[css-highlight-api] Need clarification on expected default values for style properties

[ffiori]

I didn't find any statement on default values for style properties of ::highlight in the spec draft. There are some default values in the spec for pseudos but ::highlight is not in the list. Also in the spec draft of ::highlight there's no mention of it.

Should it use no visual effects or should it use for example Highlight/HighlightText colors instead? I assume it's taking no visual effects as default values (as in when background-color is not specified inside a ::highlight(foo) then the content's background is the same as if there was no ::highlight defined), but maybe it should be explicitly stated?

[sanketj]

Since ::highlight targets author-defined highlights rather than UA-defined highlights, I don't think UAs should define any styles for ::highlight in their default stylesheets. It's also actually not possible to do this since ::highlight requires a highlight name to be passed and there's no way to write a rule that targets all ::highlight pseudos.

The default styles should just be inherited from the originating element. I do agree that we should mention this explicitly in the spec though.

[css-meeting-bot]

The CSS Working Group just discussed highlights and default values for styles, and agreed to the following:

• RESOLVED: UA does not add any default styles to custom highlights

The full IRC log of that discussion

<fantasai> Topic: highlights and default values for styles
<Rossen_> ack emilio
<fantasai> github: https://github.com//issues/6417
<fantasai> github: https://github.com//issues/6375
<fantasai> dandclark: CSS Pseudo specifies default values for certain native highlights. Should there be any defaults for custom highlights?
<fantasai> dandclark: Since these are author-defined highlight, don't think should define any styles in UA styles
<fantasai> dandclark: also no way to do this
<fantasai> dandclark: Seems better to let it just inherit from originating element
<fantasai> dandclark: Might want to make explicit that UA should not give default styles
<sanketj> s/dandclark/sanketj
<TabAtkins> fantasai: I agree with this
<fantasai> s/dandclark/sanketj
<fantasai> s/dandclark/sanketj
<fantasai> s/dandclark/sanketj
<fantasai> fantasai: Doesn't make any sense for UA to add default styles to custom highlights
<fantasai> Rossen_: Any objections?
<fantasai> RESOLVED: UA does not add any default styles to custom highlights

[sanketj]

This issue requires an update to the spec, which is still pending. Leaving this open till that has landed.