Re: 'kern': TrueType table and GPOS lookup feature

[Khaled Hosny <khaledhosny@eglug.org>]

On Sun, Dec 02, 2012 at 10:58:56AM +0100, Steve White wrote:
> Hi all,
> 
> I finally got something like Pablo's test working on my system.  It doesn't
> show much new.  As had already been established, with the right ConTeXt
> switches, OpenType features of kerning and ligatures work correctly with
> FreeSerif.
> 
> Find attached.  If there's a better way to do this, please comment: I may
> put some of this in the FreeFront usage notes.  (Hm... I may tighten the
> italic y a bit.)
> 
> A question remains: Why does ConTeXt (like some other TeX derivatives that
> use OpenType) not determine the OpenType script of runs of text from the
> Unicode (or other encoding) character range?  All other font layout systems
> I know of do this.  (Remember- a run of text in the OpenType sense is not
> the same as the scope of a TeX environment, it is typically a word,
> separated by white space or punctuation.)

Determining the script of a run of text is not that simple, take
"english (ARABIC.)"; to which script should the parenthesis and the
period be classified? (they have a "common" script property in Unicode
and not assigned to any given script). Unicode annex #24 provides an
algorithm for to handle this that an engine should implement:
http://www.unicode.org/reports/tr24/

Regards,
 Khaled
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