Re: ZWJ and Latin Ligatures (was Re: (long) Re: Chromatic font research)

From: John Hudson (
Date: Thu Jul 04 2002 - 13:06:10 EDT

At 23:08 7/1/2002, Asmus Freytag wrote:

>Remember also that the simplistic model you present already breaks down
>for German, since the same character pair may or may not allow ligation
>depending on the content and meaning of the text - features that in the
>Unicode model are relegated to *plain* text.
>Therefore, I would be much happier if the discussion of the 'standard'
>case wasn't as anglo-centric and allowed more directly for the fact that
>while fonts are in control of what ligatures are provided, layout engines
>may be in control of what and how many optional ligatures to use, the text
>(!) must be in control of where ligatures are mandatory or prohibited.
>I don't know of a case where a mandatory ligature of two characters is
>sometimes prohibited, which means that for all practical cases, mandatory
>ligatures, like LAM-ALIF tend to also be handled by the layout engine. But
>ligature prohibition is a quite regular feature of German orthography and
>any Unicode-based system that intends to provide generic support for Latin
>script use, should be able to support it. As the prohibition is on a
>case-by-case and word-by-word basis, it has to be marked in the text.

The specific requirements of some languages with ligature restrictions,
e.g. Turkish, are supported in the OpenType 'language system' model, which
enables different layout behaviour to be associated with different
orthographic systems. Unfortunately, the German rules really require
dictionary support to be properly implemented, since the rules for
word-internal ligature use/prohibition are intimately linked to spelling
and cannot be algorithmically arrived at.

John Hudson

Tiro Typeworks
Vancouver, BC

Language must belong to the Other -- to my linguistic community
as a whole -- before it can belong to me, so that the self comes to its
unique articulation in a medium which is always at some level
indifferent to it. - Terry Eagleton

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