Re: [NTG-context] Change kerning between math characters (prime and left parenthesis)

2 Jun 2017

      On Fri, Jun 2, 2017 at 4:24 PM, Hans Hagen  wrote:
...
On 6/2/2017 10:59 AM, Mikael P. Sundqvist wrote:
...
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:
you can also play withj:
return {
    name = "cambria-math",
    mathematics = {
       kerns = {
          [0x1D453] = {
              force = true,
              topright = {
                  {
                      kern = 1000,
                  },
              },
              bottomright = {
                  {
                      kern = 1000,
                  },
              },
          },
      },
    },
}
currently you need to enable this:
\enabledirectives[fontgoodies.mathkerning]
keep in mind that some cambria (not all) have such staircase kerns which is
why force is needed in order to overload
...
\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.
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                                          Hans Hagen | PRAGMA ADE
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___________________________________________________________________________________
If your question is of interest to others as well, please add an entry to
the Wiki!
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Thank you Hans, that works.

Is there also a similar way to use the "kernpairs" instead of "kerns"?
I get no effect, even after adding force = true and
\enabledirectives[fontgoodies.mathkerning].

/Mikael