Function box_from_compound

src/serializers/SvgSerializer.cpp:436–487

	};

	boost::optional<box_t> box_from_compound(TopoDS_Shape& compound) {
		/*
		// in v0.8 apparently we don't get a solid/shell anymore because
		// we no longer use PrimAPI, but rather resolve the box to an
		// explicit shell with 6 faces in the mapping, which - depending 
		// on settings - may remain solely a compound of 6.

		TopExp_Explorer exp(compound, TopAbs_SHELL);
		TopoDS_Shell shell;
		if (exp.More()) {
			shell = TopoDS::Shell(exp.Current());
			exp.Next();
			if (exp.More()) {
				return boost::none;
			}
		}
		else {
			return boost::none;
		}
		*/
		auto& shell = compound;

		if (IfcGeom::util::count(shell, TopAbs_FACE) != 6) {
			return boost::none;
		}

		TopExp_Explorer it(shell, TopAbs_FACE);
		for (; it.More(); it.Next()) {
			const auto& face = TopoDS::Face(it.Current());
			auto surf = BRep_Tool::Surface(face);
			if (surf->DynamicType() != STANDARD_TYPE(Geom_Plane)) {
				return boost::none;
			}
			auto pln = Handle(Geom_Plane)::DownCast(surf);
			auto dz = std::abs(pln->Position().Direction().Z());
			if (almost(0.) != dz && almost(1.) != dz) {
				return boost::none;
			}
			auto dy = std::abs(pln->Position().Direction().Y());
			if (almost(0.) != dy && almost(1.) != dy) {
				return boost::none;
			}
		}

		Bnd_Box b;
		BRepBndLib::Add(compound, b, false);

		double x0, y0, z0, x1, y1, z1;
		b.Get(x0, y0, z0, x1, y1, z1);

		return box_t{ {{x0, y0, z0}}, {{x1, y1, z1}} };
	}

	struct string_property {
		std::string pset_name, prop_name, value;