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?

Kincardine

In the future, please ask LaTeX-related questions at: tex.stackexchange.com. – Whaleback

@IoannisFilippidis That would have been useful to know... 8 years ago. – Kincardine

There is a package called lstlinebgrd that does this, the only caveat is that it does not read the length of the texts automatically. – Shall

This uses overlays to highlight chunks of a listing. – Cid

Answer 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}

Jegger

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? – Jackpot

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

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

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. – Tamathatamaulipas

Answer 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}

Oscillograph

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

@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. – Oscillograph

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. – Oscillograph

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

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

lstlisting doesnot work with TexLive 2021 – Kirakiran

Answer 3

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.

Shall

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

@Kucik Thanks for the information, hope it will recover soon! – Shall

Answer 4

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.

Venom

Answer 5

the listings package provides backgroundcolor=\color{} as an option, but i'm sure that makes the whole BG color, not a chunk.

you could have a look at putting it a parbox with color, or the colorbox package.

Deciare