using soul to highlight only text and math while skip any other macro

Question

I try to highlight large paragraph of text, where there are various other macros such as \cite, \SI, \ref, etc. in between.

If I do something like the following:

\hl{the duration is \SI{4}{\second} as shown in Figure~\ref{fig:fig1} \citep{Doe2015}}

The text would truncate at "is", or even cannot compile sometimes.

Is there a way to write a macro like this:

\DeclareRobustCommand{\robusthl}[1]{
    \ifnotmacro\hl{#1}\fi}

Thank you so much!

Answer 1

Protect the offending commands in \mbox. On the other hand, underlining should be avoided as much as possible.

\documentclass{article}

\usepackage{soul,siunitx,natbib}
\soulregister{\ref}{1}
\soulregister{\citep}{1}

\begin{document}

\hl{the duration is \mbox{\SI{4}{\second}} as shown in
Figure~\mbox{\ref{fig:fig1}} \mbox{\citep{Doe2015}}}

\begin{figure}\caption{X}\label{fig:fig1}\end{figure}

\begin{thebibliography}{1}

\bibitem[Doe(2015)]{Doe2015} A paper

\end{thebibliography}

\end{document}