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use super::kernels::*;
use crate::coords_iter::CoordsIter;
use crate::utils::EitherIter;
use crate::{CoordNum, LineString, Point};
use geo_types::PointsIter;
use std::iter::Rev;
/// Iterates through a list of `Point`s
#[allow(missing_debug_implementations)]
pub struct Points<'a, T>(pub(crate) EitherIter<PointsIter<'a, T>, Rev<PointsIter<'a, T>>>)
where
T: CoordNum + 'a;
impl<'a, T> Iterator for Points<'a, T>
where
T: CoordNum,
{
type Item = Point<T>;
#[inline]
fn next(&mut self) -> Option<Self::Item> {
self.0.next()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.0.size_hint()
}
}
impl<'a, T> ExactSizeIterator for Points<'a, T>
where
T: CoordNum,
{
#[inline]
fn len(&self) -> usize {
self.0.len()
}
}
/// How a linestring is wound, clockwise or counter-clockwise
#[derive(PartialEq, Clone, Debug, Eq, Copy)]
pub enum WindingOrder {
Clockwise,
CounterClockwise,
}
impl WindingOrder {
#[allow(dead_code)]
pub(crate) fn inverse(&self) -> Self {
match self {
WindingOrder::Clockwise => WindingOrder::CounterClockwise,
WindingOrder::CounterClockwise => WindingOrder::Clockwise,
}
}
}
/// Determine and operate on how a [`LineString`] is
/// wound. This functionality, and our implementation is
/// based on [CGAL's Polygon_2::orientation].
///
/// [CGAL's Polygon_2::orientation]: //doc.cgal.org/latest/Polygon/classCGAL_1_1Polygon__2.html#a4ce8b4b8395406243ac16c2a120ffc15
pub trait Winding {
type Scalar: CoordNum;
/// Return the winding order of this object if it
/// contains at least three distinct coordinates, and
/// `None` otherwise.
fn winding_order(&self) -> Option<WindingOrder>;
/// True iff this is wound clockwise
fn is_cw(&self) -> bool {
self.winding_order() == Some(WindingOrder::Clockwise)
}
/// True iff this is wound counterclockwise
fn is_ccw(&self) -> bool {
self.winding_order() == Some(WindingOrder::CounterClockwise)
}
/// Iterate over the points in a clockwise order
///
/// The object isn't changed, and the points are returned either in order, or in reverse
/// order, so that the resultant order makes it appear clockwise
fn points_cw(&self) -> Points<Self::Scalar>;
/// Iterate over the points in a counter-clockwise order
///
/// The object isn't changed, and the points are returned either in order, or in reverse
/// order, so that the resultant order makes it appear counter-clockwise
fn points_ccw(&self) -> Points<Self::Scalar>;
/// Change this object's points so they are in clockwise winding order
fn make_cw_winding(&mut self);
/// Change this line's points so they are in counterclockwise winding order
fn make_ccw_winding(&mut self);
/// Return a clone of this object, but in the specified winding order
fn clone_to_winding_order(&self, winding_order: WindingOrder) -> Self
where
Self: Sized + Clone,
{
let mut new: Self = self.clone();
new.make_winding_order(winding_order);
new
}
/// Change the winding order so that it is in this winding order
fn make_winding_order(&mut self, winding_order: WindingOrder) {
match winding_order {
WindingOrder::Clockwise => self.make_cw_winding(),
WindingOrder::CounterClockwise => self.make_ccw_winding(),
}
}
}
impl<T, K> Winding for LineString<T>
where
T: HasKernel<Ker = K>,
K: Kernel<T>,
{
type Scalar = T;
fn winding_order(&self) -> Option<WindingOrder> {
// If linestring has at most 3 coords, it is either
// not closed, or is at most two distinct points.
// Either way, the WindingOrder is unspecified.
if self.coords_count() < 4 || !self.is_closed() {
return None;
}
let increment = |x: &mut usize| {
*x += 1;
if *x >= self.coords_count() {
*x = 0;
}
};
let decrement = |x: &mut usize| {
if *x == 0 {
*x = self.coords_count() - 1;
} else {
*x -= 1;
}
};
use crate::utils::least_index;
let i = least_index(&self.0);
let mut next = i;
increment(&mut next);
while self.0[next] == self.0[i] {
if next == i {
// We've looped too much. There aren't
// enough unique coords to compute orientation.
return None;
}
increment(&mut next);
}
let mut prev = i;
decrement(&mut prev);
while self.0[prev] == self.0[i] {
// Note: we don't need to check if prev == i as
// the previous loop succeeded, and so we have
// at least two distinct elements in the list
decrement(&mut prev);
}
match K::orient2d(self.0[prev], self.0[i], self.0[next]) {
Orientation::CounterClockwise => Some(WindingOrder::CounterClockwise),
Orientation::Clockwise => Some(WindingOrder::Clockwise),
_ => None,
}
}
/// Iterate over the points in a clockwise order
///
/// The Linestring isn't changed, and the points are returned either in order, or in reverse
/// order, so that the resultant order makes it appear clockwise
fn points_cw(&self) -> Points<Self::Scalar> {
match self.winding_order() {
Some(WindingOrder::CounterClockwise) => Points(EitherIter::B(self.points().rev())),
_ => Points(EitherIter::A(self.points())),
}
}
/// Iterate over the points in a counter-clockwise order
///
/// The Linestring isn't changed, and the points are returned either in order, or in reverse
/// order, so that the resultant order makes it appear counter-clockwise
fn points_ccw(&self) -> Points<Self::Scalar> {
match self.winding_order() {
Some(WindingOrder::Clockwise) => Points(EitherIter::B(self.points().rev())),
_ => Points(EitherIter::A(self.points())),
}
}
/// Change this line's points so they are in clockwise winding order
fn make_cw_winding(&mut self) {
if let Some(WindingOrder::CounterClockwise) = self.winding_order() {
self.0.reverse();
}
}
/// Change this line's points so they are in counterclockwise winding order
fn make_ccw_winding(&mut self) {
if let Some(WindingOrder::Clockwise) = self.winding_order() {
self.0.reverse();
}
}
}
#[cfg(test)]
mod test {
use super::*;
use crate::Point;
#[test]
fn robust_winding_float() {
// 3 points forming a triangle
let a = Point::new(0., 0.);
let b = Point::new(2., 0.);
let c = Point::new(1., 2.);
// Verify open linestrings return None
let mut ls = LineString::from(vec![a.0, b.0, c.0]);
assert!(ls.winding_order().is_none());
ls.0.push(ls.0[0]);
assert_eq!(ls.winding_order(), Some(WindingOrder::CounterClockwise));
ls.make_cw_winding();
assert_eq!(ls.winding_order(), Some(WindingOrder::Clockwise));
}
#[test]
fn robust_winding_integer() {
// 3 points forming a triangle
let a = Point::new(0i64, 0);
let b = Point::new(2, 0);
let c = Point::new(1, 2);
// Verify open linestrings return None
let mut ls = LineString::from(vec![a.0, b.0, c.0]);
assert!(ls.winding_order().is_none());
ls.0.push(ls.0[0]);
assert!(ls.is_ccw());
let ccw_ls: Vec<_> = ls.points_ccw().collect();
ls.make_cw_winding();
assert!(ls.is_cw());
assert_eq!(&ls.points_ccw().collect::<Vec<_>>(), &ccw_ls,);
}
}