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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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//! Machinery to compute distances between animatable values.
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use app_units::Au;
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use euclid::default::Size2D;
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use std::iter::Sum;
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use std::ops::Add;
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/// A trait to compute squared distances between two animatable values.
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///
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/// This trait is derivable with `#[derive(ComputeSquaredDistance)]`. The derived
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/// implementation uses a `match` expression with identical patterns for both
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/// `self` and `other`, calling `ComputeSquaredDistance::compute_squared_distance`
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/// on each fields of the values.
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///
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/// If a variant is annotated with `#[animation(error)]`, the corresponding
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/// `match` arm returns an error.
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///
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/// Trait bounds for type parameter `Foo` can be opted out of with
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/// `#[animation(no_bound(Foo))]` on the type definition, trait bounds for
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/// fields can be opted into with `#[distance(field_bound)]` on the field.
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pub trait ComputeSquaredDistance {
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/// Computes the squared distance between two animatable values.
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()>;
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}
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/// A distance between two animatable values.
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#[derive(Add, Clone, Copy, Debug, From)]
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pub struct SquaredDistance {
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value: f64,
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}
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impl SquaredDistance {
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/// Returns a squared distance from its square root.
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#[inline]
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pub fn from_sqrt(sqrt: f64) -> Self {
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Self { value: sqrt * sqrt }
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}
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}
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impl ComputeSquaredDistance for u16 {
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#[inline]
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
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Ok(SquaredDistance::from_sqrt(
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((*self as f64) - (*other as f64)).abs(),
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))
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}
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}
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impl ComputeSquaredDistance for i32 {
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#[inline]
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
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Ok(SquaredDistance::from_sqrt((*self - *other).abs() as f64))
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}
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}
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impl ComputeSquaredDistance for f32 {
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#[inline]
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
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Ok(SquaredDistance::from_sqrt((*self - *other).abs() as f64))
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}
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}
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impl ComputeSquaredDistance for f64 {
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#[inline]
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
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Ok(SquaredDistance::from_sqrt((*self - *other).abs()))
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}
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}
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impl ComputeSquaredDistance for Au {
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#[inline]
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
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self.0.compute_squared_distance(&other.0)
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}
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}
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impl<T> ComputeSquaredDistance for Box<T>
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where
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T: ComputeSquaredDistance,
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{
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#[inline]
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
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(**self).compute_squared_distance(&**other)
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}
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}
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impl<T> ComputeSquaredDistance for Option<T>
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where
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T: ComputeSquaredDistance,
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{
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#[inline]
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
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match (self.as_ref(), other.as_ref()) {
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(Some(this), Some(other)) => this.compute_squared_distance(other),
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(None, None) => Ok(SquaredDistance::from_sqrt(0.)),
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_ => Err(()),
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}
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}
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}
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impl<T> ComputeSquaredDistance for Size2D<T>
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where
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T: ComputeSquaredDistance,
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{
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#[inline]
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fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
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Ok(self.width.compute_squared_distance(&other.width)? +
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self.height.compute_squared_distance(&other.height)?)
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}
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}
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impl SquaredDistance {
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/// Returns the square root of this squared distance.
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#[inline]
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pub fn sqrt(self) -> f64 {
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self.value.sqrt()
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}
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}
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impl Sum for SquaredDistance {
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fn sum<I>(iter: I) -> Self
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where
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I: Iterator<Item = Self>,
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{
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iter.fold(SquaredDistance::from_sqrt(0.), Add::add)
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}
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}
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