In short

The Japanese constitution of 1889, written in kanji and katakana, printed in top-to-bottom lines as the official gazette printed it, with its articles numbered in kanji.

What you'll build

An eight-page reprint of the Meiji Constitution as the Official Gazette (官報) printed it on 11 February 1889: the imperial edict, the ministers' countersignatures and the first two chapters, thirty-two articles. The text is 漢字カタカナ交じり文 (kanji-katakana majiri-bun), the written language of Meiji law: kanji carry the words, katakana carry the endings, and there are no voicing marks, no small kana and no punctuation at all. The pages are A5, vertical and bound on the right, with a 40 × 15 character grid inside a thick and a thin rule. The articles are numbered by a list counter in kanji, 第一條 to 第三十二條, and the seal and the countersignatures sit where the Gazette put them.

This recipe answers

How do I set a Meiji text in kanji and katakana, with its old forms, and number its articles 第一條?
How do I number chapters 第一章 in kanji numerals, or list items あいう and イロハ?
Which fonts set Japanese, with kanji in their Japanese forms, on screen and in the PDF?

The short answer

script.js · lines 40–53in full code

const layout = { layoutType: 'single', writingMode: 'vertical-rl' }; // bound on the right
const cjk = { grid: { enabled: true, charsPerLine: CHARS, linesPerPage: LINES } };
// Each article is an item of an ordered list: the counter is japanese-informal (十八, not
// 一十八), the prefix 第 and the separator 條 wrap it, and the turnover lines go back to
// the head of the line, as in the Gazette. Chapter two starts its list at 18.
const orderedLists = {
  numberFormat: 'japanese-informal', prefix: '第', separator: '條', gap: em(1),
  indent: em(0), hangingIndent: false, fontFamily: MINCHO, fontWeight: 800,
  color: col('ink'), marginTop: pt(0), marginBottom: pt(0), itemSpacing: pt(0),
};
// The chapters: 第{2:一}章 counts them in the same style, two characters down (字下げ).
const chapter = { level: 2, numberingTemplate: '第{2:一}章', numberSeparator: '　',
  fontSize: pt(BODY), fontWeight: 800, indent: em(2), lineSpan: 2, // 二行取り
  breakBefore: { enabled: false } };

Kanji with katakana, vertical, and articles numbered 第一條 in kanji

Method

#1 · Let a list counter write 第十八條

The code is the short answer above. Each article is an item of a Markdown ordered list, and orderedLists turns its number into the Gazette's form: numberFormat: 'japanese-informal' writes 十八, not 一十八, prefix: '第' and separator: '條' wrap it, and gap: em(1) leaves the full-width space of the original. With hangingIndent: false the turnover lines go back to the head of the line instead of hanging under the text, as in the Gazette. Chapter two starts its list at 18., so the counter runs on across the chapters, and the chapters themselves are numbered 第一章 and 第二章 by the heading template 第{2:一}章, the same counter style (ordered lists).

Page 5: 第一章　天皇 two characters down, articles 第一條 to 第八條 in bold, the second clause of article 8 one character down.

#2 · Leave the katakana as the Gazette wrote them

locale: 'ja' sets the Japanese rules, and none of them rewrites the text. 侵スヘカラス stays without its voicing marks (it reads okasu bekarazu), 行フ keeps its historical kana and 奪ハルヽ its katakana iteration mark. With no small kana and no punctuation in the text, the line breaks fall between any two characters; the kinsoku rules still keep ヽ and 々 off the head of a line. The editor's notes, in modern Japanese with hiragana, sit beside the edict on page 2, so the two ways of writing Japanese can be compared on one page.

#3 · Draw the frame on every page

script.js · lines 57–72in full code

// Header elements are placed on the sheet, not in the flow, so the frame is drawn in
// plain page millimetres: GAP outside the type area, then 1.4 mm to the thin rule.
const GAP = 6;
const rule = (id, out, thickness) => ({ kind: 'box', id, pages: 'all',
  style: { borderColor: col('ink'), borderWidth: pt(thickness) },
  placement: { anchor: { to: 'page', edge: 'top-left' },
    offset: { x: mm(SIDE - out), y: mm(HEAD - out) },
    size: { width: mm(AREA.across + 2 * out), height: mm(AREA.down + 2 * out) } } });
const header = { elements: [
  rule('outer', GAP + 1.4, 1.2), rule('inner', GAP, 0.4),
  // The folio in kanji, under the frame, in the middle of the page.
  { kind: 'text', id: 'folio', content: '{pageNumber}', pages: 'body', fontFamily: GOTHIC,
    fontSize: pt(8), color: col('muted'), align: 'center',
    placement: { anchor: { to: 'page', edge: 'top-left' },
      offset: { x: mm(0), y: mm(HEAD + AREA.down + GAP + 6) }, size: { width: mm(TRIM.w) } } },
] };

The header slot draws in plain page millimetres, not in the vertical flow, so the frame is two boxes placed by the same numbers that place the type area: HEAD from the top, SIDE from each edge. The margins are computed from the grid, not left to it, so the type area sits exactly 6 mm inside the thin rule. The folio, in kanji from pageNumbering.format: 'japanese-informal', sits under the frame.

#4 · Set the title page down the axis

script.js · lines 76–97in full code

// In the flow frame of a vertical page x runs down the column, y leftward across it.
const at = (down, across) => ({ anchor: { to: 'container', edge: 'top-left' },
  offset: { x: mm(down), y: mm(across) } });
const MID = AREA.across / 2; // mm: the axis of the page, from the right of the type area
const cover = {
  id: 'cover', numbered: false, toc: false, span: 'page', runningChapter: false,
  breakBefore: { enabled: true, parity: 'any' },
  advancedDesign: { enabled: true, slot: { elements: [
    { kind: 'text', id: 'title', content: '{titleText}', fontFamily: MINCHO, fontWeight: 800,
      fontSize: pt(34), lineHeight: 1, letterSpacing: pt(10), color: col('ink'),
      placement: at((AREA.down - (7 * 34 + 6 * 10) * PT) / 2, MID - 34 * PT / 2) }, // centred
    { kind: 'text', id: 'date', content: '{attr.date}', fontFamily: MINCHO, fontSize: pt(11),
      lineHeight: 1, letterSpacing: pt(2), color: col('seal'), placement: at(30, MID + 18) },
    { kind: 'text', id: 'source', content: '{attr.source}', fontFamily: MINCHO,
      fontSize: pt(11), lineHeight: 1, letterSpacing: pt(4), color: col('ink'),
      placement: at(30, MID - 18 - 11 * PT) },
    // The edition's language, turned with the line, at the foot of the type area.
    { kind: 'text', id: 'latin', content: '{attr.latin}', fontFamily: GOTHIC, fontSize: pt(7.5),
      lineHeight: 1.5, color: col('muted'), overflow: 'wrap', align: 'right',
      placement: { ...at(0, AREA.across - 9), size: { width: mm(AREA.down), height: mm(9) } } },
  ] } },
};

In a vertical flow x runs down the sheet and y leftward across it, so the title's column is placed by its distance from the right edge of the type area. The date, in the accent, and the Gazette's name stand on either side of the title, 18 mm off the axis.

#5 · Load each face with the text it sets

script.js · lines 300–301in full code

const notes = (markdown.match(/^- .*$/gm) ?? []).join('');
const gothicText = `${notes}凡例上諭一二三四五六七八九十${markdown.match(/latin="([^"]*)"/)[1]}`;

Shippori Mincho B1, a Mincho with the old forms 國, 條 and 權, loads the files for the text and the headings; Noto Sans JP loads only the editor's notes, the folios and the English line. A face given less than it sets fails the capture (C12).

The whole recipe

Sandbox

// ═══ Postext Cookbook · Nº 128 · A Meiji proclamation in kanji and katakana ═════════
// https://postext.dev/en/cookbook/katakana-majiri-proclamation
// Code: MIT · Text: Kanpō 1889, ja.wikisource (CC BY-SA 4.0); notes (CC BY 4.0)
// Fonts: Shippori Mincho B1, Noto Sans JP (SIL OFL 1.1) · Needs postext ≥ 1.16.1
// The Meiji Constitution as the Official Gazette printed it: kanji and katakana, vertical.
import {
  buildDocument, renderPageToCanvas, clearMeasurementCache, loadVerticalAlternates,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'en'; // @lang: the language of the frame; the text is Japanese in both editions
const RECIPE = 'katakana-majiri-proclamation';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: gazette black, one vermilion for the seal, toned paper
const palette = {
  ink: '#211d1a', // the text and the frame
  seal: '#a8321f', // 御名御璽 and the cover's date: the one accent (5.5:1 on the paper)
  muted: '#6b6259', // the editor's notes, the folio, the colophon
  paper: '#fbf8f0',
};
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = [
  ...Object.entries(palette).map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } })),
  { id: 'main-color', name: 'seal (defaults)', value: { hex: palette.seal, model: 'hex' } },
];
// #endregion

const MINCHO = 'Shippori Mincho B1'; // 明朝 with Meiji type in its bones, old forms 國 條 權
const GOTHIC = 'Noto Sans JP'; // the editor's voice: notes, folios, colophon
const [BODY, LEAD] = [10, 18]; // pt: line pitch 1.8 em
const [CHARS, LINES] = [40, 15]; // the type area: 40 characters down, 15 lines across
const PT = 25.4 / 72; // mm in a point
const TRIM = { w: 148, h: 210 }; // mm, A5
const AREA = { down: CHARS * BODY * PT, across: LINES * LEAD * PT }; // 141.1 × 95.3 mm
const HEAD = 37; // mm from the top edge to the head of the type area: 天 deeper than 地
const SIDE = (TRIM.w - AREA.across) / 2; // the same margin on both sides of the frame

// #region answer: kanji with katakana, vertical, and articles numbered 第一條 in kanji
const layout = { layoutType: 'single', writingMode: 'vertical-rl' }; // bound on the right
const cjk = { grid: { enabled: true, charsPerLine: CHARS, linesPerPage: LINES } };
// Each article is an item of an ordered list: the counter is japanese-informal (十八, not
// 一十八), the prefix 第 and the separator 條 wrap it, and the turnover lines go back to
// the head of the line, as in the Gazette. Chapter two starts its list at 18.
const orderedLists = {
  numberFormat: 'japanese-informal', prefix: '第', separator: '條', gap: em(1),
  indent: em(0), hangingIndent: false, fontFamily: MINCHO, fontWeight: 800,
  color: col('ink'), marginTop: pt(0), marginBottom: pt(0), itemSpacing: pt(0),
};
// The chapters: 第{2:一}章 counts them in the same style, two characters down (字下げ).
const chapter = { level: 2, numberingTemplate: '第{2:一}章', numberSeparator: '　',
  fontSize: pt(BODY), fontWeight: 800, indent: em(2), lineSpan: 2, // 二行取り
  breakBefore: { enabled: false } };
// #endregion

// #region frame: a thick and a thin rule round the type area, on every page
// Header elements are placed on the sheet, not in the flow, so the frame is drawn in
// plain page millimetres: GAP outside the type area, then 1.4 mm to the thin rule.
const GAP = 6;
const rule = (id, out, thickness) => ({ kind: 'box', id, pages: 'all',
  style: { borderColor: col('ink'), borderWidth: pt(thickness) },
  placement: { anchor: { to: 'page', edge: 'top-left' },
    offset: { x: mm(SIDE - out), y: mm(HEAD - out) },
    size: { width: mm(AREA.across + 2 * out), height: mm(AREA.down + 2 * out) } } });
const header = { elements: [
  rule('outer', GAP + 1.4, 1.2), rule('inner', GAP, 0.4),
  // The folio in kanji, under the frame, in the middle of the page.
  { kind: 'text', id: 'folio', content: '{pageNumber}', pages: 'body', fontFamily: GOTHIC,
    fontSize: pt(8), color: col('muted'), align: 'center',
    placement: { anchor: { to: 'page', edge: 'top-left' },
      offset: { x: mm(0), y: mm(HEAD + AREA.down + GAP + 6) }, size: { width: mm(TRIM.w) } } },
] };
// #endregion

// #region cover: the title down the middle, the date and the source to its left
// In the flow frame of a vertical page x runs down the column, y leftward across it.
const at = (down, across) => ({ anchor: { to: 'container', edge: 'top-left' },
  offset: { x: mm(down), y: mm(across) } });
const MID = AREA.across / 2; // mm: the axis of the page, from the right of the type area
const cover = {
  id: 'cover', numbered: false, toc: false, span: 'page', runningChapter: false,
  breakBefore: { enabled: true, parity: 'any' },
  advancedDesign: { enabled: true, slot: { elements: [
    { kind: 'text', id: 'title', content: '{titleText}', fontFamily: MINCHO, fontWeight: 800,
      fontSize: pt(34), lineHeight: 1, letterSpacing: pt(10), color: col('ink'),
      placement: at((AREA.down - (7 * 34 + 6 * 10) * PT) / 2, MID - 34 * PT / 2) }, // centred
    { kind: 'text', id: 'date', content: '{attr.date}', fontFamily: MINCHO, fontSize: pt(11),
      lineHeight: 1, letterSpacing: pt(2), color: col('seal'), placement: at(30, MID + 18) },
    { kind: 'text', id: 'source', content: '{attr.source}', fontFamily: MINCHO,
      fontSize: pt(11), lineHeight: 1, letterSpacing: pt(4), color: col('ink'),
      placement: at(30, MID - 18 - 11 * PT) },
    // The edition's language, turned with the line, at the foot of the type area.
    { kind: 'text', id: 'latin', content: '{attr.latin}', fontFamily: GOTHIC, fontSize: pt(7.5),
      lineHeight: 1.5, color: col('muted'), overflow: 'wrap', align: 'right',
      placement: { ...at(0, AREA.across - 9), size: { width: mm(AREA.down), height: mm(9) } } },
  ] } },
};
// #endregion

const config = () => ({ // a factory: the engine caches resolved configs per object
  locale: 'ja', // written out, never LANG (gotcha: ja-locale-tag)
  colorPalette,
  page: {
    sizePreset: 'custom', width: mm(TRIM.w), height: mm(TRIM.h), dpi: 150,
    backgroundColor: col('paper'),
    margins: { top: mm(HEAD), bottom: mm(TRIM.h - HEAD - AREA.down), left: mm(SIDE),
      right: mm(SIDE), mirror: true },
    pageNumbering: { format: 'japanese-informal' }, // 一, 二, 三…
  },
  layout,
  cjk,
  bodyText: {
    fontFamily: MINCHO, fontSize: pt(BODY), lineHeight: pt(LEAD), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
    // A new clause of an article (項) starts one character down; the edict's paragraphs
    // start flush, as the Gazette sets them.
    textAlign: 'justify', firstLineIndent: em(1), indentAfterHeading: true,
  },
  headings: {
    fontFamily: MINCHO, color: col('ink'), fontWeight: 800,
    levels: [
      // Restated: any headings object drops the H1 break (gotcha: headings-drop-h1-break).
      { level: 1, breakBefore: { enabled: true, parity: 'any' } },
      chapter,
    ],
  },
  headingStyles: [
    cover,
    // 凡例 and 上諭: in the editor's gothic, one line, not counted as chapters.
    { id: 'notes', numbered: false, fontFamily: GOTHIC, fontWeight: 700, fontSize: pt(9),
      color: col('muted'), lineSpan: 1, indent: em(1) },
    { id: 'edict', numbered: false, fontFamily: GOTHIC, fontWeight: 700, fontSize: pt(9),
      color: col('muted'), lineSpan: 2, indent: em(1) },
    { id: 'law', numbered: false, indent: em(1), lineSpan: 2 },
  ],
  unorderedLists: { bulletChar: '一', gap: em(1), indent: em(1), fontFamily: GOTHIC,
    color: col('muted'), marginTop: pt(0), marginBottom: pt(0), itemSpacing: pt(0) },
  orderedLists,
  paragraphStyles: [
    { id: 'flush', firstLineIndent: em(0) },
    // 御名　御璽, larger, three characters down: where the Emperor signed and sealed.
    { id: 'seal', fontSize: pt(15), lineHeight: pt(2 * LEAD), color: col('seal'),
      indent: em(2), marginTop: pt(LEAD) },
    // The ministers' countersignatures end at the foot of the line (地付き).
    { id: 'countersign', textAlign: 'end', marginTop: pt(LEAD) },
    { id: 'colophon', fontFamily: GOTHIC, fontSize: pt(7), lineHeight: pt(LEAD),
      color: col('muted'), textAlign: 'left', marginTop: pt(2 * LEAD) },
  ],
  header,
  footer: { elements: [] },
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Markdown sample · 140 lines · content.en.md
title: "大日本帝國憲法"
author: "明治二十二年二月十一日發布"
---

# 大日本帝國憲法 {style="cover" date="明治二十二年二月十一日" source="官報號外" latin="The Constitution of the Empire of Japan · Official Gazette, 11 February 1889"}

## 凡例 {style="notes"}

- 本書には、明治二十二年二月十一日の官報號外に載った大日本帝國憲法のうち、上諭と第一章、第二章を収めた。
- 本文は官報のとおり漢字カタカナ交じり文で組み、旧字体と歴史的仮名遣いを改めていない。原文には濁点も句読点もない。「侵スヘカラス」は「おかすべからず」、「行フ」は「おこなう」と読む。
- 官報は送り仮名のカタカナを漢字より小さく組んでいるが、本書では本文と同じ大きさにそろえた。
- 大臣の副署は、官報では官職名を均等に割り付けているが、本書では行末をそろえるだけにとどめた。

## 上諭 {style="edict"}

:::paragraphs{style="flush"}
朕祖宗ノ遺烈ヲ承ケ萬世一系ノ帝位ヲ踐ミ朕カ親愛スル所ノ臣民ハ即チ朕カ祖宗ノ惠撫慈養シタマヒシ所ノ臣民ナルヲ念ヒ其ノ康福ヲ増進シ其ノ懿徳良能ヲ發達セシメムコトヲ願ヒ又其ノ翼贊ニ依リ與ニ倶ニ國家ノ進運ヲ扶持セムコトヲ望ミ乃チ明治十四年十月十二日ノ詔命ヲ履踐シ茲ニ大憲ヲ制定シ朕カ率由スル所ヲ示シ朕カ後嗣及臣民及臣民ノ子孫タル者ヲシテ永遠ニ循行スル所ヲ知ラシム

國家統治ノ大權ハ朕カ之ヲ祖宗ニ承ケテ之ヲ子孫ニ傳フル所ナリ朕及朕カ子孫ハ將來此ノ憲法ノ條章ニ循ヒ之ヲ行フコトヲ愆ラサルヘシ

朕ハ我カ臣民ノ權利及財産ノ安全ヲ貴重シ及之ヲ保護シ此ノ憲法及法律ノ範圍内ニ於テ其ノ享有ヲ完全ナラシムヘキコトヲ宣言ス

帝國議會ハ明治二十三年ヲ以テ之ヲ召集シ議會開會ノ時ヲ以テ此ノ憲法ヲシテ有効ナラシムルノ期トスヘシ

將來若此ノ憲法ノ或ル條章ヲ改定スルノ必要ナル時宜ヲ見ルニ至ラハ朕及朕カ繼統ノ子孫ハ發議ノ權ヲ執リ之ヲ議會ニ付シ議會ハ此ノ憲法ニ定メタル要件ニ依リ之ヲ議決スルノ外朕カ子孫及臣民ハ敢テ之カ紛更ヲ試ミルコトヲ得サルヘシ

朕カ在廷ノ大臣ハ朕カ爲ニ此ノ憲法ヲ施行スルノ責ニ任スヘク朕カ現在及將來ノ臣民ハ此ノ憲法ニ對シ永遠ニ從順ノ義務ヲ負フヘシ
:::

:::paragraphs{style="seal"}
御名　御璽
:::

:::paragraphs{indent=6}
明治二十二年二月十一日
:::

:::paragraphs{style="countersign"}
内閣總理大臣　伯爵　黒田清隆

樞密院議長　伯爵　伊藤博文

外務大臣　伯爵　大隈重信

海軍大臣　伯爵　西郷從道

農商務大臣　伯爵　井上　馨

司法大臣　伯爵　山田顯義

大藏大臣兼内務大臣　伯爵　松方正義

陸軍大臣　伯爵　大山　巖

文部大臣　子爵　森　有禮

遞信大臣　子爵　榎本武揚
:::

## 大日本帝國憲法 {style="law"}

## 天皇

1. 大日本帝國ハ萬世一系ノ天皇之ヲ統治ス

2. 皇位ハ皇室典範ノ定ムル所ニ依リ皇男子孫之ヲ繼承ス

3. 天皇ハ神聖ニシテ侵スヘカラス

4. 天皇ハ國ノ元首ニシテ統治權ヲ總攬シ此ノ憲法ノ條規ニ依リ之ヲ行フ

5. 天皇ハ帝國議會ノ協贊ヲ以テ立法權ヲ行フ

6. 天皇ハ法律ヲ裁可シ其ノ公布及執行ヲ命ス

7. 天皇ハ帝國議會ヲ召集シ其ノ開會閉會停會及衆議院ノ解散ヲ命ス

8. 天皇ハ公共ノ安全ヲ保持シ又ハ其ノ災厄ヲ避クル爲緊急ノ必要ニ由リ帝國議會閉會ノ場合ニ於テ法律ニ代ルヘキ勅令ヲ發ス

   此ノ勅令ハ次ノ會期ニ於テ帝國議會ニ提出スヘシ若議會ニ於テ承諾セサルトキハ政府ハ將來ニ向テ其ノ効力ヲ失フコトヲ公布スヘシ

9. 天皇ハ法律ヲ執行スル爲ニ又ハ公共ノ安寧秩序ヲ保持シ及臣民ノ幸福ヲ増進スル爲ニ必要ナル命令ヲ發シ又ハ發セシム但シ命令ヲ以テ法律ヲ變更スルコトヲ得ス

10. 天皇ハ行政各部ノ官制及文武官ノ俸給ヲ定メ及文武官ヲ任免ス但シ此ノ憲法又ハ他ノ法律ニ特例ヲ掲ケタルモノハ各々其ノ條項ニ依ル

11. 天皇ハ陸海軍ヲ統帥ス

12. 天皇ハ陸海軍ノ編制及常備兵額ヲ定ム

13. 天皇ハ戰ヲ宣シ和ヲ講シ及諸般ノ條約ヲ締結ス

14. 天皇ハ戒嚴ヲ宣告ス

    戒嚴ノ要件及効力ハ法律ヲ以テ之ヲ定ム

15. 天皇ハ爵位勳章及其ノ他ノ榮典ヲ授與ス

16. 天皇ハ大赦特赦減刑及復權ヲ命ス

17. 攝政ヲ置クハ皇室典範ノ定ムル所ニ依ル

    攝政ハ天皇ノ名ニ於テ大權ヲ行フ

## 臣民權利義務

18. 日本臣民タルノ要件ハ法律ノ定ムル所ニ依ル

19. 日本臣民ハ法律命令ノ定ムル所ノ資格ニ應シ均ク文武官ニ任セラレ及其ノ他ノ公務ニ就クコトヲ得

20. 日本臣民ハ法律ノ定ムル所ニ從ヒ兵役ノ義務ヲ有ス

21. 日本臣民ハ法律ノ定ムル所ニ從ヒ納税ノ義務ヲ有ス

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23. 日本臣民ハ法律ニ依ルニ非スシテ逮捕監禁審問處罰ヲ受クルコトナシ

24. 日本臣民ハ法律ニ定メタル裁判官ノ裁判ヲ受クルノ權ヲ奪ハルヽコトナシ

25. 日本臣民ハ法律ニ定メタル場合ヲ除ク外其ノ許諾ナクシテ住所ニ侵入セラレ及搜索セラルヽコトナシ

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:::paragraphs{style="colophon"}
Set in Shippori Mincho B1 and Noto Sans JP (SIL OFL) · Text: Official Gazette (官報) extra of 11 February 1889, from the Japanese Wikisource transcription (revision 244180, CC BY-SA 4.0) · Editorial notes: CC BY 4.0
:::
`; // content.<lang>.md: the same Japanese text in both

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
const FONTS = { 'Shippori Mincho B1': ['400', '800'], 'Noto Sans JP': ['400', '700'] };
// #region voices: each face loads the files of the characters it sets
const notes = (markdown.match(/^- .*$/gm) ?? []).join('');
const gothicText = `${notes}凡例上諭一二三四五六七八九十${markdown.match(/latin="([^"]*)"/)[1]}`;
// #endregion

// ─── 4 · Build & show ───────────────────────────────────────────────────────
await loadFonts(FONTS, markdown);
await loadCjkFonts({ [MINCHO]: FONTS[MINCHO] }, markdown.replace(/^- .*$/gm, ''),
  { vertical: true });
await loadCjkFonts({ [GOTHIC]: FONTS[GOTHIC] }, gothicText, { vertical: true });
const doc = await buildWithFonts(() => buildDocument({ markdown }, config()), markdown);
showBook(doc, { title: t({ en: 'The Meiji Constitution, 1889',
  es: 'La Constitución Meiji, 1889' }) });
offerPdf(() => renderToPdf(doc, { fontProvider: cjkPdfProvider }), `${RECIPE}.pdf`);

Kit · core, fonts, viewer, pdf, cjk: the same in every recipe · 453 lines
// ─── Kit ── helpers shared by every Cookbook recipe · postext.dev/cookbook ─────

// ─── Kit · core v1 ── the same in every recipe · postext.dev/cookbook ─────────
function mm(value) { return { value, unit: 'mm' }; }
function pt(value) { return { value, unit: 'pt' }; }
function em(value) { return { value, unit: 'em' }; }
/** The sample language's string: t({ en: 'Figure', es: 'Figura' }). */
function t(strings) { return strings[LANG] ?? Object.values(strings)[0]; }
/** A file in this recipe's assets folder, served from the Postext repo by jsDelivr. */
function asset(file) { return `https://cdn.jsdelivr.net/gh/drnachio/postext@main/cookbook/${RECIPE}/assets/${file}`; }

// ─── Kit · fonts v1 ── the same in every recipe · postext.dev/cookbook ────────
// Postext measures text with the faces the browser has loaded, and caches the
// widths, so every face must be ready before the first build. Faces come from
// Fontsource: the same static files the PDF embeds, so screen and PDF agree.

/** faces = { 'Family Name': ['400', '400i', '700'] }. `text` is the sample:
 *  letters beyond Latin-1 (č, ł, ő…) also load the latin-ext files. With
 *  `optional`, a face Fontsource does not ship is skipped instead of failing.
 *  Resolves to the number of faces added. */
async function loadFonts(faces, text = '', { optional = false } = {}) {
  kitStatus('Loading fonts…');
  const ranges = {
    latin: 'U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,'
      + 'U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD',
    'latin-ext': 'U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,'
      + 'U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF',
  };
  const subsets = /[Ā-˿Ḁ-ỿ]/.test(text) ? ['latin', 'latin-ext'] : ['latin'];
  const jobs = [];
  let added = 0;
  for (const [family, specs] of Object.entries(faces)) {
    const id = fontsourceId(family);
    const meta = optional ? await fontsourceMeta(family) : null;
    for (const spec of new Set(specs)) {
      const weight = parseInt(spec, 10);
      const style = spec.endsWith('i') ? 'italic' : 'normal';
      if (hasFace(family, weight, style)) continue;
      if (optional && !(meta?.weights.includes(weight) && meta.styles.includes(style))) continue;
      for (const subset of subsets) {
        const url = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-${subset}-${weight}-${style}.woff2`;
        const face = new FontFace(family, `url(${url}) format('woff2')`,
          { weight: String(weight), style, unicodeRange: ranges[subset] });
        jobs.push(face.load().then((ready) => { document.fonts.add(ready); added++; }, () => {
          if (subset === 'latin' && !optional) throw new Error(`Fontsource has no ${family} ${weight} ${style}`);
        }));
      }
    }
  }
  await Promise.all(jobs).catch((error) => { kitFail(error); throw error; });
  return added;
}

/** Runs `build` (a buildDocument or buildBundle call) and checks the faces
 *  the pages use. A regular face missing from FONTS is loaded with a warning;
 *  bold and italic variants are loaded when the family ships them. Then the
 *  measurement caches are cleared and the build runs again. */
async function buildWithFonts(build, text = '') {
  const tried = new Set();
  for (let round = 0; round < 3; round++) {
    kitStatus('Laying out…');
    await new Promise(requestAnimationFrame);          // let the status paint first
    const result = await Promise.resolve().then(build).catch((error) => { kitFail(error); throw error; });
    const wanted = { base: {}, variants: {} };
    for (const { font, base } of [result].flat().flatMap(fontStringsOf)) {
      const { family, weight, style } = parseFont(font);
      const key = `${family}|${weight}|${style}`;
      if (tried.has(key) || hasFace(family, weight, style)) continue;
      tried.add(key);
      (wanted[base ? 'base' : 'variants'][family] ??= []).push(`${weight}${style === 'italic' ? 'i' : ''}`);
    }
    if (Object.keys(wanted.base).length) {
      console.warn(`[cookbook] FONTS does not list ${JSON.stringify(wanted.base)}: loading them.`);
    }
    const added = await loadFonts(wanted.base, text) + await loadFonts(wanted.variants, text, { optional: true });
    if (added === 0) return result;
    clearMeasurementCache();
  }
  throw new Error('The fonts did not settle after three builds.');
}

/** Every font string of the layout. `base` marks a block's own face; its
 *  bold, italic and bold-italic variants are listed whether or not used. */
function fontStringsOf(doc) {
  const found = new Map();
  const walk = (node) => {
    if (!node || typeof node !== 'object') return;
    if (Array.isArray(node)) { node.forEach(walk); return; }
    for (const [key, value] of Object.entries(node)) {
      if (typeof value === 'string' && /fontString$/i.test(key)) {
        found.set(value, found.get(value) || key === 'fontString');
      } else if (value && typeof value === 'object') walk(value);
    }
  };
  walk(doc.pages);
  walk(doc.blocks);
  return [...found].map(([font, base]) => ({ font, base }));
}

/** '700 37.5px Open Sans' / 'italic 400 13px "Source Serif 4"' → { family, weight, style }.
 *  A string with no weight ('95.8px Young Serif', from a design text) is 400. */
function parseFont(font) {
  const m = /^(?:(italic|oblique)\s+)?(?:small-caps\s+)?(?:(\d+|bold|normal)\s+)?[\d.]+px\s+(.+)$/.exec(font.trim());
  if (!m) throw new Error(`Unexpected font string: ${font}`);
  const weight = m[2] === 'bold' ? 700 : !m[2] || m[2] === 'normal' ? 400 : Number(m[2]);
  return { family: m[3].replace(/^["']|["']$/g, ''), weight, style: m[1] ? 'italic' : 'normal' };
}

/** True when a loaded FontFace covers exactly this family, weight and style
 *  (document.fonts.check() is also true for families nobody declared). */
function hasFace(family, weight, style) {
  for (const face of document.fonts) {
    if (face.status !== 'loaded' || face.style !== style) continue;
    if (face.family.replace(/^["']|["']$/g, '') !== family) continue;
    const [low, high = low] = face.weight.split(' ').map(Number);
    if (weight >= low && weight <= high) return true;
  }
  return false;
}

/** Fontsource's id for a family: 'Source Serif 4' → 'source-serif-4'. */
function fontsourceId(family) { return family.toLowerCase().replace(/\s+/g, '-'); }

/** The weights and styles a family ships ({ weights: [400, 700], styles: ['normal', 'italic'] }), or null. */
function fontsourceMeta(family) {
  fontsourceMeta.cache ??= new Map();
  const id = fontsourceId(family);
  if (!fontsourceMeta.cache.has(id)) {
    fontsourceMeta.cache.set(id, fetch(`https://api.fontsource.org/v1/fonts/${id}`)
      .then((res) => (res.ok ? res.json() : null), () => null));
  }
  return fontsourceMeta.cache.get(id);
}

// ─── Kit · viewer v1 ── the same in every recipe · postext.dev/cookbook ───────
/** Shows the pages as facing spreads on a dark desk: the first page is a
 *  recto on its own, then verso | recto pairs, as in a bound book. Pages
 *  are painted when they scroll near the screen. */
function showPages(docs, { title, width = 460 } = {}) {
  const root = viewer(title);
  const pages = [docs].flat().flatMap((doc) =>
    doc.pages.map((page) => ({ doc, page, n: (doc.pageIndexOffset ?? 0) + page.index })));
  const spreads = [];
  let verso = null;
  for (const p of pages) {
    if (p.n % 2 === 1) { if (verso) spreads.push([verso, null]); verso = p; }
    else { spreads.push([verso, p]); verso = null; }
  }
  if (verso) spreads.push([verso, null]);
  const density = Math.min(window.devicePixelRatio || 1, 2);
  showPages.painter?.disconnect();
  const painter = new IntersectionObserver((entries) => {
    for (const { isIntersecting, target } of entries) {
      if (!isIntersecting) continue;
      painter.unobserve(target);
      const { doc, page } = target.postext;
      renderPageToCanvas(page, doc, target, { scale: (width * density) / page.width });
    }
  }, { rootMargin: '800px' });
  showPages.painter = painter;
  root.replaceChildren(...spreads.map((pair) => {
    const spread = document.createElement('div');
    spread.className = 'pt-spread';
    for (const p of pair) {
      const figure = document.createElement('figure');
      if (p) {
        const label = p.page.pageLabel || String(p.n + 1);
        const canvas = document.createElement('canvas');
        canvas.postext = p;
        canvas.style.aspectRatio = `${p.page.width} / ${p.page.height}`;
        canvas.setAttribute('role', 'img');
        canvas.setAttribute('aria-label', `Page ${label}`);
        const folio = document.createElement('figcaption');
        folio.textContent = label;
        figure.append(canvas, folio);
        painter.observe(canvas);
      } else figure.className = 'pt-blank';
      spread.append(figure);
    }
    return spread;
  }));
  kitStatus(`${pages.length} ${pages.length === 1 ? 'page' : 'pages'}`);
  document.documentElement.dataset.postext = 'ready';
  return pages.length;
}

/** The desk, the bar and the error reporting, created once. */
function viewer(title) {
  if (!document.getElementById('pt-kit')) {
    document.head.insertAdjacentHTML('beforeend', `<style id="pt-kit">
      :root { color-scheme: dark; }
      body { margin: 0; background: #0e1014; color: #b9bcc4; font: 13px/1.45 system-ui, sans-serif; }
      #pt-bar { position: sticky; top: 0; z-index: 1; display: flex; flex-wrap: wrap; align-items: center;
        gap: 6px 16px; padding: 10px 16px; background: rgb(14 16 20 / .92); backdrop-filter: blur(6px);
        border-bottom: 1px solid #23262d; }
      #pt-bar strong { color: #f4f1ea; font-weight: 600; }
      #pt-actions { display: flex; gap: 12px; margin-left: auto; }
      #pt-actions a, #pt-actions button { color: #d8a21a; font: inherit; background: none; border: 0; padding: 0; cursor: pointer; }
      #pages { display: grid; justify-items: center; gap: 48px; padding: 32px 16px 72px; }
      .pt-spread { display: flex; }
      .pt-spread figure { margin: 0; width: min(460px, 44vw); }
      .pt-spread canvas { display: block; width: 100%; background: #fff;
        box-shadow: 0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
      .pt-spread figure:first-child canvas { box-shadow: inset -14px 0 14px -14px rgb(0 0 0 / .18), 0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
      .pt-spread figcaption { margin-top: 10px; text-align: center; font: 600 10px/1 system-ui, sans-serif;
        letter-spacing: .18em; text-transform: uppercase; color: #6c7079; }
      .pt-blank { visibility: hidden; }
      @media (max-width: 760px) {
        .pt-spread { flex-direction: column; gap: 32px; }
        .pt-spread figure { width: min(460px, 92vw); }
        .pt-blank { display: none; }
      }
    </style>`);
    document.body.insertAdjacentHTML('afterbegin',
      '<header id="pt-bar"><strong id="pt-title"></strong><span id="pt-status" role="status"></span><span id="pt-actions"></span></header>');
    document.getElementById('pt-title').textContent = document.title || 'Postext';
    addEventListener('error', (event) => kitFail(event.error ?? event.message));
    addEventListener('unhandledrejection', (event) => kitFail(event.reason));
  }
  if (title) document.getElementById('pt-title').textContent = title;
  return document.getElementById('pages')
    ?? document.body.appendChild(Object.assign(document.createElement('main'), { id: 'pages' }));
}

function kitStatus(text) {
  viewer();
  document.getElementById('pt-status').textContent = text;
}

function kitFail(error) {
  document.documentElement.dataset.postext = 'error';
  kitStatus(`Error: ${error?.message ?? error}`);
}

// ─── Kit · pdf v1 ── the same in every recipe that exports a PDF ──────────────
/** postext-pdf embeds TrueType bytes. Fetch the Fontsource file the screen
 *  used, snapping to a weight the family ships and falling back to upright
 *  when it has no italic: the PDF asks for every face a block could use. */
async function fontsourceProvider(family, weight, style) {
  const id = fontsourceId(family);
  const meta = await fontsourceMeta(family);
  const weights = meta?.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && meta && !meta.styles.includes('italic') ? 'normal' : style;
  const res = await fetch(`https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-${w}-${s}.woff2`);
  if (!res.ok) throw new Error(`Fontsource has no ${family} ${w} ${s} (${res.status})`);
  return decompressWoff2(new Uint8Array(await res.arrayBuffer()));
}

/** A "Build the PDF" button in the bar. Once built: "Open the PDF" (a new
 *  tab, since CodePen's preview frame cannot show PDFs) and a download link. */
function offerPdf(makePdf, filename) {
  viewer();
  const button = Object.assign(document.createElement('button'), { type: 'button', textContent: 'Build the PDF' });
  button.dataset.postextPdf = filename;
  button.addEventListener('click', async () => {
    button.disabled = true;
    button.textContent = 'Building the PDF…';
    try {
      const bytes = await makePdf();
      const url = URL.createObjectURL(new Blob([bytes], { type: 'application/pdf' }));
      const size = `${Math.max(1, Math.round(bytes.length / 1024))} KB`;
      button.replaceWith(
        Object.assign(document.createElement('a'), { href: url, target: '_blank', rel: 'noopener', textContent: 'Open the PDF ↗' }),
        Object.assign(document.createElement('a'), { href: url, download: filename, textContent: `Download ${filename} · ${size}` }));
    } catch (error) {
      button.disabled = false;
      button.textContent = 'Build the PDF';
      kitFail(error);
    }
  });
  document.getElementById('pt-actions').append(button);
}

// ─── Kit · cjk v1 ── Chinese, Japanese and Korean books · postext.dev/cookbook ─
// Fontsource ships a CJK family as about a hundred files per weight, each
// declared in its stylesheet with the unicode-range it covers. The screen
// loads the files the sample touches; the PDF gets the same files for the
// characters its pages set in each face, and embeds each as a subset.
// A book bound on the right (vertical text) is shown with its spreads
// mirrored: page 1 alone on the left of the spine, then [3 | 2].

/** The files of a Fontsource face, read from its stylesheet: { url, range,
 *  ranges }, the last declared first (the order the browser tries them in). */
function cjkSlices(family, weight, style) {
  cjkSlices.cache ??= new Map();
  const id = fontsourceId(family);
  const css = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/${weight}${style === 'italic' ? '-italic' : ''}.css`;
  if (!cjkSlices.cache.has(css)) {
    cjkSlices.cache.set(css, fetch(css)
      .then((res) => {
        if (!res.ok) throw new Error(`Fontsource has no ${family} ${weight} ${style} (${res.status})`);
        return res.text();
      })
      .then((text) => [...text.matchAll(/@font-face\s*{([^}]*)}/g)].map(([, rule]) => {
        const range = /unicode-range:\s*([^;]+);/.exec(rule)?.[1].trim() ?? 'U+0-10FFFF';
        const ranges = range.split(',').map((part) => {
          const [lo, hi = lo] = part.trim().slice(2).split('-');
          return [parseInt(lo, 16), parseInt(hi, 16)];
        });
        return { url: new URL(/url\(([^)]+?\.woff2)\)/.exec(rule)[1], css).href, range, ranges };
      }).reverse()));
  }
  return cjkSlices.cache.get(css);
}

/** The file of `slices` that holds code point `cp`, if any. */
function cjkSliceFor(slices, cp) {
  return slices.find((slice) => slice.ranges.some(([lo, hi]) => cp >= lo && cp <= hi));
}

/** Whether Fontsource serves `family` as a Chinese, Japanese or Korean
 *  family (its subsets name the script). Fails when the API does not
 *  answer: a CJK face taken for a Latin one would paint in a system face. */
async function isCjkFamily(family) {
  const meta = await fontsourceMeta(family);
  if (!meta) throw new Error(`api.fontsource.org did not describe ${family}: reload to try again`);
  return !!meta.subsets?.some((subset) => /^(chinese|japanese|korean)/.test(subset));
}

/** faces = { 'Noto Serif TC': ['400', '700'] }, as for loadFonts: the
 *  whole FONTS object may be passed, its other families are left to
 *  loadFonts. Adds one FontFace per file of each CJK face with its
 *  unicodeRange, then loads the files `text` touches. `text` is what the
 *  faces set: the sample for the text face; a book in several voices calls
 *  it once per voice (loadCjkFonts({ 'LXGW WenKai TC': ['400'] }, quotes)),
 *  so the heading and quotation faces fetch and check only their own
 *  characters. Fails when a character of `text` is in no file of a face.
 *  List every weight the pages use: a weight left to buildWithFonts gets
 *  the latin file only. With { vertical: true } it also loads each
 *  family's vertical forms (brackets, quotes, pause marks) for the canvas,
 *  which needs loadVerticalAlternates imported from postext. Resolves to
 *  the number of files loaded. */
async function loadCjkFonts(faces, text, { vertical = false } = {}) {
  kitStatus('Loading fonts…');
  let loaded = 0;
  try {
    if (vertical && typeof loadVerticalAlternates !== 'function') {
      throw new Error('loadCjkFonts(…, { vertical: true }) needs loadVerticalAlternates imported from postext');
    }
    for (const [family, specs] of Object.entries(faces)) {
      if (!(await isCjkFamily(family))) continue;
      const twin = [];
      for (const spec of new Set(specs)) {
        const weight = parseInt(spec, 10);
        const style = spec.endsWith('i') ? 'italic' : 'normal';
        const slices = await cjkSlices(family, weight, style);
        const missing = [...new Set(text)].filter((ch) => /\S/.test(ch) && !cjkSliceFor(slices, ch.codePointAt(0)));
        if (missing.length) {
          throw new Error(`${family} ${spec} has no file for ${missing.slice(0, 12).join(' ')}: `
            + `give each face the text it sets (loadCjkFonts({ '${family}': ['${spec}'] }, text))`);
        }
        for (const slice of slices) {
          document.fonts.add(new FontFace(family, `url(${slice.url}) format('woff2')`,
            { weight: String(weight), style, unicodeRange: slice.range }));
          twin.push({ source: slice.url, weight: String(weight), style, unicodeRange: slice.range });
        }
        const font = `${style === 'italic' ? 'italic ' : ''}${weight} 16px "${family}"`;
        loaded += (await document.fonts.load(font, text)).length;
        if (!document.fonts.check(font, text)) throw new Error(`${family} ${spec} did not load for the sample`);
      }
      // The same files under a twin name with the `vert` feature on: the
      // canvas paints the punctuation of vertical lines with it.
      if (vertical && twin.length) await loadVerticalAlternates(family, twin);
    }
  } catch (error) {
    kitFail(error);
    throw error;
  }
  return loaded;
}

/** The PDF font provider for recipes with CJK faces: a family whose
 *  Fontsource subsets are Chinese, Japanese or Korean gets the files that
 *  hold the characters its pages set (`request.codePoints`); any other
 *  family gets the latin file fontsourceProvider fetches (the "pdf" block)
 *  and, when the face sets letters only latin-ext has, that file too. */
async function cjkPdfProvider(family, weight, style, request) {
  if (!(await isCjkFamily(family))) return cjkLatinPdfFiles(family, weight, style, request);
  const meta = await fontsourceMeta(family);
  const weights = meta.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && !meta.styles.includes('italic') ? 'normal' : style;
  const slices = await cjkSlices(family, w, s);
  const picked = new Set();
  for (const cp of request?.codePoints ?? []) {
    const slice = cjkSliceFor(slices, cp);
    if (slice) picked.add(slice);
  }
  if (!picked.size) picked.add(slices[0]);
  return Promise.all(slices.filter((slice) => picked.has(slice)).map(async (slice) => {
    const res = await fetch(slice.url);
    if (!res.ok) throw new Error(`Fontsource file ${slice.url} (${res.status})`);
    return decompressWoff2(new Uint8Array(await res.arrayBuffer()));
  }));
}

/** A Latin family set next to the CJK faces: its latin file, then its
 *  latin-ext file when the face sets letters only latin-ext has (ō ū in
 *  Hepburn rōmaji, ǎ in pinyin), the file loadFonts adds on screen for
 *  them. Latin comes first: postext-pdf draws a character from the first
 *  file that has it, as the browser takes a character both files hold from
 *  latin. A face Fontsource ships without latin-ext, or whose file does
 *  not come, gets latin alone, and the PDF names the letters it lacks. */
async function cjkLatinPdfFiles(family, weight, style, request) {
  const meta = await fontsourceMeta(family);
  const beyond = [...(request?.codePoints ?? [])].some(cjkLatinExtOnly);
  if (!beyond || !meta?.subsets?.includes('latin-ext')) return fontsourceProvider(family, weight, style);
  const weights = meta.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && !meta.styles.includes('italic') ? 'normal' : style;
  const id = fontsourceId(family);
  const url = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-ext-${w}-${s}.woff2`;
  const [latin, ext] = await Promise.all([fontsourceProvider(family, weight, style), fetch(url)
    .then(async (res) => (res.ok ? decompressWoff2(new Uint8Array(await res.arrayBuffer())) : null), () => null)]);
  return ext ? [latin, ext] : latin;
}

/** Whether code point `cp` is in Fontsource's latin-ext file and not in
 *  its latin file: Latin Extended-A and -B, IPA, the spacing modifiers and
 *  Latin Extended Additional (loadFonts's test for latin-ext), less the
 *  few latin holds too (ı Œ œ ʻ ʼ ˆ ˚ ˜). */
function cjkLatinExtOnly(cp) {
  if (!((cp >= 0x100 && cp <= 0x2ff) || (cp >= 0x1e00 && cp <= 0x1eff))) return false;
  return ![0x131, 0x152, 0x153, 0x2bb, 0x2bc, 0x2c6, 0x2da, 0x2dc].includes(cp);
}

/** showPages for a book bound on either edge. A right-bound book (the
 *  document says so: doc.binding is 'right' for page.binding 'right' and
 *  for vertical text) lies on the desk as it opens: page 1 alone on the
 *  left of the spine, then [3 | 2], the spine shade on each page's inner
 *  edge. `binding` ('left' | 'right') overrides the document's. */
function showBook(docs, { binding, ...options } = {}) {
  const count = showPages(docs, options);
  const right = (binding ?? [docs].flat()[0]?.binding) === 'right';
  if (!document.getElementById('pt-kit-cjk')) {
    // The pages keep direction ltr: a canvas draws text in the direction its
    // element inherits, and under rtl each run would end where the engine
    // starts it, its brackets mirrored.
    document.head.insertAdjacentHTML('beforeend', `<style id="pt-kit-cjk">
      .pt-spread[dir="rtl"] canvas { direction: ltr; }
      .pt-spread[dir="rtl"] figure:first-child canvas { box-shadow: inset 14px 0 14px -14px rgb(0 0 0 / .18),
        0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
    </style>`);
  }
  // Each pair stays [verso, recto] in the page; right to left, the verso
  // sits on the right. Phones stack the pages in reading order either way.
  for (const spread of document.querySelectorAll('#pages > .pt-spread')) spread.dir = right ? 'rtl' : 'ltr';
  document.getElementById('pages').dataset.binding = right ? 'right' : 'left';
  return count;
}

// ─── /Kit ───────────────────────────────────────────────────────────────────────

The composed script.js runs as it is: paste it into any page’s module script, or open the recipe on CodePen. Recipe folder on GitHub ↗ (opens in a new tab)

Variations

#Hang the turnover lines under the text

Modern law books set the second line of an article under its first character of text, not under 第.

-  indent: em(0), hangingIndent: false, fontFamily: MINCHO, fontWeight: 800,
+  indent: em(0), hangingIndent: true, fontFamily: MINCHO, fontWeight: 800,

#Number the articles in daiji

Some legal and financial texts write 壱, 弐, 参: the token 壱 or the style japanese-formal gives 第壱條, 第弐條.

-  numberFormat: 'japanese-informal', prefix: '第', separator: '條', gap: em(1),
+  numberFormat: 'japanese-formal', prefix: '第', separator: '條', gap: em(1),

Pitfalls

Pitfall

Tag a Japanese text 'ja', never zh-Hans or LANG

A recipe's editions are en and es, but a Japanese sample is Japanese in both: `locale: LANG` would tag it English or Spanish, and a Chinese tag would set it by the Chinese rules (Kaiming punctuation, small kana free to start a line, 图 for 図, Chinese glyph forms in the PDF). Write 'ja': it picks the Japan region (JLReq line breaking and punctuation, sesame emphasis marks, furigana spacing, 図 and 表 labels) and turns hyphenation off. The lint fails a text with kana under a zh or ko tag. Japanese line breaking (kinsoku) →

Pitfall

Set Japanese in a Japanese face

Noto Serif SC and TC have kana, but they draw the kanji in Chinese forms (直, 骨 and 角 differ) and the kana in a Chinese design. Set the text in Noto Serif JP or Shippori Mincho B1 and the heads in Noto Sans JP, loaded with loadCjkFonts. Fontsource's Japanese files hold no hentaigana or other historic kana (U+1B000–1B16F): loadCjkFonts fails on them and the PDF prints boxes, so write the modern kana or ship a face that has them in the recipe's assets. Shippori Mincho also lacks the macron vowels ō and ū: set rōmaji in a Latin face. Kana, kanji and rōmaji →

Pitfall

Chinese faces load by slices, through the cjk block

Fontsource serves a Chinese, Japanese or Korean family as about a hundred files per weight, each covering a range of characters. loadFonts fetches only the latin file, so on screen the Han characters come from a system face and measure wrong, and fontsourceProvider hands the PDF that latin file, which prints them as empty boxes. List the cjk kit block, call loadCjkFonts(FONTS, markdown) after loadFonts (once per voice, with the text it sets, when the book uses several CJK faces) and give renderToPdf fontProvider: cjkPdfProvider: both take the files that hold the text's characters. Chinese, Japanese and Korean fonts →

Pitfall

Any headings object switches off the H1 page break

By default an H1 breaks to a recto (always-odd), but passing any headings object resets that default, so chapters run on and span: 'page' does nothing. Restate headings.levels[0].breakBefore: { enabled: true, parity } in every config. Chapters that open on a recto →

Pitfall

A config is cached by identity: build a fresh object

The engine caches resolved configs by object identity, so changing a config in place and building again reuses the old result. Build a fresh object for every build, which is why a recipe's config is a factory: config(). Pages on a canvas →

Pitfall

Load every face before layout

Layout measures text with the faces the browser has loaded and caches the widths, so a face that arrives after the first build leaves wrong line breaks and a PDF that no longer matches the screen. Load every weight and style first, and call clearMeasurementCache() before rebuilding when one arrives late. Fonts before layout →

The Gazette sets the katakana of the endings smaller than the kanji, and spaces the ministers' titles evenly to one width (字取り). Postext sets every character at the body size, and its even spacing, jidori, applies to headings only, so the countersignatures here are only aligned at the foot of the line.
Japanese and Chinese differ on this counter: in a ja document the token 一 and {2:一} mean japanese-informal (百一, 十八), in a Chinese one they mean the Chinese style (一百零一, 十八). The Chinese reader Dates and acronyms upright in vertical text types its 第一條 by hand.

Credits

Recipe: Ignacio Ferro
Text: The Constitution of the Empire of Japan, 11 February 1889: the imperial preamble (上諭) with its countersignatures, chapters 1 and 2, as printed in the Kanpō (Official Gazette) extra of that day · Government of Japan; transcription by Japanese Wikisource editors · CC BY-SA 4.0
The editor's notes (凡例), written in Japanese for this recipe · Postext Cookbook · CC BY 4.0
Fonts: Shippori Mincho B1 (SIL OFL 1.1) · Noto Sans JP (SIL OFL 1.1)
Code: MIT, like Postext

Edit this write-up ↗ (opens in a new tab)Recipe folder on GitHub ↗ (opens in a new tab)

In short

#What you'll build

#The short answer

#Ingredients

#Method

#1 · Let a list counter write 第十八條

#2 · Leave the katakana as the Gazette wrote them

#3 · Draw the frame on every page

#4 · Set the title page down the axis

#5 · Load each face with the text it sets

#The whole recipe

#Variations

#Hang the turnover lines under the text

#Number the articles in daiji

#Pitfalls

#Credits

More from the Cookbook

Dates and acronyms upright in vertical text

A Chinese official document to GB/T 9704

A vertical Chinese novel, bound on the right

What you'll build

The short answer

Ingredients

Method

The whole recipe

Variations

Pitfalls

Credits