Re: [csswg-drafts] [web-animations-2][css-animations-2] How should unspecified trigger range boundaries be resolved? (#11932)

I think that to some extent we are going to have to deviate from `animation-range` regardless: otherwise, `entry x%` expands to `entry x% entry 100%` but I think we've been assuming it expands to `entry x% normal(cover 100%)`.


> > I think that one-sided triggers are a very common and important use case that we should make as easy as possible, and this was explicitly identified as a goal in the original ideation issue [#8942](https://github.com/w3c/csswg-drafts/issues/8942).
> 
> I don't quite agree here. All of the examples [@bramus](https://github.com/bramus) showed above either don't have a trigger, or they were implemented watching scroll positions for legacy reasons.

Hmm, even so I'd have thought we'd agree that the one-sided case is very common and important. 

This seems to come down to personal preference as either choice offers the same functionality so I think putting it to a vote is a reasonable way to resolve the question. Hopefully the issue gets on the agenda this week and we can get a vote. I'll summarize the question: when only one end of the trigger range is specified, e.g. `entry x%` (as opposed to the 2 ends, e.g. `entry x% exit y%`), what should this imply the other end is?

1. `normal` (`cover 100%`), restricting the trigger range to when the element is in view (this is closer to the behavior of `animation-range`).
2.  end of the timeline (`scroll 100%`), making the trigger "one-sided" as the end of the timeline is a boundary that can't be crossed. 

If we decide in favor of option 2, we will probably need a name to indicate this as we would likely want to avoid repurposing `normal`. Based on flackr's [comment](https://github.com/w3c/csswg-drafts/issues/11932#issuecomment-3603914060) above, `infinity` is one option. I would add to that `auto` which would be my preference. `scroll 100%` is another option but might not be a good name for pointer timelines.


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Received on Monday, 8 December 2025 21:56:11 UTC