awaforge

fontTag

AGPL-3.0-onlyRelease 2L4

OpenType Tag — 4-char ASCII identifier ↔ uint32 BE.

Module fontTag | Source packages/front/office/fonts/src/primitives/tag.js | Deps fontErrors | Worker-safe yes

Tags such as 'head', 'glyf', 'OS/2', 'cvt ' (with a trailing space) appear in the SFNT directory, the GSUB/GPOS feature/script lists, fvar axes, etc.

Resolve

const { tag, untag, tagEquals } = runtime.resolve('fontTag');

API

Method Signature Returns
tag (s: string) => number Packs a 4-char ASCII string into a BE uint32.
untag (u32: number) => string Unpacks a uint32 into a 4-char string.
tagEquals (a: string|number, b: string|number) => boolean Compares two heterogeneous tags.

Examples

const { tag, untag } = runtime.resolve('fontTag');
tag('head');           // 0x68656164
untag(0x68656164);     // 'head'
tag('OS/2');           // 0x4F532F32

Notes

  • tag('xyz') (length ≠ 4) throws ContractError('fonts/bad-tag').
  • A space-padded tag ('cvt ') is valid — the space is part of the binary tag.

See also