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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