awaforge

tableOs2

AGPL-3.0-onlyRelease 2L4

Table OS/2 — OS/2 and Windows Metrics (OT §6.4.7), versions 0–5.

Module tableOs2 | Source packages/front/office/fonts/src/table/os2.js | Deps fontErrors, fontReader, fontWriter | Worker-safe yes

Sizes per version:

Version Size Additional fields
0 78 base
1 86 + ulCodePageRange1/2
2 96 + sxHeight, sCapHeight, usDefaultChar, usBreakChar, usMaxContext
3 96 (same layout as v2)
4 96 (same layout, new fsSelection bits)
5 100 + usLowerOpticalPointSize, usUpperOpticalPointSize

Resolve

const { parseOs2, encodeOs2 } = runtime.resolve('tableOs2');

API

Method Signature Returns
parseOs2 (bytes: Uint8Array) => OS2Table Only the fields present for the detected version are filled in.
encodeOs2 (os2: OS2Table) => Uint8Array Size determined by os2.version.

Base fields common to every version: xAvgCharWidth, usWeightClass, usWidthClass, fsType, ySubscript*, ySuperscript*, yStrikeout*, sFamilyClass, panose[10], ulUnicodeRange1..4, achVendID, fsSelection, usFirstCharIndex, usLastCharIndex, sTypoAscender, sTypoDescender, sTypoLineGap, usWinAscent, usWinDescent.

Examples

const { parseOs2 } = runtime.resolve('tableOs2');
const os2 = parseOs2(sfnt.tables['OS/2'].bytes);
console.log(os2.usWeightClass, os2.fsSelection);

Notes

  • achVendID is read as a 4-character ASCII string (not a uint32).
  • panose is an array of 10 numbers (not a Uint8Array), for easier JSON serialisation.
  • encodeOs2 applies safe defaults: usWeightClass=400, usWidthClass=5, usLastCharIndex=0xFFFF, etc.

See also