From 0aba3f7632457150cfe18c96510022e1566151c6 Mon Sep 17 00:00:00 2001 From: ljkx <177671075+ljkx@users.noreply.github.com> Date: Mon, 9 Nov 2026 06:15:26 +0100 Subject: [PATCH 1/2] M4: a Pencil stroke stays where it was drawn, without spikes off it (#1741) kurbo's simplify_bezpath, which smooths Pencil samples and runs Simplify path, fitted two common shapes with a curve that ran far off the path: a stroke that goes out and back to the very point it left (kurbo keeps a reversal as a smooth join) and nearly collinear samples (kurbo measures its error across the path, not along it). figcraft_geom::simplify_path cuts the path where it turns back by more than a right angle, simplifies each run with kurbo, and keeps a run as it was when its fit strays more than twice the accuracy from it. The Pencil and vector.simplify use it. --- crates/engine/src/brush_tests.rs | 46 +++++++ crates/engine/src/canvas/tools/pen.rs | 5 +- crates/engine/src/cmd/structure.rs | 8 +- crates/engine/src/vector_behaviour_tests.rs | 21 +++ crates/geom/src/lib.rs | 2 + crates/geom/src/simplify.rs | 140 ++++++++++++++++++++ crates/geom/src/tests.rs | 117 ++++++++++++++++ 7 files changed, 333 insertions(+), 6 deletions(-) create mode 100644 crates/geom/src/simplify.rs diff --git a/crates/engine/src/brush_tests.rs b/crates/engine/src/brush_tests.rs index 35dba6a7f..50317496d 100644 --- a/crates/engine/src/brush_tests.rs +++ b/crates/engine/src/brush_tests.rs @@ -149,3 +149,49 @@ fn the_pencil_draws_white_on_a_dark_background() { assert_eq!(stroke(&mut s, 0.0, 600.0).0, want, "on {bg}"); } } + +/// A Pencil stroke stays where it was drawn: the fitted curve shot far off the stroke, a spike +/// (#1741, its second point), where the stroke went out and back to the very point it left and +/// where samples ran on nearly straight. Pointer pixels become fractional page points, so going +/// back to a pixel lands on exactly the same point. Both sample runs are ones kurbo's fit took +/// hundreds of units off. +#[test] +fn the_pencil_keeps_its_stroke_where_it_was_drawn() { + let mut s = Session::new(); + s.execute("tool.set", &json!({"tool": "pencil"})).unwrap(); + let (p, q) = ((86.043_565_719_086_97, -173.744_402_349_100_94), (87.851_850_739_335_35, -179.202_846_445_954_52)); + let back = [(80.0, -160.0), p, q, p, (95.0, -185.0)]; + let straight = [ + (204.0, -198.0), + (209.598_690_794_015_5, -204.909_328_119_739_88), + (211.277_914_263_870_97, -207.190_974_020_753_4), + (214.246_506_828_720_84, -211.228_827_590_623_24), + (218.0, -214.0), + ]; + for (what, samples) in [("out and back", &back[..]), ("nearly straight", &straight[..])] { + let (first, last) = (samples[0], samples[samples.len() - 1]); + s.pointer(&PointerEvent::at(PointerKind::Down, first.0, first.1, 1.0)).unwrap(); + for (x, y) in &samples[1..] { + s.pointer(&PointerEvent::at(PointerKind::Move, *x, *y, 1.0)).unwrap(); + } + s.pointer(&PointerEvent::at(PointerKind::Up, last.0, last.1, 1.0)).unwrap(); + let doc = s.doc().unwrap(); + let n = doc.nodes().filter(|n| matches!(n.kind, NodeKind::Vector { .. })).max_by_key(|n| n.id).unwrap(); + let NodeKind::Vector { network } = &n.kind else { panic!("{what}: not a vector") }; + let drawn = doc.world_transform(n.id) * network.stroke_path(); + let samples_box = figcraft_geom::points_bounds(samples.iter().map(|(x, y)| Point::new(*x, *y))).unwrap(); + let (path_box, node_box) = (figcraft_geom::Shape::bounding_box(&drawn), doc.world_bounds(n.id).unwrap()); + assert!( + samples_box.inflate(1.5, 1.5).contains_rect(path_box), + "{what}: the stroke {path_box:?} goes past the samples {samples_box:?}: {}", + drawn.to_svg() + ); + assert!(samples_box.inflate(1.5, 1.5).contains_rect(node_box), "{what}: the layer {node_box:?}, the samples {samples_box:?}"); + } + // The turn is a point of the stroke, where it was drawn. + let doc = s.doc().unwrap(); + let turned = doc.nodes().find(|n| n.name == "Vector" && doc.world_bounds(n.id).is_some_and(|b| b.y1 < -150.0 && b.x1 < 100.0)).unwrap(); + let NodeKind::Vector { network } = &turned.kind else { panic!("not a vector") }; + let xf = doc.world_transform(turned.id); + assert!(network.vertices.iter().any(|v| (xf * Point::new(v.x, v.y) - Point::new(q.0, q.1)).hypot() < 1e-6), "no point at the turn"); +} diff --git a/crates/engine/src/canvas/tools/pen.rs b/crates/engine/src/canvas/tools/pen.rs index 4b98ccee1..3f8b47e59 100644 --- a/crates/engine/src/canvas/tools/pen.rs +++ b/crates/engine/src/canvas/tools/pen.rs @@ -313,7 +313,8 @@ impl Session { if points.len() < 2 { return Ok(()); } - // Smooth: fit a curve through the samples. + // Smooth: fit a curve through the samples, kept from shooting past them where the stroke + // turns back or runs nearly straight (#1741). let mut poly = figcraft_geom::BezPath::new(); for (k, p) in points.iter().enumerate() { if k == 0 { @@ -322,7 +323,7 @@ impl Session { poly.line_to(*p); } } - let fitted = figcraft_geom::kurbo::simplify::simplify_bezpath(poly.iter(), 0.75, &Default::default()); + let fitted = figcraft_geom::simplify_path(&poly, 0.75); let d = fitted.to_svg(); if matches!(self.tool.tool, ToolId::Marker | ToolId::Highlighter) { return self.ink_finish(&d); diff --git a/crates/engine/src/cmd/structure.rs b/crates/engine/src/cmd/structure.rs index 3339faa38..34cc91fbb 100644 --- a/crates/engine/src/cmd/structure.rs +++ b/crates/engine/src/cmd/structure.rs @@ -799,7 +799,7 @@ fn simplify(s: &mut Session, p: &Value) -> Result { WindingRule::NonZero }; let path = drawn.fill_path(); - let path = figcraft_geom::kurbo::simplify::simplify_bezpath(path.iter(), tol, &Default::default()); + let path = figcraft_geom::simplify_path(&path, tol); let (path, output_winding) = match figcraft_pathops::simplify_with_rule(&path, winding == WindingRule::EvenOdd) { Ok(path) => (path, WindingRule::EvenOdd), Err(_) => (path, winding), @@ -809,7 +809,7 @@ fn simplify(s: &mut Session, p: &Value) -> Result { } else { for (index, region) in source.regions.iter().enumerate() { let Some(path) = drawn.region_path(index) else { continue }; - let path = figcraft_geom::kurbo::simplify::simplify_bezpath(path.iter(), tol, &Default::default()); + let path = figcraft_geom::simplify_path(&path, tol); let path = figcraft_pathops::simplify_with_rule(&path, region.winding == WindingRule::EvenOdd).unwrap_or(path); append_region_path(&mut net, &path, region, region.winding); } @@ -826,7 +826,7 @@ fn simplify(s: &mut Session, p: &Value) -> Result { open.regions.clear(); if !open.segments.is_empty() { let path = open.stroke_path(); - let simplified = figcraft_geom::kurbo::simplify::simplify_bezpath(path.iter(), tol, &Default::default()); + let simplified = figcraft_geom::simplify_path(&path, tol); let mut loose = VectorNetwork::from_path(&simplified); loose.regions.clear(); append_network(&mut net, loose); @@ -834,7 +834,7 @@ fn simplify(s: &mut Session, p: &Value) -> Result { } if source.regions.is_empty() { let path = source.stroke_path(); - let simplified = figcraft_geom::kurbo::simplify::simplify_bezpath(path.iter(), tol, &Default::default()); + let simplified = figcraft_geom::simplify_path(&path, tol); net = VectorNetwork::from_path(&simplified); net.regions.clear(); } diff --git a/crates/engine/src/vector_behaviour_tests.rs b/crates/engine/src/vector_behaviour_tests.rs index c990ad348..4666c3028 100644 --- a/crates/engine/src/vector_behaviour_tests.rs +++ b/crates/engine/src/vector_behaviour_tests.rs @@ -326,6 +326,27 @@ fn ex_to_vector(doc: &mut figcraft_doc::Document, id: NodeId) { doc.get_mut(id).unwrap().kind = NodeKind::Vector { network }; } +/// Simplify path keeps nearly collinear points near where they were: kurbo's fit, which Simplify +/// path and the Pencil share, ran a handle hundreds of units on along the line (#1741). +#[test] +fn simplify_keeps_nearly_collinear_points_near_them() { + let mut s = Session::new(); + let id = id_of(&ex(&mut s, "vector.create", json!({"path": "M0 0 L10 10"}))["id"]).unwrap(); + // The points exactly as sampled, at the page origin (`vector.create` would move them). + let d = "M209.5986907940155 -204.90932811973988 L211.27791426387097 -207.1909740207534 L214.24650682872084 -211.22882759062324"; + let before = BezPath::from_svg(d).unwrap(); + { + let n = s.doc_mut().unwrap().get_mut(id).unwrap(); + n.transform = figcraft_geom::Affine::IDENTITY; + n.kind = NodeKind::Vector { network: VectorNetwork::from_path(&before) }; + } + assert_eq!(net(&s, id).stroke_path().elements(), before.elements(), "the samples as they were"); + ex(&mut s, "vector.simplify", json!({"ids": [id], "tolerance": 0.75})); + let after = s.doc().unwrap().world_transform(id) * net(&s, id).stroke_path(); + let (b0, b1) = (before.bounding_box(), after.bounding_box()); + assert!(b0.inflate(1.5, 1.5).contains_rect(b1), "{b1:?} past {b0:?}: {}", after.to_svg()); +} + fn ex(s: &mut Session, cmd: &str, p: Value) -> Value { s.execute(cmd, &p).unwrap_or_else(|e| panic!("{cmd}: {e}")) } diff --git a/crates/geom/src/lib.rs b/crates/geom/src/lib.rs index a775a4170..191b30419 100644 --- a/crates/geom/src/lib.rs +++ b/crates/geom/src/lib.rs @@ -12,7 +12,9 @@ use kurbo::ParamCurve; use std::f64::consts::{FRAC_PI_2, PI, TAU}; pub mod measure; +mod simplify; mod transform; +pub use simplify::simplify_path; pub use transform::*; /// Corner radii in clockwise order from the top-left: `[tl, tr, br, bl]`. diff --git a/crates/geom/src/simplify.rs b/crates/geom/src/simplify.rs new file mode 100644 index 000000000..e768f303a --- /dev/null +++ b/crates/geom/src/simplify.rs @@ -0,0 +1,140 @@ +//! Path simplification that keeps to its input where kurbo's fit would shoot past it. + +use kurbo::{BezPath, ParamCurve, ParamCurveNearest, PathEl, PathSeg, Point, Vec2}; + +/// How far, as a multiple of the accuracy asked for, a fitted run may stray from the run it +/// replaces before the run is kept as it was. kurbo's own fits stay within about the accuracy; its +/// failures stray by tens to hundreds of units, so twice the accuracy tells them apart without +/// undoing fits that are merely a little over. +const STRAY: f64 = 2.0; + +/// `path` simplified to within `accuracy` by kurbo's [`simplify_bezpath`], kept from straying +/// far from `path` where kurbo's fit does. +/// +/// Two inputs made kurbo's fit shoot far past the path it simplified (#1741, a Pencil stroke with +/// a spike off it), and both are common in pointer samples: +/// - A join where the path turns straight back (samples going down and back up the same line): +/// kurbo keeps two segments in one smooth fit when their tangents are parallel whichever way +/// they point (`|cross| <= |dot| * angle_thresh`), so it fits a smooth curve through the cusp. +/// The path is cut where it turns back by more than a right angle, each run between the cuts is +/// simplified on its own, and the runs are joined again, so the turn stays a sharp corner. Any +/// other join that isn't straight within kurbo's threshold is a corner to kurbo already, so the +/// cut changes nothing there. +/// - A run of nearly collinear segments: kurbo measures its error across the path, not along it, so +/// a fitted cubic whose handle runs hundreds of units on along the line passes its check. Each +/// fitted run is measured against the run it replaces, and one that strays more than +/// twice `accuracy` from it is kept as it was instead. +/// +/// Subpaths and closes are kept, and a closing segment stays implicit, as kurbo leaves it. +/// +/// [`simplify_bezpath`]: kurbo::simplify::simplify_bezpath +pub fn simplify_path(path: &BezPath, accuracy: f64) -> BezPath { + let mut out = BezPath::new(); + let mut run = BezPath::new(); + // Where the current subpath started, where the pen is, and the last segment's end tangent. + let mut start = Point::ZERO; + let mut at = Point::ZERO; + let mut last_tan: Option = None; + // Whether the next run that draws anything has to start the subpath with its move. + let mut fresh = true; + for el in path.elements() { + let seg = match *el { + PathEl::MoveTo(p) => { + flush(&mut out, &mut run, accuracy, &mut fresh); + (start, at, last_tan, fresh) = (p, p, None, true); + run.move_to(p); + continue; + } + PathEl::ClosePath => { + flush(&mut out, &mut run, accuracy, &mut fresh); + if !fresh { + out.close_path(); + } + // A segment after a close starts a new subpath at the closed one's start. + (at, last_tan, fresh) = (start, None, true); + run.move_to(start); + continue; + } + PathEl::LineTo(p) => PathSeg::Line(kurbo::Line::new(at, p)), + PathEl::QuadTo(p1, p2) => PathSeg::Quad(kurbo::QuadBez::new(at, p1, p2)), + PathEl::CurveTo(p1, p2, p3) => PathSeg::Cubic(kurbo::CubicBez::new(at, p1, p2, p3)), + }; + if run.elements().is_empty() { + run.move_to(at); + } + let Some((t0, t1)) = tangents(seg) else { continue }; + if last_tan.is_some_and(|last| last.dot(t0) < 0.0) { + flush(&mut out, &mut run, accuracy, &mut fresh); + run.move_to(at); + } + run.push(*el); + at = seg.end(); + last_tan = Some(t1); + } + flush(&mut out, &mut run, accuracy, &mut fresh); + out +} + +/// Simplify `run` (one move and the segments after it) with kurbo and append it to `out`; the +/// run's move is kept only when it starts a subpath (`fresh`), else the run carries on from the +/// last point drawn. `run` is left empty. +fn flush(out: &mut BezPath, run: &mut BezPath, accuracy: f64, fresh: &mut bool) { + if run.elements().len() > 1 { + let fitted = kurbo::simplify::simplify_bezpath(run.iter(), accuracy, &Default::default()); + let fitted = if keeps_to(&fitted, run, STRAY * accuracy) { fitted } else { std::mem::take(run) }; + for el in fitted.elements() { + match el { + PathEl::MoveTo(_) if !*fresh => {} + _ => { + out.push(*el); + *fresh = false; + } + } + } + } + *run = BezPath::new(); +} + +/// Whether every point of `fitted` lies within `tol` of `source`: one subpath each, from the same +/// start to the same end, `fitted` being kurbo's simplification of `source`. +/// +/// kurbo ends each fitted segment on the source, so the two are walked together: for each fitted +/// segment, the source segments from where it starts to the first one its end lies on are the only +/// ones its sample points are measured against. The work is linear in the two lengths. A fitted end +/// found on no source segment counts as straying. +fn keeps_to(fitted: &BezPath, source: &BezPath, tol: f64) -> bool { + /// Parts each fitted segment is cut into: the points between them are the ones measured. + const SAMPLES: u32 = 16; + let src: Vec = source.segments().collect(); + // kurbo puts each end on the source by evaluating it: off by rounding at most. + let on2 = (tol * 1e-3).powi(2); + let (tol2, mut cur) = (tol * tol, 0); + for seg in fitted.segments() { + let Some(last) = (cur..src.len()).find(|&i| src.get(i).is_some_and(|s| s.nearest(seg.end(), 1e-9).distance_sq <= on2)) else { + return false; + }; + let near = src.get(cur..=last).unwrap_or_default(); + for i in 1..SAMPLES { + let p = seg.eval(f64::from(i) / f64::from(SAMPLES)); + if !near.iter().any(|s| s.nearest(p, 1e-6).distance_sq <= tol2) { + return false; + } + } + cur = last; + } + true +} + +/// The directions `seg` leaves its start and reaches its end, skipping control points that sit on +/// an end; `None` for a segment of no length, which kurbo skips too. +fn tangents(seg: PathSeg) -> Option<(Vec2, Vec2)> { + let pts: Vec = match seg { + PathSeg::Line(l) => vec![l.p0, l.p1], + PathSeg::Quad(q) => vec![q.p0, q.p1, q.p2], + PathSeg::Cubic(c) => vec![c.p0, c.p1, c.p2, c.p3], + }; + let (first, last) = (*pts.first()?, *pts.last()?); + let t0 = pts.iter().map(|p| *p - first).find(|d| d.hypot2() > 0.0)?; + let t1 = pts.iter().rev().map(|p| last - *p).find(|d| d.hypot2() > 0.0)?; + Some((t0, t1)) +} diff --git a/crates/geom/src/tests.rs b/crates/geom/src/tests.rs index 459b2b101..10e09318c 100644 --- a/crates/geom/src/tests.rs +++ b/crates/geom/src/tests.rs @@ -366,3 +366,120 @@ fn svg_path_refuses_numbers_past_the_limit_before_parsing() { assert!(number_past("M0 0L-2.5.5 1e-3-4e3z", 1e3)); assert!(number_past("M.5.5e10", 1e3)); } + +/// A path through `pts` with straight lines (pencil samples). +fn polyline(pts: &[(f64, f64)]) -> BezPath { + let mut p = BezPath::new(); + for (k, (x, y)) in pts.iter().enumerate() { + if k == 0 { p.move_to((*x, *y)) } else { p.line_to((*x, *y)) } + } + p +} + +/// How far `out` strays from `input`: the largest distance from a point sampled along `out` to the +/// nearest segment of `input` (closing segments included). +fn deviation(out: &BezPath, input: &BezPath) -> f64 { + use kurbo::{ParamCurve, ParamCurveNearest}; + let segs: Vec = input.segments().collect(); + out.segments() + .flat_map(|seg| (0..=32).map(move |i| seg.eval(f64::from(i) / 32.0))) + .map(|p| segs.iter().map(|s| s.nearest(p, 1e-6).distance_sq).fold(f64::INFINITY, f64::min).sqrt()) + .fold(0.0, f64::max) +} + +/// Pencil strokes kurbo's fit shot far past keep to their samples (#1741): a stroke that goes out +/// and back to the very point it left, nearly collinear samples, and strokes that turn back along +/// their own line. The first two are from fuzzing pencil-like strokes, where kurbo's curve went +/// about 390 and 160 units off; at whole-pixel coordinates the same shapes happened to fit well. +#[test] +fn simplifying_keeps_to_strokes_kurbo_shot_past() { + use kurbo::ParamCurve; + let cases: [(&str, &[(f64, f64)]); 5] = [ + ( + "out and back to the same point", + &[ + (86.043_565_719_086_97, -173.744_402_349_100_94), + (87.851_850_739_335_35, -179.202_846_445_954_52), + (86.043_565_719_086_97, -173.744_402_349_100_94), + ], + ), + ( + "nearly collinear", + &[ + (209.598_690_794_015_5, -204.909_328_119_739_88), + (211.277_914_263_870_97, -207.190_974_020_753_4), + (214.246_506_828_720_84, -211.228_827_590_623_24), + ], + ), + ( + "a dip straight down and back up", + &[(0.0, 0.0), (10.0, 0.0), (20.0, 2.0), (30.0, 6.0), (30.0, 12.0), (30.0, 6.0), (40.0, 2.0), (50.0, 0.0)], + ), + ("a slip back at the end", &[(0.0, 0.0), (10.0, 3.0), (20.0, 8.0), (30.0, 15.0), (30.0, 25.0), (30.0, 22.0)]), + ( + "a near reversal in a curve", + &[(0.0, 0.0), (8.0, 2.0), (16.0, 6.0), (24.0, 12.0), (32.0, 20.0), (24.0, 12.000_01), (16.0, 6.0), (8.0, 2.0)], + ), + ]; + for (what, pts) in cases { + let input = polyline(pts); + let out = simplify_path(&input, 0.75); + let d = deviation(&out, &input); + assert!(d <= 1.5, "{what}: strays {d} from the samples: {}", out.to_svg()); + let (inb, outb) = (input.bounding_box(), out.bounding_box()); + assert!(inb.inflate(1.5, 1.5).contains_rect(outb), "{what}: {outb:?} past {inb:?}"); + // One subpath, starting and ending where the stroke does. + let moves = out.elements().iter().filter(|e| matches!(e, kurbo::PathEl::MoveTo(_))).count(); + assert_eq!(moves, 1, "{what}: {}", out.to_svg()); + let (first, last) = (pts[0], pts[pts.len() - 1]); + assert_eq!(out.segments().next().map(|s| s.start()), Some(Point::new(first.0, first.1)), "{what}"); + assert_eq!(out.segments().last().map(|s| s.end()), Some(Point::new(last.0, last.1)), "{what}"); + } +} + +/// Where a path never turns back and kurbo's fit holds, the result is kurbo's own, element for +/// element: smooth runs, corners sharper than a right angle, closed subpaths and several subpaths. +#[test] +fn simplifying_is_kurbos_where_its_fit_holds() { + let wave: Vec<(f64, f64)> = (0..=60).map(|i| (f64::from(i) * 4.0, (f64::from(i) / 6.0).sin() * 30.0)).collect(); + let zigzag: Vec<(f64, f64)> = (0..=8).map(|i| (f64::from(i) * 10.0, if i % 2 == 0 { 0.0 } else { 40.0 })).collect(); + let mut closed = polyline(&wave[..20]); + closed.close_path(); + let mut several = polyline(&wave); + several.extend(polyline(&zigzag).elements().iter().map(|e| match *e { + kurbo::PathEl::MoveTo(p) => kurbo::PathEl::MoveTo(p + Vec2::new(0.0, 100.0)), + kurbo::PathEl::LineTo(p) => kurbo::PathEl::LineTo(p + Vec2::new(0.0, 100.0)), + e => e, + })); + let curves = BezPath::from_svg("M0 0 C10 -20 30 -20 40 0 C50 20 70 20 80 0 Q100 -30 120 0 L140 10 Z M200 0 L240 0").unwrap(); + for (what, input) in + [("a wave", polyline(&wave)), ("a zigzag", polyline(&zigzag)), ("closed", closed), ("two subpaths", several), ("curves", curves)] + { + let ours = simplify_path(&input, 0.75); + let theirs = kurbo::simplify::simplify_bezpath(input.iter(), 0.75, &Default::default()); + assert_eq!(ours.elements(), theirs.elements(), "{what}"); + } +} + +/// A closed path with a reversal in it stays one closed subpath, and each subpath of several keeps +/// its own start. +#[test] +fn simplifying_keeps_closes_and_subpaths_across_a_reversal() { + let mut input = polyline(&[(0.0, 0.0), (40.0, 0.0), (40.0, 30.0), (40.0, 20.0), (0.0, 30.0)]); + input.close_path(); + input.extend(polyline(&[(100.0, 0.0), (100.0, 20.0), (100.0, 10.0)]).elements().iter().copied()); + let out = simplify_path(&input, 0.75); + let els = out.elements(); + let moves: Vec = els.iter().filter_map(|e| if let kurbo::PathEl::MoveTo(p) = e { Some(*p) } else { None }).collect(); + assert_eq!(moves, [Point::new(0.0, 0.0), Point::new(100.0, 0.0)], "{}", out.to_svg()); + assert_eq!(els.iter().filter(|e| matches!(e, kurbo::PathEl::ClosePath)).count(), 1, "{}", out.to_svg()); + let close = els.iter().position(|e| matches!(e, kurbo::PathEl::ClosePath)).unwrap(); + assert!(matches!(els[close + 1], kurbo::PathEl::MoveTo(_)), "the first subpath closes before the second starts"); + assert!(deviation(&out, &input) <= 1.5, "{}", out.to_svg()); + // Nothing to draw: nothing out, not a stray move or close. + let mut empty = BezPath::new(); + empty.move_to((5.0, 5.0)); + empty.line_to((5.0, 5.0)); + empty.close_path(); + assert!(simplify_path(&empty, 0.75).elements().is_empty()); +} From 61389cdd5fc03fe76bea0c80f8bed3d0606c8da1 Mon Sep 17 00:00:00 2001 From: ljkx <177671075+ljkx@users.noreply.github.com> Date: Mon, 9 Nov 2026 21:51:37 +0100 Subject: [PATCH 2/2] M4: test the simplified stroke by how far it strays, at more accuracies and inputs (#1741) Review follow-ups, tests only. - The Pencil test and the `vector.simplify` test measure how far the result strays from the samples (at most 1.5), not only its box. - The Pencil test also draws with the Marker and the Highlighter, each stroke in a fresh session, and takes the layer that stroke made. - The `vector.simplify` test runs on an open stroke, a filled shape, a region with its own fill, and a stroke beside a filled shape. - The geom tests run at accuracies 0.1, 0.75 and 8.0, on quadratic and cubic inputs as well as lines, and check both ways round how far the result and the input are apart. - A path that turns straight back is checked to be kurbo's fit of each side on its own, with a point at the turn. - Empty paths, lone moves and segments after a close are covered. --- crates/engine/src/brush_tests.rs | 72 +++++--- crates/engine/src/vector_behaviour_tests.rs | 63 +++++-- crates/geom/src/tests.rs | 191 ++++++++++++++++++-- 3 files changed, 267 insertions(+), 59 deletions(-) diff --git a/crates/engine/src/brush_tests.rs b/crates/engine/src/brush_tests.rs index 50317496d..065e5eec9 100644 --- a/crates/engine/src/brush_tests.rs +++ b/crates/engine/src/brush_tests.rs @@ -8,6 +8,7 @@ use crate::params::id_of; use crate::tools::{PointerEvent, PointerKind, pressure_profile}; use figcraft_doc::{NodeId, NodeKind}; use figcraft_geom::Point; +use figcraft_geom::kurbo::PathEl; fn id(v: Value) -> NodeId { id_of(&v["id"]).unwrap() @@ -155,10 +156,12 @@ fn the_pencil_draws_white_on_a_dark_background() { /// where samples ran on nearly straight. Pointer pixels become fractional page points, so going /// back to a pixel lands on exactly the same point. Both sample runs are ones kurbo's fit took /// hundreds of units off. +/// +/// Each stroke is drawn in a fresh session, with the Pencil and with the Marker and Highlighter +/// of a board, whose ink comes from the same fit. Every point along the stroke drawn must lie +/// within 1.5 (twice the fit's accuracy) of the polyline through the samples. #[test] fn the_pencil_keeps_its_stroke_where_it_was_drawn() { - let mut s = Session::new(); - s.execute("tool.set", &json!({"tool": "pencil"})).unwrap(); let (p, q) = ((86.043_565_719_086_97, -173.744_402_349_100_94), (87.851_850_739_335_35, -179.202_846_445_954_52)); let back = [(80.0, -160.0), p, q, p, (95.0, -185.0)]; let straight = [ @@ -168,30 +171,47 @@ fn the_pencil_keeps_its_stroke_where_it_was_drawn() { (214.246_506_828_720_84, -211.228_827_590_623_24), (218.0, -214.0), ]; - for (what, samples) in [("out and back", &back[..]), ("nearly straight", &straight[..])] { - let (first, last) = (samples[0], samples[samples.len() - 1]); - s.pointer(&PointerEvent::at(PointerKind::Down, first.0, first.1, 1.0)).unwrap(); - for (x, y) in &samples[1..] { - s.pointer(&PointerEvent::at(PointerKind::Move, *x, *y, 1.0)).unwrap(); + for tool in ["pencil", "marker", "highlighter"] { + for (what, samples) in [("out and back", &back[..]), ("nearly straight", &straight[..])] { + let what = format!("{tool}, {what}"); + let mut s = if tool == "pencil" { Session::new() } else { crate::board_tests::board() }; + s.execute("tool.set", &json!({"tool": tool})).unwrap(); + let before: Vec = s.doc().unwrap().nodes().map(|n| n.id).collect(); + let (first, last) = (samples[0], samples[samples.len() - 1]); + s.pointer(&PointerEvent::at(PointerKind::Down, first.0, first.1, 1.0)).unwrap(); + for (x, y) in &samples[1..] { + s.pointer(&PointerEvent::at(PointerKind::Move, *x, *y, 1.0)).unwrap(); + } + s.pointer(&PointerEvent::at(PointerKind::Up, last.0, last.1, 1.0)).unwrap(); + // The layer the stroke made, and only it. + let doc = s.doc().unwrap(); + let made: Vec<&figcraft_doc::Node> = + doc.nodes().filter(|n| !before.contains(&n.id) && matches!(n.kind, NodeKind::Vector { .. })).collect(); + let [n] = made[..] else { panic!("{what}: {} vectors made", made.len()) }; + let NodeKind::Vector { network } = &n.kind else { panic!("{what}: not a vector") }; + let drawn = doc.world_transform(n.id) * network.stroke_path(); + let polyline = figcraft_geom::BezPath::from_vec( + samples + .iter() + .enumerate() + .map(|(k, (x, y))| if k == 0 { PathEl::MoveTo(Point::new(*x, *y)) } else { PathEl::LineTo(Point::new(*x, *y)) }) + .collect(), + ); + let d = crate::vector_behaviour_tests::strays(&drawn, &polyline); + assert!(d <= 1.5, "{what}: the stroke strays {d} from the samples: {}", drawn.to_svg()); + let samples_box = figcraft_geom::points_bounds(samples.iter().map(|(x, y)| Point::new(*x, *y))).unwrap(); + let node_box = doc.world_bounds(n.id).unwrap(); + if tool == "pencil" { + assert!(samples_box.inflate(1.5, 1.5).contains_rect(node_box), "{what}: the layer {node_box:?}, the samples {samples_box:?}"); + } + // The turn is a point of the stroke, where it was drawn. + if samples == back { + let xf = doc.world_transform(n.id); + assert!( + network.vertices.iter().any(|v| (xf * Point::new(v.x, v.y) - Point::new(q.0, q.1)).hypot() < 1e-6), + "{what}: no point at the turn" + ); + } } - s.pointer(&PointerEvent::at(PointerKind::Up, last.0, last.1, 1.0)).unwrap(); - let doc = s.doc().unwrap(); - let n = doc.nodes().filter(|n| matches!(n.kind, NodeKind::Vector { .. })).max_by_key(|n| n.id).unwrap(); - let NodeKind::Vector { network } = &n.kind else { panic!("{what}: not a vector") }; - let drawn = doc.world_transform(n.id) * network.stroke_path(); - let samples_box = figcraft_geom::points_bounds(samples.iter().map(|(x, y)| Point::new(*x, *y))).unwrap(); - let (path_box, node_box) = (figcraft_geom::Shape::bounding_box(&drawn), doc.world_bounds(n.id).unwrap()); - assert!( - samples_box.inflate(1.5, 1.5).contains_rect(path_box), - "{what}: the stroke {path_box:?} goes past the samples {samples_box:?}: {}", - drawn.to_svg() - ); - assert!(samples_box.inflate(1.5, 1.5).contains_rect(node_box), "{what}: the layer {node_box:?}, the samples {samples_box:?}"); } - // The turn is a point of the stroke, where it was drawn. - let doc = s.doc().unwrap(); - let turned = doc.nodes().find(|n| n.name == "Vector" && doc.world_bounds(n.id).is_some_and(|b| b.y1 < -150.0 && b.x1 < 100.0)).unwrap(); - let NodeKind::Vector { network } = &turned.kind else { panic!("not a vector") }; - let xf = doc.world_transform(turned.id); - assert!(network.vertices.iter().any(|v| (xf * Point::new(v.x, v.y) - Point::new(q.0, q.1)).hypot() < 1e-6), "no point at the turn"); } diff --git a/crates/engine/src/vector_behaviour_tests.rs b/crates/engine/src/vector_behaviour_tests.rs index 4666c3028..d1d6907ee 100644 --- a/crates/engine/src/vector_behaviour_tests.rs +++ b/crates/engine/src/vector_behaviour_tests.rs @@ -326,25 +326,56 @@ fn ex_to_vector(doc: &mut figcraft_doc::Document, id: NodeId) { doc.get_mut(id).unwrap().kind = NodeKind::Vector { network }; } -/// Simplify path keeps nearly collinear points near where they were: kurbo's fit, which Simplify -/// path and the Pencil share, ran a handle hundreds of units on along the line (#1741). +/// How far `path` strays from `from`: the largest distance from a point sampled along `path` to +/// the nearest segment of `from`. +pub(crate) fn strays(path: &BezPath, from: &BezPath) -> f64 { + use figcraft_geom::kurbo::ParamCurveNearest; + let segs: Vec<_> = from.segments().collect(); + path.segments() + .flat_map(|seg| (0..=32).map(move |i| seg.eval(f64::from(i) / 32.0))) + .map(|p| segs.iter().map(|s| s.nearest(p, 1e-6).distance_sq).fold(f64::INFINITY, f64::min).sqrt()) + .fold(0.0, f64::max) +} + +/// Simplify path keeps nearly collinear points, and a stroke that goes out and back, near where +/// they were: kurbo's fit, which Simplify path and the Pencil share, ran a handle hundreds of units +/// on along the line (#1741). That holds for each way the command simplifies a layer: an open +/// stroke, a filled shape, a region with its own fill, and a stroke beside a filled shape. #[test] fn simplify_keeps_nearly_collinear_points_near_them() { - let mut s = Session::new(); - let id = id_of(&ex(&mut s, "vector.create", json!({"path": "M0 0 L10 10"}))["id"]).unwrap(); - // The points exactly as sampled, at the page origin (`vector.create` would move them). - let d = "M209.5986907940155 -204.90932811973988 L211.27791426387097 -207.1909740207534 L214.24650682872084 -211.22882759062324"; - let before = BezPath::from_svg(d).unwrap(); - { - let n = s.doc_mut().unwrap().get_mut(id).unwrap(); - n.transform = figcraft_geom::Affine::IDENTITY; - n.kind = NodeKind::Vector { network: VectorNetwork::from_path(&before) }; + // The points exactly as sampled. + let straight = "M209.5986907940155 -204.90932811973988 L211.27791426387097 -207.1909740207534 L214.24650682872084 -211.22882759062324"; + let back = + "M80 -160 L86.04356571908697 -173.74440234910094 L87.85185073933535 -179.20284644595452 L86.04356571908697 -173.74440234910094 L95 -185"; + let shape = format!("{straight} L260 -150 Z"); + let cases = [ + ("an open stroke", straight.to_string(), false), + ("a filled shape", shape.clone(), false), + ("a region with its own fill", shape.clone(), true), + ("a stroke beside a filled shape", format!("{shape} {back}"), false), + ]; + for (what, d, own_fill) in cases { + let mut s = Session::new(); + let id = id_of(&ex(&mut s, "vector.create", json!({"path": "M0 0 L10 10"}))["id"]).unwrap(); + // At the page origin, as given (`vector.create` would move the points). + let mut network = VectorNetwork::from_path(&BezPath::from_svg(&d).unwrap()); + if own_fill { + network.regions[0].fills = Some(vec![figcraft_color::Paint::solid(figcraft_color::Color::from_hex("#FF0000").unwrap())]); + } + { + let n = s.doc_mut().unwrap().get_mut(id).unwrap(); + n.transform = figcraft_geom::Affine::IDENTITY; + n.kind = NodeKind::Vector { network }; + } + let before = net(&s, id); + ex(&mut s, "vector.simplify", json!({"ids": [id], "tolerance": 0.75})); + let after = s.doc().unwrap().world_transform(id) * net(&s, id).stroke_path(); + let gone = strays(&after, &before.stroke_path()); + assert!(gone <= 1.5, "{what}: strays {gone}: {}", after.to_svg()); + let (b0, b1) = (before.stroke_path().bounding_box(), after.bounding_box()); + assert!(b0.inflate(1.5, 1.5).contains_rect(b1), "{what}: {b1:?} past {b0:?}: {}", after.to_svg()); + assert_eq!(net(&s, id).regions.len(), before.regions.len(), "{what}: the fill is kept"); } - assert_eq!(net(&s, id).stroke_path().elements(), before.elements(), "the samples as they were"); - ex(&mut s, "vector.simplify", json!({"ids": [id], "tolerance": 0.75})); - let after = s.doc().unwrap().world_transform(id) * net(&s, id).stroke_path(); - let (b0, b1) = (before.bounding_box(), after.bounding_box()); - assert!(b0.inflate(1.5, 1.5).contains_rect(b1), "{b1:?} past {b0:?}: {}", after.to_svg()); } fn ex(s: &mut Session, cmd: &str, p: Value) -> Value { diff --git a/crates/geom/src/tests.rs b/crates/geom/src/tests.rs index 10e09318c..786bf1935 100644 --- a/crates/geom/src/tests.rs +++ b/crates/geom/src/tests.rs @@ -393,7 +393,6 @@ fn deviation(out: &BezPath, input: &BezPath) -> f64 { /// about 390 and 160 units off; at whole-pixel coordinates the same shapes happened to fit well. #[test] fn simplifying_keeps_to_strokes_kurbo_shot_past() { - use kurbo::ParamCurve; let cases: [(&str, &[(f64, f64)]); 5] = [ ( "out and back to the same point", @@ -422,23 +421,127 @@ fn simplifying_keeps_to_strokes_kurbo_shot_past() { ), ]; for (what, pts) in cases { - let input = polyline(pts); - let out = simplify_path(&input, 0.75); - let d = deviation(&out, &input); - assert!(d <= 1.5, "{what}: strays {d} from the samples: {}", out.to_svg()); + keeps_to_one_stroke(what, &polyline(pts)); + } +} + +/// Accuracies the simplification is checked at: fine, the Pencil's, and coarse. +const ACCURACIES: [f64; 3] = [0.1, 0.75, 8.0]; + +/// Check that `input` (one open subpath), simplified at each of [`ACCURACIES`], strays no more +/// than twice the accuracy from it and leaves no part of it further off than that, stays in its +/// box grown by as much, and is still one subpath from its start to its end. +fn keeps_to_one_stroke(what: &str, input: &BezPath) { + for accuracy in ACCURACIES { + let out = simplify_path(input, accuracy); + let (svg, limit) = (out.to_svg(), 2.0 * accuracy); + let d = deviation(&out, input); + assert!(d <= limit, "{what} at {accuracy}: strays {d} from the input: {svg}"); + let left = deviation(input, &out); + assert!(left <= limit, "{what} at {accuracy}: leaves the input {left} off: {svg}"); let (inb, outb) = (input.bounding_box(), out.bounding_box()); - assert!(inb.inflate(1.5, 1.5).contains_rect(outb), "{what}: {outb:?} past {inb:?}"); - // One subpath, starting and ending where the stroke does. + assert!(inb.inflate(limit, limit).contains_rect(outb), "{what} at {accuracy}: {outb:?} past {inb:?}"); let moves = out.elements().iter().filter(|e| matches!(e, kurbo::PathEl::MoveTo(_))).count(); - assert_eq!(moves, 1, "{what}: {}", out.to_svg()); - let (first, last) = (pts[0], pts[pts.len() - 1]); - assert_eq!(out.segments().next().map(|s| s.start()), Some(Point::new(first.0, first.1)), "{what}"); - assert_eq!(out.segments().last().map(|s| s.end()), Some(Point::new(last.0, last.1)), "{what}"); + assert_eq!(moves, 1, "{what} at {accuracy}: {svg}"); + // From its start to its end: kurbo evaluates a fitted end on the input, so it is off by + // rounding at most. + let ends = |p: &BezPath| p.segments().next().map(|s| s.start()).zip(p.segments().last().map(|s| s.end())); + let ((start, end), (start_in, end_in)) = (ends(&out).unwrap(), ends(input).unwrap()); + assert!((start - start_in).hypot() < 1e-9 && (end - end_in).hypot() < 1e-9, "{what} at {accuracy}: {svg}"); + } +} + +/// Strokes made of curves keep to them as polylines do (#1741): a quadratic or a cubic that goes +/// out and comes straight back, one whose control points sit on its ends (so its direction is +/// read from the control point after them), and nearly collinear curves. +#[test] +fn simplifying_keeps_to_curves_that_turn_back_or_run_straight() { + let (p, q, r) = ( + (209.598_690_794_015_5, -204.909_328_119_739_88), + (211.277_914_263_870_97, -207.190_974_020_753_4), + (214.246_506_828_720_84, -211.228_827_590_623_24), + ); + // The nearly collinear samples, each line as a cubic with its handles a third of the way along. + let third = |a: (f64, f64), b: (f64, f64), t: f64| (a.0 + (b.0 - a.0) * t, a.1 + (b.1 - a.1) * t); + let mut straight_cubics = BezPath::new(); + straight_cubics.move_to(p); + for (a, b) in [(p, q), (q, r)] { + straight_cubics.curve_to(third(a, b, 1.0 / 3.0), third(a, b, 2.0 / 3.0), b); + } + let mut straight_quads = BezPath::new(); + straight_quads.move_to(p); + straight_quads.quad_to(third(p, q, 0.5), q); + straight_quads.quad_to(third(q, r, 0.5), r); + let cases = [ + ("a quadratic out and back", BezPath::from_svg("M0 0 Q15 10 30 0 Q15 10 0 0 Q-15 10 -30 0").unwrap()), + ("a cubic out and back", BezPath::from_svg("M0 0 C10 8 20 8 30 0 C20 8 10 8 0 0 C-10 8 -20 8 -30 0").unwrap()), + ("handles on the ends", BezPath::from_svg("M0 0 C0 0 30 4 30 4 C30 4 0 0 0 0 L-30 -4").unwrap()), + ("a cubic dip down and back up", BezPath::from_svg("M0 0 L10 0 C15 0 20 5 20 12 C20 5 25 0 30 0 L40 0").unwrap()), + ("nearly collinear cubics", straight_cubics), + ("nearly collinear quadratics", straight_quads), + ]; + for (what, input) in cases { + keeps_to_one_stroke(what, &input); + } +} + +/// `sides` simplified by kurbo one at a time and joined into one subpath. +fn fitted_apart(sides: &[&BezPath], accuracy: f64) -> BezPath { + let mut out = BezPath::new(); + for side in sides { + let fit = kurbo::simplify::simplify_bezpath(side.iter(), accuracy, &Default::default()); + let skip = usize::from(!out.elements().is_empty()); + out.extend(fit.elements().iter().copied().skip(skip)); + } + out +} + +/// `curve` cut into `n` cubics, drawn on from where `path` is: forwards, or back from its end. +fn in_pieces(path: &mut BezPath, curve: kurbo::CubicBez, n: u32, back: bool) { + use kurbo::ParamCurve; + for i in 0..n { + let i = if back { n - 1 - i } else { i }; + let c = curve.subsegment(f64::from(i) / f64::from(n)..f64::from(i + 1) / f64::from(n)); + if back { path.curve_to(c.p2, c.p1, c.p0) } else { path.curve_to(c.p1, c.p2, c.p3) } + } +} + +/// Where a path turns straight back it is cut, so the result is kurbo's fit of each side on its +/// own, with a point of the path at the turn. Fitted as one, kurbo rounds the turn off: its curve +/// passes the stray check, but falls short of the turn or takes more segments. A cubic whose +/// control points sit on its ends turns back as a line does. +#[test] +fn simplifying_fits_each_side_of_a_turn_back_on_its_own() { + use kurbo::ParamCurve; + let svg = |d: &str| BezPath::from_svg(d).unwrap(); + let s = kurbo::CubicBez::new((0.0, 0.0), (40.0, -60.0), (80.0, 60.0), (120.0, 0.0)); + let (mut s_out, mut s_back) = (BezPath::new(), BezPath::new()); + s_out.move_to(s.p0); + in_pieces(&mut s_out, s, 8, false); + s_back.move_to(s.p3); + in_pieces(&mut s_back, s, 8, true); + let cases = [ + ("lines", svg("M0 0 L10 0 L20 0 L30 0"), svg("M30 0 L20 0 L10 0")), + ("handles on the ends", svg("M0 0 L10 0 L20 0 C20 0 30 0 30 0"), svg("M30 0 C30 0 20 0 20 0 L10 0")), + ("a curve in pieces", s_out, s_back), + ]; + for (what, out_side, back_side) in cases { + let turn = out_side.segments().last().map(|seg| seg.end()).unwrap(); + let mut input = out_side.clone(); + input.extend(back_side.elements().iter().copied().skip(1)); + for accuracy in ACCURACIES { + let ours = simplify_path(&input, accuracy); + let apart = fitted_apart(&[&out_side, &back_side], accuracy); + assert_eq!(ours.elements(), apart.elements(), "{what} at {accuracy}"); + assert!(ours.segments().any(|seg| (seg.end() - turn).hypot() < 1e-9), "{what} at {accuracy}: {}", ours.to_svg()); + } } } /// Where a path never turns back and kurbo's fit holds, the result is kurbo's own, element for /// element: smooth runs, corners sharper than a right angle, closed subpaths and several subpaths. +/// A fit counts as holding up to twice the accuracy asked for, whatever that is: the large wave's +/// is further off at the coarse accuracy than the Pencil's limit of 1.5. #[test] fn simplifying_is_kurbos_where_its_fit_holds() { let wave: Vec<(f64, f64)> = (0..=60).map(|i| (f64::from(i) * 4.0, (f64::from(i) / 6.0).sin() * 30.0)).collect(); @@ -452,12 +555,30 @@ fn simplifying_is_kurbos_where_its_fit_holds() { e => e, })); let curves = BezPath::from_svg("M0 0 C10 -20 30 -20 40 0 C50 20 70 20 80 0 Q100 -30 120 0 L140 10 Z M200 0 L240 0").unwrap(); - for (what, input) in - [("a wave", polyline(&wave)), ("a zigzag", polyline(&zigzag)), ("closed", closed), ("two subpaths", several), ("curves", curves)] - { - let ours = simplify_path(&input, 0.75); - let theirs = kurbo::simplify::simplify_bezpath(input.iter(), 0.75, &Default::default()); - assert_eq!(ours.elements(), theirs.elements(), "{what}"); + // A sine 300 high in 40 smooth cubics. + let sine = |x: f64| ((x / 120.0).sin() * 300.0, (x / 120.0).cos() * 2.5); + let mut large = BezPath::new(); + large.move_to((0.0, 0.0)); + for i in 0..40 { + let (x0, x1) = (f64::from(i) * 40.0, f64::from(i + 1) * 40.0); + let ((y0, d0), (y1, d1)) = (sine(x0), sine(x1)); + large.curve_to((x0 + 40.0 / 3.0, y0 + d0 * 40.0 / 3.0), (x1 - 40.0 / 3.0, y1 - d1 * 40.0 / 3.0), (x1, y1)); + } + let coarse = simplify_path(&large, 8.0); + assert!(coarse.elements().len() < 10 && (1.5..=8.0).contains(&deviation(&coarse, &large)), "{}", deviation(&coarse, &large)); + for (what, input) in [ + ("a wave", polyline(&wave)), + ("a zigzag", polyline(&zigzag)), + ("closed", closed), + ("two subpaths", several), + ("curves", curves), + ("a large wave", large), + ] { + for accuracy in ACCURACIES { + let ours = simplify_path(&input, accuracy); + let theirs = kurbo::simplify::simplify_bezpath(input.iter(), accuracy, &Default::default()); + assert_eq!(ours.elements(), theirs.elements(), "{what} at {accuracy}"); + } } } @@ -482,4 +603,40 @@ fn simplifying_keeps_closes_and_subpaths_across_a_reversal() { empty.line_to((5.0, 5.0)); empty.close_path(); assert!(simplify_path(&empty, 0.75).elements().is_empty()); + for d in ["", "M5 5", "M5 5 M6 6", "M5 5 Z"] { + let input = if d.is_empty() { BezPath::new() } else { BezPath::from_svg(d).unwrap() }; + assert!(simplify_path(&input, 0.75).elements().is_empty(), "{d:?}"); + } +} + +/// The subpaths simplified keep their starts: a move with nothing drawn from it between two +/// subpaths leaves no trace, and a segment drawn on from a close starts a subpath where the closed +/// one started, as it does in the path given. +#[test] +fn simplifying_keeps_where_each_subpath_starts() { + let starts = + |p: &BezPath| -> Vec { p.elements().iter().filter_map(|e| if let kurbo::PathEl::MoveTo(p) = e { Some(*p) } else { None }).collect() }; + let between = BezPath::from_svg("M0 0 L10 0 L20 5 M50 50 M100 0 L110 0 L120 5").unwrap(); + let out = simplify_path(&between, 0.75); + assert_eq!(starts(&out), [Point::new(0.0, 0.0), Point::new(100.0, 0.0)], "{}", out.to_svg()); + assert!(deviation(&out, &between) <= 1.5, "{}", out.to_svg()); + // After the close, the pen is back at (0, 0): the next segments start there, also across a + // reversal. + use kurbo::PathEl::{ClosePath, LineTo, MoveTo}; + let on = BezPath::from_vec(vec![ + MoveTo(Point::new(0.0, 0.0)), + LineTo(Point::new(10.0, 0.0)), + LineTo(Point::new(10.0, 10.0)), + ClosePath, + LineTo(Point::new(20.0, 20.0)), + LineTo(Point::new(30.0, 20.0)), + LineTo(Point::new(20.0, 20.0)), + ]); + let out = simplify_path(&on, 0.75); + let els = out.elements(); + let close = els.iter().position(|e| matches!(e, kurbo::PathEl::ClosePath)).unwrap(); + assert_eq!(els.get(close + 1), Some(&kurbo::PathEl::MoveTo(Point::new(0.0, 0.0))), "{}", out.to_svg()); + assert_eq!(starts(&out), [Point::new(0.0, 0.0), Point::new(0.0, 0.0)], "{}", out.to_svg()); + assert_eq!(out.segments().last().map(|s| kurbo::ParamCurve::end(&s)), Some(Point::new(20.0, 20.0))); + assert!(deviation(&out, &on) <= 1.5, "{}", out.to_svg()); }