79 lines
2.3 KiB
Rust
79 lines
2.3 KiB
Rust
// pathfinder/geometry/src/monotonic.rs
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//
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// Copyright © 2019 The Pathfinder Project Developers.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! Converts paths to monotonically increasing/decreasing segments in Y.
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use crate::segment::{Segment, SegmentKind};
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use arrayvec::ArrayVec;
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pub struct MonotonicConversionIter<I>
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where
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I: Iterator<Item = Segment>,
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{
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iter: I,
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buffer: ArrayVec<[Segment; 2]>,
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}
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impl<I> Iterator for MonotonicConversionIter<I>
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where
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I: Iterator<Item = Segment>,
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{
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type Item = Segment;
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#[inline]
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fn next(&mut self) -> Option<Segment> {
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if let Some(segment) = self.buffer.pop() {
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return Some(segment);
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}
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let segment = self.iter.next()?;
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match segment.kind {
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SegmentKind::None => self.next(),
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SegmentKind::Line => Some(segment),
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SegmentKind::Cubic => self.handle_cubic(&segment),
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SegmentKind::Quadratic => {
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// TODO(pcwalton): Don't degree elevate!
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self.handle_cubic(&segment.to_cubic())
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}
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}
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}
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}
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impl<I> MonotonicConversionIter<I>
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where
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I: Iterator<Item = Segment>,
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{
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#[inline]
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pub fn new(iter: I) -> MonotonicConversionIter<I> {
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MonotonicConversionIter {
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iter,
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buffer: ArrayVec::new(),
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}
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}
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pub fn handle_cubic(&mut self, segment: &Segment) -> Option<Segment> {
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match segment.as_cubic_segment().y_extrema() {
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(Some(t0), Some(t1)) => {
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let (segments_01, segment_2) = segment.as_cubic_segment().split(t1);
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self.buffer.push(segment_2);
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let (segment_0, segment_1) = segments_01.as_cubic_segment().split(t0 / t1);
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self.buffer.push(segment_1);
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Some(segment_0)
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}
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(Some(t0), None) | (None, Some(t0)) => {
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let (segment_0, segment_1) = segment.as_cubic_segment().split(t0);
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self.buffer.push(segment_1);
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Some(segment_0)
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}
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(None, None) => Some(*segment),
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}
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}
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}
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