With newenvironment for font an Overfull\hbox warning is shown within itemize [duplicate]

Question

When I run the following code I get an Overfull\hbox(... too wide) in paragraph warning.

\documentclass{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\newenvironment{fonttfp}{\fontfamily{cmtt}\selectfont}{\par}

\begin{document}
\begin{itemize}
  \item[] {\fonttfp Afghanistan\_Albania Algeria\_Andorra Angola\_Antigua and Barbuda\_Argentina Armenia\_Australia Austria\_Azerbaijan}
\end{itemize}
\end{document}

How can I get it away. When I remove the \fonttfp statement the warning disappears. I've also tried to use sloppypar and the package microtype. Both approaches do not clear the warning.

Answer 1

Version No. 1

You could do it as you would when using an environment with \fonttfp ... \endfonttfp, what would give you this:

\documentclass{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\newenvironment{fonttfp}{\fontfamily{cmtt}\selectfont}{\par}

\begin{document}
\begin{itemize}
  \item[] {\fonttfp Afghanistan Albania Algeria Andorra Angola Antigua and Barbuda Argentina Armenia Australia Austria Azerbaijan \endfonttfp}
\end{itemize}
\end{document}

Version No. 2

You could do it the LaTeX way (\begin{fonttfp}...\end{fonttfp}):

\documentclass{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\newenvironment{fonttfp}{\fontfamily{cmtt}\selectfont}{\par}

\begin{document}
\begin{itemize}
  \item[] \begin{fonttfp}Afghanistan Albania Algeria Andorra Angola Antigua and Barbuda Argentina Armenia Australia Austria Azerbaijan\end{fonttfp}
\end{itemize}
\end{document}

Version No. 3

Use a command.

\documentclass{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\newcommand{\fonttfp}[1]{\begingroup\fontfamily{cmtt}\selectfont#1\endgroup\par}

\begin{document}
\begin{itemize}
  \item[] \fonttfp{Afghanistan Albania Algeria Andorra Angola Antigua and Barbuda Argentina Armenia Australia Austria Azerbaijan}
\end{itemize}
\end{document}

Version No. 4

Do the same as in (3), but without argument and add \par manually.

Answer 2

It's not \newenvironment, but \newcommand.

You can set \spaceskip with some flexibility:

\documentclass{scrartcl}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}

\newcommand{\fonttfp}{%
  \fontfamily{cmtt}\selectfont % better \ttfamily
  \spaceskip=.3em plus 0.2em minus .1em
}
\DeclareTextFontCommand{\texttfp}{\fonttfp}

\begin{document}

\begin{itemize}
\item[] {\fonttfp Afghanistan Albania Algeria Andorra Angola Antigua and
         Barbuda Argentina Armenia Australia Austria Azerbaijan}
\item[] \texttfp{Afghanistan Albania Algeria Andorra Angola Antigua and
          Barbuda Argentina Armenia Australia Austria Azerbaijan}
\end{itemize}

\end{document}