[Tex/LaTex] The % symbol overlaps inside a listing with MatLab code

Question

I'm using the listings package to insert MatLab routines that I've created for some papers I need to write. Everything works awesome, except the symbol % (comment in MatLab) which overlaps with the next character. Below there's an image that shows this phenomenon.

And the MWE showing the problem is attached below:

\documentclass[letterpaper,12pt,openany,final]{memoir}
\usepackage[utf8x]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{graphicx} %Gráficos
\usepackage[top=4cm,right=2.5cm,left=3cm, bottom=3cm]{geometry}
\usepackage{ucs}
\usepackage{xcolor}
\usepackage{color,calc,graphicx,soul}
\usepackage{float}
 \usepackage{rotating}
 \usepackage{parskip}
\usepackage{mathptmx}%Fuente
\usepackage{epstopdf}

\setlength{\evensidemargin}{\oddsidemargin}

\title{Lorem Ipsum}
\author{DOlor Sit amet}

\usepackage{textcomp}
\usepackage{listingsutf8}
\renewcommand\lstlistingname{Código}
\renewcommand\lstlistlistingname{Índice de Códigos Fuente}

\lstset{
    backgroundcolor=\color{white},
    tabsize=4,
    rulecolor=,
    literate={ó}{{\'o}}1
         {á}{{\'a}}1
         {é}{{\'e}}1
         {º}{{\textdegree}}1
         {ú}{{\'u}}1,
    escapeinside={\%*}{*)},
    language=octave,
        basicstyle=\scriptsize,
        numberstyle=\tiny,
        upquote=true,
        aboveskip={1.5\baselineskip},
        columns=fixed,
        showstringspaces=false,
        extendedchars=true,
        breaklines=true,
        prebreak = \raisebox{0ex}[0ex][0ex]{\ensuremath{\hookleftarrow}},
        frame=single,
        showtabs=false,
        name=Feedservoplot
        showspaces=false,
        texcl=false,
        inputencoding=latin1,
        numbers=left,
        firstnumber=auto,
    showstringspaces=false,
        identifierstyle=\ttfamily,
        keywordstyle=\color[rgb]{0,0,1},
        commentstyle=\color[rgb]{0.133,0.545,0.133},
        stringstyle=\color[rgb]{0.627,0.126,0.941},
        escapeinside={(*@}{@*)}
}
    
\usepackage[protrusion=true,expansion=true]{microtype}  %Alineado óptico
\usepackage{amssymb}
\usepackage{amsmath}

\usepackage[activeacute,spanish] {babel}
\renewcommand\shorthandsspanish{}
\renewcommand{\arraystretch}{1.2}
\clubpenalty=10000
\widowpenalty=10000
\setcounter{tocdepth}{2}
\setcounter{secnumdepth}{2}
\setcounter{lofdepth}{2}
\usepackage[]{hyperref}
\usepackage{memhfixc}
\begin{document}
\setcounter{chapter}{1}

\setlength{\evensidemargin}{\oddsidemargin}

\chapter{Lorem ipsum}

Lorem ipsum dolor sit amet:

\begin{lstlisting}
a%
\end{lstlisting}

\begin{equation}
\frac{d}{dt} \frac{\partial \mathcal{L}}{\partial \dot{q_i}}
\end{equation} 
\begin{equation}
 a<0
\end{equation} 

\end{document}

Any suggestions?
Thanks in advance.

Best regards,

Charlie

PS: I must say that I don't know if this happens with other prog. languages.

Answer 1

The problem comes from the a bad interaction with the spanish module for babel, as the following MWE shows:

\documentclass{memoir}
\usepackage[spanish]{babel}
\usepackage{listingsutf8}
\spanishplainpercent

\begin{document}

\begin{lstlisting}
%A
%a
%b
\end{lstlisting}

\end{document}

The spanish module makes osme special treatment for the percentage symbol and this produces the undesired result. Using \spanishplainpercent solves the problem:

\documentclass{memoir}
\usepackage[spanish]{babel}
\usepackage{listingsutf8}
\spanishplainpercent

\begin{document}

\begin{lstlisting}
%A
%a
%b
\end{lstlisting}

\end{document}

If for other parts of your document you want to keep the fine space that the module introduces for the percentage symbol, you can do the following:

\documentclass{memoir}
\usepackage[spanish]{babel}
\usepackage{listingsutf8}

\makeatletter
\def\spanishplainpercent{\let\es@sppercent\@empty}
\def\spanishpercent{\def\es@sppercent{\unskip\textormath{$\m@th\,$}{\,}}}
\makeatother

\begin{document}

8\%

\spanishplainpercent 8\%
\begin{lstlisting}
%A
%a
%b
\end{lstlisting}
\spanishpercent

8\%

\end{document}

\spanishplainpercent deactivates the fine space (and solves the problem with listings) and \spanishpercent activates the space.

This can be done automatically using the etoolbox package:

\usepackage{etoolbox}

\makeatletter
\def\spanishplainpercent{\let\es@sppercent\@empty}
\def\spanishpercent{\def\es@sppercent{\unskip\textormath{$\m@th\,$}{\,}}}
\makeatother

\AtBeginEnvironment{lstlisting}{\spanishplainpercent}
\AtEndEnvironment{lstlistings}{\spanishpercent}