Highlighting a Chunk of Code within a lstlisting

Question

I have a bunch of code in a lstlisting environment. How can I highlight (color background) just a particular chunk of code within the environment?

Solution 1

You can use \colorbox and an escape character inside your listing:

Add to your preamble

  \usepackage{color}

  \definecolor{light-gray}{gray}{0.80}

then use it like this in your document:

  \begin{lstlisting}[escapechar=!]
  def mult(m: Matrix[Int], n: Matrix[Int]) {
    val p = !\colorbox{light-gray}{new MatrixInt}!(m.rows, n.cols)
  }
  \end{lstlisting}

Solution 2

It's a bit cumbersome, but you can break the code into several lstlisting environments.

\begin{lstlisting}
line
\end{lstlisting}
\vspace{-\baselineskip}
\begin{lstlisting}[backgroundcolor=\color{pink}]
very
interesting
\end{lstlisting}
\vspace{-\baselineskip}
\begin{lstlisting}
line
line
\end{lstlisting}

Solution 3

Here's a solution for highlighting (parts of) individual lines using tikz:

\documentclass[pdftex,11pt,a4paper]{article}

\usepackage{listings}

\usepackage{tikz}
\usetikzlibrary{tikzmark}

% Command to place a TikZ anchor at the current position
\newcommand{\mytikzmark}[1]{%
  \tikz[overlay,remember picture,baseline] \coordinate (#1) at (0,0) {};}

\newcommand{\highlight}[2]{%
  \draw[yellow,line width=14pt,opacity=0.3]%
    ([yshift=4pt]#1) -- ([yshift=4pt]#2);%
}

\begin{document}
    \begin{lstlisting}[escapechar=@, language=C]
@\mytikzmark{hl1Start}@struct@\mytikzmark{hl1End}@ S {
    double @\mytikzmark{hl2Start}@salary_@\mytikzmark{hl2End}@;
};
    \end{lstlisting}
        
    \begin{tikzpicture}[remember picture, overlay]
        \highlight{hl1Start}{hl1End}
        \highlight{hl2Start}{hl2End}
    \end{tikzpicture}   
        
\end{document}

and you get

so the lstlisting's syntax highlighting is retained.

Solution 4

There is a package called lstlinebgrd that does this

% !TEX encoding = UTF-8 Unicode
% !TEX TS-program = xelatex
\documentclass{article}
\usepackage[a4paper]{geometry}

\usepackage{lstlinebgrd}
\usepackage{listings, xcolor}
\lstset{tabsize = 4, showstringspaces = false, breaklines = true, numbers = left, numberstyle = \tiny, basicstyle = \small \ttfamily, keywordstyle = \color{blue}, stringstyle = \color{red}, commentstyle = \color{green}, rulecolor = \color{black}}

\begin{document}

\begin{lstlisting}[language = python, frame = tRBl, basicstyle = \ttfamily \scriptsize, linebackgroundcolor = {\ifnum \value{lstnumber} = 8 \color{yellow} \fi, \ifnum \value{lstnumber} = 10 \color{yellow} \fi, \ifnum \value{lstnumber} = 12 \color{yellow} \fi}, linebackgroundsep = 2.2 em, linebackgroundwidth = 15 em]
import numpy
from tensorflow.keras.layers import Dense, Activation, Dropout, Input
from tensorflow.keras.models import Sequential, Model, load_model
from tensorflow.keras.optimizers import Adam

model_input = Input(shape = x_train[0].shape)
x = Dense(120, activation = 'relu')(model_input)
x = Dropout(0.01)(x)
x = Dense(120, activation = 'relu')(x)
x = Dropout(0.01)(x)
x = Dense(120, activation = 'relu')(x)
x = Dropout(0.01)(x)
model_output = Dense(numpy.shape(y_train)[1])(x)
model = Model(model_input, model_output)
\end{lstlisting}

\end{document}

and you get

it is however, still not optimized, you have to manually adjust the left and right edge of highlight bar, and setting multiple lines to highlight is cumbersome.

View more solutions

Comments

[Edd]

Will this work if you've got, for example, line numbers, or will they get restarted?

[Anton Geraschenko]

@Edd: By default, they will get restarted, but you can use the firstnumber keyword to fix that. In this example, you'd use firstnumber=2 and firstnumber=4 in the second and third lstlisting environments, respectively. Using firstnumber=last is supposed to continue the numbering from the previous lstlisting environment, but when I try it, it's off by one.

[Anton Geraschenko]

It turns out there's an even better solution to the numbering problem: use the name keyword (eg \begin{lstlisting}[name=asdf, ...). The name doesn't get displayed, and lstlisting environments with the same name share a line counter by default.

[thequark]

I need something extra. I am using Beamer package for my presentation and I have to highlight code present in lstlisting. The difference in my need is I can't change the code inside lstlisting, like escaping or having special comment definition. The code is present inside a different file which can't be changed. Copying the code and making modifications is not an option as there are many of them. Can we indicate from outside (i.e. in \begin{lstlisting}) which lines to highlight?

[Julian]

Nice but it doesn't work with multiple lines and you are losing the syntax highlighting inside a colorbox.

[Julian]

this works with multiple lines and the syntax highlighting get preserved. Anyone knows if this can be encapsulated in a newcommand or newenvironment ?

[Gohu]

\vspace{-\baselineskip} didn't work for me to suppress separation between each block. Setting options aboveskip=0 and belowskip=0 as needed did.

[MKroehnert]

When using LaTeX Beamer I had to mark the frame as fragile with \begin{frame}[fragile] to make it work.

[Michael]

Works great! Anyway, somehow I got the error latex undefined color model when changing colors to \definecolor{light-green}{green}{0.80}. That's why I switched to \definecolor{lightgreen}{rgb}{0.8,1.0,0.8} instead. Hope it helps anyone.

[sepideha]

lstlisting doesnot work with TexLive 2021

[Supernormal]

This looks nice, although lstlinebgrd is currently broken tex.stackexchange.com/questions/451532/…

[zyy]

@Supernormal Thanks for the information, hope it will recover soon!