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style: Avoid infinite output progress after applying the easing function

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The output progress of easing functions could be inf or -inf, per spec,
https://drafts.csswg.org/css-easing-2/#output-progress-value.

But we should avoid using infinity to calculate interpolation or use
the infinite progress in Web Animations API, per the spec issue comments:
https://github.com/w3c/csswg-drafts/issues/8344#issuecomment-1399033481

Differential Revision: https://phabricator.services.mozilla.com/D167342
This commit is contained in:
Boris Chiou 2023-01-23 22:02:23 +00:00 • committed by Martin Robinson
parent bb55e923bb
commit fffb3c0830
1 changed files with 15 additions and 3 deletions
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18
components/style/values/computed/easing.rs
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@ -69,7 +69,7 @@ impl ComputedTimingFunction {
/// The output of the timing function given the progress ratio of this animation.
pub fn calculate_output(&self, progress: f64, before_flag: BeforeFlag, epsilon: f64) -> f64 {
match self {
let progress = match self {
TimingFunction::CubicBezier { x1, y1, x2, y2 } => {
Bezier::calculate_bezier_output(progress, epsilon, *x1, *y1, *x2, *y2)
},
@ -78,7 +78,7 @@ impl ComputedTimingFunction {
},
TimingFunction::LinearFunction(function) => function.at(progress as f32).into(),
TimingFunction::Keyword(keyword) => match keyword {
TimingKeyword::Linear => return progress,
TimingKeyword::Linear => progress,
TimingKeyword::Ease => {
Bezier::calculate_bezier_output(progress, epsilon, 0.25, 0.1, 0.25, 1.)
},
@ -92,6 +92,18 @@ impl ComputedTimingFunction {
Bezier::calculate_bezier_output(progress, epsilon, 0.42, 0., 0.58, 1.)
},
},
}
};
// The output progress value of an easing function is a real number in the range:
// [-inf, inf].
// https://drafts.csswg.org/css-easing-1/#output-progress-value
//
// However, we expect to use the finite progress for interpolation and web-animations
// https://drafts.csswg.org/css-values-4/#interpolation
// https://drafts.csswg.org/web-animations-1/#dom-computedeffecttiming-progress
//
// So we clamp the infinite progress, per the spec issue:
// https://github.com/w3c/csswg-drafts/issues/8344
progress.min(f64::MAX).max(f64::MIN)
}
}