[css-text] Reference to HTTP Content-Language header for language declaration

[r12a]

1.3. Languages and Typesetting
https://drafts.csswg.org/css-text-3/#content-language

Note: Authors can tag content using the global lang attribute in HTML, the universal xml:lang attribute in XML, and the HTTP Content-Language header for content served over HTTP.

The i18n WG recommends always using document-internal declarations, even if the appropriate language is contained in the HTTP Content-Language header. Obtaining the language from the HTTP header should only be a last resort fallback, and even then it's problematic. See https://www.w3.org/International/questions/qa-http-and-lang (esp. https://www.w3.org/International/questions/qa-http-and-lang.en#http).

I think, therefore, the note should be reworded so that it doesn't imply that HTTP declarations are of equal validity to the lang attributes. Really it should say something like: authors can use the lang or xml:lang attributes, and some browsers in some cases may be able to extract something useful from the HTTP information if those are lacking. Personally, i'd be inclined to just drop the mention of the HTTP Content-Language completely.

(I was actioned to send this comment by the i18n WG)

[r12a]

fwiw, reasons HTTP language declarations are problematic include:

• they represent metadata rather than language-processing language
• they may have multiple language value arguments, which is not appropriate for applying language for language-processing, and which currently breaks language declarations for browsers
• HTTP declarations don't work unless the resource is served by a server
• it suggests to authors that it may be ok to use the Content-Language meta element, which is deprecated in HTML and doesn't actually work on all browsers

[r12a]

Thank you for this edit. The i18n WG is satisfied with the resolution and has closed its tracker issue.