How to make custom command work after line break/new paragraph?

Question

I have a simple command which creates coloured text. This works without any issues when there is a single paragraph without a line break. With a linebreak/new paragraph this does not work (commented code in MWE below produces this). The error that is given is

Too many }'s.
\tbn #1->\textcolor {blue}{{#1} }

A simple method is to use \tbn{} separately for each paragraph after line break. But can the command be redefined so that it works across paragraphs/line breaks?

\documentclass{article}
\usepackage{xcolor}
\newcommand{\tbn}[1]{\textcolor{blue}{{#1}}}
\usepackage{lipsum}
\begin{document}
\tbn{This works if there is no line break.}
% \tbn{This doesn't work if there is a line break.
% If there is a line break.}
\end{document}

Skillmon · Accepted Answer · 2024-03-03T13:15:42.497

4

\textcolor doesn't accept paragraphs in its argument (just like all the other \text... commands like \textbf). Instead use an explicit group and \color:

\documentclass{article}
\usepackage{xcolor}
\newcommand{\tbn}[1]{\leavevmode{\color{blue}#1}}
\begin{document}
\tbn{This works if there is no line break.}
\tbn{This doesn't work if there is a line break.
If there is a line break.}
\end{document}

edited Mar 03 '24 at 13:15

answered Mar 03 '24 at 08:42

Skillmon

60,462

3

I would perhaps add a leavevmode – Ulrike Fischer Mar 03 '24 at 08:55
2

I would delete the "perhaps" from Ulrike's comment – David Carlisle Mar 03 '24 at 09:16
Could you perhaps explain why leavevmode is needed? – Damitr Mar 03 '24 at 11:52
@Damitr Because colour support isn't really built into TeX but added by using \special which outputs a whatsit that might have side effects if used in the wrong place, the \leavevmode reduces the risk of strange things. – Skillmon Mar 03 '24 at 13:45
1

@Damitr for a better explanation take a look here: https://tex.stackexchange.com/a/47053/117050 – Skillmon Mar 03 '24 at 13:50

How to make custom command work after line break/new paragraph?

1 Answers1