vectorcraft/crates/svg/tests/text_layout.rs

//! Laid-out type in SVG: every line of area type is its own positioned `<tspan>`, rich text keeps
//! its leading, baseline shift, scaling and kerning, and a renderer with the same font draws the
//! export where the canvas draws the text.
// Integration tests: unwrapping and panicking on failure is fine here, unlike in shipped code (AGENTS.md › Robustness).
#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]

use std::sync::Arc;

use vectorcraft_color::{Color, Paint};
use vectorcraft_doc::{CharStyle, Document, Justify, Node, NodeKind, TextKind, TextObject, TextRun};
use vectorcraft_geom::{Affine, BezPath, PathData, Point, Rect, shapes};
use vectorcraft_svg::{ExportOptions, export};
use vectorcraft_testkit::raster::{assert_similar, render_artboard};

fn style(size: f64) -> CharStyle {
    CharStyle { size, fill: Paint::solid(Color::BLACK), ..CharStyle::default() }
}

/// Area type `w` wide at (20, 20) in a 300 × 200 document.
fn area_doc(runs: Vec<TextRun>, w: f64, justify: Justify) -> Document {
    let mut t = TextObject::point(Point::new(20.0, 20.0), "", style(12.0));
    t.runs = runs;
    t.kind = TextKind::Area { frame: shapes::rectangle(Rect::new(0.0, 0.0, w, 160.0)) };
    t.para.justify = justify;
    let mut d = Document::new(300.0, 200.0);
    let n = Node::new(d.alloc_id(), NodeKind::Text(Box::new(t)));
    let l = d.layers[0].id;
    d.insert(Some(l), 0, n).unwrap();
    d
}

fn run(text: &str, st: CharStyle) -> TextRun {
    TextRun { text: text.into(), style: st }
}

/// The `<tspan …>` start tags.
fn tspans(svg: &str) -> Vec<&str> {
    svg.match_indices("<tspan").map(|(i, _)| &svg[i..i + svg[i..].find('>').unwrap()]).collect()
}

fn attr(tag: &str, name: &str) -> Option<f64> {
    let k = format!(" {name}=\"");
    let i = tag.find(&k)? + k.len();
    tag[i..i + tag[i..].find('"')?].parse().ok()
}

#[test]
fn wrapped_lines_get_one_tspan_each() {
    let d = area_doc(vec![run("alpha beta gamma delta epsilon zeta", style(12.0))], 70.0, Justify::Left);
    let svg = export(&d, &ExportOptions::default());
    let tags = tspans(&svg);
    let ys: Vec<f64> = tags.iter().map(|t| attr(t, "y").expect("each line is placed")).collect();
    assert!(ys.len() >= 3, "the text wraps: {svg}");
    assert!(ys.windows(2).all(|w| w[1] > w[0]), "baselines go down: {ys:?}");
    // Auto leading: 120 % of the size between baselines.
    assert!((ys[1] - ys[0] - 14.4).abs() < 0.01, "{ys:?}");
    assert!(tags.iter().all(|t| attr(t, "x") == Some(0.0)), "left aligned at the frame's edge: {svg}");
    // Reading it back gives a line per baseline, starting at the first baseline.
    let back = vectorcraft_svg::import(&svg).unwrap();
    let text = back.layers[0].children().unwrap().iter().find_map(|n| if let NodeKind::Text(t) = &n.kind { Some(t.clone()) } else { None }).unwrap();
    assert_eq!(text.plain_text().lines().count(), ys.len(), "{:?}", text.plain_text());
    assert!((text.xf.translation().y - (20.0 + ys[0])).abs() < 0.01);
    // Centred lines are anchored at the frame's centre, so they stay centred in any font.
    let svg = export(&area_doc(vec![run("alpha beta gamma delta", style(12.0))], 70.0, Justify::Center), &ExportOptions::default());
    assert!(svg.contains("text-anchor=\"middle\""), "{svg}");
    assert!(tspans(&svg).iter().all(|t| (attr(t, "x").unwrap() - 35.0).abs() < 0.01), "{svg}");
    // Left-aligned (and justified) lines are placed absolutely.
    assert!(!export(&d, &ExportOptions::default()).contains("text-anchor"));
}

#[test]
fn rich_text_writes_spacing_shift_and_scale() {
    let shifted = CharStyle { baseline_shift: 4.0, ..style(12.0) };
    let wide = CharStyle { h_scale: 150.0, ..style(12.0) };
    let kerned = CharStyle { tracking: 50.0, kerning: Some(-20.0), ..style(12.0) };
    let tall = CharStyle { v_scale: 200.0, h_scale: 200.0, leading: Some(30.0), ..style(12.0) };
    let d = area_doc(
        vec![run("Base ", style(12.0)), run("up ", shifted), run("wide ", wide), run("kern\n", kerned), run("tall", tall)],
        280.0,
        Justify::Left,
    );
    let svg = export(&d, &ExportOptions::default());
    let tags = tspans(&svg);
    assert_eq!(tags.len(), 5, "{svg}");
    assert_eq!(attr(tags[1], "dy"), Some(-4.0), "baseline shift: {}", tags[1]);
    assert!(attr(tags[2], "textLength").is_some() && tags[2].contains("lengthAdjust=\"spacingAndGlyphs\""), "{}", tags[2]);
    assert!(tags[3].contains("letter-spacing=\"0.36\"") && tags[3].contains("font-kerning:none"), "tracking + kerning: {}", tags[3]);
    assert!(tags[4].contains("font-size=\"24\"") && attr(tags[4], "textLength").is_none(), "uniform scale is the size: {}", tags[4]);
    assert!((attr(tags[4], "y").unwrap() - attr(tags[0], "y").unwrap() - 30.0).abs() < 0.01, "leading");
    // Segments on one baseline share its y; the shifted one is placed with dy.
    assert_eq!(attr(tags[1], "y"), attr(tags[0], "y"));
}

#[test]
fn fewer_tspans_writes_one_per_line() {
    let bold = CharStyle { font_style: "Bold".into(), ..style(12.0) };
    let runs = vec![run("one ", style(12.0)), run("two", bold), run(" three\nfour", style(12.0))];
    let d = area_doc(runs, 280.0, Justify::Left);
    let full = export(&d, &ExportOptions::default());
    let fewer = export(&d, &ExportOptions { fewer_tspans: true, ..Default::default() });
    let placed = |s: &str| tspans(s).iter().filter(|t| attr(t, "y").is_some()).count();
    assert_eq!(placed(&full), 4, "{full}");
    assert_eq!(placed(&fewer), 2, "one positioned tspan per line: {fewer}");
    assert!(fewer.contains("font-weight=\"bold\""), "style changes stay: {fewer}");
    assert!(fewer.len() < full.len());
}

#[test]
fn justified_lines_place_each_word() {
    let d = area_doc(vec![run("aa bb cc dd ee ff gg hh ii jj kk ll", style(12.0))], 90.0, Justify::JustifyLeft);
    let svg = export(&d, &ExportOptions::default());
    let first_line_y = attr(tspans(&svg)[0], "y").unwrap();
    let words = tspans(&svg).iter().filter(|t| attr(t, "y") == Some(first_line_y)).count();
    assert!(words >= 3, "{svg}");
}

/// Glyph outlines of every text a usvg (with the bundled font) lays out from `svg`, in SVG
/// user space.
fn viewer_outlines(svg: &str) -> Vec<BezPath> {
    let mut db = usvg::fontdb::Database::new();
    db.load_font_data(std::fs::read(concat!(env!("CARGO_MANIFEST_DIR"), "/../../assets/fonts/SourceSans3-Regular.ttf")).unwrap());
    let opt = usvg::Options { fontdb: Arc::new(db), ..Default::default() };
    let tree = usvg::Tree::from_str(svg, &opt).unwrap();
    fn walk(g: &usvg::Group, out: &mut Vec<BezPath>) {
        for n in g.children() {
            match n {
                usvg::Node::Group(g) => walk(g, out),
                usvg::Node::Text(t) => walk(t.flattened(), out),
                usvg::Node::Path(p) => {
                    let m = p.abs_transform();
                    let m = Affine::new([m.sx as f64, m.ky as f64, m.kx as f64, m.sy as f64, m.tx as f64, m.ty as f64]);
                    let mut bp = BezPath::new();
                    for s in p.data().segments() {
                        use usvg::tiny_skia_path::PathSegment as S;
                        let pt = |q: usvg::tiny_skia_path::Point| m * Point::new(q.x as f64, q.y as f64);
                        match s {
                            S::MoveTo(a) => bp.move_to(pt(a)),
                            S::LineTo(a) => bp.line_to(pt(a)),
                            S::QuadTo(a, b) => bp.quad_to(pt(a), pt(b)),
                            S::CubicTo(a, b, c) => bp.curve_to(pt(a), pt(b), pt(c)),
                            S::Close => bp.close_path(),
                        }
                    }
                    out.push(bp);
                }
                usvg::Node::Image(_) => {}
            }
        }
    }
    let mut out = vec![];
    walk(tree.root(), &mut out);
    out
}

#[test]
fn a_viewer_draws_the_text_where_the_canvas_does() {
    // With a tab every line is placed absolutely; without one, centred and right-aligned lines are
    // anchored, and a baseline shift mid-line is undone by the next run.
    for (sep, shift) in [("	", 0.0), (" ", 3.0)] {
        let second = |fill: Color| CharStyle { fill: Paint::solid(fill), baseline_shift: shift, ..style(14.0) };
        let runs = |second: CharStyle| {
            vec![
                run("The quick brown fox jumps over the lazy dog. ", style(14.0)),
                run(&format!("Pack my box{sep}with"), second),
                run(" five dozen jugs.", style(14.0)),
            ]
        };
        for justify in [Justify::Left, Justify::Center, Justify::Right] {
            for fewer_tspans in [false, true] {
                let o = ExportOptions { fewer_tspans, ..Default::default() };
                let svg = export(&area_doc(runs(second(Color::rgb(0.8, 0.0, 0.0))), 200.0, justify), &o);
                assert!(svg.contains("fill=\"#cc0000\""), "{svg}");
                // The viewer's glyphs as black shapes, against the canvas drawing the text all black.
                let mut viewer = Document::new(300.0, 200.0);
                let l = viewer.layers[0].id;
                let outlines = viewer_outlines(&svg);
                assert!(outlines.iter().map(|b| b.elements().len()).sum::<usize>() > 200, "the viewer laid the text out");
                for bp in outlines {
                    let ap = vectorcraft_doc::Appearance::basic(Paint::solid(Color::BLACK), Paint::None, 0.0);
                    let n = Node::path(viewer.alloc_id(), PathData::from_bezpath(&bp), ap);
                    viewer.insert(Some(l), usize::MAX, n).unwrap();
                }
                let canvas = area_doc(runs(second(Color::BLACK)), 200.0, justify);
                assert_similar(&render_artboard(&canvas), &render_artboard(&viewer), 40.0, 0.01);
            }
        }
    }
}