Re: [csswg-drafts] [scroll-animations-1] Define how the `source` member of a `ScrollTimeline` corresponding to a `scroll()` timeline is updated (#8204)

The CSS Working Group just discussed ``[scroll-animations-1] Define how the `source` member of a `ScrollTimeline` corresponding to a `scroll()` timeline is updated``, and agreed to the following:

* `RESOLVED: Each anonymous scroll timeline is a different object. The source is updated at the same time as the currentTime.`

<details><summary>The full IRC log of that discussion</summary>
&lt;argyle> astearns: next.<br>
&lt;argyle> astearns: this is brians issue, rob<br>
&lt;argyle> astearns: this is brians issue, rob?<br>
&lt;argyle> flackr: so brian pointed out that since we have a programmatic api to access a scroll timeline source, and scroll timelines for that matter, it needs to be well defined when that changes and when it's created<br>
&lt;argyle> flackr: fantasia suggested having the scroll timeline change everytime the thing that would be the source changes, and having it be unique per source<br>
&lt;argyle> flackr: i suggested that we follow the current chrome implementation which is more closely aligned to animation objects, where the element holds a scroll timeline entry and internally it points to<br>
&lt;argyle> flackr: the source and updates that when queried or when generating new times<br>
&lt;argyle> flackr: as we have implemented right now<br>
&lt;argyle> fantasai: i'm not 100% clear on this. question is, if i have multiple references to the same scroll container scroll timeline, does that mean each reference is unique and i wouldnt be able to tell if they reference the same thing unless i reference the source values<br>
&lt;argyle> flackr: correct, have to compare the source.<br>
&lt;argyle> astearns: wolud you have to do to fiddle with the objects before you do the sourece comparison?<br>
&lt;argyle> flackr: depends, if we want to mimmick whats happening in computed style, then querying the source will calculate what would be the updated source<br>
&lt;argyle> flackr: if it's stale<br>
&lt;argyle> flackr: however, it's a bit odd that makes the sourece inconsistent with the time value, which is intentionally stale. kevin correct me there?<br>
&lt;argyle> kekvin ellis: timeline time would only be updated once with the frame. if the source changed, it would update to the next frame<br>
&lt;argyle> flackr: that's a good reason to either revisit the decision or leave the source stale. to be consistent.<br>
&lt;argyle> astearns: to be consistent with the time, only leave source stale until next frame<br>
&lt;argyle> flackr: yes<br>
&lt;argyle> fantasai: i think that makes sense for them to be in sync<br>
&lt;argyle> flackr: agree<br>
&lt;argyle> fantasai: not sure about unique identities per reference, but i just dont know which way makes mroe sense. happy to go with what other people think is the right thing to do<br>
&lt;argyle> flackr: they would be the same if they used a named timeline. but this is anonymous timelines, generated on the fly for that element, and it can change<br>
&lt;argyle> flackr: there'd be a lot of non trivial ocmplexity updating those if we needed them to be identity functions to the scroller. they'd also need idendity functions with all the args. which…<br>
&lt;argyle> flackr: and i think animations have set a precedent that is consistent with my proposal<br>
&lt;argyle> fantasai: ok<br>
&lt;argyle> astearns: other opinions?<br>
&lt;argyle> astearns: i'm fine resolving that the source is computed when you ask for it and it's updated at the same time as other data on the object<br>
&lt;argyle> astearns: any concerns?<br>
&lt;argyle> astearns: objections?<br>
&lt;flackr> Proposed resolution: Each anonymous scroll timeline is a different object. The source is updated at the same time as the currentTime.<br>
&lt;argyle> RESOLVED: Each anonymous scroll timeline is a different object. The source is updated at the same time as the currentTime.<br>
&lt;argyle> astearns: next thing we got…<br>
&lt;argyle> astearns: animation iteration count<br>
</details>


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Received on Wednesday, 1 February 2023 17:36:28 UTC