[css-contain] it should be clearer that size containment inhibits effects of contents on intrinsic sizes

[dbaron]

The definition of size containment says:

1. When calculating the size of the containing box, it must be treated as having no contents.

I think the implication here (given the text about replaced elements following this) is that "calculating the size of the containing box" includes both:

• finding the resolved values of width and height
• computing intrinsic sizes

However, I think a literal reading of the sentence implies that it means only the first and not the second. I think it should be clearer that the computation of the intrinsic sizes of the box must also be done as though the box has no contents. It's possible it might also be worth mentioning automatic sizes.

[frivoal]

This is indeed intended to cover both layout sizing and intrinsic sizing. Happy to clarify.

How's this?

When calculating the size of the containing box, including when computing its [=intrinsic size=], it must be treated as having no contents.

Also,

It's possible it might also be worth mentioning automatic sizes.

Not obvious to me that it would help. What would you do with that?

As this is a clarification rather than a contradiction or an addition, I think fixing it in level 2 is enough. I have no issue with including the fix in L1's ED, but I don't think it warrants going through the motions of republishing a REC just for this.

[frivoal]

(also are you aware of any bug triggered by this ambiguity, either in browsers or in tests?)

[dbaron]

That proposal seems reasonable. I ran into it while writing up a proposal about the size containment needed for container queries.

[css-meeting-bot]

The CSS Working Group just discussed css-contain] it should be clearer that size containment inhibits effects of contents on intrinsic sizes, and agreed to the following:

• RESOLVED: Accept propose as phrased in comment from florian

The full IRC log of that discussion

<dael> Topic: css-contain] it should be clearer that size containment inhibits effects of contents on intrinsic sizes
<dael> github: https://github.com//issues/4741
<dael> dbaron: I don't think this is controversial but it seemed to me it should be implied by size containment it doesn't impact intrinsic size in addition to final computed size
<dael> dbaron: Ran into this while writing something that referenced size containment.
<dael> florian: Agree it was the intent. Prop rephrasing in the issue to clarify. dbaron said he was fine.
<dael> florian: [reads original sentence]
<dael> florian: Would insert including when computed as intrinsic size. Suggest we add to L2. Clarification so I'll prob edit into L1 too.
<dael> Rossen_: Proposed resolution?
<dael> florian: Accept propose as phrased in comment
<dael> Rossen_: Obj?
<dael> RESOLVED: Accept propose as phrased in comment from florian
<dael> fantasai: Republish a REC?
<dael> florian: Rather not, not worth process hassle
<dael> florian: Happy to update ED so if we do need to update REC it's folded in
<dael> Rossen_: fantasai do you feel strong to republish?
<dael> fantasai: Not super strong. Want to keep things in sync but this is minor
<dael> fantasai: I do want us...if something doesn't effect sizing it should mean any type of sizing. I don't think clarification is a problem but I think problem if "Size" doesn't mean "instrinsic size"