
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except Exception:
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pass
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parts = _extract_parts_build123d(shape)
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logger.info(f"[build123d] Loaded: {step_path.name} | {face_count} faces | {len(parts)} parts")
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return StepModel(shape=shape, backend="build123d", path=step_path,
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parts=parts, face_count=face_count)
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def _fix_gbk_mojibake(s: str) -> str:
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"""
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Recover Chinese text stored as mojibake in STEP part labels.
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STEP files from Chinese CAD tools (SolidWorks CN, etc.) embed raw GBK bytes
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in PRODUCT name strings. OpenCASCADE reads STEP strings as latin-1, which
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re-interprets those GBK bytes as latin-1 code points — classic mojibake.
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Fix: re-encode the string to latin-1 (restoring the original GBK byte
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sequence) then decode as GBK to get correct Unicode Chinese characters.
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If the string is pure ASCII, or the round-trip fails (already valid Unicode
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or a non-GBK extended char), returns the original string unchanged.
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"""
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if not s or all(ord(c) < 128 for c in s):
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return s # pure ASCII: nothing to fix
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try:
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return s.encode('latin-1').decode('gbk')
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except (UnicodeDecodeError, UnicodeEncodeError):
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return s # not GBK mojibake — leave original
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def _extract_parts_build123d(shape) -> list:
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"""Walk build123d compound tree and extract named parts."""
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parts = []
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def _walk(compound, level=0, parent_name=""):
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children = []
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try:
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children = compound.children if hasattr(compound, "children") else []
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except Exception:
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pass
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if children:
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for child in children:
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raw = (getattr(child, "label", "") or
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getattr(child, "name", "") or f"Part_{level}")
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name = _fix_gbk_mojibake(raw)
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parts.append({"name": name, "level": level, "parent": parent_name})
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_walk(child, level + 1, name)
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else:
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raw = (getattr(compound, "label", "") or
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getattr(compound, "name", "") or "")
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if raw:
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name = _fix_gbk_mojibake(raw)
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parts.append({"name": name, "level": level, "parent": parent_name})
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_walk(shape)
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return parts
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def _load_via_freecad(step_path: Path) -> Optional["StepModel"]:
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"""Load using FreeCAD app bundle Python via subprocess."""
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if not Path(FREECAD_PYTHON).exists():
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logger.error(f"FreeCAD Python not found at {FREECAD_PYTHON}. Install FreeCAD.app.")
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return None
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logger.info(f"[FreeCAD] Loading: {step_path.name}")
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script = f"""
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import sys, json
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sys.path.insert(0, {repr(FREECAD_LIB)})
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import FreeCAD, Part
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try:
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shape = Part.read({repr(str(step_path))})
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bb = shape.BoundBox
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sub = shape.SubShapes if hasattr(shape, 'SubShapes') else []
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parts = [{{"name": f"Part_{{i}}", "level": 1, "parent": "root"}}
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for i in range(len(sub))]
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print(json.dumps({{"ok": True, "face_count": len(shape.Faces),
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"parts": parts,
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"bbox": {{"XMin": bb.XMin, "XMax": bb.XMax,
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"YMin": bb.YMin, "YMax": bb.YMax,
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"ZMin": bb.ZMin, "ZMax": bb.ZMax}}}}))
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except Exception as e:
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print(json.dumps({{"ok": False, "error": str(e)}}))
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"""
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with tempfile.NamedTemporaryFile(mode="w", suffix=".py", delete=False) as f:
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f.write(script)
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script_path = f.name
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try:
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proc = subprocess.run([FREECAD_PYTHON, script_path],
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capture_output=True, text=True, timeout=120)
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json_line = next((l.strip() for l in proc.stdout.splitlines()
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if l.strip().startswith("{")), None)
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if not json_line:
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logger.error(f"[FreeCAD] No JSON output. stderr: {proc.stderr[:300]}")
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return None
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data = json.loads(json_line)
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if not data.get("ok"):
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logger.error(f"[FreeCAD] Load failed: {data.get('error')}")
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return None
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proxy = _FreeCADShapeProxy(data["bbox"], data["face_count"])
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logger.info(f"[FreeCAD] Loaded: {step_path.name} | {data['face_count']} faces")
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return StepModel(shape=proxy, backend="freecad", path=step_path,
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parts=data.get("parts", []),
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face_count=data["face_count"],
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metadata={"bbox": data["bbox"]})
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except subprocess.TimeoutExpired:
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logger.error("[FreeCAD] Load timed out after 120s")
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return None
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except Exception as e:
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logger.error(f"[FreeCAD] Unexpected error: {e}")
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return None
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finally:
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Path(script_path).unlink(missing_ok=True)
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class _FreeCADShapeProxy:
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"""Proxy carrying FreeCAD geometry data extracted via subprocess."""
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def __init__(self, bbox_dict: dict, face_count: int):
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self.BoundBox = _BoundBox(bbox_dict)
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self.face_count = face_count
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self.Faces = [None] * face_count
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def faces(self):
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for _ in range(self.face_count):
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yield object()
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class _BoundBox:
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def __init__(self, d: dict):
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self.XMin = d.get("XMin", 0); self.XMax = d.get("XMax", 0)
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self.YMin = d.get("YMin", 0); self.YMax = d.get("YMax", 0)
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self.ZMin = d.get("ZMin", 0); self.ZMax = d.get("ZMax", 0)
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