[csswg-drafts] UA stylesheets in CSS specs cause interop issues (#8959)

zcorpan has just created a new issue for https://github.com/w3c/csswg-drafts:

== UA stylesheets in CSS specs cause interop issues ==
> For the record, other UA stylesheets defined include:
> 
> * [CSS Color Adjustment Module](https://drafts.csswg.org/css-color-adjust-1/#forced-color-adjust-prop)
> * [CSS Counter Styles](https://drafts.csswg.org/css-counter-styles/#predefined-counters)
> * [CSS Generated Content for Paged Media](https://drafts.csswg.org/css-gcpm-3/#ua-stylesheet) (informative)
> * [CSS Inline Layout](https://drafts.csswg.org/css-inline-3/#initial-letter-align-defaults)
> * [CSS Lists and Counters](https://drafts.csswg.org/css-lists/#ua-stylesheet) (informative)
> * [CSS Pseudo-Elements](https://drafts.csswg.org/css-pseudo-4/#highlight-ua-styles) (SHOULD)
> * [CSS Ruby Annotation](https://drafts.csswg.org/css-ruby-1/#default-ua-ruby) (informative)
> * [CSS Text](https://drafts.csswg.org/css-text-3/#default-stylesheet) (informative)
> * [CSS Text Decoration](https://drafts.csswg.org/css-text-decor-3/#default-stylesheet) (informative)
> * [CSS Transforms](https://drafts.csswg.org/css-transforms-1/#transform-origin-property) has an "initial used value is 0 0 as if > the user agent style sheet contained"(!!!)
> * [CSS Basic User Interface](https://drafts.csswg.org/css-ui-4/#content-selection)
> * [CSS Writing Modes](https://drafts.csswg.org/css-writing-modes-4/#svg-writing-mode-markup)
> * [CSS 2](https://drafts.csswg.org/css2/#html-stylesheet) (informative)
> * [Media Queries](https://drafts.csswg.org/mediaqueries-5/#inverted)

_Originally posted by @gsnedders in https://github.com/w3c/csswg-drafts/issues/8573#issuecomment-1466259733_

In https://bugzilla.mozilla.org/show_bug.cgi?id=645642 `match-parent` was implemented in Gecko, and per https://bugzilla.mozilla.org/show_bug.cgi?id=645642#c14 the suggested UA stylesheet for `option` was implemented. But it was *not* implemented in WebKit or Chromium.

https://drafts.csswg.org/css-text/#default-stylesheet says 

> This appendix is informative, and is to help UA developers to implement a default stylesheet for HTML, but UA developers are free to ignore or modify as appropriate.

I do not find these optional UA stylesheets helpful at all, and would prefer if the UA stylesheet for HTML was left entirely to the HTML standard to define.

Maybe there are exceptional cases where a new feature isn't ready to be included in HTML's UA stylesheet. If you want to include example UA stylesheets, please say that they must not be implemented in UAs, so that they don't cause further interop issues.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/8959 using your GitHub account


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Received on Tuesday, 13 June 2023 08:30:21 UTC