Use shapepar for beamer titlepage

Question

Looking for a solution to avoid arithmetic error while trying to get tikz and shapepar working together.

\documentclass{beamer}
\usepackage{tikz,shapepar}

\setbeamertemplate{title page}{%
\begin{tikzpicture}[remember picture,overlay]
%\node[circle,fill=black,text=white] {\shapepar{\circleshape} \inserttitle\par}; % <- not working
\end{tikzpicture}}

\title{Some title with variable length}
\begin{document}
\maketitle

\begin{frame}
\shapepar{\circleshape} \huge\inserttitle % <- working fine here
\end{frame}
\end{document}

According to David, this should be the syntax: \node[shape=circle,text width=0cm, fill=black,text=white] {\shapepar{\circleshape} \inserttitle\par};, with text width=0cm so that the node scales with the content. Anyhow, depending on the length of \inserttitle, I still encounter arithmetic overflow.

Answer 1

a node is an \hbox and can't have paragraph things unless you specify either text width or align=<...> keys (when it becomes a minipage environment)

\documentclass{beamer}
\usepackage{tikz,shapepar}

\setbeamertemplate{title page}{%
\begin{tikzpicture}[remember picture,overlay]
\node[text width=6cm, fill=black,text=white] {\shapepar{\circleshape} \inserttitle\par}; % <- not working
\end{tikzpicture}}

\title{Some title with variable length}
\begin{document}
\maketitle

\begin{frame}
\shapepar{\circleshape} \huge\inserttitle % <- working fine here
\end{frame}
\end{document}

or a version with a long title and the division operator modified so it never overflows (just returns \maxdimen

\documentclass{beamer}
\usepackage{tikz,shapepar}
\makeatletter
\def\fpdivide#1#2{%
\@tempcntb #2\relax
\multiply\@tempcntb10
#1=\dimexpr(#1*\p@ /\@tempcntb) \relax
\ifdim#1>0.1\maxdimen
#1=\maxdimen
\else
\multiply#1 by 10
\fi
}

\makeatother

\setbeamertemplate{title page}{%
\begin{tikzpicture}[remember picture,overlay]
\node[text width=8cm, fill=black,text=white] {\shapepar{\circleshape} \inserttitle\par}; % <- not working
\end{tikzpicture}}

\title{Some title with variable length
x x x x x x x x x x x
very very long
very very long
very very long
very very long
very very long
}
\begin{document}


\maketitle

\begin{frame}
\shapepar{\circleshape} \huge\inserttitle % <- working fine here
\end{frame}
\end{document}