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style: Cleanup and add references to Quaternion::animate.

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No functional change, but I did this while searching for the bug.

Bug: 1459403
Reviewed-by: hiro
MozReview-Commit-ID: KsJxFoYaOq1
This commit is contained in:
Emilio Cobos Álvarez 2018-05-26 23:40:45 +02:00
parent 99d4e7b65c
commit 6ddb04a483
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GPG key ID: 056B727BB9C1027C
1 changed files with 34 additions and 23 deletions
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57
components/style/properties/helpers/animated_properties.mako.rs
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@ -1820,12 +1820,16 @@ impl Animate for Quaternion {
use std::f64; use std::f64;
let (this_weight, other_weight) = procedure.weights(); let (this_weight, other_weight) = procedure.weights();
debug_assert!((this_weight + other_weight - 1.0f64).abs() <= f64::EPSILON || debug_assert!(
other_weight == 1.0f64 || other_weight == 0.0f64, (this_weight + other_weight - 1.0f64).abs() <= f64::EPSILON ||
"animate should only be used for interpolating or accumulating transforms"); other_weight == 1.0f64 || other_weight == 0.0f64,
"animate should only be used for interpolating or accumulating transforms"
);
// We take a specialized code path for accumulation (where other_weight is 1) // We take a specialized code path for accumulation (where other_weight
if other_weight == 1.0 { // is 1).
if let Procedure::Accumulate { .. } = procedure {
debug_assert_eq!(other_weight, 1.0);
if this_weight == 0.0 { if this_weight == 0.0 {
return Ok(*other); return Ok(*other);
} }
@ -1856,32 +1860,39 @@ impl Animate for Quaternion {
)); ));
} }
let mut product = self.0 * other.0 + // Straight from gfxQuaternion::Slerp.
self.1 * other.1 + //
self.2 * other.2 + // Dot product, clamped between -1 and 1.
self.3 * other.3; let dot =
(self.0 * other.0 +
self.1 * other.1 +
self.2 * other.2 +
self.3 * other.3)
.min(1.0).max(-1.0);
// Clamp product to -1.0 <= product <= 1.0 if dot == 1.0 {
product = product.min(1.0);
product = product.max(-1.0);
if product == 1.0 {
return Ok(*self); return Ok(*self);
} }
let theta = product.acos(); let theta = dot.acos();
let w = (other_weight * theta).sin() * 1.0 / (1.0 - product * product).sqrt(); let rsintheta = 1.0 / (1.0 - dot * dot).sqrt();
let mut a = *self; let right_weight = (other_weight * theta).sin() * rsintheta;
let mut b = *other; let left_weight = (other_weight * theta).cos() - dot * right_weight;
let mut result = Quaternion(0., 0., 0., 0.,);
let mut left = *self;
let mut right = *other;
% for i in range(4): % for i in range(4):
a.${i} *= (other_weight * theta).cos() - product * w; left.${i} *= left_weight;
b.${i} *= w; right.${i} *= right_weight;
result.${i} = a.${i} + b.${i};
% endfor % endfor
Ok(result) Ok(Quaternion(
left.0 + right.0,
left.1 + right.1,
left.2 + right.2,
left.3 + right.3,
))
} }
} }