[csswg-drafts] [css-fonts-4] font-language-override tag is not necessarily 3 letters (#5195)

jfkthame has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-fonts-4] font-language-override tag is not necessarily 3 letters ==
The [spec](https://www.w3.org/TR/css-fonts-4/#font-language-override-string-value) says that the value of `font-language-override` is a "single three-letter case-sensitive OpenType language system tag". However, while it's true that most OT langsys tags are three letters, this is not actually a requirement; the [OT spec](https://docs.microsoft.com/en-us/typography/opentype/spec/languagetags) has a few 4-character tags.

(Actually, they're all 4-character, because the ones that look like 3-letter tags are padded with a trailing space.)

The characters involved are not necessarily limited to letters, either. Although the spec says that "[b]y convention, registered language system tags use three or four capital letters", the list has a couple of examples that include a digit 0.


Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/5195 using your GitHub account