Re: [csswg-drafts] [css-contain-3][css-animations][css-transitions] Isolate animation side-effects? (#6398)

> What if we isolate all side-effects that happen because of stuff that's animating, such that it can't trigger new animations:
> 
> * Let the _base style_ be the style as it would be without _any_ animation effects applied (of any kind), inheriting from the base style of the parent.

I've certainly come across a few cases where having an API to get the un-animated style would be very useful so introducing this concept at a spec level might be a useful step in that direction.

> * Let the _before-change style_ be the base style as of the previous style change event, inheriting from the before-change style of the parent. (I.e. just remember the previous base style).

I'm not sure about this. It's been a while since I've touched this code but from memory the following clause from the CSS Transitions spec is quite important:

> except with any styles derived from declarative animations such as CSS Transitions, CSS Animations ([CSS3-ANIMATIONS]), and SMIL Animations ([SMIL-ANIMATION], [SVG11]) updated to the current time.

Without that, animations end up triggering transitions.

> Not sure how web-compatible this is, or if this loses us any crucial aspect of the current specified behavior. On the other hand, the interop situation seems pretty poor in this area, and no browser seems to implement the current before/after change style correctly, so there might be wiggle-room.

I think Firefox should be correct regarding the before/after change styles part including inheritance--the only area where I'm aware it's wrong is with regards to context-sensitive properties like `font-size`.


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Received on Tuesday, 22 June 2021 00:17:17 UTC