[XeTeX] optical sizes not found

[Roland Kuhn]

  Am 05.10.2010 22:41, schrieb Khaled Hosny:
> On Tue, Oct 05, 2010 at 10:32:51PM +0200, Roland Kuhn wrote:
>>   Hi,
>>
>> a few days back I asked about a problem with optical font sizes: for
>> me, the correct fonts are not automatically selected. I can rule out
>> a fontspec bug, since the problem exists also in plain XeTeX:
>>
>> \font\1="Kepler Std" at 9pt\1
>> Hallo Welt!
>> \font\2="Kepler Std" at 12pt\2
>> Hallo Welt!
>> \font\3="Kepler Std" at 14pt\3
>> Hallo Welt!
>> \font\4="Kepler Std" at 24pt\4
>> Hallo Welt!
>> \end
>>
>> This results in a PDF containing only the KeplerStd-Regular font (no
>> Capt, Subh or Disp variants). Now I've had the opportunity to test
>> this using the same OTF files on a Windows 7 computer with an
>> up-to-date TL2010 installation, and the same happens as on my Mac
>> (Snow Leopard, same TL2010 revision).
>>
>> Could it be that the fonts do not contain some needed hints? (I'm
>> using the version from 2003.) How does font selection work on the
>> inside?
> The font need to have a "size" feature for automatic optical size
> selection to work, you can check with otfinfo (part of texlive) if the
> font have such feature. If not, then fontspec has options for manually
> selecting optical sizes.
>
> Regards,
>   Khaled
>
Yes, I was aware of the feature, and here is the output of "otfinfo -z" 
on my regular ("Text") variant:

design size 11 pt, size range (8.9 pt, 13.9 pt], subfamily ID 4, 
subfamily name Regular

I wonder where XeTeX should now take the information to look for a font 
named KeplerStd-Capt.otf or "Kepler Std Capt" when I select it at 8pt? 
(forget my 9pt in the example above, I've just verified that using 8pt 
does not make a difference)

Regards,

Roland