payv

Pure-Dart OpenType shaping and vector PDF generation.

payv lays out text by executing a font's own GSUB/GPOS tables, the way HarfBuzz does. That is what lets it reach glyphs with no Unicode codepoint — and it is why Kurdish Sorani comes out right.

Zero runtime dependencies, no FFI, no platform channels. Runs on the VM, in Flutter, on a server, in a CLI and on the web.

Install

dart pub add payv

Quick start

import 'dart:io';
import 'package:payv/payv.dart';

void main() async {
  final font = PayvFont.load(await File('Vazirmatn.ttf').readAsBytes());

  final doc = PayvDocument(title: 'پەیڤ', language: 'ckb');
  final page = doc.addPage(format: PageFormat.a4);

  // `x` is where the run STARTS — the right edge for RTL, the left for LTR.
  // A bilingual layout needs no conditional at the call site.
  page.text(
    'پەیڤ',
    x: page.width - 56,
    y: page.height - 120,
    style: TextStyle(font: font.weight(700), size: 48),
  );

  page.textBox(
    'گۆڕینی ڕووکار',
    rect: PdfRect(56, 560, page.width - 112, 80),
    style: TextStyle(font: font, size: 14, lineHeight: 24),
    align: PayvTextAlign.start,
  );

  await File('out.pdf').writeAsBytes(doc.save());
}

The output is real vector text — selectable, searchable, copy-pastable, sharp at any zoom, and about 10 KB a page. payv embeds only the font you hand it, and only the glyphs the document actually draws.

A full worked page is in example/:

dart run example/payv_example.dart path/to/YourFont.ttf

Shaping without the PDF half

final font = OpenTypeFont.parse(bytes);
final run = Shaper(font).shape('پاڵاوتن');

for (var i = 0; i < run.length; i++) {
  print('gid ${run.infos[i].glyphId}  +${run.positions[i].xAdvance}');
}

Why it exists

Dart PDF libraries render Arabic script by swapping each letter for its Unicode presentation form (U+FB50–FDFF / U+FE70–FEFF). Four letters Kurdish Sorani needs have no presentation form at all:

ڕ `U+0695`	ڵ `U+06B5`	ە `U+06D5`	ێ `U+06CE`

Neither does the ڵ+ا ligature. A good Kurdish font supplies those shapes — Vazirmatn keeps them at gid 474, 839, 896 — but they are reachable only as the output of a GSUB lookup, never through cmap. A library that resolves codepoints to glyphs is on the wrong side of that wall, and cannot spell this package's own name.

The argument in full, with measurements and prior art: doc/DESIGN.md.

Supported


Shaping	`GSUB` 1–8, `GPOS` 1–9, `GDEF`, extension lookups
Arabic	joining state machine, `fin2`/`fin3`/`med2`, transparent marks, ZWJ/ZWNJ, tatweel
Bidi	UAX #9, isolates and paired brackets
Fonts	TrueType `glyf`, composites, variable fonts (`fvar`/`gvar`/`avar`/`HVAR`) with static instancing, subsetting
Output	PDF 1.7, CIDFontType2 / Identity-H, `ToUnicode`, `/ActualText`
Scripts	Arabic, Kurdish Sorani, Persian, Urdu, Pashto, Sindhi, Uyghur, Syriac, N'Ko, Thaana, Adlam · Latin/Cyrillic/Greek via the default shaper

Not yet: CFF/CFF2 outlines · Indic, Khmer and Myanmar shapers · tagged PDF (PDF/UA) · encryption, forms, annotations beyond links.

Correctness

Shaping is graded byte-exact against HarfBuzz — 53 corpus cases, 371 glyphs, 16 distinct GSUB-only glyphs — plus Unicode's own BidiTest.txt and BidiCharacterTest.txt. Text extraction is deliberately not the gate: a perfect /ActualText span can sit over completely wrong glyphs.

dart test              # everything
tool/fetch_ucd.sh      # the two bidi conformance suites (15 MB, not vendored)

Known defects and coverage gaps are written down: doc/DEFECTS.md.

Font licensing

payv reads OS/2.fsType and refuses to embed a font whose bits forbid it, rather than embedding it anyway and leaving you the legal problem. Those bits are a foundry's machine-readable summary, not the licence — check the real one for any font you did not author.

Contributing

Issues and PRs welcome, particularly a CFF interpreter, more shapers and PDF/UA structure trees. See CONTRIBUTING.md; the one hard rule is that dart test --tags shaping stays green.