In the figure form, adjust the whole size of “text” and “math” format at once (II): from \twocolumngrid to \onecolumngrid

Question

This follows from a previous post In the figure form, how to adjust the whole size of "text" and "math" format at once?,

In the figure form, how to adjust the whole size of "text" and "math" format "as a combined figure" at once, from the \twocolumngrid to \onecolumngrid? (say in the revtex)

My trouble is that in the "twocolumn" format of revtex4-1, if I use the following method @Herbert,

\documentclass[aps,prl,twocolumn,superscriptaddress,floatfix,letterpaper,nofootinbib]{revtex4-1}
\usepackage{mathtools,amssymb,varwidth}
\usepackage{showframe}


\begin{document}


\onecolumngrid
\begin{widetext}

\begin{figure}[!h]
\centering
\begin{center}
\resizebox{\linewidth}{!}{%
  \begin{varwidth}{\linewidth}
\begin{gather*}
 \overbrace{\underbrace{A \times B}_E\times
               \underbrace{C\times {D}}_{EFG}}^{\text{ABCDEFG}}\\[-\normalbaselineskip]
    \underbrace{\hphantom{A\times B\times C\times D}}_{\text{family}}
   \end{gather*}
  \end{varwidth}}
 \end{center}
  \caption{}
\end{figure}
\end{widetext}
\twocolumngrid

\end{document}

I got:

This is not what I wanted. I want to have the figure stand in the middle, with adjustable size (likely 2/3 or 3/4 of the document width).

However, the "\begin{gather*} \end{gather*}" seems to make the trouble.

If I remove "\begin{gather*} ... \end{gather*}" to simply use "$...$", I got a compilation problem and a troublesome output, where the "braces" are making troubles in the wrong position:

PS. My last figure is what I am hoping to get (with tunable size, like 2/3 or 3/4 of the whole document width). But it shall also be scale-invariant as the same smaller one as the one in my first figure. The code should be also compilable.

Edit 1: This seems to cause the trouble \\[-\normalbaselineskip], which outputs "LaTeX Error: There's no line here to end."

My following attempt can not be compiled fully:

\documentclass[aps,prl,twocolumn,superscriptaddress,floatfix,letterpaper,nofootinbib]{revtex4-1}
\usepackage{mathtools,amssymb,varwidth}
\usepackage{showframe}


\begin{document}


\onecolumngrid
\begin{widetext}

\begin{figure}[!h]
\centering
\begin{center}
\resizebox{\linewidth}{!}{%
  \begin{varwidth}{\linewidth}
$
\overbrace{\underbrace{A \times B}_E\times
               \underbrace{C\times {D}}_{EFG}}^{\text{ABCDEFG}}\\[-\normalbaselineskip]
    \underbrace{\hphantom{A\times B\times C\times D}}_{\text{family}}
$  \end{varwidth}}
 \end{center}
  \caption{}
\end{figure}
\end{widetext}
\twocolumngrid

\end{document}

Answer 1

Since displayed math uses the entire width of the column, varwidth won't help. Instead you need to measure the width seperately and use a normal minipage.

Note the the actual width of the underbrace is slightly larger than its measured width. One gets the same result using \sbox0{$\displaystyle A\times B\times C\times D$}%.

\documentclass[aps,prl,twocolumn,superscriptaddress,floatfix,letterpaper,nofootinbib]{revtex4-1}
\usepackage{mathtools,amssymb,varwidth}
\usepackage{showframe}


\begin{document}


\onecolumngrid
\begin{widetext}

\begin{figure}[htp]% I have yet to find a case where ! makes any difference whatsoever
\centering
\sbox0{$\displaystyle \underbrace{\hphantom{A\times B\times C\times D}}_\text{family}$}% measure width
\resizebox{\linewidth}{!}{\begin{minipage}{\wd0}
  \begin{gather*}
    \overbrace{\underbrace{A \times B}_E\times
               \underbrace{C\times {D}}_{EFG}}^{\text{ABCDEFG}}\\[-\normalbaselineskip]
    \underbrace{\hphantom{A\times B\times C\times D}}_{\text{family}}
  \end{gather*}
  \end{minipage}}
  \caption{}
\end{figure}
\end{widetext}
\twocolumngrid

\end{document}