HarfBuzz Text Shaping Engine

HarfBuzz is a text shaping library that converts a sequence of Unicode codepoints into a sequence of correctly positioned glyph indices with proper ligatures, contextual alternates, and complex script handling. Developed by Behdad Esfahbod and Jonathan Kew since 2009, HarfBuzz has become the industry-standard text shaping engine used by Firefox, Chrome, Android, iOS, Linux, LibreOffice, Inkscape, and virtually every modern text rendering stack. Key features include: OpenType shaping (full OpenType Layout table support including GSUB for substitution and GPOS for positioning, handling ligatures, contextual alternates, kerning, mark positioning, and chaining context rules), complex script support (Arabic, Hebrew, Indic Devanagari, Bengali, Gurmukhi, Gujarati, Tamil, Telugu, Kannada, Malayalam, Thai, Lao, Tibetan, Khmer, and Myanmar with per-script shaping engines), AAT shaping (Apple Advanced Typography support for macOS and iOS compatibility), vertical text (CJK vertical layout with vertical alternates and proper punctuation positioning), color fonts (COLR/CPAL layered color glyphs, SBIX bitmap, and SVG glyph support), variable fonts (OpenType variation with axis-aware shaping), fallback shaping (basic Latin shaping when no OpenType tables are present), Unicode normalization (canonical decomposition and composition for combining characters), cluster level control (monotone, character, and grapheme cluster levels), language and script detection (automatic script detection and explicit language tagging), font functions (pluggable font backends for FreeType, CoreText, and DirectWrite), WASM compilation (WebAssembly with hbjs bindings for browser-based text shaping), and high performance (SIMD-accelerated lookup caching and sublinear shaping complexity).