Define an underline with white contour that allows breaklines and hyphenation

Question

I define an underline (based on the following site: https://alexwlchan.net/2017/10/latex-underlines/).

This was my initial code:

\usepackage{ulem}
\renewcommand{\ULdepth}{1.8pt}
\contourlength{0.8pt}
\newcommand{\myuline}[1]{%
  \uline{\phantom{#1}}%
  \llap{\contour{white}{#1}}%
}

The problem with the code is that it doesn't allow linebreaks nor hyphenations if I underline a lot of text. I made some research and found that \phantom and \contour could be the problem, so I replace \phantom with \textcolor in white, and add the following (to allow contour break lines):

\usepackage{ulem}
\renewcommand{\ULdepth}{1.8pt}
\contourlength{0.8pt}
% contour each word to allow linebreaks
\RequirePackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\MIR}{m}
 {
  \seq_set_split:Nnn \l_tmpa_seq { ~ } { #1 }
  \seq_map_inline:Nn \l_tmpa_seq { \contour{white}{##1} ~ } \unskip
 }
\ExplSyntaxOff
% define underline
\newcommand{\myuline}[1]{%
  \uline{\textcolor{white}{#1}}%
  \llap{\contour{white}{#1}}%
}

but this didn't solve my problem, and now I realized that \llap doesn't allow linebreaks nor hyphenation too ... then, I don't know how can I solve the problem. Please help.

Thank you very much @Bernard for the corrections, I think I should improve my English. — hllspwn, Sep 15 '20 at 13:18
Perhaps related: https://tex.stackexchange.com/questions/126291/list-of-underlining-packages-pros-and-cons — Steven B. Segletes, Sep 15 '20 at 13:23

score 1 · Answer 1 · answered Oct 24 '21 at 17:07

Modifying what you have, you can use the following

\usepackage{contour}
\usepackage[normalem]{ulem}
\renewcommand{\ULdepth}{1.8pt}
\contourlength{0.8pt}
\newcommand{\myuline}[1]{%
  \uline{\phantom{#1}}%
  \llap{\contour{white}{#1}}%
}
% myuline on each word to allow linebreaks
\RequirePackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand{\myulineX}{m}
 {
  \seq_set_split:Nnn \l_tmpa_seq { ~ } { #1 }
  \seq_map_inline:Nn \l_tmpa_seq { \myuline{##1} ~ } \unskip
 }
\ExplSyntaxOff

Then you can get alexwlchan's nice underlines that you want, and also get them to work across line-breaks. Use it like:

\myulineX{Now the \texttt{myulineX} text will have nice underlines that avoid
  descenders, and also don't cause issues with line-breaking.}

to get:

However, the underlines don't continue through spaces between words. If that's an issue, I don't know how to solve that (also see comment here to the same effect, I think).

Define an underline with white contour that allows breaklines and hyphenation

1 Answers1