[Tex/LaTex] Justify text inside itemize environment with beamer class

Question

I would like to justify text inside an itemize environment with the beamer class. Text appears to be justified by default with the article class, but not with the beamer class.

The following code justifies text left and right:

    \documentclass{article}
    \usepackage{lipsum}
    \begin{document}
    \begin{itemize}
    \item \lipsum[1-1]
    \end{itemize}
    \end{document}

The following code does not:

    \documentclass{beamer}
    \usepackage{lipsum}
    \begin{document}
    \begin{frame}
    \begin{itemize}
    \item \lipsum[1-1]
    \end{itemize}
    \end{frame}
    \end{document}

I have tried this:

    \documentclass{beamer}
    \usepackage{ragged2e}
    \usepackage{lipsum}
    \let\olditemize=\itemize 
    \renewenvironment{itemize}{\olditemize\justify}{\endlist} 
    \begin{document}
    \begin{frame}
    \begin{itemize}
    \item \lipsum[1-1]
    \end{itemize}
    \end{frame}
    \end{document}

but it won't justify text on the right. Any suggestions welcome!

Answer 1

beamer has its own ways and, in particular, it redefines many standard LaTeX environments/commands; in particular, it redefines the basic list-like environments itemize, enumerate and description.

Here's, for example, the definition of \itemize as given in beamerbaselocalstructure.sty:

\renewcommand{\itemize}[1][]{%
  \beamer@ifempty{#1}{}{\def\beamer@defaultospec{#1}}%
  \ifnum \@itemdepth >2\relax\@toodeep\else
    \advance\@itemdepth\@ne
    \beamer@computepref\@itemdepth% sets \beameritemnestingprefix
    \usebeamerfont{itemize/enumerate \beameritemnestingprefix body}%
    \usebeamercolor[fg]{itemize/enumerate \beameritemnestingprefix body}%
    \usebeamertemplate{itemize/enumerate \beameritemnestingprefix body begin}%
    \list
      {\usebeamertemplate{itemize \beameritemnestingprefix item}}
      {\def\makelabel##1{%
          {%
            \hss\llap{{%
                \usebeamerfont*{itemize \beameritemnestingprefix item}%
                \usebeamercolor[fg]{itemize \beameritemnestingprefix item}##1}}%
          }%
        }%
      }
  \fi%
  \beamer@cramped%
  \raggedright% 
  \beamer@firstlineitemizeunskip%
}

as you can see, \itemize internally uses \raggedright. The best approach to keep things overlay specification-aware is to redefine \itemize to use \justifying (from the ragged2e package) instead; the following code shows this redefinition in an actual document:

\documentclass{beamer}
\usepackage{ragged2e}
\usepackage{lipsum}

\makeatletter
\renewcommand{\itemize}[1][]{%
  \beamer@ifempty{#1}{}{\def\beamer@defaultospec{#1}}%
  \ifnum \@itemdepth >2\relax\@toodeep\else
    \advance\@itemdepth\@ne
    \beamer@computepref\@itemdepth% sets \beameritemnestingprefix
    \usebeamerfont{itemize/enumerate \beameritemnestingprefix body}%
    \usebeamercolor[fg]{itemize/enumerate \beameritemnestingprefix body}%
    \usebeamertemplate{itemize/enumerate \beameritemnestingprefix body begin}%
    \list
      {\usebeamertemplate{itemize \beameritemnestingprefix item}}
      {\def\makelabel##1{%
          {%
            \hss\llap{{%
                \usebeamerfont*{itemize \beameritemnestingprefix item}%
                \usebeamercolor[fg]{itemize \beameritemnestingprefix item}##1}}%
          }%
        }%
      }
  \fi%
  \beamer@cramped%
  \justifying% NEW
  %\raggedright% ORIGINAL
  \beamer@firstlineitemizeunskip%
}
\makeatother

\begin{document}

\begin{frame}
\begin{itemize}
\item<1->\lipsum[2]
\item<2>\lipsum[2]
\end{itemize}
\end{frame}

\end{document}

The output:

As a final note, I would suggest you to consider if this redefinition is really needed at all; frames with too much text (like the one I just build for the example) are to be avoided in a presentation.