What are "CSS character escape sequences"?

[edent]

Re Example 6 https://www.w3.org/TR/2017/WD-webvtt1-20170808/#introduction-other-features

Would it be possible to link the text "CSS character escape sequences" to an explanation?

It took me a while to realise that \31 related to the Unicode code point of 1.

https://github.com/w3c/webvtt/blob/gh-pages/index.bs#L394

[silviapfeiffer]

I think that's a good idea.
BTW: that example was specifically included because WebVTT has visual similarity to SRT and in SRT all the cues are numbered, so if you wanted to reference such cues by CSS, you needed to use the Unicode code point (see https://mathiasbynens.be/notes/css-escapes).

Maybe this is the best place to link to for the explanation: https://www.w3.org/International/questions/qa-escapes

[edent]

I think that's an excellent idea.

A small explanation in the text would also be useful.

For example, does 123 become \3123 or \31 23 or \31\32\33?

[silviapfeiffer]

Quoting from https://mathiasbynens.be/notes/css-escapes : "Basically, to escape any numeric character, just prefix it with \3 and append a space character"

so it would be \3123 ?

[edent]

This is where I get confused. According to https://googlechrome.github.io/samples/css-escape/ - it should be \31 23

So, a few examples in the spec would be helpful.

[silviapfeiffer]

yeah, I'm confused also :-)

[aphillips]

There should be no confusion. If you want to encode "123" it's one of:

\31 \32 \33

Or

\31\32\33 // because \ cannot be a hex digit

Or

\000031\000032\000033

But definitely not:

\3123 // that's ㄣ, a zhuyin/bopomofo character
\31 23 // that's 123, but the 2 and 3 are not escaped: they are just literals

The advice that you can follow \3 with a numeric character only works for the ASCII digits, please note. \3٢ (that's an Arabic script '2') produces garbage.

It's a good idea to have an example like 123 as the label so that you can show one of the valid sequences. It also suggests that the qa-escapes article could use a sequence example.

[silviapfeiffer]

Thanks for clarifying! Easy to add an example - and yes, the qa-escapes article could do with one also. :-)

[dwsinger]

shouldn't we link to the CSS clause and let/ask them do the appropriate examples?

[edent]

I think having a few examples in the document would be helpful. If this is going to confuse people used to SRT files, then the more in-line examples the better.

[zcorpan]

There should be no confusion.

Evidently there is confusion... ^_^

But definitely not:
...
\31 23 // that's 123, but the 2 and 3 are not escaped: they are just literals

\31 23 is actually OK, the whole thing is an ident.

[silviapfeiffer]

Yeah, I confused myself in the end, so agree with @edent to just add another example.

[edent]

Or, is it possible to not use CSS Escaping? Seems like such an obscure requirement.

[silviapfeiffer]

Nope, your stylesheet will not work to style cues without the escaping.

[r12a]

Easy to add an example - and yes, the qa-escapes article could do with one also. :-)

Ok, i did it in the lower part of the section at http://w3c.github.io/i18n-drafts/questions/qa-escapes.en#cssescapes

Please could you take a look, and if you're happy with it, i'll publish to the /International site. Thanks.

[aphillips]

@r12a I think the example is "okay" but confusing because there is something missing from the article, example-wise. I would suggest adding an example of a multi-character escape, e.g. ‘日本語‘　-> \65E5 \672C \8A9E

Otherwise the number (123 -> \31 23) example is confusing.

[r12a]

@aphillips why would you need to do multiple escaping here? Or are you talking about a different use case?

[aphillips]

@r12a You don't need it here. I'm suggesting you need it in the article. In the article you only ever show one character being escaped in a row, with the édition/émotion examples. The above thread represents confusion about how additional characters work. If you only show one-in-a-row, it's less clear how the escapes work.

[zcorpan]

@r12a does the article say that non-ASCII has to be escaped in CSS? It does not. .émotion {...} is allowed.

[zcorpan]

PR: #356

[r12a]

Ok, new text at http://w3c.github.io/i18n-drafts/questions/qa-escapes.en.html#cssescapes including the feedback above. Please review. Thanks.

(I also made additional edits to other parts of the article, including a new quick answer section.)

[zcorpan]

@r12a LGTM.