use crate::path_builder::{arc_segment, ArcParameterization, CubicBezierCurve, Path, PathCommand};
fn curve(x1: f64, y1: f64, x2: f64, y2: f64, x3: f64, y3: f64, x4: f64, y4: f64) -> Segment {
// point) or a zero-length segment, i.e. where all four control points are coincident (the first
// and last control points may coincide, but the others may define a loop - thus nonzero length)