[luatex] How to access user-defined kerning

Hans Hagen j.hagen at xs4all.nl
Fri Apr 20 08:39:30 CEST 2018

On 4/20/2018 8:24 AM, Henri Menke wrote:
> On Fri, 2018-04-20 at 07:47 +0200, Herbert Voss wrote:
>> Am 20.04.2018 um 05:52 schrieb Henri Menke:
>>> I'm trying to determine the kerning between two letters (here A and V).  For
>>> the
>>> sake of this example I'm inserting negative kerning of -400/1000 em.
>>>   However,
>>> when I examine the kern in the kerning callback this massive enhancement of
>>> the
>>> negative kern doesn't show up but I only see the kerning from the font
>>> itself.
>>> How can I access the user-defined kerns?  MWE is below.
>> no problem with
> No, that is not my problem.  The kern is correct in the output.  However, I
> cannot inspect the kern from within the "kerning" callback.  The user-defined
> kern is not added inside the kerning callback and I want to know how to query it
> (see the line annotated with <--).
the kerning and ligaturing callbacks are for text (an deven then only 
make sense for traditional fonts with a kern and ligature table)

rendering math is done completely different and is a two pass process; 
there are often two code paths, one for traditonal math and one for 
opentype and opentype

kerning/glueing there is done based on character classes, math 
parameters and specific font information (the initial math list is more 
complex than a textual node list)

eventualy the typoeset math becomes a sequence of regular nodes injected 
in the list that makes a paragraph


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