write_slideshow.rs

//! A slideshow: fourteen pages, each arriving by a different effect.
//!
//! The file opens full screen, and every page states how it arrives and how
//! long it stands before the next one comes by itself. Nothing here is drawn by
//! the effect: each page simply names the one that brings it in, so what
//! reading software does can be checked against what the file asked for.
//!
//! Open it in reading software that honours full screen to see them run.
//!
//! The title slide also carries a link that acts rather than leads: following
//! it asks reading software to show the screen again, brought in by dissolving.
//! Each slide keeps the effect it states for itself.
//!
//! The slides are written in the language `HQF_PDF_LANG` names: what an effect
//! is called and what it does are words a person reads. The entries the file
//! writes for it are not — `/S /Split /Dm /V /M /O` is what reading software
//! parses, and it is the same in every language, so each slide carries both.
//!
//! Usage: `cargo run --example write_slideshow -- tmp/slideshow.pdf [font.ttf]`
//!        `HQF_PDF_LANG=fr cargo run --example write_slideshow`

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

use hqf_pdf::action::Action;
use hqf_pdf::content::Content;
use hqf_pdf::transition::{Axis, Effect, Heading, Motion, Transition};
use hqf_pdf::{Color, Document, Error, Font, FontHandle, Link, OpenMode, Page, Rgb};

#[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;

/// The font the example draws with when none is given on the command line.
fn default_font() -> PathBuf {
    Path::new(env!("CARGO_MANIFEST_DIR"))
        .join("tests")
        .join("fonts")
        .join("DejaVuSans.ttf")
}

/// A slide, laid down sideways: a projected page is wider than it is tall.
const SHEET: (f64, f64) = (720.0, 540.0);

/// How far in from the edge of the slide everything is set.
const MARGIN: f64 = 64.0;

/// How long each slide stands before the next arrives, in seconds.
const STANDS: f64 = 4.0;

/// How long each effect takes, in seconds.
const TAKES: f64 = 1.0;

/// The size a slide's name is set at, in points.
const NAME: f64 = 54.0;

/// The size the line under a slide's name is set at, in points.
const DOES: f64 = 15.0;

/// The size the title slide's heading is set at, in points.
const TITLE: f64 = 42.0;

/// The size the lines of the title slide are set at, in points.
const INTRO: f64 = 12.0;

/// How far apart the lines of the title slide are stacked, in points.
const INTRO_STEP: f64 = 20.0;

/// The baseline of the line on the title slide that a link lies over.
const FOLLOW_AT: f64 = 90.0;

/// How far below its baseline, and how far above, the link over that line
/// reaches.
const FOLLOW_REACH: (f64, f64) = (4.0, 12.0);

/// How wide the link over that line is: the room between the two margins.
const FOLLOW_WIDTH: f64 = SHEET.0 - 2.0 * MARGIN;

/// The words the slides are written in, one set per language.
///
/// What is not language stays out of it: the entries the file writes for each
/// effect are what reading software parses, and the name on the footer is a
/// name.
#[derive(Debug)]
struct Words {
    /// What the title slide is headed by.
    title: &'static str,
    /// The line under that heading.
    strapline: &'static str,
    /// What the title slide says the file asks reading software for.
    intro: [&'static str; 4],
    /// What the title slide says of itself.
    stands_still: &'static str,
    /// The line on the title slide a link lies over, saying what following it
    /// does.
    follow: &'static str,
    /// What stands between a slide's number and the count of them.
    of: &'static str,
    /// What is written over the entries the file states for a slide.
    states_label: &'static str,
    /// What each effect is called, in the order `EFFECTS` sets them.
    names: [&'static str; EFFECTS.len()],
    /// What each effect does, in the same order.
    does: [&'static str; EFFECTS.len()],
}

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

/// The slides in English.
const ENGLISH: Words = Words {
    title: "Twelve ways in",
    strapline: "Every effect a PDF can ask reading software for, one to a slide.",
    intro: [
        "This file opens full screen, and each slide states how it arrives and how long",
        "it stands before the next one comes by itself. Reading software that honours",
        "all of it runs the whole thing unattended; one that honours none of it shows",
        "fourteen pages, and nothing is lost.",
    ],
    stands_still: "This first slide arrives by nothing at all: it is the one already on the screen.",
    follow: "Click this line and the screen you are on is shown again, dissolving in.",
    of: "of",
    states_label: "the file states",
    names: [
        "Split",
        "Blinds",
        "Box",
        "Wipe",
        "Dissolve",
        "Glitter",
        "Fly",
        "Fly, at the reader",
        "Push",
        "Cover",
        "Uncover",
        "Fade",
        "Replace",
    ],
    does: [
        "Two lines sweep apart to reveal the slide.",
        "Many lines sweep across at once, like a blind opening.",
        "A rectangle opens out of the middle of the slide.",
        "One line sweeps left to right.",
        "The slide before it dissolves into this one.",
        "The dissolve travels from the top-left corner down.",
        "The slide before it flies off downwards.",
        "What has changed flies out of the screen, starting small.",
        "Both slides slide together, the old one pushing this on.",
        "This slide slides up over the one before it.",
        "The slide before it slides down off this one.",
        "The slide fades up out of reading software's own background.",
        "Nothing sweeps or fades: the slide is simply there.",
    ],
};

/// The slides in French.
const FRENCH: Words = Words {
    title: "Douze façons d'entrer",
    strapline: "Tous les effets qu'un PDF demande au logiciel de lecture, un par diapositive.",
    intro: [
        "Ce fichier s'ouvre en plein écran, et chaque diapositive dit comment elle arrive et",
        "combien de temps elle reste avant que la suivante vienne d'elle-même. Un logiciel",
        "de lecture qui suit tout cela déroule l'ensemble sans personne ; celui qui n'en suit",
        "rien montre quatorze pages, et rien n'est perdu.",
    ],
    stands_still: "Cette première diapositive n'arrive par rien du tout : elle est déjà à l'écran.",
    follow: "Cliquez cette ligne : l'écran où vous êtes est réaffiché par dissolution.",
    of: "sur",
    states_label: "ce que le fichier écrit",
    names: [
        "Séparation",
        "Stores",
        "Boîte",
        "Balayage",
        "Dissolution",
        "Scintillement",
        "Envol",
        "Envol vers l'avant",
        "Poussée",
        "Recouvrement",
        "Dévoilement",
        "Fondu",
        "Remplacement",
    ],
    does: [
        "Deux traits s'écartent et découvrent la diapositive.",
        "Plusieurs traits balaient l'écran d'un coup, comme un store qui s'ouvre.",
        "Un rectangle s'ouvre depuis le milieu de la diapositive.",
        "Un trait balaie l'écran de la gauche vers la droite.",
        "La diapositive précédente se dissout dans celle-ci.",
        "La dissolution part du coin haut gauche et descend.",
        "La diapositive précédente s'envole vers le bas.",
        "Ce qui a changé sort de l'écran, petit d'abord puis grand.",
        "Les deux diapositives glissent ensemble, l'ancienne poussant celle-ci.",
        "Cette diapositive glisse vers le haut par-dessus la précédente.",
        "La diapositive précédente glisse vers le bas et libère celle-ci.",
        "La diapositive apparaît en fondu depuis le fond du logiciel de lecture.",
        "Rien ne balaie ni ne s'estompe : la diapositive est là.",
    ],
};

/// 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); 2] =
    [(Language::English, &ENGLISH), (Language::French, &FRENCH)];

/// Draws one line of text with its baseline at `(x, y)`.
fn text(
    content: &mut Content,
    font: &FontHandle,
    size: f64,
    x: f64,
    y: f64,
    line: &str,
) -> Result<(), Error> {
    content.begin_text();
    content.set_font(font, size)?;
    content.text_origin(x, y)?;
    content.show_glyphs(&font.glyphs(line));
    content.end_text();
    Ok(())
}

/// One slide: a wash of colour, the name of the effect that brings it in, what
/// that effect does, and the entries the file states for it.
fn slide(
    font: &FontHandle,
    words: &Words,
    wash: Rgb,
    number: &str,
    name: &str,
    does: &str,
    states: &str,
) -> Result<Vec<u8>, Error> {
    let mut content = Content::new();
    content.save_state();
    content.set_fill(wash)?;
    content.rect(0.0, 0.0, SHEET.0, SHEET.1)?.fill();
    content.restore_state();

    content.save_state();
    content.set_fill(Rgb::new(1.0, 1.0, 1.0))?;
    content.rect(0.0, SHEET.1 - 8.0, SHEET.0, 8.0)?.fill();
    content.restore_state();

    content.save_state();
    content.set_fill(Rgb::new(1.0, 1.0, 1.0))?;
    text(&mut content, font, DOES, MARGIN, SHEET.1 - 70.0, number)?;
    text(&mut content, font, NAME, MARGIN, 300.0, name)?;
    content.restore_state();

    content.save_state();
    content.set_fill(Color::Gray(0.92))?;
    text(&mut content, font, DOES, MARGIN, 254.0, does)?;
    content.restore_state();

    content.save_state();
    content.set_fill(Color::Gray(0.82))?;
    text(
        &mut content,
        font,
        11.0,
        MARGIN,
        MARGIN + 34.0,
        words.states_label,
    )?;
    text(&mut content, font, 11.0, MARGIN, MARGIN + 16.0, states)?;
    content.restore_state();
    Ok(content.into_bytes())
}

/// The title slide, which nothing brings in: it is the one already there.
fn title(font: &FontHandle, words: &Words) -> Result<Vec<u8>, Error> {
    let mut content = Content::new();
    content.save_state();
    content.set_fill(Rgb::new(0.09, 0.11, 0.16))?;
    content.rect(0.0, 0.0, SHEET.0, SHEET.1)?.fill();
    content.restore_state();

    content.save_state();
    content.set_fill(Rgb::new(1.0, 1.0, 1.0))?;
    text(&mut content, font, TITLE, MARGIN, 330.0, words.title)?;
    content.set_fill(Color::Gray(0.72))?;
    text(&mut content, font, DOES, MARGIN, 286.0, words.strapline)?;
    content.restore_state();

    content.save_state();
    content.set_fill(Color::Gray(0.55))?;
    let mut y = 210.0;
    for line in words.intro {
        text(&mut content, font, INTRO, MARGIN, y, line)?;
        y -= INTRO_STEP;
    }
    // The line that speaks of this slide alone stands a blank line clear of the
    // ones that speak of the file.
    y -= INTRO_STEP;
    text(&mut content, font, INTRO, MARGIN, y, words.stands_still)?;
    text(&mut content, font, INTRO, MARGIN, FOLLOW_AT, words.follow)?;
    content.restore_state();

    content.save_state();
    content.set_fill(Color::Gray(0.4))?;
    text(&mut content, font, 11.0, MARGIN, MARGIN, "HQF Development")?;
    content.restore_state();
    Ok(content.into_bytes())
}

/// One slide's worth: how it arrives, the wash it is laid on, and the entries
/// the file writes for it. What the effect is called and what it does are words
/// a person reads, and are held in `Words`.
type Slide = (Effect, Rgb, &'static str);

/// The thirteen slides after the title one: the twelve effects the format
/// defines, `Fly` standing on two of them.
const EFFECTS: [Slide; 13] = [
    (
        Effect::Split {
            axis: Axis::Vertical,
            motion: Motion::Outward,
        },
        Rgb::new(0.13, 0.29, 0.36),
        "/S /Split /Dm /V /M /O",
    ),
    (
        Effect::Blinds {
            axis: Axis::Horizontal,
        },
        Rgb::new(0.16, 0.34, 0.31),
        "/S /Blinds /Dm /H",
    ),
    (
        Effect::Box {
            motion: Motion::Outward,
        },
        Rgb::new(0.24, 0.33, 0.22),
        "/S /Box /M /O",
    ),
    (
        Effect::Wipe {
            heading: Heading::Rightwards,
        },
        Rgb::new(0.36, 0.32, 0.16),
        "/S /Wipe /Di 0",
    ),
    (Effect::Dissolve, Rgb::new(0.40, 0.26, 0.16), "/S /Dissolve"),
    (
        Effect::Glitter {
            heading: Heading::Diagonally,
        },
        Rgb::new(0.42, 0.20, 0.20),
        "/S /Glitter /Di 315",
    ),
    (
        Effect::Fly {
            heading: Some(Heading::Downwards),
            scale: None,
            whole_page: true,
        },
        Rgb::new(0.38, 0.17, 0.30),
        "/S /Fly /Di 270 /B true",
    ),
    (
        Effect::Fly {
            heading: None,
            scale: Some(0.6),
            whole_page: false,
        },
        Rgb::new(0.31, 0.18, 0.38),
        "/S /Fly /Di /None /SS 0.6 /B false",
    ),
    (
        Effect::Push {
            heading: Heading::Leftwards,
        },
        Rgb::new(0.21, 0.20, 0.42),
        "/S /Push /Di 180",
    ),
    (
        Effect::Cover {
            heading: Heading::Upwards,
        },
        Rgb::new(0.14, 0.26, 0.42),
        "/S /Cover /Di 90",
    ),
    (
        Effect::Uncover {
            heading: Heading::Downwards,
        },
        Rgb::new(0.11, 0.31, 0.38),
        "/S /Uncover /Di 270",
    ),
    (Effect::Fade, Rgb::new(0.20, 0.20, 0.22), "/S /Fade"),
    (Effect::Replace, Rgb::new(0.09, 0.11, 0.16), "/S /R"),
];

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 mut args = env::args().skip(1);
    // A named file is written as named; the default one carries the language,
    // so the two languages do not overwrite each other in `tmp/`.
    let out = args
        .next()
        .unwrap_or_else(|| language.file_name(&out::default_path("slideshow")));
    let font_path = args.next().map_or_else(default_font, PathBuf::from);

    let mut doc = Document::new();
    doc.set_license(licence::licensed());
    let font = doc.add_font(Font::parse(fs::read(&font_path)?)?);

    let mut first = Page::new(SHEET.0, SHEET.1);
    first.content = title(&font, words)?;
    first.duration = Some(STANDS);
    first.links.push(Link::acting(
        MARGIN,
        FOLLOW_AT - FOLLOW_REACH.0,
        FOLLOW_WIDTH,
        FOLLOW_REACH.0 + FOLLOW_REACH.1,
        Action::Transition(Transition::new(Effect::Dissolve).seconds(TAKES)),
    ));
    doc.add_page(first)?;

    let total = EFFECTS.len() + 1;
    for (index, (effect, wash, states)) in EFFECTS.into_iter().enumerate() {
        let number = format!("{} {} {total}", index + 2, words.of);
        let mut page = Page::new(SHEET.0, SHEET.1);
        page.content = slide(
            &font,
            words,
            wash,
            &number,
            words.names[index],
            words.does[index],
            states,
        )?;
        page.transition = Some(Transition::new(effect).seconds(TAKES));
        page.duration = Some(STANDS);
        doc.add_page(page)?;
    }

    // A transition is read in full screen and nowhere else, so a slideshow that
    // does not ask for full screen asks for nothing.
    doc.set_open_mode(OpenMode::FullScreen);

    let written = doc.to_bytes()?;
    if let Some(parent) = Path::new(&out).parent() {
        fs::create_dir_all(parent)?;
    }
    fs::write(&out, &written)?;
    println!(
        "wrote {out}: {} bytes, {} slides, each arriving by a different effect",
        written.len(),
        doc.page_count()
    );
    Ok(())
}

#[cfg(test)]
mod tests {
    use hqf_pdf::{Document, Font};

    use super::{DOES, EFFECTS, INTRO, MARGIN, NAME, SHEET, TITLE, WORDS, default_font, language};

    /// The room a line set from the left margin has before it reaches the
    /// margin on the other side of the slide.
    const ROOM: f64 = SHEET.0 - 2.0 * MARGIN;

    /// The lines two languages are allowed to write the same way. There are
    /// none: the entries the file writes for each effect are held outside the
    /// words, and so is the name on the footer.
    const SPARED: [&str; 0] = [];

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

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

    /// Nothing on a slide is broken to a width: a line longer than the slide
    /// runs off the edge of it, and the name of an effect is set at 54 points,
    /// where a word or two more is all it takes.
    #[test]
    fn every_language_writes_lines_that_fit_the_slide() {
        let mut doc = Document::new();
        let font = doc.add_font(
            Font::parse(std::fs::read(default_font()).expect("the committed font is there"))
                .expect("the committed font parses"),
        );

        for (named, words) in WORDS {
            let lines = [(TITLE, words.title), (DOES, words.strapline)]
                .into_iter()
                .chain(words.intro.map(|line| (INTRO, line)))
                .chain([(INTRO, words.stands_still), (INTRO, words.follow)])
                .chain(words.names.map(|name| (NAME, name)))
                .chain(words.does.map(|does| (DOES, does)));

            for (size, line) in lines {
                let measured = font.measure(line, size);
                assert!(
                    measured <= ROOM,
                    "the {} slides draw {line:?} over {measured:.1} points, \
                     and they have {ROOM:.1}",
                    named.code()
                );
            }
        }
    }

    /// The strapline of the title slide promises every effect the format
    /// defines, one to a slide. Each slide is named here by the entries the
    /// file writes for it, which are the same in every language.
    #[test]
    fn every_effect_the_format_defines_stands_on_a_slide() {
        const DEFINED: [&str; 12] = [
            "/S /R",
            "/S /Split",
            "/S /Blinds",
            "/S /Box",
            "/S /Wipe",
            "/S /Dissolve",
            "/S /Glitter",
            "/S /Fly",
            "/S /Push",
            "/S /Cover",
            "/S /Uncover",
            "/S /Fade",
        ];

        let missing: Vec<&str> = DEFINED
            .into_iter()
            .filter(|entries| {
                !EFFECTS
                    .iter()
                    .any(|(_, _, states)| states.starts_with(*entries))
            })
            .collect();

        assert!(missing.is_empty(), "no slide arrives by {missing:?}");
    }

    /// The heading of the title slide counts the effects in words, and the
    /// lines under it count the pages the same way. Neither can be worked out
    /// from the table, so an effect added or dropped has to be carried into
    /// every language by hand — and this is what says so.
    #[test]
    fn the_counts_written_in_words_are_the_counts_the_file_has() {
        assert_eq!(
            EFFECTS.len(),
            13,
            "the title slide says twelve effects, and `Fly` stands on two slides"
        );
        assert_eq!(EFFECTS.len() + 1, 14, "the title slide says fourteen pages");
    }
}