Re: Proposal: Ligatures w/ ZWJ in OpenType

From: Doug Ewell (
Date: Tue Jul 16 2002 - 11:06:33 EDT

[Note: Please feel free to repost this to the OpenType mailing list. I
removed their address as I am not a member and cannot post there.]

John H. Jenkins <jenkins at apple dot com> wrote:

> The position of the UTC is not that ZWJ should never be used and we're
> sorry we added it, which is the case of the Plane 14 language tags.
> It's that the ZWJ should not be the primary mechanism for providing
> ligature support in many cases. That's as far as it goes.

Good, I'm glad I misconstrued the stronger tone of previous arguments.

>> The UTC may have "intended" that ZWJ ligation be used only in rare
>> and exceptional circumstances, but UAX #27, revised section 13.2
>> doesn't say that.
> The latest word is the Unicode 3.2 document, not the Unicode 3.1
> document. It says:
> Ligatures and Latin Typography (addition)

Oops, I missed that. Obviously one has to read both updates to get the
full picture (no, Ken, I'm not complaining about that).

UAX #28 seems to say that style markup should be used to implement
general ligature policies within a document, and ZWJ/ZWNJ should be used
to implement exceptions to those policies. For example, in Michael
Everson's putative Runic document where only a few combinations are
ligated, or Old Hungarian document where most but not all combinations
are ligated, markup could be used for the general case and ZWJ/ZWNJ
could be used for the exceptions. As long as the markup can specify
ligation to a fine-enough degree, that's perfectly OK.

> The goal is to make the ZWJ mechanism available to people who feel it
> is appropriate to meet their needs, but to try to inform them that in
> the majority of cases, a higher-level protocol would be better.
> Adobe doesn't have to revise InDesign, for example, to insert ZWJ all
> over when a user selects text and turns optional ligatures on.

I never suggested that tools should be *required* to use ZWJ/ZWNJ to
implement ligation, although that would be one way of doing it. It
would have the disadvantage, for instance, that if a user inserted a ZWJ
manually, then turned global ligation on and then off, the manually
entered ZWJ would disappear.

This has been part of the problem in discussing ligation by ZWJ vs.
markup: the perception that it must be either one or the other. Let
users choose whichever mechanism is most suitable for them. UAX #28
implies that markup is better in some cases, and that's fine. I'm just
saying that ZWJ is another way of creating ligatures, and it should not
be artificially constrained to "stylistic" (as opposed to "orthographic"
or "grammatical") ligation, or have any other similar restrictions.

If we wanted to be ridiculously hard-nosed about plain text vs. markup,
we could say that CR/LF should not be used in HTML, because there are
always the <p> and <br> tags that do a better job of controlling line
and paragraph separation. We would never say this, of course. The
"line" between plain text and markup is sort of a shoreline; you can
never say with 100% certainty where the water ends and the land begins.

> OTOH, the hope is that if ligatures are available InDesign will honor
> the ZWJ marked ones, even if ligation has been turned off.


> It's discouraged when it's inappropriate. It isn't deprecated.
> There are numerous places where Unicode provides multiple ways of
> representing something. In this instance, Unicode is trying to
> delineate where a particular mechanism is appropriate and where
> inappropriate.

I still think words like "suggested" and "preferable" are better suited
to this issue than "discouraged" and "inappropriate."

-Doug Ewell
 Fullerton, California

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