visualGlyphs
Orders and shapes a complete logical line while preserving original UTF-16 scalar positions for font lookup. Shaping spans the whole line, including font boundaries, and contractions belong to their first contributing scalar. Original positions deliberately correct the native style lookup drift after Arabic contractions without changing the shaped glyphs. The default supplies identity order and replaces unmatched UTF-16 surrogates with the replacement scalar. Backends providing native bidirectional processing must override this operation alongside visualOrder.
Return
detached immutable visual glyphs with UTF-16 scalar offsets into the original logical line.
Parameters
immutable logical text, potentially containing several font spans.
whether the fallback paragraph direction is right-to-left.