Re: Adjust kern for one character

[Rik Kabel <ConTeXt@rik.users.panix.com>]

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On 12/23/2019 18:45, Rik Kabel wrote:
>
> On 12/22/2019 21:34, Henri Menke wrote:
>>
>>
>> On 12/23/19 3:33 PM, Henri Menke wrote:
>>> On 12/23/19 2:30 PM, Rik Kabel wrote:
>>>>
>>>> On 12/22/2019 17:40, mf wrote:
>>>>> Il 22/12/19 22:19, Rik Kabel ha scritto:
>>>>>> List,
>>>>>>
>>>>>> Is there a way in ConTeXt to adjust the left-side kern for one
>>>>>> character? The cap J in the font I am using is being set too 
>>>>>> close to
>>>>>> the preceding characters and I would rather not insert a thinspace
>>>>>> before each. (Inserting a thinspace is sufficient, but finer control
>>>>>> is welcome.)
>>>>>>
>>>>> \definecharacterspacing[distantJ]
>>>>> \setupcharacterspacing[distantJ]["004A][left=.15,alternative=1] % 
>>>>> 004A
>>>>> is the unicode hex index of letter J
>>>>> \starttext
>>>>>     normal: AJB\par
>>>>>     \setcharacterspacing[distantJ] more space on the left: AJB\par
>>>>>     \resetcharacterspacing normal again: AJB\par
>>>>> \stoptext
>>>>>
>>>> Thank you for that, Massi.
>>>>
>>>> Unfortunately, that is too blunt an instrument in this case -- in
>>>> addition to the body font where the problem exists, it works on the
>>>> heading and titling font, which does not share the problem.
>>>>
>>>> As Henri's answer hints, I was a bit unclear in my request. It is a 
>>>> kern
>>>> between a word space and the cap J that is the issue. Perhaps a font
>>>> feature file is the place to do such a thing.
>>>
>>> \startluacode
>>> fonts.handlers.otf.addfeature {
>>>       name = "kern",
>>>       type = "kern",
>>>       data = {
>>>           [" "] = {
>>>               ["J"] = 1000 % exaggerated value
>>
>> Should of course be a Lua comment
>>
>>             ["J"] = 1000 -- exaggerated value
>>
>>>           }
>>>       }
>>> }
>>> \stopluacode
>>>
>>> \setupbodyfont[modern] % have to reload the font
>>>
>>> \starttext
>>>
>>> No Jokes!
>>>
>>> \stoptext
>>>
> Henri,
>
> This looks very promising. It works, mostly. That is, all fonts that 
> use default fontfeatures pick up the change. So, for example, the 
> companion sansserif for my body font also gets it even though that is 
> not what I want.
>
> I can remove kerning from the default fontfeatures and add it back 
> just for the problematic font, but that means no kerning for the sans 
> font.
>
> Is there a way to apply this to one font only (serif upright, bold, 
> italic, ...) or even a single face (upright), perhaps by giving it a 
> unique name? I have tried a few variations but had no success. The 
> fonts-mkiv manual has very little on this, and the cld manual nothing.
>
Okay, I have progressed further but have run into something (else) I 
cannot understand. Consider the following example:

    \definefontfeature   [myserif] [mode=node,kern=yes,xkern=yes]
    \definefontfeature   [mysans]  [mode=node,kern=yes,xkern=no]
    \definefontfeature   [none]    [mode=node]
    \definefontfamily    [mykerns] [serif] [Baskervaldx]    [features=myserif]
    \definefontfamily    [mykerns] [sans]  [Dejavusans]     [features=mysans]
    \definefontfamily    [default] [serif] [Baskervaldx]    [features=default]
    \definefontfamily    [default] [sans]  [Dejavusans]     [features=default]
    \definefontfamily    [nokerns] [serif] [Baskervaldx]    [features=none]
    \definefontfamily    [nokerns] [sans]  [Dejavusans]     [features=none]
    \definefontfamily    [legends] [mono]  [Dejavusansmono] [features=default]

    \startluacode
       fonts.handlers.otf.addfeature {
           name = "kern",
           type = "kern",
           data = {
               ["x"] = { ["x"] = -300 },
               [" "] = { ["A"] = 1000 }
           }
       }
       fonts.handlers.otf.addfeature {
           name = "xkern",
           type = "kern",
           data = {
               ["x"] = { ["x"] = 500 },
               [" "] = { ["J"] = 500 }
           }
       }
    \stopluacode

    \startbuffer[Sample]
       g, Jaxxb AJon
    \stopbuffer

    \define[2]\Test{
       {\switchtobodyfont[#1]#2\getbuffer[Sample]}}

    \setupbodyfont[legends]

    \starttext
    \starttabulate[|l|l|l|]
    \NC test     \NC  Serif                \NC  Sans                 \NC \NR
    \NC nokerns  \NC  \Test{nokerns}{\tf}  \NC  \Test{nokerns}{\ss}  \NC \NR
    \NC default  \NC  \Test{default}{\tf}  \NC  \Test{default}{\ss}  \NC \NR
    \NC mykerns  \NC  \Test{mykerns}{\tf}  \NC  \Test{mykerns}{\ss}  \NC \NR
    \stoptabulate
    \stoptext

It shows, as far as I see, that the kern feature type supports " ", but 
only when it is named kern. When it is named xkern, as here, it does not 
support spaces, but does support other characters.

If I can get support for a separate feature name, I can easily apply 
this corrective kern to the single problematic font.

I also tried a goodie file, but it, too, did not support the " ".

-- 
Rik


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