1//! Closed shape thick segment iterator.
2
3use crate::{
4 geometry::Point,
5 primitives::common::{LineJoin, StrokeOffset, ThickSegment},
6};
7
8/// Closed shape thick segments iterator.
9///
10/// Iterates over all line segments in the polyline, returning a 6-sided shape as a [`ThickSegment`]
11/// for each segment. These are tessellated and are used to produce scanline intersections.
12///
13/// Unlike [`ThickSegmentIter`], this iterator closes the shape with a final line between the
14/// start and end points.
15///
16/// [`ThickSegment`]: super::thick_segment::ThickSegment
17/// [`ThickSegmentIter`]: super::thick_segment_iter::ThickSegmentIter
18#[derive(Clone, Debug)]
19#[cfg_attr(feature = "defmt", derive(::defmt::Format))]
20pub struct ClosedThickSegmentIter<'a> {
21 windows: core::slice::Windows<'a, Point>,
22 first_join: LineJoin,
23 start_join: LineJoin,
24 width: u32,
25 stroke_offset: StrokeOffset,
26 points: &'a [Point],
27 stop: bool,
28 idx: usize,
29}
30
31static EMPTY: &[Point; 0] = &[];
32
33impl<'a> ClosedThickSegmentIter<'a> {
34 /// Create a new thick segments iterator.
35 pub fn new(points: &'a [Point], width: u32, stroke_offset: StrokeOffset) -> Self {
36 if let [start, end] = points {
37 // Single line segment.
38 let start_join = LineJoin::start(*start, *end, width, stroke_offset);
39
40 Self {
41 windows: EMPTY.windows(3),
42 start_join,
43 width,
44 stroke_offset,
45 points,
46 stop: false,
47 first_join: start_join,
48 idx: 1,
49 }
50 } else if points.is_empty() {
51 Self::empty()
52 } else {
53 let windows = points.windows(3);
54
55 let start_join = LineJoin::from_points(
56 *points.last().unwrap(),
57 points[0],
58 points[1],
59 width,
60 stroke_offset,
61 );
62
63 Self {
64 windows,
65 start_join,
66 width,
67 stroke_offset,
68 points,
69 stop: false,
70 first_join: start_join,
71 idx: 1,
72 }
73 }
74 }
75
76 /// Empty
77 fn empty() -> Self {
78 Self {
79 windows: EMPTY.windows(3),
80 start_join: LineJoin::empty(),
81 width: 0,
82 stroke_offset: StrokeOffset::None,
83 points: EMPTY,
84 stop: true,
85 first_join: LineJoin::empty(),
86 idx: 1,
87 }
88 }
89}
90
91impl<'a> Iterator for ClosedThickSegmentIter<'a> {
92 type Item = ThickSegment;
93
94 fn next(&mut self) -> Option<Self::Item> {
95 if self.stop {
96 return None;
97 }
98
99 self.idx += 1;
100
101 let end_join = if let Some([start, mid, end]) = self.windows.next() {
102 LineJoin::from_points(*start, *mid, *end, self.width, self.stroke_offset)
103 } else if self.idx == self.points.len() {
104 // The join at the end of the line. This will become the start join of the closing
105 // segment.
106 let start = self.points.get(self.points.len() - 2)?;
107 let mid = self.points.last()?;
108 let end = self.points.first()?;
109
110 LineJoin::from_points(*start, *mid, *end, self.width, self.stroke_offset)
111 } else {
112 // Final closing line between start/end.
113 self.stop = true;
114
115 self.first_join
116 };
117
118 let segment = ThickSegment::new(self.start_join, end_join);
119
120 self.start_join = end_join;
121
122 Some(segment)
123 }
124}
125