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 >result.
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
