[css-text-3][CSS2] bidi white space collapsing, with bidi control characters

[frivoal]

CSS2 (and also CSS-TEXT-3) is pretty clear about how control characters should be processed when doing white space collapsing:

For each inline element (including anonymous inline elements), the following steps are performed, treating bidi formatting characters as if they were not there:
...

However, it seems that all browsers agree not to do that:
http://jsbin.com/locakid/edit?html,output

They do it correctly when the bidi situation is caused by markup/properties, but not when it comes from bidi control characters.

This causes web-platform-tests/wpt#5460

We need either to fix the specs or to fix the browsers. Browsers all behaving the same makes me doubt changing this is web compatible, but bidi or i18n experts should chime in about how important this is.

@fantasai, what do you think?

[fantasai]

I doubt there's a Web-compat issue here--if you're collapsing spaces, you expect the spaces collapsed, and as an author you're not particularly aware of bidi characters. That said, I don't consider this an important situation to handle correctly, so it might not be worth asking the browsers to fix it.

[frivoal]

if you're collapsing spaces, you expect the spaces collapsed, and as an author you're not particularly aware of bidi characters.

Right, but the fact that they don't collapse is the bug, so by your logic, that would violate author expectations.

(I do defer to you and i18n folks as to whether this is important)

[css-meeting-bot]

The Working Group just discussed white space collapsing through bidi formatting chars, and agreed to the following resolutions:

• RESOLVED: Keep but mark at risk
• RESOLVED: Just keep, don't mark at risk.

The full IRC log of that discussion

<fantasai> Topic: white space collapsing through bidi formatting chars
<fantasai> https://drafts.csswg.org/css-text-3/issues-lc-2013#issue-172
<dael> github: https://github.com//issues/2233
<dael> fantasai: We asked for i118n feedback. Wanted to check with WG as well. You have some text and at the end of the line you have whitepsace and mixed in there are bidi control characters. Does the whitespace collapse?
<dael> florian: If instead of bidi control characters you have markup with the eq. bidi commands we collapse through.
<dael> myles: Reason to not collapse is if there's a character user can see. This is not that. It should collapse.
<dael> florian: Spec says that but I don't believe anyone does that.
<dael> florian: CSS2 and CSS Text 3 says it must collapse.
<dael> fantasai: Keep spec as is and file bugs?
<dael> myles: THis is a thing we should do.
<dael> koji: WE make bidi controls follow collapsing.
<dael> astearns: Text 3 is where in process?
<dael> fantasai: LC
<dael> astearns: It'll have to be at risk if we still don't have impl.
<dael> fantasai: I'm happy for at risk.
<eae> (to clarify, in our new layout engine we do collapse through bidi control characters. the current layout engine does not)
<dael> fantasai: Mark it as at risk and if no one impl we say we want to do it this way.
<dael> astearns: Close no change?
<dael> florian: Mark at risk?
<dael> RESOLVED: Keep but mark at risk
<dael> fremy: Edge does this
<dael> fantasai: koji says Chrome will.
<dael> RESOLVED: Just keep, don't mark at risk.

[fantasai]

There's already a test for this, it's bidi-003, written by Hixie a long time ago. It's not complete, since it only handles some bidi control characters, but it exists.