Un romanzo bunko in verticale, con furigana

// ═══ Postext Cookbook · Nº 117 · A bunko novel set vertically, with furigana ════════
// https://postext.dev/en/cookbook/bunko-novel-furigana
// Code: MIT · Text: 夏目漱石『夢十夜』, Aozora Bunko 799 (public domain) · Pictures: none
// Fonts: Shippori Mincho B1, Noto Sans JP (SIL OFL 1.1) · Needs postext ≥ 1.28.0
import {
  buildDocument, withLoadedFonts, renderPageToCanvas, loadVerticalAlternates,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'en'; // @lang: the language of the colophon; the novel is Japanese in both
const RECIPE = 'bunko-novel-furigana';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: sumi ink on a cream bunko stock, one vermilion
const palette = {
  ink: '#1f1b18', // the text: a warm sumi black
  vermilion: '#a8392b', // 朱: the frame of the title page
  muted: '#6b635b', // the hashira and the folios
  paper: '#fbf7ee', // bunko paper is cream, not white
};
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: 'defaults', value: { hex: palette.vermilion, model: 'hex' } },
];
// #endregion
const [MINCHO, GOTHIC] = ['Shippori Mincho B1', 'Noto Sans JP'];
const [BODY, LEAD, CHARS, LINES] = [9, 15.75, 38, 15]; // pt, pt: 38字 × 15行 at 1.75 em
const lines = (n) => pt(n * LEAD); // n lines across the page
const PT = 25.4 / 72; // mm in a point

// #region answer: a bunko page, 38 characters down 15 lines, bound on the right
// 'vertical-rl' sets each line top to bottom and the lines from right to left; with the
// binding left to 'auto' the book opens from the right, so page 1 is a left-hand page and
// the spreads read [3 | 2]. locale 'ja' gives the cjk settings Japan's values: they are
// written out below so you can see them, and leaving them out sets the same page.
const page = {
  sizePreset: 'custom', width: mm(105), height: mm(148), dpi: 200, // 文庫判 A6
  backgroundColor: col('paper'),
  // 天 above 地; left is the spine side (the right edge of a left-hand page). The grid
  // grows the margins of each pair alike, so the head stays deeper than the foot.
  margins: { top: mm(15), bottom: mm(11), left: mm(9), right: mm(12), mirror: true },
  pageNumbering: { format: 'japanese-informal' }, // folios 一, 二 … 十, 十一
};
const layout = { layoutType: 'single', writingMode: 'vertical-rl' };
const cjk = {
  grid: { enabled: true, charsPerLine: CHARS, linesPerPage: LINES },
  lineBreak: 'ja-very-strict', // 行頭禁則: no 、。」ー or small kana at the head of a line
  hangingPunctuation: 'allow', // ぶら下げ: a 、。 that would open a line hangs below the last
  paragraphStartBracket: 'half', // ③: a 「 that opens a paragraph fills the indent cell
  ruby: { align: 'jis', overhang: 'kana' }, // JIS 1:2:1, a reading may run onto kana only
};
// #endregion

// #region nights: each night's title takes three body lines (3行取り), five characters down
// lineSpan sets the heading in a band of three body lines, its characters centred in it, so
// the text after it stands on the grid's lines. Aozora marks the titles ５字下げ (中見出し);
// indent counts body characters, whatever the heading's own size.
const night = {
  level: 1, fontFamily: MINCHO, fontWeight: 600, fontSize: pt(12.5),
  lineSpan: 3, indent: em(5), // JLReq §4.1.3
  breakBefore: { enabled: false }, // the nights run on
};
// #endregion

// #region hashira: the title down the fore-edge of left-hand pages, kanji folios below
// anchor 'outer' is the fore-edge: the left margin of an odd page, the right of an even one
// in a book bound on the right. The 柱 starts two characters below the head of the text.
const foreEdge = (id, content, parity, edge, y, pages) => ({
  kind: 'text', id, content, parity, pages, writingMode: 'vertical-rl',
  fontFamily: GOTHIC, fontSize: pt(7), letterSpacing: pt(1), color: col('muted'),
  overflow: 'clip', placement: { anchor: { to: 'outer', edge }, offset: { y: em(y) } },
});
const header = { elements: [
  foreEdge('hashira', '{title}', 'odd', 'top', 2, 'body'), // never on the opening page
  foreEdge('folio', '{pageNumber}', 'all', 'bottom', -2, 'all'),
] };
const none = { elements: [] };
// #endregion

// #region title-page: the 扉, a vermilion frame round the title and the author
// A design on a vertical page is laid out in the flow frame: x runs down the page and y
// across it, leftwards from the right edge. Anchored to the page (the trim), the frame and
// the title stand on the page's axis, 52.5 mm in, whichever side the spine is on.
const at = (down, across) => ({ anchor: { to: 'page', edge: 'top-left' },
  offset: { x: mm(down), y: mm(across) } });
const AXIS = 105 / 2; // mm
const TITLE = 28 * PT; // mm: 夢十夜 in 28 pt, three characters and two 8 pt gaps down
const frame = { kind: 'box', id: 'frame', placement: { ...at(30, AXIS - 23),
  size: { width: mm(88), height: mm(46) } }, // 88 mm down, 46 mm across
  style: { borderColor: col('vermilion'), borderWidth: pt(0.75) } };
const titlePage = {
  id: 'title', numbered: false, toc: false, span: 'page', header: none, footer: { elements: [
    // The colophon across the foot, in the edition's language: each \n in the attribute
    // starts a line; the box hangs from the foot of the page, centred.
    // Noto Sans JP: Shippori Mincho B1 has no ō or ū for the rōmaji.
    { kind: 'text', id: 'colophon', content: '{attr.colophon}', fontFamily: GOTHIC,
      fontSize: pt(5.25), lineHeight: 1.45, color: col('muted'), overflow: 'wrap',
      align: 'center', placement: { anchor: { to: 'page', edge: 'bottom' },
        offset: { y: mm(-4) }, size: { width: mm(84) } } }] },
  breakBefore: { enabled: true, parity: 'any' },
  advancedDesign: { enabled: true, minHeight: lines(LINES), slot: { elements: [
    frame,
    { kind: 'text', id: 'book', content: '{titleText}', fontFamily: MINCHO, fontWeight: 800,
      fontSize: pt(28), lineHeight: 1, letterSpacing: pt(8), color: col('ink'),
      placement: at(44, AXIS - TITLE / 2) },
    { kind: 'text', id: 'author', content: '{author}', fontFamily: MINCHO, fontSize: pt(11),
      letterSpacing: pt(4), color: col('ink'), placement: at(92, AXIS + TITLE / 2 + 4) },
  ] } },
};
// #endregion

const config = () => ({
  locale: 'ja', // written out, never LANG (gotcha: ja-locale-tag)
  colorPalette,
  page,
  layout,
  cjk,
  bodyText: {
    fontFamily: MINCHO, fontSize: pt(BODY), lineHeight: pt(LEAD), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
    textAlign: 'justify', firstLineIndent: em(1), indentAfterHeading: true, // 一字下げ
  },
  headings: { fontFamily: MINCHO, color: col('ink'), levels: [night] },
  headingStyles: [titlePage],
  header,
  footer: none,
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
Esempio Markdown · 77 righe · content.en.md
title: "夢十夜"
author: "夏目漱石"
---

# 夢十夜 {style="title" colophon="Natsume Sōseki, 夢十夜 (Ten Nights of Dreams, 1908), nights one and two.\nText: Aozora Bunko 799, public domain.\nSet in Shippori Mincho B1 and Noto Sans JP (SIL OFL)."}

# 第一夜

こんな夢を見た。

腕組をして枕元に{坐|すわ}っていると、{仰向|あおむき}に寝た女が、静かな声でもう死にますと云う。女は長い髪を枕に敷いて、{輪郭|りんかく}の{柔|やわ}らかな{瓜実|うりざね}{顔|がお}をその中に横たえている。真白な頬の底に温かい血の色がほどよく差して、{唇|くちびる}の色は無論赤い。とうてい死にそうには見えない。しかし女は静かな声で、もう死にますと{判然|はっきり}云った。自分も{確|たしか}にこれは死ぬなと思った。そこで、そうかね、もう死ぬのかね、と上から{覗|のぞ}き込むようにして聞いて見た。死にますとも、と云いながら、女はぱっちりと眼を{開|あ}けた。大きな{潤|うるおい}のある眼で、長い{睫|まつげ}に包まれた中は、ただ一面に真黒であった。その真黒な{眸|ひとみ}の奥に、自分の姿が{鮮|あざやか}に浮かんでいる。

自分は{透|す}き{徹|とお}るほど深く見えるこの黒眼の{色沢|つや}を眺めて、これでも死ぬのかと思った。それで、ねんごろに枕の{傍|そば}へ口を付けて、死ぬんじゃなかろうね、大丈夫だろうね、とまた聞き返した。すると女は黒い眼を眠そうに{睜|みはっ}たまま、やっぱり静かな声で、でも、死ぬんですもの、仕方がないわと云った。

じゃ、{私|わたし}の顔が見えるかいと{一心|いっしん}に聞くと、見えるかいって、そら、そこに、写ってるじゃありませんかと、にこりと笑って見せた。自分は黙って、顔を枕から離した。腕組をしながら、どうしても死ぬのかなと思った。

しばらくして、女がまたこう云った。

「死んだら、{埋|う}めて下さい。大きな真珠貝で穴を掘って。そうして天から落ちて来る星の{破片|かけ}を{墓標|はかじるし}に置いて下さい。そうして墓の傍に待っていて下さい。また{逢|あ}いに来ますから」

自分は、いつ逢いに来るかねと聞いた。

「日が出るでしょう。それから日が沈むでしょう。それからまた出るでしょう、そうしてまた沈むでしょう。――赤い日が東から西へ、東から西へと落ちて行くうちに、――あなた、待っていられますか」

自分は黙って{首肯|うなず}いた。女は静かな調子を一段張り上げて、

「百年待っていて下さい」と思い切った声で云った。

「百年、私の墓の{傍|そば}に坐って待っていて下さい。きっと逢いに来ますから」

自分はただ待っていると答えた。すると、黒い{眸|ひとみ}のなかに{鮮|あざやか}に見えた自分の姿が、ぼうっと{崩|くず}れて来た。静かな水が動いて写る影を乱したように、流れ出したと思ったら、女の眼がぱちりと閉じた。長い{睫|まつげ}の間から涙が頬へ垂れた。――もう死んでいた。

自分はそれから庭へ下りて、真珠貝で穴を掘った。真珠貝は大きな{滑|なめら}かな{縁|ふち}の{鋭|する}どい貝であった。土をすくうたびに、貝の裏に月の光が差してきらきらした。{湿|しめ}った土の{匂|におい}もした。穴はしばらくして掘れた。女をその中に入れた。そうして柔らかい土を、上からそっと掛けた。掛けるたびに真珠貝の裏に月の光が差した。

それから星の{破片|かけ}の落ちたのを拾って来て、かろく土の上へ乗せた。星の破片は丸かった。長い間大空を落ちている{間|ま}に、{角|かど}が取れて{滑|なめら}かになったんだろうと思った。{抱|だ}き{上|あ}げて土の上へ置くうちに、自分の胸と手が少し暖くなった。

自分は{苔|こけ}の上に坐った。これから百年の間こうして待っているんだなと考えながら、腕組をして、丸い{墓石|はかいし}を眺めていた。そのうちに、女の云った通り日が東から出た。大きな赤い日であった。それがまた女の云った通り、やがて西へ落ちた。赤いまんまでのっと落ちて行った。一つと自分は{勘定|かんじょう}した。

しばらくするとまた{唐紅|からくれない}の{天道|てんとう}がのそりと{上|のぼ}って来た。そうして黙って沈んでしまった。二つとまた勘定した。

自分はこう云う風に一つ二つと勘定して行くうちに、赤い日をいくつ見たか分らない。勘定しても、勘定しても、しつくせないほど赤い日が頭の上を通り越して行った。それでも百年がまだ来ない。しまいには、{苔|こけ}の{生|は}えた丸い石を眺めて、自分は女に{欺|だま}されたのではなかろうかと思い出した。

すると石の下から{斜|はす}に自分の方へ向いて青い{茎|くき}が伸びて来た。見る間に長くなってちょうど自分の胸のあたりまで来て留まった。と思うと、すらりと{揺|ゆら}ぐ{茎|くき}の{頂|いただき}に、心持首を{傾|かたぶ}けていた細長い一輪の{蕾|つぼみ}が、ふっくらと{弁|はなびら}を開いた。真白な{百合|ゆり}が鼻の先で骨に{徹|こた}えるほど匂った。そこへ{遥|はるか}の上から、ぽたりと{露|つゆ}が落ちたので、花は自分の重みでふらふらと動いた。自分は首を前へ出して冷たい露の{滴|したた}る、白い{花弁|はなびら}に{接吻|せっぷん}した。自分が百合から顔を離す{拍子|ひょうし}に思わず、遠い空を見たら、{暁|あかつき}の星がたった一つ{瞬|またた}いていた。

「百年はもう来ていたんだな」とこの時始めて気がついた。

# 第二夜

こんな夢を見た。

{和尚|おしょう}の室を{退|さ}がって、{廊下|ろうか}{伝|づた}いに自分の部屋へ帰ると{行灯|あんどう}がぼんやり{点|とも}っている。{片膝|かたひざ}を{座蒲団|ざぶとん}の上に突いて、灯心を{掻|か}き立てたとき、花のような{丁子|ちょうじ}がぱたりと朱塗の台に落ちた。同時に部屋がぱっと明かるくなった。

{襖|ふすま}の{画|え}は{蕪村|ぶそん}の筆である。黒い柳を濃く薄く、{遠近|おちこち}とかいて、{寒|さ}むそうな漁夫が{笠|かさ}を{傾|かたぶ}けて土手の上を通る。{床|とこ}には{海中文殊|かいちゅうもんじゅ}の{軸|じく}が{懸|かか}っている。{焚|た}き残した線香が暗い方でいまだに{臭|にお}っている。広い寺だから{森閑|しんかん}として、{人気|ひとけ}がない。黒い{天井|てんじょう}に差す{丸行灯|まるあんどう}の丸い影が、{仰向|あおむ}く{途端|とたん}に生きてるように見えた。

{立膝|たてひざ}をしたまま、左の手で{座蒲団|ざぶとん}を{捲|めく}って、右を差し込んで見ると、思った所に、ちゃんとあった。あれば安心だから、蒲団をもとのごとく{直|なお}して、その上にどっかり{坐|すわ}った。

お前は{侍|さむらい}である。侍なら悟れぬはずはなかろうと{和尚|おしょう}が云った。そういつまでも悟れぬところをもって見ると、御前は侍ではあるまいと言った。人間の{屑|くず}じゃと言った。ははあ怒ったなと云って笑った。{口惜|くや}しければ悟った証拠を持って来いと云ってぷいと{向|むこう}をむいた。{怪|け}しからん。

隣の広間の床に{据|す}えてある置時計が次の{刻|とき}を打つまでには、きっと悟って見せる。悟った上で、今夜また{入室|にゅうしつ}する。そうして和尚の首と悟りと{引替|ひきかえ}にしてやる。悟らなければ、和尚の命が取れない。どうしても悟らなければならない。自分は侍である。

もし悟れなければ{自刃|じじん}する。侍が{辱|はずか}しめられて、生きている訳には行かない。{綺麗|きれい}に死んでしまう。

こう考えた時、自分の手はまた思わず{布団|ふとん}の下へ{這入|はい}った。そうして{朱鞘|しゅざや}の短刀を{引|ひ}き{摺|ず}り出した。ぐっと{束|つか}を握って、赤い鞘を向へ払ったら、冷たい{刃|は}が一度に暗い部屋で光った。{凄|すご}いものが手元から、すうすうと逃げて行くように思われる。そうして、ことごとく{切先|きっさき}へ集まって、{殺気|さっき}を一点に{籠|こ}めている。自分はこの鋭い刃が、無念にも針の頭のように{縮|ちぢ}められて、{九寸|くすん}{五分|ごぶ}の先へ来てやむをえず{尖|とが}ってるのを見て、たちまちぐさりとやりたくなった。{身体|からだ}の血が右の手首の方へ流れて来て、握っている束がにちゃにちゃする。{唇|くちびる}が{顫|ふる}えた。

短刀を鞘へ収めて右脇へ引きつけておいて、それから{全伽|ぜんが}を組んだ。――{趙州|じょうしゅう}曰く{無|む}と。無とは何だ。{糞坊主|くそぼうず}めとはがみをした。

奥歯を強く{咬|か}み{締|し}めたので、鼻から熱い息が荒く出る。こめかみが釣って痛い。眼は普通の倍も大きく開けてやった。

{懸物|かけもの}が見える。行灯が見える。{畳|たたみ}が見える。和尚の{薬缶頭|やかんあたま}がありありと見える。{鰐口|わにぐち}を{開|あ}いて{嘲笑|あざわら}った声まで聞える。{怪|け}しからん坊主だ。どうしてもあの薬缶を首にしなくてはならん。悟ってやる。無だ、無だと舌の根で念じた。無だと云うのにやっぱり線香の{香|におい}がした。何だ線香のくせに。

自分はいきなり{拳骨|げんこつ}を固めて自分の頭をいやと云うほど{擲|なぐ}った。そうして奥歯をぎりぎりと{噛|か}んだ。{両腋|りょうわき}から汗が出る。背中が棒のようになった。{膝|ひざ}の{接目|つぎめ}が急に痛くなった。膝が折れたってどうあるものかと思った。けれども痛い。苦しい。{無|む}はなかなか出て来ない。出て来ると思うとすぐ痛くなる。腹が立つ。無念になる。非常に{口惜|くや}しくなる。涙がほろほろ出る。ひと{思|おもい}に身を{巨巌|おおいわ}の上にぶつけて、骨も肉もめちゃめちゃに{砕|くだ}いてしまいたくなる。

それでも我慢してじっと坐っていた。{堪|た}えがたいほど切ないものを胸に{盛|い}れて忍んでいた。その切ないものが{身体|からだ}中の筋肉を下から持上げて、毛穴から外へ吹き出よう吹き出ようと{焦|あせ}るけれども、どこも一面に{塞|ふさ}がって、まるで出口がないような残刻極まる状態であった。

そのうちに頭が変になった。{行灯|あんどう}も{蕪村|ぶそん}の{画|え}も、畳も、{違棚|ちがいだな}も有って無いような、無くって有るように見えた。と云って{無|む}はちっとも{現前|げんぜん}しない。ただ{好加減|いいかげん}に坐っていたようである。ところへ{忽然|こつぜん}隣座敷の時計がチーンと鳴り始めた。

はっと思った。右の手をすぐ短刀にかけた。時計が二つ目をチーンと打った。
`; // content.<lang>.md: the same Japanese text in both

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
const FONTS = {
  'Shippori Mincho B1': ['400', '600', '800'], // the text and furigana; 一; the title
  'Noto Sans JP': ['400'], // the hashira, the folios and the colophon
};

// ─── 4 · Build & show ───────────────────────────────────────────────────────
// #region voices: each face loads the files that hold the characters it sets
// Fontsource cuts a Japanese face into about 120 files; loadCjkFonts fetches the ones the
// text touches (gotcha: cjk-fonts-slices). vertical: true loads the face's vertical forms
// for the canvas: 、。「」ー and small kana such as っ stand differently down a line.
const title = markdown.match(/^title: "(.*)"$/m)[1];
const author = markdown.match(/^author: "(.*)"$/m)[1];
const heads = markdown.match(/^# [^{\n]*/gm).join('');
await loadFonts(FONTS, markdown); // the Latin files: the colophon, with ō and ū
await loadCjkFonts({ [MINCHO]: ['400'] }, markdown, { vertical: true });
await loadCjkFonts({ [MINCHO]: ['600', '800'] }, `${heads}${title}${author}`);
await loadCjkFonts({ [GOTHIC]: ['400'] }, `${title}一二三四五六七八九十`, { vertical: true });
// #endregion
const doc = await withLoadedFonts(() => buildDocument({ markdown }, config()),
  { ...kitFonts(FONTS), text: markdown });
showBook(doc, { title: t({ en: 'A bunko novel set vertically, with furigana',
  es: 'Una novela en formato bunko, en vertical y con furigana' }) });
offerPdf(() => renderToPdf(doc, { fontProvider: cjkPdfProvider }), `${RECIPE}.pdf`);

Kit · core, fonts, viewer, pdf, cjk: uguale in ogni ricetta · 458 righe
// ─── 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 v3 ── the same in every recipe · postext.dev/cookbook
// Postext loads the faces a config asks for before layout (prepareFonts,
// buildDocumentWithFonts) and asks the kit for the files: Fontsource's, the
// files the PDF embeds too.

/** The options of buildDocumentWithFonts / prepareFonts / withLoadedFonts:
 *  the Fontsource resolver, and the faces of FONTS loaded with the ones the
 *  config names. FONTS = { 'Family Name': ['400', '400i', '700'] }. */
function kitFonts(FONTS = {}) {
  const faces = Object.entries(FONTS).flatMap(([family, specs]) => specs.map((spec) =>
    ({ family, weight: parseInt(spec, 10), style: spec.endsWith('i') ? 'italic' : 'normal' })));
  return { resolve: fontsourceResolver, faces };
}

/** A face's Fontsource files, in a fixed order: latin, then latin-ext and greek
 *  when `text` needs them and the family ships them (kitSubsetsFor), each with
 *  its unicode-range. Null for a weight or slant Fontsource does not ship. */
async function fontsourceResolver(family, weight, style, { text = '' } = {}) {
  const id = fontsourceId(family);
  const meta = await fontsourceMeta(family);
  if (meta && !(meta.weights.includes(weight) && meta.styles.includes(style))) return null;
  kitStatus('Loading fonts…');
  const at = await fontsourceAt(id);
  return ['latin', ...kitSubsetsFor(text, meta)].map((subset) => ({
    source: `${at}files/${id}-${subset}-${weight}-${style}.woff2`,
    unicodeRange: kitRanges()[subset],
  }));
}

/** The unicode-range of each Fontsource file the kit loads (a function: the
 *  kit is inlined after the pen's code, which runs before a const would be set). */
function kitRanges() {
  return {
    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',
    greek: 'U+0370-03FF',
  };
}

/** For the cjk, arabic and comics blocks, which add their own files: the
 *  faces of `faces` = { 'Family Name': ['400', '400i', '700'] }. `text` is the sample:
 *  č ł † α χ also load latin-ext and greek files (kitSubsetsFor). With
 *  `optional`, a face Fontsource does not ship is skipped instead of failing.
 *  The files are added once all have loaded, in the order asked (latin, then
 *  latin-ext, then greek), whatever order they arrive in: the last one added
 *  wins a character two files hold. Resolves to the number of faces added. */
async function loadFonts(faces, text = '', { optional = false } = {}) {
  kitStatus('Loading fonts…');
  const ranges = kitRanges();
  const jobs = [];
  for (const [family, specs] of Object.entries(faces)) {
    const id = fontsourceId(family);
    const todo = [...new Set(specs)].map((spec) => [parseInt(spec, 10), spec.endsWith('i') ? 'italic' : 'normal'])
      .filter(([weight, style]) => !hasFace(family, weight, style)); // before any await
    const at = fontsourceAt(id);
    const meta = optional || /[^\0-ÿ]/u.test(text) ? await fontsourceMeta(family) : null;
    const subsets = ['latin', ...kitSubsetsFor(text, meta)];
    for (const [weight, style] of todo) {
      if (optional && !(meta?.weights.includes(weight) && meta.styles.includes(style))) continue;
      for (const subset of subsets) {
        const url = `${await at}files/${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().catch(() => {
          if (subset === 'latin' && !optional) throw new Error(`Fontsource has no ${family} ${weight} ${style}`);
        }));
      }
    }
  }
  const ready = await Promise.all(jobs).catch((error) => { kitFail(error); throw error; });
  return ready.filter((face) => face && document.fonts.add(face)).length;
}

/** A loaded FontFace covers this family, weight and style (fonts.check() would
 *  also say yes 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;
}

/** The files beyond latin `text` needs that `meta`'s family ships. */
function kitSubsetsFor(text, meta) {
  return [[/[Ā-˿ᴀ-ᶿḀ-ỿ†ℓⱠ-Ɀ꜠-ꟿ]/u, 'latin-ext'], [/[Ͱ-Ͽ]/u, 'greek']]
    .filter(([re, x]) => re.test(text) && meta?.subsets?.includes(x)).map(([, x]) => x);
}

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

/** A package's folder at the one version @5 names now (#766). */
function fontsourceAt(id, u = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@`) {
  return (fontsourceAt.c ??= {})[id] ??= fetch(u + '5/package.json').then((r) => r.json())
    .then((p) => p.version || 5, () => 5).then((v) => `${u}${v}/`);
}

/** The family's Fontsource metadata (weights, styles, subsets), 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 v2 ── the same in every recipe · postext.dev/cookbook
/** The pages as spreads on a dark desk, page 1 alone, then verso | recto,
 *  each painted when it scrolls near. Other options go to renderPageToCanvas. */
function showPages(docs, { title, width = 460, ...render } = {}) {
  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, { ...render, scale: (width * density) / page.width });
    }
  }, { rootMargin: '800px' });
  showPages.painter = painter;
  root.replaceChildren(...spreads.map((pair) => {
    const spread = document.createElement('div');
    spread.className = 'pt-spread';
    for (const p of pair) {
      const figure = document.createElement('figure');
      if (p) {
        const label = p.page.pageLabel || String(p.n + 1);
        const canvas = document.createElement('canvas');
        canvas.postext = p;
        canvas.style.aspectRatio = `${p.page.width} / ${p.page.height}`;
        canvas.setAttribute('role', 'img');
        canvas.setAttribute('aria-label', `Page ${label}`);
        const folio = document.createElement('figcaption');
        folio.textContent = label;
        figure.append(canvas, folio);
        painter.observe(canvas);
      } else figure.className = 'pt-blank';
      spread.append(figure);
    }
    return spread;
  }));
  kitStatus(`${pages.length} ${pages.length === 1 ? 'page' : 'pages'}`);
  document.documentElement.dataset.postext = 'ready';
  return pages.length;
}

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

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

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

// ─── Kit · pdf v3 ── the same in every recipe that exports a PDF
/** The Fontsource files the screen used, as TrueType, with their range and
 *  place: the nearest weight the family ships, upright with no italic;
 *  latin, then what its letters need (kitSubsetsFor). */
async function fontsourceProvider(family, weight, style, request) {
  const id = fontsourceId(family);
  const meta = await fontsourceMeta(family);
  const weights = meta?.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && meta && !meta.styles.includes('italic') ? 'normal' : style;
  const text = String.fromCodePoint(...(request?.codePoints ?? []));
  const files = await Promise.all(['latin', ...kitSubsetsFor(text, meta)].map(async (subset, order) => {
    const res = await fetch(`${await fontsourceAt(id)}files/${id}-${subset}-${w}-${s}.woff2`);
    if (!res.ok) throw new Error(`Fontsource has no ${family} ${w} ${s} ${subset}`);
    return Object.assign(await decompressWoff2(new Uint8Array(await res.arrayBuffer())),
      { unicodeRange: kitRanges()[subset], order });
  }));
  return files.length === 1 ? files[0] : files;
}

/** A "Build the PDF" button; then "Open the PDF" (a new tab: CodePen's frame
 *  shows no PDFs) and a download link. */
function offerPdf(makePdf, filename) {
  viewer();
  const button = Object.assign(document.createElement('button'), { type: 'button', textContent: 'Build the PDF' });
  button.dataset.postextPdf = filename;
  button.addEventListener('click', async () => {
    button.disabled = true;
    button.textContent = 'Building the PDF…';
    try {
      const bytes = await makePdf();
      const url = URL.createObjectURL(new Blob([bytes], { type: 'application/pdf' }));
      const size = `${Math.max(1, Math.round(bytes.length / 1024))} KB`;
      button.replaceWith(
        Object.assign(document.createElement('a'), { href: url, target: '_blank', rel: 'noopener', textContent: 'Open the PDF ↗' }),
        Object.assign(document.createElement('a'), { href: url, download: filename, textContent: `Download ${filename} · ${size}` }));
    } catch (error) {
      button.disabled = false;
      button.textContent = 'Build the PDF';
      kitFail(error);
    }
  });
  document.getElementById('pt-actions').append(button);
}

// ─── Kit · cjk v2 ── Chinese, Japanese and Korean books · postext.dev/cookbook
// Fontsource ships a CJK family as about a hundred files per weight, each
// declared in its stylesheet with the unicode-range it covers. The screen
// loads the files the sample touches; the PDF gets the same files for the
// characters its pages set in each face, and embeds each as a subset.
// A book bound on the right (vertical text) is shown with its spreads
// mirrored: page 1 alone on the left of the spine, then [3 | 2].

/** The files of a Fontsource face, read from its stylesheet: { url, range,
 *  ranges }, the last declared first (the order the browser tries them in). */
function cjkSlices(family, weight, style) {
  cjkSlices.cache ??= new Map();
  const id = fontsourceId(family);
  const css = `${id}/${weight}${style === 'italic' ? '-italic' : ''}.css`;
  if (!cjkSlices.cache.has(css)) {
    let at;
    cjkSlices.cache.set(css, fontsourceAt(id).then((a) => fetch(at = a + css.slice(id.length + 1)))
      .then((res) => {
        if (!res.ok) throw new Error(`Fontsource has no ${family} ${weight} ${style} (${res.status})`);
        return res.text();
      })
      .then((text) => [...text.matchAll(/@font-face\s*{([^}]*)}/g)].map(([, rule]) => {
        const range = /unicode-range:\s*([^;]+);/.exec(rule)?.[1].trim() ?? 'U+0-10FFFF';
        const ranges = range.split(',').map((part) => {
          const [lo, hi = lo] = part.trim().slice(2).split('-');
          return [parseInt(lo, 16), parseInt(hi, 16)];
        });
        return { url: new URL(/url\(([^)]+?\.woff2)\)/.exec(rule)[1], at).href, range, ranges };
      }).reverse()));
  }
  return cjkSlices.cache.get(css);
}

/** The file of `slices` the screen sets code point `cp` in, if any: the
 *  last one loadCjkFonts adds whose range holds it. A numbered file that
 *  repeats a letter of latin is added after latin, and wins it. */
function cjkSliceFor(slices, cp) {
  const holds = (slice) => slice.ranges.some(([lo, hi]) => cp >= lo && cp <= hi);
  return slices.reduce((last, slice) => (holds(slice) ? slice : last), undefined);
}

/** Whether Fontsource serves `family` as a Chinese, Japanese or Korean
 *  family (its subsets name the script). Fails when the API does not
 *  answer: a CJK face taken for a Latin one would paint in a system face. */
async function isCjkFamily(family) {
  const meta = await fontsourceMeta(family);
  if (!meta) throw new Error(`api.fontsource.org did not describe ${family}: reload to try again`);
  return !!meta.subsets?.some((subset) => /^(chinese|japanese|korean)/.test(subset));
}

/** faces = { 'Noto Serif TC': ['400', '700'] }, as for loadFonts: the
 *  whole FONTS object may be passed, its other families are left to
 *  loadFonts. Adds one FontFace per file of each CJK face with its
 *  unicodeRange, then loads the files `text` touches. `text` is what the
 *  faces set: the sample for the text face; a book in several voices calls
 *  it once per voice (loadCjkFonts({ 'LXGW WenKai TC': ['400'] }, quotes)),
 *  so the heading and quotation faces fetch and check only their own
 *  characters. Fails when a character of `text` is in no file of a face.
 *  List every weight the pages use: a weight left to the engine's later round
 *  gets the latin file only. With { vertical: true } it also loads each
 *  family's vertical forms (brackets, quotes, pause marks) for the canvas,
 *  which needs loadVerticalAlternates imported from postext. Resolves to
 *  the number of files loaded. */
async function loadCjkFonts(faces, text, { vertical = false } = {}) {
  kitStatus('Loading fonts…');
  let loaded = 0;
  try {
    if (vertical && typeof loadVerticalAlternates !== 'function') {
      throw new Error('loadCjkFonts(…, { vertical: true }) needs loadVerticalAlternates imported from postext');
    }
    for (const [family, specs] of Object.entries(faces)) {
      if (!(await isCjkFamily(family))) continue;
      const twin = [];
      for (const spec of new Set(specs)) {
        const weight = parseInt(spec, 10);
        const style = spec.endsWith('i') ? 'italic' : 'normal';
        const slices = await cjkSlices(family, weight, style);
        const missing = [...new Set(text)].filter((ch) => /\S/.test(ch) && !cjkSliceFor(slices, ch.codePointAt(0)));
        if (missing.length) {
          throw new Error(`${family} ${spec} has no file for ${missing.slice(0, 12).join(' ')}: `
            + `give each face the text it sets (loadCjkFonts({ '${family}': ['${spec}'] }, text))`);
        }
        for (const slice of slices) {
          document.fonts.add(new FontFace(family, `url(${slice.url}) format('woff2')`,
            { weight: String(weight), style, unicodeRange: slice.range }));
          twin.push({ source: slice.url, weight: String(weight), style, unicodeRange: slice.range });
        }
        const font = `${style === 'italic' ? 'italic ' : ''}${weight} 16px "${family}"`;
        loaded += (await document.fonts.load(font, text)).length;
        if (!document.fonts.check(font, text)) throw new Error(`${family} ${spec} did not load for the sample`);
      }
      // The same files under a twin name with the `vert` feature on: the
      // canvas paints the punctuation of vertical lines with it.
      if (vertical && twin.length) await loadVerticalAlternates(family, twin);
    }
  } catch (error) {
    kitFail(error);
    throw error;
  }
  return loaded;
}

/** The PDF font provider for recipes with CJK faces: a family whose
 *  Fontsource subsets are Chinese, Japanese or Korean gets the files the
 *  screen set its pages' characters in (`request.codePoints`), each marked
 *  with its unicode-range and its place in the order loadCjkFonts added
 *  them: postext-pdf sets a character two files hold in the one added
 *  last, as the browser does. Any other family gets the latin file
 *  fontsourceProvider fetches (the "pdf" block) and, when the face sets
 *  letters only latin-ext has, that file too. */
async function cjkPdfProvider(family, weight, style, request) {
  if (!(await isCjkFamily(family))) return cjkLatinPdfFiles(family, weight, style, request);
  const meta = await fontsourceMeta(family);
  const weights = meta.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && !meta.styles.includes('italic') ? 'normal' : style;
  const slices = await cjkSlices(family, w, s);
  const picked = new Set();
  for (const cp of request?.codePoints ?? []) {
    const slice = cjkSliceFor(slices, cp);
    if (slice) picked.add(slice);
  }
  if (!picked.size) picked.add(slices[0]);
  return Promise.all(slices.map(async (slice, order) => {
    if (!picked.has(slice)) return null;
    const res = await fetch(slice.url);
    if (!res.ok) throw new Error(`Fontsource file ${slice.url} (${res.status})`);
    const bytes = await decompressWoff2(new Uint8Array(await res.arrayBuffer()));
    return Object.assign(bytes, { unicodeRange: slice.range, order });
  })).then((files) => files.filter(Boolean));
}

/** A Latin family set next to the CJK faces: its latin file, then its
 *  latin-ext file when the face sets letters only latin-ext has (ō ū in
 *  Hepburn rōmaji, ǎ in pinyin), the file loadFonts adds on screen for
 *  them, each marked with its unicode-range and its place in that order:
 *  the PDF sets a character in the file the browser took it from. A face
 *  Fontsource ships without latin-ext, or whose file does not come, gets
 *  latin alone, and the PDF names the letters it lacks. */
async function cjkLatinPdfFiles(family, weight, style, request) {
  const meta = await fontsourceMeta(family);
  const beyond = [...(request?.codePoints ?? [])].some(cjkLatinExtOnly);
  if (!beyond || !meta?.subsets?.includes('latin-ext')) return fontsourceProvider(family, weight, style);
  const weights = meta.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && !meta.styles.includes('italic') ? 'normal' : style;
  const id = fontsourceId(family);
  const url = `${await fontsourceAt(id)}files/${id}-latin-ext-${w}-${s}.woff2`;
  const [latin, ext] = await Promise.all([fontsourceProvider(family, weight, style), fetch(url)
    .then(async (res) => (res.ok ? decompressWoff2(new Uint8Array(await res.arrayBuffer())) : null), () => null)]);
  const ranges = kitRanges();
  return ext ? [Object.assign(latin, { unicodeRange: ranges.latin, order: 0 }),
    Object.assign(ext, { unicodeRange: ranges['latin-ext'], order: 1 })] : latin;
}

/** Whether code point `cp` is in Fontsource's latin-ext file and not in
 *  its latin file: Latin Extended-A and -B, IPA, the spacing modifiers and
 *  Latin Extended Additional (loadFonts's test for latin-ext), less the
 *  few latin holds too (ı Œ œ ʻ ʼ ˆ ˚ ˜). */
function cjkLatinExtOnly(cp) {
  if (!((cp >= 0x100 && cp <= 0x2ff) || (cp >= 0x1e00 && cp <= 0x1eff))) return false;
  return ![0x131, 0x152, 0x153, 0x2bb, 0x2bc, 0x2c6, 0x2da, 0x2dc].includes(cp);
}

/** showPages for a book bound on either edge. A right-bound book (the
 *  document says so: doc.binding is 'right' for page.binding 'right' and
 *  for vertical text) lies on the desk as it opens: page 1 alone on the
 *  left of the spine, then [3 | 2], the spine shade on each page's inner
 *  edge. `binding` ('left' | 'right') overrides the document's. */
function showBook(docs, { binding, ...options } = {}) {
  const count = showPages(docs, options);
  const right = (binding ?? [docs].flat()[0]?.binding) === 'right';
  if (!document.getElementById('pt-kit-cjk')) {
    // The pages keep direction ltr: a canvas draws text in the direction its
    // element inherits, and under rtl each run would end where the engine
    // starts it, its brackets mirrored.
    document.head.insertAdjacentHTML('beforeend', `<style id="pt-kit-cjk">
      .pt-spread[dir="rtl"] canvas { direction: ltr; }
      .pt-spread[dir="rtl"] 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); }
    </style>`);
  }
  // Each pair stays [verso, recto] in the page; right to left, the verso
  // sits on the right. Phones stack the pages in reading order either way.
  for (const spread of document.querySelectorAll('#pages > .pt-spread')) spread.dir = right ? 'rtl' : 'ltr';
  document.getElementById('pages').dataset.binding = right ? 'right' : 'left';
  return count;
}

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