embedded_graphics/primitives/common/
thick_segment_iter.rs

1//! Thick segment iterator.
2
3use crate::{
4    geometry::Point,
5    primitives::common::{JoinKind, LineJoin, StrokeOffset, ThickSegment},
6};
7
8/// 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/// [`ThickSegment`]: super::thick_segment::ThickSegment
14#[derive(Clone, Debug)]
15#[cfg_attr(feature = "defmt", derive(::defmt::Format))]
16pub struct ThickSegmentIter<'a> {
17    windows: core::slice::Windows<'a, Point>,
18    start_join: LineJoin,
19    end_join: LineJoin,
20    width: u32,
21    stroke_offset: StrokeOffset,
22    points: &'a [Point],
23    stop: bool,
24}
25
26static EMPTY: &[Point; 0] = &[];
27
28impl<'a> ThickSegmentIter<'a> {
29    /// Create a new thick segments iterator.
30    pub fn new(points: &'a [Point], width: u32, _stroke_offset: StrokeOffset) -> Self {
31        // Fix stroke alignment to None. There are issues with degenerate joints when using
32        // Inside/Outside stroke alignment on polylines, so this is disabled for now.
33        let stroke_offset = StrokeOffset::None;
34
35        let mut windows = points.windows(3);
36
37        if let Some([start, mid, end]) = windows.next() {
38            let start_join = LineJoin::start(*start, *mid, width, stroke_offset);
39            let end_join = LineJoin::from_points(*start, *mid, *end, width, stroke_offset);
40
41            Self {
42                windows,
43                start_join,
44                end_join,
45                width,
46                stroke_offset,
47                points,
48                stop: false,
49            }
50        } else if let [start, end] = points {
51            // Single line segment.
52            let start_join = LineJoin::start(*start, *end, width, stroke_offset);
53            let end_join = LineJoin::end(*start, *end, width, stroke_offset);
54
55            Self {
56                windows: EMPTY.windows(3),
57                start_join,
58                end_join,
59                width,
60                stroke_offset,
61                points,
62                stop: false,
63            }
64        } else {
65            // Points must be at least 2 in length to make a polyline iterator out of.
66            Self::empty()
67        }
68    }
69
70    /// Empty
71    fn empty() -> Self {
72        Self {
73            windows: EMPTY.windows(3),
74            start_join: LineJoin::empty(),
75            end_join: LineJoin::empty(),
76            width: 0,
77            stroke_offset: StrokeOffset::None,
78            points: EMPTY,
79            stop: true,
80        }
81    }
82}
83
84impl<'a> Iterator for ThickSegmentIter<'a> {
85    type Item = ThickSegment;
86
87    fn next(&mut self) -> Option<Self::Item> {
88        if self.stop {
89            return None;
90        }
91
92        let segment = ThickSegment::new(self.start_join, self.end_join);
93
94        self.start_join = self.end_join;
95
96        if let Some([start, mid, end]) = self.windows.next() {
97            self.end_join =
98                LineJoin::from_points(*start, *mid, *end, self.width, self.stroke_offset);
99        } else if self.end_join.kind != JoinKind::End {
100            let start = *self.points.get(self.points.len() - 2)?;
101            let end = *self.points.last()?;
102
103            self.end_join = LineJoin::end(start, end, self.width, self.stroke_offset);
104        } else {
105            self.stop = true;
106        }
107
108        Some(segment)
109    }
110}
embedded_graphics/primitives/common/thick_segment_iter.rs

embedded_graphics/primitives/common/
thick_segment_iter.rs
