kinsoku

Japanese text processing library for kinsoku (禁則処理 - line breaking rules), character classification, yakumono adjustment, and kerning.

pub package License: MIT

Features

  • Kinsoku Shori (禁則処理): Japanese line breaking rules

    • Line-start prohibition (行頭禁則, gyoto kinsoku)
    • Line-end prohibition (行末禁則, gyomatsu kinsoku)
    • Hanging characters (ぶら下げ, burasage)
    • Pushing-in characters (追い込み, oikomi)
    • Separation prohibition for paired characters (……, ‥‥, ――, etc.)

  • Character Classification: Identify character types

    • Kanji (漢字)
    • Hiragana (ひらがな)
    • Katakana (カタカナ)
    • Latin alphabet
    • Numbers
    • Punctuation
    • Yakumono (約物 - Japanese typography symbols)
    • Space

  • Yakumono Adjustment: Fine-tune punctuation and symbol positioning

    • Half-width yakumono handling
    • Gyoto indent for opening brackets
    • Consecutive yakumono spacing

  • Kerning: Spacing adjustments between character pairs

    • Kerning pairs for Japanese punctuation
    • Oikomi (push-in) adjustment calculations

  • Text Alignment: Line-level alignment options

    • TextAlignment.start (天付き): Align to top/left
    • TextAlignment.center: Center alignment
    • TextAlignment.end (地付き): Align to bottom/right

This package is part of the Japanese text layout suite:

Package Description
kinsoku Core text processing (this package)
tategaki Vertical text layout (縦書き)
yokogaki Horizontal text layout (横書き)

Quick Start

シンプルな禁則処理の例:

import 'package:kinsoku/kinsoku.dart';

void main() {
  final text = 'これは禁則処理のテストです。';

  // 指定位置で改行できるか判定
  if (KinsokuProcessor.canBreakAt(text, 10)) {
    print('位置10で改行可能');
  }

  // 最適な改行位置を取得
  final breakPos = KinsokuProcessor.findBreakPosition(text, 10);
  print('推奨改行位置: $breakPos');
}

Platform Support

Platform Pure Dart ICU-based
Flutter (All) ✅ -
Web ✅ -
Windows ✅ ✅
macOS ✅ ✅
Linux ✅ ✅
Server ✅ ✅

Requirements:

  • Dart SDK: ≥3.10.3
  • ICU機能: ICUライブラリが必要（デスクトップ/サーバーのみ）

Installation

Add this to your package's pubspec.yaml file:

dependencies:
  kinsoku: ^0.3.4

Then run:

dart pub get

Usage

Basic Character Classification

import 'package:kinsoku/kinsoku.dart';

void main() {
  // Classify characters
  print(CharacterClassifier.classify('あ')); // CharacterType.hiragana
  print(CharacterClassifier.classify('漢')); // CharacterType.kanji
  print(CharacterClassifier.classify('A'));  // CharacterType.latin

  // Check character properties
  print(CharacterClassifier.isSmallKana('ゃ'));  // true
  print(CharacterClassifier.isLongVowelMark('ー')); // true
}

Kinsoku Processing

import 'package:kinsoku/kinsoku.dart';

void main() {
  final text = 'これは禁則処理のテストです。';

  // Check if we can break at a specific position
  final canBreak = KinsokuProcessor.canBreakAt(text, 10);
  print('Can break at position 10: $canBreak');

  // Find the best break position
  final breakPos = KinsokuProcessor.findBreakPosition(text, 10);
  print('Best break position near 10: $breakPos');

  // Check if a character can hang at line end
  print(KinsokuProcessor.canHangAtLineEnd('。'));  // true
  print(KinsokuProcessor.canHangAtLineEnd('ー'));  // false
}

Yakumono Adjustment

import 'package:kinsoku/kinsoku.dart';

void main() {
  // Adjust yakumono position
  final basePos = Position(100, 200);
  final adjusted = YakumonoAdjuster.adjustPosition(
    '。',
    basePos,
    fontSize: 16.0,
    adjustYakumono: true,
  );
  print('Adjusted position: (${adjusted.x}, ${adjusted.y})');

  // Check yakumono properties
  print(YakumonoAdjuster.isHalfWidthYakumono('。'));  // true
  print(YakumonoAdjuster.getYakumonoWidth('。'));     // 0.5
  print(YakumonoAdjuster.getGyotoIndent('「'));       // 0.1
}

Text Alignment

import 'package:kinsoku/kinsoku.dart';

void main() {
  // Use TextAlignment for line-level alignment
  final alignment = TextAlignment.end; // 地付き (bottom/right alignment)

  switch (alignment) {
    case TextAlignment.start:
      print('天付き - Align to start');
      break;
    case TextAlignment.center:
      print('Center alignment');
      break;
    case TextAlignment.end:
      print('地付き - Align to end');
      break;
  }
}

Kerning

import 'package:kinsoku/kinsoku.dart';

void main() {
  // Get kerning between two characters
  final kerning = KerningProcessor.getKerning('。', '、');
  print('Kerning between 。 and 、: $kerning');  // -0.5

  // Calculate oikomi adjustment
  final adjustment = KerningProcessor.calculateOikomiAdjustment(
    'テキスト',
    0,
    4,
    100.0,  // target width
    110.0,  // current width
  );
  print('Oikomi adjustment: $adjustment');
}

ICU-based Kinsoku Processing (Optional)

For full Unicode UAX #14 compliance with customizable rules, use the ICU-based processor:

Installation Requirements

Install the ICU library on your system:

  • macOS: brew install icu4c
  • Linux: sudo apt install libicu-dev
  • Windows: Download ICU binaries from unicode-org/icu

Usage

import 'package:kinsoku/icu.dart';

void main() {
  // Default UAX #14 rules
  final processor = ICUKinsokuProcessor();

  // Or use JIS X 4051-inspired rules
  final jisProcessor = ICUKinsokuProcessor.withJISX4051Rules();

  // Check if we can break at a position
  final text = 'これは禁則処理のテストです。';
  final canBreak = processor.canBreakAt(text, 10);

  // Find all break positions
  final breaks = processor.getAllBreakPositions(text);
  print('Break positions: $breaks');

  // Clean up
  processor.dispose();
}

Custom Rules

Define custom break iterator rules using ICU syntax:

final customRules = r'''
# Define character classes
$CL_OP = [\u0028 \u300C];  # Opening brackets: （「
$CL_CL = [\u0029 \u300D];  # Closing brackets: ）」
$CL_PC = [\u3002 \u3001];  # Periods and commas: 。、

# Break rules
× $CL_OP;   # No break after opening brackets
$CL_CL ×;   # No break before closing brackets
$CL_PC ×;   # No break before periods/commas
÷;          # Default: allow break
''';

final processor = ICUKinsokuProcessor.withCustomRules(customRules);

Configuration-based Rules

Use the KinsokuConfig class for easier customization:

final config = KinsokuConfig(
  gyotoKinsoku: {'。', '、', '）', '」'},      // Line-start forbidden
  gyomatsuKinsoku: {'（', '「'},              // Line-end forbidden
  burasageAllowed: {'。', '、'},              // Can hang
  pairedCharacters: {'…', '‥'},              // Must stay together
);

final rules = config.toICURules();
final processor = ICUKinsokuProcessor.withCustomRules(rules);

ICU vs Pure Dart Comparison

Feature Pure Dart ICU-based
Dependencies None ICU library required
Unicode Support Basic (hardcoded rules) Full UAX #14
Customization Limited (static sets) Extensive (custom rules)
Performance Fast Fast (native)
Platform All platforms Desktop/Server
JIS X 4051 Compliance Simplified Complete (16+ classes)

JIS X 4051:2004 Complete Compliance

The ICU processor provides full compliance with JIS X 4051:2004:

Complete Character Class Implementation

Class Description Count Examples
Class 1 Opening brackets (始め括弧類) 14 （「『【〈《〔
Class 2 Closing brackets (終わり括弧類) 14 ）」』】〉》〕
Class 3 Japanese delimiters (句読点類) 4 。、，．
Class 4 Western period/comma 2 ,.
Class 5 Middle dots (中点類) 5 ・：；: ;
Class 6 Inseparable chars (分離禁止) 4 ！？!?
Class 7 Prolonged sound (長音記号) 1 ー
Class 8 Small kana (小書き仮名) 24 ぁぃぅぇぉゃゅょゎっァィゥェォャュョヮッ
Class 9 Iteration marks (繰返記号) 7 ゝゞヽヾ々〃〻
Class 10 Currency/units (通貨・単位) 11 $¥£€℃°%
Class 11 Postfix abbreviations 5 ℃°′″℉
Class 12 Prefix abbreviations 3 №＃#
Class 13 Dashes (ダッシュ) 10 ‐–—―－─
Class 14 Ellipsis (リーダー) 3 …‥⋯
Class 15 Combining marks 2 ゛゜
Class 16+ Other special chars Various 〳〴〵ヿ

Line Breaking Rules

  • Gyoto Kinsoku (行頭禁則): 70+ characters cannot appear at line start
  • Gyomatsu Kinsoku (行末禁則): 25+ characters cannot appear at line end
  • Paired Separation (分離禁止): ……, ‥‥, ――, etc. must stay together
  • Consecutive Punctuation: ！！, ？？, ！？, ？！ cannot be separated
  • Special Handling: Currency symbols (¥£€), small kana, iteration marks

See example/icu_example.dart for comprehensive examples.

Use Cases / ユースケース

テキストエディタの改行処理

ユーザー入力テキストの自動改行:

String wrapText(String text, int maxCharsPerLine) {
  final lines = <String>[];
  var remaining = text;

  while (remaining.isNotEmpty) {
    if (remaining.length <= maxCharsPerLine) {
      lines.add(remaining);
      break;
    }

    // 禁則を考慮した改行位置を取得
    final breakPos = KinsokuProcessor.findBreakPosition(
      remaining,
      maxCharsPerLine,
    );

    lines.add(remaining.substring(0, breakPos));
    remaining = remaining.substring(breakPos);
  }

  return lines.join('\n');
}

文字種判定

入力バリデーションやIME処理:

bool isJapaneseText(String text) {
  for (final char in text.characters) {
    final type = CharacterClassifier.classify(char);
    if (type == CharacterType.hiragana ||
        type == CharacterType.katakana ||
        type == CharacterType.kanji) {
      return true;
    }
  }
  return false;
}

DTPソフトウェア

プロフェッショナルな組版処理:

// JIS X 4051準拠の禁則処理（ICU使用）
final processor = ICUKinsokuProcessor.withJISX4051Rules();

// テキストの全改行位置を取得
final breaks = processor.getAllBreakPositions(text);

// カスタムルールで初期化
final config = KinsokuConfig(
  gyotoKinsoku: {'。', '、', '）', '」'},
  gyomatsuKinsoku: {'（', '「'},
  burasageAllowed: {'。', '、'},
);
final customProcessor = ICUKinsokuProcessor.withCustomRules(
  config.toICURules(),
);

カーニング調整

約物間のスペース最適化:

double calculateLineWidth(String line, double fontSize) {
  double width = 0;
  for (var i = 0; i < line.length; i++) {
    width += fontSize;
    if (i < line.length - 1) {
      // 約物間のカーニング値を取得
      final kerning = KerningProcessor.getKerning(
        line[i],
        line[i + 1],
      );
      width += kerning * fontSize;
    }
  }
  return width;
}

Pure Dart Package

This is a pure Dart package with no Flutter dependencies. The core functionality works everywhere:

  • Flutter applications
  • Web applications
  • Server-side Dart applications
  • Command-line tools
  • Any Dart environment

The ICU-based processor requires native ICU library and works on:

  • macOS, Linux, Windows (desktop)
  • Server environments
  • (Not available on web or mobile platforms)

License

MIT License - see LICENSE file for details

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

References

Libraries

icu
ICU-based Japanese text processing with customizable line breaking rules
kinsoku
Japanese text processing library for kinsoku (line breaking rules), character classification, yakumono adjustment, and kerning.