At 19:53 +0300 2002-07-04, John Hudson wrote:
>Well, we need and have (in OpenType and AAT) a general purpose
>mechanism for typesetting texts employing ligatures as deemed fit by
>the professional typographer. The expectation of such a mechanism is
>that layout is applied to 'normal' text to render that text
>according to the norms of particular typographic traditions,
>publishing house styles, etc.. It should not be necessary to edit
>the text, inserting ZWJ all over the place, in order to achieve this
It *is* necessary for some ligatures in some scripts. Let's say that
there is in the entire corpus of Ogham three ligatures of RUIS RUIS.
We don't want to encode that as a separate character, and we don't
want it to be on by default since there could be numerous other
examples of RUIS side-by-side with RUIS. But a disgustingly complete
font could take the ZWJ into account for the ligature, which could be
used by people wanting to typeset the non-standard but extant
ligature. ZWJ forces unusual ligatures if the font supports them, and
ZWNJ breaks them where not.
>There are, however, kinds of documents in which the presence or
>absence of ligatures is best determined by the author of the
>document, and for that reason the ZWJ provides a means for the
>author to specify ligation in plain text.
As I have said.
>But it seems to me that such documents are the exception rather than the norm
This is certainly true. That's why ZWJ should not be preferred for
non-exceptional kinds of ligation. But some scripts like Hungarian
Runic and Germanic Runic have a fairly large set which are used from
time to time and irregularly.
>(a particular set of ligatures involving the lowercase f have been a
>normative aspect of European typography for more than 500 years; in
>my profession they are not considered optional or discretionary in
>the setting of running text at typical sizes).
Except for Turkish and Azerbaijani of course. :-)
>Documents using ZWJ can only be reliably rendered in particular fonts.
Well, the same holds true for all ligatures.
>For example, there is no reason why I should not include the
>sequence 'p ZWJ q' in a document, but unless I have a font
>containing a pq ligature I will not be able to render the sequence
>as intended by the author.
But if you were changing the font, it would be available for those
fonts which had it, and ignored for those fonts which didn't.
-- Michael Everson *** Everson Typography *** http://www.evertype.com
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