Poemas con forma: Alas de Pascua, con cada verso centrado

// ═══ Postext Cookbook · Nº 062 · Shaped verse: Herbert's Easter Wings, centred line by line ═
// https://postext.dev/en/cookbook/shaped-verse
// Code: MIT · Text: G. Herbert, The Temple, 1633 (PD; EEBO-TCP, CC0) · Spanish version: CC BY 4.0
// Fonts: IM Fell English, Great Primer and English SC (SIL OFL 1.1) · Needs postext ≥ 1.4.1
import { buildDocument, renderPageToCanvas, clearMeasurementCache } from 'https://esm.sh/postext';

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

// ─── 1 · Design ─────────────────────────────────────────────────────────────
const palette = { // every colour in the config links to one of these
  ink: '#241d29', // the text: a violet-black
  violet: '#5c2a6f', // the one accent: the titles and the small-capital labels
  paper: '#fbf7ee', // the sheet: an uncoated cream
};
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = [
  ...Object.entries(palette).map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } })),
  // Italic and bold take their colour from 'main-color' unless set. With 'main-color' in ink,
  // the italic subtitle, epigraph and motto print in ink instead of the default blue.
  { id: 'main-color', name: 'ink (defaults)', value: { hex: palette.ink, model: 'hex' } },
];
const LEAD = 17; // pt: the leading of every line, verse and prose alike

// #region answer: centred text, one line of verse to a paragraph
// Postext joins the lines of a Markdown paragraph, so every line of the poem is a paragraph
// of its own, with a blank line after it. Centred, each line keeps its natural width on the
// axis of the measure, and the lengths Herbert gave his lines draw the figure:
//   Lord, who createdst man in wealth and store,
//
//   Though foolishly he lost the same,
//
//   Decaying more and more,
const verse = {
  fontFamily: 'IM Fell English', fontSize: pt(12.4), lineHeight: pt(LEAD), color: col('ink'),
  textAlign: 'center', // ragged on both sides; 1.4.1 hyphenates justified text only
  firstLineIndent: pt(0), // the default 1.5 em moves every line 3.3 mm off the titles' axis
};
// #endregion

// #region measure: an A5 leaf whose measure holds the longest line whole
// A line too long for the measure wraps, and both halves are centred, which adds a step to
// the outline.
// The widest line, 'Lord, who createdst man in wealth and store,', is 80.7 mm in 12.4 pt
// Fell, so the 110 mm measure takes every line of both poems whole.
const TRIM = { w: 148, h: 210 }; // mm: A5, one A4 sheet folded once
const MARGIN = { top: 22, bottom: 24, inner: 17, outer: 21 }; // mm: the measure is 110 mm
// #endregion

// #region titles: plain headings, centred, in the display face and the accent
// headings.textAlign centres every level. The Fell faces ship weight 400 only, so no level
// asks for bold.
const titles = {
  fontFamily: 'IM Fell Great Primer', fontWeight: 400, color: col('violet'), textAlign: 'center',
  levels: [
    // The keepsake's title opens page 1, where a break changes nothing. It is restated because
    // any headings object drops it, and a second # title would then run on
    // (gotcha: headings-drop-h1-break).
    { level: 1, fontSize: pt(40), lineHeight: pt(LEAD * 3), textTransform: 'uppercase',
      marginBottom: pt(LEAD), breakBefore: { enabled: true, parity: 'odd' } },
    // A poem opens the next page, recto or verso: The Altar (page 2) faces Easter Wings.
    // 1.4.1 drops the top margin of a heading that opens a page, so the title is lowered by
    // its line box instead: three lines deep, it sets the title about 5 mm down. The default
    // half-em margin under it rounds up to a whole line, and each poem starts on line 5.
    { level: 2, fontSize: pt(24), lineHeight: pt(LEAD * 3), textTransform: 'uppercase',
      breakBefore: { enabled: true, parity: 'any' } },
    // The small-capital labels on pages 1 and 4: the sister face at the body size, with no
    // margins, since the :::space lines place them.
    { level: 3, fontFamily: 'IM Fell English SC', fontSize: pt(12.4), lineHeight: pt(LEAD),
      marginTop: pt(0), marginBottom: pt(0) },
  ],
};
// #endregion

// #region pages: four pages, spaced and broken from the Markdown
// A blank line adds no space, so every gap on these pages is a :::space{lines=N}, which adds
// N lines of the 17 pt grid (one without the attribute). ## opens a page for each poem, and
// :::pagebreak opens the last page.
const config = () => ({ // a factory: the engine caches resolved configs per object
  colorPalette,
  page: { // mirror: left is the inner margin; 150 dpi is for the screen
    sizePreset: 'custom', width: mm(TRIM.w), height: mm(TRIM.h), dpi: 150,
    backgroundColor: col('paper'),
    margins: { top: mm(MARGIN.top), bottom: mm(MARGIN.bottom), left: mm(MARGIN.inner),
      right: mm(MARGIN.outer), mirror: true },
  },
  layout: { layoutType: 'single' }, // the default is two columns
  // 1.4.1 does not link referenceColor to main-color (gotcha: palette-skips-designs), so a
  // :ref added to these pages would print in the default blue.
  bodyText: { ...verse, referenceColor: col('ink') },
  headings: titles,
  header: { elements: [] }, // a folded keepsake of four pages: no running heads,
  footer: { elements: [] }, // and no folios
});
// #endregion

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Muestra en Markdown · 131 líneas · content.es.md
title: "El templo"
author: "George Herbert"
---

# El templo

*Poemas sagrados y jaculatorias privadas*

:::space

de George Herbert

:::space{lines=5}

### Salmo 29

*Y en su templo todos los suyos le dicen gloria.*

:::space{lines=10}

### Dos poemas con forma

según la primera edición, Cambridge, 1633,

en versión castellana

## El altar

Un ALTAR roto, Señor, te alza tu siervo,

hecho de un corazón y unido con lágrimas:

sus piezas son como tu mano las hizo;

no lo tocó la herramienta de un cantero.

Solo un CORAZÓN

es una piedra tal

que nada salvo

tu poder la talla.

Por eso cada parte

de mi duro pecho

se une en este marco

y alaba tu nombre,

para que, si llego a guardar silencio,

no cesen estas piedras de alabarte.

Oh, sea mío tu bendito SACRIFICIO,

y santifica este ALTAR, que sea tuyo.

## Alas de Pascua

Señor, que creaste al hombre rico y colmado,

aunque él, necio, lo perdió todo,

decayendo cada vez más

hasta volverse

pobrísimo:

junto a ti

déjame alzarme

como alondras, en armonía,

y cantar este día tus victorias:

entonces la caída impulsará en mí el vuelo.

:::space

Mi tierna edad comenzó en el dolor:

y sin tregua, con males y vergüenza,

castigaste tanto el pecado

que me volví

flaquísimo.

Junto a ti

déjame unirme,

y sentir este día tu victoria:

pues si injerto mi ala en la tuya,

la aflicción hará avanzar en mí el vuelo.

:::pagebreak

### El lema de Herbert

*Menos que la menor de las misericordias de Dios.*

:::space

Con él, escribieron sus impresores, cerraba cuanto pudiera redundar en su propia honra.

:::space{lines=7}

### Nota sobre el texto

Las versiones siguen la edición príncipe (Cambridge, 1633). Allí «The Altar» se lee derecho en la página 18, mientras que «Easter Wings» va de lado en las páginas 34 y 35, una estrofa en cada una. Aquí van derechas; si giras el cuadernillo un cuarto de vuelta, cada estrofa se abre en dos alas. Cada verso castellano mide casi lo que el original, pero pierde la rima.

:::space{lines=3}

Compuesto en IM Fell English, English SC y Great Primer,

recreaciones de Igino Marini de los tipos

que John Fell reunió en Oxford.

Texto inglés de EEBO-TCP;

salmo de la Reina-Valera.
`; // content.<lang>.md, inlined by the Cookbook

// ─── 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 = {
  'IM Fell English': ['400', '400i'],
  'IM Fell Great Primer': ['400'],
  'IM Fell English SC': ['400'],
};

// ─── 4 · Build & show ───────────────────────────────────────────────────────
await loadFonts(FONTS, markdown);
const doc = await buildWithFonts(() => buildDocument({ markdown }, config()), markdown);
showPages(doc, { title: t({ en: 'Easter Wings and The Altar', es: 'Alas de Pascua y El altar' }) });

Kit · core, fonts, viewer: igual en todas las recetas · 235 líneas
// ─── 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 ───────────────────────────────────────────────────────────────────────