What you'll build

Reciclar en el barrio is a four-page A4 recycling guide from an invented Spanish council, for reading on screen or printing at home. The navy cover shows the five street bins on a yellow kerb. Page 2 holds the contents and three boxes beside a letter from the councillor, and pages 3 and 4 the two sections, in two ragged columns of Atkinson Hyperlegible Next. The pen exports a tagged PDF that passes veraPDF's PDF/UA-1 checks, with headings, lists, boxes and tables in reading order, alt text on the figure and header cells in both tables. The file declares its title and language (es), and its bookmarks and contents rows link to the pages. Tags do not print, so the pen draws them over page 3 of its preview, shown here, each tagged block in a numbered box labelled with its tag. The downloaded PDF has no overlay.

This recipe answers

How do I produce an accessible (tagged, PDF/UA) PDF with alt text and a document language?
How do I get "Figure" and "Table" labels in my document's language?
How do I add a table of contents that updates itself (leaders, page numbers, authors, part rows)?
How do I export a real PDF in the browser with the fonts embedded?

The short answer

script.js · lines 48–71in full code

// renderToPdf writes a tagged PDF by default: the tag tree follows the headings, paragraphs,
// lists and boxes of the Markdown. Pictures and tables carry their own accessible text here.
const table = (id, tsv, columnWidths, caption, altText) => ({ id, typeId: 'table', kind: 'table',
  caption, altText, createdAt: 0, updatedAt: 0, // altText → the Table's /Summary
  placement: { position: 'here' }, // read where cited, not after the page (gotcha: float-read-last)
  table: { model: { headerRowCount: 1, columnWidths, // row 0: TH cells, scope Column
    rows: parseTSV(tsv).rows.map((row) => row.map(({ content }, c) => ({ content: cell(content),
      ...(c === 0 && { isHeader: true }) }))) } } }); // column 0: TH cells, scope Row
const resources = () => [
  { id: 'contenedores', typeId: 'figure', kind: 'svg', placement: { position: 'here' },
    svg: { fileId: 'contenedores.svg', width: FIGURE[0] * PX, height: FIGURE[1] * PX },
    caption: 'Una isla del barrio: de izquierda a derecha, amarillo, azul, verde, marrón y gris.',
    altText: 'Cinco contenedores en fila: amarillo con una botella de plástico, azul con una caja '
      + 'de cartón, verde con una botella de vidrio, marrón con un corazón de manzana y gris con '
      + 'una bolsa de basura cerrada.', createdAt: 0, updatedAt: 0 }, // → the Figure's /Alt
  table('dudas', dudas, [3, 2], 'Los residuos que más dudas dan.',
    'Once residuos y el contenedor de cada uno.'),
  table('horarios', horarios, [2.2, 4, 1.4], 'Días y horas de recogida.',
    'Qué días y desde qué hora se vacía cada contenedor.'),
  { id: 'calle', typeId: 'figure', kind: 'svg', createdAt: 0, updatedAt: 0, // the cover's row:
    svg: { fileId: 'calle.svg', width: STREET[0] * PX, height: STREET[1] * PX } }, // an artifact
];
const exportPdf = (doc) => renderToPdf(doc, { fontProvider: fontsourceProvider,
  resourceBytes: imageBytes }); // accessible and outlines default to true

The alt text and header cells the tags take from the resources

Ingredients

Features: Accessible tagged PDF Table of contents PDF export PDF bookmarks Figure and Table in your language Tables from data Figures exactly here Colour swatches Citations that place figures Document metadata Heading styles Unnumbered chapters Designed openers Full-width chapter band Covers, title pages and colophons Pictures in page designs Callout boxes Fonts before layout Pages on a canvas
Also uses: Heading attributes Numbered headings Leaving the grid on purpose Page and column breaks Paragraph styles Fonts embedded in the PDF Custom resource types Figures and tables as resources Section geometry Running heads per section Line breaks in titles
Type: Atkinson Hyperlegible Next, Atkinson Hyperlegible Mono, Public Sans (SIL OFL 1.1)
Assets: None: every picture is drawn in code
API: buildDocumentclearMeasurementCachedecompressWoff2defaultResourceTypesparseTSVregisterResourceImagerenderPageToCanvasrenderToPdf

Method

#1 · The document's language and title

script.js · lines 127–129in full code

  locale: LANG, // → /Lang es (it hyphenates justified text only: gotcha ragged-no-hyphenation)
  resourceTypes: defaultResourceTypes(LANG), // "Figura", "Tabla" (gotcha: resource-types-locale)
  // /Title and /Author come from the frontmatter, every value quoted (gotcha: quote-frontmatter)

postext-pdf writes the language of the tags from locale, here /Lang es, so a screen reader reads the guide with Spanish pronunciation; without it the file declares en-US. The title and author of the frontmatter in content.es.md become the PDF's title and author, and the file asks viewers to show that title in the window bar instead of the file name. defaultResourceTypes(LANG) gives the captions and the citations their Spanish names: “Figura 1.1”, “tabla 1.1”. The short answer gives the figure and the tables their accessible text: altText becomes the figure's alternate description (/Alt) and each table's /Summary, and the first row and the first column of both tables are tagged as header cells.

#2 · One outline, and a cover band with nothing but the title

script.js · lines 75–105in full code

const [BAND, COVER] = [54, 176]; // mm from the trim top to the foot of each band
const band = (height) => ({ kind: 'box', id: 'band', style: { backgroundColor: col('navy') },
  placement: { ...at('bleed', 'top-left'), size: { width: 'fill', height: mm(height) } } });
const display = (size, hue) => face('Public Sans', 800, size, { lineHeight: 1, color: col(hue) });
const section = { enabled: true, slot: { elements: [band(BAND),
  text('number', '{number}', display(64, 'signal'), at('container', 'top-left', 0, 4)),
  text('title', '{titleText}', display(28, 'paper'),
    { ...at('#number', 'right-of', 6, 3.5), size: { width: mm(130) } })] } };
// A heading design's text is tagged as the heading, so the cover's band holds only the title.
const cover = { enabled: true, minHeight: mm(COVER - TOP + 24), slot: { elements: [band(COVER),
  { kind: 'box', id: 'kerb', style: { backgroundColor: col('signal') },
    placement: { ...at('bleed', 'top-left', 0, COVER), size: { width: 'fill', height: mm(3) } } },
  { kind: 'image', id: 'bins', resourceId: 'calle', // the wheels stand on the kerb
    placement: { ...at('#kerb', 'align-bottom', SIDE), size: { width: mm(STREET[0]) } } },
  text('title', '{titleText}', display(66, 'paper'),
    { ...at('container', 'top-left', 0, 26), size: { width: mm(STREET[0]) } })] } };
const plain = (id, more) => ({ id, numbered: false, span: 'column', ...more,
  advancedDesign: { enabled: false }, fontSize: pt(26), lineHeight: pt(2 * LEAD) });
const headingStyles = [
  { id: 'portada', numbered: false, toc: false, span: 'page', advancedDesign: cover,
    layout: { layoutType: 'single' }, footer: { elements: [] } },
  plain('indice', { toc: false }), // the contents leave their own heading out
  plain('presentacion', { breakBefore: { enabled: false } }), // gotcha: style-inherits-break
];
const headings = { fontFamily: 'Public Sans', fontWeight: 800, color: col('ink'),
  levels: [ // restated: any headings object drops the H1 break (gotcha: headings-drop-h1-break)
    { level: 1, numberingTemplate: '{1}', breakBefore: { enabled: true, parity: 'any' },
      span: 'page', advancedDesign: section, marginBottom: pt(LEAD) }, // 9.7 mm under the band
    { level: 2, fontWeight: 700, fontSize: pt(13.5), lineHeight: pt(LEAD), marginTop: pt(0),
      marginBottom: pt(0) }, // the line above an H2 is the paragraph's, or the resource's, gap
  ] };

The tag tree takes its H1 and H2 elements from the Markdown headings, and the PDF's bookmarks come from the same list, so the cover, the contents, the letter and both sections are level 1 and the crossheads level 2. postext-pdf tags every text element of a heading's design as part of that heading, so the cover's band holds only the title, and the lead and the council's name are set below it as paragraphs. The navy bands, the kerb and the row of bins are design elements, and the PDF marks design boxes and images as artifacts, so they need no alt text and a screen reader skips them.

#3 · Contents that link

script.js · lines 109–114in full code

const [NUMBER, GAP] = [6, 2.5]; // mm: the number column and the gap before a title
const toc = { levels: [{ level: 1, ...face('Public Sans', 700, 12), numberWidth: mm(NUMBER),
  numberGap: mm(GAP), marginTop: pt(LEAD / 2) }, { level: 2, indent: mm(NUMBER + GAP) }],
  unnumbered: { indent: mm(NUMBER + GAP) }, leader: { gap: mm(1.5) }, // Presentación: no number
  // The leaders take this face, not Public Sans (gotcha: toc-leader-kerning)
  pageNumber: { fontFamily: 'Atkinson Hyperlegible Next', fontWeight: 700, width: mm(8) } };

:::toc lists the H1s and H2s with the page labels they print, and in the PDF each of its eleven rows links to the top of its page. The :ref citations “figura 1.1” and “tabla 1.1” on page 3 and “tabla 2.1” on page 4 link to the figure and the tables. The leaders take the page numbers' face, Atkinson Hyperlegible Next Bold, because in Public Sans a run of full stops is spaced wider than the single dot the leader is counted from, and the dots ran into the numbers.

#4 · Reading order, drawn on the page

script.js · lines 301–318in full code

// An opener band's title, each column from top to bottom, then the page's floats. A paragraph
// continued in the next column stays one element, so its second part keeps its number.
const tagOf = (b) => ({ heading: `H${b.headingLevel ?? 1}`, callout: 'Div', listItem: 'LI',
  resource: b.resourceBlock?.kind === 'table' ? 'Table' : 'Figure' })[b.type] ?? 'P';
function readingOrder(page) {
  const ids = new Map(); // element → its number
  const add = (block, box) => {
    const key = block.id.replace(/-cont-\d+$/, ''); // fragments share their block's id
    if (!ids.has(key)) ids.set(key, ids.size + 1);
    return { n: ids.get(key), tag: tagOf(block), box, cont: key !== block.id };
  };
  const blocks = page.columns.flatMap((c) => c.blocks);
  const title = blocks.find((b) => b.hidden && b.type === 'heading'); // drawn by the band
  return [...(page.openerBand && title ? [add(title, union(page.openerBand.blocks
    .filter((b) => b.kind === 'text')))] : []),
  ...blocks.filter((b) => !b.hidden).map((b) => add(b, b.bbox)),
  ...(page.floats ?? []).map((b) => add(b, b.bbox))];
}

A screen reader follows the tags, and renderToPdf tags each page in the order it paints it: the band's title, the first column from top to bottom, the second, then the page's floats. This function replays that order to number the boxes on page 3, and the PDF's structure tree lists the same fourteen elements in the same order. That order is why the figure and both tables sit in the flow, with placement: { position: 'here' } and a ::resource line. Floated to the foot of the first column, figure 1.1 would be tagged after table 1.1, the last block on its page. The paragraph on glass that runs into the second column keeps one number, 9, because the PDF tags both parts as one paragraph.

#5 · Colours picked by contrast ratio

script.js · lines 16–35in full code

const palette = {
  ink: '#14243a', // text: 15.6:1 on white
  navy: '#173556', // bands: white type on it 12.5:1
  signal: '#f2b705', // yellow: only on navy (6.9:1) or as a fill, never as text on white
  tint: '#e8eef5', // header cells and boxes: ink on it 13.4:1
  rule: '#aebccb', // table rules
  muted: '#4a5a6e', // footer and colophon: 7.0:1 on white
  paper: '#ffffff',
};
// hex beside the id: designs read the hex (gotcha: palette-skips-designs)
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
// 'main-color' is the id the engine's default styles link to: any default left in them is navy
const colorPalette = [...Object.entries(palette), ['main-color', palette.navy]]
  .map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } }));
const BIN = { amarillo: '#f2b705', azul: '#1f6fc5', verde: '#2e8b4a', marron: '#8a5a2f',
  gris: '#6b7480' }; // the street bins' colours, for the pictograms and the swatches
const NAME = { amarillo: 'Amarillo', azul: 'Azul', verde: 'Verde', marron: 'Marrón', gris: 'Gris',
  punto: 'Punto limpio' }; // a table cell never shows a colour alone: its name goes beside it
const cell = (text) => (text in NAME // an unknown colour ('none') draws an empty square
  ? `:swatch{color="${BIN[text] ?? 'none'}"} ${NAME[text]}` : text);

PDF/UA-1 does not check colour, but WCAG 2.2 asks for 4.5:1 between text and its background. The ink measures 15.6:1 on white, white type 12.5:1 on the navy bands and the footer's grey 7.0:1. The yellow gives 1.8:1 on white, so it appears only on navy (6.9:1) and as a fill. The pictograms follow WCAG's 3:1 for graphics: white where it reaches that against the bin, ink on the yellow one. cell() writes each container's name beside its swatch, and gives the recycling centre an empty square, so no instruction depends on telling colours apart.

The whole recipe

// ═══ Postext Cookbook · Nº 039 · Accessible tagged PDF (PDF/UA) ═════════════════════
// https://postext.dev/en/cookbook/accessible-tagged-pdf
// Code: MIT · Text: original (CC BY 4.0) · Pictograms: generated in code (CC BY 4.0)
// Fonts: Atkinson Hyperlegible Next and Mono, Public Sans (SIL OFL 1.1) · Needs postext ≥ 1.4.1
import {
  buildDocument, renderPageToCanvas, clearMeasurementCache, registerResourceImage,
  defaultResourceTypes, parseTSV,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'es'; // @lang: the language of the sample document (this recipe is Spanish only)
const RECIPE = 'accessible-tagged-pdf';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: text colours chosen for their contrast, and never a colour without its name
const palette = {
  ink: '#14243a', // text: 15.6:1 on white
  navy: '#173556', // bands: white type on it 12.5:1
  signal: '#f2b705', // yellow: only on navy (6.9:1) or as a fill, never as text on white
  tint: '#e8eef5', // header cells and boxes: ink on it 13.4:1
  rule: '#aebccb', // table rules
  muted: '#4a5a6e', // footer and colophon: 7.0:1 on white
  paper: '#ffffff',
};
// hex beside the id: designs read the hex (gotcha: palette-skips-designs)
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
// 'main-color' is the id the engine's default styles link to: any default left in them is navy
const colorPalette = [...Object.entries(palette), ['main-color', palette.navy]]
  .map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } }));
const BIN = { amarillo: '#f2b705', azul: '#1f6fc5', verde: '#2e8b4a', marron: '#8a5a2f',
  gris: '#6b7480' }; // the street bins' colours, for the pictograms and the swatches
const NAME = { amarillo: 'Amarillo', azul: 'Azul', verde: 'Verde', marron: 'Marrón', gris: 'Gris',
  punto: 'Punto limpio' }; // a table cell never shows a colour alone: its name goes beside it
const cell = (text) => (text in NAME // an unknown colour ('none') draws an empty square
  ? `:swatch{color="${BIN[text] ?? 'none'}"} ${NAME[text]}` : text);
// #endregion

const TRIM = [210, 297]; // A4, the size residents print at home
const [TOP, FOOT, SIDE, LEAD] = [20, 22, 18, 15.5]; // margins in mm, not mirrored; leading in pt
const [PX, FIGURE, STREET] = [12, [83, 30], [174, 44]]; // drawings: px per mm, sizes in mm
const face = (fontFamily, fontWeight, size, more) => ({ fontFamily, fontWeight, fontSize: pt(size),
  ...more });
const at = (to, edge, x = 0, y = 0) => ({ anchor: { to, edge }, offset: { x: mm(x), y: mm(y) } });
const text = (id, content, style, placement) => ({ kind: 'text', id, content, align: 'left',
  overflow: 'wrap', ...style, placement }); // default: '…' (gotcha: overflow-ellipsis-default)

// #region answer: the alt text and header cells the tags take from the resources
// renderToPdf writes a tagged PDF by default: the tag tree follows the headings, paragraphs,
// lists and boxes of the Markdown. Pictures and tables carry their own accessible text here.
const table = (id, tsv, columnWidths, caption, altText) => ({ id, typeId: 'table', kind: 'table',
  caption, altText, createdAt: 0, updatedAt: 0, // altText → the Table's /Summary
  placement: { position: 'here' }, // read where cited, not after the page (gotcha: float-read-last)
  table: { model: { headerRowCount: 1, columnWidths, // row 0: TH cells, scope Column
    rows: parseTSV(tsv).rows.map((row) => row.map(({ content }, c) => ({ content: cell(content),
      ...(c === 0 && { isHeader: true }) }))) } } }); // column 0: TH cells, scope Row
const resources = () => [
  { id: 'contenedores', typeId: 'figure', kind: 'svg', placement: { position: 'here' },
    svg: { fileId: 'contenedores.svg', width: FIGURE[0] * PX, height: FIGURE[1] * PX },
    caption: 'Una isla del barrio: de izquierda a derecha, amarillo, azul, verde, marrón y gris.',
    altText: 'Cinco contenedores en fila: amarillo con una botella de plástico, azul con una caja '
      + 'de cartón, verde con una botella de vidrio, marrón con un corazón de manzana y gris con '
      + 'una bolsa de basura cerrada.', createdAt: 0, updatedAt: 0 }, // → the Figure's /Alt
  table('dudas', dudas, [3, 2], 'Los residuos que más dudas dan.',
    'Once residuos y el contenedor de cada uno.'),
  table('horarios', horarios, [2.2, 4, 1.4], 'Días y horas de recogida.',
    'Qué días y desde qué hora se vacía cada contenedor.'),
  { id: 'calle', typeId: 'figure', kind: 'svg', createdAt: 0, updatedAt: 0, // the cover's row:
    svg: { fileId: 'calle.svg', width: STREET[0] * PX, height: STREET[1] * PX } }, // an artifact
];
const exportPdf = (doc) => renderToPdf(doc, { fontProvider: fontsourceProvider,
  resourceBytes: imageBytes }); // accessible and outlines default to true
// #endregion

// #region headings: one outline: cover and contents unnumbered, then sections 1 and 2 with H2s
const [BAND, COVER] = [54, 176]; // mm from the trim top to the foot of each band
const band = (height) => ({ kind: 'box', id: 'band', style: { backgroundColor: col('navy') },
  placement: { ...at('bleed', 'top-left'), size: { width: 'fill', height: mm(height) } } });
const display = (size, hue) => face('Public Sans', 800, size, { lineHeight: 1, color: col(hue) });
const section = { enabled: true, slot: { elements: [band(BAND),
  text('number', '{number}', display(64, 'signal'), at('container', 'top-left', 0, 4)),
  text('title', '{titleText}', display(28, 'paper'),
    { ...at('#number', 'right-of', 6, 3.5), size: { width: mm(130) } })] } };
// A heading design's text is tagged as the heading, so the cover's band holds only the title.
const cover = { enabled: true, minHeight: mm(COVER - TOP + 24), slot: { elements: [band(COVER),
  { kind: 'box', id: 'kerb', style: { backgroundColor: col('signal') },
    placement: { ...at('bleed', 'top-left', 0, COVER), size: { width: 'fill', height: mm(3) } } },
  { kind: 'image', id: 'bins', resourceId: 'calle', // the wheels stand on the kerb
    placement: { ...at('#kerb', 'align-bottom', SIDE), size: { width: mm(STREET[0]) } } },
  text('title', '{titleText}', display(66, 'paper'),
    { ...at('container', 'top-left', 0, 26), size: { width: mm(STREET[0]) } })] } };
const plain = (id, more) => ({ id, numbered: false, span: 'column', ...more,
  advancedDesign: { enabled: false }, fontSize: pt(26), lineHeight: pt(2 * LEAD) });
const headingStyles = [
  { id: 'portada', numbered: false, toc: false, span: 'page', advancedDesign: cover,
    layout: { layoutType: 'single' }, footer: { elements: [] } },
  plain('indice', { toc: false }), // the contents leave their own heading out
  plain('presentacion', { breakBefore: { enabled: false } }), // gotcha: style-inherits-break
];
const headings = { fontFamily: 'Public Sans', fontWeight: 800, color: col('ink'),
  levels: [ // restated: any headings object drops the H1 break (gotcha: headings-drop-h1-break)
    { level: 1, numberingTemplate: '{1}', breakBefore: { enabled: true, parity: 'any' },
      span: 'page', advancedDesign: section, marginBottom: pt(LEAD) }, // 9.7 mm under the band
    { level: 2, fontWeight: 700, fontSize: pt(13.5), lineHeight: pt(LEAD), marginTop: pt(0),
      marginBottom: pt(0) }, // the line above an H2 is the paragraph's, or the resource's, gap
  ] };
// #endregion

// #region contents: the H1s and H2s with their page numbers; each row links in the PDF
const [NUMBER, GAP] = [6, 2.5]; // mm: the number column and the gap before a title
const toc = { levels: [{ level: 1, ...face('Public Sans', 700, 12), numberWidth: mm(NUMBER),
  numberGap: mm(GAP), marginTop: pt(LEAD / 2) }, { level: 2, indent: mm(NUMBER + GAP) }],
  unnumbered: { indent: mm(NUMBER + GAP) }, leader: { gap: mm(1.5) }, // Presentación: no number
  // The leaders take this face, not Public Sans (gotcha: toc-leader-kerning)
  pageNumber: { fontFamily: 'Atkinson Hyperlegible Next', fontWeight: 700, width: mm(8) } };
// #endregion

const label = (size, color, weight = 400) => face('Atkinson Hyperlegible Mono', weight, size,
  { color: col(color) });
const footer = { elements: [ // the PDF tags these as pagination artifacts
  text('where', '{title} · Castrovalle', { ...label(7.5, 'muted'), letterSpacing: pt(0.6),
    overflow: 'clip' }, at('container', 'bottom-left', 0, -11)),
  text('folio', '{pageNumber}', { ...label(9, 'ink', 700), align: 'right', overflow: 'clip' },
    at('container', 'bottom-right', 0, -10.6))] };

const config = () => ({ // a factory: configs are cached by identity (gotcha: config-cache-identity)
  // #region identity: the language the PDF declares, and captions in that language
  locale: LANG, // → /Lang es (it hyphenates justified text only: gotcha ragged-no-hyphenation)
  resourceTypes: defaultResourceTypes(LANG), // "Figura", "Tabla" (gotcha: resource-types-locale)
  // /Title and /Author come from the frontmatter, every value quoted (gotcha: quote-frontmatter)
  // #endregion
  colorPalette, headings, headingStyles, toc, footer,
  header: { elements: [] }, // each page opens with an H1, so the folio goes in the footer
  page: { width: mm(TRIM[0]), height: mm(TRIM[1]), dpi: 150,
    margins: { top: mm(TOP), bottom: mm(FOOT), left: mm(SIDE), right: mm(SIDE) } },
  layout: { gutterWidth: mm(8) }, // two columns: the default layout
  bodyText: { fontFamily: 'Atkinson Hyperlegible Next', fontSize: pt(10.5), lineHeight: pt(LEAD),
    color: col('ink'), boldColor: col('ink'), italicColor: col('ink'), textAlign: 'left',
    firstLineIndent: mm(0), paragraphSpacing: true }, // ragged, so no runt check: ragged-runts
  unorderedLists: { color: col('ink'), marginTop: pt(0), marginBottom: pt(LEAD) },
  orderedLists: { color: col('ink'), fontWeight: 700, marginTop: pt(0), marginBottom: pt(LEAD) },
  paragraphStyles: [{ id: 'entradilla', fontSize: pt(17), lineHeight: pt(24) },
    { id: 'carta', fontSize: pt(12), lineHeight: pt(18), spaceBetween: pt(9) },
    // the council's imprint drops seven lines below the lead, to the cover's last line
    { id: 'sello', ...label(9, 'ink'), lineHeight: pt(LEAD), marginTop: pt(7 * LEAD) },
    { id: 'colofon', ...label(7, 'muted'), lineHeight: pt(10), marginTop: pt(LEAD) }],
  calloutStyles: [{ id: 'formatos', background: col('tint'), padding: mm(4), snapToGrid: false,
    titleStyle: { ...label(8, 'navy', 700), letterSpacing: pt(0.6), textTransform: 'uppercase' },
    marginTop: mm(4.5), body: { fontSize: pt(10), lineHeight: pt(14.5) } }],
  tableStyle: { rules: 'horizontal', borderColor: col('rule'), borderWidth: pt(0.5),
    headerBackground: col('tint'), headerColor: col('ink'), headerFontSize: pt(9.5),
    bodyFontSize: pt(9.5), cellPadding: mm(1.35) }, // faces and colours follow the body text
  captionStyle: { fontSize: pt(9) },
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Markdown sample · 121 lines · content.es.md
title: "Reciclar en el barrio"
subtitle: "Guía de residuos del barrio de la Estación"
author: "Ayuntamiento de Castrovalle"
---

# Reciclar \\ en el barrio {style="portada"}

:::paragraphs{style="entradilla"}
Dónde va cada residuo del barrio de la Estación, del brik de leche al sofá viejo, y a qué hora pasa cada camión.
:::

:::paragraphs{style="sello"}
**Ayuntamiento de Castrovalle** · Concejalía de Medio Ambiente · Enero de 2026
:::

# Índice {style="indice"}

:::toc

:::callout{type="formatos" title="Cómo usar esta guía"}
La sección 1 recorre la isla de contenedores de izquierda a derecha, y su tabla resuelve los residuos que más dudas dan. La sección 2 trata lo que no va al contenedor: el punto limpio, los horarios de recogida y la retirada de muebles.

Cada cuadrado de color de las tablas lleva al lado el nombre de su contenedor, para que nadie tenga que distinguir los colores.
:::

:::callout{type="formatos" title="Esta guía, en otros formatos"}
Este PDF está etiquetado. Un lector de pantalla recorre sus títulos, listas y tablas en el orden de lectura y lee la descripción de cada figura, y cada fila del índice lleva a su página.

Si la prefieres en letra grande, en lectura fácil o en papel, pídela en el 010 o en la Oficina de Atención a la Ciudadanía. Te la enviamos a casa.
:::

:::callout{type="formatos" title="Datos útiles"}
- **Información municipal:** 010, de lunes a sábado, de 8:00 a 20:00.
- **Punto limpio:** avenida de los Álamos, 14.
- **Muebles y enseres:** cita previa en el 010.
- **Atención a la Ciudadanía:** plaza Mayor, 1.
:::

:::columnbreak

# Presentación {style="presentacion"}

:::paragraphs{style="carta"}
En el barrio de la Estación viven unas 6400 personas, y cada una tira algo más de un kilo de basura al día. Hasta hace un año, casi todo acababa en el mismo sitio. Desde marzo hay contenedor marrón en todas las calles, y con él son cinco los contenedores de cada isla.

Esta guía explica qué va en cada contenedor y qué hacer con lo que no cabe en ninguno: el sofá viejo, el aceite de la sartén, las pilas o una lámpara rota. Los horarios de recogida y la dirección del punto limpio están en la última página.

Lo que se echa al contenedor marrón se convierte en compost en la planta de la comarca y vuelve a los parques y jardines del municipio. Para que ese compost sirva, la materia orgánica tiene que llegar limpia, sin bolsas de plástico ni restos de vidrio.

En la planta de clasificación, un envase echado al contenedor equivocado se aparta a mano. Una bolsa de basura en el contenedor del papel moja y mancha el cartón, y puede echar a perder la carga entera del camión.

Entre marzo y diciembre, el barrio llevó al contenedor marrón 312 toneladas de restos de comida, una de cada siete toneladas de la basura que tiró en esos meses. Este año queremos llegar a una de cada cuatro, y para eso basta con que cada casa separe sus restos de comida.

*Marta Ibarra, concejala de Medio Ambiente*
:::

# Qué va en cada contenedor

En cada calle del barrio hay una isla de cinco contenedores, siempre en el mismo orden, el de la :ref{id="contenedores" style="full" case="lower"}. Cada color recoge un tipo de residuo, pero no todo el plástico va al amarillo ni todo el vidrio al verde.

::resource{id="contenedores"}

## Amarillo: envases

Envases de plástico, latas y briks: botellas de agua y de refresco, botes de champú y de detergente, latas de conserva y de bebida, bolsas de plástico, bandejas de corcho blanco, papel de aluminio, chapas y tapas de metal. Vacíalos antes de tirarlos; no hace falta lavarlos. Un juguete o un cubo no son envases, aunque sean de plástico, y van al contenedor gris.

## Azul: papel y cartón

Periódicos, revistas, folletos, sobres, cajas de cartón y hueveras de cartón. Pliega las cajas antes de echarlas, para que quepan más. Las servilletas y el papel de cocina usados van al marrón, y los tiques de compra, de papel térmico, al gris.

## Verde: vidrio

Botellas, tarros y frascos de vidrio, sin tapas ni tapones: los de metal y plástico van al amarillo, y los de corcho, al marrón. Los vasos, las copas y los platos no son vidrio de envase: funden a otra temperatura y estropean el vidrio que se recicla. Van al gris, y los espejos y los cristales de ventana, al punto limpio.

## Marrón: orgánico

Restos de comida, crudos o cocinados: mondas de fruta, cáscaras de huevo, espinas, posos de café e infusiones, flores secas, tapones de corcho y papel de cocina sucio. Usa bolsas compostables, con la marca de la norma UNE-EN 13432: en la planta, las bolsas de plástico se retiran a mano antes de hacer el compost.

## Gris: resto

Lo que no va en ninguno de los otros cuatro: pañales y compresas, colillas, excrementos de mascotas y arena del gato, polvo de barrer, chicles, cerámica y loza rota. Antes de echar algo al gris, busca en la :ref{id="dudas" style="full" case="lower"} si tiene un sitio mejor, y echa siempre la bolsa cerrada.

::resource{id="dudas"}

# Lo que no va al contenedor

Algunos residuos no caben en ninguna isla, por su tamaño o porque contaminan. Se llevan al punto limpio, se dejan en los puntos de recogida de las tiendas o se recogen a domicilio.

## El punto limpio

Está en la avenida de los Álamos, 14, junto a la rotonda del polígono, y abre de martes a sábado, de 9:00 a 14:00 y de 16:00 a 19:30. Allí se dejan, sin coste para los vecinos:

- aceite de cocina usado, en una botella de plástico cerrada;
- pilas, baterías y bombillas;
- pequeños aparatos eléctricos, como secadores, móviles o cargadores;
- pintura, disolventes y aerosoles con restos;
- espejos, cristales de ventana y radiografías;
- restos de poda, en sacos de hasta 25 kilos.

Las pilas y las bombillas también se pueden dejar en los contenedores de las tiendas que las venden, y los medicamentos, con su caja, en cualquier farmacia. La ropa y el calzado usados tienen sus propios contenedores, en la plaza del Mercado y junto al centro de salud.

## Cuándo pasa cada camión

Los contenedores se vacían de noche, salvo el del vidrio, que se vacía por la mañana. La :ref{id="horarios" style="full" case="lower"} da el día y la hora de cada recogida. Echa las bolsas a partir de las 20:00, para que pasen el menor tiempo posible en la calle, y el vidrio, de día, porque hace ruido.

::resource{id="horarios"}

## Muebles y enseres

Un colchón, una silla o una lavadora no se dejan junto a los contenedores. Si compras un electrodoméstico nuevo, la tienda se lleva el viejo sin cobrarte nada. Lo demás lo retira gratis el servicio municipal, en la puerta de casa:

1. Llama al 010 o pide cita en la sede electrónica del Ayuntamiento.
2. Apunta el día y el número de recogida.
3. Pega en cada objeto un papel con ese número.
4. Esa noche, desde las 21:00, saca los objetos a la acera de tu portal.

Si tienes una duda que esta guía no resuelve, llama al 010, de lunes a sábado de 8:00 a 20:00, o pregunta en el punto limpio. Las preguntas que más se repitan entrarán en la próxima edición.

:::paragraphs{style="colofon"}
Castrovalle es un municipio imaginario, y esta guía se escribió para el Recetario de Postext (postext.dev). Compuesta en Atkinson Hyperlegible Next, Atkinson Hyperlegible Mono y Public Sans (SIL Open Font License). Texto e ilustraciones: CC BY 4.0.
:::
`; // content.<lang>.md, inlined by the Cookbook
const dudas = String.raw`Residuo	Contenedor
Markdown sample · 11 lines · content.dudas.es.md
Brik de leche o de zumo	amarillo
Tapa de un tarro de cristal	amarillo
Papel de aluminio	amarillo
Bolsa de patatas fritas	amarillo
Caja de pizza	azul
Frasco de colonia	verde
Servilleta de papel usada	marron
Vaso o copa de cristal	gris
Tique de compra	gris
Bombilla	punto
Aceite de cocina usado	punto
`; // TSV, as a spreadsheet exports it: residuo, contenedor
const horarios = String.raw`Contenedor	Días	Desde
Markdown sample · 5 lines · content.horarios.es.md
amarillo	Lunes, miércoles y viernes	22:00
azul	Martes y sábados	22:00
verde	Jueves alternos	8:00
marron	Todos los días	23:00
gris	Todos los días	23:00
`; // TSV: contenedor, días, desde qué hora

// #region reading-order: the order of the tags, which is the order renderToPdf paints the page in
// An opener band's title, each column from top to bottom, then the page's floats. A paragraph
// continued in the next column stays one element, so its second part keeps its number.
const tagOf = (b) => ({ heading: `H${b.headingLevel ?? 1}`, callout: 'Div', listItem: 'LI',
  resource: b.resourceBlock?.kind === 'table' ? 'Table' : 'Figure' })[b.type] ?? 'P';
function readingOrder(page) {
  const ids = new Map(); // element → its number
  const add = (block, box) => {
    const key = block.id.replace(/-cont-\d+$/, ''); // fragments share their block's id
    if (!ids.has(key)) ids.set(key, ids.size + 1);
    return { n: ids.get(key), tag: tagOf(block), box, cont: key !== block.id };
  };
  const blocks = page.columns.flatMap((c) => c.blocks);
  const title = blocks.find((b) => b.hidden && b.type === 'heading'); // drawn by the band
  return [...(page.openerBand && title ? [add(title, union(page.openerBand.blocks
    .filter((b) => b.kind === 'text')))] : []),
  ...blocks.filter((b) => !b.hidden).map((b) => add(b, b.bbox)),
  ...(page.floats ?? []).map((b) => add(b, b.bbox))];
}
// #endregion

// #region art: the five street bins, and the reading order painted over page 3
const n = (v) => Math.round(v * 100) / 100;
const rgb = (hex) => hex.slice(1).match(/../g).map((c) => parseInt(c, 16));
const shade = (hex, k) => `#${rgb(hex).map((c) => Math.round(c * k).toString(16).padStart(2, '0'))
  .join('')}`;
const luminance = (hex) => rgb(hex).map((c) => c / 255).map((c) => (c <= 0.03928 ? c / 12.92
  : ((c + 0.055) / 1.055) ** 2.4)).reduce((sum, c, i) => sum + c * [0.2126, 0.7152, 0.0722][i], 0);
// A white glyph where it reaches 3:1 against the bin (WCAG's figure for graphics), else ink.
const glyphOn = (hex) => (1.05 / (luminance(hex) + 0.05) >= 3 ? '#ffffff' : palette.ink);
// Pictograms in an 8 × 10 box centred on (0, 0): a bottle, a box, a wine bottle, an apple core
// and a tied bag. Strokes only, so they stay vector in the PDF.
const GLYPH = {
  amarillo: 'M-1.2 -5L1.2 -5L1.2 -3.6C2.8 -3 3 -2 3 -1L3 4.2C3 4.8 2.6 5 2 5L-2 5C-2.6 5 -3 4.8 '
    + '-3 4.2L-3 -1C-3 -2 -2.8 -3 -1.2 -3.6Z M-3 0.6L3 0.6',
  azul: 'M-4 -1L0 -3L4 -1L4 4L0 5.6L-4 4Z M-4 -1L0 1L4 -1 M0 1L0 5.6 M-4 -1L-5 -3.4L-1 -5.4L0 -3',
  verde: 'M-0.9 -5.4L0.9 -5.4L0.9 -2.2C2.6 -1.4 2.8 -0.4 2.8 0.8L2.8 4.6C2.8 5.1 2.5 5.4 2 5.4L-2 '
    + '5.4C-2.5 5.4 -2.8 5.1 -2.8 4.6L-2.8 0.8C-2.8 -0.4 -2.6 -1.4 -0.9 -2.2Z',
  marron: 'M-2.6 -3.2C-0.6 -3.8 0.6 -3.8 2.6 -3.2C1.2 -1.6 1.2 1.6 2.6 3.6C0.6 4.4 -0.6 4.4 '
    + '-2.6 3.6C-1.2 1.6 -1.2 -1.6 -2.6 -3.2Z M0 -3.6L0.4 -5.6 M0.4 -5C1.6 -6 2.8 -5.6 3.2 -5',
  gris: 'M-3.4 -1.6C-3.8 1.4 -3.4 5 0 5C3.4 5 3.8 1.4 3.4 -1.6C2.6 -2.6 1 -3 0 -3.2C-1 -3 '
    + '-2.6 -2.6 -3.4 -1.6Z M-1.6 -3.1L-2.4 -5.2L0 -4L2.4 -5.2L1.6 -3.1',
};
function binsSvg([w, h], size) { // five bins across w mm, their wheels on the foot of the drawing
  const step = w / 5;
  const bins = Object.keys(BIN).map((id, i) => {
    const [cx, bw, r] = [step * (i + 0.5), size * 0.68, size * 0.06]; // centre, width, wheel
    const [top, foot] = [h - size - r, h - r];
    const lid = `M${n(cx - bw / 2 - r / 2)} ${n(top)}L${n(cx + bw / 2 + r / 2)} ${n(top)}`
      + `L${n(cx + bw / 2)} ${n(top - size * 0.1)}L${n(cx - bw / 2)} ${n(top - size * 0.1)}Z`;
    const body = `M${n(cx - bw / 2)} ${n(top)}L${n(cx + bw / 2)} ${n(top)}L${n(cx + bw * 0.46)} `
      + `${n(foot)}L${n(cx - bw * 0.46)} ${n(foot)}Z`;
    const wheel = (x) => `<circle cx="${n(x)}" cy="${n(foot)}" r="${n(r)}" fill="${palette.ink}"/>`;
    return `<path d="${body}" fill="${BIN[id]}"/><path d="${lid}" fill="${shade(BIN[id], 0.72)}"/>`
      + wheel(cx - bw * 0.34) + wheel(cx + bw * 0.34)
      + `<path d="${GLYPH[id]}" transform="translate(${n(cx)} ${n(top + size * 0.48)}) `
      + `scale(${n(size / 16)})" fill="none" stroke="${glyphOn(BIN[id])}" stroke-width="0.8" `
      + 'stroke-linejoin="round" stroke-linecap="round"/>'; // the glyphs are drawn for a 16 mm bin
  });
  return `<svg xmlns="http://www.w3.org/2000/svg" width="${w * PX}" height="${h * PX}" `
    + `viewBox="0 0 ${w} ${h}">${bins.join('')}</svg>`;
}
function union(boxes) { // the box around several design elements
  return boxes.reduce((u, { bbox: b }) => {
    const [x, y] = [Math.min(u.x, b.x), Math.min(u.y, b.y)];
    return { x, y, width: Math.max(u.x + u.width, b.x + b.width) - x,
      height: Math.max(u.y + u.height, b.y + b.height) - y };
  }, boxes[0].bbox);
}
function drawReadingOrder(ctx, page, scale) {
  const mmPx = (v) => (v * page.width * scale) / TRIM[0];
  const [r, pad, ink] = [mmPx(2.8), mmPx(1.2), '#d6146e']; // disc radius, box padding, magenta
  const inset = mmPx(0.6); // a gap under a box another one touches, such as a heading
  const boxOf = ({ x, y, width, height }, grow = 0) => ({ x: x * scale - pad, y: y * scale
    + inset - grow, w: width * scale + 2 * pad, h: height * scale - inset + 2 * grow });
  const tab = (label, { x, y, w }, fill) => { // a label straddling the box's top-right corner
    ctx.font = `700 ${r * 0.95}px "Atkinson Hyperlegible Mono"`;
    const lw = ctx.measureText(label).width + r * 0.8;
    ctx.fillStyle = fill;
    ctx.fillRect(x + w - lw, y - r * 0.55, lw, r * 1.1);
    ctx.fillStyle = '#ffffff';
    ctx.fillText(label, x + w - lw / 2, y + r * 0.02);
  };
  const marks = readingOrder(page).map((m) => ({ ...m, ...boxOf(m.box) }));
  ctx.save();
  ctx.textAlign = 'center';
  ctx.textBaseline = 'middle';
  ctx.lineWidth = r / 4.5;
  ctx.strokeStyle = ink;
  marks.forEach((m, i) => { // a line down each column, from one number to the next
    const p = marks[i - 1];
    if (!p || m.y < p.y) return; // no line for the jump to the next column
    ctx.beginPath();
    ctx.moveTo(p.x - r * 1.3, p.y + r);
    ctx.lineTo(m.x - r * 1.3, m.y + r);
    ctx.stroke();
  });
  for (const m of marks) {
    ctx.fillStyle = 'rgba(214, 20, 110, 0.07)';
    ctx.fillRect(m.x, m.y, m.w, m.h);
    ctx.setLineDash(m.cont ? [r / 2, r / 3] : []);
    ctx.strokeRect(m.x, m.y, m.w, m.h);
    ctx.setLineDash([]);
    ctx.fillStyle = ink;
    ctx.beginPath();
    ctx.arc(m.x - r * 1.3, m.y + r, r, 0, Math.PI * 2);
    ctx.fill();
    tab(m.cont ? `${m.tag} (cont.)` : m.tag, m, ink);
    ctx.font = `700 ${r * 1.15}px "Atkinson Hyperlegible Mono"`;
    ctx.fillText(String(m.n), m.x - r * 1.3, m.y + r * 1.05);
  }
  if (page.footer?.blocks.length) { // running heads and folios: artifacts, never read
    const foot = boxOf(union(page.footer.blocks), pad);
    ctx.strokeStyle = '#6b7480';
    ctx.setLineDash([r / 2, r / 3]);
    ctx.strokeRect(foot.x, foot.y, foot.w, foot.h);
    tab('Artifact', foot, '#6b7480');
  }
  ctx.restore();
}
function showReadingOrder(page) { // over the viewer's page, and in the Cookbook's page images
  const canvas = [...document.querySelectorAll('#pages canvas')]
    .find((c) => c.postext.page === page);
  const layer = Object.assign(document.createElement('canvas'), { width: canvas.clientWidth * 2,
    height: canvas.clientHeight * 2 }); // transparent, over the painted page
  layer.style.cssText = 'position:absolute;top:0;left:0;width:100%;background:none;box-shadow:none';
  canvas.parentElement.style.position = 'relative';
  canvas.after(layer);
  drawReadingOrder(layer.getContext('2d'), page, layer.width / page.width);
  window.__postextOverlay = (ctx, p, _, scale) => p.index === page.index
    && drawReadingOrder(ctx, p, scale);
}
// #endregion

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
// Loaded before layout (gotcha: fonts-first); the PDF embeds the same files (gotcha: latin-subset)
const FONTS = { 'Atkinson Hyperlegible Next': ['400', '400i', '700', '700i'],
  'Atkinson Hyperlegible Mono': ['400', '700'], 'Public Sans': ['700', '800'] };

// ─── 4 · Build & show ───────────────────────────────────────────────────────
await loadFonts(FONTS, markdown);
await loadSvg('contenedores.svg', binsSvg(FIGURE, 23));
await loadSvg('calle.svg', binsSvg(STREET, 36));
const content = { markdown, resources: resources() };
const doc = await buildWithFonts(() => buildDocument(content, config()), markdown);
showPages(doc, { title: 'Reciclar en el barrio · PDF accesible' });
showReadingOrder(doc.pages[2]); // page 3: every tagged block numbered in reading order
offerPdf(() => exportPdf(doc), `${RECIPE}.pdf`);

Kit · core, fonts, viewer, pdf, images: the same in every recipe · 310 lines
// ─── Kit ── helpers shared by every Cookbook recipe · postext.dev/cookbook ─────

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

// ─── Kit · 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 ───────────────────────────────────────────────────────────────────────

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

Variations

#Let the figure float

Drop the placement and figure 1.1 floats to the foot of page 3's first column, and the PDF tags it after table 1.1, the last block on the page.

-  { id: 'contenedores', typeId: 'figure', kind: 'svg', placement: { position: 'here' },
+  { id: 'contenedores', typeId: 'figure', kind: 'svg',

Pitfalls

Pitfall

A floated figure is read after the text of its page

renderToPdf tags a page in the order it paints it: an opener band's title, each column from top to bottom, then the page's floats. A figure or table that floats to the head of a column is therefore read after the last paragraph and the last table of its page, away from the sentence that cites it. Set the ones a reader must meet where they are cited inline, with placement 'here' and a ::resource line. Accessible tagged PDF →

Pitfall

Contents leaders overrun in a face that kerns full stops

postext 1.4.1 counts a leader's dots from the width of one dot and sets them in the page numbers' face. Some faces space a run of full stops wider than that (Public Sans Bold at 12 pt: 6.7 px for one dot at 150 dpi, 7.6 px for each dot of a run), so the dots overrun their room, touch the page number and stop lining up from row to row. Give toc.pageNumber a fontFamily whose full stops keep their width in a run, such as the body face. Table of contents →

Pitfall

Ragged text is never checked for runts

optimalLineBreaking, avoidRunts, runtPenalty and runtMinCharacters act on the Knuth–Plass line breaker, which postext 1.4.1 runs for justified text only. A ragged paragraph is broken line by line and can end on one short word whatever those settings say. Read the last lines of ragged text and reword a paragraph that ends on a runt. Widows, orphans and runts →

Pitfall

Quote every frontmatter value

YAML reads title: 1984 as a number and a date as a Date object, and non-string values print empty in placeholders and leave the PDF without a title. Quote every value: title: "1984". Document metadata →

Pitfall

Localise Figure/Table with defaultResourceTypes(locale)

The config's locale sets hyphenation, not captions: without resourceTypes the built-in types say Figure and Table in English. Pass resourceTypes: defaultResourceTypes('es') for Spanish; for any other language, write the names yourself in resourceTypes. Figure and Table in your language →

Pitfall

Ragged text is never hyphenated

Hyphenation applies to justified text only; ragged-right text breaks between words, so a narrow ragged column gets a deep rag. Justify the passage or widen the measure. Hyphenation and document language →

Pitfall

An unknown :ref id prints '?' with no engine warning

A :ref to an id no resource has prints "?" and places nothing, and only the Sandbox warns about it. Check that every cited id exists. Citations that place figures →

Pitfall

Any headings object switches off the H1 page break

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

Pitfall

A heading style inherits its level's page break

A headingStyles entry takes every field it leaves out from its heading level, breakBefore included. A contents page or a colophon styled on an H1 after a :::pagebreak inherits parity 'odd' and lands behind a blank page. Give such a style breakBefore: { enabled: false }. Heading styles →

Pitfall

A swapped palette misses design elements and the reference colour

postext 1.4.1 reads colorPalette into the text styles (body, headings, lists, captions, tables, boxes) but not into the elements of headers, footers, openers and part pages, nor into bodyText.referenceColor: they keep the hex written beside their paletteId. When you swap the palette, for a dark screen edition or a retint, rewrite every linked colour from colorPalette before the build. Semantic colour palette →

Pitfall

Design text overflow defaults to 'ellipsis-end'

A design text element that does not fit its width ends in an ellipsis by default. Set overflow: 'wrap' for titles that should break onto more lines. Text, rules and boxes in page designs →

Pitfall

A config is cached by identity: build a fresh object

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

Pitfall

Load every face before layout

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

Pitfall

Fontsource latin files drop glyphs outside Latin

The PDF provider embeds Fontsource's latin files, which cover Spanish and Western European text but not →, ≈, ✓, ★, Greek or Central European letters; those glyphs go missing in the PDF. Keep PDF text inside the latin range. Fonts embedded in the PDF →

The pen cannot validate its own PDF, because veraPDF runs outside the browser. Download the file and run verapdf -f ua1 accessible-tagged-pdf.pdf; the copy captured for this page passes. The checker cannot tell whether an alt text describes its picture, so listen to the guide with a screen reader as well.

In postext 1.4.1 a Markdown link prints its words and adds no link to the PDF; only :ref citations and contents rows link. The colophon prints the web address in full.

Credits

Recipe: Ignacio Ferro
Text: Original prose, CC BY 4.0
Fonts: Atkinson Hyperlegible Next (SIL OFL 1.1) · Atkinson Hyperlegible Mono (SIL OFL 1.1) · Public Sans (SIL OFL 1.1)
Code: MIT, like Postext

Edit this write-up ↗Recipe folder on GitHub ↗

#What you'll build

#The short answer

#Ingredients

#Method

#1 · The document's language and title

#2 · One outline, and a cover band with nothing but the title

#3 · Contents that link

#4 · Reading order, drawn on the page

#5 · Colours picked by contrast ratio

#The whole recipe

#Variations

#Let the figure float

#Pitfalls

#Credits

More from the Cookbook

Print-ready PDF: bleed, crop marks and CMYK

A real PDF with the same fonts embedded

Front matter in roman folios, then page 1

What you'll build

The short answer

Ingredients

Method

The whole recipe

Variations

Pitfalls

Credits