Linespacing only for main text body

Question

In a LaTeX beamer document, is there a way to change line spacing only for the main text body - i.e. for everything between \begin{frame} and \end{frame}? In particular if using \linespread and its variants in the preamble the line spacing will also increase in multi-line titles or if the respective beamertheme uses newlines in its layout. I also tried using \linespread within a frame but to no avail.

Answer 1

If you have a title on each frame, your generic structure would probably resemble

\begin{frame}
  \frametitle{<title>}
  % <frame content>
\end{frame}

As such, you have the \frametitle command as a hook that you can use to initiate a different line spacing for the remainder of the frame. And, instead of using the traditional \linespread{<factor>} to modify the spacing, use \setstretch{<factor>} from the setspace package. To that end, include the following in your preamble:

\usepackage{setspace}% http://ctan.org/pkg/setspace
\let\oldframetitle\frametitle% Store \frametitle in \oldframetitle
\renewcommand{\frametitle}[1]{%
  \oldframetitle{#1}\setstretch{2}}

This will typeset the regular \frametitle and immediately after it call \setstretch{2} which increases ("doubles") the line spacing for the remainder of the group. Since the frame environment provides the necessary scope boundary, \setstretch only has an effect until \end{frame}. This allows for only the frame content to be typeset under a different line spacing, leaving titles untouched in terms of this stretch factor. Additionally, a natural form of automation by redefinition of the existing commands allow for legible and transferable code.

Here's a minimal example showing this:

\documentclass{beamer}% http://ctan.org/pkg/beamer
\useoutertheme{infolines}
\usetheme{Warsaw}
\usepackage{lipsum}% http://ctan.org/pkg/lipsum
\usepackage{setspace}% http://ctan.org/pkg/setspace
\let\oldframetitle\frametitle% Store old \frametitle in \oldframetitle
\renewcommand{\frametitle}[1]{% Redefine \frametitle
  \oldframetitle{#1}\setstretch{2}}
%\setstretch{2} <--- uncomment to see the global effect of \setstretch{2}
\title{Random title}
\subtitle{Random subtitle}
\author{Random Randofsky}
\institute{Random institute, Random City 1000, Randomia}
\date{\today}

\begin{document}
\maketitle

\begin{frame}
  \tableofcontents
\end{frame}

\section{Random section 1}
\begin{frame}
  \frametitle{This frame title is extremely long and spans at least two lines}
  \begin{itemize}
    \item Random stuff Random stuff
    \item \itshape{more random stuff}
    \item Random stuff...
  \end{itemize}
\end{frame}

\section{Random section 2}
\begin{frame}
  \frametitle{Here is another long frame title - this time it spans more than 
    just two lines of the frame; it actually spans three lines}
  \lipsum[4]
\end{frame}

\section{Random section 3}
\begin{frame}
  This frame has no title. So, the contents is not affected by line spacing changes
  \begin{itemize}
    \item Random stuff Random stuff
    \item \itshape{more random stuff}
    \item Random stuff...
  \end{itemize}
\end{frame}


\section{Random section 4}
\begin{frame}
  \frametitle{About this frame}
  \begin{itemize}
    \item Random stuff Random stuff
    \item \itshape{more random stuff}
    \item Random stuff...
  \end{itemize}
\end{frame}

\end{document}

Of course, this relies on the fact that your frame has the structure suggested at the start. So, a frame without a title would be void of any line spacing alterations. Since you didn't mention this in your question, I assume this is not a problem. However, such modifications are always possible, given an alternative/suitable hook.

The lipsum package was merely used to provide filler text on slide 4.

^{To see the global effect of \setspace{2} on the frame titles, uncomment \setspace{2} in the preamble.}