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

2 Jun 2017

      On Fri, Jun 2, 2017 at 1:39 PM, Mikael P. Sundqvist  wrote:
...
On Fri, Jun 2, 2017 at 11:39 AM, Mathias Schickel
 wrote:
...
Hi Mikael,
math fonts are a bit different from text fonts. This means that you need special methods to influence them. Because I once had a similar concern like you I asked Hans to implement a way to influence kerning in math fonts between certain glyphs. I have attached an lfg-file that shows how to use it.
To enable a goodie file like the one attached you have to define your typescript like
\starttypescript [\s!math][cambriaown][\s!all]
        \loadfontgoodies[cambriaown-math]
        \definefontsynonym[\s!MathRoman]        [Cambria-Math]                  [\s!features={\s!math\mathsizesuffix},\s!designsize=\s!auto,\s!goodies=cambriaown-math]
\stoptypescript
I hope this helps!
Best
Mathias
...
Am 02.06.2017 um 10:59 schrieb Mikael P. Sundqvist :
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.
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Thank you very much for your reply, Mathias!
I'm not sure I get it, though. I find that there is already a file
lucida-opentype-math.lfg in the distribution.
Just experimenting, I added to this file an entry with kernpairs (see
below), to see if I could make a change with a and b (if I cannot
manage that, I don't see how I could get the prime and parenthesis
case to work).
%%% start of my new lucida-opentype-math.lfg
----- kern_250 = { bottomright = { { kern = -250 } }, force = true }
return {
    name = "lucida-opentype-math",
    version = "1.00",
    comment = "Goodies that complement lucida opentype.",
    author = "Hans Hagen",
    copyright = "ConTeXt development team",
    mathematics = {
        alternates = {
            italic       = { feature = 'ss01', value = 1, comment =
"Mathematical Alternative Lowercase Italic" },
            arrow        = { feature = 'ss02', value = 1, comment =
"Mathematical Alternative Smaller Arrows" },
            operator     = { feature = 'ss03', value = 1, comment =
"Mathematical Alternative Smaller Operators" },
            calligraphic = { feature = 'ss04', value = 1, comment =
"Mathematical Alternative Calligraphic Characters" },
            zero         = { feature = 'ss05', value = 1, comment =
"Mathematical Alternative Zero" },
            partial      = { feature = 'ss20', value = 1, comment =
"Mathematical Alternative Upright Partial Differential" },
        },
     -- kerns = {
     --     [0x1D449] = kern_250, --
     --     [0x1D44A] = kern_250, -- 𝑊
     -- },
        kernpairs = {
           [0x1D44E] =    {      -- a
               [0x1D44F] = -200,} -- b
        },
        dimensions = {
            default = { -- experimental values
                [0x2044] = { xoffset = 275, width = 600 },
--                 [0x2032] = { yoffset = -10 },
            },
        },
    },
}
%%% end of lucida-opentype-math.lfg
but in the output of
\setupbodyfont[lucidaot,10pt]
\startTEXpage[offset=3pt]
$ab$
\stopTEXpage
I see no changes in the spacing between a and b.
Any ideas?
/Mikael
If I change the dimensions tag in the lucida-opentype-math.lfg into

        dimensions = {
            default = { -- experimental values
                [0x2044] = { xoffset = 275, width = 600 },
                [0x2032] = { xoffset = 40, width = 290 }, -- prime
                [0x2033] = { xoffset = 40, width = 690 }, -- double prime
                [0x2034] = { xoffset = 40, width = 1090 }, -- triple prime
                [0x2057] = { xoffset = 40, width = 1490 }, -- quadruple prime
--                 [0x2032] = { yoffset = -10 },
            },

I get something that looks better (look at the attached pdf file). But
I don't know the side-effects of changing the offset and with of
glyphs like that. It might break something at some other place, I
guess.

Hans, is there a way to work only on the pair between the prime and
the parenthesis?

/Mikael