[XeTeX] Versions and AAT features in Hoefler Text

Jonathan Kew jonathan_kew at sil.org
Mon May 15 18:25:30 CEST 2006

On 15 May 2006, at 11:07 am, Bruno Voisin wrote:

> Le 12 mai 06 à 12:40, Jonathan Kew a écrit :
>> The Number Case feature went missing in Hoefler Text Regular on
>> Tiger, I believe; it was there in earlier versions (although there
>> were other inconsistencies in features/names).
>> I filed a bug report about this in May 2005 (# 4110574), but checking
>> on BugReporter still shows the status as "open". I'm bcc'ing this to
>> a couple of friends at Apple, as a little reminder.... (hi Deborah &
>> John!).
> What's most surprising is that the Number Case feature seems indeed
> to be present in the version 5.0d7e2 of Hoefler Text shipped with
> Tiger,

No, not quite . All the necessary glyphs are in the font (and so by  
re-encoding the font appropriately, it's possible to display them),  
but the AAT feature to substitute lining numerals for the default  
oldstyle ones is missing.

> and only to be inaccessible through AAT (or ATSUI, I never
> quite understood the difference):

AAT (Apple Advanced Typography) is the enhanced TrueType font format  
that includes extra tables to implement typographic features/options,  
and (I think) also refers to the overall font-layout technology;  
ATSUI (Apple Type Services for Unicode Imaging) is the particular  
implementation of AAT in the Mac OS. So we use the ATSUI programming  
interfaces and libraries to render text using AAT fonts and features.

In principle, there could be other implementations of AAT layout (and  
in fact, ICU Layout does support some AAT features, though XeTeX  
doesn't make use of this); ATSUI is the only complete one around,  
though (AFAIK).

> when using the gtamacfonts package,
> based on .ttf versions of the fonts obtained by applying Fondu to
> extract the .ttf files from their .dfont container, both oldstyle and
> lining numbers are accessible.

This is because that package re-encodes the fonts, based on glyph  
names, so as to access the various alternate glyphs from 8-bit codes  
in the old TeX world. So it neither depends on nor benefits from the  
AAT features (and bugs!) in the font, it depends only on the  
collection of glyphs.


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