Re: [possible patch] Basic fontspec code for LuaLaTeX and XelaTeX (was "LaTeX export: when is it more useful...")

[Max Nikulin]

On 11/07/2022 03:23, Juan Manuel Macías wrote:
> 3. A variable (something like 'org-latex-fontspec-default-configuration') would 
> return something like this:
>
> (format
>   \\usepackage{iftex}
>   \\ifpdftex

I like the idea of unified preamble suitable for pdflatex and lualatex. 
For pdftex \usepackage[...]{fontenc} line may be added here.

>   \\relax
>   \\else

Is it the case of latex as the old engine with tex->dvi->ps workflow 
besides new XeTeX and LuaTeX? However such engine is not used by Org.

>   \\usepackage{fontspec}
>   \\usepackage{unicode-math}
>   \\defaultfontfeatures{Scale=MatchLowercase}
>   \\defaultfontfeatures[\\rmfamily]{Ligatures=TeX}
>   \\setmainfont{%s}
>   \\setsansfont{%s}
>   \\setmonofont{%s}
>   \\fi
>   org-latex-fontspec-mainfont
>   org-latex-fontspec-sansfont
>   org-latex-fontspec-monofont)

Too many variables to my taste. It can be single property list. If I 
remember correctly, changing of mainfont requires setting of a 
consistent font for mathematics, so more options may be required.

ox-latex has some code searching for e.g. \usepackage[...]{inputenc} in 
the current configuration to avoid adding of extra copy. It would be 
great to have something similar for fontspec commands. I guess, it is 
harder to detect, since per-language font configuration may be required 
as babel options.

Finally, default value may be language-dependent or alternative font set 
may be activated when non-latin characters are detected in the document.