[css-contain] Remove "at-risk" for style containment

[chrishtr]

Right now, the level 2 draft spec says this:

The following features are at-risk, and may be dropped during the CR period:

style containment and the contain: style value

I propose that we drop this text. The reason it exists:

• @emilio was skeptical of the use cases for style containment
• Concerns about interoperability of style containment implementations, and Chromium bugginess in its initial implementation
• Desire to improve the spec for counters (which was one of the main use cases motivating style containment)
• Desire to be able to ship layout and paint containment earlier in Firefox, without getting blocked on the above

Since then:

• There is a new, compelling use case in [css-contain-3] Need style containment for container queries #6213.
• This PR has landed to improve the spec
• Chrome has fixed the known problematic testcases
• Firefox did ship layout and paint containment, and an implementation is in progress in Webkit

Therefore I propose we remove the spec text mentioned above.

[astearns]

I think one thing we should consider is removing contain: style for lack of its own compelling use case and create a new contain: query-target (or some such) as suggested in #6174 that would include the behaviors currently defined for style layout and size

[chrishtr]

for lack of its own compelling use case

I still think containing CSS counters is a compelling use case. Otherwise style recalc won't be contained.

[css-meeting-bot]

The CSS Working Group just discussed [css-contain] Remove "at-risk" for style containment, and agreed to the following:

• RESOLVED: Remove at-risk label for style containment

The full IRC log of that discussion

<dael> Topic: [css-contain] Remove "at-risk" for style containment
<dael> github: https://github.com//issues/6272
<dael> chrishtr: I think there's a use case now which people agree is important. Have improved definition with respect to HTML.
<dael> chrishtr: Spec says HTML ordinals are impl via css counters.
<dael> chrishtr: I think we're in good shape to remove those lines
<dael> florian: I wouldn't be surprised if when another browser impl there's something we overlooked, but don't need label anymore.
<dael> chrishtr: Agreed
<chris> rrsagent, here
<RRSAgent> See https://www.w3.org/2021/05/12-css-irc#T16-19-47
<dael> florian: Have some amount of tests. Want to put it back on track
<dael> astearns: When last discussed I think one impl was against implementing?
<dael> chrishtr: Previously emilio but I think all issues have been addressed
<dael> emilio: I don't object. My concern with style containment is it wasn't clear it was useful and interacted with lists, but since lists are now in terms of counters...still style containment doesn't allow style system optimization but it is needed for use case described
<dael> astearns: Process-wise I would like to see a second impl started. once we put at-risk it's easy to leave until we're sure it's going to happen. I'm not absolutely sure, but it's low risk to take off if we have to put back on
<dael> astearns: Prop: Remove at-risk label for style containment
<dael> RESOLVED: Remove at-risk label for style containment

[frivoal]

closed by f0da302