Re: Proposal: Ligatures w/ ZWJ in OpenType

From: John Hudson (
Date: Mon Jul 15 2002 - 16:41:11 EDT

At 08:58 AM 15-07-02, Doug Ewell wrote:

>No, what bothers me is that the ZWJ/ZWNJ ligation scheme is starting to
>look just like the DOA (deprecated on arrival) Plane 14 language tags.
>In each case, Unicode has created a mechanism to solve a genuine (if
>limited) need, but then told us -- officially or unofficially -- that we
>should not use it, or that it is "reserved for use with special
>protocols" which are never defined or mentioned again.

>ZWJ/ZWNJ for ligation control is part of Unicode. It is not always the
>best solution, but it is *a* solution, and should be available to the
>user without restriction or discouragement.

I don't think I am trying to discourage people from using ZWJ/ZWNJ for
ligation control, or to impose restrictions upon it, but I do have concerns
about the practicalities of implementing such control in a way that
provides users of ZWJ with the results they desire while not breaking
existing ligature implementations. I really am trying to figure out a clear
and consistent way to make ZWJ work. Of course, I can only try to propose
part of the solution, because ZWJ has an impact not only on how fonts are
made but on how layout engines handle the relationship of control
characters and glyphs. The implementation note in TR27 stating that font
developers should add glyph substitution lookups for ZWJ sequences to their
fonts seems to me to display an incomplete understanding of the technology
involved. The comments on 'Ligatures and Latin Typography -- naive
comments, I think: the layout issues involved are in no way limited to
Latin typography -- in TR28, instead of clarifying the situation retreat to
a vaguer position. Perhaps the idea is that, by keeping things vague, the
UTC permits freedom of implementation, but so far all I am seeing in
response is confusion: confusion about what ZWJ signifies in text, and how
it should be implemented in line layout. If Doug is worried that ZWJ will
be 'deprecated on arrival', he might also worry that ZWJ will be so
variously interpreted as to become useless as a reliable means of achieving
any consistent result.

I have other, more general concerns, about the poor communication between
the UTC and the people who make fonts. This is not the UTC's fault. Unlike
other technologies that are related to and influenced by Unicode, e.g. web
standards and technology, there is no parallel organisation governing the
development of font software, no 'Font Technology Consortium'. This means
that communication between UTC and font developers has been, at best, ad
hoc. I am trying to do something to rectify this situation, since I believe
it will benefit everyone if UTC can rely on more regular, consistent and
informed involvement from the type industry, and font developers can
receive and digest information from the UTC that has an impact on font
technology in a timely fashion.

John Hudson

Tiro Typeworks
Vancouver, BC

Language must belong to the Other -- to my linguistic community
as a whole -- before it can belong to me, so that the self comes to its
unique articulation in a medium which is always at some level
indifferent to it. - Terry Eagleton

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