import(): AMF, X3D and VRML97; a .pdf or malformed SVG no longer hangs

[revarbat]

import() now reads AMF, X3D and VRML97, the three multi-object formats export writes that nothing could read back. Current upstream OpenSCAD removed its AMF importer (bf7a0970b), so all three go beyond it.

Geometry only, like the STL/OBJ/OFF/3MF loaders, but each format's scene structure is honoured:

• X3D and VRML97
  • Transforms nest and apply in full: translation, rotation, scale, center and scaleOrientation (T·C·R·SR·S·SR⁻¹·C⁻¹).
  • DEF/USE resolves, and ccw FALSE flips winding.
  • IndexedFaceSet polygons are fan-triangulated; a last polygon without -1 still counts.
  • X3D also reads IndexedTriangleSet and TriangleSet.
  • X3D goes through a small real XML parser (comments, CDATA, DOCTYPE, entities). VRML goes through a tokenizer and generic node parser that steps over PROTO, EXTERNPROTO and ROUTE; VRML 1.0 is refused by name.
• AMF: plain or zipped (read like 3MF), with unit (inch, feet, metre, micron) scaled to mm.
• What isn't a mesh (X3D/VRML primitives, Inline, AMF constellations) is skipped with a warning, import: '<file>': skipped what is not a mesh: 1 Box, from both the geometry and expression forms of import().

Tested (8 new tests):

• Round trips: our own AMF, X3D and VRML exports import back at exact volume.
• Hand-written X3D: a scaled cube, the same cube reused with USE under a rotation, a tetrahedron with ccw="false" and a Box. Expected and got a volume of 13.5, the right bounding box, and the Box warning.
• Hand-written VRML: the same scene plus PROTO/ROUTE/comments. Expected and got volume 9, and a maximum x of 30, which proves the rotation applied.
• AMF in inches, plain and zipped: exactly 25.4³, plus the constellation warning.
• Errors: a face index past its points is an error.

Suites: all 1346 C++ tests pass, all 61 binding tests pass, and BelfrySCAD's full suite (2187) passes against this build.

Also fixes an import() hang. The SVG parser's attribute loop stopped on a character no attribute can start with (a / not followed by >, a stray =) without consuming it, then came back to it forever. A PDF is full of /Name, so import("x.pdf") (routed to the SVG parser) hung for good, and so did a malformed SVG like <a / b>. The loop now steps past such a character, and .pdf is no longer routed to the SVG parser: nothing reads PDF (OpenSCAD doesn't either), so it gets the ordinary "unsupported file type" error. Both files that hung now fail in under half a second, and 3 new tests cover them.

🤖 Generated with Claude Code