Re: [csswg-drafts] [css-pseudo] clarify paired-cascading behavior (#6386)

The CSS Working Group just discussed `Paired Cascading of Highlight color/bgcolor`, and agreed to the following:

* `RESOLVED: Author origin rules, and not user-origin rules, trigger paired cascade fallback`

<details><summary>The full IRC log of that discussion</summary>
&lt;fantasai_> Topic: Paired Cascading of Highlight color/bgcolor<br>
&lt;fantasai_> github: https://github.com/w3c/csswg-drafts/issues/6386<br>
&lt;fantasai_> delan: for compat reasons, highlights have a "paired cascade", at least for ::selection (but we decided to apply to all)<br>
&lt;fantasai_> delan: for background-color and color<br>
&lt;fantasai_> delan: if you have some browser default colors for ::selection, e.g. white on blue<br>
&lt;fantasai_> delan: if you then go and set one of those two properties, then both of the defaults get suppressed<br>
&lt;delan> ::selection { background: yellow; }<br>
&lt;fantasai_> delan: defaulting to their initial value<br>
&lt;fantasai_> delan: e.g. if you set selection's background to yellow, then the default foreground color at used value time is no longer going to be white<br>
&lt;fantasai_> delan: This issue was pretty big, I asked 7 questions about it in the issue<br>
&lt;fantasai_> delan: pretty much none of the questions have disagreement in the issue<br>
&lt;fantasai_> delan: the main open question is, which origins should this apply to?<br>
&lt;fantasai_> delan: Original spec text says that when author sets one of these two properties, then we suppress highlight color<br>
&lt;fantasai_> delan: but there's also animation and transition origins, and also user orgin<br>
&lt;fantasai_> delan: will talk about aimation and transition first<br>
&lt;fantasai_> delan: I think it doesn't matter whether animation or transition is included in this rule or not<br>
&lt;fantasai_> delan: we used to think it mattered for consistency with 'appearance', but I realized it doesn't matter because the animation and transition properties are not applicable for highlights<br>
&lt;fantasai_> delan: so as far as I'm aware, can't use them in highlights<br>
&lt;fantasai_> emilio: I think ?? you should be able to<br>
&lt;fantasai_> emilio: don't know if propertly supported, though<br>
&lt;fantasai_> dholbert: can a property that is inherited be animated or transitioned?<br>
&lt;fantasai_> delan: Wondering if it is allowed by the spec right now<br>
&lt;fantasai_> delan: if not allowed, then doesn't matter whether those origins included in this rule<br>
&lt;fantasai_> delan: at least until they become allowed<br>
&lt;fantasai_> florian: I believe delan is right, not part of the list of allowed properties<br>
&lt;fantasai_> delan: no way for some way for them to sneak in, despite being applicable properties?<br>
&lt;fantasai_> florian: I don't think we designed one<br>
&lt;delan> s/being/not being/<br>
&lt;fantasai_> dholbert: if animate color of parent, and it inherits through?<br>
&lt;dholbert> s/dholbert/emilio/<br>
&lt;fantasai_> fantasai_: That wouldn't be in the animation or transition origin on the highlight itself<br>
&lt;fantasai_> delan: if not possible to come into highlight overlay, and it doesn't matter<br>
&lt;fantasai_> florian: I think we should talk some other day whether they should, but until they do...<br>
&lt;fantasai_> delan: For the user origin, I did some playing around with user style sheets<br>
&lt;fantasai_> delan: afaict, the question here about user origin and paired cascade comes down to<br>
&lt;fantasai_> delan: if the user sets one of the two properties (bg color or color) in their user style sheet<br>
&lt;fantasai_> delan: do we want that to suppress the UA default for the other property or do we want it to not suppress it and leave the other property as UA-default<br>
&lt;fantasai_> florian: Can implementations guide us? This rule was just for compat<br>
&lt;fantasai_> emilio: I don't think there's any compat requirements on user origin<br>
&lt;fantasai_> emilio: User origins don't disable appearance, so let's follow that precedent<br>
&lt;fantasai_> fantasai_: My reading is that we really don't care, so we should do whatever is easiest<br>
&lt;fantasai_> delan: works out<br>
&lt;fantasai_> delan: even if you go with compat angle, it doesn't suppress default UA colors in Firefox<br>
&lt;fantasai_> Rossen: other opinions?<br>
&lt;fantasai_> RESOLVED: Author origin rules, and not user-origin rules, trigger paired cascade fallback<br>
&lt;fantasai_> delan: In the issue, we all agree on the other 7 questions<br>
&lt;fantasai_> delan: do we need resolutions?<br>
&lt;fantasai_> fantasai_: IIRC they're minor enough that I'd close them under Editor Discretion<br>
</details>


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Received on Wednesday, 15 December 2021 18:25:26 UTC