cairo/
paths.rs

1// Take a look at the license at the top of the repository in the LICENSE file.
2
3use std::{iter::FusedIterator, ptr};
4
5use crate::{ffi, PathDataType};
6
7#[derive(Debug)]
8#[doc(alias = "cairo_path_t")]
9pub struct Path(ptr::NonNull<ffi::cairo_path_t>);
10
11impl Path {
12    #[inline]
13    pub fn as_ptr(&self) -> *mut ffi::cairo_path_t {
14        self.0.as_ptr()
15    }
16
17    #[inline]
18    pub unsafe fn from_raw_full(pointer: *mut ffi::cairo_path_t) -> Path {
19        debug_assert!(!pointer.is_null());
20        Path(ptr::NonNull::new_unchecked(pointer))
21    }
22
23    pub fn iter(&self) -> PathSegments {
24        use std::slice;
25
26        unsafe {
27            let ptr: *mut ffi::cairo_path_t = self.as_ptr();
28            let length = (*ptr).num_data as usize;
29            let data_ptr = (*ptr).data;
30            let data_vec = if length != 0 && !data_ptr.is_null() {
31                slice::from_raw_parts(data_ptr, length)
32            } else {
33                &[]
34            };
35
36            PathSegments {
37                data: data_vec,
38                i: 0,
39                num_data: length,
40            }
41        }
42    }
43}
44
45impl Drop for Path {
46    #[inline]
47    fn drop(&mut self) {
48        unsafe {
49            ffi::cairo_path_destroy(self.as_ptr());
50        }
51    }
52}
53
54#[derive(Debug, Clone, Copy, PartialEq)]
55pub enum PathSegment {
56    MoveTo((f64, f64)),
57    LineTo((f64, f64)),
58    CurveTo((f64, f64), (f64, f64), (f64, f64)),
59    ClosePath,
60}
61
62pub struct PathSegments<'a> {
63    data: &'a [ffi::cairo_path_data],
64    i: usize,
65    num_data: usize,
66}
67
68impl Iterator for PathSegments<'_> {
69    type Item = PathSegment;
70
71    fn next(&mut self) -> Option<PathSegment> {
72        if self.i >= self.num_data {
73            return None;
74        }
75
76        unsafe {
77            let res = match PathDataType::from(self.data[self.i].header.data_type) {
78                PathDataType::MoveTo => PathSegment::MoveTo(to_tuple(&self.data[self.i + 1].point)),
79                PathDataType::LineTo => PathSegment::LineTo(to_tuple(&self.data[self.i + 1].point)),
80                PathDataType::CurveTo => PathSegment::CurveTo(
81                    to_tuple(&self.data[self.i + 1].point),
82                    to_tuple(&self.data[self.i + 2].point),
83                    to_tuple(&self.data[self.i + 3].point),
84                ),
85                PathDataType::ClosePath => PathSegment::ClosePath,
86                PathDataType::__Unknown(x) => panic!("Unknown value: {x}"),
87            };
88
89            self.i += self.data[self.i].header.length as usize;
90
91            Some(res)
92        }
93    }
94}
95
96impl FusedIterator for PathSegments<'_> {}
97
98fn to_tuple(pair: &[f64; 2]) -> (f64, f64) {
99    (pair[0], pair[1])
100}
101
102#[cfg(test)]
103mod tests {
104    use super::*;
105    use crate::{context::*, enums::Format, image_surface::*};
106
107    fn make_cr() -> Context {
108        let surface = ImageSurface::create(Format::Rgb24, 1, 1).unwrap();
109
110        Context::new(&surface).expect("Can't create a Cairo context")
111    }
112
113    fn assert_path_equals_segments(expected: &Path, actual: &[PathSegment]) {
114        // First ensure the lengths are equal
115
116        let expected_iter = expected.iter();
117        let actual_iter = actual.iter();
118
119        assert_eq!(expected_iter.count(), actual_iter.count());
120
121        // Then actually compare the contents
122
123        let expected_iter = expected.iter();
124        let actual_iter = actual.iter();
125
126        let iter = expected_iter.zip(actual_iter);
127        for (e, a) in iter {
128            assert_eq!(e, *a);
129        }
130    }
131
132    #[test]
133    fn empty_path_doesnt_iter() {
134        let cr = make_cr();
135
136        let path = cr.copy_path().expect("Invalid context");
137
138        assert!(path.iter().next().is_none());
139    }
140
141    #[test]
142    fn moveto() {
143        let cr = make_cr();
144
145        cr.move_to(1.0, 2.0);
146
147        let path = cr.copy_path().expect("Invalid path");
148
149        assert_path_equals_segments(&path, &[PathSegment::MoveTo((1.0, 2.0))]);
150    }
151
152    #[test]
153    fn moveto_lineto_moveto() {
154        let cr = make_cr();
155
156        cr.move_to(1.0, 2.0);
157        cr.line_to(3.0, 4.0);
158        cr.move_to(5.0, 6.0);
159
160        let path = cr.copy_path().expect("Invalid path");
161
162        assert_path_equals_segments(
163            &path,
164            &[
165                PathSegment::MoveTo((1.0, 2.0)),
166                PathSegment::LineTo((3.0, 4.0)),
167                PathSegment::MoveTo((5.0, 6.0)),
168            ],
169        );
170    }
171
172    #[test]
173    fn moveto_closepath() {
174        let cr = make_cr();
175
176        cr.move_to(1.0, 2.0);
177        cr.close_path();
178
179        let path = cr.copy_path().expect("Invalid path");
180
181        // Note that Cairo represents a close_path as closepath+moveto,
182        // so that the next subpath will have a starting point,
183        // from the extra moveto.
184        assert_path_equals_segments(
185            &path,
186            &[
187                PathSegment::MoveTo((1.0, 2.0)),
188                PathSegment::ClosePath,
189                PathSegment::MoveTo((1.0, 2.0)),
190            ],
191        );
192    }
193    #[test]
194    fn curveto_closed_subpath_lineto() {
195        let cr = make_cr();
196
197        cr.move_to(1.0, 2.0);
198        cr.curve_to(3.0, 4.0, 5.0, 6.0, 7.0, 8.0);
199        cr.close_path();
200        cr.line_to(9.0, 10.0);
201
202        let path = cr.copy_path().expect("Invalid path");
203
204        assert_path_equals_segments(
205            &path,
206            &[
207                PathSegment::MoveTo((1.0, 2.0)),
208                PathSegment::CurveTo((3.0, 4.0), (5.0, 6.0), (7.0, 8.0)),
209                PathSegment::ClosePath,
210                PathSegment::MoveTo((1.0, 2.0)),
211                PathSegment::LineTo((9.0, 10.0)),
212            ],
213        );
214    }
215}