Per the CSS Animations spec, the animation-timing-function property
describes how the animation progresses between each pair of keyframes,
not as an overall effect-level timing function.
Previously we set it as the effect-level timing function on the
AnimationEffect, which caused easing to be applied to the global
animation progress. This made animations with multiple keyframes
"pause" at the start and end of the full animation cycle instead of
easing smoothly between each pair of keyframes.
Now we:
- Store per-keyframe easing in ResolvedKeyFrame from @keyframes rules
- Store the default easing on CSSAnimation instead of on the effect
- Apply per-keyframe easing to the interval progress during
interpolation, falling back to the CSS animation's default easing
- Also store per-keyframe easing from JS-created KeyframeEffects to
avoid incorrectly applying CSS default easing to replaced effects
This reverts 0e3487b9ab.
Back when I made that change, I thought we could make our StyleValue
classes match the typed-om definitions directly. However, they have
different requirements. Typed-om types need to be mutable and GCed,
whereas StyleValues are immutable and ideally wouldn't require a JS VM.
While I was already making such a cataclysmic change, I've moved it into
the StyleValues directory, because it *not* being there has bothered me
for a long time. 😅
Resulting in a massive rename across almost everywhere! Alongside the
namespace change, we now have the following names:
* JS::NonnullGCPtr -> GC::Ref
* JS::GCPtr -> GC::Ptr
* JS::HeapFunction -> GC::Function
* JS::CellImpl -> GC::Cell
* JS::Handle -> GC::Root
