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..
>
> --
> Rune Lillesveen
>
>
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