[csswg-drafts] [web-animations] How/when do the "rangeStart/rangeEnd" attributes the Animation interface get evaluated (#13853)

weinig has just created a new issue for https://github.com/w3c/csswg-drafts:

== [web-animations] How/when do the "rangeStart/rangeEnd" attributes the Animation interface get evaluated ==
How/when do the `<length-percentage>` values that can be passed to the [rangeStart](https://drafts.csswg.org/web-animations-2/#dom-animation-rangestart)/[rangeEnd](https://drafts.csswg.org/web-animations-2/#dom-animation-rangeend) attributes on the Animation interface (or via [KeyframeAnimationOption](https://drafts.csswg.org/web-animations-2/#dom-keyframeanimationoptions-rangestart)) when assigning a DOMString, get resolved.

Specifically, the KeyframeAnimationOption section for `rangeEnd` says "A [DOMString](https://webidl.spec.whatwg.org/#idl-DOMString) value is parsed as an [animation-range-end](https://www.w3.org/TR/scroll-animations-1/#propdef-animation-range-end) value to yield a [TimelineRangeOffset](https://drafts.csswg.org/web-animations-2/#dictdef-timelinerangeoffset)". `animation-range-end` is defined as `[ normal | <length-percentage> | <timeline-range-name> <length-percentage>? ]#`, so, `<length-percentage>` values will have to resolved.

Given all that, how/when should a string like `1em` be resolved? 

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/13853 using your GitHub account


-- 
Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config

Received on Tuesday, 28 April 2026 19:15:06 UTC