Re: Fallback fonts in LaTeX export for non latin scripts

[Juan Manuel Macías]

Ihor Radchenko writes:

> May we explicitly set the needed font around language environments?
>
> Something like
>
> \setfontforrussian
> \selectlanguage{russian}
> ....
>
> \setfontforbulgarian
> \selectlanguage{bulgarian}
> ....

There's no need. With \babelfont you can associate a font with a
language (declared with both the classic syntax and \babelprovide. And
when you use \selectlanguage, \foreignlanguage or any other babel
command or environment to switch languages, the associated font is
activated for that language. For example:

\babelprovide[import]{russian}
\babelprovide[import]{bulgarian}
\babelfont[russian]{rm}[]{Old Standard}
\babelfont[bulgarian]{rm}[]{Freeserif} 

and then:

\selectlanguage{russian}
...
\selectlanguage{bulgarian}
...

\babelprovide supports several properties. Adding the onchar=ids
fonts/letters property equates language and script, and everything in
that script is associated with a font. This would only make sense to use
when there is only one language in the document that has that script, as
we discussed before. In case like russian/bulgarian, the source of the
last babelprovide is overwritten for all cases where that script
appears.

>
>> In any case (to organize myself mentally) I thought that it could be
>> done on two levels:
>>
>> - Level 0: The fonts associated with each script are loaded (from a
>>   defcustom list) if luatex is the current engine. And low-level code is
>>   generated in Lua with the luaotfload.add_fallback function. That code
>>   can be in a Lua file or directly within the preamble, enclosed in the
>>   \directlua primitive (mode=harf means that HarfBuzz is used as otf
>>   rendering):
>> ...
>
> Sounds reasonable.
>
>> - Level 1: The user can load language properties and associate fonts
>>   with each language using Babel's high-level code (via keywords in Org,
>>   as we have commented in previous messages). Here you can also modify
>>   the default fonts (also, as we mentioned before): main, mono, sans and
>>   math. If the language is declared with an asterisk (for example:
>>   russian*) the onchar=etc property will be included in the preamble,
>>   and it would not be necessary to switch to russian explicitly. It is
>>   assumed that in this scenario the only language with Cyrillic script
>>   would be Russian. For language swithcing, in the rest of the cases,
>>   some babel command would have to be used using @@latex:@@, special
>>   blocks, etc. When Org already has its own language switching
>>   mechanism, this would be used instead. Wdyt?
>
> I am not sure if I like "russian*" idea. May you explain a bit more
> about how onchar works? What if language characters are intersecting,
> and not using exactly the same char sets?

Basically, it's like I said above. According to the Babel Manual:

#+begin_quote
onchar= ids | fonts | letters

This option is much like an ‘event’ called when a character belonging to
the script of this locale is found (as its name implies, it acts on
characters, not on spaces). There are currently two ‘actions’, which can
be used at the same time (separated by a space): with ids the \language
and the \localeid are set to the values of this locale; with fonts, the
fonts are changed to those of this locale (as set with \babelfont).
Characters can be added or modified with \babelcharproperty.

[...] Option letters restricts the ‘actions’ to letters, in the TEX
sense (i. e., with catcode 11). Digits and punctuation are then
considered part of current locale (as set by a selector). This option is
useful when the main script is non-Latin and there is a secondary one
whose script is Latin.
#+end_quote


-- 
Juan Manuel Macías 

https://juanmanuelmacias.com

https://lunotipia.juanmanuelmacias.com

https://gnutas.juanmanuelmacias.com