[Tex/LaTex] \bgroup and \egroup

environmentsformattinggroupinghorizontal alignment

So I've been looking to expand on the following bit of code (a hack to not screw up the margins when using oversized figures):

\noindent\makebox[\textwidth]{%
\begin{tabularx}{1.5\textwidth}{XX}
  \blindtext & \blindtext
\end{tabularx}
}

I wanted to turn this into an environment, so was thinking of doing the following:

\newenvironment{figurehack}{\noindent\makebox[\textwidth]\bgroup}{\egroup}

This throws a strop, LaTeX decides to insert the "missing" brace. So to see if this was a newenvironment quirk, I tried the following bit of code:

\noindent\makebox[\textwidth]\bgroup%
\begin{tabularx}{1.5\textwidth}{XX}
  \blindtext & \blindtext
\end{tabularx}
\egroup

LaTeX once again tries to insert the "missing" brace. Any suggestions how I can resolve this?

Best Answer

You can only use \bgroup and \egroup as a replacement for { and } if LaTeX is expanding the content like it does for low-level boxing commands, but not when it is looking for an macro argument. The \makebox macro reads the content as argument not as box, so your attempt doesn't work. I wrote the realboxes package which provides variants of all \...box macros which read the content as real boxes using my other package collectbox. Simply load realboxes and use \Makebox instead:

\newenvironment{figurehack}{\noindent\Makebox[\textwidth]\bgroup}{\egroup}

Also have a look on my adjustbox package which provides an \adjustbox macro and adjustbox environment. It also allows \bgroup/\egroup and provides many options which can be easily combined. A \makebox[\textwidth] (which by default centers the content) can be done using \adjustbox{center=\textwidth}. The \textwidth is already the default value, so \adjustbox{center} would be enough.

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