Stroke tessellator bad triangle

[songhuaixu]

bad triangle VertexId(13) VertexId(16) VertexId(16)
thread 'main' panicked at /Users/Users/.cargo/registry/src/index.crates.io-6f17d22bba15001f/lyon_tessellation-1.0.13/src/geometry_builder.rs:449:9:
assertion failed: b != c

struct VariableWidthStrokeCtor;
impl StrokeVertexConstructor<[f32; 2]> for VariableWidthStrokeCtor {
    fn new_vertex(&mut self, vertex: StrokeVertex) -> [f32; 2] {
        vertex.position().to_array()
    }
}

const STROKE_WIDTH: AttributeIndex = 0;

fn main() {
    let mut builder = Path::builder_with_attributes(1);
    builder.begin(point(435.72, 368.42), &[38.82]);
    builder.line_to(point(433.53, 366.06), &[38.82]);
    builder.quadratic_bezier_to(point(431.35, 363.70), point(430.22, 362.52), &[39.59]);
    builder.quadratic_bezier_to(point(429.09, 361.34), point(429.05, 362.14), &[41.62]);
    builder.line_to(point(429.00, 362.95), &[41.63]);
    builder.end(false);
    let path = builder.build();
    let mut stroke_tessellator = StrokeTessellator::new();
    let mut geometry: lyon::tessellation::VertexBuffers<[f32; 2], u16> =
        lyon::tessellation::VertexBuffers::new();
    _ = stroke_tessellator.tessellate_path(
        &path,
        &StrokeOptions::tolerance(0.01)
            .with_line_cap(LineCap::Round)
            .with_variable_line_width(STROKE_WIDTH),
        &mut BuffersBuilder::new(&mut geometry, VariableWidthStrokeCtor),
    );
}

But if we change

    builder.line_to(point(429.00, 362.95), &[41.63]);

to

    builder.line_to(point(429.00, 362.95), &[41.5]);

, there's no problem

[nical]

Thanks for filing this and providing a test case. I'll have a look soon-ish.