Hi!

Now that the bug with primes is fixed in ConTeXt, I wonder if there is
a way to change the kerning between certain characters in mathematics
(in case one is not happy with the output from the font)? After
reading in fonts-mkiv.pdf this is what I came up with:

\startluacode
fonts.handlers.otf.addfeature {
name = "kerntest",
type = "kern",
data = {
[0x61] = { [0x62] = -150 }, -- a and b in text
[0x1d44e] = { [0x1d44f] = -150 }, -- mathematical italic small a and b
[0x02032] = { [0x00028] = -150 }, -- prime and left parenthesis
}
}
\stopluacode

\definefontfeature[kerntest][kerntest=yes]

\definefontfamily[lucidaopentype][rm][Lucida Bright OT]
\definefontfamily[lucidaopentype][mm][Lucida Bright Math OT]

\setupbodyfont[lucidaopentype,10pt]


\startTEXpage[offset=3pt]
abba $abba f'(x)$

\addff{kerntest}

abba $abba f'(x)$

I prefer $f'\mkern-3mu(x)$
\stopTEXpage

The output is attached as a png file. As you see the kerning works as
expected in text mode, but not at all in math mode, even not for the a
and b (which I hope I entered correctly).

Something like the third line is what I'm after, but not having to use
\mkern in all places. Is it possible?

/Mikael

PS: This is a cross post of the question
https://tex.stackexchange.com/q/372857/52406, where I got the
suggestion to ask on the list.