Re: font features in CSS

Hello Adam,

[cc to IETF LTRU WG]

On 2009/10/30 16:12, Adam Twardoch (List) wrote:

> All OpenType Layout features are assigned in a context of specific
> script and language system. While the assignment of script is easy (the
> engine can determine from the Unicode string which script a certain
> character belongs to, and from there it can pick the appropriate
> OpenType script branch to apply the features for), the language system
> is trickier.
> As you can see from
> OpenType uses a list of language systems that do not have a 1:1
> correspondence with any of the ISO 639 standards. In OpenType 1.6 (at
> the link above), an informational mapping of OpenType language system
> tags and "best matches" in the ISO 639 standards has been provided. It
> is quite obvious that a web browser that applies OpenType Layout
> features should observe the HTML "lang" attribute and, if present, apply
> the appropriate features from the particular language system branch in a
> font (and only if absent, apply the features from the Default language
> system within a script branch). But it might be worth considering to add
> a low-level CSS access mechanism to allow users to choose a specific
> OpenType language system, because some ISO 639 codes can map to several
> OpenType language systems, e.g.
>                          (OT)    (ISO)
> Chinese Hong Kong   ZHH   zho
> Chinese Phonetic  ZHP  zho
> Chinese Simplified  ZHS  zho
> Chinese Traditional  ZHT  zho

HTML lang and XML xml:lang use BCP 47 (, 
formerly RFC 1766/3066/4646) tags, not ISO 639 directly. BCP 47 uses 
two-letter codes (i.e. 'zh') and not three-letter codes (i.e. 'zho') 
when two-letter codes are available. Also, BCP 47 has facilities for 
indicating Region (country,...) with two-letter codes and for indicating 
script with four-letter codes. So the above list should be changed to:

                         (OT)    (BCP 47)
Chinese Hong Kong   ZHH   zh-HK
Chinese Phonetic  ZHP  **
Chinese Simplified  ZHS  zh-Hans
Chinese Traditional  ZHT  zh-Hant

** not sure what's meant by Chinese Phonetic, may be zh-Latn (Latin 
transcription) or zh-Bopo (Bopomofo)?

Regards,   Martin.

#-# Martin J. Dürst, Professor, Aoyama Gakuin University

Received on Friday, 30 October 2009 09:30:12 UTC