Re: ZWJ and Latin Ligatures

Date: Wed Jul 17 2002 - 11:43:30 EDT

On 07/02/2002 10:41:24 AM "John H. Jenkins" wrote:

[I've been out of the loop for the past couple of weeks -- just now
catching up on this.]

>Alas, but that's technically impossible. Both OT and AAT (I'm not sure
>about Graphite) require that single characters map to single glyphs, which
>are then processed. (In OT, of course, you are also supposed to do some
>preprocessing in character space, but that doesn't solve this problem.)
>It would be nice to have a cmap format which maps multiple characters to
>single glyphs initially.
>The way we deal with this is to have the ligatures with the ZWJ inserted
>as part of a ligature table which is on by default and which isn't
>revealed to the UI so that the user can't turn them off.

In Graphite, character sequences get mapped into glyph sequences one-to-one
via the cmap, just as in OT and AAT. From that point, what happens and what
can happen is completely at the discretion of the font developer. They can
decide to always form certain ligatures, always form some ligatures but
make others dependent upon ZWJ, or they may make some/all dependent upon a
user-selected font feature (assumes the software exposes an UI for
selecting the features that the font supports). Of course, nothing happens
unless the font developer included rules that make it happen.

- Peter

Peter Constable

Non-Roman Script Initiative, SIL International
7500 W. Camp Wisdom Rd., Dallas, TX 75236, USA
Tel: +1 972 708 7485
E-mail: <>

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