style/values/computed/
ratio.rs

1/* This Source Code Form is subject to the terms of the Mozilla Public
2 * License, v. 2.0. If a copy of the MPL was not distributed with this
3 * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
4
5//! `<ratio>` computed values.
6
7use crate::values::animated::{Animate, Procedure};
8use crate::values::computed::NonNegativeNumber;
9use crate::values::distance::{ComputeSquaredDistance, SquaredDistance};
10use crate::values::generics::ratio::Ratio as GenericRatio;
11use crate::values::generics::NonNegative;
12use crate::Zero;
13use std::cmp::Ordering;
14
15/// A computed <ratio> value.
16pub type Ratio = GenericRatio<NonNegativeNumber>;
17
18impl PartialOrd for Ratio {
19    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
20        f64::partial_cmp(
21            &((self.0).0 as f64 * (other.1).0 as f64),
22            &((self.1).0 as f64 * (other.0).0 as f64),
23        )
24    }
25}
26
27impl Ratio {
28    /// Returns the f32 value by dividing the first value by the second one.
29    #[inline]
30    fn to_f32(&self) -> f32 {
31        debug_assert!(!self.is_degenerate());
32        (self.0).0 / (self.1).0
33    }
34    /// Returns a new Ratio.
35    #[inline]
36    pub fn new(a: f32, b: f32) -> Self {
37        GenericRatio(a.into(), b.into())
38    }
39}
40
41/// https://drafts.csswg.org/css-values/#combine-ratio
42impl Animate for Ratio {
43    fn animate(&self, other: &Self, procedure: Procedure) -> Result<Self, ()> {
44        // If either <ratio> is degenerate, the values cannot be interpolated.
45        if self.is_degenerate() || other.is_degenerate() {
46            return Err(());
47        }
48
49        // Addition of <ratio>s is not possible, and based on
50        // https://drafts.csswg.org/css-values-4/#not-additive,
51        // we simply use the first value as the result value.
52        // Besides, the procedure for accumulation should be identical to addition here.
53        if matches!(procedure, Procedure::Add | Procedure::Accumulate { .. }) {
54            return Ok(self.clone());
55        }
56
57        // The interpolation of a <ratio> is defined by converting each <ratio> to a number by
58        // dividing the first value by the second (so a ratio of 3 / 2 would become 1.5), taking
59        // the logarithm of that result (so the 1.5 would become approximately 0.176), then
60        // interpolating those values.
61        //
62        // The result during the interpolation is converted back to a <ratio> by inverting the
63        // logarithm, then interpreting the result as a <ratio> with the result as the first value
64        // and 1 as the second value.
65        let start = self.to_f32().ln();
66        let end = other.to_f32().ln();
67        let e = std::f32::consts::E;
68        let result = e.powf(start.animate(&end, procedure)?);
69        // The range of the result is [0, inf), based on the easing function.
70        if result.is_zero() || result.is_infinite() {
71            return Err(());
72        }
73        Ok(GenericRatio(NonNegative(result), NonNegative(1.0)))
74    }
75}
76
77impl ComputeSquaredDistance for Ratio {
78    fn compute_squared_distance(&self, other: &Self) -> Result<SquaredDistance, ()> {
79        if self.is_degenerate() || other.is_degenerate() {
80            return Err(());
81        }
82        // Use the distance of their logarithm values. (This is used by testing, so don't
83        // need to care about the base. Here we use the same base as that in animate().)
84        self.to_f32()
85            .ln()
86            .compute_squared_distance(&other.to_f32().ln())
87    }
88}
style/values/computed/ratio.rs

style/values/computed/
ratio.rs
