[css-lists-3] Should unicode-bidi / direction apply to ::marker?

[fantasai]

CSS Lists 3 currently lists ::marker { unicode-bidi: isolate; } in its UA default rules. This is good, markers should be bidi isolated. However, unicode-bidi isn't listed in css-pseudo-4 as a valid property on ::marker. Options:

• Make unicode-bidi and direction apply to ::marker and keep the UA rule.
• Just make marker's automagically bidi-isolated always.

@MatsPalmgren @emilio thoughts?

[MatsPalmgren]

Fwiw, here's our current UA sheet rule for ::marker.

However, unicode-bidi isn't listed in css-pseudo-4 as a valid property on ::marker.

Please just remove all of the restrictions. It's better if ::marker behaves exactly as ::before/::after in terms of styling/layout. It literally follows the same code path as ::before/::after in Gecko and I see no reason to change that. You could add a note there saying "we may restrict which properties applies to ::marker in the future if it proves impossible to implement in UAs or web compat demands it", if you think it's necessary (I don't).

Caveat: in Gecko, you currently need to use the content property to trigger the new code path. This is a temporary implementation restriction which we intend to fix so that the legacy code path for list-style-type/image synthesize a pseudo content node instead and then use the new path too. (We'll fix this soon hopefully.)

[fantasai]

list-style: outside marker box layout isn't defined, so applying properties like background or border or position or anything else that exposes the exact box dimensions isn't feasible right now. Therefore the whitelist. Happy to add things to the whitelist, but not if they expose things that aren't defined.

[css-meeting-bot]

The CSS Working Group just discussed #3809, and agreed to the following:

• RESOLVED: unicode-bidi / direction apply to ::marker

The full IRC log of that discussion

<dael> Topic: #3809
<dael> Github: https://github.com//issues/3809
<dael> fantasai: We have a limited set of prop that apply to ::market. Unicode bidi direction weren't listed but seems it would be helpful. This is a request to add those to pseudo element spec
<dael> plinss: Objections?
<dael> RESOLVED: unicode-bidi / direction apply to ::marker