Re: org-mode export to (latex) PDF

[Maxim Nikulin <manikulin@gmail.com>]

On 17/07/2021 01:34, Juan Manuel Macías wrote:
> Maxim Nikulin writes:
> 
>> I think that low level implementation in browser or in some underlying
>> library is much faster
>>
>>      <dl>
>>        <dt>LM Roman 12</dt>
>>        <dd style="font-family: 'LM Roman 12'">abc абв…с</dd>
>>        <dt>LM Roman 12, CMU Serif</dt>
>>        <dd style="font-family: 'LM Roman 12', 'CMU Serif'">abc абв…с</dd>
>>      </dl>
> 
> They are two different scenarios: web publishing and book typesetting

Juan Manuel, it seems you are too inclined to book typesetting. It is 
important case and it should be supported by org. I have repeated two 
times in this thread that there is another case, namely routine quick 
notes. Such documents have another balance concerning time required to 
get acceptable result. TeX takes responsibility for a lot of defaults 
such as what spaces should be added around "=" and what ones around 
right angle bracket. Users do not need to make decisions concerning such 
design details to get accurately typeset equations.

At the age of custom charsets (often 8bit) and encodings the problem of 
multilingual texts was obvious. Unicode and UTF-8 alleviate many issues. 
It happened that Cyrillic is an edge case for Unicode TeX engines. Since 
~2000 it works out of the box for LaTeX and PdfLaTeX. Last years I did 
not need to adjust config files and regenerate formats. Hyphenation, 
default fonts (OK, "apt install cm-super" to avoid rasterized fonts is a 
bit behind defaults though no manual config is required) just work. Each 
document needs a few universal lines to setup Russian. Some users may 
have specific style files but generally source documents are quite portable.

Default fonts for LuaTeX and XeTeX do not include Cyrillic any more. 
Every user have to do a decision which fonts should be used even if one 
does not care concerning particular fonts. It increases probability to 
get a file with font configuration that is specific to Mac or Windows.

I do not actively use characters from other Unicode planes, however 
sometimes I do it for fun. Getting them completely missing is less 
preferred than displaying them with low quality font. Specifying all 
fonts requires lengthy config, probably different for LuaTeX and XeTeX. 
At first it is necessary to realize which fonts are available for 
particular glyph. Finally it makes *source* document less portable.

"font-family: 'LM Roman 12', 'CMU Serif'" above is a dumb example of 
what I consider relatively high-level config for routine documents that 
do not need to be handcrafted. Unavailable glyph or even font is not an 
error, it just causes lookup of candidates in the following items. For 
TeX maybe it is reasonable to consider fallback to complete set of fonts 
at ones (roman + mono + math) if such combination is available.

> If I want to use the GFS Porson as italics from
> another font, a Didot typeface for example, I can do this:

If it is not a book or at the stage of early draft another scenario is 
possible. Text should just appear in the compiled document, particular 
font does not matter, its choice is postponed since text content has 
higher priority. Minimal setup in invaluable.

At least with minimal examples I faced another issue: characters 
silently disappears, no warning is generated. Adding babel changes it, 
but I still believe that especially for documents with carefully chosen 
fonts. It is a serious hidden error to get "invalid char glyph" instead 
of all missed characters.

> [1] If you want to have fallback fonts, you can also do it in
> LuaTeX by adding some Lua code:
> https://tex.stackexchange.com/questions/514940/define-fallback-font-for-missing-glyphs-in-lualatex

Would you recommend such code as default for Org? Let's assume that some 
information concerning system fonts are available. I suspect, the 
accepted answer is not fool-proof. In addition, XeLaTeX requires 
something different.

luaotfload provides fallback feature close to what I expect, however it 
is necessary to explicitly specify script that I would prefer to avoid. 
Moreover it significantly increases compilation time. Sometimes LuaLaTeX 
starts to eat CPU with no progress, emoji does not work for some reason.
I am unsure concerning particular "Noto Sans CJK" since several ones are 
available.

\documentclass{article}
\usepackage{fontspec}
\usepackage{unicode-math}
\directlua{luaotfload.add_fallback
   ("seriffallback",
     {
       "Noto Serif CJK SC:mode=harf;script=sc;",
       "file:/usr/lib/firefox/fonts/TwemojiMozilla.ttf:mode=harf;"
     })
}
% TwemojiMozilla is not shown by viewers, visible in pdftotext
       %"Noto Color Emoji:mode=harf;"
% or
       %"file:/usr/share/fonts/truetype/noto/NotoColorEmoji.ttf:mode=harf;"
% </usr/share/fonts/truetype/noto/NotoColorEmoji.ttf
% ! error:  (file /usr/share/fonts/truetype/noto/NotoColorEmoji.ttf) 
(ttf): loca
% table not found
% !  ==> Fatal error occurred, no output PDF file produced!
\setmainfont{CMU Serif}[RawFeature={fallback=seriffallback}]

\directlua{luaotfload.add_fallback
   ("sansfallback",
     {
       "Noto Sans CJK SC:mode=harf;script=sc;",
       "file:/usr/lib/firefox/fonts/TwemojiMozilla.ttf:mode=harf;"
     })
}
\setsansfont{CMU Sans Serif}[RawFeature={fallback=sansfallback}]

\directlua{luaotfload.add_fallback
   ("monofallback",
     {
       "Noto Sans Mono CJK SC:mode=harf;script=sc;",
       "file:/usr/lib/firefox/fonts/TwemojiMozilla.ttf:mode=harf;"
     })
}
\setmonofont{CMU Typewriter Text}[RawFeature={fallback=monofallback}]
\begin{document}
Test¹ of superscript and ½ fraction.

\textbf{«Теорема».} \emph{Пусть} $α → ∞$ и $\beta \to \infty$.

\verb=Катет= и \textsf{гипотенуза}.

Åå. Text Greek α.

Text utf8x ≠ utf8 and math $utf8x ≠ utf8$.

Randomly chosen examples: "日本", "多喝水", "📞".

\verb=Randomly chosen examples: "日本", "多喝水", "📞".=
\end{document}