RE: [OpenType] Proposal: Ligatures w/ ZWJ in OpenType

Date: Fri Jul 19 2002 - 10:25:23 EDT

On 07/18/2002 07:31:52 PM asmusf wrote:

>>Let's forget for a moment whether we're interested in ZWJ or ZWNJ. What
>you recommend to be the default behaviour with German text in the context
>of software that has no particular knowledge of German typography and a
>user that doesn't know to enter any control characters? ...

>**> Having 'elegant' typography that is incorrect is not 'elegant' it is

In other words, in a situation where a user doesn't take any steps to
control ligation and the application doesn't have particular knowledge of
German typography, you'd prefer to see no standard ligatures used for
German text.

In that case, it seems to me that the best way to implement that behaviour
(given current OT specs) is:

- have German-specific lookups in a OT font

- in the German tables, do not apply any of the standard ligatures by
default -- i.e. no liga lookups (the documentation on this feature says
that apps should have this on by default, regardless of language -- see

- in the German tables, include lookups the standard Latin ligatures (ff,
etc.) under the dlig feature

- in the German tables, still include lookups under the dlig feature (or,
per John's proposal, an rlig feature) that allow for ZWJ, even though these
should never be needed for German (include them in case they do occur).

Then, if a user wants ligatures, they activate them using the dlig feature,
and then add ZWNJ to block those that are undesireable (or the application
automates this for them).

What isn't handled well in this scheme is to distinguish the common Latin
ligatures -- ff, fi etc. -- from those that are less common -- ct, st, etc.
The problem here is that the German user wanting standard liguatures would
be applying the dlig feature globally to their text, which isn't how use of
the dlig feature was envisioned.

I see two ways to deal with that:

1) Change the spec with regard to the liga feature (the "UI Suggestion"
section) to say that this feature should be active by default, except in
the case of German. The problem with this is that the list of writing
systems for which this may be needed might not be limited to German, and is
not yet known. This results in a maintenance problem for the spec.

2) Register another feature, slig (say), that can be used for cases like
German where the standard ligatures are not handled by the liga feature
(which would remain on by default for all languages), so that there's a way
to active standard ligatures globally without at the same time activated
less common ligatures.

- 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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