社区简报：头条与简讯

// ═══ Postext Cookbook · Nº 042 · Community newsletter: lead story and briefs ═════
// https://postext.dev/en/cookbook/community-newsletter
// Code: MIT · Text: original (CC BY 4.0) · Drawings: generated in code (CC BY 4.0)
// Fonts: Work Sans, Titan One, Courier Prime (SIL OFL 1.1) · Needs postext ≥ 1.4.1
import {
  buildDocument, renderPageToCanvas, clearMeasurementCache, registerResourceImage,
} from 'https://esm.sh/postext';

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

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: garden colours, every one linked by id
// ink: text · leaf: nameplate and headlines · tomato, the accent: tags, tab, column heads ·
// straw: the band · marigold: second tag · tint: the box · rule: hairlines · muted: notes
const palette = { ink: '#1d211c', leaf: '#2f6b3a', tomato: '#c43f2a', straw: '#f2d492',
  marigold: '#e2b33c', tint: '#eef4e8', rule: '#cfd3c6', muted: '#5f6659', paper: '#fbfaf5' };
// The hex rides along: 1.4.1 designs read it, not the link (gotcha: palette-skips-designs).
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = [ // defaults link to 'main-color': point it at the leaf, never blue
  ...Object.entries(palette).map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } })),
  { id: 'main-color', name: 'leaf (defaults)', value: { hex: palette.leaf, model: 'hex' } },
];
// #endregion
const [TEXT, DISPLAY, LABEL] = ['Work Sans', 'Titan One', 'Courier Prime'];
const SIDE = 16; // mm: the side margins of one A4 sheet, printed on both sides
const LEAD = 13.4; // body leading in pt: the baseline grid
const caps = (size, colour) => ({ fontFamily: LABEL, fontSize: pt(size), fontWeight: 700,
  textTransform: 'uppercase', letterSpacing: pt(size * 0.12), color: col(colour) });
const at = (to, edge, x = 0, y = 0) => ({ anchor: { to, edge }, offset: { x: mm(x), y: mm(y) } });

// #region answer: a wide column for the lead, a narrow one for the briefs, one flow
const layout = {
  layoutType: 'oneAndHalf', // the narrow column sits on the right and takes text (the
  // defaults of sideColumnSide and sideColumnRole; 'floats' would keep text out of it)
  sideColumnPercent: 32, // 57 mm of the 178 mm measure
  gutterWidth: mm(8), // the wide column keeps the other 113 mm
  columnRule: { enabled: true, color: col('rule') }, // a 0.5 pt hairline in the gutter
};
// The text runs down the wide column, then the narrow one, then the next page's wide
// column. A :::columnbreak sends the next block on to the following column, so the
// Markdown decides what each column holds:
//   ## Shared compost bays open by the top gate      ← the lead, in the wide column
//   … :chip[Continued on page 2]{style="jump"}
//   :::columnbreak                                    ← the briefs open the narrow column
//   ## In brief {style="rail"}
//   …
//   :::columnbreak                                    ← from the last column: next page
//   :chip[Continued from page 1]{style="jump"}        ← the lead goes on in the wide column
// Fit the copy so that each column ends on a whole paragraph: in 1.4.1 a paragraph that
// runs over into the other column keeps the measure it started with (gotcha:
// split-paragraph-measure).
// #endregion

// #region masthead: the H1 is the nameplate; the issue tab reads the frontmatter
const BEARING = 0.6; // mm: Titan One's left side bearing at 60 pt (T 0.42, G 0.63, L/H 0.85)
const DRILL = { id: 'drill', typeId: 'drawing', kind: 'svg', createdAt: 0, updatedAt: 0,
  svg: { fileId: 'drill.svg', width: 2100, height: 80 } }; // drawn by the design, not the text
const masthead = { enabled: true,
  minHeight: pt(10 * LEAD), // ten grid lines: the text starts one line clear of the band
  slot: { elements: [
    // The band, 62 mm deep, covers the column rule, which 1.4.1 starts at the top of the text
    // area on this page, behind the masthead, however deep the masthead is.
    { kind: 'box', id: 'band', style: { backgroundColor: col('straw') },
      placement: { ...at('page', 'top-left'), size: { width: mm(210), height: mm(62) } } },
    { kind: 'image', id: 'drill', resourceId: 'drill', // seedlings along the band's foot
      placement: { ...at('page', 'top-left', 0, 54), size: { width: mm(210), height: mm(8) } } },
    { kind: 'text', id: 'society', content: '{subtitle}', ...caps(8, 'leaf'), align: 'left',
      placement: { ...at('page', 'top-left', SIDE, 12), size: { width: mm(150) } } },
    { kind: 'text', id: 'title', content: '{titleText}', fontFamily: DISPLAY, fontSize: pt(60),
      lineHeight: 0.9, // a multiple of the size (gotcha: design-lineheight-multiple)
      color: col('leaf'), align: 'left', overflow: 'wrap', // two lines in 178 mm
      placement: { ...at('page', 'top-left', SIDE - BEARING, 17), size: { width: mm(178) } } },
    // {attr.issue} comes from the H1 line, {publishDate} from the quoted frontmatter
    // (gotcha: quote-frontmatter): an unquoted date prints nothing here.
    { kind: 'text', id: 'tab', content: '{attr.issue} · {publishDate}', ...caps(9, 'paper'),
      align: 'right', box: { backgroundColor: col('tomato'),
        padding: { top: mm(1.8), right: mm(3.2), bottom: mm(1.6), left: mm(3.2) } },
      placement: at('page', 'top-right', -SIDE, 44) },
  ] } };
// #endregion

// #region tags: four chip styles replace the built-in pale-blue chip
const chip = (id, look) => ({ id, fontFamily: LABEL, bold: true,
  fontSize: pt(7.7), // in points: em(0.82) is 7.7 pt in the text, 6.6 pt on the 8 pt jump lines
  borderWidth: pt(0), borderRadius: em(1), // a radius past half the height draws a pill
  paddingX: em(0.5), paddingY: em(0.14), ...look }); // em: of the chip's own size
const chipStyles = [
  chip('tag', { background: col('tomato'), color: col('paper') }), // the first is the default
  chip('free', { background: col('marigold'), color: col('ink') }),
  chip('when', { backgroundEnabled: false, borderWidth: pt(0.8), borderColor: col('leaf'),
    color: col('leaf') }),
  chip('jump', { background: col('straw'), color: col('ink') }),
];
// #endregion

// #region box: two columns inside a box set a paragraph beside its drawing
// Text never runs round a picture in a column (text wrap is a gap), but a :::columns group
// inside a box sets blocks side by side; breaks="2" opens column two at the second block:
//   :::callout{type="bed" title="Sixteen squares by the gate"}
//   :::columns{count=2 breaks="2"}
//   The demonstration bed by the gate is 1.2 metres square …   ← block 1
//   ::resource{id="bed"}                                        ← block 2
//   :::
//   :::                                   (gotcha: callout-columns)
const bedBox = { id: 'bed', background: col('tint'), // one device: a tint, no stripe
  padding: { top: mm(3.5), right: mm(4), bottom: mm(4), left: mm(4) }, columnGap: mm(5),
  titleStyle: { ...caps(8.5, 'leaf'), gap: mm(2.4) },
  body: { fontSize: pt(8.8), lineHeight: pt(12.4), paragraphSpacing: false } };
// #endregion

// #region band: a narrower figure still takes the whole band of its column
const drawing = (id, w, h, placement = {}) => ({ id, typeId: 'drawing', kind: 'svg',
  svg: { fileId: `${id}.svg`, width: w * 10, height: h * 10 }, // mm × 10: fitted to the column
  placement: { position: 'here', ...placement }, // drawn where ::resource{id} stands
  caption: CAPTIONS[id][0], note: CAPTIONS[id][1], altText: CAPTIONS[id][2],
  createdAt: 0, updatedAt: 0 });
// width is a fraction of the column and align where the figure sits in it: the text above
// and below never moves into the white either side.
const HEAT = { width: 0.62, align: 'center' };
const resources = () => [drawing('plan', 114, 56.5), drawing('heat', 68, 40, HEAT),
  drawing('bed', 50, 50), DRILL];
// Newsletter drawings carry no "Figure 1": an empty prefix prints no label.
const resourceTypes = [{ id: 'drawing', name: 'Drawing', shortLabel: 'Drawing',
  captionPrefix: '', numberingTemplate: '', resetOn: 'never', counterFormat: 'decimal' }];
// #endregion

const head = (id, content, edge, x, y, look) => ({ kind: 'text', id, content, pages: 'body',
  align: edge.slice(4), placement: at('page', edge, x, y), ...look });
const folio = { elements: [ // page 2's head: title and date over a hairline, the folio right
  head('name', '{title} · {publishDate}', 'top-left', SIDE, 11, caps(7.5, 'leaf')),
  head('folio', '{pageNumber}', 'top-right', -SIDE, 9.6,
    { fontFamily: DISPLAY, fontSize: pt(12), color: col('tomato') }),
  { kind: 'rule', id: 'rule', thickness: pt(0.5), color: col('rule'), pages: 'body',
    placement: { ...at('page', 'top-left', SIDE, 15.5), size: { width: mm(210 - 2 * SIDE) } } },
] };

const label = (size, look = {}) => ({ fontFamily: LABEL, fontSize: pt(size), ...look });
const config = () => ({ // a factory: the engine caches resolved configs per object
  colorPalette, resourceTypes, chipStyles, layout, calloutStyles: [bedBox],
  page: { width: mm(210), height: mm(297), dpi: 150, backgroundColor: col('paper'),
    margins: { top: mm(20), bottom: mm(18), left: mm(SIDE), right: mm(SIDE) } },
  bodyText: { fontFamily: TEXT, fontSize: pt(9.4), lineHeight: pt(LEAD), color: col('ink'),
    referenceColor: col('leaf'), // for a :ref label: the palette reaches bold but not this
    // colour, which would stay the default blue (gotcha: palette-skips-designs)
    // Ragged: no hyphens, no runt check (gotchas: ragged-no-hyphenation, ragged-runts)
    textAlign: 'left', firstLineIndent: pt(0), paragraphSpacing: true },
  headings: { fontFamily: DISPLAY, fontWeight: 400, color: col('leaf'), levels: [
    // Restated (gotcha: headings-drop-h1-break); span: 'page' sets the masthead over both columns
    { level: 1, span: 'page', breakBefore: { enabled: true, parity: 'any' } },
    { level: 2, fontSize: pt(24), lineHeight: pt(2 * LEAD), marginTop: pt(0),
      marginBottom: pt(LEAD / 2) },
    { level: 3, fontFamily: TEXT, fontWeight: 700, fontSize: pt(10.2), lineHeight: pt(LEAD),
      color: col('ink'), marginTop: pt(LEAD), marginBottom: pt(0) }, // a brief's name
    { level: 4, ...caps(8.5, 'tomato'), lineHeight: pt(LEAD), marginTop: pt(LEAD),
      marginBottom: pt(0) }, // a notice's name
  ] },
  headingStyles: [
    // marginBottom 0: the level's 0.5 em is added under minHeight and would drop the text a line
    { id: 'masthead', marginBottom: pt(0), advancedDesign: masthead },
    { id: 'rail', fontSize: pt(17), lineHeight: pt(2 * LEAD), color: col('tomato') },
    { id: 'jump', fontSize: pt(19), lineHeight: pt(1.5 * LEAD), marginTop: pt(LEAD / 2) },
  ],
  paragraphStyles: [
    { id: 'standfirst', fontSize: pt(12), lineHeight: pt(16) },
    { id: 'byline', ...label(8, { color: col('muted'), marginBottom: pt(LEAD / 2) }) },
    { id: 'jump', ...label(8, { textAlign: 'right' }) }, // 'Continued on page 2'
    { id: 'from', ...label(8) }, // 'Continued from page 1'
    { id: 'colophon', ...label(7, { lineHeight: pt(9.4), color: col('muted'),
      marginTop: pt(LEAD) }) },
  ],
  captionStyle: { fontFamily: TEXT, fontSize: pt(8), color: col('ink'), gap: mm(1.6),
    note: { fontFamily: LABEL, fontSize: pt(6.8), color: col('muted') } },
  header: folio,
  footer: { elements: [] }, // the folio is at the head of page 2; page 1 has the masthead
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Markdown样例 · 116行 · content.en.md
title: "The Allotment Gazette"
subtitle: "Newsletter of the Wren Lane Allotment Society"
publishDate: "Spring 2026"
---

# The Allotment Gazette {style="masthead" issue="No. 47"}

:chip[SITE NEWS]{style="tag"}

## Shared compost bays open by the top gate

:::paragraphs{style="standfirst"}
Sixty plots now feed three timber bays instead of a heap each, and bay one reached 63 °C in five days. Its compost goes back to the plots in September.
:::

:::paragraphs{style="byline"}
Maureen Adeyemi, site secretary
:::

::resource{id="plan"}

On the first Saturday of March eleven of us put up three bays of reclaimed scaffold boards by the top gate. Each is a metre and a half square and a metre high, with loose boards at the front that lift out, so a heap can be forked into the next bay. Hallam’s yard on Station Road let us have the boards for the cost of the van, and Ron Ellis brought his drill.

Until now each plot has kept its own heap, and most of those heaps never get warm. A heap needs about a cubic metre of mixed material before it holds its heat, and few of us fill that much in a season. In one bay, with the stable manure the riding school leaves at the gate, the same waste heats up within days.

:::paragraphs{style="jump"}
:chip[Continued on page 2]{style="jump"}
:::

:::columnbreak

## In brief {style="rail"}

### Path day

:chip[WORK PARTY]{style="tag"} :chip[Sun 12 April]{style="when"} The grass paths between the plots need edging, and the main path a fresh load of gravel. Andy Price brings his edging iron; there are spades and barrows. Meet at the hut at nine.

### Seed swap

:chip[EVENT]{style="tag"} :chip[Sat 11 April]{style="when"} Bring spare seed in labelled envelopes to the hut between ten and twelve. Seed saved from open-pollinated plants is welcome; seed from F1 hybrids will not come true. Tea and flapjack, 50p.

### Stable manure

:chip[FREE]{style="free"} Whitecross Riding School leaves a trailer-load at the top gate every other Tuesday. Take what your plot needs, but top up bay one first, and keep the gateway clear for the tractor.

### Jam jars and a gazebo

:chip[WANTED]{style="tag"} Clean jars with lids for the jam stall at the summer show, and a gazebo to borrow on Saturday 18 July. Leave jars in the crate by the hut door; Sue Marsh collects them on Fridays.

### New neighbours

:chip[WELCOME]{style="free"} Four plots changed hands this winter. Welcome to the Okafors on plot 9, Priya and Tom on 23a, Mr Hensley on 31, and the Year 5 class at St Anne’s, who share plot 40 with Mrs Dunn.

:::columnbreak

:::paragraphs{style="from"}
:chip[Continued from page 1]{style="jump"}
:::

## What goes into the bays {style="jump"}

Bay one was filled on 7 March. On the 12th the thermometer at its centre read 63 °C, and the heap stayed at 55 °C or more for six days, long enough to kill most weed seeds. The morning readings are chalked on the board by the gate.

Fill one bay at a time, with green and brown in equal barrow-loads: grass cuttings, weeds without seed heads, spent crops and peelings with torn cardboard, straw and manure. Chop anything thicker than a thumb. Keep out clubroot-infected brassica roots, bindweed and couch grass, and cooked food, which brings rats.

::resource{id="heat"}

Turning lets air into the middle of the heap, and the temperature climbs again: bay one, turned on 18 March, was back above 60 °C two days later. The rota on the hut door puts two plots in charge of the fork each week. In September every plot can take away two barrow-loads of finished compost, and whatever is left goes on the demonstration bed by the gate.

:::callout{type="bed" title="Sixteen squares by the gate"}
:::columns{count=2 breaks="2"}
The demonstration bed by the gate is 1.2 metres square, edged with the same scaffold boards as the bays. This year it holds compost from the council depot, 15 centimetres deep; next spring it gets our own. Strings divide the bed into sixteen squares, 30 centimetres a side, each planted with one, four, nine or sixteen plants according to the size of the crop. Year 5 from St Anne’s planted it on 20 March and will keep its diary.

::resource{id="bed"}
:::
:::

:::columnbreak

## Notices {style="rail"}

#### Rents

Rents for 2026 are £52 for a full plot and £28 for a half, due by the end of April. Pay Dev Sharma on plot 18, or by bank transfer: the details are on the hut door.

#### Water

The troughs are filled from 1 April to the end of October. Use a hose to fill cans only, and never leave one running on a bed.

#### Bonfires

None from April to September, and none at any time when the wind blows towards the houses on Wren Lane.

#### Sheds

A new shed over two metres tall needs the committee’s approval. Send a sketch with its size to the secretary before you buy.

#### Waiting list

Thirty-one names are on the list. We expect to offer eight plots this year, most of them half plots.

#### Bees

On sunny Saturdays in April, Jan inspects the two hives on plot 52. Keep to the main path while her flag is up.

#### Lost

A green ten-litre watering can with a brass rose. Please bring it back to plot 7.

#### Next issue

Please leave copy for the summer issue in the letterbox on the hut door by 15 June.

:::paragraphs{style="colophon"}
The Allotment Gazette is written and put together by members of the Wren Lane Allotment Society. Set in Work Sans, Titan One and Courier Prime (SIL Open Font License) · Text: original, CC BY 4.0.
:::
`; // content.<lang>.md, inlined by the Cookbook

// #region art: the site plan, the heap's temperature and the square-metre bed
function mulberry32(seed) { // a seeded PRNG: the same plots on every run
  return () => {
    seed = (seed + 0x6d2b79f5) | 0;
    let r = Math.imul(seed ^ (seed >>> 15), 1 | seed);
    r = (r + Math.imul(r ^ (r >>> 7), 61 | r)) ^ r;
    return ((r ^ (r >>> 14)) >>> 0) / 4294967296;
  };
}
const channel = (hex, i) => parseInt(hex.slice(i, i + 2), 16);
const mix = (a, b, k) => `#${[1, 3, 5].map((i) => Math.round(channel(a, i) * (1 - k)
  + channel(b, i) * k).toString(16).padStart(2, '0')).join('')}`; // a towards b by k
const f = (v) => +v.toFixed(2);
const P = palette;
const SOIL = mix(P.tomato, P.ink, 0.62);
const EARTH = mix(SOIL, P.straw, 0.28);
const GRASS = mix(P.tint, P.leaf, 0.3);
const DEEP = mix(P.leaf, P.ink, 0.35);
const svgOf = (w, h, body, style = '') => `<svg xmlns="http://www.w3.org/2000/svg" `
  + `width="${w * 10}" height="${h * 10}" viewBox="0 0 ${w} ${h}">${style}${body}</svg>`;
const dot = (x, y, r, fill) => `<circle cx="${f(x)}" cy="${f(y)}" r="${f(r)}" fill="${fill}"/>`;
const rect = (x, y, w, h, fill, extra = '') => `<rect x="${f(x)}" y="${f(y)}" width="${f(w)}" `
  + `height="${f(h)}" fill="${fill}"${extra}/>`;
const line = (x1, y1, x2, y2, stroke, width) => `<path d="M${f(x1)} ${f(y1)}L${f(x2)} ${f(y2)}" `
  + `stroke="${stroke}" stroke-width="${width}" stroke-linecap="round"/>`;

// One plot seen from above: rows of crops across it, sometimes a shed or a greenhouse.
function plot(x, y, w, h, rand, extra) {
  let out = rect(x, y, w, h, EARTH);
  const strips = 2 + Math.floor(rand() * 3);
  let top = y + 0.8;
  for (let s = 0; s < strips; s++) {
    const room = y + h - 0.8 - top;
    if (room < 2) break;
    let sh = s === strips - 1 ? room : Math.max(4, (h - 1.6) * (0.2 + rand() * 0.3));
    if (room - sh < 4) sh = room; // no strip thinner than 4 mm
    const kind = Math.floor(rand() * 6);
    const [x0, x1] = [x + 0.9, x + w - 0.9];
    if (kind === 0) { // rows of lettuce and onions
      for (let yy = top + 1; yy < top + sh - 0.6; yy += 1.7) {
        for (let xx = x0 + 0.6; xx < x1; xx += 1.5) out += dot(xx, yy, 0.55, P.leaf);
      }
    } else if (kind === 1) { // peas and beans up canes
      for (let yy = top + 1.2; yy < top + sh - 0.8; yy += 2.6) out += line(x0, yy, x1, yy, DEEP, 1);
    } else if (kind === 2) { // brassicas under netting
      out += rect(x0 - 0.3, top, x1 - x0 + 0.6, sh - 0.4, mix(P.tint, P.paper, 0.4));
      for (let yy = top + 1.6; yy < top + sh - 1.2; yy += 3) {
        for (let xx = x0 + 1.4; xx < x1 - 0.8; xx += 3) {
          out += dot(xx, yy, 1.1, mix(P.leaf, P.rule, 0.45));
        }
      }
    } else if (kind === 3) { // rhubarb and squashes
      for (let xx = x0 + 2; xx < x1 - 1; xx += 4 + rand() * 2) {
        const yy = top + sh / 2 + (rand() - 0.5) * (sh - 3);
        out += dot(xx, yy, 1.8, P.leaf) + dot(xx + 0.6, yy - 0.5, 0.45, P.marigold);
      }
    } else if (kind === 4) { // dug over and raked
      for (let yy = top + 0.7; yy < top + sh - 0.3; yy += 0.9) {
        out += line(x0, yy, x1, yy, SOIL, 0.25);
      }
    } else { // straw round the strawberries
      out += rect(x0 - 0.3, top, x1 - x0 + 0.6, sh - 0.4, P.straw);
      for (let xx = x0 + 1; xx < x1; xx += 2.2) {
        out += dot(xx, top + sh / 2 - 0.2, 0.8, P.leaf)
          + dot(xx + 0.4, top + sh / 2 + 0.3, 0.3, P.tomato);
      }
    }
    top += sh;
  }
  if (extra === 'shed') { // a shed with its felt roof in tomato, and a water butt
    const sx = rand() < 0.5 ? x + 0.6 : x + w - 5.1;
    out += rect(sx, y + 0.6, 4.5, 3.4, P.tomato) + line(sx, y + 2.3, sx + 4.5, y + 2.3, SOIL, 0.3)
      + dot(sx + (sx > x + 1 ? -1.3 : 5.8), y + 1.6, 0.9, P.ink);
  } else if (extra === 'glass') { // a greenhouse: glass over the whole end of the plot
    out += rect(x + 0.8, y + h - 7.2, w - 1.6, 6.4, mix(P.paper, P.tint, 0.6))
      + [0.25, 0.5, 0.75].map((k) => line(x + 0.8 + k * (w - 1.6), y + h - 7.2,
        x + 0.8 + k * (w - 1.6), y + h - 0.8, P.rule, 0.3)).join('');
  }
  return out;
}

function planSvg(face) { // 114 × 56.5 mm: the top of the Wren Lane site, north up
  const rand = mulberry32(1921); // the year the society took the lease
  const [W, H, PATH] = [114, 56.5, 26.5];
  const label = (lx, ly, s, fill, anchor = 'start') => `<text x="${lx}" y="${ly}" `
    + `font-size="2.3" fill="${fill}" text-anchor="${anchor}">${s}</text>`;
  let out = rect(0, 0, W, H, GRASS) + rect(0, PATH, W, 4.5, P.straw); // the main path, gravel
  out += label(W - 2, PATH + 3, t({ en: 'MAIN PATH', es: 'CAMINO' }), SOIL, 'end');
  // The top gate at the end of the path, and the corner behind it.
  out += rect(0, PATH - 0.8, 1.2, 1.2, P.ink) + rect(0, PATH + 4.1, 1.2, 1.2, P.ink)
    + label(2.2, PATH + 3, t({ en: 'TOP GATE', es: 'PUERTA DE ARRIBA' }), SOIL);
  out += rect(2, 2.4, 11, 8, P.tomato) + rect(2, 6.4, 11, 4, mix(P.tomato, P.ink, 0.22)) // the hut
    + label(7.5, 7.2, t({ en: 'HUT', es: 'CASETA' }), P.paper, 'middle');
  out += rect(15.5, 3.2, 11.5, 3.6, mix(P.rule, P.ink, 0.3)) // the trough
    + rect(16.1, 3.8, 10.3, 2.4, mix(P.tint, P.rule, 0.4));
  for (let i = 0; i < 3; i++) { // the three bays in fresh boards: full, half full, empty
    const bx = 2 + i * 8.6;
    out += rect(bx, 13.5, 7.8, 7.8, P.marigold) + rect(bx + 0.8, 14.3, 6.2, 6.2, SOIL);
    for (let k = 0; k < 16 - i * 7; k++) {
      out += dot(bx + 1.5 + rand() * 4.8, 15 + rand() * 4.8, 0.5, i === 0 ? DEEP : EARTH);
    }
    out += label(bx + 3.9, 24.6, i + 1, P.ink, 'middle');
  }
  out += dot(25.5, 10.5, 3.6, DEEP); // the old pear
  // Plots: four above the path, five below; one split in halves, grass paths between.
  const row = (x0, x1, y, h, n, extras) => {
    const w = (x1 - x0 - (n - 1) * 1.4) / n;
    for (let i = 0; i < n; i++) {
      const px = x0 + i * (w + 1.4);
      if (extras[i] === 'halves') {
        const half = (h - 1.4) / 2;
        out += plot(px, y, w, half, rand) + plot(px, y + half + 1.4, w, half, rand, 'shed');
      } else out += plot(px, y, w, h, rand, extras[i]);
    }
  };
  row(31, W - 2, 2, PATH - 3.5, 4, ['shed', 'halves', '', 'shed']);
  row(2, W - 2, PATH + 6.5, H - PATH - 8.5, 5, ['', 'shed', 'glass', '', 'shed']);
  return svgOf(W, H, out, face);
}
// An SVG drawn as an image cannot see the page's web fonts (gotcha: svg-no-webfonts), so the
// chart carries its label face inline, as a data URL of the Fontsource file.
async function inlineFace(family, weight) {
  const id = family.toLowerCase().replace(/\s+/g, '-');
  const url = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@5/files/${id}-latin-${weight}`
    + '-normal.woff2';
  const bytes = new Uint8Array(await (await fetch(url)).arrayBuffer());
  let bin = '';
  for (const b of bytes) bin += String.fromCharCode(b);
  return `<style>@font-face{font-family:L;src:url(data:font/woff2;base64,${btoa(bin)}) `
    + `format('woff2')}text{font-family:L;font-weight:700}</style>`;
}
const HEAT_LOG = [12, 24, 38, 49, 57, 63, 64, 62, 59, 55, 51, 47, 56, 61, 62, 60, 57, 54, 51, 48,
  46, 44]; // °C at the heap's centre, 7 to 28 March; turned after the reading on the 18th
function heatSvg(face) { // 68 × 40 mm; the plot runs 7–28 March and 0–70 °C
  const [W, H, X0, X1, Y0, Y1] = [68, 40, 9, 66, 3, 33];
  const x = (day) => X0 + ((day - 7) / 21) * (X1 - X0);
  const y = (deg) => Y1 - (deg / 70) * (Y1 - Y0);
  const text = (tx, ty, s, fill, anchor = 'end', size = 2.5) => `<text x="${f(tx)}" y="${f(ty)}" `
    + `font-size="${size}" fill="${fill}" text-anchor="${anchor}">${s}</text>`;
  let out = rect(X0, y(65), X1 - X0, y(55) - y(65), P.straw); // where weed seeds die
  for (const deg of [20, 40, 60]) {
    out += line(X0, y(deg), X1, y(deg), P.rule, 0.2) + text(X0 - 1.2, y(deg) + 0.9, deg, P.muted);
  }
  out += text(X0 - 1.2, y(70) + 0.9, '°C', P.muted); // the unit, over the scale
  for (const day of [7, 14, 21, 28]) {
    out += line(x(day), Y1, x(day), Y1 + 1, P.ink, 0.25)
      + text(x(day), Y1 + 3.8, day === 28 ? t({ en: '28 March', es: '28 marzo' }) : day, P.muted,
        day === 28 ? 'end' : 'middle');
  }
  out += line(x(18.5), y(70), x(18.5), Y1, P.leaf, 0.35)
    + text(x(18.5) + 1, y(70) + 2.2, t({ en: 'turned', es: 'volteo' }), P.leaf, 'start');
  const pts = HEAT_LOG.map((deg, i) => [x(7 + i), y(deg)]);
  out += `<path d="M${pts.map(([px, py]) => `${f(px)} ${f(py)}`).join('L')}" fill="none" `
    + `stroke="${P.tomato}" stroke-width="0.55" stroke-linejoin="round"/>`;
  out += pts.map(([px, py]) => dot(px, py, 0.6, P.tomato)).join('');
  out += line(X0, Y1, X1, Y1, P.ink, 0.3);
  return svgOf(W, H, out, face);
}

// The square-metre bed: sixteen squares of 30 cm, one to sixteen plants in each.
const CROPS = { // plants per square, size and colour of each plant seen from above
  cabbage: [1, 4.2, mix(P.leaf, P.rule, 0.35)], lettuce: [4, 2.1, mix(P.leaf, P.straw, 0.35)],
  chard: [4, 1.9, mix(P.leaf, P.tomato, 0.3)], marigold: [4, 1.5, P.marigold],
  beetroot: [9, 1.1, mix(P.tomato, P.ink, 0.35)], beans: [9, 1.2, P.leaf],
  onion: [9, 0.8, mix(P.straw, P.paper, 0.3)], radish: [16, 0.6, P.tomato],
  carrot: [16, 0.55, mix(P.marigold, P.tomato, 0.35)],
};
const BED = [['cabbage', 'lettuce', 'lettuce', 'marigold'],
  ['beetroot', 'radish', 'carrot', 'onion'], ['chard', 'beans', 'beetroot', 'radish'],
  ['marigold', 'onion', 'carrot', 'lettuce']];
function bedSvg() { // 50 × 50 mm: 1.2 m of bed inside its scaffold boards
  const [S, BOARD] = [50, 2.6];
  const cell = (S - 2 * BOARD) / 4;
  let out = rect(0, 0, S, S, P.marigold) + rect(BOARD, BOARD, S - 2 * BOARD, S - 2 * BOARD, SOIL);
  BED.forEach((cropRow, r) => cropRow.forEach((crop, c) => {
    const [n, size, fill] = CROPS[crop];
    const k = Math.sqrt(n);
    for (let i = 0; i < n; i++) {
      const cx = BOARD + c * cell + ((i % k) + 0.5) * (cell / k);
      const cy = BOARD + r * cell + (Math.floor(i / k) + 0.5) * (cell / k);
      out += dot(cx, cy, size, fill);
      if (crop === 'marigold') out += dot(cx, cy, size * 0.4, P.tomato);
    }
  }));
  for (let i = 1; i < 4; i++) { // the strings
    const at = BOARD + i * cell;
    out += line(at, BOARD, at, S - BOARD, P.paper, 0.25)
      + line(BOARD, at, S - BOARD, at, P.paper, 0.25);
  }
  return svgOf(S, S, out);
}
// A drill of seedlings along the foot of the masthead band, 210 × 8 mm: some show only their
// seed leaves, the rest their first true leaves too.
function leaf(x, y, len, wid, deg, fill) { // a leaf from its stalk end, deg from the vertical
  const a = (deg * Math.PI) / 180;
  const [dx, dy] = [Math.sin(a), -Math.cos(a)];
  const [mx, my, px, py] = [x + (dx * len) / 2, y + (dy * len) / 2, -dy * wid, dx * wid];
  return `<path d="M${f(x)} ${f(y)}Q${f(mx + px)} ${f(my + py)} ${f(x + dx * len)} `
    + `${f(y + dy * len)}Q${f(mx - px)} ${f(my - py)} ${f(x)} ${f(y)}Z" fill="${fill}"/>`;
}
function drillSvg() {
  const rand = mulberry32(47); // the issue number
  const [W, H, RIDGE] = [210, 8, 1.3];
  const SEED = mix(P.leaf, P.straw, 0.3);
  let out = rect(0, H - RIDGE, W, RIDGE, SOIL);
  for (let x = 2.6; x < W - 1; x += 4.6 + rand() * 1.2) {
    const ground = H - RIDGE;
    const grown = rand() < 0.62;
    const stem = grown ? 2.6 + rand() * 1.2 : 1.2 + rand() * 0.8;
    const lean = (rand() - 0.5) * 10;
    out += line(x, ground, x, ground - stem, P.leaf, 0.45);
    const top = ground - stem;
    if (grown) {
      out += leaf(x, ground - stem * 0.45, 1.6, 0.55, -68 + lean, SEED)
        + leaf(x, ground - stem * 0.45, 1.6, 0.55, 68 + lean, SEED)
        + leaf(x, top, 2.6 + rand() * 0.5, 1, -32 + lean, P.leaf)
        + leaf(x, top, 2.6 + rand() * 0.5, 1, 32 + lean, P.leaf);
    } else {
      out += leaf(x, top, 1.7, 0.6, -58 + lean, SEED) + leaf(x, top, 1.7, 0.6, 58 + lean, SEED);
    }
  }
  return svgOf(W, H, out);
}

// What the drawings say under them, in the sample's language: caption, credit note, alt text.
const CAPTIONS = {
  plan: [t({
    en: '**The top of the Wren Lane site, from the air.** The three new bays stand between '
      + 'the hut and the top gate.',
    es: '**La parte alta del Soto, desde el aire.** Los tres cajones nuevos están entre la '
      + 'caseta y la puerta de arriba.' }),
  t({ en: 'Drawing: The Gazette, from the society’s site plan',
    es: 'Dibujo: La Gaceta, a partir del plano de la asociación' }),
  t({ en: 'Plan of allotment plots seen from above, with three compost bays by the gate.',
    es: 'Plano de parcelas de huerto vistas desde arriba, con tres cajones de compost junto a la '
      + 'puerta.' })],
  heat: [t({
    en: '**Bay one in March.** Temperature at the centre of the heap, read at nine each '
      + 'morning. In the shaded band, 55 to 65 °C, most weed seeds die.',
    es: '**El cajón uno en marzo.** Temperatura en el centro, a las nueve. En la franja, de '
      + '55 a 65 °C, mueren casi todas las semillas de malas hierbas.' }),
  t({ en: 'Readings: the compost rota', es: 'Lecturas: el turno del compost' }),
  t({ en: 'Line chart: the heap rises from 12 °C to 64 °C in six days, cools to 47 °C, and '
      + 'climbs back to 62 °C after it is turned on 18 March.',
    es: 'Gráfico de líneas: el montón sube de 12 °C a 64 °C en seis días, baja a 47 °C y vuelve '
      + 'a 62 °C después del volteo del 18 de marzo.' })],
  bed: [t({
    en: '**What goes where.** One cabbage to a square; four lettuces, chard or marigolds; '
      + 'nine beetroot, beans or onions; sixteen radishes or carrots.',
    es: '**Cómo se planta el bancal.** Una col por cuadro; cuatro lechugas, acelgas o '
      + 'caléndulas; nueve remolachas, judías o cebollas; dieciséis rábanos o zanahorias.' }),
  t({ en: 'Drawing: The Gazette', es: 'Dibujo: La Gaceta' }),
  t({ en: 'A square bed divided by strings into sixteen squares, each planted with one to '
      + 'sixteen plants.', es: 'Un bancal cuadrado dividido con cuerdas en dieciséis cuadros, '
      + 'cada uno con entre una y dieciséis plantas.' })],
};
// #endregion

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
// Text, display and label faces, loaded before the build (gotcha: fonts-first).
const FONTS = {
  'Work Sans': ['400', '700'], 'Titan One': ['400'], 'Courier Prime': ['400', '700'] };

// ─── 4 · Build & show ───────────────────────────────────────────────────────
await loadFonts(FONTS, markdown);
const face = await inlineFace(LABEL, 700); // the label face, for the drawings' own lettering
await Promise.all([loadSvg('plan.svg', planSvg(face)), loadSvg('heat.svg', heatSvg(face)),
  loadSvg('bed.svg', bedSvg()), loadSvg('drill.svg', drillSvg())]);
const doc = await buildWithFonts(
  () => buildDocument({ markdown, resources: resources() }, config()), markdown);
showPages(doc, { title: t({ en: 'Community newsletter', es: 'Boletín vecinal' }) });

工具包 · core, fonts, viewer, images：每道食谱都相同 · 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 ───────────────────────────────────────────────────────────────────────