tawasuyu/llimphi

1// Copyright 2024 the Velato Authors
2// SPDX-License-Identifier: Apache-2.0 OR MIT
3
4use kurbo::{PathEl, Point};
5
6/// Helper trait for converting cubic splines to paths.
7pub trait SplineToPath {
8    fn get(&self, index: usize) -> Point;
9    fn len(&self) -> usize;
10
11    fn to_path(&self, is_closed: bool, path: &mut Vec<PathEl>) -> Option<()> {
12        use PathEl::*;
13        if self.len() == 0 {
14            return None;
15        }
16        path.push(MoveTo(self.get(0)));
17        let n_vertices = self.len() / 3;
18        let mut add_element = |from_vertex, to_vertex| {
19            let from_index = 3 * from_vertex;
20            let to_index = 3 * to_vertex;
21            let p0: Point = self.get(from_index);
22            let p1: Point = self.get(to_index);
23            let mut c0: Point = self.get(from_index + 2);
24            c0.x += p0.x;
25            c0.y += p0.y;
26            let mut c1: Point = self.get(to_index + 1);
27            c1.x += p1.x;
28            c1.y += p1.y;
29            if c0 == p0 && c1 == p1 {
30                path.push(LineTo(p1));
31            } else {
32                path.push(CurveTo(c0, c1, p1));
33            }
34        };
35        for i in 1..n_vertices {
36            add_element(i - 1, i);
37        }
38        if is_closed && n_vertices != 0 {
39            add_element(n_vertices - 1, 0);
40            path.push(ClosePath);
41        }
42        Some(())
43    }
44}
45
46/// Converts a static spline to a path.
47impl SplineToPath for &'_ [Point] {
48    fn len(&self) -> usize {
49        self.as_ref().len()
50    }
51
52    fn get(&self, index: usize) -> Point {
53        self[index]
54    }
55}
56
57/// Produces a path by lerping between two sets of points.
58impl SplineToPath for (&'_ [Point], &'_ [Point], f64) {
59    fn len(&self) -> usize {
60        self.0.len().min(self.1.len())
61    }
62
63    fn get(&self, index: usize) -> Point {
64        // TODO: This definitely shouldn't be a lerp
65        self.0[index].lerp(self.1[index], self.2)
66    }
67}