designcraft/crates/doc/src/otf.rs

//! OpenType features as the Character panel's OpenType menu offers them, kept in a character
//! format's `otf_features` tag list (`"dlig"` on, `"-calt"` off).

/// On/off features: (tag, menu label, IDML attribute).
pub const TOGGLES: &[(&str, &str, &str)] = &[
    ("dlig", "Discretionary Ligatures", "OTFDiscretionaryLigature"),
    ("frac", "Fractions", "OTFFraction"),
    ("ordn", "Ordinal", "OTFOrdinal"),
    ("swsh", "Swash", "OTFSwash"),
    ("titl", "Titling Alternates", "OTFTitling"),
    ("calt", "Contextual Alternates", "OTFContextualAlternate"),
    ("zero", "Slashed Zero", "OTFSlashedZero"),
    ("palt", "Proportional Metrics", "OTFProportionalMetrics"),
    ("hkna", "Horizontal Kana", "OTFHVKana"),
    ("locl", "Localized Forms", "OTFLocale"),
    ("mark", "Mark Positioning", "OTFMark"),
    ("hist", "Historical Forms", "OTFHistorical"),
    ("salt", "Stylistic Alternates", "OTFStylisticAlternate"),
    ("jalt", "Justification Alternates", "OTFJustificationAlternate"),
    ("ital", "Roman Italics", "OTFRomanItalics"),
];

/// Figure styles: (id, menu label, tags, IDML value).
pub const FIGURES: &[(&str, &str, &[&str], &str)] = &[
    ("tabularLining", "Tabular Lining", &["tnum", "lnum"], "TabularLining"),
    ("proportionalOldstyle", "Proportional Oldstyle", &["pnum", "onum"], "ProportionalOldstyle"),
    ("proportionalLining", "Proportional Lining", &["pnum", "lnum"], "ProportionalLining"),
    ("tabularOldstyle", "Tabular Oldstyle", &["tnum", "onum"], "TabularOldstyle"),
    ("default", "Default Figure Style", &[], "Default"),
];

/// Features shaping turns on by itself: "off" is an explicit `-tag`.
fn default_on(tag: &str) -> bool {
    matches!(tag, "calt" | "liga" | "locl" | "mark")
}

pub fn is_on(list: &[String], tag: &str) -> bool {
    if default_on(tag) { !list.iter().any(|t| t.strip_prefix('-') == Some(tag)) } else { list.iter().any(|t| t == tag) }
}

pub fn set(list: &mut Vec<String>, tag: &str, on: bool) {
    list.retain(|t| t != tag && t.strip_prefix('-') != Some(tag));
    if on != default_on(tag) {
        list.push(if on { tag.to_string() } else { format!("-{tag}") });
    }
}

/// The figure style id of a tag list ("default" when none matches).
pub fn figures(list: &[String]) -> &'static str {
    FIGURES.iter().find(|(_, _, tags, _)| !tags.is_empty() && tags.iter().all(|t| list.iter().any(|x| x == t))).map_or("default", |f| f.0)
}

pub fn set_figures(list: &mut Vec<String>, id: &str) -> bool {
    let Some((_, _, tags, _)) = FIGURES.iter().find(|f| f.0 == id) else { return false };
    list.retain(|t| !matches!(t.as_str(), "tnum" | "pnum" | "lnum" | "onum"));
    list.extend(tags.iter().map(ToString::to_string));
    true
}

/// Stylistic sets 1–20 as a bit mask (bit 0 = ss01), IDML's `OTFStylisticSets`.
pub fn stylistic_sets(list: &[String]) -> u32 {
    list.iter().filter_map(|t| t.strip_prefix("ss")?.parse::<u32>().ok()).filter(|n| (1..=20).contains(n)).fold(0, |m, n| m | 1 << (n - 1))
}

pub fn set_stylistic_sets(list: &mut Vec<String>, mask: u32) {
    list.retain(|t| !(t.len() == 4 && t.starts_with("ss") && t[2..].parse::<u32>().is_ok()));
    list.extend((1..=20).filter(|n| mask & (1 << (n - 1)) != 0).map(|n| format!("ss{n:02}")));
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn toggles_figures_and_sets() {
        let mut l: Vec<String> = vec![];
        assert!(is_on(&l, "calt") && !is_on(&l, "dlig"));
        set(&mut l, "dlig", true);
        set(&mut l, "calt", false);
        assert_eq!(l, ["dlig", "-calt"]);
        set(&mut l, "calt", true);
        assert_eq!(l, ["dlig"]);
        assert!(set_figures(&mut l, "tabularOldstyle"));
        assert_eq!(figures(&l), "tabularOldstyle");
        set_figures(&mut l, "default");
        assert_eq!(figures(&l), "default");
        set_stylistic_sets(&mut l, 0b101);
        assert_eq!(stylistic_sets(&l), 0b101);
        assert!(l.contains(&"ss03".to_string()));
    }
}