awaforge

tableCff2

AGPL-3.0-onlyRelease 2L4

Table CFF2 — Compact Font Format 2, the variable-aware outline container (OT §10.2).

Module tableCff2 | Source packages/front/office/fonts/src/table/cff2.js | Deps fontErrors, fontReader, tableCffDict | Worker-safe yes

Reads the CFF2 header, the single Top DICT, the Global Subr INDEX, the CharStrings INDEX and the location of the Item Variation Store. CFF2 differs from CFF: there is no Name, String, Encoding or Charset data (names live in name), the Top DICT is one block rather than an INDEX, and every INDEX carries a uint32 count.

Exports

Symbol Type Description
parseCff2 function (bytes: Uint8Array) => { majorVersion, minorVersion, headerSize, topDictLength, topDict, globalSubrIndex, charStringsIndex, vstore, fdArray, vstoreOffset?, vstoreBytes? }. topDict is a Map<operator, operand[]>; charStringsIndex is null when the Top DICT has no single-offset CharStrings entry; vstore and fdArray are always null; vstoreOffset and vstoreBytes are present only when the Top DICT carries a vstore offset.
parseCff2Index function (r: BinaryReader) => { count, offSize, offsets, data, items, end }. Reads one INDEX with a uint32 count from the reader's current position.
CFF2_TOP_DICT_OPS const Frozen map of Top DICT operator code to name: 17 CharStrings, 18 FDArray, 0x0C24 FontMatrix, 0x0C07 FontMatrix(legacy alias), 24 vstore.
tableCff2 factory Factory { name, dependencies, factory }.

Usage

import fw from '@awacloud/fw';
import { fw_require, modules } from '@awacloud/fonts';

for (const m of [...fw_require, ...modules]) fw.runtime.register(m);
const { parseSfnt } = fw.runtime.resolve('fontSfnt');
const { parseCff2 } = fw.runtime.resolve('tableCff2');

const sfnt = parseSfnt(bytes);   // bytes: Uint8Array of an OpenType font with a CFF2 table
const cff2 = parseCff2(sfnt.tables.CFF2.bytes);
console.log(cff2.charStringsIndex?.count, cff2.vstoreOffset);

Notes

  • parseCff2Index returns { count: 0, offSize: 0, offsets: [], data: <empty Uint8Array>, items: [], end } for an empty INDEX. Otherwise items[i] is a zero-copy view into the source bytes, and offsets holds count + 1 entries.
  • The Top DICT is decoded through tableCffDict into a Map keyed by the packed operator (0x0C00 | op for two-byte operators).
  • The CharStrings INDEX is read only when the CharStrings operand (17) holds exactly one offset. Charstring programs (including blend and vsindex) are returned as raw bytes and are not interpreted.
  • The Item Variation Store is not decoded: vstoreBytes is the byte range from the vstore offset to the end of the table, and vstore stays null.
  • The Font DICT array is not read: fdArray stays null. Private DICTs and Local Subr INDEXes are not read either.
  • parseCff2 skips ahead to headerSize before reading the Top DICT, so a header longer than 5 bytes is accepted.
  • Errors (all ParseError): fonts/cff2-short (fewer than 5 bytes), fonts/cff2-version (major version is not 2), fonts/cff2-index-offsize (INDEX offSize outside 1..4), fonts/cff2-index-first-offset (first INDEX offset is not 1).

See also

  • cff — the CFF 1 counterpart
  • gvar — variation data for TrueType outlines
  • hvar — variation of horizontal metrics
  • sfnt — host container