vectorcraft/crates/brush/src/tests.rs

use vectorcraft_color::{Color, Paint};
use vectorcraft_doc::{Appearance, Document, Node, NodeId, NodeKind, StrokeLayer};
use vectorcraft_geom::{BezPath, Point, Rect, shapes};

use super::*;

fn line(x0: f64, y0: f64, x1: f64, y1: f64) -> BezPath {
    let mut bp = BezPath::new();
    bp.move_to((x0, y0));
    bp.line_to((x1, y1));
    bp
}

fn stroke(w: f64) -> StrokeLayer {
    StrokeLayer::new(Paint::solid(Color::rgb(1.0, 0.0, 0.0)), w)
}

fn calli(angle: f64, roundness: f64, size: f64) -> Brush {
    Brush { name: "c".into(), kind: BrushKind::Calligraphic(Calligraphic { angle, roundness, size, ..Default::default() }) }
}

fn bounds(nodes: &[Node]) -> Rect {
    nodes.iter().fold(None, |a, n| vectorcraft_geom::union_opt(a, n.geometric_bounds())).unwrap()
}

fn near(a: f64, b: f64, tol: f64) -> bool {
    (a - b).abs() <= tol
}

fn all_points(n: &Node, out: &mut Vec<Point>) {
    n.walk(&mut |c| {
        if let Some(p) = c.path_data() {
            out.extend(p.anchors().map(|(_, _, a)| a.p));
        }
    });
}

#[test]
fn calligraphic_vertical_nib_is_full_width_across_horizontal_stroke() {
    let out = stroke_pieces(&Document::new(1.0, 1.0), &calli(90.0, 20.0, 10.0), &line(0.0, 0.0, 100.0, 0.0), &stroke(1.0));
    assert_eq!(out.len(), 1);
    let b = bounds(&out);
    assert!(near(b.height(), 10.0, 0.05), "{b:?}");
    assert!(near(b.x0, -1.0, 0.05) && near(b.x1, 101.0, 0.05), "caps add half the minor axis: {b:?}");
}

#[test]
fn calligraphic_flat_nib_is_thin_along_its_angle() {
    let out = stroke_pieces(&Document::new(1.0, 1.0), &calli(0.0, 20.0, 10.0), &line(0.0, 0.0, 100.0, 0.0), &stroke(1.0));
    assert!(near(bounds(&out).height(), 2.0, 0.05), "{:?}", bounds(&out));
}

#[test]
fn calligraphic_width_at_45_degrees_matches_ellipse_support() {
    let (a, b) = (5.0_f64, 1.0_f64);
    let out = stroke_pieces(&Document::new(1.0, 1.0), &calli(45.0, 20.0, 10.0), &line(0.0, 0.0, 100.0, 0.0), &stroke(1.0));
    let expect = 2.0 * ((a * a + b * b) / 2.0).sqrt();
    assert!(near(bounds(&out).height(), expect, 0.05), "{} vs {expect}", bounds(&out).height());
    // A vertical stroke with the same nib has the same width (45° is symmetric).
    let v = stroke_pieces(&Document::new(1.0, 1.0), &calli(45.0, 20.0, 10.0), &line(0.0, 0.0, 0.0, 100.0), &stroke(1.0));
    assert!(near(bounds(&v).width(), expect, 0.05));
}

#[test]
fn calligraphic_scales_with_stroke_weight() {
    let out = stroke_pieces(&Document::new(1.0, 1.0), &calli(90.0, 100.0, 3.0), &line(0.0, 0.0, 100.0, 0.0), &stroke(2.0));
    assert!(near(bounds(&out).height(), 6.0, 0.05));
}

#[test]
fn round_nib_is_direction_independent() {
    let out = stroke_pieces(&Document::new(1.0, 1.0), &calli(0.0, 100.0, 4.0), &line(0.0, 0.0, 60.0, 80.0), &stroke(1.0));
    let b = bounds(&out);
    // Round caps: the bounds grow by the radius on every side.
    assert!(near(b.x0, -2.0, 0.05) && near(b.y1, 82.0, 0.05), "{b:?}");
}

#[test]
fn closed_calligraphic_makes_a_ring() {
    let bp = shapes::ellipse(Rect::new(0.0, 0.0, 100.0, 100.0)).to_bezpath();
    let out = stroke_pieces(&Document::new(1.0, 1.0), &calli(0.0, 100.0, 6.0), &bp, &stroke(1.0));
    let pd = out[0].path_data().unwrap();
    assert_eq!(pd.subpaths.len(), 2);
    let poly_area = |sp: &vectorcraft_geom::SubPath| {
        let a = &sp.anchors;
        (0..a.len()).map(|i| a[i].p.x * a[(i + 1) % a.len()].p.y - a[(i + 1) % a.len()].p.x * a[i].p.y).sum::<f64>() / 2.0
    };
    let (outer, inner) = (poly_area(&pd.subpaths[0]), poly_area(&pd.subpaths[1]));
    assert!(outer * inner < 0.0, "opposite windings make a hole");
    let area = (outer.abs() - inner.abs()).abs();
    let expect = std::f64::consts::PI * (53.0f64.powi(2) - 47.0f64.powi(2));
    assert!((area - expect).abs() / expect < 0.03, "{area} vs {expect}");
}

fn art_brush(art: Node, scale: ArtScale) -> Brush {
    Brush { name: "a".into(), kind: BrushKind::Art(ArtBrush { art, scale, colorization: Colorization::None, ..Default::default() }) }
}

fn rect_art(w: f64, h: f64) -> Node {
    Node::path(NodeId(0), shapes::rectangle(Rect::new(0.0, -h / 2.0, w, h / 2.0)), Appearance::basic(Paint::solid(Color::BLACK), Paint::None, 0.0))
}

#[test]
fn art_brush_stretches_to_path_length() {
    let out =
        stroke_pieces(&Document::new(1.0, 1.0), &art_brush(rect_art(10.0, 4.0), ArtScale::Stretch), &line(20.0, 50.0, 220.0, 50.0), &stroke(1.0));
    let b = bounds(&out);
    assert!(near(b.x0, 20.0, 1e-6) && near(b.x1, 220.0, 1e-6), "{b:?}");
    assert!(near(b.height(), 4.0, 1e-6));
    // 3 pt stroke → 3× wider.
    let out =
        stroke_pieces(&Document::new(1.0, 1.0), &art_brush(rect_art(10.0, 4.0), ArtScale::Stretch), &line(20.0, 50.0, 220.0, 50.0), &stroke(3.0));
    assert!(near(bounds(&out).height(), 12.0, 1e-6));
}

#[test]
fn art_brush_arc_length_mapping_is_linear() {
    // A marker square at art x ∈ [5, 6] of a 10 wide art lands at 50..60 % of the path.
    let marker =
        Node::path(NodeId(0), shapes::rectangle(Rect::new(5.0, -1.0, 6.0, 1.0)), Appearance::basic(Paint::solid(Color::BLACK), Paint::None, 0.0));
    let frame = rect_art(10.0, 2.0);
    let mut spacer = frame.clone();
    spacer.appearance = Appearance::default().into();
    let art = Node::group(NodeId(0), vec![std::sync::Arc::new(spacer), std::sync::Arc::new(marker)]);
    let out = stroke_pieces(&Document::new(1.0, 1.0), &art_brush(art, ArtScale::Stretch), &line(0.0, 0.0, 300.0, 0.0), &stroke(1.0));
    let g = &out[0];
    let m = g.children().unwrap()[1].geometric_bounds().unwrap();
    assert!(near(m.x0, 150.0, 1e-6) && near(m.x1, 180.0, 1e-6), "{m:?}");
}

#[test]
fn art_brush_proportional_keeps_aspect() {
    let out =
        stroke_pieces(&Document::new(1.0, 1.0), &art_brush(rect_art(100.0, 4.0), ArtScale::Proportional), &line(0.0, 0.0, 200.0, 0.0), &stroke(1.0));
    assert!(near(bounds(&out).height(), 8.0, 1e-6));
}

#[test]
fn art_brush_between_guides_keeps_ends() {
    // Head (last 20 % of a 100 pt art) keeps its 20 pt length on a 300 pt path.
    let head =
        Node::path(NodeId(0), shapes::rectangle(Rect::new(80.0, -4.0, 100.0, 4.0)), Appearance::basic(Paint::solid(Color::BLACK), Paint::None, 0.0));
    let shaft = rect_art(80.0, 2.0);
    let art = Node::group(NodeId(0), vec![std::sync::Arc::new(shaft), std::sync::Arc::new(head)]);
    let out = stroke_pieces(
        &Document::new(1.0, 1.0),
        &art_brush(art, ArtScale::BetweenGuides { start: 0.0, end: 0.8 }),
        &line(0.0, 0.0, 300.0, 0.0),
        &stroke(1.0),
    );
    let h = out[0].children().unwrap()[1].geometric_bounds().unwrap();
    assert!(near(h.x0, 280.0, 1e-6) && near(h.x1, 300.0, 1e-6), "{h:?}");
}

#[test]
fn art_brush_overlap_splits_at_corners() {
    let mut bp = BezPath::new();
    bp.move_to((0.0, 0.0));
    bp.line_to((100.0, 0.0));
    bp.line_to((100.0, 100.0));
    let brush = |overlap: bool| Brush {
        name: "a".into(),
        kind: BrushKind::Art(ArtBrush {
            art: rect_art(10.0, 4.0),
            scale: ArtScale::Stretch,
            overlap,
            colorization: Colorization::None,
            ..Default::default()
        }),
    };
    let one = stroke_pieces(&Document::new(1.0, 1.0), &brush(false), &bp, &stroke(1.0));
    let two = stroke_pieces(&Document::new(1.0, 1.0), &brush(true), &bp, &stroke(1.0));
    assert_eq!(one.len(), 1, "one bent copy along the whole path");
    assert_eq!(two.len(), 2, "one copy per run between corners");
}

#[test]
fn art_brush_follows_curves() {
    let bp = shapes::ellipse(Rect::new(0.0, 0.0, 200.0, 200.0)).to_bezpath();
    let mut bp_open = BezPath::new();
    // Upper half of the circle, as an open path.
    for (i, el) in bp.elements().iter().enumerate() {
        if i < 3 {
            bp_open.push(*el);
        }
    }
    let out = stroke_pieces(&Document::new(1.0, 1.0), &art_brush(rect_art(10.0, 4.0), ArtScale::Stretch), &bp_open, &stroke(1.0));
    let mut pts = vec![];
    all_points(&out[0], &mut pts);
    assert!(pts.len() > 40, "long edges are subdivided so they bend: {}", pts.len());
    for p in pts {
        let r = p.distance(Point::new(100.0, 100.0));
        assert!((r - 100.0).abs() <= 2.0 + 0.3, "point {p:?} is {r} from the centre");
    }
}

fn scatter_brush(spacing: f64) -> Brush {
    Brush {
        name: "s".into(),
        kind: BrushKind::Scatter(Scatter {
            art: rect_art(10.0, 4.0),
            spacing: (spacing, spacing),
            colorization: Colorization::None,
            ..Default::default()
        }),
    }
}

#[test]
fn scatter_count_and_spacing() {
    let out = stroke_pieces(&Document::new(1.0, 1.0), &scatter_brush(100.0), &line(0.0, 0.0, 100.0, 0.0), &stroke(1.0));
    assert_eq!(out.len(), 10);
    let centres: Vec<f64> = out.iter().map(|n| n.geometric_bounds().unwrap().center().x).collect();
    for (i, c) in centres.iter().enumerate() {
        assert!(near(*c, 5.0 + 10.0 * i as f64, 1e-6), "{centres:?}");
    }
    let out = stroke_pieces(&Document::new(1.0, 1.0), &scatter_brush(200.0), &line(0.0, 0.0, 100.0, 0.0), &stroke(1.0));
    assert_eq!(out.len(), 5);
}

#[test]
fn scatter_is_deterministic_and_randomised() {
    let b = Brush {
        name: "r".into(),
        kind: BrushKind::Scatter(Scatter {
            art: rect_art(4.0, 4.0),
            size: (50.0, 150.0),
            scatter: (-100.0, 100.0),
            rotation: (-90.0, 90.0),
            ..Default::default()
        }),
    };
    let p = line(0.0, 0.0, 300.0, 0.0);
    let a1 = stroke_pieces(&Document::new(1.0, 1.0), &b, &p, &stroke(1.0));
    let a2 = stroke_pieces(&Document::new(1.0, 1.0), &b, &p, &stroke(1.0));
    assert_eq!(a1, a2);
    let ys: Vec<f64> = a1.iter().map(|n| n.geometric_bounds().unwrap().center().y).collect();
    assert!(ys.iter().any(|y| y.abs() > 0.5), "scatter offsets copies: {ys:?}");
}

fn pattern_brush(fit: PatternFit, corners: bool) -> Brush {
    let side = rect_art(10.0, 4.0);
    let corner =
        Node::path(NodeId(0), shapes::ellipse(Rect::new(0.0, -3.0, 6.0, 3.0)), Appearance::basic(Paint::solid(Color::BLACK), Paint::None, 0.0));
    Brush {
        name: "p".into(),
        kind: BrushKind::Pattern(PatternBrush {
            side,
            outer_corner: corners.then(|| corner.clone()),
            inner_corner: corners.then_some(corner),
            fit,
            colorization: Colorization::None,
            ..Default::default()
        }),
    }
}

#[test]
fn pattern_tile_count_by_fit() {
    let p = line(0.0, 0.0, 100.0, 0.0);
    assert_eq!(stroke_pieces(&Document::new(1.0, 1.0), &pattern_brush(PatternFit::Stretch, false), &p, &stroke(1.0)).len(), 10);
    let p2 = line(0.0, 0.0, 104.0, 0.0);
    let st = stroke_pieces(&Document::new(1.0, 1.0), &pattern_brush(PatternFit::Stretch, false), &p2, &stroke(1.0));
    assert_eq!(st.len(), 10);
    assert!(near(bounds(&st).width(), 104.0, 1e-6), "stretch fills the path exactly");
    let sp = stroke_pieces(&Document::new(1.0, 1.0), &pattern_brush(PatternFit::AddSpace, false), &line(0.0, 0.0, 109.0, 0.0), &stroke(1.0));
    assert_eq!(sp.len(), 10);
    assert!(near(sp[0].geometric_bounds().unwrap().width(), 10.0, 1e-6), "add space keeps tile size");
    assert_eq!(stroke_pieces(&Document::new(1.0, 1.0), &pattern_brush(PatternFit::Stretch, false), &p, &stroke(2.0)).len(), 5);
}

#[test]
fn pattern_places_corner_tiles() {
    let sq = shapes::rectangle(Rect::new(0.0, 0.0, 100.0, 100.0)).to_bezpath();
    let out = stroke_pieces(&Document::new(1.0, 1.0), &pattern_brush(PatternFit::Stretch, true), &sq, &stroke(1.0));
    let corners = out
        .iter()
        .filter(
            |n| matches!(&n.kind, NodeKind::Path { path, .. } if path.subpaths[0].anchors.len() == 4 && n.geometric_bounds().unwrap().width() < 7.0),
        )
        .count();
    assert_eq!(corners, 4);
    // Sides lose half a corner tile at each end: 94 pt per side → 9 tiles each.
    assert_eq!(out.len() - corners, 36);
}

#[test]
fn bristle_makes_translucent_strands() {
    let b = Brush { name: "b".into(), kind: BrushKind::Bristle(Bristle::default()) };
    let out = stroke_pieces(&Document::new(1.0, 1.0), &b, &line(0.0, 0.0, 200.0, 0.0), &stroke(1.0));
    assert!(out.len() >= 5, "{}", out.len());
    assert!(out.iter().all(|n| n.opacity < 1.0 && n.opacity > 0.0));
    let bb = bounds(&out);
    assert!(bb.height() <= 6.0 * 1.3 && bb.height() >= 3.0, "{bb:?}");
}

#[test]
fn tints_colorization_uses_stroke_colour() {
    let b = art_brush(rect_art(10.0, 4.0), ArtScale::Stretch);
    let BrushKind::Art(mut a) = b.kind else { panic!("not an art brush") };
    a.colorization = Colorization::Tints;
    let b = Brush { name: "t".into(), kind: BrushKind::Art(a) };
    let out = stroke_pieces(&Document::new(1.0, 1.0), &b, &line(0.0, 0.0, 50.0, 0.0), &stroke(1.0));
    assert_eq!(out[0].appearance.fill_paint(), Paint::solid(Color::rgb(1.0, 0.0, 0.0)));
    let mut white = rect_art(1.0, 1.0);
    white.appearance.set_fill(Paint::solid(Color::WHITE));
    colorize(&mut white, Colorization::Tints, &Paint::solid(Color::rgb(1.0, 0.0, 0.0)));
    assert_eq!(white.appearance.fill_paint().color().unwrap().to_rgb(), [1.0, 1.0, 1.0]);
}

/// Point type at (0, 0) whose characters are painted `fill` and `stroke` (1 pt wide).
fn type_art(fill: Paint, stroke: Paint) -> Node {
    use vectorcraft_doc::{CharStyle, TextObject};
    let style = CharStyle { fill, stroke, stroke_width: 1.0, ..CharStyle::default() };
    Node::new(NodeId(0), NodeKind::Text(Box::new(TextObject::point(Point::new(0.0, 0.0), "Ag", style))))
}

/// The characters' fills and strokes of every piece of type in `nodes`.
fn run_paints(nodes: &[Node]) -> Vec<(Paint, Paint)> {
    let mut out = vec![];
    for n in nodes {
        n.walk(&mut |c| {
            if let NodeKind::Text(t) = &c.kind {
                out.extend(t.runs.iter().map(|r| (r.style.fill.clone(), r.style.stroke.clone())));
            }
        });
    }
    out
}

/// A scatter brush's colorization recolors the type in its art as it recolors the art's paths.
#[test]
fn scatter_colorization_recolors_type() {
    let red = Paint::solid(Color::rgb(1.0, 0.0, 0.0));
    let blue = StrokeLayer::new(Paint::solid(Color::rgb(0.0, 0.0, 1.0)), 1.0);
    let mut path = rect_art(10.0, 4.0);
    path.appearance.set_fill(red.clone());
    let art = Node::group(NodeId(0), vec![Arc::new(path), Arc::new(type_art(red.clone(), red.clone()))]);
    let b = Brush { name: "s".into(), kind: BrushKind::Scatter(Scatter { art, colorization: Colorization::Tints, ..Default::default() }) };
    let out = stroke_pieces(&Document::new(1.0, 1.0), &b, &line(0.0, 0.0, 100.0, 0.0), &blue);
    assert!(!out.is_empty());
    let path_fill = out[0].children().unwrap()[0].appearance.fill_paint();
    assert_ne!(path_fill, red);
    let paints = run_paints(&out);
    assert_eq!(paints.len(), out.len());
    assert!(paints.iter().all(|p| *p == (path_fill.clone(), path_fill.clone())), "{paints:?}");
    // Black type takes the stroke color itself.
    let black = Paint::solid(Color::BLACK);
    let b = Brush {
        name: "s".into(),
        kind: BrushKind::Scatter(Scatter { art: type_art(black.clone(), black), colorization: Colorization::Tints, ..Default::default() }),
    };
    let out = stroke_pieces(&Document::new(1.0, 1.0), &b, &line(0.0, 0.0, 100.0, 0.0), &blue);
    assert!(!out.is_empty());
    assert!(run_paints(&out).iter().all(|p| *p == (blue.paint.clone(), blue.paint.clone())));
}

/// The Symbol Stainer mixes the characters' strokes of type toward the stain, as it mixes their fills.
#[test]
fn stain_mixes_type_strokes_too() {
    let red = Paint::solid(Color::rgb(1.0, 0.0, 0.0));
    let blue = Color::rgb(0.0, 0.0, 1.0);
    let mut art = type_art(red.clone(), red);
    tint_node(&mut art, &blue, 1.0);
    assert_eq!(run_paints(&[art]), [(Paint::solid(blue), Paint::solid(blue))]);
}

#[test]
fn library_defaults_store_and_find() {
    let mut d = Document::new(100.0, 100.0);
    let lib = library(&d);
    assert!(lib.len() >= 10);
    for kind in ["calligraphic", "scatter", "art", "pattern", "bristle"] {
        assert!(lib.iter().any(|b| b.kind.type_id() == kind), "{kind}");
    }
    assert!(find(&d, "Chain").is_some());
    let mut lib = lib;
    lib.retain(|b| b.name != "Chain");
    store(&mut d, &lib);
    assert!(find(&d, "Chain").is_none());
    assert_eq!(library(&d).len(), lib.len());
    assert_eq!(unique_name(&lib, "Arrow"), "Arrow 2");
}

#[test]
fn brushes_serde_round_trip() {
    let lib = defaults().to_vec();
    let s = serde_json::to_string(&lib).unwrap();
    let back: Vec<Brush> = serde_json::from_str(&s).unwrap();
    assert_eq!(back, lib);
    // Partial definitions fill in defaults.
    let b: Brush = serde_json::from_value(serde_json::json!({"name": "x", "type": "calligraphic", "angle": 30})).unwrap();
    assert_eq!(b.kind, BrushKind::Calligraphic(Calligraphic { angle: 30.0, ..Default::default() }));
}

#[test]
fn every_default_brush_draws_something() {
    let bp = preview_path(120.0, 24.0);
    for b in defaults() {
        let out = stroke_pieces(&Document::new(1.0, 1.0), b, &bp, &stroke(1.0));
        assert!(!out.is_empty(), "{}", b.name);
        let bb = bounds(&out);
        assert!(bb.width() > 50.0 && bb.width() < 200.0, "{}: {bb:?}", b.name);
    }
}

#[test]
fn expand_keeps_fill_and_adds_pieces() {
    let mut d = Document::new(200.0, 200.0);
    let mut ap = Appearance::basic(Paint::solid(Color::WHITE), Paint::solid(Color::BLACK), 1.0);
    ap.stroke_mut().unwrap().brush = Some("3 pt. Round".into());
    let n = Node::path(d.alloc_id(), shapes::rectangle(Rect::new(10.0, 10.0, 90.0, 90.0)), ap);
    assert!(has_brush(&n));
    let g = expand(&d, &n).unwrap();
    let ch = g.children().unwrap();
    assert_eq!(ch.len(), 2);
    assert!(ch[0].appearance.stroke().is_none() && !ch[0].appearance.fill_paint().is_none());
    assert_eq!(ch[1].appearance.fill_paint(), Paint::solid(Color::BLACK));
    let b = ch[1].geometric_bounds().unwrap();
    assert!(near(b.x0, 8.5, 0.05) && near(b.x1, 91.5, 0.05), "{b:?}");
    let plain = Node::path(NodeId(9), shapes::rectangle(Rect::new(0.0, 0.0, 1.0, 1.0)), Appearance::default_art());
    assert!(expand(&d, &plain).is_none());
}

/// A Calligraphic brush (round nib) whose size follows the pen pressure by `var` either way.
fn pressure_calli(size: f64, var: f64) -> Brush {
    let c = Calligraphic {
        size,
        variation: [0.0, 0.0, var],
        modes: Some([Variation::Fixed, Variation::Fixed, Variation::Pressure]),
        ..Default::default()
    };
    Brush { name: "p".into(), kind: BrushKind::Calligraphic(c) }
}

/// The stroke's half-width (largest |y|) among outline points with x in `x0..x1`.
fn half_width(nodes: &[Node], x0: f64, x1: f64) -> f64 {
    let mut pts = vec![];
    for n in nodes {
        all_points(n, &mut pts);
    }
    pts.iter().filter(|p| p.x >= x0 && p.x <= x1).map(|p| p.y.abs()).fold(0.0, f64::max)
}

fn pressed(points: Vec<(f64, f64)>) -> StrokeLayer {
    StrokeLayer { pressure: Some(vectorcraft_doc::PressureProfile { points }), ..stroke(1.0) }
}

/// #852: with Size on Pressure the nib goes from size − variation at the lightest pressure to
/// size + variation at the heaviest, along the stroke where the pen pressed.
#[test]
fn pressure_maps_to_size_along_the_stroke() {
    let b = pressure_calli(10.0, 4.0);
    let light_to_heavy = pressed(vec![(0.0, 0.0), (1.0, 1.0)]);
    let out = stroke_pieces(&Document::new(1.0, 1.0), &b, &line(0.0, 0.0, 100.0, 0.0), &light_to_heavy);
    // Lightest: 6 pt (half 3); heaviest: 14 pt (half 7); in between the pressure there.
    assert!(near(half_width(&out, 0.5, 1.5), 3.0, 0.1), "{}", half_width(&out, 0.5, 1.5));
    assert!(near(half_width(&out, 98.5, 99.5), 7.0, 0.1), "{}", half_width(&out, 98.5, 99.5));
    assert!(near(half_width(&out, 49.5, 50.5), 5.0, 0.1), "{}", half_width(&out, 49.5, 50.5));
    // The stroke weight scales it.
    let heavy = StrokeLayer { width: 2.0, ..light_to_heavy };
    let out = stroke_pieces(&Document::new(1.0, 1.0), &b, &line(0.0, 0.0, 100.0, 0.0), &heavy);
    assert!(near(half_width(&out, 98.5, 99.5), 14.0, 0.2));
    // No pressure recorded (a mouse, or a path the brush was applied to): the size itself.
    let out = stroke_pieces(&Document::new(1.0, 1.0), &b, &line(0.0, 0.0, 100.0, 0.0), &stroke(1.0));
    assert!(near(bounds(&out).height(), 10.0, 0.05), "{:?}", bounds(&out));
    // Kept within the valid range: 2 ± 4 never goes below nothing.
    let out = stroke_pieces(&Document::new(1.0, 1.0), &pressure_calli(2.0, 4.0), &line(0.0, 0.0, 100.0, 0.0), &pressed(vec![(0.0, 0.0), (1.0, 0.0)]));
    assert!(!out.is_empty() && bounds(&out).height() < 0.2, "{:?}", bounds(&out));
}

/// Angle and roundness follow the pressure the same way, clamped to their ranges.
#[test]
fn pressure_varies_angle_and_roundness() {
    let c = |modes| Calligraphic { angle: 0.0, roundness: 60.0, size: 10.0, variation: [90.0, 60.0, 0.0], modes: Some(modes) };
    let horizontal = line(0.0, 0.0, 100.0, 0.0);
    let draw = |c: Calligraphic, p: f64| {
        let b = Brush { name: "a".into(), kind: BrushKind::Calligraphic(c) };
        bounds(&stroke_pieces(&Document::new(1.0, 1.0), &b, &horizontal, &pressed(vec![(0.0, p), (1.0, p)]))).height()
    };
    use Variation::{Fixed, Pressure};
    // Angle 0 ± 90: heavy pressure stands the flat nib up across the stroke.
    assert!(near(draw(c([Pressure, Fixed, Fixed]), 0.5), 6.0, 0.05));
    assert!(near(draw(c([Pressure, Fixed, Fixed]), 1.0), 10.0, 0.05));
    // Roundness 60 ± 60, kept within 1..100: light is a hairline, heavy is round.
    let vertical = Calligraphic { angle: 90.0, ..c([Fixed, Pressure, Fixed]) };
    let wide = |p| {
        let b = Brush { name: "r".into(), kind: BrushKind::Calligraphic(vertical.clone()) };
        bounds(&stroke_pieces(&Document::new(1.0, 1.0), &b, &line(0.0, 0.0, 0.0, 100.0), &pressed(vec![(0.0, p), (1.0, p)]))).width()
    };
    assert!(near(wide(0.0), 0.1, 0.05), "{}", wide(0.0));
    assert!(near(wide(1.0), 10.0, 0.05), "{}", wide(1.0));
}

/// Brushes saved before the variation modes keep their look: a variation means Random, none
/// means Fixed, and they are written back without modes.
#[test]
fn brushes_without_modes_vary_randomly_as_before() {
    let old: Brush = serde_json::from_value(serde_json::json!({"name": "x", "type": "calligraphic", "size": 8, "variation": [0, 0, 3]})).unwrap();
    let BrushKind::Calligraphic(c) = &old.kind else { panic!() };
    assert_eq!(c.modes, None);
    assert_eq!(c.modes(), [Variation::Fixed, Variation::Fixed, Variation::Random]);
    assert!(!c.uses_pressure());
    assert!(serde_json::to_value(&old).unwrap().get("modes").is_none(), "written back as it was");
    // The same strokes as the brush with its modes spelled out.
    let explicit = Brush {
        kind: BrushKind::Calligraphic(Calligraphic { modes: Some([Variation::Fixed, Variation::Fixed, Variation::Random]), ..c.clone() }),
        ..old.clone()
    };
    let bp = preview_path(120.0, 24.0);
    assert_eq!(
        stroke_pieces(&Document::new(1.0, 1.0), &old, &bp, &stroke(1.0)),
        stroke_pieces(&Document::new(1.0, 1.0), &explicit, &bp, &stroke(1.0))
    );
    // Fixed ignores the variation; Random still draws a different size per stroke.
    let fixed = Brush { kind: BrushKind::Calligraphic(Calligraphic { modes: Some([Variation::Fixed; 3]), ..c.clone() }), ..old.clone() };
    assert!(near(bounds(&stroke_pieces(&Document::new(1.0, 1.0), &fixed, &line(0.0, 0.0, 100.0, 0.0), &stroke(1.0))).height(), 8.0, 0.05));
    // Recorded pressure changes nothing for a brush that doesn't use it.
    assert_eq!(
        stroke_pieces(&Document::new(1.0, 1.0), &old, &bp, &stroke(1.0)),
        stroke_pieces(&Document::new(1.0, 1.0), &old, &bp, &pressed(vec![(0.0, 0.0), (1.0, 1.0)]))
    );
    // Modes are saved by name.
    assert_eq!(serde_json::to_value(Variation::ALL).unwrap(), serde_json::json!(["fixed", "random", "pressure"]));
    assert!(Variation::ALL.iter().all(|v| Variation::parse(v.id()) == Some(*v)));
}

/// Junk definitions and pressure never panic and never draw non-finite art.
#[test]
fn junk_pressure_brushes_draw_finite_art() {
    let bp = preview_path(120.0, 24.0);
    for (size, var) in [(1e308, 1e308), (-1e308, 1e308), (0.0, -1e308), (f64::MAX, f64::MAX)] {
        for profile in [vec![], vec![(0.0, 2.0), (0.0, -1.0), (5.0, 0.5)], vec![(1.0, 1.0), (0.0, 0.0)]] {
            let out = stroke_pieces(&Document::new(1.0, 1.0), &pressure_calli(size, var), &bp, &pressed(profile));
            let mut pts = vec![];
            for n in &out {
                all_points(n, &mut pts);
            }
            assert!(pts.iter().all(|p| p.x.is_finite() && p.y.is_finite()), "{size} {var}");
        }
    }
}

/// A scatter brush of 10 × 4 pt rectangles whose size goes from `lo` % to `hi` % as `mode` says.
fn sized_scatter(lo: f64, hi: f64, mode: Variation) -> Brush {
    let s = scatter_brush(100.0);
    let BrushKind::Scatter(sc) = s.kind else { panic!("not a scatter brush") };
    let modes = [mode, Variation::Fixed, Variation::Fixed, Variation::Fixed];
    Brush { kind: BrushKind::Scatter(Scatter { size: (lo, hi), modes: Some(modes), ..sc }), ..s }
}

/// Scatter Brush Options: Fixed takes the first value, Pressure goes from the first at the
/// lightest pen pressure to the second at the heaviest; brushes saved before modes keep their look.
#[test]
fn scatter_values_follow_their_modes() {
    let bp = line(0.0, 0.0, 400.0, 0.0);
    let heights = |b: &Brush, st: &StrokeLayer| -> Vec<f64> {
        stroke_pieces(&Document::new(1.0, 1.0), b, &bp, st).iter().map(|n| n.geometric_bounds().unwrap().height()).collect()
    };
    // Fixed: every copy at 50 %, whatever the second value.
    assert!(heights(&sized_scatter(50.0, 300.0, Variation::Fixed), &stroke(1.0)).iter().all(|h| near(*h, 2.0, 1e-6)));
    // Pressure: light at the start (50 %: 2 pt tall), heavy at the end (300 %: 12 pt).
    let ramp = pressed(vec![(0.0, 0.0), (1.0, 1.0)]);
    let h = heights(&sized_scatter(50.0, 300.0, Variation::Pressure), &ramp);
    let (first, last) = (h[0], h[h.len() - 1]);
    assert!(near(first, 2.0, 0.1) && last > 10.0, "{h:?}");
    assert!(h.windows(2).all(|w| w[1] >= w[0] - 1e-9), "grows with the pressure: {h:?}");
    // Without recorded pressure, half way between the two.
    assert!(heights(&sized_scatter(50.0, 300.0, Variation::Pressure), &stroke(1.0)).iter().all(|h| near(*h, 7.0, 1e-6)));
    // No modes saved: Random where the values differ, as before; Fixed and Random draw the same.
    let old = sized_scatter(50.0, 300.0, Variation::Random);
    let BrushKind::Scatter(sc) = &old.kind else { panic!("not a scatter brush") };
    assert_eq!(Scatter { modes: None, ..sc.clone() }.modes(), [Variation::Random, Variation::Fixed, Variation::Fixed, Variation::Fixed]);
    let unsaved = Brush { kind: BrushKind::Scatter(Scatter { modes: None, ..sc.clone() }), ..old.clone() };
    assert_eq!(
        stroke_pieces(&Document::new(1.0, 1.0), &old, &bp, &stroke(1.0)),
        stroke_pieces(&Document::new(1.0, 1.0), &unsaved, &bp, &stroke(1.0))
    );
    assert!(serde_json::to_value(&unsaved).unwrap().get("modes").is_none(), "not saved when unset");
}

/// Definitions from files and commands are kept within their ranges.
#[test]
fn sanitize_keeps_values_within_their_ranges() {
    let mut v = serde_json::to_value(sized_scatter(1e308, -1e308, Variation::Random)).unwrap();
    v["rotation"] = serde_json::json!([720.0, -1e300]);
    v["scatter"] = serde_json::json!([5000.0, 0.0]);
    let lib = parse_library(&serde_json::json!([
        v,
        {"name": "a", "type": "art", "art": rect_art(10.0, 4.0), "width": 1e308, "scale": {"mode": "betweenGuides", "start": -3.0, "end": 9.0}},
        {"name": "p", "type": "pattern", "side": rect_art(10.0, 4.0), "scale": 0.0, "spacing": -5.0},
        {"name": "c", "type": "calligraphic", "angle": 400.0, "roundness": -1.0, "size": 1e9, "variation": [1e9, -1.0, 2.0]},
        {"name": "b", "type": "bristle", "size": 0.0, "length": 1000.0, "density": 0.0},
    ]));
    let [s, a, p, c, b] = lib.as_slice() else { panic!("{lib:?}") };
    let BrushKind::Scatter(s) = &s.kind else { panic!() };
    assert_eq!((s.size, s.rotation, s.scatter), ((10000.0, 1.0), (180.0, -180.0), (1000.0, 0.0)));
    let BrushKind::Art(a) = &a.kind else { panic!() };
    assert_eq!((a.width, a.scale), (1000.0, ArtScale::BetweenGuides { start: 0.0, end: 1.0 }));
    let BrushKind::Pattern(p) = &p.kind else { panic!() };
    assert_eq!((p.scale, p.spacing), (1.0, 0.0));
    let BrushKind::Calligraphic(c) = &c.kind else { panic!() };
    assert_eq!((c.angle, c.roundness, c.size, c.variation), (180.0, 0.0, 1296.0, [180.0, 0.0, 2.0]));
    let BrushKind::Bristle(b) = &b.kind else { panic!() };
    assert_eq!((b.size, b.length, b.density), (0.1, 300.0, 1.0));
}

/// Hue Shift's key colour defaults to the art's most used colour.
#[test]
fn art_colors_list_the_most_used_first() {
    let red = Color::rgb(1.0, 0.0, 0.0);
    let blue = Color::rgb(0.0, 0.0, 1.0);
    let path =
        |c: Color| Node::path(NodeId(0), shapes::rectangle(Rect::new(0.0, 0.0, 1.0, 1.0)), Appearance::basic(Paint::solid(c), Paint::None, 0.0));
    let g = Node::group(NodeId(0), vec![Arc::new(path(red)), Arc::new(path(blue)), Arc::new(path(blue))]);
    assert_eq!(art_colors([&g]), vec![blue, red]);
    // Type counts its characters' fills and drawn strokes.
    let text = type_art(Paint::solid(red), Paint::solid(red));
    let g = Node::group(NodeId(0), vec![Arc::new(path(blue)), Arc::new(text.clone())]);
    assert_eq!(art_colors([&g]), vec![red, blue]);
    let NodeKind::Text(mut t) = text.kind else { panic!("not type") };
    t.runs[0].style.stroke_width = 0.0;
    let text = Node::new(NodeId(0), NodeKind::Text(t));
    let g = Node::group(NodeId(0), vec![Arc::new(text), Arc::new(path(blue)), Arc::new(path(blue))]);
    assert_eq!(art_colors([&g]), vec![blue, red], "a stroke 0 wide is not counted");
    let b = defaults().iter().find(|b| b.name == "Chain").unwrap();
    assert_eq!(b.art().len(), 3, "the side and both corner tiles");
    assert!(calli(0.0, 100.0, 3.0).art().is_empty());
}

/// A Hue Shift definition without a key color takes the art's most used color, or black when the
/// art has no solid color; a key that is given is kept.
#[test]
fn hue_shift_without_a_key_takes_the_most_used_art_color() {
    let red = Color::rgb(1.0, 0.0, 0.0);
    let blue = Color::rgb(0.0, 0.0, 1.0);
    let path = |fill: Paint| Node::path(NodeId(0), shapes::rectangle(Rect::new(0.0, 0.0, 1.0, 1.0)), Appearance::basic(fill, Paint::None, 0.0));
    let art = Node::group(NodeId(0), vec![Arc::new(path(Paint::solid(red))), Arc::new(path(Paint::solid(blue))), Arc::new(path(Paint::solid(blue)))]);
    let lib = parse_library(&serde_json::json!([
        {"name": "s", "type": "scatter", "art": art, "colorization": {"method": "hueShift"}},
        {"name": "a", "type": "art", "art": art, "colorization": {"method": "hueShift", "key": null}},
        {"name": "p", "type": "pattern", "side": art, "colorization": {"method": "hueShift", "key": red}},
        {"name": "n", "type": "art", "art": path(Paint::None), "colorization": {"method": "hueShift"}},
    ]));
    let keys: Vec<(&str, Colorization)> = lib.iter().map(|b| (b.name.as_str(), b.kind.colorization())).collect();
    assert_eq!(
        keys,
        vec![
            ("s", Colorization::HueShift { key: blue }),
            ("a", Colorization::HueShift { key: blue }),
            ("p", Colorization::HueShift { key: red }),
            ("n", Colorization::HueShift { key: Color::BLACK }),
        ]
    );
}

/// Brush pieces draw no brushed stroke, also not by name: a symbol instance whose art is brushed
/// is left out, a pattern paint whose tile is brushed becomes no paint, and plain ones stay.
#[test]
fn pieces_leave_out_what_draws_a_brushed_stroke_by_name() {
    use vectorcraft_doc::{PatternDef, Symbol};
    let mut doc = Document::new(100.0, 100.0);
    let mut brushed = rect_art(10.0, 4.0);
    brushed.appearance.items.push(vectorcraft_doc::AppearanceItem::Stroke(StrokeLayer { brush: Some("s".into()), ..stroke(1.0) }));
    for (name, art) in [("plain", rect_art(10.0, 4.0)), ("brushed", brushed)] {
        doc.symbols.push(Symbol { name: name.into(), art: std::sync::Arc::new(art.clone()) });
        doc.patterns.push(PatternDef::new(name, vec![std::sync::Arc::new(art)]));
    }
    let instance = |symbol: &str| Node::new(NodeId(0), NodeKind::SymbolInstance { symbol: symbol.into(), xf: vectorcraft_geom::Affine::IDENTITY });
    let painted = |pattern: &str| {
        let fill = Paint::Pattern { pattern: pattern.into(), xf: vectorcraft_geom::Affine::IDENTITY };
        Node::path(NodeId(0), shapes::rectangle(Rect::new(0.0, 0.0, 10.0, 4.0)), Appearance::basic(fill, Paint::None, 0.0))
    };
    let art = Node::group(NodeId(0), [instance("plain"), instance("brushed"), painted("plain"), painted("brushed")].map(std::sync::Arc::new).into());
    let b = Brush { name: "s".into(), kind: BrushKind::Scatter(Scatter { art, colorization: Colorization::None, ..Default::default() }) };
    let out = stroke_pieces(&doc, &b, &line(0.0, 0.0, 100.0, 0.0), &stroke(1.0));
    assert!(!out.is_empty());
    for piece in &out {
        let children = piece.children().unwrap();
        let symbols: Vec<&str> = children
            .iter()
            .filter_map(|c| if let NodeKind::SymbolInstance { symbol, .. } = &c.kind { Some(symbol.as_str()) } else { None })
            .collect();
        assert_eq!(symbols, ["plain"]);
        let fills: Vec<Paint> =
            children.iter().filter(|c| c.path_data().is_some()).filter_map(|c| c.appearance.fill().map(|f| f.paint.clone())).collect();
        assert_eq!(fills, [Paint::Pattern { pattern: "plain".into(), xf: vectorcraft_geom::Affine::IDENTITY }, Paint::None]);
    }
}

/// Anchors a brushed stroke emitted, which is what the output budget counts.
fn anchors(nodes: &[Node]) -> usize {
    nodes
        .iter()
        .map(|n| match &n.kind {
            NodeKind::Path { path, .. } => path.subpaths.iter().map(|s| s.anchors.len()).sum::<usize>(),
            _ => 0,
        })
        .sum()
}

/// A path of `subpaths` long parallel lines, each long enough to want more tiles than the
/// per-run cap allows.
fn many_long_subpaths(subpaths: usize) -> BezPath {
    let mut bp = BezPath::new();
    for i in 0..subpaths {
        let y = i as f64 * 50.0;
        bp.move_to((0.0, y));
        bp.line_to((300_000.0, y));
    }
    bp
}

/// #3594: the per-factor caps are per track, and a path has as many tracks as it has subpaths,
/// so they multiply instead of bounding. Measured before the budget: 20,000 nodes and 320,000
/// anchors for one subpath, and exactly N times that for N, so sixteen gave 5,120,000.
#[test]
fn pattern_output_is_capped_across_subpaths_not_only_per_run() {
    let brush = pattern_brush(PatternFit::Stretch, false);
    let one = stroke_pieces(&Document::new(1.0, 1.0), &brush, &many_long_subpaths(1), &stroke(1.0));
    assert_eq!(one.len(), 20_000, "one track still fills its own per-run cap");
    let a1 = anchors(&one);
    assert!(a1 < 2_000_000, "one track stays under the total budget: {a1}");

    // Sixteen tracks would be sixteen times that without a total budget.
    // Four tracks are 4 x 320,000 anchors, still inside the budget, so nothing is cut: the
    // budget must not bite before the per-factor caps have actually multiplied past it.
    let four = stroke_pieces(&Document::new(1.0, 1.0), &brush, &many_long_subpaths(4), &stroke(1.0));
    assert_eq!(four.len(), 4 * 20_000, "four tracks are under the budget and keep every piece");
    assert_eq!(anchors(&four), 4 * a1);

    // Sixteen would be 5,120,000 anchors. The budget is what stops it, not the per-run caps.
    let many = stroke_pieces(&Document::new(1.0, 1.0), &brush, &many_long_subpaths(16), &stroke(1.0));
    let an = anchors(&many);
    assert!(an <= 2_000_000, "sixteen subpaths must not exceed the budget: {an}");
    assert!(an > anchors(&four), "but more is drawn than four tracks' worth: {an}");
    assert!(many.len() < 16 * 20_000, "and fewer pieces than the per-run caps alone would allow: {}", many.len());
}

/// The same for scatter, whose per-track guard is also 20,000 copies.
#[test]
fn scatter_output_is_capped_across_subpaths() {
    let b = Brush {
        name: "s".into(),
        kind: BrushKind::Scatter(Scatter { art: rect_art(4.0, 4.0), colorization: Colorization::None, ..Default::default() }),
    };
    let few = stroke_pieces(&Document::new(1.0, 1.0), &b, &many_long_subpaths(1), &stroke(1.0));
    let per_track = anchors(&few);
    assert!(per_track > 0, "one track draws something");
    // Enough tracks that the per-track guards alone would pass the budget.
    let tracks = 2_000_000 / per_track + 4;
    let many = stroke_pieces(&Document::new(1.0, 1.0), &b, &many_long_subpaths(tracks), &stroke(1.0));
    let an = anchors(&many);
    assert!(an <= 2_000_000, "{tracks} tracks must not exceed the budget: {an}");
    assert!(an > per_track, "but more is drawn than one track's worth: {an}");
    assert!(many.len() < tracks * few.len().max(1), "fewer copies than the per-track guards alone would allow");
}

/// A short, ordinary stroke is untouched by the budget: it is the absurd ones that are cut.
#[test]
fn an_ordinary_stroke_is_unaffected_by_the_budget() {
    let brush = pattern_brush(PatternFit::Stretch, false);
    let sq = shapes::rectangle(Rect::new(0.0, 0.0, 100.0, 100.0)).to_bezpath();
    let out = stroke_pieces(&Document::new(1.0, 1.0), &brush, &sq, &stroke(1.0));
    assert_eq!(out.len(), 40, "ten tiles on each of the four sides, as before the budget");
    assert!(anchors(&out) < 2_000_000);
}