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

From: Doug Ewell (
Date: Thu Jul 04 2002 - 14:46:41 EDT

John Hudson <tiro at tiro dot com> wrote:

> Documents using ZWJ can only be reliably rendered in particular
> fonts. 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 the whole point of including ZWJ is to make the sequence "as
connected as possible," which implies "and no more so." If you code the
sequence "f ZWJ l" that should tell the renderer to use an fl ligature
*if* one exists in the font, and to just use f l if it doesn't. Some
fonts will be able to display the ligature, others won't. For "p ZWJ q"
every font will just display p q. That's completely consistent with
both the wording and the intent of ligation-by-ZWJ.

There's nothing about using ZWJ to form ligatures that requires every
font to contain all possible ligatures, nor anything that requires the
renderer to switch fonts in mid-word and hunt around for a font that
contains the requested ligature. If it's not there, it's not there.

-Doug Ewell
 Fullerton, California

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