HarfBuzz shaping and Unicode text algorithms

Document status: reviewed. Canonical source.

Summary

HarfBuzz maps Unicode code points to ordered glyph IDs, clusters, advances and offsets based on font data and shaping rules. Unicode UAX #9/#14/#29 define bidi, line-break and segmentation foundations, but actual line choice and font rendering remain higher-level concerns.

NUIF relevance

Canonical documents store semantic text, runs, font references and layout intent. Shaped glyph runs are resolved/cache data tied to evaluator context and font hashes; they must not replace source text.