Re: [csswg-drafts] [scroll-animations-1][css-animations-2] Out-of-range range offsets (#8578)

The CSS Working Group just discussed `[scroll-animations-1][css-animations-2] Out-of-range range offsets`, and agreed to the following:

* `RESOLVED: allow timeline ranges outside of 0-100% range, and use them as-is for existing animation start-time and duration calculations.`

<details><summary>The full IRC log of that discussion</summary>
&lt;TabAtkins> flackr: This is about whether we allow animation-range offsets outside the 0-100% range, and if so what we do with them<br>
&lt;TabAtkins> flackr: I propose we do allow them, and we have the animation-range account for that range (so the animation conceptually begins before the timeline start). This is already well-defined.<br>
&lt;TabAtkins> flackr: Also fairly consistent with the way we allow keyframe offsets outside the animation active interval.<br>
&lt;TabAtkins> (Also consistent with gradients.)<br>
&lt;TabAtkins> flackr: I think it's also useful to have negative values so you can define an animation portion as starting before some other range.<br>
&lt;TabAtkins> +1<br>
&lt;ydaniv> q+<br>
&lt;miriam> ack ydaniv<br>
&lt;TabAtkins> ydaniv: Is there weirdness with non-named ranges, having values outside the range?<br>
&lt;TabAtkins> flackr: Why is that weird<br>
&lt;TabAtkins> ydaniv: With named ranges you may still have more scroll range<br>
&lt;TabAtkins> ydaniv: when you use the entire scroll range there's nothing outside of 0-100<br>
&lt;TabAtkins> flackr: That's not true with view timelines, because their complete range is "cover" but they do produce values outside of 0-100<br>
&lt;TabAtkins> flackr: But even so, having implicit clipping at the scroll limit is alreayd part of the API in terms of how keyframes work, and how named ranges work if you can't scroll to that full range. So I think it's consistent.<br>
&lt;TabAtkins> miriam: So if the value is outside 0-100 and there's no way to get to there, it's clipped?<br>
&lt;TabAtkins> flackr: It's implicitly clipped - if you have an animation start at -20%, when the animation actually starts it'll actually have already gone thru 20% of the animation.<br>
&lt;TabAtkins> flackr: Proposed resolution is allow timeline ranges outside of 0-100% range, and use them as-is for existing animation start-time and duration calculations.<br>
&lt;TabAtkins> miriam: Objections?<br>
&lt;TabAtkins> RESOLVED: allow timeline ranges outside of 0-100% range, and use them as-is for existing animation start-time and duration calculations.<br>
</details>


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Received on Wednesday, 17 May 2023 16:35:10 UTC