[css-2025][css-pseudo-4] Add `::marker` to Safe to Release Exceptions

[SebastianZ]

In the discussion about adding typographic pseudo-elements to the Safe to Release Exceptions, @fantasai asked for the ::marker element to be added to the Safe to Release Exceptions, as well. (This was not minuted, though.)
As ::marker wasn't part of that issue, here's a new one, so we can discuss it separately.

So here are the facts and stats regarding this pseudo-element:

• implemented in all major browsers since 2020, though limited support for properties
• WPT pseudo + lists: passing tests: Chrome: 348, Edge: 348, Firefox: 280, Safari: 297; interop pseudo + lists: 233 / 357 (65.2%)
• Open issues: on GitHub pseudo + lists: ~9, in spec.: 2

Sebastian

[Loirooriol]

implemented in all major browsers since 2020

WebKit doesn't support content nor a bunch of properties that are supposed to work: https://bugs.webkit.org/show_bug.cgi?id=204163

Also the wpt link is wrong, tests are in:

• https://wpt.fyi/results/css/css-pseudo?q=marker
• https://wpt.fyi/results/css/css-lists?q=marker

Also see some open issues against css-lists (not all are about the pseudo-element):

• https://github.com/w3c/csswg-drafts/issues?q=is%3Aissue%20state%3Aopen%20label%3Acss-lists-3%20%22%3Amarker%22%20in%3Atitle

[SebastianZ]

implemented in all major browsers since 2020

WebKit doesn't support content nor a bunch of properties that are supposed to work: https://bugs.webkit.org/show_bug.cgi?id=204163

Interestingly, according to https://wpt.fyi/results/css/css-pseudo/parsing/marker-supported-properties.html?label=experimental&aligned&q=marker WebKit supports parsing content while Gecko fails a lot of those tests.

Anyway, I already wondered whether I should add a note about that but then thought it's obvious from the WPTs. Though given the numbers don't fully reflect the support, I've now added a short note. Thanks for the hint!

Also the wpt link is wrong, tests are in:

• https://wpt.fyi/results/css/css-pseudo?q=marker

• https://wpt.fyi/results/css/css-lists?q=marker

Copy & paste error. Fixed that and added the list ones.

Also see some open issues against css-lists (not all are about the pseudo-element):

• https://github.com/w3c/csswg-drafts/issues?q=is%3Aissue%20state%3Aopen%20label%3Acss-lists-3%20%22%3Amarker%22%20in%3Atitle

I've added the css-pseudo-4 tag to all that seemed related to the pseudo-element and added the URL to the description and updated the issue count. Again, thanks for the hint!

Sebastian

[Loirooriol]

WebKit supports parsing content

Yeah, I added both parsing tests and behavior tests. I guess they wanted to raise their WPT pass rate so they just enabled parsing without adding any real support for lots of properties, which would require a huge refactoring.

On the other hand, Gecko has real support for all properties, it's just gated by a pref. So they only need to relax it a bit and allow more properties without the pref.