[luatex] How to query fonts.handlers

[Henri Menke]

On 6/02/19 10:36 AM, Ulrike Fischer wrote:
> Am Mon, 4 Feb 2019 15:00:12 +1300 schrieb Henri Menke:
> 
>> Dear list,
>>
>> I am trying to access extra kerning that I have defined using
>> fonts.handlers.otf.addfeature.  Even though I query the kerning from
>> within a paragraph where the kerning is evidently applied I can't seem
>> to get the value stored earlier, see the comment in the MWE.  What am I
>> doing wrong?
> 
> Your value is in the ktest lookup, so you need to read this:

Great! That's a step in the right direction. However it requires me to
know which lookup to query. Is there a way to query the lookups?

Cheers, Henri

> 
> \input luaotfload.sty
> 
> 
> \directlua{
>      fonts.handlers.otf.addfeature {
>          name = "ktest",
>          type = "kern",
>          data = {
>              ["t"] = { ["e"] = 500 },
>          }
>      }
> }
> 
> \font\1="file:lmroman10-regular.otf:mode=node;+ktest;" at 10pt
> \1
> 
> test%
> \directlua{
>      local fnt = font.current()
>      local tfmdata = font.getfont(fnt)
>      local t = string.byte("t")
>      local e = string.byte("e")
>      local kern = fonts.handlers.otf.getkern(tfmdata,t,e,"ktest")
>      local kern = kern / tfmdata.parameters.factor
>      tex.sprint(kern) % 500 
>    }
> \bye
> 
>