Expand description
Shared conformance checks for portable visible-face providers.
Like the hidden-line suite, it calls the provider directly, so a provider must refuse bad input itself. Each exact case states the regions it must return, bit for bit; the area cases state the area per source where the coordinates are not binary64; the snap cases are scenes that binary64 rounding used to refuse and that must now be answered, with the snapping in the evidence. Every outcome is also checked for shape (ring orientation and start, sort order, triangle lists, caps, evidence). The scenes and the arithmetic behind them are in the (private) fixtures, checked by their own unit tests.