TL:DR: Is there a solution to fake overlay with mutiple frames?
As explained here I would like to add multiple backgrounds to a same set of overlays. This thread gives a few solutions, but none of them is perfect: the first solution adds some margin, so one need to arbitrary increase the background until no margin is visible which may zoom a bit the background image, and the second solution seems better, but it adds new pages. Basically, this second solution adds some frames by adding new pages via:
\setbeamertemplate{background}{...}
\againframe<2>{myframelabel}
but unfortunately this adds new pages instead of overlays:
I managed to solve the page numbering problem by using some \addtocounter{framenumber}{-1}, but unfortunately the miniframes (the dots in the top left part) are still bad...
Is there a solution to fake overlay with mutiple frames?
MWE:
\documentclass{beamer}
\useoutertheme[footline=institutetitle,subsection=false]{miniframes}
\usecolortheme{beaver}
\setbeamercolor{separation line}{use=structure,bg=darkred!80!black}
\makeatletter
\setbeamertemplate{footline}
{%
% \begin{beamercolorbox}[colsep=1.5pt]{upper separation line foot}
% \end{beamercolorbox}
\hbox{%
\begin{beamercolorbox}[wd=0.1\paperwidth, ht=2.5ex, dp=1.125ex, left]{title in head/foot}%
\hspace{4ex}
\usebeamerfont{author in head/foot}\insertshortauthor~~\beamer@ifempty{%
%\insertshortinstitute
}{}{}
\end{beamercolorbox}%
\begin{beamercolorbox}[wd=0.8\paperwidth, ht=2.5ex, dp=1.125ex, center]{title in head/foot}%
\usebeamerfont{title in head/foot}\insertshorttitle
\end{beamercolorbox}%
\begin{beamercolorbox}[wd=0.1\paperwidth, ht=2.5ex, dp=1.125ex, right]{title in head/foot}%
\usebeamerfont{title in head/foot}\insertframenumber/\inserttotalframenumber\hspace{4ex}
\end{beamercolorbox}}
}
\makeatother
\begin{document}
\section{test}
{
\setbeamertemplate{background}{\includegraphics[height=\paperheight,width=\paperwidth]{example-image-a}}
\begin{frame}<1>[label=myframelabel]
\begin{itemize}
\item<+-> a
\item<+-> b
\item<+-> c
\item<+-> d
\item<+-> e
\end{itemize}
\end{frame}
\setbeamertemplate{background}{\includegraphics[height=\paperheight,width=\paperwidth]{example-image-b}}
\addtocounter{framenumber}{-1}\againframe<2>{myframelabel}
\setbeamertemplate{background}{\includegraphics[height=\paperheight,width=\paperwidth]{example-image-c}}
\addtocounter{framenumber}{-1}\againframe<3>{myframelabel}
\setbeamertemplate{background}{\includegraphics[height=\paperheight,width=\paperwidth]{example-image-a}}
\addtocounter{framenumber}{-1}\againframe<4->{myframelabel}
}
\begin{frame}
Hello, I'm a new empty frame
\end{frame}
\end{document}
-- EDIT --
I finally found a problem to my original problem here, so I don't need anymore to solve that one, but of course I'm still curious to ear about answers.
