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CFF2 table ​

Contains variable PostScript glyph outlines with blend operators for CFF2-based variable fonts.

Scope ​

  • Format family: OTF-specific
  • Table tag in JSON: CFF2

Specs ​

JSON Skeleton ​

This skeleton reflects fields currently parsed/written by Font Flux JS for this table.

json
{
	"tables": {
		"CFF2": {
			"majorVersion": null,
			"minorVersion": null,
			"topDict": null,
			"globalSubrs": null,
			"charStrings": null,
			"fontDicts": null,
			"fdSelect": null,
			"variationStore": null,
			"_checksum": 0
		}
	}
}

Top-level Fields ​

  • majorVersion - implementation-defined
  • minorVersion - implementation-defined
  • topDict - implementation-defined
  • globalSubrs - implementation-defined
  • charStrings - implementation-defined
  • fontDicts - implementation-defined
  • fdSelect - implementation-defined
  • variationStore - implementation-defined

Nested JSON Structure ​

Parsed CFF2 table:

json
{
	"majorVersion": 2,
	"minorVersion": 0,
	"topDict": { "FontMatrix": [0.001, 0, 0, 0.001, 0, 0] },
	"globalSubrs": [[0, 1]],
	"charStrings": [[139, 14]],
	"fontDicts": [
		{
			"fontDict": { "FontName": 391 },
			"privateDict": { "BlueScale": 0.039625 },
			"localSubrs": [[11]]
		}
	],
	"fdSelect": {
		"format": 3,
		"ranges": [{ "first": 0, "fd": 0 }],
		"sentinel": 500
	},
	"variationStore": [0, 20, 0, 1]
}

Notes:

  • CFF2 has no Name INDEX, no String INDEX, and no Encoding table.
  • variationStore is currently stored as raw bytes.
  • Private DICT and local subroutines are represented per entry in fontDicts[].

Interpreting charStrings ​

Like CFF v1, CFF2 stores glyph outlines as Type 2 charstring byte arrays. Font Flux interprets these into cubic Bézier contour commands:

js
import { FontFlux } from 'font-flux-js';

const contours = FontFlux.interpretCharString(
	cff2.charStrings[glyphIndex],
	fontDict.localSubrs,
	cff2.globalSubrs,
);
// Returns: [[{ type: 'M', x, y }, { type: 'C', x1, y1, x2, y2, x, y }, ...], ...]

Use FontFlux.disassembleCharString(bytes) for a human-readable text representation of the charstring program.

When using FontFlux.open(), CFF2 glyphs automatically include contours, charString, and charStringDisassembly.

Converting to/from SVG paths ​

CFF2 contours work identically with the SVG path conversion methods:

js
const d = FontFlux.contoursToSVG(glyph.contours); // CFF2 cubic → SVG
const contours = FontFlux.svgToContours(d, 'cff'); // SVG → CFF cubic

See the main docs for full SVG path conversion details.

Validation Constraints ​

  • CFF2 outlines are an alternative to TrueType glyf/loca.
  • majorVersion should be 2 for standard CFF2 data.
  • Keep charStrings glyph count aligned with fdSelect ranges when fdSelect is present.
  • variationStore is currently treated as raw bytes; preserve byte integrity if editing manually.

Authoring Example ​

json
{
	"tables": {
		"CFF2": {
			"majorVersion": 2,
			"minorVersion": 0,
			"topDict": {},
			"globalSubrs": [],
			"charStrings": [[14]],
			"fontDicts": [],
			"fdSelect": null,
			"variationStore": null,
			"_checksum": 0
		}
	}
}

Additional Nested Keys Seen In Implementation ​

  • fontDict
  • charStrings
  • fdArray
  • fdSelect
  • variationStore
  • operator
  • operands
  • totalSize

Notes ​

  • Preserve _checksum for stable round-tripping.
  • If a table is only partially understood, prefer keeping unknown bytes in _raw instead of dropping data.
  • Validate with .validate() after edits.