[XeTeX] wrong kerning and slow processing with xelatex in texlive 2010

[Vadim Radionov]

Hi, Jonathan,

I asked my font vendor and they explained that when specific kerning
pair accompanies a kerning class, it work as "class exception" rather
than a correction to the kerning for classes. There are several words
about it in Opentype specification. (Unfortunately, I didn't find
anything about cumulative behaviour of several specific pairs.)

Do you know how exactly XeTeX deal with it?

Vadim

>> I finally found the explanation. Mea culpa, it was in the kerning in
>> the font. All 3 lookup tables contained kerning -50 for small caps
>> Cyrillic `t' and `a', and the was another one of -60 in kerning
>> classes, which gave the total of -210.
>>
>> I'm not sure if it is allowed and what should be the default behavior
>> of typesetting program -- to add them of to use the last.
>
> Are all those lookup tables assigned to the 'kern' feature within the same script and language system? If so, then they're cumulative. If the lookups are each assigned to a different script/language, then they shouldn't all be applied at the same time.
>
> JK
>
>
>> If it is
>> stated somewhere and you can point me to it, i will complain to my
>> font vendor. And of course I will check for such cases myself and wipe
>> out extra kerning.
>
>
>
>
> --------------------------------------------------
> Subscriptions, Archive, and List information, etc.:
>  http://tug.org/mailman/listinfo/xetex
>