widetext.sty

example.tex

\documentclass[twocolumn]{article}
\usepackage{mwe}
\usepackage{widetext}
\begin{document}
\blindtext
\begin{widetext}
  \[
    E = mc^2.
  \]
\end{widetext}
\blindtext
\begin{widetext}
\begin{table}
\begin{center}
\caption{fake}
\begin{tabular}{cc}
  \hline
  fake & table \\
  \hline
\end{tabular}
\end{center}
\end{table}
\end{widetext}
\blindtext
\end{document}

widetext.sty

\NeedsTeXFormat{LaTeX2e}
\ProvidesPackage{widetext}

%% Mimics the widetext environment of revtex4 for any other class package
%% Eg: article.cls
%%
%% Authored by: Liam Huang
%%
%% Advantages:
%% *) Supports float (eg: figure) in two column format (Advantage over
%%      multicol package)
%% *) One and twocolumn exist on the same page
%% *) Flow of text shown via rule
%% *) Equal height of text when in two column format
%%
%% Acknowledgment(s):
%% 1. Instead of re-inventing the wheel, two packages (flushend, cuted) of
%% the sttools bundle are used. The sttools bundle is available from CTAN.
%% Lisence of these packages rests with their corresponding author.
%% Any bug/problem with flushend and cuted should be forwarded to their
%% corresponding package authors.
%% 2. The idea of the rule came from the following latex community website
%% http://www.latex-community.org/forum/viewtopic.php?f=5&t=2770
%%
%% This package just defines the widetext environment and the rules.
%%
%% Usage:
%% \documentclass[a4paper,12pt,twocolumn]{article}
%% \usepackage{widetext}
%%
%% \begin{document}
%%
%% Some text in twocolumn
%%
%% \begin{widetext}
%% Text in onecolumn format.
%% \end{widetext}
%%
%% Some more text in twocolumn
%%
%% \end{document}
%%%%%%%%%%%%%%%%%%%%

\newlength\wttlinewidth
\setlength{\wttlinewidth}{0.4pt}

\@ifpackageloaded{etoolbox}{\relax}{
  \IfFileExists{etoolbox.sty}
      {\RequirePackage{etoolbox}}
      {\typeout{}
      \typeout{Package widetext error: Install the etoolbox package. Available from CTAN.}
      \typeout{}
      \stop
      }
}

\AtBeginEnvironment{widetext}{%
  \renewenvironment{figure}[1][htb]%
  {%
    \let\oldcaption\caption
    \renewcommand\caption{\def\@captype{figure}\oldcaption}%
  }{}
  \renewenvironment{table}[1][htb]%
  {%
    \let\oldcaption\caption
    \renewcommand\caption{\def\@captype{table}\oldcaption}%
  }{}
}

\AtBeginDocument{%
  % Firstly, test which method of two-column document is being used
  \@ifpackageloaded{multicol} % test \ver@multicol.sty
  {
    \newlength\@parindent
    \setlength\@parindent{\parindent}
    \newenvironment{widetext}[1][2]{%
      \gdef\savedcolnum{#1}
      \noindent
      \rule{\dimexpr(0.5\textwidth-0.5\columnsep-0.4pt)}{\wttlinewidth}%
      \par %\vspace{6pt}
      \parindent \@parindent
    }{%
        \par
        \hfill
        \rule[0.5\baselineskip]
            {\dimexpr(0.5\textwidth-0.5\columnsep-1pt)}{\wttlinewidth}%
    }
    \BeforeBeginEnvironment{widetext}{\end{multicols}}
    \AfterEndEnvironment{widetext}{\begin{multicols}{\savedcolnum}}
  }{% if the multicol package is not used, test if LaTeX standard twocolumn is used
    \if@twocolumn
      \@ifpackageloaded{flushend}{\relax}{
        \IfFileExists{flushend.sty}
            {\RequirePackage{flushend}}
            {\typeout{}
            \typeout{Package widetext error: Install the flushend package. Available from CTAN.}
            \typeout{}
            \stop
            }
      }
      \@ifpackageloaded{cuted}{\relax}{
        \IfFileExists{cuted.sty}
            {\RequirePackage{cuted}}
            {\typeout{}
            \typeout{Package widetext error: Install the cuted package. Available from CTAN.}
            \typeout{}
            \stop
            }
      }
      \newlength\@parindent
      \setlength\@parindent{\parindent}
      \newenvironment{widetext}[1][2]
        {%
          \begin{strip}
          \rule{\dimexpr(0.5\textwidth-0.5\columnsep-0.4pt)}{\wttlinewidth}%
          \par %\vspace{6pt}
          \parindent \@parindent
        }%
        {%
          \par
          \hfill
          \rule[0.5\baselineskip]
            {\dimexpr(0.5\textwidth-0.5\columnsep-1pt)}{\wttlinewidth}
          \end{strip}
        }
    \else
      \newenvironment{widetext}[1][2]{}{}
    \fi
  }
}

\endinput

Is it intentionally that after the widetext environment the first line of the following text is indented?
This somehow then appears as a new paragraph. According to the code in the example everything should be set in one paragraph.