acronyms lead to unexpected behavior of onslide

[fmirus]

Using acronyms in beamer in combination with overlays (such as onslide) leads to the following unexpected behavior: having two items in one frame being uncovered sequentially using onslide, I would expect the first item to remain on the same position in both slides. However, if the second item contains an acronym, which is used for the first time, the first occurrence of the acronym is invisible and thus beamer used this invisible version for the first item to save space. However, if the second item is uncovered, it only uses the short version of the acronym (since the first occurrence was when it was still invisible) and thus the position of the first item changes. Here is a minimal working example (using \setbeamercovered{transparent} to make the actual problem visible):

\documentclass{beamer}
\usepackage[acronym, toc, shortcuts, nowarn]{glossaries}
\setacronymstyle{short-long}
\newacronym{VLA}{VLA}{Very Loooooooong Acronym}
\setbeamercovered{transparent}
\begin{document}
 \begin{frame}
    \frametitle{Minimal working example}
    \onslide<1->{Some text without acronym.}
    \onslide<2->{Some more text with \ac{VLA}.}
\end{frame}

\end{document}

First slide:

Second slide:

Not sure, if this is even a bug in beamer or intended behaviour. It is also quite simple to resolve the issue by replacing \ac{VLA} by \acf{VLA}. However, I just wanted to point it out since it took me quite some time to figure out what went wrong in my presentation and others might have the same problem :wink:

[dbitouze]

glossaries's documentation provides workarounds pages 202-203.