write_typography.rs

//! Sets five short samples twice each — once as the font is read straight off
//! its `cmap`, once with one typographic feature turned on — so the difference
//! each feature makes can be seen side by side.
//!
//! The five are the ligatures a font offers, small capitals, old-style figures,
//! the forms the font draws for one language, and kerning. Nothing is on unless
//! it is asked for, so the two settings of a sample differ in exactly one
//! thing. The forms of one language are the font's `locl` feature read for
//! Serbian, the Cyrillic script and the `SRB ` language.
//!
//! The font here is Spectral, which offers all five.
//!
//! The closing lines are measured off the fonts themselves rather than written
//! down: how many glyphs the ligature sample takes each way, how much narrower
//! kerning draws its own, and how many of the face's glyphs no character leads
//! to. The first of those are drawn last, asked for by their number in the file
//! and centred on the width measured off them.
//!
//! A second page sets the ligature sample with ligatures and kerning on, then
//! with ligatures alone turned back off, draws the face's `fi` glyph by its
//! number, stated to stand for the two letters it joins, and sets three
//! fractions twice: the face's `frac` feature draws each figure before the
//! slash as a numerator and each after it as a denominator, by the glyphs
//! around it.
//!
//! The words are held in `Words`, once per language, and `HQF_PDF_LANG` picks
//! which set is drawn.
//!
//! Usage: `cargo run --example write_typography -- tmp/typography.pdf`
//!        `HQF_PDF_LANG=fr cargo run --example write_typography --
//! tmp/typographie.pdf`

use std::collections::BTreeSet;
use std::env;
use std::fs;
use std::path::{Path, PathBuf};

use hqf_pdf::content::Content;
use hqf_pdf::font::GlyphId;
use hqf_pdf::{Document, Font, FontHandle, Page, TextFlow};

#[path = "shared/out.rs"]
mod out;

#[path = "shared/licence.rs"]
mod licence;

#[path = "shared/language.rs"]
mod language;

#[path = "shared/failure.rs"]
mod failure;

use language::Language;

/// Where the committed fonts sit.
fn font_dir() -> PathBuf {
    Path::new(env!("CARGO_MANIFEST_DIR"))
        .join("tests")
        .join("fonts")
}

/// The words the page is written in, one set per language.
#[derive(Debug)]
struct Words {
    /// The line across the top of the page.
    title: &'static str,
    /// What the page shows, in two sentences.
    why: &'static str,
    /// The heading over each of the five samples.
    headings: [&'static str; 5],
    /// What each feature does, one line each.
    explanations: [&'static str; 5],
    /// The five samples, each set twice.
    samples: [&'static str; 5],
    /// What is written beside the setting with nothing turned on.
    off: &'static str,
    /// What is written beside the setting with the feature turned on.
    on: &'static str,
    /// The line about the ligature sample, cut where the two counts go into it.
    glyphs_before: &'static str,
    glyphs_between: &'static str,
    glyphs_after: &'static str,
    /// The line about the kerning sample, cut where the width goes into it.
    kerned_before: &'static str,
    kerned_after: &'static str,
    /// The line over the glyphs drawn by number, cut where the count of the
    /// face's glyphs, the count no character leads to and the count drawn go
    /// into it.
    numbered_before: &'static str,
    numbered_between: &'static str,
    numbered_then: &'static str,
    numbered_after: &'static str,
    /// The line at the head of the second page.
    back_title: &'static str,
    /// What the second page shows.
    back_why: &'static str,
    /// What is written beside the sample set with ligatures and kerning.
    both: &'static str,
    /// What is written beside it with ligatures turned back off.
    without: &'static str,
    /// What stands over the glyph drawn by its number.
    by_number: &'static str,
    /// The heading over the fraction sample.
    fraction_heading: &'static str,
    /// What the `frac` feature does, in one line.
    fraction_explanation: &'static str,
}

impl Words {
    /// The words the page is written in, in `language`.
    fn of(language: Language) -> &'static Self {
        language::pick(&WORDS, language)
    }

    /// The line about the ligature sample, with the two counts in it.
    fn glyph_line(&self, apart: usize, joined: usize) -> String {
        format!(
            "{}{apart}{}{joined}{}",
            self.glyphs_before, self.glyphs_between, self.glyphs_after
        )
    }

    /// The line about the kerning sample, with the width it saves in it.
    fn kerned_line(&self, saved: f64) -> String {
        format!("{}{saved:.1}{}", self.kerned_before, self.kerned_after)
    }

    /// The line over the glyphs drawn by number, with its three counts in it.
    fn numbered_line(&self, held: usize, unreached: usize, drawn: usize) -> String {
        format!(
            "{}{held}{}{unreached}{}{drawn}{}",
            self.numbered_before, self.numbered_between, self.numbered_then, self.numbered_after
        )
    }
}

/// The page in English.
const ENGLISH: Words = Words {
    title: "Five things a font knows about its own letters",
    why: "A font file carries more than one glyph per character. It says which \
          letters are drawn joined, which figures hang below the line, which \
          letters have a small capital of their own, which letters take another \
          form in one language, and how far apart each pair of glyphs should \
          stand.\n\
          None of it is used unless it is asked for, so a document written \
          before these settings existed comes out byte for byte as it did. Each \
          sample below is set twice, and only the setting differs.",
    headings: [
        "Ligatures",
        "Small capitals",
        "Old-style figures",
        "Local forms",
        "Kerning",
    ],
    explanations: [
        "Letters that meet are drawn as one glyph the font designer cut for them.",
        "Lowercase letters drawn as capitals no taller than an x.",
        "Figures that rise and fall around the x-height instead of standing at cap height.",
        "The same Cyrillic letters, in the forms the font draws for Serbian.",
        "Each pair of glyphs moved as far apart as the font asks.",
    ],
    samples: [
        "office filing affidavit",
        "reprinted quarterly",
        "1 234 567 890",
        "пут, град, беседа",
        "Wavy TAXI Today",
    ],
    off: "off",
    on: "on",
    glyphs_before: "The first sample takes ",
    glyphs_between: " glyphs as it stands and ",
    glyphs_after: " with the ligatures on: the pairs the font joins are one glyph each.",
    kerned_before: "The last sample is drawn ",
    kerned_after: " points narrower with kerning on, and it is measured that way \
                   too, so the line is as wide as it looks.",
    numbered_before: "Spectral holds ",
    numbered_between: " glyphs, and no character leads to ",
    numbered_then: " of them: the forms a feature or a language puts in a \
                    letter's place. The first ",
    numbered_after: ", asked for by their number in the file and centred on \
                     their measured width:",
    back_title: "One feature turned back off, one glyph by its number",
    back_why: "Ligatures and kerning are turned on together, then ligatures alone are turned back off: the letters come apart again, and the pairs stay kerned.",
    both: "both",
    without: "no liga",
    by_number: "The glyph the face names fi, asked for by its number and stated to stand for the two letters it joins, so that the text copies out as those two letters:",
    fraction_heading: "Fractions",
    fraction_explanation: "Figures on either side of a slash, set as a numerator and a denominator around a fraction bar.",
};

/// The page in French.
const FRENCH: Words = Words {
    title: "Cinq choses qu’une police sait de ses propres lettres",
    why: "Un fichier de police contient plus d’un glyphe par caractère. Il indique \
quelles lettres se lient, quels chiffres descendent sous la ligne, quelles \
lettres ont leur propre petite capitale, lesquelles changent de forme dans une \
langue donnée, et quel écart laisser entre chaque paire de glyphes.\nRien de \
tout cela ne sert tant qu’on ne le demande pas : un document écrit avant que \
ces réglages existent sort à l’octet près comme avant. Chaque échantillon \
ci-dessous est composé deux fois, et seul le réglage change.",
    headings: [
        "Ligatures",
        "Petites capitales",
        "Chiffres elzéviriens",
        "Formes locales",
        "Crénage",
    ],
    explanations: [
        "Les lettres qui se touchent forment un seul glyphe, prévu pour elles par le \
créateur de la police.",
        "Des minuscules dessinées en capitales pas plus hautes qu’un x.",
        "Des chiffres qui montent et descendent autour de la hauteur d’x au lieu de \
s’aligner sur les capitales.",
        "Les mêmes lettres cyrilliques, dans les formes que la police dessine pour le serbe.",
        "Chaque paire de glyphes écartée autant que la police le demande.",
    ],
    samples: [
        "affiche officielle du greffe",
        "réédition trimestrielle",
        "1 234 567 890",
        "пут, град, беседа",
        "Wagon TAXI Toiture",
    ],
    off: "sans",
    on: "avec",
    glyphs_before: "Le premier échantillon compte ",
    glyphs_between: " glyphes tel quel et ",
    glyphs_after: " avec les ligatures : chaque paire liée ne fait plus qu’un glyphe.",
    kerned_before: "Le dernier échantillon est composé ",
    kerned_after: " points plus étroit avec le crénage, et il est aussi mesuré ainsi : la ligne \
fait bien la largeur qu’elle paraît faire.",
    numbered_before: "Spectral contient ",
    numbered_between: " glyphes, et aucun caractère ne mène à ",
    numbered_then: " d’entre eux : les formes qu’un réglage ou une langue met à la place d’une \
lettre. Les ",
    numbered_after: " premiers, demandés par leur numéro dans le fichier et centrés sur leur largeur \
mesurée :",
    back_title: "Une fonction désactivée, un glyphe par son numéro",
    back_why: "Ligatures et crénage sont activés ensemble, puis les ligatures seules \
sont désactivées : les lettres se séparent de nouveau, et les paires restent crénées.",
    both: "les deux",
    without: "sans liga",
    by_number: "Le glyphe que la police nomme fi, demandé par son numéro et déclaré tenir lieu des deux lettres qu’il joint, pour que le texte se copie en ces deux lettres :",
    fraction_heading: "Fractions",
    fraction_explanation: "Les chiffres de part et d’autre d’une barre oblique, composés en numérateur et en dénominateur.",
};

/// The page in Dutch.
const DUTCH: Words = Words {
    title: "Vijf dingen die een lettertype over zijn eigen letters weet",
    why: "Een lettertypebestand bevat meer dan één glyph per teken. Het zegt welke letters verbonden getekend worden, welke cijfers onder de regel hangen, welke letters een eigen kleinkapitaal hebben, welke letters in een bepaalde taal een andere vorm krijgen, en hoe ver elk paar glyphs uit elkaar moet staan.\nNiets ervan wordt gebruikt tenzij erom gevraagd wordt, dus een document dat geschreven is voordat deze instellingen bestonden, komt er byte voor byte uit zoals vroeger. Elk voorbeeld hieronder is twee keer gezet, en alleen de instelling verschilt.",
    headings: [
        "Ligaturen",
        "Kleinkapitalen",
        "Mediëvalcijfers",
        "Lokale vormen",
        "Kerning",
    ],
    explanations: [
        "Letters die elkaar raken, worden getekend als één glyph die de ontwerper ervoor sneed.",
        "Kleine letters getekend als hoofdletters niet hoger dan een x.",
        "Cijfers die rond de x-hoogte stijgen en dalen in plaats van op kapitaalhoogte te staan.",
        "Dezelfde Cyrillische letters, in de vormen die het lettertype voor het Servisch tekent.",
        "Elk paar glyphs zo ver uit elkaar gezet als het lettertype vraagt.",
    ],
    samples: [
        "officiële flessenafvulling",
        "elk kwartaal herdrukt",
        "1 234 567 890",
        "пут, град, беседа",
        "Wafel TAXI Toren",
    ],
    off: "uit",
    on: "aan",
    glyphs_before: "Het eerste voorbeeld neemt",
    glyphs_between: " glyphs zoals het is en",
    glyphs_after: " met de ligaturen aan: de paren die het lettertype verbindt, zijn elk één glyph.",
    kerned_before: "Het laatste voorbeeld wordt",
    kerned_after: " punten smaller getekend met kerning aan, en het wordt ook zo gemeten, dus is de regel zo breed als hij lijkt.",
    numbered_before: "Spectral bevat",
    numbered_between: " glyphs, en bij",
    numbered_then: " ervan komt geen teken uit: de vormen die een functie of een taal in de plaats van een letter zet. De eerste",
    numbered_after: ", opgevraagd bij hun nummer in het bestand en gecentreerd op hun gemeten breedte:",
    back_title: "Eén functie weer uitgezet, één glyph bij zijn nummer",
    back_why: "Ligaturen en kerning worden samen aangezet, dan worden alleen de ligaturen weer uitgezet: de letters gaan weer uit elkaar, en de paren blijven gekerned.",
    both: "beide",
    without: "zonder liga",
    by_number: "De glyph die het lettertype fi noemt, opgevraagd bij zijn nummer en opgegeven als de twee letters die hij verbindt, zodat de tekst als die twee letters gekopieerd wordt:",
    fraction_heading: "Breuken",
    fraction_explanation: "Cijfers aan weerszijden van een schuine streep, gezet als teller en noemer rond een breukstreep.",
};

/// The page in Portuguese.
const PORTUGUESE: Words = Words {
    title: "Cinco coisas que um tipo de letra sabe sobre as suas letras",
    why: "Um ficheiro de tipo de letra leva mais de um glifo por carácter. Diz que letras se desenham unidas, que algarismos descem abaixo da linha, que letras têm versaletes próprios, que letras tomam outra forma numa língua e a que distância deve ficar cada par de glifos.\nNada disto é usado sem ser pedido, por isso um documento escrito antes de estas definições existirem sai byte a byte como saía. Cada amostra abaixo é composta duas vezes, e só muda a definição.",
    headings: [
        "Ligaduras",
        "Versaletes",
        "Algarismos de estilo antigo",
        "Formas locais",
        "Crenagem",
    ],
    explanations: [
        "As letras que se tocam são desenhadas como um glifo que o desenhador do tipo cortou para elas.",
        "Minúsculas desenhadas como maiúsculas não mais altas do que um x.",
        "Algarismos que sobem e descem em torno da altura do x em vez de ficarem à altura das maiúsculas.",
        "As mesmas letras cirílicas, nas formas que o tipo desenha para o sérvio.",
        "Cada par de glifos afastado tanto quanto o tipo pede.",
    ],
    samples: [
        "ficha oficial do filiado",
        "reimpresso a cada trimestre",
        "1 234 567 890",
        "пут, град, беседа",
        "Vagão TAXI Torta",
    ],
    off: "não",
    on: "sim",
    glyphs_before: "A primeira amostra ocupa",
    glyphs_between: " glifos tal como está e",
    glyphs_after: " com as ligaduras: os pares que o tipo une são um glifo cada.",
    kerned_before: "A última amostra é desenhada",
    kerned_after: " pontos mais estreita com crenagem, e também é medida assim, por isso a linha é tão larga como parece.",
    numbered_before: "O Spectral tem",
    numbered_between: " glifos, e",
    numbered_then: " deles não levam nenhum carácter: as formas que uma funcionalidade ou uma língua põem no lugar de uma letra. Os primeiros",
    numbered_after: ", pedidos pelo seu número no ficheiro e centrados na largura medida:",
    back_title: "Uma funcionalidade desligada de novo, um glifo pelo seu número",
    back_why: "Ligaduras e crenagem são ligadas juntas, e depois só as ligaduras são desligadas: as letras voltam a separar-se, e os pares continuam com crenagem.",
    both: "ambas",
    without: "sem liga",
    by_number: "O glifo a que o tipo chama fi, pedido pelo seu número e indicado como representante das duas letras que une, para que o texto se copie como essas duas letras:",
    fraction_heading: "Frações",
    fraction_explanation: "Os algarismos de cada lado de uma barra, compostos como numerador e denominador em volta de um traço de fração.",
};

/// The page in Italian.
const ITALIAN: Words = Words {
    title: "Cinque cose che un font sa delle proprie lettere",
    why: "Un file di font porta più di un glifo per carattere. Dice quali lettere si disegnano unite, quali cifre scendono sotto la riga, quali lettere hanno un maiuscoletto proprio, quali lettere prendono un’altra forma in una lingua e quanto distante deve stare ogni coppia di glifi.\nNiente di tutto ciò è usato se non lo si chiede, così un documento scritto prima che queste impostazioni esistessero esce byte per byte come usciva. Ogni campione qui sotto è composto due volte, e cambia solo l’impostazione.",
    headings: [
        "Legature",
        "Maiuscoletto",
        "Cifre in stile antico",
        "Forme locali",
        "Crenatura",
    ],
    explanations: [
        "Le lettere che si toccano sono disegnate come un glifo che il disegnatore del carattere ha tagliato per loro.",
        "Minuscole disegnate come maiuscole non più alte di una x.",
        "Cifre che salgono e scendono intorno all’altezza della x anziché stare all’altezza delle maiuscole.",
        "Le stesse lettere cirilliche, nelle forme che il carattere disegna per il serbo.",
        "Ogni coppia di glifi distanziata quanto chiede il font.",
    ],
    samples: [
        "ufficio affiliato fluviale",
        "ristampato ogni trimestre",
        "1 234 567 890",
        "пут, град, беседа",
        "Vagone TAXI Torta",
    ],
    off: "no",
    on: "sì",
    glyphs_before: "Il primo campione occupa",
    glyphs_between: " glifi così com’è e",
    glyphs_after: " con le legature: le coppie che il font unisce sono un glifo ciascuna.",
    kerned_before: "L’ultimo campione è disegnato",
    kerned_after: " punti più stretto con la crenatura, ed è misurato così: la riga è larga quanto sembra.",
    numbered_before: "Spectral contiene",
    numbered_between: " glifi, e a",
    numbered_then: " di essi non corrisponde alcun carattere: le forme che una funzione o una lingua mettono al posto di una lettera. I primi",
    numbered_after: ", chiesti per numero nel file e centrati sulla larghezza misurata:",
    back_title: "Una funzione disattivata di nuovo, un glifo per numero",
    back_why: "Legature e crenatura si attivano insieme, poi si disattivano solo le legature: le lettere si separano di nuovo, e le coppie restano crenate.",
    both: "entrambe",
    without: "senza liga",
    by_number: "Il glifo che il carattere chiama fi, chiesto per numero e indicato come rappresentante delle due lettere che unisce, così il testo si copia come quelle due lettere:",
    fraction_heading: "Frazioni",
    fraction_explanation: "Le cifre ai due lati di una barra, composte come numeratore e denominatore attorno a una barra di frazione.",
};

/// The page in Spanish.
const SPANISH: Words = Words {
    title: "Cinco cosas que una fuente sabe de sus propias letras",
    why: "Un archivo de fuente lleva más de un glifo por carácter. Dice qué letras se dibujan unidas, qué cifras bajan de la línea, qué letras tienen versalita propia, qué letras toman otra forma en un idioma y a qué distancia debe estar cada par de glifos.\nNada de ello se usa si no se pide, así que un documento escrito antes de que existieran estos ajustes sale byte a byte como salía. Cada muestra de abajo se compone dos veces, y solo cambia el ajuste.",
    headings: [
        "Ligaduras",
        "Versalitas",
        "Cifras elzevirianas",
        "Formas locales",
        "Interletraje",
    ],
    explanations: [
        "Las letras que se tocan se dibujan como un glifo que el diseñador de la fuente cortó para ellas.",
        "Minúsculas dibujadas como mayúsculas no más altas que una x.",
        "Cifras que suben y bajan alrededor de la altura de la x en vez de alinearse con las mayúsculas.",
        "Las mismas letras cirílicas, en las formas que la fuente dibuja para el serbio.",
        "Cada par de glifos separado tanto como pide la fuente.",
    ],
    samples: [
        "ficha oficial del afiliado",
        "reimpreso cada trimestre",
        "1 234 567 890",
        "пут, град, беседа",
        "Vagón TAXI Tarta",
    ],
    off: "no",
    on: "sí",
    glyphs_before: "La primera muestra ocupa",
    glyphs_between: " glifos tal cual y",
    glyphs_after: " con las ligaduras: los pares que une la fuente son un glifo cada uno.",
    kerned_before: "La última muestra se dibuja",
    kerned_after: " puntos más estrecha con interletraje, y también se mide así, así que la línea es tan ancha como parece.",
    numbered_before: "Spectral tiene",
    numbered_between: " glifos, y",
    numbered_then: " de ellos no corresponden a ningún carácter: las formas que una función o un idioma ponen en lugar de una letra. Los primeros",
    numbered_after: ", pedidos por su número en el archivo y centrados en su ancho medido:",
    back_title: "Una función desactivada otra vez, un glifo por su número",
    back_why: "Ligaduras e interletraje se activan juntos, y luego se desactivan solo las ligaduras: las letras se separan de nuevo, y los pares siguen con interletraje.",
    both: "ambos",
    without: "sin liga",
    by_number: "El glifo que la fuente llama fi, pedido por su número e indicado como representante de las dos letras que une, para que el texto se copie como esas dos letras:",
    fraction_heading: "Fracciones",
    fraction_explanation: "Las cifras a cada lado de una barra, compuestas como numerador y denominador alrededor de una barra de fracción.",
};

/// The page in German.
const GERMAN: Words = Words {
    title: "Was eine Schrift über ihre Buchstaben weiß",
    why: "Eine Schriftdatei trägt mehr als einen Glyphen je Zeichen. Sie sagt, welche Buchstaben verbunden gezeichnet werden, welche Ziffern unter die Zeile hängen, welche Buchstaben ein eigenes Kapitälchen haben, welche Buchstaben in einer Sprache eine andere Form annehmen und wie weit jedes Glyphenpaar auseinanderstehen soll.\nNichts davon wird genutzt, wenn es nicht verlangt wird, also kommt ein Dokument, das vor diesen Einstellungen geschrieben wurde, Byte für Byte so heraus wie damals. Jedes Muster unten ist zweimal gesetzt, und nur die Einstellung unterscheidet sich.",
    headings: [
        "Ligaturen",
        "Kapitälchen",
        "Mediävalziffern",
        "Lokale Formen",
        "Unterschneidung",
    ],
    explanations: [
        "Sich berührende Buchstaben werden zu einem eigens geschnittenen Glyphen.",
        "Kleinbuchstaben als Versalien, nicht höher als ein x.",
        "Ziffern, die um die x-Höhe auf- und absteigen, statt auf Versalhöhe zu stehen.",
        "Dieselben kyrillischen Buchstaben in ihren serbischen Formen.",
        "Jedes Glyphenpaar so weit gerückt, wie die Schrift verlangt.",
    ],
    samples: [
        "offizielle Kaffeefilter",
        "vierteljährlich nachgedruckt",
        "1 234 567 890",
        "пут, град, беседа",
        "Wagen TAXI Torte",
    ],
    off: "aus",
    on: "an",
    glyphs_before: "Das erste Muster braucht ",
    glyphs_between: " Glyphen, wie es ist, und ",
    glyphs_after: " mit Ligaturen: Die Paare, die die Schrift verbindet, sind je ein Glyph.",
    kerned_before: "Das letzte Muster ist mit Unterschneidung ",
    kerned_after: " Punkt schmaler gezeichnet und wird auch so gemessen, also ist die Zeile so breit, wie sie aussieht.",
    numbered_before: "Spectral enthält ",
    numbered_between: " Glyphen, und kein Zeichen führt zu ",
    numbered_then: " davon: die Formen, die ein Merkmal oder eine Sprache an die Stelle eines Buchstabens setzt. Die ersten ",
    numbered_after: ", über ihre Nummer in der Datei verlangt und auf ihre gemessene Breite zentriert:",
    back_title: "Ein Merkmal wieder ausgeschaltet, ein Glyph über seine Nummer",
    back_why: "Ligaturen und Unterschneidung werden zusammen eingeschaltet, dann wird nur die Ligatur wieder ausgeschaltet: Die Buchstaben trennen sich wieder, und die Paare bleiben unterschnitten.",
    both: "beide",
    without: "ohne liga",
    by_number: "Der Glyph, den der Schnitt fi nennt, über seine Nummer verlangt und als Stellvertreter der zwei Buchstaben angegeben, die er verbindet, sodass der Text als diese zwei Buchstaben herauskopiert wird:",
    fraction_heading: "Brüche",
    fraction_explanation: "Ziffern links und rechts eines Schrägstrichs, gesetzt als Zähler und Nenner um einen Bruchstrich.",
};

/// Every language the example is written in. A language is added by writing its
/// own set of words and naming it here.
static WORDS: [(Language, &Words); 7] = [
    (Language::English, &ENGLISH),
    (Language::French, &FRENCH),
    (Language::German, &GERMAN),
    (Language::Spanish, &SPANISH),
    (Language::Italian, &ITALIAN),
    (Language::Portuguese, &PORTUGUESE),
    (Language::Dutch, &DUTCH),
];

/// The left edge of everything on the page.
const X: f64 = 60.0;

/// The width every block is broken to.
const ROOM: f64 = 475.0;

/// The baseline the title sits on.
const TITLE_TOP: f64 = 780.0;

/// The top of the block that says what the page shows.
const WHY_TOP: f64 = 748.0;

/// The top of each of the five samples, in the order they are drawn.
const TOPS: [f64; 5] = [650.0, 550.0, 450.0, 350.0, 250.0];

/// How far the line that explains a feature sits below its heading.
const EXPLAIN_DROP: f64 = 16.0;

/// How far the setting with nothing turned on sits below the heading.
const OFF_DROP: f64 = 42.0;

/// How far the setting with the feature turned on sits below the heading.
const ON_DROP: f64 = 68.0;

/// Where the word beside a setting is written, and where the sample begins.
const LABEL_X: f64 = X;
const SAMPLE_X: f64 = X + 46.0;

/// The size the samples are set in.
const SAMPLE_SIZE: f64 = 18.0;

/// The size the headings are set in.
const HEADING_SIZE: f64 = 12.0;

/// The size everything that is not a heading or a sample is set in.
const SMALL: f64 = 9.0;

/// The top of the two closing lines.
const CLOSING_TOP: f64 = 150.0;

/// How far the second closing line sits below the first.
const CLOSING_DROP: f64 = 30.0;

/// How far the closing line over the glyphs drawn by number sits below the
/// first.
const NUMBERED_DROP: f64 = 60.0;

/// The baseline of the glyphs drawn by number.
const NUMBERED_BASELINE: f64 = 28.0;

/// How many of the glyphs no character leads to are drawn.
const NUMBERED_SHOWN: usize = 12;

/// The glyphs of `font` no character of its map leads to, by number, leaving
/// out the empty box at zero.
fn unreached(font: &Font) -> Vec<u16> {
    let reached: BTreeSet<GlyphId> = font.coverage().map(|(_, glyph)| glyph).collect();
    let held = u16::try_from(font.glyph_count()).unwrap_or(u16::MAX);
    (1..held)
        .filter(|number| !reached.contains(&GlyphId::new(*number)))
        .collect()
}

/// Draws one line of text at `size`, left-aligned at `x`, with its baseline
/// under `top`.
fn line(
    c: &mut Content,
    handle: &FontHandle,
    text: &str,
    size: f64,
    x: f64,
    top: f64,
) -> hqf_pdf::Result<()> {
    let flow = TextFlow::new(handle, size);
    let lines = flow.break_lines(text, ROOM);
    c.begin_text();
    flow.draw(c, &lines, x, top, ROOM)?;
    c.end_text();
    Ok(())
}

/// The name the face gives the glyph joining `f` and `i`.
const JOINED: &str = "fi";

/// The tops of the second page's two settings, and of the line over the glyph
/// drawn by its number, and that glyph's baseline.
const BACK_TOPS: [f64; 2] = [680.0, 650.0];
const BY_NUMBER_TOP: f64 = 610.0;
const BY_NUMBER_BASELINE: f64 = 550.0;

/// The top of the fraction sample on the second page.
const FRACTION_TOP: f64 = 480.0;

/// The fraction sample, written the same way in every language.
const FRACTIONS: &str = "1/2 3/4 15/16";

/// The second page: the ligature sample with ligatures and kerning, then with
/// ligatures turned back off, the glyph numbered `joined` stated to stand for
/// the two letters it joins, and the fraction sample without and with the
/// `frac` feature.
fn back_page(
    plain: &FontHandle,
    words: &Words,
    joined: Option<u16>,
) -> Result<Page, hqf_pdf::Error> {
    let mut c = Content::new();
    line(&mut c, plain, words.back_title, 18.0, X, TITLE_TOP)?;
    let why = TextFlow::new(plain, 10.0).leading(14.0);
    let why_lines = why.break_lines(words.back_why, ROOM);
    c.begin_text();
    why.draw(&mut c, &why_lines, X, WHY_TOP, ROOM)?;
    c.end_text();

    let both = plain.clone().with_ligatures().kerning();
    let apart = both.clone().without_feature(*b"liga");
    for ((label, handle), top) in [(words.both, &both), (words.without, &apart)]
        .into_iter()
        .zip(BACK_TOPS)
    {
        line(&mut c, plain, label, SMALL, LABEL_X, top)?;
        line(&mut c, handle, words.samples[0], SAMPLE_SIZE, SAMPLE_X, top)?;
    }

    if let Some(number) = joined {
        let over = TextFlow::new(plain, 10.0).leading(14.0);
        let over_lines = over.break_lines(words.by_number, ROOM);
        c.begin_text();
        over.draw(&mut c, &over_lines, X, BY_NUMBER_TOP, ROOM)?;
        c.end_text();
        let glyph = plain.numbered_glyph_standing_for(number, JOINED)?;
        c.begin_text();
        c.set_font(plain, SAMPLE_SIZE)?
            .text_origin(X, BY_NUMBER_BASELINE)?;
        c.show_glyphs(&[glyph]);
        c.end_text();
    }

    line(
        &mut c,
        plain,
        words.fraction_heading,
        HEADING_SIZE,
        X,
        FRACTION_TOP,
    )?;
    line(
        &mut c,
        plain,
        words.fraction_explanation,
        SMALL,
        X,
        FRACTION_TOP - EXPLAIN_DROP,
    )?;
    let fractions = plain.clone().with_feature(*b"frac");
    for (drop, label, handle) in [
        (OFF_DROP, words.off, plain),
        (ON_DROP, words.on, &fractions),
    ] {
        line(&mut c, plain, label, SMALL, LABEL_X, FRACTION_TOP - drop)?;
        line(
            &mut c,
            handle,
            FRACTIONS,
            SAMPLE_SIZE,
            SAMPLE_X,
            FRACTION_TOP - drop,
        )?;
    }

    let mut page = Page::a4();
    page.content = c.into_bytes();
    Ok(page)
}

fn main() -> std::process::ExitCode {
    failure::reported(run())
}

fn run() -> Result<(), Box<dyn std::error::Error>> {
    let language = Language::from_environment()?;
    let words = Words::of(language);

    let out = env::args()
        .nth(1)
        .unwrap_or_else(|| language.file_name(&out::default_path("typography")));

    let bytes = fs::read(font_dir().join("Spectral-Regular.ttf"))?;

    let mut doc = Document::new();
    doc.set_license(licence::licensed());
    let font = Font::parse(bytes)?;
    let held = font.glyph_count();
    let unreached = unreached(&font);
    let ligature = font.glyph_named(JOINED).map(GlyphId::index);
    let plain = doc.add_font(font);

    // One handle per feature, each turned on alone: the two settings of a
    // sample then differ in exactly one thing.
    let with: [FontHandle; 5] = [
        plain.clone().with_ligatures(),
        plain.clone().with_small_capitals(),
        plain.clone().with_oldstyle_figures(),
        plain
            .clone()
            .with_feature(*b"locl")
            .with_language_system(*b"cyrl", Some(*b"SRB ")),
        plain.clone().kerning(),
    ];

    let mut c = Content::new();

    line(&mut c, &plain, words.title, 18.0, X, TITLE_TOP)?;

    let why = TextFlow::new(&plain, 10.0).leading(14.0);
    let why_lines = why.break_lines(words.why, ROOM);
    c.begin_text();
    why.draw(&mut c, &why_lines, X, WHY_TOP, ROOM)?;
    c.end_text();

    for (index, top) in TOPS.iter().enumerate() {
        line(&mut c, &plain, words.headings[index], HEADING_SIZE, X, *top)?;
        line(
            &mut c,
            &plain,
            words.explanations[index],
            SMALL,
            X,
            top - EXPLAIN_DROP,
        )?;

        for (drop, label, handle) in [
            (OFF_DROP, words.off, &plain),
            (ON_DROP, words.on, &with[index]),
        ] {
            line(&mut c, &plain, label, SMALL, LABEL_X, top - drop)?;
            line(
                &mut c,
                handle,
                words.samples[index],
                SAMPLE_SIZE,
                SAMPLE_X,
                top - drop,
            )?;
        }
    }

    // The closing lines are read off the fonts, not written down.
    let apart = plain
        .runs(words.samples[0])
        .iter()
        .map(|run| run.glyphs().len())
        .sum();
    let joined = with[0]
        .runs(words.samples[0])
        .iter()
        .map(|run| run.glyphs().len())
        .sum();
    let saved = plain.measure(words.samples[4], SAMPLE_SIZE)
        - with[4].measure(words.samples[4], SAMPLE_SIZE);

    let shown = &unreached[..NUMBERED_SHOWN.min(unreached.len())];

    let closing = TextFlow::new(&plain, 10.0).leading(14.0);
    for (drop, text) in [
        (0.0, words.glyph_line(apart, joined)),
        (CLOSING_DROP, words.kerned_line(saved)),
        (
            NUMBERED_DROP,
            words.numbered_line(held, unreached.len(), shown.len()),
        ),
    ] {
        let lines = closing.break_lines(&text, ROOM);
        c.begin_text();
        closing.draw(&mut c, &lines, X, CLOSING_TOP - drop, ROOM)?;
        c.end_text();
    }

    // Drawn by their number, since no character leads to them.
    let row = plain.numbered_glyphs(shown.iter().copied())?;
    let row_width = plain.measure_glyphs(&row, SAMPLE_SIZE);
    c.begin_text();
    c.set_font(&plain, SAMPLE_SIZE)?
        .text_origin(X + (ROOM - row_width) / 2.0, NUMBERED_BASELINE)?;
    c.show_glyphs(&row);
    c.end_text();

    let mut page = Page::a4();
    page.content = c.into_bytes();
    doc.add_page(page)?;
    doc.add_page(back_page(&plain, words, ligature)?)?;

    let bytes = doc.to_bytes()?;
    if let Some(parent) = Path::new(&out).parent() {
        fs::create_dir_all(parent)?;
    }
    fs::write(&out, &bytes)?;
    println!("wrote {out}: {} bytes", bytes.len());
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::{
        CLOSING_DROP, CLOSING_TOP, FRACTIONS, HEADING_SIZE, NUMBERED_BASELINE, NUMBERED_DROP,
        NUMBERED_SHOWN, ON_DROP, ROOM, SAMPLE_SIZE, SAMPLE_X, SMALL, TOPS, WORDS, X, language,
        unreached,
    };
    use hqf_pdf::{Document, Font, FontHandle, TextFlow};

    /// The lines two languages are allowed to write the same way: the figures
    /// are figures in both, the Serbian words are Serbian in both, and
    /// ligatures are called ligatures in both.
    const SPARED: [&str; 9] = [
        "\"1 234 567 890\"",
        "\"пут, град, беседа\"",
        "\"Ligatures\"",
        // Written the same way in Italian.
        r#"off: "no""#,
        // Written the same way in Portuguese.
        r#""Ligaduras""#,
        // Written the same way in Dutch.
        r#""Kerning""#,
        r#""Ligaturen""#,
        r#"both: "beide""#,
        // Written the same way in French.
        r#"fraction_heading: "Fractions""#,
    ];

    /// The room a sample has, from where it begins to the edge of the block.
    const SAMPLE_ROOM: f64 = ROOM - SAMPLE_X + X;

    /// The committed font, added to a document of its own.
    fn font() -> (Document, FontHandle) {
        let bytes = std::fs::read(super::font_dir().join("Spectral-Regular.ttf"))
            .expect("the font is committed");
        let mut doc = Document::new();
        let handle = doc.add_font(Font::parse(bytes).expect("the font parses"));
        (doc, handle)
    }

    #[test]
    fn every_language_draws_the_page_in_its_own_words() {
        let untranslated = language::untranslated_lines(&WORDS, &SPARED);

        assert!(
            untranslated.is_empty(),
            "the page says these in more than one language: {untranslated:?}"
        );
    }

    /// The page rests on the font joining letters in the first sample, drawing
    /// Serbian forms in the fourth and kerning pairs in the last: a page whose
    /// two settings drew the same thing would show nothing at all.
    #[test]
    fn every_language_gives_the_two_settings_something_to_differ_about() {
        let (_doc, plain) = font();
        let joined = plain.clone().with_ligatures();
        let kerned = plain.clone().kerning();
        let local = plain
            .clone()
            .with_feature(*b"locl")
            .with_language_system(*b"cyrl", Some(*b"SRB "));

        for (code, words) in WORDS {
            let ligature_sample = words.samples[0];
            assert!(
                joined.runs(ligature_sample)[0].glyphs().len()
                    < plain.runs(ligature_sample)[0].glyphs().len(),
                "{code:?} writes a first sample the font joins nothing in"
            );

            let kerning_sample = words.samples[4];
            assert!(
                kerned.measure(kerning_sample, SAMPLE_SIZE)
                    < plain.measure(kerning_sample, SAMPLE_SIZE),
                "{code:?} writes a last sample the font kerns nothing in"
            );

            let figures = words.samples[2];
            assert_ne!(
                plain.clone().with_oldstyle_figures().runs(figures)[0].glyphs(),
                plain.runs(figures)[0].glyphs(),
                "{code:?} writes a sample of figures the font hangs none of"
            );

            let serbian = words.samples[3];
            assert_ne!(
                local.runs(serbian)[0].glyphs(),
                plain.runs(serbian)[0].glyphs(),
                "{code:?} writes a Serbian sample the font draws no local form in"
            );
            assert_eq!(
                plain.clone().with_feature(*b"locl").runs(serbian)[0].glyphs(),
                plain.runs(serbian)[0].glyphs(),
                "the forms are Serbian ones, not the default language's"
            );
        }
    }

    /// The fraction sample rests on the font drawing each figure after a slash
    /// as a denominator, which only the glyphs around it say.
    #[test]
    fn the_fraction_sample_draws_its_denominators_after_the_bar() {
        let (_doc, plain) = font();
        let fractions = plain.with_feature(*b"frac");
        let drawn = fractions.glyphs(FRACTIONS);
        let bytes = std::fs::read(super::font_dir().join("Spectral-Regular.ttf"))
            .expect("the font is committed");
        let face = Font::parse(bytes).expect("the font parses");
        let named = |name| face.glyph_named(name).expect("the face names it");

        assert_eq!(drawn[0], named("one.sups"));
        assert_eq!(drawn[2], named("two.sinf"), "after the bar");
        assert_eq!(drawn[4], named("three.sups"), "after the space");
    }

    /// The second sample rests on the font having a small capital for the
    /// letters it holds, and on the capitals being left where they stand.
    #[test]
    fn the_small_capitals_sample_is_drawn_with_small_capitals() {
        let (_doc, plain) = font();
        let asked = plain.clone().with_small_capitals();

        for (code, words) in WORDS {
            let sample = words.samples[1];
            assert_ne!(
                asked.runs(sample)[0].glyphs(),
                plain.runs(sample)[0].glyphs(),
                "{code:?} writes a second sample the font has no small capital for"
            );
            assert!(
                sample.chars().all(|ch| !ch.is_uppercase()),
                "{code:?} writes a capital into the sample, which the setting leaves alone"
            );
        }
    }

    /// Nothing the page draws runs off the paper.
    #[test]
    fn every_language_writes_blocks_no_wider_than_the_room_they_have() {
        let (_doc, plain) = font();

        for (code, words) in WORDS {
            for (text, size, room) in [
                (words.title, 18.0, ROOM),
                (words.off, SMALL, ROOM),
                (words.on, SMALL, ROOM),
                (words.fraction_heading, HEADING_SIZE, ROOM),
                (words.fraction_explanation, SMALL, ROOM),
                (FRACTIONS, SAMPLE_SIZE, SAMPLE_ROOM),
            ] {
                let width = plain.measure(text, size);
                assert!(
                    width <= room,
                    "{code:?} writes {width} points in {room}: {text}"
                );
            }

            for index in 0..TOPS.len() {
                let heading = plain.measure(words.headings[index], HEADING_SIZE);
                assert!(heading <= ROOM, "{code:?} writes a heading of {heading}");

                let explanation = plain.measure(words.explanations[index], SMALL);
                assert!(
                    explanation <= ROOM,
                    "{code:?} writes an explanation of {explanation} points"
                );

                let sample = plain.measure(words.samples[index], SAMPLE_SIZE);
                assert!(
                    sample <= SAMPLE_ROOM,
                    "{code:?} writes a sample of {sample} points in {SAMPLE_ROOM}"
                );
            }
        }
    }

    /// The samples stand clear of one another, and the last stands clear of the
    /// closing lines.
    #[test]
    fn nothing_the_page_draws_lands_on_what_comes_after_it() {
        let (_doc, plain) = font();
        let flow = TextFlow::new(&plain, SAMPLE_SIZE);

        for (code, words) in WORDS {
            for (index, top) in TOPS.iter().enumerate() {
                let lines = flow.break_lines(words.samples[index], ROOM);
                let bottom = top - ON_DROP - flow.height(&lines);
                let next = TOPS.get(index + 1).copied().unwrap_or(CLOSING_TOP);
                assert!(
                    bottom > next,
                    "{code:?} sets its sample {index} down to {bottom}, over {next}"
                );
            }

            let closing = TextFlow::new(&plain, 10.0).leading(14.0);
            let lines = closing.break_lines(&words.kerned_line(9.9), ROOM);
            let bottom = CLOSING_TOP - CLOSING_DROP - closing.height(&lines);
            assert!(
                bottom > CLOSING_TOP - NUMBERED_DROP,
                "{code:?} sets its kerning line down onto the next"
            );

            let numbered = words.numbered_line(1480, 601, NUMBERED_SHOWN);
            let lines = closing.break_lines(&numbered, ROOM);
            let bottom = CLOSING_TOP - NUMBERED_DROP - closing.height(&lines);
            let row_top = NUMBERED_BASELINE + plain.ascent(SAMPLE_SIZE);
            assert!(
                bottom > row_top,
                "{code:?} sets its last line down to {bottom}, over the glyphs at {row_top}"
            );
        }
    }

    /// The last row holds glyphs no character leads to, all of them the face
    /// holds, and it fits the block it is centred in.
    #[test]
    fn the_glyphs_drawn_by_number_are_ones_no_character_leads_to() {
        let bytes = std::fs::read(super::font_dir().join("Spectral-Regular.ttf"))
            .expect("the font is committed");
        let font = Font::parse(bytes).expect("the font parses");
        let numbers = unreached(&font);
        let mut doc = Document::new();
        let plain = doc.add_font(font.clone());

        assert!(
            numbers.len() >= NUMBERED_SHOWN,
            "the face has twelve to show"
        );
        for (_, glyph) in font.coverage() {
            assert!(!numbers.contains(&glyph.index()));
        }
        let row = plain
            .numbered_glyphs(numbers[..NUMBERED_SHOWN].iter().copied())
            .expect("the face holds them");
        let width = plain.measure_glyphs(&row, SAMPLE_SIZE);
        assert!(width > 0.0 && width <= ROOM, "a row of {width} points");
    }
}