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Skip zero-length segments when finding arrowhead direction

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Found while testing crates/pathops/src/lib.rs:352 (path_end, used by arrowhead)

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
This commit is contained in:
NetterSilver
2026-10-24 18:52:03 +00:00
co-authored by Claude Haiku 5.5
parent 10702311f3
commit 42fbe8f00c
1 changed files with 43 additions and 26 deletions
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crates/pathops/src/lib.rs
+43 -26
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@@ -359,36 +359,35 @@ pub fn stroke_outline_of(path: &BezPath, props: &StrokeProps, closed_shape: bool
/// End point and outward direction of an open path at its start or end.
fn path_end(path: &BezPath, at_end: bool) -> Option<(Point, Vec2)> {
let segs: Vec<PathSeg> = path.segments().collect();
let seg = if at_end { segs.last()? } else { segs.first()? };
use kurbo::ParamCurve;
use kurbo::ParamCurveDeriv;
let (p, d) = if at_end {
let d = match seg {
PathSeg::Line(l) => l.p1 - l.p0,
PathSeg::Quad(q) => q.deriv().eval(1.0).to_vec2(),
PathSeg::Cubic(c) => {
let d = c.deriv().eval(1.0).to_vec2();
if d.hypot() < 1e-9 { c.p3 - c.p2 } else { d }
}
let dir_of = |seg: &PathSeg| -> Option<(Point, Vec2)> {
let (p, d) = if at_end {
let d = match seg {
PathSeg::Line(l) => l.p1 - l.p0,
PathSeg::Quad(q) => q.deriv().eval(1.0).to_vec2(),
PathSeg::Cubic(c) => {
let d = c.deriv().eval(1.0).to_vec2();
if d.hypot() < 1e-9 { c.p3 - c.p2 } else { d }
}
};
(seg.end(), d)
} else {
let d = match seg {
PathSeg::Line(l) => l.p0 - l.p1,
PathSeg::Quad(q) => -q.deriv().eval(0.0).to_vec2(),
PathSeg::Cubic(c) => {
let d = -c.deriv().eval(0.0).to_vec2();
if d.hypot() < 1e-9 { c.p0 - c.p1 } else { d }
}
};
(seg.start(), d)
};
(seg.end(), d)
} else {
let d = match seg {
PathSeg::Line(l) => l.p0 - l.p1,
PathSeg::Quad(q) => -q.deriv().eval(0.0).to_vec2(),
PathSeg::Cubic(c) => {
let d = -c.deriv().eval(0.0).to_vec2();
if d.hypot() < 1e-9 { c.p0 - c.p1 } else { d }
}
};
(seg.start(), d)
let len = d.hypot();
(len >= 1e-12).then(|| (p, d / len))
};
let len = d.hypot();
if len < 1e-12 {
return None;
}
Some((p, d / len))
// Skip zero-length segments (repeated vertices) and use the nearest one with a direction.
if at_end { path.segments().collect::<Vec<_>>().iter().rev().find_map(dir_of) } else { path.segments().find_map(|s| dir_of(&s)) }
}
/// The filled arrowhead shape for `cap` at one end of an open path.
@@ -742,4 +741,22 @@ mod tests {
let s = stroke_outline_of(&ring, &inside, true, Some(&nz));
assert!(s.winding(material) != 0 && s.winding(hole) != 0);
}
#[test]
fn arrowhead_skips_zero_length_end_segments() {
let mut p = BezPath::new();
p.move_to((0.0, 0.0));
p.line_to((100.0, 0.0));
assert!(arrowhead(&p, StrokeCap::TriangleArrow, 2.0, true).is_some());
p.line_to((100.0, 0.0));
let (tip, dir) = path_end(&p, true).expect("end direction");
assert_eq!((tip, dir), (Point::new(100.0, 0.0), Vec2::new(1.0, 0.0)));
assert!(arrowhead(&p, StrokeCap::TriangleArrow, 2.0, true).is_some());
let mut q = BezPath::new();
q.move_to((0.0, 0.0));
q.line_to((0.0, 0.0));
q.line_to((100.0, 0.0));
let (tip, dir) = path_end(&q, false).expect("start direction");
assert_eq!((tip, dir), (Point::new(0.0, 0.0), Vec2::new(-1.0, 0.0)));
}
}