Centering something that is scaled to fit an empty beamer slide

Question

I am trying to fit something in a beamer slide so that it covers the entire frame width, but what I get seems to be offset to the right by \hoffset. Here is a MWE:

\documentclass{beamer}

\usepackage{adjustbox}

% No navigation symbols. %
\setbeamertemplate{navigation symbols}{}

\begin{document}

\begin{frame}[plain]
%
\centering
%
\begin{adjustbox}{%
  max totalsize={\paperwidth}%
                {\dimexpr\paperheight-\voffset\relax}}
%
% Something larger than paperwidth, so that scaling is necessary.
\adjustbox{width=1.2\paperwidth}{Test text.}
%
\end{adjustbox}
%
\end{frame}

\end{document}

The above produces the following:

As can be seen, there is some empty space on the left. Moreover, the contents don't really seem to actually have a width of \paperwidth.

What is the right way of achieving this? I would like to avoid playing around with \usebackgroundtemplate, as something like Image on full slide in beamer package seems very ad-hoc to me.

Answer 1

With the current version of adjustbox just add the center key at the very end. There is also no need to use \dimexpr anymore. This has been fixed.

\documentclass{beamer}

\usepackage{adjustbox}

% No navigation symbols. %
\setbeamertemplate{navigation symbols}{}

\begin{document}

\begin{frame}[plain]
%
\centering
%
\begin{adjustbox}{%
  max totalsize={\paperwidth}{\paperheight-\voffset}, center}
%
% Something larger than paperwidth, so that scaling is necessary.
\adjustbox{width=1.2\paperwidth}{Test text.}
%
\end{adjustbox}
%
\end{frame}

\end{document}

Answer 2

TeX doesn't centre stuff which is wider than the text width. In that case it always starts at the left margin. To fix this, change the width that the typesetting algorithm sees to something which fits into the width with \makebox:

\documentclass{beamer}

\usepackage{adjustbox}

% No navigation symbols. %
\setbeamertemplate{navigation symbols}{}

\begin{document}

\begin{frame}[plain]
%
\centering
%
\makebox[\textwidth]{%
\begin{adjustbox}{%
  max totalsize={\paperwidth}%
                {\dimexpr\paperheight-\voffset\relax}}%
%
% Something larger than paperwidth, so that scaling is necessary.
\adjustbox{width=1.2\paperwidth}{Test text.}%
%
\end{adjustbox}%
}%
\end{frame}

\end{document}