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Re: [css3-text] script categories, 'bicameral', 'discrete', Unicode links and more

From: John Hudson <tiro@tiro.com>
Date: Fri, 15 Apr 2011 12:38:34 -0700
Message-ID: <4DA89EBA.2060406@tiro.com>
To: Asmus Freytag <asmusf@ix.netcom.com>
CC: fantasai <fantasai.lists@inkedblade.net>, John Cowan <cowan@mercury.ccil.org>, Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>, 'WWW International' <www-international@w3.org>, public-i18n-core@w3.org, indic <public-i18n-indic@w3.org>, CJK discussion <public-i18n-cjk@w3.org>, www-style@w3.org
Asmus wrote:

> In English you may find narrow columns that are typeset with 
> letterspacing to make them justified. If you do the same in German, many 
> readers will mistake this for an attempt at  e m p h a s i s. (It used 
> to be more common, especially so during the age of Fraktur, but it's 
> widespread enough that some people use it manually, like I did here, in 
> internet postings).

> Whether letter-spacing is "allowed" for justification depends thus not 
> only on the script, but on (local) conventions. In the example I gave, 
> letter-spacing is allowed for emphasis, but not for justification (the 
> latter, if you attempted it, would look like a ransom note to readers 
> who are used to interpret letterspacing as emphasis).
...

> In typesetting German in Fraktur there are a number of required 
> ligatures. These are not broken apart when letterspacing is applied (for 
> emphasis).

Yes, there is a hierarchy of typographic behaviours that is expressible 
as either

	Script -> Language -> Style

or as

	Script -> Style -> Language

which is to say that sometimes the language (perhaps better thought of 
as local conventional) behaviour is a variation of the typical 
script-level behaviour and sometimes it is a variation within a 
particular style that is itself a variation of the script-level 
behaviour. In functional terms, sometimes you want to define language 
level behaviour in contrast to script level behaviour, while at other 
times one wants to insert the style behaviour between the script and the 
language levels.

[At the font level, OpenType enforces a script-language-lookup 
hierarchy, which means that style behaviour, insofar as it is possible 
to define this with regard to GSUB and GPOS layout, is implemented at 
the lookup level. This works, but isn't always as efficient as it would 
be if there were the option to define a style level between script and 
language. It is possible, within this system, to inhibit letter spacing 
by using the <curs> Cursive Attachment GPOS lookup type, which locks 
glyphs together in particular x,y relationships; however, the majority 
of Latin script cursive style fonts do not implement this because they 
do not employ any y-direction position adjustments, and hence do not 
strictly need <curs> attachment for most layout needs.]

JH
Received on Friday, 15 April 2011 19:48:16 GMT

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