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I want to highlight either a whole line of code in a listing, or a part of line (a subexpression) using background color (to not interfere with syntax highlighting).

I use lstlistings environment from 'listings' package.

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(to not interfere with syntax highlighting) Does it have to be a background-color solution or would you also be happy with some text style applied "on top" of syntax highlighting (e.g., make the text color red while keeping boldface for keywords). –  Daniel Dec 2 '11 at 16:26
    
Since you have some responses below that seem to answer your question, please consider marking one of them as ‘Accepted’ by clicking on the tickmark below their vote count (see How do you accept an answer?). This shows which answer helped you most, and it assigns reputation points to the author of the answer (and to you!). It's part of this site's idea to identify good questions and answers through upvotes and acceptance of answers. –  Jubobs Mar 1 at 22:28
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2 Answers

up vote 6 down vote accepted

Listings allow escaping to TeX, so you can put a box in the background:

\documentclass{standalone}
\usepackage{listings,xcolor}
\lstset{language=c,escapechar=|}
\begin{document}
\begin{lstlisting}
int main (int argc, char ** argv)
{
  |\makebox[0pt]{\color{yellow}\rule[-0.1ex]{30em}{2ex}}|printf("Hello, world\n");
  exit(0);
}
\end{lstlisting}
\end{document}

enter image description here

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if the listing environment has background, this solution may not work well -- there may be spaces that break the listing background. –  An Cong Tran Feb 10 at 3:48
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Here is one easy-to-use solution built on posts from this site.

Sources :

  1. Creating a zebra effect using listings
  2. Listing, zebra effect and broken lines
  3. Highlighting line ranges in a lstlisting: partial solution, but expansion issues

The code:

\documentclass[10pt,a4paper]{article}
    \usepackage[utf8x]{inputenc}
    \usepackage{ucs}
    \usepackage{amsmath}
    \usepackage{amsfonts}
    \usepackage{amssymb}

    \usepackage{xcolor}
    \usepackage{listings}

    \usepackage{pgf}
    \usepackage{pgffor}

% Define backgroundcolor
    \usepackage[
        style=1,
        skipbelow=\topskip,
        skipabove=\topskip
    ]{mdframed}

    \definecolor{bggray}{rgb}{0.85, 0.85, 0.85}
    \mdfsetup{
        leftmargin = 20pt,
        rightmargin = 20pt,
        backgroundcolor = bggray,
        middlelinecolor = black,
        roundcorner = 15
    }
    \BeforeBeginEnvironment{lstlisting}{\begin{mdframed}\vskip-.5\baselineskip}
    \AfterEndEnvironment{lstlisting}{\end{mdframed}}

    \makeatletter
%
% \btIfInRange{number}{range list}{TRUE}{FALSE}
%
% Test if int number <number> is element of a (comma separated) list of ranges
% (such as: {1,3-5,7,10-12,14}) and processes <TRUE> or <FALSE> respectively
%
        \newcount\bt@rangea
        \newcount\bt@rangeb

        \newcommand\btIfInRange[2]{%
            \global\let\bt@inrange\@secondoftwo%
            \edef\bt@rangelist{#2}%
            \foreach \range in \bt@rangelist {%
                \afterassignment\bt@getrangeb%
                \bt@rangea=0\range\relax%
                \pgfmathtruncatemacro\result{ ( #1 >= \bt@rangea) && (#1 <= \bt@rangeb) }%
                \ifnum\result=1\relax%
                    \breakforeach%
                    \global\let\bt@inrange\@firstoftwo%
                \fi%
            }%
            \bt@inrange%
        }

        \newcommand\bt@getrangeb{%
            \@ifnextchar\relax%
            {\bt@rangeb=\bt@rangea}%
            {\@getrangeb}%
        }

        \def\@getrangeb-#1\relax{%
            \ifx\relax#1\relax%
                \bt@rangeb=100000%   \maxdimen is too large for pgfmath
            \else%
                \bt@rangeb=#1\relax%
            \fi%
        }

%
% \btLstHL{range list}
%
        \newcommand{\btLstHL}[1]{%
            \btIfInRange{\value{lstnumber}}{#1}%
            {\color{blue!30}}%
            {\def\lst@linebgrd}%
        }%

%
% \btInputEmph[listing options]{range list}{file name}
%
        \newcommand{\btLstInputEmph}[3][\empty]{%
            \lstset{%
                linebackgroundcolor=\btLstHL{#2}%
                \lstinputlisting{#3}%
            }% \only
        }

% Patch line number key to call line background macro
        \lst@Key{numbers}{none}{%
            \def\lst@PlaceNumber{\lst@linebgrd}%
            \lstKV@SwitchCases{#1}{%
                none&\\%
                left&\def\lst@PlaceNumber{\llap{\normalfont
                \lst@numberstyle{\thelstnumber}\kern\lst@numbersep}\lst@linebgrd}\\%
                right&\def\lst@PlaceNumber{\rlap{\normalfont
                \kern\linewidth \kern\lst@numbersep
                \lst@numberstyle{\thelstnumber}}\lst@linebgrd}%
            }{%
                \PackageError{Listings}{Numbers #1 unknown}\@ehc%
            }%
        }

% New keys
        \lst@Key{linebackgroundcolor}{}{%
            \def\lst@linebgrdcolor{#1}%
        }
        \lst@Key{linebackgroundsep}{0pt}{%
            \def\lst@linebgrdsep{#1}%
        }
        \lst@Key{linebackgroundwidth}{\linewidth}{%
            \def\lst@linebgrdwidth{#1}%
        }
        \lst@Key{linebackgroundheight}{\ht\strutbox}{%
            \def\lst@linebgrdheight{#1}%
        }
        \lst@Key{linebackgrounddepth}{\dp\strutbox}{%
            \def\lst@linebgrddepth{#1}%
        }
        \lst@Key{linebackgroundcmd}{\color@block}{%
            \def\lst@linebgrdcmd{#1}%
        }

% Line Background macro
        \newcommand{\lst@linebgrd}{%
            \ifx\lst@linebgrdcolor\empty\else
                \rlap{%
                    \lst@basicstyle
                    \color{-.}% By default use the opposite (`-`) of the current color (`.`) as background
                    \lst@linebgrdcolor{%
                        \kern-\dimexpr\lst@linebgrdsep\relax%
                        \lst@linebgrdcmd{\lst@linebgrdwidth}{\lst@linebgrdheight}{\lst@linebgrddepth}%
                    }%
                }%
            \fi
        }

    \makeatother


\begin{document}

\begin{lstlisting}[
    language = C,
    linebackgroundcolor = {\btLstHL{4-6,9}},
]
/**
* Prints Hello World.
**/
#include <stdio.h>
}
int main(void) {
    printf("Hello World!");  
    return 0;
}
\end{lstlisting}

\end{document}

enter image description here

share|improve this answer
    
Was thinking about a similar solution, but realized that it will work only with highlighting full lines, not partial lines. Still very useful to have. One suggestion: can you make the sources on this site as part of the text (as opposed to part of the code) so that they are click able links, and post an image. –  Peter Grill Dec 2 '11 at 18:16
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