tableGlyf · @awacloud/fonts

Table glyf — Glyph Data (OT §6.4.12, TT §1.2), simple & composite glyphs.

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

Every glyph starts with a header (numberOfContours, bbox). ≥ 0 ⇒ simple; < 0 ⇒ composite. Simple flags encode coordinate compaction (X_SHORT, Y_SAME, REPEAT, …); composites chain references with offset/anchor and a 2×2 F2Dot14 transform.

Resolve

const { parseGlyph, parseGlyf, GLYF_FLAG, COMPONENT_FLAG } = runtime.resolve('tableGlyf');

API

Method	Signature	Returns
`parseGlyph`	`(bytes: Uint8Array) => SimpleGlyph \| CompositeGlyph \| null`	`null` for an empty glyph (length 0).
`parseGlyf`	`(bytes: Uint8Array, locaOffsets: Uint32Array) => Array<glyph\|null>`	One entry per glyph.
`GLYF_FLAG`	frozen object	Simple-point flag bits.
`COMPONENT_FLAG`	frozen object	Composite-component flag bits.

`SimpleGlyph`

{
    kind: 'simple',
    bbox: { xMin, yMin, xMax, yMax },
    numberOfContours,
    endPtsOfContours: number[],
    instructions: Uint8Array,
    points: [{ x, y, onCurve }]
}

`CompositeGlyph`

{
    kind: 'composite',
    bbox,
    components: [{
        flags, glyphIndex, arg1, arg2,
        xy: boolean,                       // ARGS_ARE_XY_VALUES
        transform: { a, b, c, d },         // F2Dot14
        useMyMetrics: boolean
    }],
    instructions: Uint8Array
}

`GLYF_FLAG`

ON_CURVE 0x01, X_SHORT 0x02, Y_SHORT 0x04, REPEAT 0x08, X_SAME_OR_POS 0x10, Y_SAME_OR_POS 0x20, OVERLAP_SIMPLE 0x40.

`COMPONENT_FLAG`

ARG_1_AND_2_ARE_WORDS 0x0001, ARGS_ARE_XY_VALUES 0x0002, ROUND_XY_TO_GRID 0x0004, WE_HAVE_A_SCALE 0x0008, MORE_COMPONENTS 0x0020, WE_HAVE_AN_X_AND_Y_SCALE 0x0040, WE_HAVE_A_TWO_BY_TWO 0x0080, WE_HAVE_INSTRUCTIONS 0x0100, USE_MY_METRICS 0x0200, OVERLAP_COMPOUND 0x0400, SCALED_COMPONENT_OFFSET 0x0800, UNSCALED_COMPONENT_OFFSET 0x1000.

Examples

Parse all glyphs

const { parseGlyf } = runtime.resolve('tableGlyf');
const glyphs = parseGlyf(sfnt.tables.glyf.bytes, loca);
const g = glyphs[42];
if (g && g.kind === 'simple') console.log(g.points.length);

Parser hardening

fonts/glyf-too-many-components — Composite glyphs used to be decoded via do { ... } while (flags & MORE_COMPONENTS) with no upper bound. A malicious font could emit millions of components → OOM. The number of components per glyph is now capped at 256 (OT validators recommend ≤ 8 — the limit leaves a comfortable margin). The resolution-depth cap (MAX_DEPTH = 16 in compositeResolve.js) is unchanged: both width and depth are now bounded.
fonts/inconsistent-tables — Cross-table check: every component.glyphIndex must stay within [0, maxp.numGlyphs). Thrown from buildFont (fonts.js).

Notes

Coordinates are absolute (cumulative delta reconstructed at parse time) — points[i].x are final design units.
A truncated glyph header (< 10 bytes and non-empty) throws ParseError('fonts/glyf-short').
Encoding is implemented on the writer side (the embed-pdf subsetter).

Resolve

API

SimpleGlyph

CompositeGlyph

GLYF_FLAG

COMPONENT_FLAG