From: Mark Davis (mark.davis@jtcsv.com)
Date: Thu Dec 05 2002 - 16:33:23 EST
> with MS people (and not only me, but also Pothana's designer), MS answered
> that the Unicode standard seemed to imply that these accents apply to
> Devanagari script only.
That is incorrect; all non-spacing marks should inherit the script of their
base character. We need to make this clear in
http://www.unicode.org/unicode/reports/tr24/ for Unicode 4.0
Mark
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----- Original Message -----
From: "Antoine LECA" <Antoine10646@leca-marti.org>
To: <unicode@unicode.org>
Sent: Thursday, December 05, 2002 11:13
Subject: Re: Script of U+0951 .. U+0954
> Peter Constable wrote:
> >
> > There is a potential concern in Uniscribe/OpenType: substitution and
> > positioning rules in OT are organised hierarchically by script then by
> > individual writing system / typographic groups (the label used is
> > languages, but the intent is really groups of writing systems that share
> > common typographic behaviours). Thus, a rule that handles positioning of
a
> > glyph for 0950 (or whatever) relative to some member of some class of
> > glyphs must be entered somewhere under some particular script. Now,
there
> > is nothing that prohibits a font developer from creating multiple
> > positioning rules for 0950 with different classes of base glyphs and to
> > have a different one placed in the hierarchy under several different
> > scripts.
>
> Fully agreed so far.
>
>
> > But there may yet be an issue on the Uniscribe side: given a
> > string of characters, which it will begin by mapping into a string of
> > initial glyphs, it has to decide which script tag(s) to apply to
portions
> > of the string. What I don't know is whether it generally assumes
combining
> > marks belong to a specific script, or whether it allows combining marks
to
> > inherit their script from the base characters with which they combine.
>
> Look: in current Uniscribe, leading ZWJ and ZWNJ are discarded (i.e., with
> input U+200B U+093E, you still get the circle meaning "incorrect
combining",
> even if this is perfectly correct Unicode as far as I understand.
> So clearly, they have a problem with "backtracking" when the script is
> not determined by the first character in stream. I can understand that.
> OTOH, when ZWJ or ZWNJ come second or later in conjuncts, they are
properly
> handled. In every script it is relevant. What I would like to see, is that
> the Indic accents be handled in the same way. And when I spoke about that
> with MS people (and not only me, but also Pothana's designer), MS answered
> that the Unicode standard seemed to imply that these accents apply to
> Devanagari script only.
> It looks like to me taht this Scripts.txt just confirm the MS point of
view.
> If this is as intended, that is fine, but that means that a bunch of new
> character (with few or no added value) are to be added to some new
revision
> of Unicode.
>
> By the way, the situation is similar with the dandas (U+0964 and U+0965):
> they only appear in the Devanagari and Myanmar blocks, but are used for
many
> other (all?) South-Asian scripts as well. Worse, they are often used, so
> there is already many material that is encoded with these codepoints.
> Luckily, dandas do not need special handling from complex script engines,
> so it does not matter if Uniscribe decide they are Devanagri or
script-less
> (except perhaps on the selection of the font).
>
>
> Antoine
>
>
>
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