From: John Hudson (john@tiro.ca)
Date: Thu Aug 31 2006 - 00:03:25 CDT
Philippe Verdy wrote:
> Where do we have a reference in OpenType to describe correctly the correct shaping behavior for various languages using the Arabic script? It looks like U+06BE was not covered in these specs, so this may explain why it was forgotten; and anyway, there's certainly a lack of agreement and specification for any other language than Arabic.
>
> All this suggests that the OpenType working group should really work on this script and start immediately a survey about the effective coverage of all languages using that script. It is clear from those discussions, that only the Arabic language has been seriously considered, and I fear that we learn that other issues are still not detected, even for languages that we know are (or were) written with the Arabic script (and there are many...).
There is no 'OpenType working group' responsible for such things. The OpenType font format
is becoming part of the MPEG standard, which I presume involves some kind of working
group, but that is specifically the font file format (itself an extension of the TrueType
sfnt format), and it should be noted that OpenType *Layout* is an optional aspect of
OpenType (all the OTL tables are desgination optional; a conformant OT font might not have
any OTL tables at all). There is no body responsible for researching and specifying
language-specific font behaviour. Microsoft specify how to build fonts to work with their
shaping engines, but only occasionally make recommendations about specific language
shaping. For the most part, us font developers have been left to figure it out ourselves.
We use a variety of channels to share information, including the OpenType discussion list,
Typohile forums, ATypI conferences and other font technology events. And of course those
of us most involved with non-Latin type design tend to be active in Unicode circles or at
least to keep ourselves informed. Many of us also have particular language users as
clients or advisors. The majority of Arabic script fonts have relatively limited language
support, usually either Arabic language only (common for fonts originating in the Middle
East) or based on Arabic 8-bit codepages (e.g. Arabic, Persian and Urdu). The number of
extended Arabic fonts is actually quite small. The last one I worked on (Adobe Arabic) has
OTL language system tags and distinct glyph shaping and or localised preferred forms for
Arabic, Persian, Malay (Jawi), Morrocan Arabic, Sindhi, Urdu and Uighur. The 'default'
shaping tries to provide the best general coverage, i.e. it is not identical to Arabic
language shaping (which includes some specialised ligatures and contextual variation in
the isolated form of U+0647). I'm happy to recommend to my clients support for additional
language shaping, if I have reliable information. It should be noted though that there are
no currently shipping applications that support language-specific OpenType Layout. It
should also be noted that there is not a one-to-one mapping between OTL 'language system'
tags and language tagging systems and standards; 'language system' is a misnomer, and the
OTL tags should have been called something like 'writing system' or 'typographic
convention', which only sometimes is neatly aligned to a language (it could be aligned to
regional or national preferences, variant orthographies (e.g. traditional vs reformed
Malayalam), or even conventions employed by individual publishers (e.g. variant
conventions for typesetting classical Greek)).
That is the state of play.
John Hudson
-- Tiro Typeworks www.tiro.com Vancouver, BC john@tiro.ca I am not yet so lost in lexicography, as to forget that words are the daughters of earth, and that things are the sons of heaven. - Samuel Johnson
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