[Bug 14709] user agent lang tag handling is insufficiently specified


--- Comment #24 from John Daggett <jdaggett@mozilla.com> 2011-11-09 01:02:41 UTC ---
(In reply to comment #23)
> 'mya' (comment #0) is clearly invalid as a BCP47 language tag. However, AFAICS,
> it would have to be BCP47 which defined what a "legacy language tag" would be.
> But "legacy" is a word that does not occur in BCP47. 
> BCP47 operates with 'Deprecated', and in the Language Subtag registry, there
> appear to be 90 entries which have the 'Deprecated:' field. Since 'mya' does
> not appear in the Language Subtag registry, it has no other status than
> invalid.

The 'mya' language subtag is a registered ISO 639-3 language subtag but
there's an equivalent ISO 639-1 two-letter code, 'my', so the valid
BCP47 form is 'my' and not 'mya'.  I don't think "deprecated" really is
a fitting description, it's simply invalid in the context of a BCP47 tag.

I agree that invalid language subtags should not be mutated in the DOM
but invalid BCP47 language subtags must be interpreted as being
equivalent to null lang subtags.

For background, below is the bug discussion that led me to file this
bug: https://bugzilla.mozilla.org/show_bug.cgi?id=631479#c92

Basically Gecko has several backends for handling fonts, one for
OpenType fonts and another for Graphite fonts under development, and the
language tag format is different between these.  My feeling is that
only valid BCP47 language subtags should be mapped or passed down to
these font backends, invalid tags should treated as if the lang subtag
was not specified.

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Received on Wednesday, 9 November 2011 01:02:54 UTC