Hyphen

pub package License: MIT + MPL 2.0

Hyphen is a cross-platform Flutter package that provides high-quality word hyphenation, implemented in pure Dart. The same code runs on every platform Flutter supports — there is no native library to build and nothing to link.

The engine is a Dart port of hunspell/hyphen, the TeX-pattern hyphenation library originally cut from libHnj for OpenOffice.org. It reads the same hyph_*.dic dictionaries and was verified against the original C implementation over 9.26 million cases across 18 dictionaries, so output is identical rather than merely similar.

With Hyphen, you can split words into their hyphenation parts according to language-specific rules. The API returns a List<String> where each element is a chunk of the word between possible hyphenation points.

❗️ Breaking change in v0.4.0

  • The dart:ffi bindings, the Emscripten JS/WASM runtime, the native build trees, and the Hyphen.fromDictionaryPathWithBindingsAndAllocator constructor are all gone. See the Changelog for details.

✨ Features

  • Works on all Flutter platforms: Android, iOS, macOS, Windows, Linux, Web — one pure-Dart implementation, no platform-specific builds
  • Uses battle-tested hyphen dictionaries
  • Combines hunspell/hyphen's two hyphenation APIs hnj_hyphen_hyphenate2 and hnj_hyphen_hyphenate3 into a single hyphenate function
  • Unified API for all platforms – always use the same Hyphen class, no matter the platform

📦 Installing

Add to your pubspec.yaml:

dependencies:
  hyphen: ^0.4.0

Then run:

flutter pub get

📚 Dictionaries

Hyphen requires a .dic file for the language you want to hyphenate.
These are not bundled due to licensing reasons.

👉 You need to generate or obtain these .dic files yourself.

Where to get dictionary files

Hyphenation dictionaries are created from TeX hyphenation pattern files (commonly available on CTAN and other TeX distribution sources).

🔨 Step-by-step Example: English (US)

  1. Download the pattern file hyph-en-us.tex

  2. Run the substrings.pl script (from hunspell/hyphen):

    perl substrings.pl hyph-en-us.tex hyph_en_US.dic UTF-8

    This generates a file called hyph_en_US.dic.

  3. Add the file to your Flutter project:

    assets/hyph_en_US.dic

  4. Declare it in pubspec.yaml:

    flutter:
  assets:
    - assets/hyph_en_US.dic

🚀 Usage

import 'package:hyphen/hyphen.dart';

Future<void> main() async {
  // Load a dictionary from assets
  final hyphen = await Hyphen.fromDictionaryPath('assets/hyph_en_US.dic');

  // Hyphenate a word
  final result = hyphen.hyphenate('hyphenation');
  print(result); // ["hy", "phen", "ation"]

  // Using the additional parameters to define a minimum distance from the start/end of the word
  // to the first break
  final result2 = hyphen.hyphenate(
    'hyphenation',
    lhmin: 3,
    rhmin: 3,
  );
  print(result2); // ["hyphen", "ation"]
}

Loading a dictionary

From a Flutter asset:

final hyphen = await Hyphen.fromDictionaryPath('assets/hyph_en_US.dic');

From bytes, with no asset bundle — usable in plain Dart, tests and CLI tools:

import 'dart:io';

final hyphen = Hyphen.fromDictionaryBytes(File('hyph_en_US.dic').readAsBytesSync());

🖥 Platform Notes

Hyphen is a pure-Dart package. It runs identically on Android, iOS, macOS, Windows, Linux and Web — there is no native library to build, no platform-specific plugin implementation, and nothing to link. On every platform, you must still provide your own .dic file; see Dictionaries above.

⚠️ License

This package is dual-licensed:

  • Package code (the public API, dictionary loading and hyphenation engine): licensed under MIT.
  • A small number of files are a Dart port of Hunspell/Hyphen C sources and remain covered by that project's license. See THIRD_PARTY_LICENSES.md for exactly which files and terms.

Hyphenation dictionaries come with their own licenses – check the hunspell/hyphen repo before redistributing.

🤝 Contributing

Issues and pull requests are welcome!

Libraries

hyphen