Odd spacing effect of \small in blocks

[josephwright]

In a mail from @frankmittelbach

\documentclass{beamer}

\usetheme{PaloAlto}     % more visible this way but not needed

\begin{document}

\begin{frame}{Frame normal}
  \begin{block}{X}
    \begin{itemize}
    \item first item
    \item second item
    \end{itemize}
  \end{block}
\end{frame}

\begin{frame}{Frame small (or not)}
  \begin{block}{X}
    \small
    \begin{itemize}
    \item first item      % extra spacing above (and below?)
    \item second item
    \end{itemize}
  \end{block}
\end{frame}

\end{document}

[louisstuart96]

This might be a "whatsit in vertical mode" problem? I have not checked it yet.

[louisstuart96]

@josephwright The \parsep glue in \@listi is set to zero globally by beamer, but \small command in size11.clo resets \parsep to a non-zero glue.

[louisstuart96]

We may alter the the size settings and dump them to sepearte files like beamersize11.clo. This also helps to fix #506. (And the extsize package will not be required at all.)

[josephwright]

@louisstuart96 Don't we just need to patch \@listi after the loading line? We can just add \parsep \z@ onto the end of it

\edef\@listi{\unexpanded\expandafter{\@listi}\parsep\z@}

[louisstuart96]

@josephwright If so, the commands \small and \footnotesize need to be patched since they redefine the whole \@listi command.

Moreover, the glues are a little bit different among these font size options in the standard classes, but beamer use the same glues for all sizes. Another issue is that the default glue settings for article classes might be too large for beamer's small page size.