Always* insert a fixed slide after the title slide

Question

I'm implementing my institution's PP templates -- like so many others. At our organisation we're often presenting classified stuff and we're supposed to include a slide with information about classification and remind people to take their electronics out of the room.

Ideally, the user shouldn't have to remember to include this slide by herself: If beamer is told that that the presentation contains classified information, then it should automatically insert this slide after the title page. For now, let's just assume there exists a boolean classified.

As a workaround, I could do it as a transition on the title page template. However, that would look very strange when printing.

It feels like this question is related to Theme with a different footline for the titlepage (in principle, insert some stuff before and after should be equivalent?), but I haven't been able to proceed.

There is no MWE, as I don't even know where to begin. As such, I'm happy to just get pointers in the right direction, and I'll make sure to post a working result at the end.

Answer 1

You could put the title page and a conditional 'Classified' frame in a style file. The frames can be inserted using the AfterEndPreamble hook from the etoolbox package, which is executed at the end of the \begin{document} command.

MWE, iooci.sty:

\usepackage{etoolbox}
\newif\ifclassified
\classifiedtrue   % set boolean to true by default
\institute{Institute of Often Classified Information}   % default institute and logo
\logo{\fbox{\Huge IoOCI}}
\AfterEndPreamble{
{%
\beamertemplatenavigationsymbolsempty % switch off navigation symbols 
\setbeamertemplate{logo}{}            % and logo for first two slides
\begin{frame}
\maketitle
\end{frame}
\ifclassified   % show slide only if boolean is true
\begin{frame}{Classified}
This presentation is classified
\end{frame}
\fi % end if
}   % end scope of switching off navigation and logo
}

Document with extra slide:

\documentclass{beamer}
\usepackage{iooci}
\author{John Smith}
\date{\today}
\begin{document}
\begin{frame}{First real slide}
\end{frame}
\end{document}

And without:

\documentclass{beamer}
\usepackage{iooci}
\author{John Smith}
\date{\today}
\classifiedfalse
\begin{document}
\begin{frame}{First real slide}
\end{frame}
\end{document}

Result (with extra slide):

Answer 2

I finally opted to use a variation of @Fran's suggestion in the comments above. A justification to future people like me follows below. In the style of @Marijn's code:

iooci.sty

\usepackage{etoolbox}

\institute{Institute of Often Classified Information}   % default institute and logo
\logo{\fbox{\Huge IoOCI}}

\setbeamertemplate{classificationframe}{%
  \begin{frame}
    \frametitle{Classified}
    This presentation is classified
  \end{frame}
}

Document

\documentclass{beamer}

\usepackage{iooci}
\author{John Smith}
\date{\today}
\begin{document}

\begin{frame}
    \maketitle
\end{frame}

\usebeamertemplate{classificationframe}

\begin{frame}{First real slide}
\end{frame}
\end{document}

---

Why not anything more fancy? I figured I had to tell the user how to do stuff nonetheless, so I opted for the most straight-forward solution.

Along the way, I explored using [allowframebreaks] (see Beamer allowframebreaks default option), but if I redefined the frame to allow me to put the classification info on the title page template, it could potentially break how the user expected new frames to work, including \frame{\titlepage} and frames with [fragile].

Fran and Marijn, thanks for taking the time to answer a vague question. It helped me explore my possibilities.

Any better solutions than the one I ended up with are obviously still welcome.