レシピカード：材料と作り方を並べて

// ═══ Postext Cookbook · Nº 033 · Recipe card: ingredients beside the method ═══════
// https://postext.dev/en/cookbook/recipe-card
// Code: MIT · Text: original (CC BY 4.0) · Photos: diffusion models · Pictograms: CC BY 4.0
// Fonts: Young Serif, Figtree, Caveat (SIL OFL 1.1) · Needs postext ≥ 1.8.0
import { buildDocument, renderPageToCanvas, clearMeasurementCache, registerResourceImage }
  from 'https://esm.sh/postext';

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

// ─── 1 · Design ─────────────────────────────────────────────────────────────
const palette = { ink: '#2b2118', muted: '#76634e', // text; folios and the colophon
  paper: '#f7eddb', card: '#fffdf8', // the cream page; the white recipe card on it
  tomato: '#bf3d29', olive: '#6b7a3a', tint: '#f6e3c1' }; // numbers and tab; dashes; tags
// The hex rides along: design elements read it, not the palette (gotcha: palette-skips-designs).
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
// The engine's defaults link to 'main-color': point it at the tomato, so nothing prints blue.
const colorPalette = Object.entries({ ...palette, 'main-color': palette.tomato })
  .map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } }));
const [TEXT, DISPLAY, HAND] = ['Figtree', 'Young Serif', 'Caveat'];
const PAGE = { w: 190, h: 250, top: 22, inner: 18, outer: 16 }; // mm, mirrored margins
const [BODY, LEAD] = [9.4, 12.8]; // pt: the text of the cards and the notes under them

// #region answer: a white card with a servings tab, two columns inside it
// In the Markdown, :::callout{type="card" label="SERVES 4"} holds a :::columns{count=2} group
// of two nested boxes, :::callout{type="column" title="Ingredients"} and one for the method.
// The group levels its columns by cutting between blocks or lines, so loose lists would run
// the method on under the ingredients. A nested box is one block that never splits, so the
// only cut left is between the two (gotcha: callout-columns).
const TAB = 5.6; // mm: the tab's height, and how far it rises above the card
const card = { id: 'card', background: col('card'),
  padding: { top: mm(4.5), right: mm(6), bottom: mm(5), left: mm(6) },
  // No space of its own above: the tab starts on the first grid line under the opener.
  columnGap: mm(7), marginTop: mm(0),
  // label="…" on the fence prints here: a tab on the top-right corner, a cutlery pictogram
  // beside it and a rule from the far corner that makes the tab part of the card.
  label: { fontFamily: TEXT, fontSize: pt(8), color: col('card'), // bold by default
    background: col('tomato'), height: mm(TAB), offset: mm(TAB), paddingX: mm(2.6),
    icon: { resourceId: 'cutlery', width: mm(TAB * 6 / 8), gap: mm(1.6) }, // as tall as the tab
    rule: { enabled: true, color: col('tomato'), width: pt(1.2) } } };
// The two columns: frameless boxes whose only device is a tracked title.
const NONE = { top: mm(0), right: mm(0), bottom: mm(0), left: mm(0) };
const column = { id: 'column', backgroundEnabled: false, padding: NONE,
  lists: { gap: mm(2.2), itemSpacing: pt(3.5) }, // for the steps as well as the dashes
  titleStyle: { fontFamily: TEXT, fontSize: pt(8), color: col('tomato'), // bold by default
    textTransform: 'uppercase', letterSpacing: pt(1.5), gap: mm(2.4) } };
// config() plugs them in: calloutStyles: [card, column, prep].
// #endregion

// #region prep: a checklist under a header with a strip of three pictograms
// :::callout{type="prep" title="Before you start"}, closed at once, is a header: a box that
// holds only its title and icon. The icon is one picture of three drawings; a width KIT times
// its size makes its box a strip, and the picture is fitted into width × size, left of the
// title. Tasks set inside the box would start after that column, 21 mm in, so the '- [ ]'
// items follow the box, where they print the default task box, '☐'.
const [STRIP, KIT] = [5, 30 / 8]; // mm: the strip's height; the drawing's width over height
const prep = { id: 'prep', backgroundEnabled: false, padding: NONE,
  marginTop: pt(LEAD), marginBottom: column.titleStyle.gap, // the tasks follow at this gap
  icon: { kind: 'resource', resourceId: 'kit', size: mm(STRIP), width: mm(STRIP * KIT),
    align: 'center' }, // the title centred on the strip
  titleStyle: { ...column.titleStyle, color: col('olive') } };
// #endregion

// #region steps: big step numbers in the display face, an olive full stop after each
// Young Serif has old-style figures: 1 and 2 stand 0.56 em, a little above its 0.50 em
// x-height, so 5.1 mm at STEP. A list number is centred 0.3 em (of the text) above the item's
// first baseline, with the canvas 'middle' baseline, which Chrome puts 0.24 em above Young
// Serif's own (gotcha: list-number-centred). DROP centres the figures on the step's first two
// lines, from the cap height of the first to the baseline of the second.
const [STEP, FIGURE, MIDDLE, CAP] = [26, 0.56, 0.24, 0.7]; // pt; em of each face
const DROP = (LEAD - CAP * BODY) / 2 + 0.3 * BODY + (FIGURE / 2 - MIDDLE) * STEP; // pt
const orderedLists = { fontFamily: DISPLAY, fontWeight: 400, // Young Serif ships 400 only
  numberFontSize: pt(STEP), color: col('tomato'),
  separatorColor: col('olive'), separatorGap: pt(0.6), // the default '.' as its own run
  numberVerticalOffset: pt(DROP) };
// #endregion

// #region chips: tags for diet and occasion, as pills in the text
const chipStyles = [{ id: 'tag', fontSize: em(0.86), bold: true, background: col('tint'),
  borderWidth: pt(0), borderRadius: em(1), // no outline; a radius past half the height: a pill
  paddingX: em(0.7), paddingY: em(0.18), gap: em(0.3) }];
// #endregion

// #region opener: the photograph bled across the head, the title and pills set on it
const BAND = 104; // mm: the photo's foot; the pills sit 13 mm above it, the lead 6 mm below
const NOTE = { x: 18, y: 24, w: 70 }; // mm on the page: the box ends 2 mm before the arrow
const at = (x, y, size) => ({ anchor: { to: 'container', edge: 'top-left' },
  offset: { x: mm(x), y: mm(y - PAGE.top) }, size }); // y in mm from the top of the page
const text = (id, content, family, size, placement, extra) => ({ kind: 'text', id, content,
  fontFamily: family, fontSize: pt(size), color: col('ink'), align: 'left',
  overflow: 'wrap', placement, ...extra }); // gotcha: overflow-ellipsis-default
const tracked = { fontWeight: 700, textTransform: 'uppercase', letterSpacing: pt(1.6) };
// Pills are text boxes chained right-of each other; each prints one heading attribute.
const pill = (id, after) => text(id, `{attr.${id}}`, TEXT, 8.4, after ? { anchor:
  { to: `#${after}`, edge: 'right-of' }, offset: { x: mm(1.8) } } : at(0, BAND - 13), {
  fontWeight: 600, box: { backgroundColor: col('card'), borderRadius: mm(3),
    padding: { top: mm(1.1), right: mm(2.8), bottom: mm(1.1), left: mm(2.8) } } });
// One heading style for every recipe; each heading names its photo: art="tortilla".
const opener = { id: 'receta', advancedDesign: { enabled: true, slot: { elements: [
    { kind: 'image', id: 'art', resourceId: '{attr.art}', // filled in per heading, like a text
      placement: { anchor: { to: 'page', edge: 'top-left' },
        size: { width: mm(PAGE.w), height: mm(BAND) } } },
    { kind: 'image', id: 'arrow', resourceId: 'arrow', // the note's arrow, over the photo
      placement: { anchor: { to: 'page', edge: 'top-left' },
        size: { width: mm(PAGE.w), height: mm(BAND) } } },
    text('note', '{attr.note}', HAND, 19, { anchor: { to: 'page', edge: 'top-left' },
      offset: { x: mm(NOTE.x), y: mm(NOTE.y) }, size: { width: mm(NOTE.w) } },
    { fontWeight: 600, align: 'right' }), // on the page, like the arrow and the photo
    pill('time'), pill('level', 'time'), pill('season', 'level'),
    text('title', '{titleText}', DISPLAY, 42, { anchor: { to: '#time', edge: 'above' },
      offset: { y: mm(-3.2) }, size: { width: mm(96) } }, // two lines: the \\ in the heading
    { lineHeight: 1 }), // a multiple, never pt() (gotcha: design-lineheight-multiple)
    text('kicker', '{attr.kicker}', TEXT, 8.2, { anchor: { to: '#title', edge: 'above' },
      offset: { y: mm(-2.4) }, size: { width: mm(96) } }, tracked),
    // The photo reserves no height (gotcha: opener-image-no-reserve); the lead under it does,
    // so the card starts below the lead without a minHeight.
    text('lead', '{attr.lead}', TEXT, 10.5, at(0, BAND + 6, { width: mm(122) }),
      { italic: true, lineHeight: 1.45 }),
  ] } } };
// #endregion

// Folios at the foot of the outer corner: the book on versos, the recipe on rectos.
const foot = (id, content, parity, edge, x, look) => text(id, content, TEXT, 7.6,
  { anchor: { to: 'page', edge }, offset: { x: mm(x), y: mm(-12) } },
  { color: col('muted'), parity, align: edge.endsWith('left') ? 'left' : 'right', ...look });
const folio = { fontFamily: DISPLAY, fontSize: pt(10), color: col('tomato') };
const footer = { elements: [
  foot('verso-folio', '{pageNumber}', 'even', 'bottom-left', PAGE.outer, folio),
  foot('verso-book', '{title}', 'even', 'bottom-left', PAGE.outer + 9, tracked),
  foot('recto-dish', '{chapterTitle}', 'odd', 'bottom-right', -(PAGE.outer + 9), tracked),
  foot('recto-folio', '{pageNumber}', 'odd', 'bottom-right', -PAGE.outer, folio),
] };

const config = () => ({ // a factory, never a shared object (gotcha: config-cache-identity)
  colorPalette, chipStyles, orderedLists, footer, header: { elements: [] },
  page: { width: mm(PAGE.w), height: mm(PAGE.h), dpi: 150, backgroundColor: col('paper'),
    margins: { top: mm(PAGE.top), bottom: mm(20), left: mm(PAGE.inner),
      right: mm(PAGE.outer), mirror: true } }, // left is the inner margin
  layout: { layoutType: 'single' },
  bodyText: { fontFamily: TEXT, fontSize: pt(BODY), lineHeight: pt(LEAD), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
    textAlign: 'left', firstLineIndent: mm(0) }, // ragged and flush: the notes under the cards
  // A designed heading's own text is hidden but still measured: in Young Serif 400, the only
  // weight it ships, not in the default Open Sans 700 that FONTS does not load.
  headings: { fontFamily: DISPLAY, fontWeight: 400, levels: [
    // Restated: any headings object drops the H1 break (gotcha: headings-drop-h1-break).
    // 'any': each recipe opens the next page, whichever side it is on. span: 'page' paints the
    // opener outside the column's clip: kept in the column, the drawing is cut at the top margin.
    { level: 1, span: 'page', breakBefore: { enabled: true, parity: 'any' } },
  ] },
  headingStyles: [opener],
  // Olive dashes for the whole document: an olive lists.color on the column style would turn
  // the step numbers olive too (gotcha: box-list-colour-numbers).
  unorderedLists: { bulletChar: '–', color: col('olive'),
    marginTop: mm(0), // under the checklist's header, the header's marginBottom alone
    marginBottom: pt(LEAD / 2) }, // half a line above the tags
  calloutStyles: [card, column, prep],
  paragraphStyles: [{ id: 'colophon', fontSize: pt(7.4), lineHeight: pt(10),
    color: col('muted'), marginTop: pt(LEAD) }],
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Markdownの見本 · 66行 · content.es.md
title: "Sal y aceite"
---

# Tortilla \\ de patatas {style="receta" art="tortilla" kicker="Huevos y patatas" time="45 min" level="Dificultad media" season="Todo el año" note="¡con cebolla, siempre!" lead="La de casa: patata pochada despacio en mucho aceite de oliva, huevo apenas cuajado y diez minutos de reposo para que la patata se empape. Con cebolla, como la de la abuela; sin ella, si en tu casa se discute."}

:::callout{type="card" label="PARA 4"}
:::columns{count=2}
:::callout{type="column" title="Ingredientes"}
- **6** huevos camperos grandes
- **800 g** de patatas para freír
- **1** cebolla mediana
- **300 ml** de aceite de oliva virgen extra
- Sal fina

:chip[Vegetariana]{style="tag"} :chip[Sin gluten]{style="tag"} :chip[De fiambrera]{style="tag"}

:::callout{type="prep" title="Antes de empezar"}
:::

- [ ] Los huevos, fuera de la nevera
- [ ] Un bol para el huevo y la patata
- [ ] Un plato más ancho que la sartén
:::
:::callout{type="column" title="Elaboración"}
1. Pela las patatas y córtalas en láminas finas; la cebolla, en juliana. Sálalas.
2. Pocha las dos en el aceite, a fuego medio y en una sartén de 24 cm, unos 20 minutos: tiernas y sin dorar.
3. Escúrrelas y guarda el aceite. Bate los huevos con sal, añade la patata aún caliente y deja reposar 10 minutos.
4. Calienta a fuego fuerte una cucharada del aceite, vierte la mezcla y cuájala dos minutos, despegando los bordes.
5. Dale la vuelta con un plato, cuájala un minuto más y sírvela templada.
:::
:::
:::

**Guarda el aceite.** Colado y en un tarro, sirve para freír la próxima tortilla.

# Gazpacho \\ andaluz {style="receta" art="gazpacho" kicker="Sopas frías" time="25 min + 2 h de nevera" level="Fácil" season="De junio a septiembre" note="¡bien frío!" lead="En muchas casas andaluzas se bebe en vaso, recién sacado de la nevera. Pide tomates maduros de verdad y el aceite en hilo con la batidora en marcha, que lo deja cremoso y anaranjado."}

:::callout{type="card" label="PARA 6"}
:::columns{count=2}
:::callout{type="column" title="Ingredientes"}
- **1,5 kg** de tomates de pera maduros
- **1** pimiento verde italiano
- **1** pepino
- **1** diente de ajo
- **100 g** de pan del día anterior, remojado
- **120 ml** de aceite de oliva virgen extra
- **3 cucharadas** de vinagre de Jerez
- Sal y agua fría

:chip[Vegana]{style="tag"} :chip[Sin fuego]{style="tag"} :chip[De víspera]{style="tag"}
:::
:::callout{type="column" title="Elaboración"}
1. Trocea los tomates, el pimiento sin semillas, el pepino pelado y el ajo.
2. Ponlo todo en la batidora con el pan remojado, el vinagre y una cucharadita de sal; deja macerar 15 minutos.
3. Tritura 2 minutos a máxima potencia y, sin parar el motor, añade el aceite en hilo fino hasta que emulsione.
4. Pásalo por un colador fino y aligéralo con agua fría a tu gusto.
5. Rectifica de sal y vinagre y enfríalo al menos 2 horas antes de servirlo.
:::
:::
:::

**Hazlo de víspera.** Aguanta dos días en la nevera, en una jarra tapada; remuévelo antes de servirlo.

:::paragraphs{style="colophon"}
*Sal y aceite* · Compuesto en Young Serif, Figtree y Caveat (SIL OFL) · Recetas originales, CC BY 4.0 · Fotos generadas
:::
`; // content.<lang>.md, inlined by the Cookbook

// #region art: the note's arrow and the pictograms, drawn in the palette's colours
// The dishes are photographs, JPEGs in assets/ cut to the band's 190 × 104 mm. The arrow from
// the handwritten note to the dish and the line pictograms stay vector; the note itself is a
// design element set in Caveat.
const n = (v) => +v.toFixed(2);
const svgDoc = (w, h, body) => `<svg xmlns="http://www.w3.org/2000/svg" width="${w * 10}" `
  + `height="${h * 10}" viewBox="0 0 ${w} ${h}">${body}</svg>`;
const circle = (x, y, r, fill, extra = '') => `<circle cx="${n(x)}" cy="${n(y)}" r="${n(r)}" `
  + `fill="${fill}"${extra}/>`;
const path = (d, fill, extra = '') => `<path d="${d}" fill="${fill}"${extra}/>`;
const stroke = (d, color, width, extra = '') => path(d, 'none', ` stroke="${color}" `
  + `stroke-width="${width}" stroke-linecap="round" stroke-linejoin="round"${extra}`);
const group = (x, y, turn, body) => `<g transform="translate(${n(x)} ${n(y)}) `
  + `rotate(${n(turn)})">${body}</g>`;
// A hand-drawn line and its head, as paths, never a <marker>, in a box as large as the photo:
// it runs from the end of the note, over the plate's rim, to the edge of the dish.
const arrow = svgDoc(PAGE.w, BAND, stroke('M90 29C97 26 102 28 106 33', palette.ink, 0.55)
  + group(106, 33, 62, stroke('M-2.4-1.3L0 0-2.4 1.5', palette.ink, 0.55)));
const cutlery = svgDoc(6, 8, stroke('M1.6 .6V7.4M.6 .6V2.6C.6 3.4 2.6 3.4 2.6 2.6V.6',
  palette.tomato, 0.55) + stroke('M4.6 7.4V.6C5.8 1.4 5.8 3.6 4.6 4.4', palette.tomato, 0.55));
// The kit in line drawings: a bowl with two eggs, the frying pan and the plate that turns the
// tortilla over, in a box KIT times as wide as it is tall.
const egg = (x, turn) => `<ellipse cx="${x}" cy="2.5" rx="1.05" ry="1.35" `
  + `transform="rotate(${turn} ${x} 2.5)" fill="none" stroke="${palette.olive}" `
  + 'stroke-width=".6"/>';
const kit = svgDoc(8 * KIT, 8, egg(3, -12) + egg(5, 14)
  + stroke('M.6 3.9H7.4M1 3.9C1 6.4 2.4 7.4 4 7.4S7 6.4 7 3.9', palette.olive, 0.7)
  + stroke('M9.8 4.4H16.8M10.2 4.4L10.8 6.7C10.9 7.1 11.2 7.3 11.6 7.3H15C15.4 7.3 15.7 7.1 '
    + '15.8 6.7L16.4 4.4', palette.olive, 0.7) + stroke('M16.8 5L20.2 4.1', palette.olive, 1.1)
  + circle(26.2, 4.2, 3.3, 'none', ` stroke="${palette.olive}" stroke-width=".7"`)
  + circle(26.2, 4.2, 2, 'none', ` stroke="${palette.olive}" stroke-width=".5"`));
// #endregion

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
// Every face the design uses. Layout measures with the browser's fonts, so the
// kit loads them from Fontsource before the first build (gotcha: fonts-first).
const FONTS = { Figtree: ['400', '400i', '600', '700'], 'Young Serif': ['400'], Caveat: ['600'] };

// ─── 4 · Build & show ───────────────────────────────────────────────────────
// #region pictures: the photos and the pictograms are resources, cited by id, never by :ref
// The opener's image elements and both icons name a resource id; the resource names the file
// the canvas paints (loadImage or loadSvg registers it). No :ref cites them, so none is numbered.
const photo = (id, altText) => ({ id, typeId: 'figure', kind: 'bitmap', createdAt: 0, updatedAt: 0,
  altText, bitmap: { fileId: `${id}-1520.jpg`, format: 'jpeg', width: 1520, height: 832 } });
const ART = { // markup, width and height in mm, and the alt text
  arrow: [arrow, PAGE.w, BAND, t({ en: 'An arrow to the dish', es: 'Una flecha al plato' })],
  cutlery: [cutlery, 6, 8, t({ en: 'Fork and knife', es: 'Tenedor y cuchillo' })],
  kit: [kit, 8 * KIT, 8, t({ en: 'A bowl with two eggs, a frying pan and a plate',
    es: 'Un bol con dos huevos, una sartén y un plato' })] };
const resources = [
  photo('tortilla', t({ en: 'A potato omelette with a slice pulled out, on a blue-rimmed plate '
    + 'and a red-checked napkin', es: 'Una tortilla de patatas con una porción separada, en un '
    + 'plato de borde azul sobre una servilleta de cuadros rojos' })),
  photo('gazpacho', t({ en: 'A bowl of gazpacho with diced vegetables and a spoon, on a '
    + 'blue-checked napkin beside a tomato', es: 'Un cuenco de gazpacho con dados de verdura '
    + 'y una cuchara, sobre una servilleta de cuadros azules junto a un tomate' })),
  ...Object.entries(ART).map(([id, [, w, h, altText]]) => ({ id, typeId: 'figure',
    kind: 'svg', createdAt: 0, updatedAt: 0, altText, svg: { fileId: `${id}.svg`, width: w * 10,
      height: h * 10 } })), // 10 px a millimetre: the sizes only set the aspect ratio here
];
const photos = resources.filter((r) => r.kind === 'bitmap').map((r) => r.bitmap.fileId);
await Promise.all([...photos.map((file) => loadImage(file, asset(file))),
  ...Object.entries(ART).map(([id, [svg]]) => loadSvg(`${id}.svg`, svg))]);
// #endregion
await loadFonts(FONTS, markdown);
// The excerpt is pages 58 and 59 of the book: 57 pages come before it, so the tortilla opens
// on a verso and the two recipes face each other.
const doc = await buildWithFonts(() => buildDocument({ markdown, resources,
  continuation: { pageIndexOffset: 57, pageNumbering: { startAt: 58 } } }, config()), markdown);
showPages(doc, { title: t({ en: 'Recipe card', es: 'Tarjeta de receta' }) });

キット · core, fonts, viewer, images：全レシピ共通 · 270行
// ─── 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 · images v1 ── recipes with pictures · postext.dev/cookbook ──────────
/** Registers a photo or PNG for the canvas and keeps its bytes for the PDF.
 *  fetch → ImageBitmap never taints the canvas (a plain cross-origin <img> would). */
async function loadImage(fileId, url) {
  const res = await fetch(url);
  if (!res.ok) throw new Error(`Image not found (${res.status}): ${url}`);
  const bytes = new Uint8Array(await res.arrayBuffer());
  registerResourceImage(fileId, await createImageBitmap(new Blob([bytes])));
  (loadImage.bytes ??= new Map()).set(fileId, bytes);
}

/** Registers SVG markup (drawn in code, or fetched) as a vector image. */
async function loadSvg(fileId, svg) {
  const img = new Image();
  img.src = `data:image/svg+xml;charset=utf-8,${encodeURIComponent(svg)}`;
  await img.decode();
  registerResourceImage(fileId, img);
  (loadImage.bytes ??= new Map()).set(fileId, new TextEncoder().encode(svg));
}

/** renderToPdf({ resourceBytes: imageBytes }) */
function imageBytes(fileId) { return loadImage.bytes?.get(fileId); }

/** renderToHtml({ resourceImageUrl: imageUrl }) */
function imageUrl(fileId) {
  const bytes = imageBytes(fileId);
  if (!bytes) return undefined;
  imageUrl.urls ??= new Map();
  if (!imageUrl.urls.has(fileId)) {
    const type = /\.svg$/i.test(fileId) ? 'image/svg+xml' : /\.png$/i.test(fileId) ? 'image/png' : 'image/jpeg';
    imageUrl.urls.set(fileId, URL.createObjectURL(new Blob([bytes], { type })));
  }
  return imageUrl.urls.get(fileId);
}

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