awaforge

extraTtHinting

AGPL-3.0-onlyRelease 2L4

RM05 VM — TrueType bytecode hinting (191/220 catalogued opcodes recognized).

Module extraTtHinting | Source packages/front/office/fonts/src/extra/tt-hinting.js | Deps fontErrors, fontReader, ttHintingGs, ttHintingOpCatalog, ttHintingOpPush, ttHintingOpStack, ttHintingOpMath, ttHintingOpControl, ttHintingOpGs, ttHintingOpOutline, ttHintingOpCvt | Worker-safe yes

Evaluates most of the Reference Manual 05 opcode set: push, stack ops, math, control flow (IF/ELSE/EIF, JMPR/JROT/JROF), graphics-state setters (including rounding mode, SROUND/S45ROUND), and outline-manipulation opcodes. Function-definition machinery (FDEF, ENDF, CALL, LOOPCALL) is not implemented — a stream that uses it throws. RM05_OPCODES catalogues every opcode name RM05 defines (measured: 220 entries); RM05_DEFERRED_COUNT is the count of catalogued opcodes the interpreter does not recognize (measured: 29 — see Notes).

Exports

Symbol Type Description
GraphicsState class Graphics state of a VM run.
Zone class Point zone (twilight/glyph).
RM05_OPCODES const Frozen catalogue of the 220 named RM05 opcodes (name, code, arg-bytes, stack delta) — not 340 (opcodes-catalog.js, buildOpcodeTable).
RM05_DEFERRED_COUNT const Count of catalogued opcodes not in the interpreter's IMPLEMENTED set — measured 29, not ~310 (opcodes-catalog.js line 140).
interpret function (bytes, ctx) => { stack, gs, zones, executed, cvt, storage } — executes the stream; throws RenderError('fonts/tt-hinting-unimplemented', …) on a catalogued-but-unrecognized opcode, or RenderError('fonts/tt-hinting-unknown-op', …) on a byte outside the catalogue.
extraTtHinting factory Factory.

Usage

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

for (const m of [...fw_require, ...modules, ...extras]) fw.runtime.register(m);
const { interpret } = fw.runtime.resolve('extraTtHinting');
interpret(font.tables.fpgm.bytes, { /* ctx */ });

Notes

  • 191 of the 220 catalogued opcodes are recognized by interpret (don't throw) — this is the majority of the catalogue, not "~30 implemented" as an earlier draft of this page claimed. The 29 genuinely deferred opcodes include UTP, LOOPCALL, CALL, FDEF, ENDF, MSIRP[0/1], SCFS, MD[0/1], DEBUG, ODD, EVEN, SDB, SDS, NROUND[*], SANGW, AA, FLIPPT, FLIPRGON, FLIPRGOFF, SDPVTL[0/1], GETINFO, IDEF, GETVARIATION (opcodes-catalog.js IMPLEMENTED set).
  • Being "recognized" is not the same as full RM05 fidelity: outline-movement opcodes (MDAP/MIAP/MDRP/MIRP, IUP, SHP/SHC/SHZ/SHPIX/IP, ALIGNRP/ALIGNPTS, ISECT) update reference points and drain the stack correctly but perform no actual glyph-outline coordinate movement — geometry is not computed (opcodes-outline.js header comment). DELTAP1-3/DELTAC1-3 likewise pop their stack pairs without applying any delta (opcodes-cvt.js). By contrast, graphics-state setters — including SROUND/S45ROUND, which set round_state/round_period/round_phase/round_threshold on the GraphicsState — genuinely execute (opcodes-gs.js).
  • Requires the fonts-full or fonts-apple-aat bundle (not in fonts-large).

See also