Mirrors selected helpers from ifcopenshell.util.unit: SI prefix
multipliers, the conversion-based-unit table (foot/inch/etc -> SI
metres), siScaleFromNamedUnit (walks IfcConversionBasedUnit chains
down to IfcSIUnit), getUnitAssignment / getProjectUnit /
calculateUnitScale, and convert / convertUnit. Lives in
src/ifcviewer/ for now alongside Geolocation; will move out when
ifcopenshell.util is ported to C++.
Needed by upcoming Geolocation fix (e/n/h on IfcMapConversion are
in MapUnit, must be converted to metres for the meter-by-default
iterator output) and by the federation module (display-unit
conversion when the user changes the federation unit).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Dion Moult