soul package and Cyrillic with xelatex

Question

How to handle Cyrillic ymbols with soul package?

\documentclass[a4paper,10pt]{book}
\usepackage{polyglossia}
    \defaultfontfeatures{Ligatures={TeX}}
    \setmainfont{Liberation Serif}
    \setmonofont{Liberation Mono}
    \setmainlanguage{ukrainian}
\usepackage{soulutf8}
\begin{document}
    \mainmatter
    Короткий зміст\par
    Brief content\par
    \so{Короткий зміст}\par
    \so{Brief content}
\end{document}

Compile with

xelatex test.tex

I assume that this is caused by the absence of Cyrillic characters in the internal font used by soul package. It is possible to set this font with \font\SOUL@tt= but I don't know how I can use a font with this command.

I added \tracinglostchars=2 and saw this:

Missing character: There is no К in font ectt1000!
Missing character: There is no о in font ectt1000!
...
Missing character: There is no с in font ectt1000!
Missing character: There is no т in font ectt1000!

Is XeLaTeX a hard requirement or would you consider changing to LuaLaTeX? For the latter the excellent lua-ul package handles underlining flawlessly. — Skillmon, Dec 12 '21 at 18:16
And instead of \so you could use \textls provided by the microtype package in LuaTeX. — Skillmon, Dec 12 '21 at 18:23
@Skillmon I use XeTeX because I have a book typeset in XeTeX and I can't easily change to another system. — Yola, Dec 12 '21 at 18:38
Are you sure that LuaTeX doesn't work (the two are similar enough that most things should out of the box)? It should be possible to make soul work for you: You'll have to find a monospaced font that contains all characters you need. — Skillmon, Dec 12 '21 at 18:46
Special case of accents - soul dropping some accented letters from the end of words - TeX - LaTeX Stack Exchange. But looks like there's another solution specific to this question. — user202729, Nov 30 '22 at 09:37

egreg · Accepted Answer · 2021-12-12T21:34:38.197

You can locally add the LetterSpace feature.

\documentclass[a4paper,10pt]{book}
\usepackage{polyglossia}
%\defaultfontfeatures{Ligatures={TeX}} % not needed
\setmainfont{Liberation Serif}
\setmonofont{Liberation Mono}
\setmainlanguage{ukrainian}
\NewDocumentCommand{\so}{m}{%
  {\addfontfeatures{LetterSpace=10,Ligatures=NoCommon}#1}%
}
\begin{document}
\mainmatter
Короткий зміст
Brief content ffi ffl
\so{Короткий зміст}
\so{Brief content ffi ffl}
Короткий зміст
Brief content ffi ffl
\end{document}

The Ligatures=NoCommon is necessary with fonts having ligatures, as the following example with Libertinus Serif instead of Liberation shows:

Beware that stealing sheep is not considered good practice.

I know that it's common with Cyrillic to letter space also lower case for emphasis, but letter spacing Latin letters is not considered good typography.

I'm looking into sources of soul and see \let\so\textso where \textso is defined via \sodef so it has not only \SOUL@soletterskip but also \SOUL@soinnerskip and \SOUL@soouterskip. Seems like I need to know how to convert 3 \sodef parameters into LetterSpace,, maybe WordSpace, something else. — Yola, Dec 13 '21 at 02:39

score 2 · Answer 2 · answered Dec 12 '21 at 18:35

Using LuaLaTeX and the microtype package you could use \textls instead of \so. If you also need highlighting, underlining or strike through of soul you could instead use the lua-ul package in LuaLaTeX.

\documentclass[a4paper,10pt]{book}
\usepackage[letterspace=200]{microtype}
\usepackage{polyglossia}
    \defaultfontfeatures{Ligatures={TeX}}
    \setmainfont{Liberation Serif}
    \setmonofont{Liberation Mono}
    \setmainlanguage{ukrainian}
\begin{document}
    \mainmatter
    Короткий зміст\par
    Brief content\par
    \textls{Короткий зміст}\par
    \textls{Brief content}
\end{document}

soul package and Cyrillic with xelatex

2 Answers2

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