[XeTeX] [off-topic] proper OpenType tag for hanging diacritics

Khaled Hosny khaledhosny at eglug.org
Fri Dec 25 14:57:01 CET 2009

Though it is bit late, I just came across this post on Typophile and
thought it might be of interest to you:


On Mon, Oct 05, 2009 at 08:54:47PM +0200, Pablo Rodríguez wrote:
> Hi there,
> this is mainly a question for OpenType experts, but I guess anyone can
> enjoy the beauty of the texts composed with XeTeX.
> At http://diosas-nubes.blogspot.com/2009/09/mas-ligaduras.html, you can
> find an ancient Greek text typeset with XeTeX and ledmac.
> There are two images, with and without Greek ligatures enabled. The font
> used is GFS Baskerville. But there is a problem that you can see at the
> end of line 14 on the first image: the space before the uppercase letter
> with diacritics is wrong.
> The problem comes from the font itself, since it has a negative value
> for the left bearing of capital letters with diacritics.
> The explanation for the issue was to properly align Greek capital
> letters with hanging diacritics at the beginning of the line in a left
> aligned paragraph. This was a convention in Greek poetry (as Yannis
> Haralambous described in section 3.5 from
> http://omega.enstb.org/yannis/pdf/thessaloniki.pdf).
> I'm afraid that this was the worst way of solving the issue, because the
> effects when composing non-verse texts are obvious, since they can
> contain words beginning with capital letters with diacritics in the
> middle of a sentence..
> A way to avoid this would be to add a kerning pair with the space
> character and add the value from the left bearing to the kerning. But
> this is only a workaround and not the proper fix.
> I thought there might be a proper feature for this in OpenType (from the
> GPOS table). After having a quick look at the list of registered
> features (http://www.microsoft.com/typography/otspec/featurelist.htm), I
> think that the optical bounds is the proper feature to do this
> (http://www.microsoft.com/typography/otspec/features_ko.htm#opbd). The
> example doesn't refer to Greek capital letters with diacritics, but I
> think it describes the same case.
> I wonder whether optical bounds are the right choice for hanging
> diacritics. And I would like to know whether XeTeX would support this
> feature with poetry.
> Thanks for your help,
> Pablo

 Khaled Hosny
 Arabic localiser and member of Arabeyes.org team
 Free font developer
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