Re: [csswg-drafts] [scroll-animations-1] View progress contain of a sticky positioned elements on the edges (#8298)

The CSS Working Group just discussed `[scroll-animations-1] View progress contain of a sticky positioned elements on the edges`, and agreed to the following:

* `RESOLVED: ignore transforms when calculating timeline ranges`
* `RESOLVED: the start position for view timeline uses the minimum sticky offset or the offset form the start of the scroll, and the end position uses the max sticky offset`

<details><summary>The full IRC log of that discussion</summary>
&lt;argyle> YehonatanDaniv: when you have a sticky positioned element and this is the subject for the view timeline, it has a top 0 so its effective stack point is both the end of the contained range and the beginning of the exit range<br>
&lt;argyle> YehonatanDaniv: the main issue was around adding the phase of the stickiness to also be included int he contained range, so this would match expectations<br>
&lt;argyle> YehonatanDaniv: later rob had a proposal because more issues were raised on the same issue<br>
&lt;argyle> flackr: so when we were workign out the ranges for all these phases, we rely on the principal box<br>
&lt;argyle> flackr: proposal is that when we try and work out the end of these ranges, we treat sticky elements as if it has it's max sticky offset, the offset that it would get at the end scrollposition<br>
&lt;argyle> flackr: similar for the start value, or the minium sticky offset that it would have at the beginning of scroll<br>
&lt;argyle> flackr: this makes all thephases match the visual expectation of the elements position<br>
&lt;argyle> flackr: which has a related issue that we shouldnt be observing transforms, like other layout primitives<br>
&lt;argyle> fantasai: i think that's a separate topic, lets take them one at a time<br>
&lt;argyle> YehonatanDaniv: also what you wrote, that it's already in the spec, that it was implemented differently<br>
&lt;argyle> flackr: if we dont do this, the proposal for sticky position doesnt work as well because the sticky offset isnt necessarily the same direction as the scroll if you include the transform<br>
&lt;argyle> flackr: then thingd are worse if it includes a transform<br>
&lt;argyle> flackr: should lwe talk about this other thing first?<br>
&lt;argyle> fantasai: want to resolve we ignore transforms then switch back?<br>
&lt;argyle> fantasai: proposed resolution is transforms are ignored when caclculating timeline ranges<br>
&lt;argyle> flackr: major point of frustration, adam and bramus may talk about this as well<br>
&lt;argyle> astearns: it's a frustration that they have to be ignored?<br>
&lt;argyle> flackr: no, that's they're currently not ignored<br>
&lt;argyle> bramus: result now is you get into situations where the entire thing flickers<br>
&lt;argyle> i had to train myself out of this bug<br>
&lt;argyle> flackr: if we could ignore the transform position, it makes devs lives easier. makes sticky position easier to reason about<br>
&lt;argyle> astearns: hearing consensus that we ignore transforms when calculating timeline ranges<br>
&lt;argyle> RESOLVED: ignore transforms when calculating timeline ranges<br>
&lt;argyle> flackr: proposal for this is that the start position for view timeline uses the minimum sticky offset or the offset form the start of the scroll, and the end position uses the max sticky offset<br>
&lt;argyle> astearns: seeing thumbs up, any concerns?<br>
&lt;fantasai> +1<br>
&lt;argyle> RESOLVED: the start position for view timeline uses the minimum sticky offset or the offset form the start of the scroll, and the end position uses the max sticky offset<br>
&lt;fantasai> Not sure how to spec it, but I think I agree with what we should *try* to spec :)<br>
&lt;argyle> astearns: anything else on this issue?<br>
&lt;argyle> YehonatanDaniv: probably better in a separate issue? there were other things<br>
&lt;argyle> astearns: given fantasai's concerns about how to get it specced, let get the spec text then raise issues on that<br>
&lt;argyle> fantasai: it's a matter of, do we have the vocab to talk about this? maybe not, and we need the spec to update to provide that<br>
&lt;argyle> astearns: rob, can you pick something for the remaianing time?<br>
&lt;argyle> astearns: rob, can you pick something for the remaining time?<br>
</details>


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Received on Wednesday, 1 February 2023 17:55:37 UTC