> If software can automatically do something in one place, it
> seems to me that it should also be able to do an equivalent
> thing in another place. I.e. if software can automatically add
> ZWL at appropriate places to create the desired ligature glyphs
> on output, then software should also be able to automatically
> select the desired sequences of character codes (sans ZWL) to
> substitute by ligature glyphs. At least, that seems to make
> sense to me unless there's more to this story than I'm not
> aware of.
> For unpredictable ligatures, it should be possible (i.e. 'it is
> technologically feasible', not 'software ought to be able') to
> apply style information to the relevant run of text enabling a
> feature that causes ligation.
I agree that software could (and should) do a lot concerning ligatures in the
But from my point-of-view there are several arguments against letting the
software do everything (and preventing explicit specification of ligation
behaviour by the author):
1. As I pointed out in my reply to John Jenkins, there are cases where the
software will not be able to determine ligation correctly. (The "Wachstube"
example) In these cases the author MUST explicitly specify ligation. So Unicode
MUST provide means to do so, eather by defining ZWJ or ZWL to be the character
that specifies ligation behaviour in latin scripts. I agree with Micheal Everson
who has claimed the need for such a character.
2. Software can do a lot, but does it do so? I am pretty sure that there does
not exist a single text editor that handles all blackletter ligatures. But even
in the much more common case of roman fonts and the fi, ffi, ffl Ö ligatures:
How many programs actually use ligature shapes to display these character
sequences? And how much money do they cost?
3. With the OpenType or related fonts every font designer can offer ligature
shapes in his fonts. I would like to do so for the (few?) people that like
blackletter fonts. If there was a ZWJ or an official declaration that Unicode
ZWJ and ZWNJ should be used to force or prohibit ligation in latin scripts, then
every writer could use the ligature shapes offerd by the fonts. He would need
only basic software abilities built-in to the operating system and thus also
accessible from small and affordable applications. He would not need to by
Indesign and then see that he gets fi ligatures but doesn't get others like sch,
tz or ft in Fraktur.
4. What about portability and exchangeability of text fragments, if one program
handles ligatures and another does not? Should we forget copy and paste, because
ligation information simply gets lost when pasting from one application to
another? ZWJ ore ZWL would certainly not get lost in this process!
Although my knowledge is limited to the blackletter case which is a historical
one and thus probably has low priority for the experts developing Unicode, I
have learned from the contributions of Micheal Everson and others that the
arguments listed above will apply similarly to other and more common cases.
The discussion which arose from my first mail is still going on. I feel that the
problem of ligatures in the latin script is not yet solved. I think that it
should be solved inside Unicode by defining control characters that explicitly
define ligation behavior. These controls then could be used in conjunction with
OpenType font tables to provide an almost application-independent means of
controlling ligature display. The experts have to decide whether ZWJ and ZWNJ
should be used for this purpose or not, and if there also is a need for a ZWNL
in addition to a ZWL character. Clear statements on what theses characters are
made for in latin script should accompany these decisions.
Maybe, ligation in the arabic and indic scripts has been a problem more urgent
to be solved by Unicode than ligation in the latin script. But now the time has
come to find a solution to the latter, too!
Eberhard Pehlemann, Dorfstraße 7, D-23909 Giesensdorf, Germany, Tel. +49 4541
This archive was generated by hypermail 2.1.2 : Tue Jul 10 2001 - 17:20:57 EDT