With both font technologies, control can be offered to the user. Let's make the
scenarios more specific.
Suppose that the user has a "AAT/OpenType" font that has the ligature glyph for
"ct". If he/she doesn't, then a "ct" ligature will never appear in any of the
following scenarios (scenarii?). Note that the sequence "ct" will be rendered as a
"ct" ligature if the font has that ligature on by default (ON), and just as "ct" if
it is off by default (OFF)
Here are the different cases:
A. The keyboard supports ZWL.
A1. Before typing ZWL:
ON: the user sees "ct" ligature.
OFF: the user sees "ct".
A2. After typing ZWL:
A2a. The font doesn't know about ZWL.
ON&OFF: The user sees "c", <black box>, "t"
A2b. The font at least knows that ZWL is in the range of format characters, and
renders it invisibly.
ON&OFF: The user sees "ct"
A2c. The font supports the triple "c", "ZWL", "t".
ON&OFF: The user sees "ct" ligature.
B. The keyboard supports ZWNL.
B1. Before typing ZWNL:
ON: the user sees "ct" ligature.
OFF: the user sees "ct".
B2. After typing ZWNL:
B2a. The font doesn't know about ZWNL.
ON&OFF: The user sees "c", <black box>, "t"
B2b. The font at least knows that ZWNL is in the range of format characters, and
renders it invisibly.
ON&OFF: The user sees "ct"
C. The GUI supports explicit ligature formation (EON or EOFF).
B1. Before choosing setting
ON: the user sees "ct" ligature.
OFF: the user sees "ct".
B2. After choosing setting
B2a. The font doesn't know about or support setting
ON: the user sees "ct" ligature.
OFF: the user sees "ct".
B2b. The font supports the setting
EON: ON&OFF: The user sees "ct" ligature
EOFF: ON&OFF: The user sees "ct"
In all three scenarios, one can control whether the user sees a "ct" or a "ct"
ligature, if all the appropriate support is there. If all the appropriate support is
not there, they degrade in different ways, as one can see by the different cases.
Lacking complete support, at best, nothing will happen. In some cases, typing a ZWL
will actually break a ligature that would otherwise appear. At worst (with the
format characters), the user will see "c" <black box> "t".
The one further interesting scenario is text interchange:
- When going from rich text (in C) to plain text, one loses the explicit ligature
setting. One does not lose the ZWL/ZWNL characters. The result on the other end of
the interchange depends on the capabilities there, of course. Sending a ZWL or ZWNL
may not achieve the desired result, if the end user just sees a black box.
- In going between different rich-text formats, it depends on the capabilities of
the formats. Looking at the markup world, XSL does support EON/EOFF, while CSS does
not yet.
Mark
John Cowan wrote:
> John Jenkins wrote:
>
> > For me, the AAT and OpenType mechanisms adequately answer this point, as
> > they allow full control over arbitrary (or automatic) ligature generation or
> > overriding.
>
> I begin to suspect that people are talking past one another here. Allow
> full control to whom, using what? AFAIU (and I may not understand far
> enough), OpenType allows control to the font designer, not to the document
> author/transcriber. It is the latter for whom ZWL/ZWNL caters.
>
> > I'm still trying to figure out what I would consider adequate reasons for
> > requiring ligation control in plain text. I haven't seen them proposed yet,
> > however.
>
> In cases where it is incorrect to ligate, though the default says to do
> so; or it is incorrrect not to ligate, though the default says not to.
> A hypothetical example: suppose there are certain words in Arabiform text where
> lam followed by alef must appear, but *without* ligation. How would that be
> represented in Unicode? Because it is a matter of correctness/legibility,
> it is a plain-text distinction.
>
> (There may be no such words, but that doesn't affect my current subpoint.)
>
> --
>
> Schlingt dreifach einen Kreis vom dies! || John Cowan <jcowan@reutershealth.com>
> Schliesst euer Aug vor heiliger Schau, || http://www.reutershealth.com
> Denn er genoss vom Honig-Tau, || http://www.ccil.org/~cowan
> Und trank die Milch vom Paradies. -- Coleridge (tr. Politzer)
This archive was generated by hypermail 2.1.2 : Tue Jul 10 2001 - 17:20:57 EDT