Change the background color of line numbers in a lstlisting?

Question

Consider the following code which deals with a lstlisting.

\documentclass{article}

\usepackage[T1]{fontenc}
\usepackage{listings}
\usepackage{xcolor}
\lstset{basicstyle=\small\ttfamily,keywordstyle=\color{blue},language=C++,showstringspaces=false,tabsize=2,numbers=left}
\begin{document}

\begin{lstlisting}
#include <stdio.h>
int main(void) {
  printf("Hello World!");
  return 0;
}
\end{lstlisting}

\end{document}

Is there a way to coulour the background of line numbers (in grey for example) but not the background of the code ?

Answer 1

listings doesn't have a predefined option for this, but if you are willing to use the tcolorbox package, which has a nice interaction with the listings package, here's how you can do it:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[many]{tcolorbox}
\tcbuselibrary{listings}

\newtcblisting{mycpp}{
  colback=white,
  boxrule=0pt,
  arc=0pt,
  outer arc=0pt,
  top=0pt,
  bottom=0pt,
  colframe=white,
  listing only,
  left=15.5pt,
  enhanced,
  listing options={
    basicstyle=\small\ttfamily,
    keywordstyle=\color{blue},
    language=C++,
    showstringspaces=false,
    tabsize=2,
    numbers=left
  },
  overlay={
    \fill[gray!30] 
      ([xshift=-3pt]frame.south west)
      rectangle 
      ([xshift=11.5pt]frame.north west);
  }
}

\begin{document}

\begin{mycpp}
#include <stdio.h>
int main(void) {
  printf("Hello World!");
  return 0;
}
int main(void) {
  printf("Hello World!");
  return 0;
}
int main(void) {
  printf("Hello World!");
  return 0;
}
\end{mycpp}

\end{document}

Answer 2

Another way would be to work with frames and their margins so you can use the normal lstlisting command.

\lstset {
...
frame=l,
framesep=4.5mm,
framexleftmargin=2.5mm,
fillcolor=\color{numberbg},
rulecolor=\color{ballblue},
numberstyle=\normalfont\tiny\color{numbercolor}
}

This snippet will result in following style: