Daten und Akronyme aufrecht im vertikalen Text

// ═══ Postext Cookbook · Nº 081 · Dates and acronyms upright in vertical text ═══════
// https://postext.dev/en/cookbook/chinese-dates-upright
// Code: MIT · Text: 1912 documents, zh.wikisource (CC BY-SA 4.0); notes (CC BY 4.0)
// Fonts: Noto Serif TC, Noto Sans TC, LXGW WenKai TC (SIL OFL 1.1) · Needs postext ≥ 1.25.0
// Two founding documents of the Republic of China, 1912, set vertically as a reader.
import {
  buildDocument, withLoadedFonts, renderPageToCanvas, loadVerticalAlternates,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'en'; // @lang: the language of the sample document ('en' | 'es')
const RECIPE = 'chinese-dates-upright';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: ink, the vermilion of a seal, and the paper of a gazette
const palette = {
  ink: '#1e1a17', // text: a warm near-black
  seal: '#b1291f', // the one accent: the bands, the seal notes, the chapter heads
  tint: '#f6dccf', // the cover's double rule, a pale vermilion
  muted: '#6d645b', // fore-edge heads, the colophon
  paper: '#fffdf8',
};
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 SONG = 'Noto Serif TC'; // 宋/明: the documents
const HEI = 'Noto Sans TC'; // 黑: titles, heads, labels
const KAI = 'LXGW WenKai TC'; // 楷: the editor's headnotes and notes
const BODY = 12; // pt, 小四
const LEAD = 21; // pt: a line gap of 0.75 em
const CHARS = 44; // characters to a line
const LINE = (CHARS * BODY * 25.4) / 72; // mm: the length of a line, 186.3
const TRIM = { w: 184, h: 260 }; // mm, 16开
const MARGIN = { top: 30, bottom: 22, side: 20 }; // mm, minimums: 天头 deeper than 地脚

// #region answer: vertical text where numbers of one or two digits stand upright
const layout = { layoutType: 'single', writingMode: 'vertical-rl' }; // binding 'auto': right
const cjk = {
  // 10月10日: each number of up to two digits stands upright in one cell (tate-chu-yoko);
  // 1912 and Sun Yat-sen stay on their side, as clreq sets long numbers and Latin words.
  uprightDigits: 2,
  // The type area in characters: 44 down each line, 19 lines to the page.
  grid: { enabled: true, charsPerLine: CHARS, linesPerPage: 19 },
};
// By hand, in the Markdown: 民國:tcy[115]年 puts three digits in one cell, :upright[ROC]
// stands each letter of an acronym upright, :sideways[…] turns any run with the line.
// #endregion

// #region opener: a vermilion band down the right edge, where each document begins
// The margins are minimums: the grid centres the 44 characters (186.3 mm) between them,
// so the type area starts HEAD mm down the sheet. The band's title starts there too.
const HEAD = MARGIN.top + (TRIM.h - MARGIN.top - MARGIN.bottom - LINE) / 2;
const BAND = 42; // mm from the right trim edge: where a reader of vertical text starts
const onBand = { color: col('paper'), overflow: 'wrap' };
// In the flow of a vertical page x runs down the sheet and y leftward from its right edge.
const at = (x, y, extra = {}) => ({ anchor: { to: 'page', edge: 'top-left' },
  offset: { x: mm(x), y: mm(y) }, ...extra });
const opener = {
  enabled: true,
  minHeight: mm(BAND - 15), // past the side margin (21.6 mm), 6 mm of paper before the text
  slot: { elements: [
    { kind: 'box', id: 'band', style: { backgroundColor: col('seal') },
      placement: { anchor: { to: 'bleed', edge: 'top-left' }, size: { height: mm(BAND) } } },
    { kind: 'text', id: 'title', content: '{titleText}', ...onBand, fontFamily: HEI,
      fontWeight: 700, fontSize: pt(34), lineHeight: 1.2, letterSpacing: pt(4), align: 'left',
      placement: at(HEAD, 8) },
    { kind: 'text', id: 'latin', content: '{attr.latin}', ...onBand, fontFamily: HEI,
      fontSize: pt(9), lineHeight: 1.6, align: 'left', placement: at(HEAD, 25) },
    // The date ends where the lines of text end: align 'right' is the foot of a vertical line.
    { kind: 'text', id: 'date', content: '{attr.date}', ...onBand, fontFamily: HEI,
      fontWeight: 500, fontSize: pt(13), lineHeight: 1.2, align: 'right',
      placement: at(HEAD, 24, { size: { width: mm(LINE) } }) },
  ] },
};
// #endregion

// #region heads: fore-edge heads, the folio in Chinese numerals
const foreEdge = (id, content, edge, y) => ({
  kind: 'text', id, content, writingMode: 'vertical-rl', pages: 'body', align: 'left',
  fontFamily: HEI, fontSize: pt(9.6), color: col('muted'), overflow: 'clip',
  placement: { anchor: { to: 'outer', edge }, offset: { y: em(y) } },
});
const header = { elements: [
  foreEdge('head', '{chapterTitle}', 'top', 4), // four characters below the type area
  foreEdge('folio', '{pageNumber}', 'bottom', -5), // ends five characters above its foot
] };
// #endregion

// #region cover: the title page, a vermilion field inside a double rule
const frame = (id, inset, width) => ({ kind: 'box', id,
  style: { borderColor: col('tint'), borderWidth: pt(width) },
  placement: at(inset, inset, { size: { width: mm(TRIM.h - 2 * inset),
    height: mm(TRIM.w - 2 * inset) } }) });
const coverLine = (id, content, y, align) => ({ kind: 'text', id, content, ...onBand,
  fontFamily: HEI, fontWeight: 500, fontSize: pt(18), lineHeight: 1.2, align,
  placement: at(HEAD, y, { size: { width: mm(LINE) } }) });
const cover = {
  id: 'cover', numbered: false, toc: false, runningChapter: false,
  span: 'page', // a page-wide design is not cut at the foot of the column: the field bleeds
  header: { elements: [] }, footer: { elements: [] },
  advancedDesign: { enabled: true, slot: { elements: [
    { kind: 'box', id: 'field', style: { backgroundColor: col('seal') },
      placement: { anchor: { to: 'bleed', edge: 'top-left' }, size: { height: mm(TRIM.w) } } },
    frame('rule-outer', 11, 1.6), frame('rule-inner', 13, 0.5), // 文武線: thick, then thin
    { kind: 'text', id: 'title', content: '{titleText}', ...onBand, fontFamily: HEI,
      fontWeight: 700, fontSize: pt(56), lineHeight: 1.1, letterSpacing: pt(5.6), align: 'left',
      placement: at(HEAD, 26) },
    { kind: 'text', id: 'latin', content: '{attr.latin}', ...onBand, fontFamily: HEI,
      fontSize: pt(11), lineHeight: 1.4, align: 'left', placement: at(HEAD, 51) },
    coverLine('first', '臨時大總統宣言書', 104, 'left'),
    coverLine('first-date', '1912年1月1日', 104, 'right'),
    coverLine('second', '中華民國臨時約法', 118, 'left'),
    coverLine('second-date', '1912年3月11日', 118, 'right'),
  ] } },
};
// #endregion

const config = () => ({
  locale: 'zh-Hant', // Taiwan conventions: centred punctuation (gotcha: cjk-locale-tag)
  colorPalette,
  page: {
    sizePreset: 'custom', width: mm(TRIM.w), height: mm(TRIM.h), dpi: 150,
    backgroundColor: col('paper'),
    margins: { top: mm(MARGIN.top), bottom: mm(MARGIN.bottom), left: mm(MARGIN.side),
      right: mm(MARGIN.side), mirror: true },
    pageNumbering: { format: 'trad-chinese-informal' }, // 一, 二, 三…
  },
  layout,
  cjk,
  bodyText: {
    fontFamily: SONG, fontSize: pt(BODY), lineHeight: pt(LEAD), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
    textAlign: 'justify', firstLineIndent: em(2), indentAfterHeading: true,
  },
  headings: {
    fontFamily: HEI, color: col('seal'), fontWeight: 700,
    levels: [
      // Each document opens on the next page, whichever side that is.
      { level: 1, breakBefore: { enabled: true, parity: 'any' }, advancedDesign: opener },
      { level: 2, fontSize: pt(BODY), lineHeight: pt(LEAD), marginTop: pt(LEAD),
        marginBottom: pt(0) },
    ],
  },
  headingStyles: [cover],
  paragraphStyles: [
    // 低二格: the editor's Kai, two body cells lower (pt: the Kai's own em is off the grid).
    { id: 'headnote', fontFamily: KAI, fontSize: pt(10.5), lineHeight: pt(LEAD), color: col('ink'),
      indent: pt(2 * BODY), firstLineIndent: pt(2 * BODY), marginBottom: pt(LEAD) },
    { id: 'note', fontFamily: KAI, fontSize: pt(10.5), lineHeight: pt(LEAD),
      color: col('ink'), firstLineIndent: pt(0), hangingIndent: em(1) },
    { id: 'order', firstLineIndent: em(2), marginTop: pt(0) },
    { id: 'dateline', textAlign: 'left', indent: em(12), firstLineIndent: pt(0) },
    // The seal notice starts 22 cells down, a cell past the end of 大中華民國元年元旦.
    { id: 'seal', fontFamily: HEI, fontSize: pt(10.5), color: col('seal'), textAlign: 'left',
      indent: pt(22 * BODY), firstLineIndent: pt(0) },
    { id: 'article', firstLineIndent: pt(0), hangingIndent: em(2) },
    { id: 'item', indent: em(2), firstLineIndent: pt(0), hangingIndent: em(2) },
    { id: 'colophon', fontFamily: HEI, fontSize: pt(7.5), lineHeight: pt(LEAD),
      color: col('muted'), textAlign: 'left', firstLineIndent: pt(0), marginTop: pt(LEAD) },
  ],
  header,
  footer: { elements: [] },
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Markdown-Beispiel · 139 Zeilen · content.en.md
title: "民國元年文告二種"
author: "孫文　臨時參議院"
---

# 民國元年文告二種 {style="cover" latin="Two founding documents of 1912"}

# 臨時大總統宣言書 {date="1912年1月1日" latin="Proclamation of the Provisional President"}

:::paragraphs{style="headnote"}
1912年1月1日晚上10時，孫文在南京就任中華民國臨時大總統，宣誓受印之後，以這篇宣言書布告國民。同月29日《臨時政府公報》創刊，第1號第3至6頁刊出全文，題作〈臨時大總統宣言書〉，字句略異。本篇據廣州市博物館藏原件排印；原件沒有標點，也不分段，標點與分段從維基文庫整理本。
:::

中華民國締造之始，而文以不德，膺臨時大總統之任，夙夜戒懼，慮無以副國民之望。夫中國專制政治之毒，至二百餘年來而滋甚，一旦以國民之力踣而去之，起事不過數旬，光復已十餘行省，自有歷史以來成功未有如是之速也。國民以為於內無統一之機關，於外無對待之主體，建設之事更不容緩，於是以組織臨時政府之責相屬。自推功讓能之觀念以言，文所不敢任也；自服務盡責之觀念以言，則文所不敢辭也。是用黽勉從國民之後，能盡掃專制之流毒，確定共和，以達革命之宗旨，完國民之志願，端在今日。敢披瀝肝膽，為國民告：

國家之本，在於人民。合漢、滿、蒙、回、藏諸地為一國，即合漢、滿、蒙、回、藏諸族為一人。——是曰民族之統一。

武漢首義，十數行省先後獨立。所謂獨立，對於清廷為脫離，對於各省為聯合。蒙古、西藏，意亦同此。行動既一，決無歧趨，樞機成於中央，斯經緯周於四至。——是曰領土之統一。

血鐘一鳴，義旗四起，擁甲帶戈之士遍於十餘行省。雖編製或不一，號令或不齊，而目的所在則無不同。由共同之目的，以為共同之行動，整齊劃一，夫豈其難？——是曰軍政之統一。

國家幅員遼闊，各省自有其風氣所宜。前此清廷強以中央集權之法行之，遂其偽立憲之術；今者各省聯合，互謀自治，此後行政，期於中央政府與各省之關係調劑得宜。大綱既挈，條目自舉。——是曰內治之統一。

滿清時代，借立憲之名，行斂財之實，雜捐苛細，民不聊生。此後國家經費，取給於民，必期合於理財學理，而尤在改良社會經濟組織，使人民知有生之樂。——是曰財政之統一。

以上數者，為政務之方針，持此進行，庶無大過。

若夫革命主義，為吾儕所昌言，萬國所同喻，前此雖屢起屢躓，外人無不鑒其用心。八月以來，義旗飆發，諸友邦對之抱和平之望、持中立之態，而報紙及輿論尤每表其同情。鄰誼之篤，良足深謝。臨時政府成立以後，當盡文明國應盡之義務，以期享文明國應享之權利。滿清時代辱國之舉措與排外之心理，務一洗而去之。與我友邦益增睦誼，持和平主義，將使中國見重於國際社會，且將使世界漸趨於大同。循序以進，不為幸獲。對外方針，實在於是。

夫民國新建，外交內政百緒繁生，文自顧何人，而克勝此？然而臨時之政府，革命時代之政府也。十餘年來從事於革命者，皆以誠摯純潔之精神戰勝所遇之艱難。即使後此之艱難遠逾於前日，而吾人惟保此革命之精神，一往而莫之能阻，必使中華民國之基礎確定於大地，然後臨時政府之職務始盡，而吾人始可告無罪於國民也。今以與我國民初相見之日，披布腹心，惟我四萬萬之同胞共鑒之。

:::paragraphs{style="dateline"}
大中華民國元年元旦
:::

:::paragraphs{style="seal"}
（中華民國臨時大總統印）
:::

## 注釋

:::paragraphs{style="note"}
【中華民國】1912年1月1日建立。英文國號作 Republic of China，縮寫:upright[ROC]。

【文以不德】文，孫文自稱其名；不德，自謙德行不足。孫文號逸仙，西文拼作 Sun Yat-sen（1866—1925）。

【二百餘年】指清朝的統治。清兵1644年入關，至1912年2月12日宣統帝退位，凡:tcy[268]年。

【八月以來】辛亥年八月十九日（1911年10月10日）武昌起義以來。

【四萬萬之同胞】四萬萬，四億。當時以此通稱全國人口。

【大中華民國元年元旦】1912年1月1日，夏曆辛亥年十一月十三日。民國紀年由此日起算，當年稱民國元年。公元2026年是民國:tcy[115]年。
:::

# 中華民國臨時約法 {date="1912年3月11日" latin="Provisional Constitution of the Republic of China"}

:::paragraphs{style="headnote"}
1912年3月8日，南京臨時參議院議決《中華民國臨時約法》；3月11日，臨時大總統孫文公布施行，全文刊於《臨時政府公報》第35號。約法凡7章56條，本篇錄第一章〈總綱〉與第二章〈人民〉，共15條，前冠公布令。原文的「爲」「靑」「敎」「决」，本篇改用通行字形。
:::

:::paragraphs{style="order"}
玆准參議院咨送議決臨時約法前來，合行公布。
:::

:::paragraphs{style="seal"}
孫文印
:::

:::paragraphs{style="dateline"}
中華民國元年三月十一日
:::

## 第一章　總綱

:::paragraphs{style="article"}
第一條　中華民國由中華人民組織之。

第二條　中華民國之主權屬於國民全體。

第三條　中華民國領土，為二十二行省、內外蒙古、西藏、青海。

第四條　中華民國以參議院、臨時大總統、國務院、法院行使其統治權。
:::

## 第二章　人民

:::paragraphs{style="article"}
第五條　中華民國人民一律平等，無種族、階級、宗教之區別。

第六條　人民得享有左列各項之自由權：
:::

:::paragraphs{style="item"}
一、人民之身體，非依法律不得逮捕、拘禁、審問、處罰。

二、人民之家宅，非依法律不得侵入或搜索。

三、人民有保有財產及營業之自由。

四、人民有言論、著作、刊行及集會結社之自由。

五、人民有書信秘密之自由。

六、人民有居住遷徙之自由。

七、人民有信教之自由。
:::

:::paragraphs{style="article"}
第七條　人民有請願於議會之權。

第八條　人民有陳訴於行政官署之權。

第九條　人民有訴訟於法院受其審判之權。

第十條　人民對於官吏違法損害權利之行為，有陳訴於平政院之權。

第十一條　人民有應任官考試之權。

第十二條　人民有選舉及被選舉之權。

第十三條　人民依法律有納稅之義務。

第十四條　人民依法律有服兵之義務。

第十五條　本章所載人民之權利，有認為增進公益、維持治安或非常緊急必要時，得依法律限制之。
:::

## 注釋

:::paragraphs{style="note"}
【參議院】臨時參議院，1912年1月28日在南京開院，參議員由各省都督府選派，每省至多3人。

【二十二行省】清末本部十八省，加上東三省與新疆，合稱二十二行省。
:::

:::paragraphs{style="colophon"}
Set in Noto Serif TC, Noto Sans TC and LXGW WenKai TC (SIL OFL) · Texts: zh.wikisource, CC BY-SA 4.0 · Headnotes and notes: CC BY 4.0
:::
`; // content.<lang>.md, inlined by the Cookbook

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
// Every face the pages paint; the Chinese ones by files (gotcha: cjk-fonts-slices).
const FONTS = { 'Noto Serif TC': ['400'], 'Noto Sans TC': ['400', '500', '700'],
  'LXGW WenKai TC': ['400'] };
// #region voices: each Chinese face loads the files for the text it sets
const voice = (styles) => (markdown.match(
  new RegExp(`:::paragraphs\\{style="(?:${styles})"\\}[\\s\\S]*?:::`, 'g')) ?? []).join('');
const kaiText = voice('headnote|note');
// Hei: headings and their attributes, seals, colophon, the cover's lines, folios 一 to 十.
const heiText = (markdown.match(/^#.*$/gm) ?? []).join('') + voice('seal|colophon')
  + '臨時大總統宣言書1912年1月1日中華民國臨時約法1912年3月11日一二三四五六七八九十';
// #endregion

// ─── 4 · Build & show ───────────────────────────────────────────────────────
await loadFonts(FONTS, markdown);
await loadCjkFonts({ [SONG]: FONTS[SONG] }, markdown, { vertical: true });
await loadCjkFonts({ [HEI]: FONTS[HEI] }, heiText, { vertical: true });
await loadCjkFonts({ [KAI]: FONTS[KAI] }, kaiText, { vertical: true });
const doc = await withLoadedFonts(() => buildDocument({ markdown }, config()),
  { ...kitFonts(FONTS), text: markdown });
showBook(doc, { title: t({ en: 'Two documents of 1912', es: 'Dos documentos de 1912' }) });
offerPdf(() => renderToPdf(doc, { fontProvider: cjkPdfProvider }), `${RECIPE}.pdf`);

Kit · core, fonts, viewer, pdf, cjk: in jedem Rezept gleich · 458 Zeilen
// ─── 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 v3 ── the same in every recipe · postext.dev/cookbook
// Postext loads the faces a config asks for before layout (prepareFonts,
// buildDocumentWithFonts) and asks the kit for the files: Fontsource's, the
// files the PDF embeds too.

/** The options of buildDocumentWithFonts / prepareFonts / withLoadedFonts:
 *  the Fontsource resolver, and the faces of FONTS loaded with the ones the
 *  config names. FONTS = { 'Family Name': ['400', '400i', '700'] }. */
function kitFonts(FONTS = {}) {
  const faces = Object.entries(FONTS).flatMap(([family, specs]) => specs.map((spec) =>
    ({ family, weight: parseInt(spec, 10), style: spec.endsWith('i') ? 'italic' : 'normal' })));
  return { resolve: fontsourceResolver, faces };
}

/** A face's Fontsource files, in a fixed order: latin, then latin-ext and greek
 *  when `text` needs them and the family ships them (kitSubsetsFor), each with
 *  its unicode-range. Null for a weight or slant Fontsource does not ship. */
async function fontsourceResolver(family, weight, style, { text = '' } = {}) {
  const id = fontsourceId(family);
  const meta = await fontsourceMeta(family);
  if (meta && !(meta.weights.includes(weight) && meta.styles.includes(style))) return null;
  kitStatus('Loading fonts…');
  const at = await fontsourceAt(id);
  return ['latin', ...kitSubsetsFor(text, meta)].map((subset) => ({
    source: `${at}files/${id}-${subset}-${weight}-${style}.woff2`,
    unicodeRange: kitRanges()[subset],
  }));
}

/** The unicode-range of each Fontsource file the kit loads (a function: the
 *  kit is inlined after the pen's code, which runs before a const would be set). */
function kitRanges() {
  return {
    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',
    greek: 'U+0370-03FF',
  };
}

/** For the cjk, arabic and comics blocks, which add their own files: the
 *  faces of `faces` = { 'Family Name': ['400', '400i', '700'] }. `text` is the sample:
 *  č ł † α χ also load latin-ext and greek files (kitSubsetsFor). With
 *  `optional`, a face Fontsource does not ship is skipped instead of failing.
 *  The files are added once all have loaded, in the order asked (latin, then
 *  latin-ext, then greek), whatever order they arrive in: the last one added
 *  wins a character two files hold. Resolves to the number of faces added. */
async function loadFonts(faces, text = '', { optional = false } = {}) {
  kitStatus('Loading fonts…');
  const ranges = kitRanges();
  const jobs = [];
  for (const [family, specs] of Object.entries(faces)) {
    const id = fontsourceId(family);
    const todo = [...new Set(specs)].map((spec) => [parseInt(spec, 10), spec.endsWith('i') ? 'italic' : 'normal'])
      .filter(([weight, style]) => !hasFace(family, weight, style)); // before any await
    const at = fontsourceAt(id);
    const meta = optional || /[^\0-ÿ]/u.test(text) ? await fontsourceMeta(family) : null;
    const subsets = ['latin', ...kitSubsetsFor(text, meta)];
    for (const [weight, style] of todo) {
      if (optional && !(meta?.weights.includes(weight) && meta.styles.includes(style))) continue;
      for (const subset of subsets) {
        const url = `${await at}files/${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().catch(() => {
          if (subset === 'latin' && !optional) throw new Error(`Fontsource has no ${family} ${weight} ${style}`);
        }));
      }
    }
  }
  const ready = await Promise.all(jobs).catch((error) => { kitFail(error); throw error; });
  return ready.filter((face) => face && document.fonts.add(face)).length;
}

/** A loaded FontFace covers this family, weight and style (fonts.check() would
 *  also say yes 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;
}

/** The files beyond latin `text` needs that `meta`'s family ships. */
function kitSubsetsFor(text, meta) {
  return [[/[Ā-˿ᴀ-ᶿḀ-ỿ†ℓⱠ-Ɀ꜠-ꟿ]/u, 'latin-ext'], [/[Ͱ-Ͽ]/u, 'greek']]
    .filter(([re, x]) => re.test(text) && meta?.subsets?.includes(x)).map(([, x]) => x);
}

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

/** A package's folder at the one version @5 names now (#766). */
function fontsourceAt(id, u = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@`) {
  return (fontsourceAt.c ??= {})[id] ??= fetch(u + '5/package.json').then((r) => r.json())
    .then((p) => p.version || 5, () => 5).then((v) => `${u}${v}/`);
}

/** The family's Fontsource metadata (weights, styles, subsets), 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 v2 ── the same in every recipe · postext.dev/cookbook
/** The pages as spreads on a dark desk, page 1 alone, then verso | recto,
 *  each painted when it scrolls near. Other options go to renderPageToCanvas. */
function showPages(docs, { title, width = 460, ...render } = {}) {
  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, { ...render, 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 v3 ── the same in every recipe that exports a PDF
/** The Fontsource files the screen used, as TrueType, with their range and
 *  place: the nearest weight the family ships, upright with no italic;
 *  latin, then what its letters need (kitSubsetsFor). */
async function fontsourceProvider(family, weight, style, request) {
  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 text = String.fromCodePoint(...(request?.codePoints ?? []));
  const files = await Promise.all(['latin', ...kitSubsetsFor(text, meta)].map(async (subset, order) => {
    const res = await fetch(`${await fontsourceAt(id)}files/${id}-${subset}-${w}-${s}.woff2`);
    if (!res.ok) throw new Error(`Fontsource has no ${family} ${w} ${s} ${subset}`);
    return Object.assign(await decompressWoff2(new Uint8Array(await res.arrayBuffer())),
      { unicodeRange: kitRanges()[subset], order });
  }));
  return files.length === 1 ? files[0] : files;
}

/** A "Build the PDF" button; then "Open the PDF" (a new tab: CodePen's frame
 *  shows no 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 v2 ── 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 = `${id}/${weight}${style === 'italic' ? '-italic' : ''}.css`;
  if (!cjkSlices.cache.has(css)) {
    let at;
    cjkSlices.cache.set(css, fontsourceAt(id).then((a) => fetch(at = a + css.slice(id.length + 1)))
      .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], at).href, range, ranges };
      }).reverse()));
  }
  return cjkSlices.cache.get(css);
}

/** The file of `slices` the screen sets code point `cp` in, if any: the
 *  last one loadCjkFonts adds whose range holds it. A numbered file that
 *  repeats a letter of latin is added after latin, and wins it. */
function cjkSliceFor(slices, cp) {
  const holds = (slice) => slice.ranges.some(([lo, hi]) => cp >= lo && cp <= hi);
  return slices.reduce((last, slice) => (holds(slice) ? slice : last), undefined);
}

/** 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 the engine's later round
 *  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 the
 *  screen set its pages' characters in (`request.codePoints`), each marked
 *  with its unicode-range and its place in the order loadCjkFonts added
 *  them: postext-pdf sets a character two files hold in the one added
 *  last, as the browser does. 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.map(async (slice, order) => {
    if (!picked.has(slice)) return null;
    const res = await fetch(slice.url);
    if (!res.ok) throw new Error(`Fontsource file ${slice.url} (${res.status})`);
    const bytes = await decompressWoff2(new Uint8Array(await res.arrayBuffer()));
    return Object.assign(bytes, { unicodeRange: slice.range, order });
  })).then((files) => files.filter(Boolean));
}

/** 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, each marked with its unicode-range and its place in that order:
 *  the PDF sets a character in the file the browser took it from. 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 = `${await fontsourceAt(id)}files/${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)]);
  const ranges = kitRanges();
  return ext ? [Object.assign(latin, { unicodeRange: ranges.latin, order: 0 }),
    Object.assign(ext, { unicodeRange: ranges['latin-ext'], order: 1 })] : 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 ───────────────────────────────────────────────────────────────────────