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RE: ligature formation across text chunks

From: Rik Cabanier <cabanier@adobe.com>
Date: Thu, 19 May 2011 21:17:39 -0700
To: "'Cameron McCormack'" <cam@mcc.id.au>, Glenn Adams <glenn@skynav.com>
CC: Tavmjong Bah <tavmjong@free.fr>, Vincent Hardy <vhardy@adobe.com>, "public-svg-wg@w3.org" <public-svg-wg@w3.org>
Message-ID: <8A13F0222395BD428969E5BA529EFA74777F321505@NAMBX01.corp.adobe.com>
> > > When the resulting space between two characters is not the same as
> > > the default space, user agents should not use optional ligatures.
> 
> I missed that, thanks.

I do not believe that us true. For certain ligatures, the characters will be closer together than the individual glyphs.
See the attached PDF as an example.
This is also the reason that the auto-generation of ligatures in SVG is not a good idea because it will create gaps or overlap with subsequent glyghs.

Rik


> -----Original Message-----
> From: public-svg-wg-request@w3.org [mailto:public-svg-wg-
> request@w3.org] On Behalf Of Cameron McCormack
> Sent: Thursday, May 19, 2011 9:03 PM
> To: Glenn Adams
> Cc: Tavmjong Bah; Vincent Hardy; public-svg-wg@w3.org
> Subject: Re: ligature formation across text chunks
> 
> Glenn Adams:
> > The current css3-text has the following under [1]:
> ...
> > > If the UA cannot expand a cursive script without breaking the
> > > cursive connections, it should not apply letter-spacing between
> > > grapheme clusters of that script at all.
> >
> > > When the resulting space between two characters is not the same as
> > > the default space, user agents should not use optional ligatures.
> 
> I missed that, thanks.
> 
> > This text provides for the Arabic Script case (a cursive script), by
> > indicating that the space to be extended is between disjoint graphemes.
> > Furthermore, this text provides for the case that only optional (but
> > not
> > mandatory) ligatures be disabled when a letter space would apply
> > between the characters that contribute to the ligature's component
> allographs.
> 
> That sounds reasonable.
> 
> > I believe this text (the last sentence) may be acceptable in Indic
> > scripts as well, since it only prevents optional conjunct formation in
> > the case that letter spacing is non-zero. The only issue then is if an
> > author wanted to use letter spacing *and* still have (some or all)
> > optional ligatures
> > (conjuncts) used. The alternative in that case would be to use an
> > authoring tool that performs its own letter spacing and outputs glyphs
> > at specific origins.
> 
> Maybe font-variant can be used to force optional ligatures to be used in this
> case?
> 
> --
> Cameron McCormack ≝ http://mcc.id.au/



Received on Friday, 20 May 2011 04:23:46 GMT

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