Re: [csswg-drafts] [css-will-change] Should `will-change: transform` establish a containing block for fixed background attachments? (#11811)

The CSS Working Group just discussed ``[css-will-change] Should `will-change: transform` establish a containing block for fixed background attachments?``, and agreed to the following:

* `RESOLVED: If any non-initial value of a property would cause the element to generate a containing block for fixed background attachments, specifying that property in will-change must cause the element to generate a containing block for fixed background attachments.`

<details><summary>The full IRC log of that discussion</summary>
&lt;noamr> oriol: when you set will-change to the name of another property the element would get all the behaviors related to that specify property. in particular, for transform, the spec says that the element establishes a CB for all descendants (abs, fixed, fixed background attachment)<br>
&lt;noamr> oriol: the first two already apply for the first two. but not for background attachment. in does do this in gecko and blink, and not in webkit<br>
&lt;noamr> oriol: smfr said this is a webkit bug<br>
&lt;noamr> oriol: I think should cover this in will-change<br>
&lt;noamr> oriol: there was a discussion on how to deal with it, e.g. just for transform.<br>
&lt;noamr> emilio: also the individual transform properties<br>
&lt;noamr> astearns: does the general statement in the quote match your expectation?<br>
&lt;noamr> emilio: I think so<br>
&lt;emilio> q+<br>
&lt;astearns> ack emilio<br>
&lt;noamr> fantasai: all values or just CB/SC creating values?<br>
&lt;noamr> TabAtkins: don't create a stacking context there<br>
&lt;TabAtkins> s/don't/do/<br>
&lt;noamr> astearns: sounds like we agree about that comment in the last issue<br>
&lt;noamr> PROPOSED RESOLUTION: If any (*) non-initial value of a property would cause the element to generate a containing block for fixed background attachments, specifying that property in will-change must cause the element to generate a containing block for fixed background attachments.<br>
&lt;noamr> RESOLVED: If any non-initial value of a property would cause the element to generate a containing block for fixed background attachments, specifying that property in will-change must cause the element to generate a containing block for fixed background attachments.<br>
&lt;dholbert> +1 to the ambiguity around "any" there<br>
&lt;noamr> scribe-<br>
</details>


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Received on Friday, 14 November 2025 00:56:15 UTC