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Re: [css-fonts] font-language-override property and descriptor

From: John Hudson <john@tiro.ca>
Date: Fri, 3 Feb 2017 16:52:53 -0800
To: fantasai <fantasai.lists@inkedblade.net>, Jonathan Kew <jfkthame@gmail.com>, www-style@w3.org
Message-ID: <7cb6af15-a08d-7aab-adc6-b70367994838@tiro.ca>
On 03/02/17 16:07, fantasai wrote:
> I'd like to check with John Daggett on this point... in the meantime,
> what's the use case for having one font use one language value and a
> different font use a different one--is that ever a thing that happens? 

The first use case is OpenType fonts with different Language System 
coverage, one of which might be suitable for the document language 
without that language being included in the font Language System 
coverage. My usual example for this is a document in Macedonian being 
displayed using a font that contains an SRB (Serbian) Language System 
but not an MKD (Macedonian) Language System. This is not unusual, as 
font developers at the time such a font is made might only have reliable 
information about specific language typographic norms, e.g. Serbian, and 
not be aware that the same norms are suitable for Macedonian.

The second use case arises from the fact that an OpenType Language 
System tag is not, in fact, a natural language tag directly analogous to 
a document language tag. An OT Language System tag in combination with 
an OT Script tag, indicates a particular typographic form of a writing 
system. In some cases, this can be mapped directly to a document 
language tag, in some cases it might be better mapped to a locale, and 
some registered Language System tags indicate notation systems that are 
not specific to any individual language. So, the two phonetic notation 
system tags for IPA and Americanist transcription — IPPH and APPH, 
respectively — will be essential for enabling appropriate phonetic forms 
of some Greek letters that in a font may differ from the default Greek 
alphabet style. This is only possible if authors are able to directly 
specify the appropriate OT Language System tags independently of 
document language tagging.

There is third use case, but it is very peculiar, and I don't think I've 
actually seen a font built in this way: it is possible that a 
combination of OT Script and Language System tags can be used to 
identify a typographic convention for a script that is particular to a 
locale. So, for example, if one examines German and French editions of 
classical Greek texts of the 19th Century, one observes fairly regular 
and differing conventions regarding use of the long and short forms of 
the letter beta (I forget the exact conventions; I recall that one uses 
the long form only at the beginning of a word). These conventions could 
be captured in an OT font, using contextual substitutions under 
particular Language System tags, in such a way that text in Greek 
characters (<grek> Script tag) could be processed according to either 
FRA (French) or DEU (German) Language System. In that case, the Language 
System tag isn't indicating the document language — Greek — at all, but 
rather a convention for Greek typography associated with French or 
German publishing conventions.



John Hudson
Tiro Typeworks Ltd    www.tiro.com
Salish Sea, BC        tiro@tiro.com

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Received on Saturday, 4 February 2017 00:53:29 UTC

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