Re: [csswg-drafts] [web-animations-2] Prefer phase based start / end delays over converting time based delays (#7749)

The CSS Working Group just discussed `[web-animations-2] Prefer phase based start / end delays over converting time based delays`, and agreed to the following:

* `RESOLVED: Times in a non-time-based timeline are converted to their relative %s.`
* `RESOLVED: Once group effects are added, also add %-based delays/durations.`

<details><summary>The full IRC log of that discussion</summary>
&lt;TabAtkins> flackr: We defined a Web Anim 2 feature for converting time-based to run on non time-based timelines<br>
&lt;TabAtkins> flackr: So they'd "just work", continuing to use %s<br>
&lt;TabAtkins> flackr: Another idea came up to simplify, treating time-based durations and delays as their initial value (as if they're invalid)<br>
&lt;TabAtkins> flackr: This works for simple cases, but concern if you have a time-based group or sequence effect, the delays between effects are very important for relative timing<br>
&lt;TabAtkins> flackr: You couldn't take one of those and switch it to a different timeline if we didn't preserve those delays<br>
&lt;TabAtkins> flackr: So two options, one is continue to convert all times to relative %s when running a time anim on a non-time timeline<br>
&lt;TabAtkins> flackr: This ensures relative timing between effects stays<br>
&lt;TabAtkins> flackr: Other is we use initial values, but allow specifying %-based durations/delays, which let you define the relation of different effects in a non-time-based way<br>
&lt;TabAtkins> flackr: I think first is simpler, and what we already agreed on, but wanted to confirm.<br>
&lt;TabAtkins> TabAtkins: [missed]<br>
&lt;emeyer> TabAtkins: Locking ourselves into non-time-based is a weird syntax; if that’s not the case, fine<br>
&lt;emeyer> s/is/with/<br>
&lt;TabAtkins> flackr: We'll still want to define a % delay for these non-time things, but this wouldn't be required for existing ones<br>
&lt;TabAtkins> flackr: Something raised is it should be possible to take a time-based anim and switch it to a non-time timeline, and have it pick up where it left off<br>
&lt;TabAtkins> flackr: Which #1 will do<br>
&lt;TabAtkins> fantasai: So is proposed resolution that we'll autoconvert time-based delays, and *also* add % delays?<br>
&lt;TabAtkins> flackr: that sounds good to me<br>
&lt;TabAtkins> flackr: Group and sequence effects aren't implemented currently, so I think we should add % delays at some point before/as we implement group/sequences.<br>
&lt;TabAtkins> fantasai: If the main thing you'r eusing the delay for is to create overlapping effects, in a time-based system are you able to specify you anims in a way that's easy and comfortable, given you're combining %s and times<br>
&lt;TabAtkins> fantasai: Feels like that can be a little awkward, two different units<br>
&lt;TabAtkins> flackr: I think the way author would use %s is they'd define a duration for the overall group or sequence, adn the effects within would be %-based<br>
&lt;TabAtkins> flackr: They could mix-and-match but it would get confusing.<br>
&lt;TabAtkins> fantasai: Tangential, do we want to introduce frs as a keyframe offset mechanism? Then you don't have to reshuffle all your %s if you insert some frames.<br>
&lt;TabAtkins> (probably good to bring up as a separate issue)<br>
&lt;TabAtkins> astearns: Should raise separately<br>
&lt;TabAtkins> fantasai: Will do, just wanted to think aobut it in context<br>
&lt;TabAtkins> astearns: Othe ropinions? Rob, can you summarize resolution?<br>
&lt;TabAtkins> flackr: When running an animation with defined times in a non-time-based timeline, we convert those times to their relative %s of the overall effect.<br>
&lt;TabAtkins> +1<br>
&lt;TabAtkins> astearns: Concerns? Objectinos?<br>
&lt;TabAtkins> RESOLVED: Times in a non-time-based timeline are converted to their relative %s.<br>
&lt;TabAtkins> flackr: Should we also resolve to add %-based delays?<br>
&lt;TabAtkins> fantasai: If that's only needed for groups/seqs, we should add it when we do those.<br>
&lt;fantasai> fantasai: but we should resolve now<br>
&lt;TabAtkins> astearns: So proposed resolution is to add % delays once we add group effects?<br>
&lt;TabAtkins> (clearly just use `-duration: 100s`, then 5s == 5%)<br>
&lt;fantasai> fantasai: because having time-based delays that get auto-converted to lengths be the only way to sequence group affects on a scroll animation is just too weird<br>
&lt;TabAtkins> flackr: I'm good with that proposed res<br>
&lt;TabAtkins> astearns: Objections?<br>
&lt;TabAtkins> RESOLVED: Once group effects are added, also add %-based delays/durations.<br>
</details>


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Received on Wednesday, 12 April 2023 16:18:43 UTC