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