CSSWG resolved on this issue
https://github.com/w3c/csswg-drafts/issues/10982#issuecomment-2898572289
I believe this aligns with option 2 in Yoav's reply.
LGTM1
Thanks,
Vlad
On Wednesday, May 21, 2025 at 3:48:18 AM UTC-4 Rune Lillesveen wrote:
> On Tue, May 20, 2025 at 1:38 PM Yoav Weiss (@Shopify) <
> yoavwe...@chromium.org> wrote:
>
>>
>>
>> On Tue, May 20, 2025 at 1:32 PM Rune Lillesveen <futh...@chromium.org>
>> wrote:
>>
>>> On Tue, May 20, 2025 at 10:47 AM Yoav Weiss (@Shopify) <
>>> yoavwe...@chromium.org> wrote:
>>>
>>>>
>>>>
>>>> On Wed, May 14, 2025 at 6:10 PM Philip Jägenstedt <foo...@chromium.org>
>>>> wrote:
>>>>
>>>>> On Wed, May 14, 2025 at 5:21 PM Rune Lillesveen <futh...@chromium.org>
>>>>> wrote:
>>>>>
>>>>>> On Tue, May 13, 2025 at 9:20 AM Rune Lillesveen <futh...@chromium.org>
>>>>>> wrote:
>>>>>>
>>>>>>> On Tue, May 13, 2025 at 8:34 AM Rune Lillesveen <
>>>>>>> futh...@chromium.org> wrote:
>>>>>>>
>>>>>>>> On Tue, May 13, 2025 at 7:43 AM Domenic Denicola <
>>>>>>>> dome...@chromium.org> wrote:
>>>>>>>>
>>>>>>>>> I'm very slightly worried about the cases which we seem to accept,
>>>>>>>>> but the latest on the CSSWG thread suggests we should disallow.
>>>>>>>>> Namely,
>>>>>>>>> @container and @page. How sure are you that changing those to be
>>>>>>>>> invalid in
>>>>>>>>> the future, to follow the latest CSSWG decisions, will not cause
>>>>>>>>> compat
>>>>>>>>> problems?
>>>>>>>>>
>>>>>>>>
>>>>>>>> For @page, I wouldn't be worried at all. It's unlikely someone will
>>>>>>>> start using the feature and rely on a constant
>>>>>>>> sibling-index()/sibling-count() in @page.
>>>>>>>>
>>>>>>>> For @container, I agree that it's safer to be conservative and wait
>>>>>>>> for the resolution, since for @container there are clear use cases and
>>>>>>>> and a more or less obvious behavior in that context.
>>>>>>>>
>>>>>>>
>>>>>>> Some more details below.
>>>>>>>
>>>>>>> For @container, this is relevant for size queries and style()
>>>>>>> queries.
>>>>>>>
>>>>>>> Size queries are currently always evaluated in an element context,
>>>>>>> although falling back to viewport has been discussed, and container
>>>>>>> units
>>>>>>> fall back to small viewport units. Relative units (like ems below) are
>>>>>>> evaluated against the computed values of the container element:
>>>>>>>
>>>>>>> @container (width > calc(sibling-index() * 50px)) {}
>>>>>>> @container (width > 10em)) {}
>>>>>>>
>>>>>>>
>>>>>>> For style queries, the right hand of the query is evaluated against
>>>>>>> the container element and its computed styles for registered custom
>>>>>>> properties. Note that for non-registered custom properties,
>>>>>>> sibling-index()
>>>>>>> would just be part of the string/tokens without any specific meaning.
>>>>>>>
>>>>>>> I think it would be inconsistent to reference relative units (like
>>>>>>> em below) and resolve custom properties references (like var(--a)
>>>>>>> below),
>>>>>>> but specifically throw away sibling-index() when evaluating the value
>>>>>>> against the registered syntax:
>>>>>>>
>>>>>>> @container style(--registered-length: calc(sibling-index() * 20px))
>>>>>>> {}
>>>>>>> @container style(--registered-length: 10em) {}
>>>>>>> @container style(--registered-length: var(--a)) {}
>>>>>>>
>>>>>>
>>>>>> I'll make my position clearer.
>>>>>>
>>>>>> I think we should ship with support for tree counting functions
>>>>>> in @container because
>>>>>>
>>>>>> 1. @container queries are currently always in a (container) element
>>>>>> context and there are valid use cases
>>>>>> 2. Supporting tree counting functions in @container does not break
>>>>>> with the current spec
>>>>>> 3. I don't think it's likely there will be a resolution that
>>>>>> disallows tree counting functions in @container
>>>>>> 4. In particular, disallowing tree counting functions in style()
>>>>>> queries would be inconsistent with e.g. relative units
>>>>>>
>>>>>
>>>>> I am recused on this one, but FWIW I agree with this reasoning.
>>>>> https://github.com/w3c/csswg-drafts/issues/10982 is already Agenda+
>>>>>
>>>>
>>>> When is the discussion scheduled to take place?
>>>>
>>>
>>> I added Agenda+ in March, but haven't pushed hard. Asked the chairs to
>>> put it on the agenda now.
>>>
>>>
>>>> and if we're confident the right solution is to match how relative
>>>>> units, then we can proceed. Rune pointed out that it's already tested
>>>>> here:
>>>>>
>>>>> https://wpt.fyi/results/css/css-values/tree-counting/sibling-function-container-query.html
>>>>>
>>>>> To ship without this behavior only to add it a few milestones later
>>>>> would complicate the browser support story and require explanation on
>>>>> places like MDN and caniuse.com.
>>>>>
>>>>
>>>> In case the CSSWG decision is made before 138 ships to stable and it
>>>> does not align with what you're proposing we ship, are you OK with
>>>> disabling the feature using its Finch flag? Or should we put @container
>>>> support behind a separate flag?
>>>>
>>>
>>> Adding a separate flag for @container here:
>>>
>>> https://chromium-review.googlesource.com/c/chromium/src/+/6563296
>>>
>>> I'm fine with shipping support in @container later in a separate intent,
>>> when the issue is resolved, too.
>>>
>>
>> I think we have two options:
>> 1. Ship @container separately, incurring the costs Philip mentioned
>> (complex support grids, wonky feature detection (do we have a proper story
>> for that?), etc)
>> 2. Optimistically ship everything and hope that the resolution would
>> match what we're trying to ship. In case it won't, we reverse course.
>>
>> I prefer (2), and depending on the answer to my feature detection
>> question, it might be better to keep a single flag and ensure the feature
>> either ships or doesn't in its entirety.
>>
>> WDYT? Does (2) seem like a reasonable risk to take?
>> It does assume that the discussion will happen before 138 hits stable
>> though..
>>
>
> Yes. The issue is now also the second item on the agenda for the CSSWG
> call tonight, so we'd hopefully have a resolution one way or the other.
>
> --
> Rune Lillesveen
>
>
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