Um relatório bilíngue árabe-inglês

// ═══ Postext Cookbook · Nº 106 · A bilingual Arabic–English report ═══════════════════
// https://postext.dev/en/cookbook/bilingual-arabic-english-report
// Code: MIT · Text: original Arabic, English and Spanish prose (CC BY 4.0) · Pictures: none
// Fonts: IBM Plex Sans Arabic, IBM Plex Sans (SIL OFL 1.1) · Needs postext ≥ 1.15.0
import {
  buildDocument, renderPageToCanvas, clearMeasurementCache, defaultResourceTypes,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'en'; // @lang: the second language of the report: English, or Spanish in 'es'
const RECIPE = 'bilingual-arabic-english-report';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: a deep teal for the Arabic, a slate for the second language
const palette = {
  ink: '#1b1f22', // the Arabic text
  teal: '#0e5a5c', // the accent: the cover band, headings, table heads
  slate: '#45535c', // the English (or Spanish) text: a voice of its own, a step lighter
  tint: '#e4eeec', // the second language's panels
  rule: '#b9c4c2', // hairlines
  paper: '#ffffff',
};
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = Object.entries({ ...palette, 'main-color': palette.teal })
  .map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } }));
// #endregion
const [ARABIC, LATIN] = ['IBM Plex Sans Arabic', 'IBM Plex Sans']; // one superfamily
const LEAD = 18; // pt: the Arabic leading
const SIDE = 20; // mm: the side margins

// #region answer: one Arabic document, its English blocks marked {dir=ltr}
// The document is Arabic (locale 'ar'): right to left, Arabic-Indic digits. A block in the
// other language says so in the Markdown, and its style gives it its own voice:
//   :::paragraphs{style="second" dir=ltr}      a paragraph or several, set left to right
//   ### Director's note {style="second-head" dir=ltr}
// Inside an Arabic sentence, a Latin name is an isolate, :ltr[Penguin Classics]{lang=en}, so
// the words around it keep their order. 'start' and 'end' follow each block's own direction.
const second = { id: 'second', fontFamily: LATIN, fontSize: pt(9.5), lineHeight: pt(14),
  color: col('slate'), textAlign: 'start', firstLineIndent: pt(0) };
const bodyText = { fontFamily: ARABIC, fontSize: pt(11), lineHeight: pt(LEAD),
  color: col('ink'), boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
  textAlign: 'start', // ragged: the right edge for Arabic, the left for an English block
  firstLineIndent: pt(0), paragraphSpacing: true,
  // The Arabic is never slanted; italics stay for the titles in the Latin blocks.
  emphasis: 'italic' };
// #endregion

// #region tables: the Arabic table runs with the page; the English one runs left to right
const cell = (content, extra = {}) => ({ content, ...extra });
const tableOf = (head, rows) => ({ headerRowCount: 1, columnWidths: [46, 18, 18, 18],
  rows: [head.map((h, i) => cell(h, { isHeader: true, align: i ? 'end' : 'start' })),
    ...rows.map((r) => r.map((c, i) => cell(c, { align: i ? 'end' : 'start' })))] });
const FIGURES = [ // programme, 2024, 2025, change: the Foundation's own counts
  ['كتب مترجمة إلى العربية', 'Books translated into Arabic', 28, 34],
  ['كتب مترجمة من العربية', 'Books translated from Arabic', 9, 14],
  ['منح للمترجمين', 'Translator grants', 41, 52],
  ['ورشات تدريب', 'Training workshops', 12, 18],
  ['مشاركون في الورشات', 'Workshop participants', 310, 466]];
const SPANISH = { 'Books translated into Arabic': 'Libros traducidos al árabe',
  'Books translated from Arabic': 'Libros traducidos del árabe',
  'Translator grants': 'Becas para traductores', 'Training workshops': 'Talleres de formación',
  'Workshop participants': 'Participantes en los talleres' };
const change = (a, b) => `${b > a ? '+' : ''}${Math.round((100 * (b - a)) / a)}%`;
const AR = (n) => String(n).replace(/\d/g, (d) => '٠١٢٣٤٥٦٧٨٩'[d]); // the author's ٠–٩
const tableAr = tableOf(['البرنامج', '٢٠٢٤', '٢٠٢٥', 'التغيّر'], FIGURES.map(([ar, , a, b]) =>
  [ar, AR(a), AR(b), AR(change(a, b)).replace('%', '٪')]));
const tableEn = tableOf(t({ en: ['Programme', '2024', '2025', 'Change'],
  es: ['Programa', '2024', '2025', 'Cambio'] }), FIGURES.map(([, en, a, b]) =>
  [t({ en, es: SPANISH[en] }), String(a), String(b), change(a, b)]));
// The English table has a heading of its own and no number: a generated number would print in
// the document's digits, ٢, inside the English block.
const resourceTypes = [...defaultResourceTypes('ar'), { id: 'data', name: 'Data',
  shortLabel: 'Data', captionPrefix: '', numberingTemplate: '', resetOn: 'never',
  counterFormat: 'decimal' }];
const resources = [
  { id: 'figures-ar', typeId: 'table', kind: 'table', createdAt: 0, updatedAt: 0,
    table: { model: tableAr }, placement: { position: 'here' },
    caption: 'أرقام البرامج في عامي ٢٠٢٤ و٢٠٢٥' },
  { id: 'figures-en', typeId: 'data', kind: 'table', createdAt: 0, updatedAt: 0,
    table: { model: tableEn, direction: 'ltr', styleId: 'second' },
    placement: { position: 'here' } },
];
// #endregion

// #region cover: the report's two titles on a teal band, each in its own direction
const band = { enabled: true, minHeight: mm(70), slot: { elements: [
  { kind: 'box', id: 'band', style: { backgroundColor: col('teal') },
    placement: { anchor: { to: 'bleed', edge: 'top-left' },
      size: { width: mm(216), height: mm(86) } } },
  // Design text takes the document's direction; an English title says 'ltr' and aligns left.
  { kind: 'text', id: 'org', content: '{attr.org}', fontFamily: ARABIC, fontSize: pt(13),
    fontWeight: 600, color: col('tint'), align: 'right',
    placement: { anchor: { to: 'page', edge: 'top-right' }, offset: { x: mm(-SIDE), y: mm(18) } } },
  { kind: 'text', id: 'title', content: '{titleText}', fontFamily: ARABIC, fontSize: pt(50),
    fontWeight: 700, lineHeight: 1.15, color: col('paper'), align: 'right',
    placement: { anchor: { to: 'page', edge: 'top-right' }, offset: { x: mm(-SIDE), y: mm(30) } } },
  { kind: 'text', id: 'title-2', content: '{attr.second}', direction: 'ltr', fontFamily: LATIN,
    fontSize: pt(20), fontWeight: 300, color: col('tint'), align: 'left',
    placement: { anchor: { to: 'page', edge: 'top-left' }, offset: { x: mm(SIDE), y: mm(66) } } },
] } };
// #endregion

const config = () => ({ // a factory: the engine caches resolved configs per object
  locale: 'ar', // written out, never LANG (gotcha: arabic-locale-tag)
  colorPalette, bodyText, resourceTypes,
  page: { width: mm(210), height: mm(280), dpi: 150,
    margins: { top: mm(22), bottom: mm(22), left: mm(SIDE), right: mm(SIDE), mirror: true } },
  layout: { layoutType: 'single' },
  headings: { fontFamily: ARABIC, fontWeight: 700, color: col('teal'), levels: [
    // Restated: any headings object drops the H1 break (gotcha: headings-drop-h1-break).
    { level: 1, breakBefore: { enabled: true, parity: 'any' }, marginTop: pt(0),
      marginBottom: pt(0), advancedDesign: band },
    { level: 2, fontSize: pt(17), lineHeight: pt(26), marginTop: pt(LEAD), marginBottom: pt(0) },
  ] },
  headingStyles: [{ id: 'second-head', fontFamily: LATIN, fontSize: pt(10), fontWeight: 600,
    lineHeight: pt(14), color: col('slate'), marginTop: pt(0), marginBottom: pt(4) }],
  paragraphStyles: [second,
    { id: 'colophon', fontFamily: LATIN, fontSize: pt(7.5), lineHeight: pt(10),
      color: col('slate'), textAlign: 'start', firstLineIndent: pt(0), marginTop: pt(LEAD) }],
  tableStyle: { rules: 'horizontal', borderColor: col('rule'), borderWidth: pt(0.5),
    headerBackground: col('teal'), headerColor: col('paper'), headerFontFamily: ARABIC,
    headerFontSize: pt(9.5), bodyFontFamily: ARABIC, bodyFontSize: pt(10), bodyColor: col('ink'),
    cellPadding: mm(1.6) },
  tableStyles: [{ id: 'second', headerBackground: col('slate'), headerFontFamily: LATIN,
    bodyFontFamily: LATIN, bodyFontSize: pt(9), bodyColor: col('slate') }],
  captionStyle: { fontFamily: ARABIC, fontSize: pt(9.5), color: col('ink'), position: 'above',
    labelBold: true, labelColor: col('teal'), labelSeparator: ': ' },
  header: { elements: [] },
  footer: { elements: [{ kind: 'text', id: 'folio', content: '{pageNumber}', pages: 'body',
    fontFamily: ARABIC, fontSize: pt(9), fontWeight: 600, color: col('teal'), align: 'center',
    placement: { anchor: { to: 'page', edge: 'bottom' }, offset: { y: mm(-12) } } }] },
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Amostra em Markdown · 60 linhas · content.en.md
title: "التقرير السنوي ٢٠٢٥"
---

# التقرير السنوي ٢٠٢٥ {org="مؤسسة دار الضاد للترجمة" second="Dar al-Dad Translation Foundation · Annual Report 2025"}

## كلمة المديرة

### Director's note {style="second-head" dir=ltr}

كان عام ٢٠٢٥ أكثر أعوام المؤسسة نشاطًا منذ تأسيسها. فقد صدر في هذا العام ٣٤ كتابًا مترجمًا إلى العربية و١٤ كتابًا مترجمًا منها، ومنحنا ٥٢ منحة لمترجمين من تسعة بلدان، وأقمنا ١٨ ورشة تدريب حضرها ٤٦٦ مشاركًا ومشاركة.

:::paragraphs{style="second" dir=ltr}
2025 was the busiest year in the Foundation's history. We published 34 books translated into Arabic and 14 translated from it, awarded 52 grants to translators from nine countries, and ran 18 training workshops attended by 466 people.
:::

وأكثر ما يسعدنا في هذه الأرقام أن الترجمة من العربية بدأت تلحق بالترجمة إليها. فقد كان الكتاب المترجم من العربية قبل خمس سنوات يقابله أكثر من ستة كتب مترجمة إليها، وصار اليوم يقابله كتابان ونصف. وقد صدرت روايتان من الكتب التي دعمناها في سلسلة :ltr[Harbour Modern Classics]{lang=en}، وهي المرة الأولى التي تدخل فيها روايات عربية معاصرة هذه السلسلة بدعم منا.

:::paragraphs{style="second" dir=ltr}
What pleases us most in these figures is that translation from Arabic has begun to catch up with translation into it. Five years ago, every book we supported out of Arabic was matched by more than six into it; today the ratio is two and a half to one. Two of the novels we supported appeared in Harbour Modern Classics.
:::

## أرقام العام

### The year in figures {style="second-head" dir=ltr}

يعرض الجدول التالي برامج المؤسسة الخمسة في العامين الأخيرين، والنسبة التي تغيّر بها كل برنامج. وتُحسب المنح في السنة التي صُرفت فيها، لا في السنة التي قُدّم فيها الطلب.

::resource{id="figures-ar"}

:::paragraphs{style="second" dir=ltr}
The table below gives the same figures in English. Grants are counted in the year they were paid, not the year they were applied for.
:::

::resource{id="figures-en"}

## البرامج

### Programmes {style="second-head" dir=ltr}

**الترجمة إلى العربية.** نختار الكتب بالتشاور مع لجنة من الناشرين والمترجمين تجتمع مرتين في السنة. ومن أبرز ما صدر هذا العام ترجمة جديدة لرواية :ltr[Middlemarch]{lang=en} لجورج إليوت، ومختارات من مقالات :ltr[Michel de Montaigne]{lang=fr} في الصداقة والسفر والقراءة.

:::paragraphs{style="second" dir=ltr}
**Translation into Arabic.** Titles are chosen with a committee of publishers and translators that meets twice a year. This year's list includes a new translation of George Eliot's *Middlemarch* and a selection of Montaigne's essays on friendship, travel and reading.
:::

**الترجمة من العربية.** نموّل نصف تكاليف الترجمة للناشر الأجنبي الذي يشتري حقوق كتاب عربي، ونرافق المترجم بمحرر يقرأ ترجمته مع النص الأصلي. وصدرت هذا العام كتب مترجمة إلى الإنجليزية والإسبانية والتركية والإندونيسية.

:::paragraphs{style="second" dir=ltr}
**Translation from Arabic.** We pay half the translation costs of a foreign publisher who buys the rights to an Arabic book, and pair the translator with an editor who reads the translation against the original. This year's books appeared in English, Spanish, Turkish and Indonesian.
:::

**التدريب.** تستمر الورشة الواحدة خمسة أيام، ويعمل فيها المشاركون على نص واحد بإشراف مترجمَين اثنين، أحدهما ينقل إلى العربية والآخر ينقل منها. وقد أضفنا هذا العام ورشة للترجمة الأدبية للأطفال، وأخرى لترجمة الشعر.

:::paragraphs{style="second" dir=ltr}
**Training.** Each workshop runs for five days, and its participants work on a single text with two tutors, one translating into Arabic and one out of it. This year we added a workshop on children's literature and another on poetry.
:::

:::paragraphs{style="colophon" dir=ltr}
A specimen report written for the Postext Cookbook; the Foundation, its figures and its people are invented. Set in IBM Plex Sans Arabic and IBM Plex Sans (SIL OFL) · Text: CC BY 4.0.
:::
`; // content.<lang>.md: the Arabic, with English or Spanish

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
const FONTS = { // every face the pages use, loaded before the build (gotcha: fonts-first)
  'IBM Plex Sans Arabic': ['400', '600', '700'], // ARABIC: text, headings, tables, folios
  'IBM Plex Sans': ['300', '400', '400i', '600'], // LATIN: the second language, its table
};

// ─── 4 · Build & show ───────────────────────────────────────────────────────
await loadFonts(FONTS, markdown);
// Each Arabic face's letters live in a file of their own (gotcha: arabic-fonts-subset).
await loadArabicFonts(FONTS, markdown + JSON.stringify(resources));
const doc = await buildWithFonts(() => buildDocument({ markdown, resources }, config()), markdown);
showBook(doc, { title: t({ en: 'A bilingual Arabic–English report',
  es: 'Un informe bilingüe árabe-español' }) });
offerPdf(() => renderToPdf(doc, { fontProvider: arabicPdfProvider }), `${RECIPE}.pdf`);

Kit · core, fonts, viewer, pdf, arabic, book: igual em todas as receitas · 417 linhas
// ─── 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 v2 ── the same in every recipe · postext.dev/cookbook
// Postext measures with the loaded faces and caches the widths: load every face
// before the first build, from Fontsource, the files the PDF embeds too.

/** 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.
 *  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',
    greek: 'U+0370-03FF',
  };
  const jobs = [];
  let added = 0;
  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 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 = `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` and loads any face the pages use that FONTS missed (a regular
 *  one with a warning), then clears the measurement cache and builds 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. */
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' };
}

/** 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, '-'); }

/** 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 v1 ── 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. */
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 v2 ── the same in every recipe that exports a PDF
/** The Fontsource files the screen used, as TrueType: the nearest weight the
 *  family ships, upright if it has no italic; latin, then what the face's
 *  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 more = kitSubsetsFor(text, meta);
  const files = await Promise.all(['latin', ...more].map(async (subset) => {
    const res = await fetch(`https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-${subset}-${w}-${s}.woff2`);
    if (!res.ok) throw new Error(`Fontsource has no ${family} ${w} ${s} ${subset}`);
    return decompressWoff2(new Uint8Array(await res.arrayBuffer()));
  }));
  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 · arabic v1 ── Arabic-script faces · postext.dev/cookbook
// Fontsource ships an Arabic family as one file per subset and weight: the
// `arabic` file holds the letters, the harakat, the Arabic-Indic digits, the
// Arabic punctuation and the presentation forms; `latin` and `latin-ext`
// hold the rest. loadFonts loads the latin files; this block adds the arabic
// file of every Arabic family, for the canvas and for the PDF, which shapes
// the letters with HarfBuzz from the same bytes.

/** The code points of Fontsource's `arabic` subset, as its stylesheets
 *  declare them (the same unicode-range the browser picks the file by). A
 *  function, not a const: the kit is inlined after the recipe's top-level
 *  awaits, and a const read before its line throws, where a function
 *  declaration is hoisted. */
function arabicRange() {
  return 'U+0600-06FF,U+0750-077F,U+0870-088E,U+0890-0891,U+0897-08E1,U+08E3-08FF,'
    + 'U+200C-200E,U+2010-2011,U+204F,U+2E41,U+FB50-FDFF,U+FE70-FE74,U+FE76-FEFC,U+102E0-102FB,'
    + 'U+10E60-10E7E,U+10EC2-10EC4,U+10EFC-10EFF,U+1EE00-1EEFF';
}

/** Whether code point `cp` is in the arabic file. */
function inArabicRange(cp) {
  inArabicRange.ranges ??= arabicRange().split(',').map((part) => {
    const [lo, hi = lo] = part.slice(2).split('-');
    return [parseInt(lo, 16), parseInt(hi, 16)];
  });
  return inArabicRange.ranges.some(([lo, hi]) => cp >= lo && cp <= hi);
}

/** Whether Fontsource serves `family` with an `arabic` subset. Fails when
 *  the API does not answer: an Arabic face taken for a Latin one would set
 *  its letters in a system face. */
async function isArabicFamily(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?.includes('arabic');
}

/** The arabic file of a face. */
function arabicFileUrl(family, weight, style) {
  const id = fontsourceId(family);
  return `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-arabic-${weight}-${style}.woff2`;
}

/** faces = { Amiri: ['400', '700'] }, as for loadFonts, after it: the whole
 *  FONTS object may be passed, its families without an arabic subset are
 *  left alone. Adds the arabic file of every listed weight of each Arabic
 *  family (the latin files come from loadFonts) and loads it. `text` is
 *  the sample: fails when it holds an Arabic-script character the arabic
 *  file does not cover. List every weight the pages set in Arabic: a weight
 *  left to buildWithFonts gets the latin file only, and its Arabic letters
 *  fall back to a system face. Resolves to the number of files loaded. */
async function loadArabicFonts(faces, text = '') {
  kitStatus('Loading fonts…');
  let loaded = 0;
  try {
    const outside = [...new Set(text)].filter((ch) => /\p{Script=Arabic}/u.test(ch) && !inArabicRange(ch.codePointAt(0)));
    if (outside.length) throw new Error(`Fontsource's arabic files have no ${outside.slice(0, 12).join(' ')}`);
    for (const [family, specs] of Object.entries(faces)) {
      if (!(await isArabicFamily(family))) continue;
      for (const spec of new Set(specs)) {
        const weight = parseInt(spec, 10);
        const style = spec.endsWith('i') ? 'italic' : 'normal';
        const face = new FontFace(family, `url(${arabicFileUrl(family, weight, style)}) format('woff2')`,
          { weight: String(weight), style, unicodeRange: arabicRange() });
        document.fonts.add(await face.load().catch(() => {
          throw new Error(`Fontsource has no arabic file for ${family} ${weight} ${style}`);
        }));
        loaded++;
      }
    }
  } catch (error) {
    kitFail(error);
    throw error;
  }
  return loaded;
}

/** The PDF font provider for recipes with Arabic faces: a family with an
 *  arabic subset gets its arabic file when its pages set Arabic letters
 *  (`request.codePoints`), then its latin file, and its latin-ext file for
 *  the letters beyond latin (transliteration: ā ḥ ʿ). The arabic file comes
 *  first: it also holds the space and the brackets, so a line of Arabic is
 *  shaped as one run and not cut at every space. Any other family goes to
 *  fontsourceProvider (the "pdf" block). */
async function arabicPdfProvider(family, weight, style, request) {
  if (!(await isArabicFamily(family))) return fontsourceProvider(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 wanted = [...(request?.codePoints ?? [])];
  const id = fontsourceId(family);
  const urls = [];
  if (!wanted.length || wanted.some(inArabicRange)) urls.push(arabicFileUrl(family, w, s));
  urls.push(`https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-${w}-${s}.woff2`);
  if (meta.subsets.includes('latin-ext') && wanted.some((cp) => /[Ā-˿Ḁ-ỿ]/u.test(String.fromCodePoint(cp)))) {
    urls.push(`https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-ext-${w}-${s}.woff2`);
  }
  return Promise.all(urls.map(async (url) => {
    const res = await fetch(url);
    if (!res.ok) throw new Error(`Fontsource file ${url} (${res.status})`);
    return decompressWoff2(new Uint8Array(await res.arrayBuffer()));
  }));
}

// ─── Kit · book v1 ── books bound on either edge · postext.dev/cookbook
// A book bound on the right (Arabic, Hebrew or Persian text, vertical
// Chinese, or page.binding 'right') opens from what a Latin reader calls
// the back: page 1 lies alone on the left of the spine, then [3 | 2].

/** showPages for a book bound on either edge. A right-bound book (the
 *  document says so: doc.binding is 'right' for page.binding 'right', for
 *  text that runs right to left and for vertical text, when the binding is
 *  left to 'auto') 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-book')) {
    // The pages keep direction ltr, as in a left-bound book: a canvas takes
    // the direction its element inherits, and under the spread's rtl a run
    // painted for an ltr canvas would end where the engine starts it.
    document.head.insertAdjacentHTML('beforeend', `<style id="pt-kit-book">
      .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 ───────────────────────────────────────────────────────────────────────