Carter N. wrote, on Tue, 10 Nov 2009 15:41:50 -0000:

Dear Mr Moses and Mr Tantau,

First of all, /many/ thanks for the time and effort you have put into
your truly excellent packages, which I gratefully use on a daily basis
to teach programming to our students.

Unfortunately, I have found what appears to be a bug (or just a normal
behaviour that is beyond my level of LaTeX knowledge!): tab symbols are
not displayed in Beamer mode, even when showtabs is set to true.

At the bottom of this message, you will find a small document that
demonstrates the problem (I trust that my email client will not
interfere with the spaces and tabs). If you change the document class to
"article" and remove the frame's begin-end pair, the problem goes away,
but no amount of my reading your (also excellent) documentation has
enabled me to resolve the problem for beamer mode.

Perhaps you could advise?

Yours sincerely,

Neil.

\documentclass{beamer}
\usepackage{listings}
\lstset{
showspaces=true,
showtabs=false,
tabsize=4,
tab=\rightarrowfill
}
\begin{document}

\begin{frame}[fragile]{Test}

spaces on, tabs off:

\begin{lstlisting}
Sp: a b c
Tb: 1 2 3
\end{lstlisting}

spaces off, tabs on:

\lstset{showspaces=false,showtabs=true}

\begin{lstlisting}
Sp: a b c
Tb: 1 2 3
\end{lstlisting}

\end{frame}
\end{document}