What you'll build

A poster from a fictional astronomy club for four Thursday lectures before the total solar eclipse of 2 August 2027. An ultramarine sky fills the top two thirds of an A3 sheet. On the right a black Moon covers a lemon Sun cut off by the trim, and a corona drawn in code spreads behind both. The title, The Shadow Returns in 120 pt Funnel Display, stands on its standfirst at the foot of the sky. Under the horizon four blue dates head the talks, and the fine print runs in two columns above a blue band. Each element hangs from the bleed, the page, its slot or another element, and its offsets count from there. The second sheet repeats the poster with a pink frame round each element’s box and round the header and footer containers, and a tag on thirteen elements that prints each one’s placement.

This recipe answers

How do I place design elements against the page, the bleed or one another instead of by coordinates?
How do I add a watermark, a background tint or a decorative image on every page?

The short answer

script.js · lines 57–73in full code

const SKY = 272; // mm from the trim's top edge to the horizon, the sky's lower edge
const INSET = BLEED + MARGIN; // from the bleed's edge to the text's edge
const AIR = 14; // mm between the standfirst and the horizon
const poster = () => ({ enabled: true, slot: { elements: [ // array order is paint order
  // 'bleed' and 'page' are frames of the sheet; 'container' would be this heading's own box.
  { kind: 'box', id: 'sky', style: { backgroundColor: col('sky') }, // no width: fills the bleed
    placement: at('bleed', 'top-left', 0, 0, { height: mm(BLEED + SKY) }) },
  ...eclipse(), // the Sun hangs from the trim's corner, the Moon and the corona from the Sun
  // The headline stands on the horizon and grows upwards: 'above' puts an element's
  // bottom-left corner on the top-left corner of its anchor, so a longer title lifts the kicker.
  text('deck', '{attr.deck}', FACE.deck, { ...at('#sky', 'align-bottom', INSET, -AIR),
    size: { maxWidth: mm(153) } }), // shrink-wraps its lines, but wraps at 153 mm
  text('title', '{titleText}', FACE.title, at('#deck', 'above', 0, -9)), // breaks at the \\
  text('kicker', '{attr.kicker}', FACE.kicker, at('#title', 'above', 0, -7)),
  ...programme(), // four columns chained off the horizon
] } }); // hook-up: headings.levels[0] = { span: 'page', breakBefore, advancedDesign: poster() }
// {titleText} is the heading's text; each {attr.*} is written on its line in content.md.

Two elements pinned to frames of the sheet, every other one to an element

Ingredients

Features: Anchoring design elements Text, rules and boxes in page designs Pictures in page designs Designed openers Full-width chapter band Bleed bands and thumb tabs Heading styles Running heads per section Heading attributes Line breaks in titles Semantic colour palette Paragraph styles Figures and tables as resources Pages on a canvas
Also uses: Bleed and crop marks
Type: Funnel Display, Funnel Sans, Martian Mono (SIL OFL 1.1)
Assets: None: every picture is drawn in code
API: buildDocumentclearMeasurementCacheregisterResourceImagerenderPageToCanvas

Method

#1 · Pin two elements to the sheet and hang the rest from them

The code is the short answer above. In it, anchor.to names what an element hangs from: 'bleed' and 'page' are frames of the sheet (the same box while page.cutLines is off), 'container' is the slot’s own box and '#id' is another element (element placement). A box with no width runs to the far edge of its frame, so the sky fills the bleed from side to side. An element placed against the sky measures from the sky’s left edge, which is the bleed’s, so the standfirst takes INSET, 18 mm, as its x. The headline is built upwards from the sky’s lower edge. 'align-bottom' puts the foot of the standfirst’s box AIR, 14 mm, above that edge, and 'above' sets each element’s foot on the top of the one below it, so a title that runs to more lines lifts the kicker instead of covering the standfirst. Under the design, the fine print starts on the first 16 pt grid line at least 3.2 mm below the lowest element, the speakers’ line; those 3.2 mm are the heading’s default bottom margin.

#2 · Hang the Moon and the corona from the Sun

script.js · lines 77–88in full code

const SUN = 150; // mm across; the Moon is drawn the same size
const CORONA = 300; // mm, the square picture of the corona
const HALO = (CORONA - SUN) / 2; // how far the corona reaches past the Sun on every side
const BITE = { x: 2, y: 2.5 }; // mm the Moon sits off the Sun: a sliver is left at upper left
const disc = (id, colour, placement) => ({ kind: 'box', id, placement: { ...placement,
  size: square(SUN) }, style: { backgroundColor: col(colour), borderRadius: mm(SUN / 2) } });
const eclipse = () => [
  { kind: 'image', id: 'corona', resourceId: 'corona', // listed before the discs: painted behind
    placement: at('#sun', 'align-top', -HALO, -HALO, square(CORONA)) },
  disc('sun', 'sun', at('page', 'top-right', 30, 25)), // 30 mm of it past the right edge
  disc('moon', 'ink', at('#sun', 'align-top', BITE.x, BITE.y)),
];

The Sun is the one element pinned to the page, the trim box. Measured from the 'top-right' corner, a positive x runs past the right edge, so 30 mm of the disc is cut off. The Moon and the corona hang from the Sun with 'align-top', so moving the Sun moves both. Their offsets count from the Sun’s top-left corner: the Moon sits 2 mm right and 2.5 mm down, which leaves a sliver of Sun at the upper left, and the corona starts HALO, 75 mm, up and to the left, which centres its 300 mm square on the 150 mm disc. The corona is an image element that takes the size of its box (image elements) and comes before the discs in the list, so it is painted behind them.

#3 · Chain the evenings into columns

script.js · lines 92–101in full code

const GUT = 7; // mm between the evenings, and between the two columns of text under them
const COL = (A3.width - 2 * MARGIN - 3 * GUT) / 4; // four columns across the text width: 60 mm
const DROP = 12; // mm from the horizon to the dates
const programme = () => [1, 2, 3, 4].flatMap((n) => [
  text(`day${n}`, `{attr.d${n}}`, FACE.day, n === 1
    ? at('#sky', 'below', INSET, DROP, wide(COL)) // the first date hangs from the horizon
    : at(`#day${n - 1}`, 'right-of', GUT, 0, wide(COL))), // the others from the one before
  text(`talk${n}`, `{attr.t${n}}`, FACE.talk, at(`#day${n}`, 'below', 0, 3, wide(COL))),
  text(`who${n}`, `{attr.s${n}}`, FACE.who, at(`#talk${n}`, 'below', 0, 2.5, wide(COL))),
]);

Each date, talk and speaker line has a fixed size.width of COL, and 'right-of' plus GUT lays the next date one column over. Without a width a date shrink-wraps to its digits (the ‘8’ is 17 mm wide), so the ‘15’ would start 7 mm after it and each talk would run on one line into the next column. COL splits the text width into four with the same 7 mm gutter as the two columns of fine print below, which puts the second column of fine print under the 22. Each talk hangs 'below' its date and each speaker line below its talk, so a talk that wrapped to a third line would push down its own speaker and no other.

script.js · lines 105–116in full code

const MARK = 10; // mm, the club's mark
const PAD = (FOOT - MARK) / 2; // centres the mark in the bottom margin
const markTall = { height: mm(MARK) }; // as tall as the mark: the line is centred on it
const footer = { elements: [
  { kind: 'box', id: 'band', style: { backgroundColor: col('sky') }, // the bottom margin, bled
    placement: at('bleed', 'bottom-left', 0, 0, { height: mm(BLEED + FOOT) }) },
  // The container runs from the text down to the trim: 'bottom-*' counts up, 'top-*' down.
  { kind: 'image', id: 'mark', resourceId: 'mark',
    placement: at('container', 'bottom-left', 0, -PAD, square(MARK)) },
  text('club', '{attr.club}', FACE.foot, at('#mark', 'right-of', 3, 0, markTall)),
  text('free', '{attr.free}', FACE.foot, at('container', 'top-right', 0, PAD, markTall)),
] };

Anything that has to print on every page, such as this band, goes in the header or footer slot, and a heading style with a header or footer of its own replaces that slot on its section’s pages. The guides style’s footer repeats these four elements with their frames and tags, which is why the band and the mark print on both sheets. The footer’s container is the bottom margin, from the text down to the trim: 'bottom-left' counts up from the trim and 'top-right' down from the text, and the mark’s −10 and the “Free entry” line’s +10 land on the same 10 mm strip in the middle of the band (headers and footers). The footer is painted after the text and takes no room from it, so FOOT sets both the bottom margin and the band’s height, and the band stays clear of the lines above it.

#5 · Draw the construction lines from the same config

script.js · lines 120–147in full code

const GUIDE = { borderColor: col('guide'), borderWidth: pt(1) };
const signed = ({ value }) => `${value < 0 ? '−' : '+'}${Math.abs(value)}`; // all offsets in mm
const describe = ({ id, placement: { anchor: { to, edge }, offset = {} } }) => [`#${id}`,
  `${edge} ${to}`, // the two words of anchor: { to, edge }
  ['x', 'y'].filter((k) => offset[k]?.value).map((k) => `${k} ${signed(offset[k])}`).join(' '),
].filter(Boolean).join(' · ');
// A border never changes an element's size (padding does), so each frame traces its box.
// An image or a rounded box gets a square frame of its size, hung from its top-left corner.
const frame = (el) => (el.kind === 'text' ? [{ ...el, box: { ...el.box, ...GUIDE } }]
  : el.kind === 'box' && !el.style.borderRadius ? [{ ...el, style: { ...el.style, ...GUIDE } }]
    : [el, { kind: 'box', id: `${el.id}-box`, style: GUIDE,
      placement: at(`#${el.id}`, 'align-top', 0, 0, el.placement.size) }]);
const tag = (el, [edge, x = 0, y = 0, note]) => text(`${el.id}-tag`, note ?? describe(el),
  face('Martian Mono', 8.5, 500, 'ink', { box: { backgroundColor: col('guide'),
    padding: { top: pt(1.6), bottom: pt(1.2), left: pt(3), right: pt(3) } } }),
  at(`#${el.id}`, edge, x, y));
const guides = (elements, tags) => [...elements.flatMap(frame),
  ...elements.filter((el) => tags[el.id]).map((el) => tag(el, tags[el.id]))];
const container = (id) => ({ kind: 'box', id, style: GUIDE, // the slot's own box, drawn
  placement: at('container', 'top-left', 0, 0, { width: 'fill', height: 'fill' }) });
const TAGS = { // where each tag sits against its element: [edge, x, y, text]
  sky: ['align-bottom', INSET, -3], corona: ['align-bottom', 90, -2], sun: ['above'],
  moon: ['below', 20, 2], kicker: ['above'], title: ['above'], deck: ['above'],
  day1: ['above', 0, -6], day2: ['above'], who1: ['below'],
  mark: ['above', 0, -2], club: ['above', 69, -2], free: ['above', -30, -2],
  header: ['align-bottom', 0, -2, t({ en: 'header container', es: 'contenedor de la cabecera' })],
  footer: ['align-bottom', 0, -2, t({ en: 'footer container', es: 'contenedor del pie' })],
};

guides() walks the poster’s elements. A text gets a border on its box and a square box a border on its style; neither moves anything, because only padding makes a box bigger. An image or a round disc gets a square box of its own size hung from its top-left corner, so the corner of the Sun that the Moon and the corona hang from is drawn too. Each tag is a text hung from its element, written by describe() from that element’s own placement, so a tag cannot disagree with the config it labels. {style="guides"} on the second heading brings in this design and a header and footer of its own (heading styles). A tag with no width only has the room between its anchor and the container’s right edge, which is why the #free tag starts 30 mm left of its text. pageIndexOffset: 1, in the content’s continuation, makes the poster a verso, so the viewer sets the two sheets side by side.

The whole recipe

// ═══ Postext Cookbook · Nº 029 · Anchoring cheat sheet: a poster built from chained elements ═══
// https://postext.dev/en/cookbook/anchoring-cheat-sheet
// Code: MIT · Text: original (CC BY 4.0) · Drawings: generated in code (CC BY 4.0)
// Fonts: Funnel Display, Funnel Sans, Martian Mono (SIL OFL 1.1) · Needs postext ≥ 1.4.1
// An A3 poster whose elements hang from the bleed, the page, their slot or one another, never
// from coordinates; the second sheet is the same poster with each element framed and tagged.
import {
  buildDocument, renderPageToCanvas, clearMeasurementCache, registerResourceImage,
} from 'https://esm.sh/postext';

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

// ─── 1 · Design ─────────────────────────────────────────────────────────────
const palette = {
  ink: '#0b0b0c', // text, and the Moon
  sky: '#1b3bff', // the sky, the foot band and the dates
  sun: '#ffe53b', // the Sun and the kicker
  paper: '#ffffff', // type on the sky
  muted: '#5c5f66', // speakers and the colophon
  guide: '#ff2d9b', // frames and tags on the construction sheet
};
// col(id): a palette-linked colour that also carries its hex, because 1.4.1 paints design
// elements from the hex (gotcha: palette-skips-designs).
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' } })),
  { id: 'main-color', name: 'sky (defaults)', value: { hex: palette.sky, model: 'hex' } },
];

const A3 = { width: 297, height: 420 }; // mm, the trim
const MARGIN = 18; // mm at the top and sides: the body's edges, and the header container's
const FOOT = 30; // mm, the bottom margin: the footer container and its band
const BLEED = 0; // mm; 3 for the printer, which switches on page.cutLines below
// at(): a placement. Offsets are distances from the anchor point, never page coordinates.
const at = (to, edge, x = 0, y = 0, size) => ({ anchor: { to, edge },
  offset: { x: mm(x), y: mm(y) }, ...(size && { size }) });
const wide = (w) => ({ width: mm(w) }); // fixed, so a text is as wide as its column
const square = (d) => ({ width: mm(d), height: mm(d) });
// Design text is centred and cut with '…' by default (gotcha: overflow-ellipsis-default).
const text = (id, content, face, placement) => ({ kind: 'text', id, content, overflow: 'wrap',
  align: 'left', ...face, placement });
const face = (fontFamily, size, fontWeight, colour, more) => ({ fontFamily, fontSize: pt(size),
  fontWeight, color: col(colour), ...more });
const caps = (tracking) => ({ letterSpacing: pt(tracking), textTransform: 'uppercase' });
const FACE = { // lineHeight: a multiple, never pt() (gotcha: design-lineheight-multiple)
  kicker: face('Martian Mono', 12, 500, 'sun', caps(1.8)),
  title: face('Funnel Display', 120, 800, 'paper', { lineHeight: 0.86 }),
  deck: face('Funnel Sans', 22, 400, 'paper', { lineHeight: 1.22 }),
  day: face('Funnel Display', 84, 800, 'sky', { lineHeight: 0.9 }),
  talk: face('Funnel Sans', 19, 600, 'ink', { lineHeight: 1.14 }),
  who: face('Funnel Sans', 12.5, 400, 'muted', { lineHeight: 1.3, italic: true }),
  foot: face('Martian Mono', 9, 500, 'paper', caps(0.9)),
};

// #region answer: two elements pinned to frames of the sheet, every other one to an element
const SKY = 272; // mm from the trim's top edge to the horizon, the sky's lower edge
const INSET = BLEED + MARGIN; // from the bleed's edge to the text's edge
const AIR = 14; // mm between the standfirst and the horizon
const poster = () => ({ enabled: true, slot: { elements: [ // array order is paint order
  // 'bleed' and 'page' are frames of the sheet; 'container' would be this heading's own box.
  { kind: 'box', id: 'sky', style: { backgroundColor: col('sky') }, // no width: fills the bleed
    placement: at('bleed', 'top-left', 0, 0, { height: mm(BLEED + SKY) }) },
  ...eclipse(), // the Sun hangs from the trim's corner, the Moon and the corona from the Sun
  // The headline stands on the horizon and grows upwards: 'above' puts an element's
  // bottom-left corner on the top-left corner of its anchor, so a longer title lifts the kicker.
  text('deck', '{attr.deck}', FACE.deck, { ...at('#sky', 'align-bottom', INSET, -AIR),
    size: { maxWidth: mm(153) } }), // shrink-wraps its lines, but wraps at 153 mm
  text('title', '{titleText}', FACE.title, at('#deck', 'above', 0, -9)), // breaks at the \\
  text('kicker', '{attr.kicker}', FACE.kicker, at('#title', 'above', 0, -7)),
  ...programme(), // four columns chained off the horizon
] } }); // hook-up: headings.levels[0] = { span: 'page', breakBefore, advancedDesign: poster() }
// {titleText} is the heading's text; each {attr.*} is written on its line in content.md.
// #endregion

// #region eclipse: the Sun pinned to the trim's corner, the Moon and the corona to the Sun
const SUN = 150; // mm across; the Moon is drawn the same size
const CORONA = 300; // mm, the square picture of the corona
const HALO = (CORONA - SUN) / 2; // how far the corona reaches past the Sun on every side
const BITE = { x: 2, y: 2.5 }; // mm the Moon sits off the Sun: a sliver is left at upper left
const disc = (id, colour, placement) => ({ kind: 'box', id, placement: { ...placement,
  size: square(SUN) }, style: { backgroundColor: col(colour), borderRadius: mm(SUN / 2) } });
const eclipse = () => [
  { kind: 'image', id: 'corona', resourceId: 'corona', // listed before the discs: painted behind
    placement: at('#sun', 'align-top', -HALO, -HALO, square(CORONA)) },
  disc('sun', 'sun', at('page', 'top-right', 30, 25)), // 30 mm of it past the right edge
  disc('moon', 'ink', at('#sun', 'align-top', BITE.x, BITE.y)),
];
// #endregion

// #region programme: four evenings in fixed-width columns, chained right-of and below
const GUT = 7; // mm between the evenings, and between the two columns of text under them
const COL = (A3.width - 2 * MARGIN - 3 * GUT) / 4; // four columns across the text width: 60 mm
const DROP = 12; // mm from the horizon to the dates
const programme = () => [1, 2, 3, 4].flatMap((n) => [
  text(`day${n}`, `{attr.d${n}}`, FACE.day, n === 1
    ? at('#sky', 'below', INSET, DROP, wide(COL)) // the first date hangs from the horizon
    : at(`#day${n - 1}`, 'right-of', GUT, 0, wide(COL))), // the others from the one before
  text(`talk${n}`, `{attr.t${n}}`, FACE.talk, at(`#day${n}`, 'below', 0, 3, wide(COL))),
  text(`who${n}`, `{attr.s${n}}`, FACE.who, at(`#talk${n}`, 'below', 0, 2.5, wide(COL))),
]);
// #endregion

// #region footer: a band and the club's mark in the footer slot, which prints on every page
const MARK = 10; // mm, the club's mark
const PAD = (FOOT - MARK) / 2; // centres the mark in the bottom margin
const markTall = { height: mm(MARK) }; // as tall as the mark: the line is centred on it
const footer = { elements: [
  { kind: 'box', id: 'band', style: { backgroundColor: col('sky') }, // the bottom margin, bled
    placement: at('bleed', 'bottom-left', 0, 0, { height: mm(BLEED + FOOT) }) },
  // The container runs from the text down to the trim: 'bottom-*' counts up, 'top-*' down.
  { kind: 'image', id: 'mark', resourceId: 'mark',
    placement: at('container', 'bottom-left', 0, -PAD, square(MARK)) },
  text('club', '{attr.club}', FACE.foot, at('#mark', 'right-of', 3, 0, markTall)),
  text('free', '{attr.free}', FACE.foot, at('container', 'top-right', 0, PAD, markTall)),
] };
// #endregion

// #region guides: the same slots, each element framed and tagged with its own placement
const GUIDE = { borderColor: col('guide'), borderWidth: pt(1) };
const signed = ({ value }) => `${value < 0 ? '−' : '+'}${Math.abs(value)}`; // all offsets in mm
const describe = ({ id, placement: { anchor: { to, edge }, offset = {} } }) => [`#${id}`,
  `${edge} ${to}`, // the two words of anchor: { to, edge }
  ['x', 'y'].filter((k) => offset[k]?.value).map((k) => `${k} ${signed(offset[k])}`).join(' '),
].filter(Boolean).join(' · ');
// A border never changes an element's size (padding does), so each frame traces its box.
// An image or a rounded box gets a square frame of its size, hung from its top-left corner.
const frame = (el) => (el.kind === 'text' ? [{ ...el, box: { ...el.box, ...GUIDE } }]
  : el.kind === 'box' && !el.style.borderRadius ? [{ ...el, style: { ...el.style, ...GUIDE } }]
    : [el, { kind: 'box', id: `${el.id}-box`, style: GUIDE,
      placement: at(`#${el.id}`, 'align-top', 0, 0, el.placement.size) }]);
const tag = (el, [edge, x = 0, y = 0, note]) => text(`${el.id}-tag`, note ?? describe(el),
  face('Martian Mono', 8.5, 500, 'ink', { box: { backgroundColor: col('guide'),
    padding: { top: pt(1.6), bottom: pt(1.2), left: pt(3), right: pt(3) } } }),
  at(`#${el.id}`, edge, x, y));
const guides = (elements, tags) => [...elements.flatMap(frame),
  ...elements.filter((el) => tags[el.id]).map((el) => tag(el, tags[el.id]))];
const container = (id) => ({ kind: 'box', id, style: GUIDE, // the slot's own box, drawn
  placement: at('container', 'top-left', 0, 0, { width: 'fill', height: 'fill' }) });
const TAGS = { // where each tag sits against its element: [edge, x, y, text]
  sky: ['align-bottom', INSET, -3], corona: ['align-bottom', 90, -2], sun: ['above'],
  moon: ['below', 20, 2], kicker: ['above'], title: ['above'], deck: ['above'],
  day1: ['above', 0, -6], day2: ['above'], who1: ['below'],
  mark: ['above', 0, -2], club: ['above', 69, -2], free: ['above', -30, -2],
  header: ['align-bottom', 0, -2, t({ en: 'header container', es: 'contenedor de la cabecera' })],
  footer: ['align-bottom', 0, -2, t({ en: 'footer container', es: 'contenedor del pie' })],
};
// #endregion

const LEAD = 16; // body leading in pt
const config = () => ({ // a factory: configs are cached by identity (gotcha: config-cache-identity)
  colorPalette,
  page: { width: mm(A3.width), height: mm(A3.height), dpi: 150, // 150 dpi is for the screen
    cutLines: { enabled: BLEED > 0, bleed: mm(BLEED) },
    margins: { top: mm(MARGIN), bottom: mm(FOOT), left: mm(MARGIN), right: mm(MARGIN) } },
  layout: { layoutType: 'double', gutterWidth: mm(GUT) }, // the text columns under the evenings
  bodyText: { fontFamily: 'Funnel Sans', fontSize: pt(12), lineHeight: pt(LEAD), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), textAlign: 'left', firstLineIndent: pt(0),
    paragraphSpacing: true },
  // The hidden title is still measured, so it needs a face FONTS loads.
  headings: { fontFamily: 'Funnel Display', fontWeight: 800,
    levels: [{ level: 1, span: 'page', advancedDesign: poster(),
      breakBefore: { enabled: true, parity: 'any' } }] }, // gotcha: headings-drop-h1-break
  // {style="guides"}: the same design framed and tagged, and a header and footer of its own.
  headingStyles: [{ id: 'guides',
    advancedDesign: { enabled: true, slot: { elements: guides(poster().slot.elements, TAGS) } },
    header: { elements: guides([container('header')], TAGS) },
    footer: { elements: guides([...footer.elements, container('footer')], TAGS) } }],
  paragraphStyles: [{ id: 'colophon', fontFamily: 'Martian Mono', fontSize: pt(8),
    lineHeight: pt(LEAD * 0.75), color: col('muted') }],
  header: { elements: [] }, // the poster has none; the guides page draws the empty container
  footer,
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`# The\\Shadow\\Returns {kicker="April 2027 · Thursdays at 19:30" deck="Four talks to get ready for the total eclipse of 2 August 2027, when the Moon’s shadow crosses the Strait of Gibraltar." d1="8" t1="Why the Moon fits the Sun" s1="Marta Iribarren, astronomer" d2="15" t2="Where the shadow will fall" s2="Óscar Beltrán, meteorologist" d3="22" t3="What the corona tells us" s3="Lucía Ferrándiz, physicist" d4="29" t4="Looking at the Sun without harm" s4="Tomás Rey, optometrist" club="Umbra Circle · amateur astronomers since 1987" free="Free entry · no booking"}
Markdown sample · 14 lines · content.en.md

Every lecture begins at 19:30 and lasts about an hour, questions included. The Umbra Circle hall is at 14 Lighthouse Road; the doors open at 19:00, entry is free and there is no booking, so the 120 seats go to whoever comes first.

On 29 April every listener takes home a pair of eclipse glasses made to ISO 12312-2: wear them through each partial phase, and take them off only while the Sun is completely covered. On eclipse morning the Circle sets up filtered telescopes on the harbour wall.

# The\\Shadow\\Returns {style="guides" kicker="April 2027 · Thursdays at 19:30" deck="Four talks to get ready for the total eclipse of 2 August 2027, when the Moon’s shadow crosses the Strait of Gibraltar." d1="8" t1="Why the Moon fits the Sun" s1="Marta Iribarren, astronomer" d2="15" t2="Where the shadow will fall" s2="Óscar Beltrán, meteorologist" d3="22" t3="What the corona tells us" s3="Lucía Ferrándiz, physicist" d4="29" t4="Looking at the Sun without harm" s4="Tomás Rey, optometrist" club="Umbra Circle · amateur astronomers since 1987" free="Free entry · no booking"}

**How to read this sheet.** Each pink frame is an element’s box as laid out, and a tag gives an element’s id, the edge it is pinned by, what it is pinned to and any offset in millimetres. Above the footer only two elements hang from the sheet itself: the sky from the bleed and the Sun from the page, which is the trim. Every other one hangs from an element, so a longer title lifts the kicker, and the four evenings move with the horizon.

The frames in the top and bottom margins are the header and footer containers. The footer container runs from the text down to the trim, so its bottom anchors count up from the trim and its top anchors down from the text.

:::paragraphs{style="colophon"}
Set in Funnel Display, Funnel Sans and Martian Mono (SIL OFL) · Text and drawings: original, CC BY 4.0 · The Umbra Circle and its speakers are fictional.
:::
`; // content.<lang>.md, inlined by the Cookbook

// #region art: the corona and the club's mark, drawn in code, and their resources
function mulberry32(seed) { // a seeded generator: the same corona on every run
  return () => {
    seed = (seed + 0x6d2b79f5) | 0;
    let t = Math.imul(seed ^ (seed >>> 15), 1 | seed);
    t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
    return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
  };
}
function coronaSvg() { // a glow, then 14 streamers, 70 polar plumes and 160 fine rays
  const rand = mulberry32(20270802);
  const R = (500 * SUN) / CORONA; // the Sun's radius in the 1000-unit square
  const TILT = Math.PI / 4; // the Sun's equator: long streamers go up-left, clear of the kicker
  const TYPE = [2.2, 3.05]; // radians from the centre where the type is: rays there stop at 9 mm
  const p = (r, a) => `${(500 + r * Math.cos(a)).toFixed(1)} ${(500 + r * Math.sin(a)).toFixed(1)}`;
  const ray = (a, full, half, opacity) => { // a petal from the limb, tapered to a point
    const turn = ((a % (2 * Math.PI)) + 2 * Math.PI) % (2 * Math.PI);
    const length = turn > TYPE[0] && turn < TYPE[1] ? Math.min(full, R * 0.12) : full;
    const bend = (rand() - 0.5) * 0.06;
    return `<path d="M${p(R * 0.97, a - half)}C${p(R + length * 0.35, a - half * 1.1)} `
      + `${p(R + length * 0.7, a + bend - half * 0.25)} ${p(R + length, a + bend)}`
      + `C${p(R + length * 0.7, a + bend + half * 0.25)} ${p(R + length * 0.35, a + half * 1.1)} `
      + `${p(R * 0.97, a + half)}Z" fill="${palette.paper}" fill-opacity="${opacity.toFixed(3)}"/>`;
  };
  const glow = Array.from({ length: 28 }, (_, i) => `<circle cx="500" cy="500" `
    + `r="${(R * (1.01 + i * 0.022)).toFixed(1)}" fill="${palette.paper}" fill-opacity="0.022"/>`)
    .reverse().join('');
  const out = [];
  for (let i = 0; i < 14; i++) { // helmet streamers, two fans across the equator
    const a = TILT + (i % 2) * Math.PI + (rand() - 0.5) * 1.1;
    out.push(ray(a, R * (0.55 + 0.45 * rand()), 0.1 + 0.14 * rand(), 0.06 + 0.06 * rand()));
  }
  for (let i = 0; i < 70; i++) { // polar plumes, shorter and thinner than the streamers
    const a = TILT + Math.PI / 2 + (i % 2) * Math.PI + (rand() - 0.5) * 1.3;
    out.push(ray(a, R * (0.18 + 0.3 * rand()), 0.008 + 0.012 * rand(), 0.1 + 0.12 * rand()));
  }
  for (let i = 0; i < 160; i++) { // fine rays all round
    const a = (i / 160) * 2 * Math.PI + (rand() - 0.5) * 0.04;
    out.push(ray(a, R * (0.12 + 0.3 * rand()), 0.006 + 0.014 * rand(), 0.05 + 0.07 * rand()));
  }
  return `<svg xmlns="http://www.w3.org/2000/svg" width="1500" height="1500" `
    + `viewBox="0 0 1000 1000">${glow}${out.join('')}</svg>`;
}
function markSvg() { // the Umbra Circle's mark: a ring round an eclipsed Sun
  return `<svg xmlns="http://www.w3.org/2000/svg" width="200" height="200" viewBox="0 0 100 100">`
    + `<circle cx="50" cy="50" r="45" fill="none" stroke="${palette.paper}" stroke-width="6"/>`
    + `<circle cx="50" cy="50" r="27" fill="${palette.sun}"/>`
    + `<circle cx="56" cy="45" r="27" fill="${palette.sky}"/></svg>`;
}
const svg = (id, size, altText) => ({ id, typeId: 'figure', kind: 'svg', altText,
  svg: { fileId: `${id}.svg`, width: size, height: size }, createdAt: 0, updatedAt: 0 });
// Image elements draw resources. Nothing cites them, so neither is placed or numbered as a figure.
const resources = [
  svg('corona', 1500, t({ en: 'The solar corona round the eclipsed Sun',
    es: 'La corona solar alrededor del Sol eclipsado' })),
  svg('mark', 200, t({ en: 'The Umbra Circle’s mark', es: 'El emblema del Círculo Umbra' })),
];
// #endregion

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
// Every face the pages paint, loaded before the first build (gotcha: fonts-first).
const FONTS = {
  'Funnel Display': ['800'],
  'Funnel Sans': ['400', '400i', '600', '700'],
  'Martian Mono': ['400', '500'],
};

// ─── 4 · Build & show ───────────────────────────────────────────────────────
await loadSvg('corona.svg', coronaSvg());
await loadSvg('mark.svg', markSvg());
await loadFonts(FONTS, markdown);
// pageIndexOffset 1 makes the poster a verso, so the viewer sets the two sheets side by side.
const content = { markdown, resources, continuation: { pageIndexOffset: 1 } };
const doc = await buildWithFonts(() => buildDocument(content, config()), markdown);
showPages(doc, { title: t({ en: 'Anchoring cheat sheet', es: 'Chuleta de anclajes' }) });

Kit · core, fonts, viewer, images: the same in every recipe · 270 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 · 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

#Add a 3 mm bleed and crop marks

Three millimetres of BLEED switch on the cut lines and push the sky and the foot band 3 mm into the bleed they hang from, while INSET keeps the text on the margin; the Sun, the Moon and the corona hang from the page, and because 1.4.1 does not clip design elements to the bleed they run on across the white margin to the sheet’s edge.

-const BLEED = 0; // mm; 3 for the printer, which switches on page.cutLines below
+const BLEED = 3; // mm; 3 for the printer, which switches on page.cutLines below

#Raise the horizon

Taking 20 mm off SKY lifts the sky’s edge, and with it the standfirst, the title, the kicker and the twelve texts of the programme, while the fine print starts on a higher grid line; the Sun hangs from the page, so the second change lifts it the same 20 mm, or the ‘w’ of Shadow would touch the crescent.

-const SKY = 272; // mm from the trim's top edge to the horizon, the sky's lower edge
+const SKY = 252; // mm from the trim's top edge to the horizon, the sky's lower edge
-  disc('sun', 'sun', at('page', 'top-right', 30, 25)), // 30 mm of it past the right edge
+  disc('sun', 'sun', at('page', 'top-right', 30, 5)), // 30 mm of it past the right edge

Pitfalls

Pitfall

Header and footer elements paint over text

Header and footer elements are painted over the page and the text area does not make room for them. Keep them within the margins, which are what reserve their space. Running heads and folios →

Pitfall

Attribute values: no { or }; single-quote a value with "

An attribute value ends at the closing brace, so it cannot hold { or }. A value that contains a double quote goes in single quotes; a dollar sign is fine. Heading attributes →

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 design text's lineHeight is a multiple, never a dimension

In a design slot, a text element's lineHeight multiplies its font size (lineHeight: 1.05). In postext 1.4.1 a dimension such as pt(15) is not rejected: the opener's height measures as NaN, the room it reserves, minHeight included, is dropped without a warning and the text runs under the title. Text, rules and boxes in page designs →

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

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 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 →

Sandbox check · designCyclicAnchor

Cyclic anchor reference

Why. Design elements anchor to each other in a loop, so none of them can be placed.

Fix. Anchor one element of the chain to the container, the page or the bleed. Docs →

Sandbox check · designDanglingAnchor

Dangling anchor reference

Why. A design element anchors to an #id that no element in the slot has.

Fix. Correct the id, or add the element it refers to. Docs →

In a pen, 1.4.1 reports neither a cyclic nor a dangling anchor. The Sandbox’s Checks panel lists them in the header, the footer, part pages and heading levels, but not in heading styles such as guides. An element pinned to an #id that does not exist is placed against the container: an element edge such as 'below' falls back to the container’s top-left corner, offset included, and a container edge such as 'top-right' to that corner. In a loop, one element falls back the same way and the others chain off it.
'align-left' and 'align-top' land on the same point in 1.4.1: both put the element’s top-left corner on its anchor’s top-left corner.
A border is painted centred on the box’s edge, so each 1 pt pink frame reaches 0.5 pt outside the box it traces, although the configuration docs say strokes are painted inside.

Credits

Recipe: Ignacio Ferro
Text: Original prose, CC BY 4.0
Fonts: Funnel Display (SIL OFL 1.1) · Funnel Sans (SIL OFL 1.1) · Martian Mono (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 · Pin two elements to the sheet and hang the rest from them

#2 · Hang the Moon and the corona from the Sun

#3 · Chain the evenings into columns

#4 · Put the band in the footer, on every page

#5 · Draw the construction lines from the same config

#The whole recipe

#Variations

#Add a 3 mm bleed and crop marks

#Raise the horizon

#Pitfalls

#Credits

More from the Cookbook

Business letter to DIN 5008

Certificate with a guilloche border

Magazine cover and sectioned contents

What you'll build

The short answer

Ingredients

Method

The whole recipe

Variations

Pitfalls

Credits