[Fontconfig] editing FcConfig in code

[Idriss Fekir]

On 4/14/23 12:16, Akira TAGOH wrote:
> On Thu, Apr 13, 2023 at 10:48 PM Idriss Fekir <mcsm224 at gmail.com> wrote:
>> Sorry, my question wasn't clear, what i meant is, is there a way in in
>> the config file to say, "if given this string, match it to this psname,
>> or this full_name", e.g: if given "Iosevka Extrabold Extended Oblique"
>> match it to the font with psname:"Iosevka-Extrabold-Extended-Oblique".
> 
> No. we could guess a postscript name from family and/or fullname but
> it is't perfect because they are stored as independent metadata. they
> are free to set regardless of regularity.
> 
> So you need to do compare "family" and "postscriptname" separately.
> 
>>>> My goal is, at application startup to check for fonts that aren't
>>>> matched properly, then remap then load the config, is there a general
>>>> solution?
>>>
>>> That depends on the meaning of "not matched". speaking of the fallback
>>> font, that is exactly what fontconfig does. In case of your issue,
>>> that is the case-by-case. If there are any generally useful solutions,
>>> please let us know.
>>>
>>
>> What could be done in this particular case? that is,
>> `fc-match "Isoveka Extrabold Extended Oblique"` outputs
>> `Noto Sans Regular` instead of the correct font.
> 
> You want to substitute it with Noto Sans no matter what they exist and
> change the weight and the slant too?

No, i just want for the font to match correctly,
`fc-match "Isoveka Extrabold Extended Oblique"` should output 
`iosevka-extrabold.ttc: "Iosevka" "Extrabold Extended Oblique"`
but it doesn't output that. It outputs `NotoSans-Regular.ttf: "Noto 
Sans" "Regular"`, which is wrong since i do have that Iosevka font 
installed.

The only way i'm getting the correct font is with
`fc-match ":postscriptname=Iosevka-Extrabold-Extended-Oblique"`
i just want the output of:
`fc-match "Isoveka Extrabold Extended Oblique"`
to be identical to the output of:
`fc-match ":postscriptname=Iosevka-Extrabold-Extended-Oblique"`
(because matching like this with the psname outputs the correct font)

Really sorry that my previous question wasn't clear enough.

> I didn't test but this may *theoretically* works:
> 
> <match>
>    <test name="fullname">
>      <string>Isoveka Extrabold Extended Oblique</string>
>    </test>
>    <edit name="family" mode="prepend">
>      <string>Noto Sans</string>
>    </edit>
>    <edit name="weight" mode="prepend">
>      <const>regular</const>
>    </edit>
>    <edit name="slant" mode="prepend">
>      <const>roman</const>
>    </edit>
> </match>
> 
> This assumes that applications request a font with fullname. you may
> need to replace it with "family", and "style" or "weight" and "slant"
> in some case.
> If you want to fallback only when they aren't available, that may be
> much more complicated.
> 
>> Another question, what does `FcConfigSubstituteWithPat` do, i couldn't
>> understand from the man page.
> 
> Well, there are three matching patterns in fontconfig. "pattern",
> "font", and "scan". These patterns are performed only when "kind" is
> the same. however, if you call FcConfigSubstituteWithPat(config,
> pfont, ppat, FcMatchFont) then, you can get both "pattern" in ppat and
> "font" in pfont FcPatterns. see FcFontRenderPrepare() for more
> details.
> 
>>
>> Sorry for asking so many questions.
>>
>> Thank.
>> --
>> Idriss
> 
> 
> 

Thank a lot.
-- 
Idriss