How can I get all paragraphs in a block to have a hanging indent?

Question

I have a manual bibliography (i.e. not bibtex) that I'd like to indent with hanging indent (only second, third, etc, lines). Ideally, I'd like not to have to do this with a command on each line, but for the whole block, like \begin{hangingindent} and \end{hangingindent}. How do you do that?

Answer 1

Perhaps a list environment is all you need?

\documentclass{article}

\newenvironment{hangingpar}[1]
  {\begin{list}
          {}
          {\setlength{\itemindent}{-#1}%%'
           \setlength{\leftmargin}{#1}%%'
           \setlength{\itemsep}{0pt}%%'
           \setlength{\parsep}{\parskip}%%'
           \setlength{\topsep}{\parskip}%%'
           }
    \setlength{\parindent}{-#1}%%
    \item[]
  }
  {\end{list}}

\usepackage{lipsum}


\pagestyle{empty}
\begin{document}

  \begin{hangingpar}{2em}
  \lipsum[1-5]  
  \end{hangingpar}

  \vspace{2ex}

  But, \lipsum[6-7]

\end{document}

Alternatively, you could define an environment as follows:

\newenvironment{hangingparII}[1]
  {\setlength{\leftskip}{#1}%%
   \setlength{\parindent}{#1}%%
  }
  {\par}

This approach is not quite equivalent to the first. \leftskip handles the horizontal placement of displayed math differently from how a list environment handles things as the following MWE illustrates.

\documentclass{article}

\newenvironment{hangingpar}[1]
  {\begin{list}
          {}
          {\setlength{\itemindent}{-#1}%%'
           \setlength{\leftmargin}{#1}%%'
           \setlength{\itemsep}{0pt}%%'
           \setlength{\parsep}{\parskip}%%'
           \setlength{\topsep}{\parskip}%%'
           }
    \setlength{\parindent}{-#1}%%
    \item[]
  }
  {\end{list}}


\newenvironment{hangingparII}[1]
  {\setlength{\leftskip}{#1}%%'
   \setlength{\parindent}{-#1}%%'
  }
  {\par}

\usepackage{lipsum}
\pagestyle{empty}
\begin{document}

  \begin{hangingpar}{3em}
  Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut
  purus elit, vestibu- lum ut, placerat ac, adipiscing vitae,
  felis. Curabitur dictum gravida mauris.  Nam dui ligula,
  fringilla a, euismod sodales, sollicitudin vel, wisi.
  \[
    \sin^2(x) + \cos^2(x) = 1
  \]
  Morbi auctor lorem non justo. Nam lacus libero, pretium at,
  lobortis vitae, ultricies et, tellus. Donec aliquet, tortor sed
  accumsan bibendum, erat ligula aliquet magna, vitae ornare odio
  metus a mi. Morbi ac orci et nisl hendrerit mollis. 

  Suspendisse ut massa. Cras nec ante. Pellentesque a nulla. Cum
  sociis natoque penatibus et magnis dis parturient montes,
  nascetur ridiculus mus. Aliquam tincidunt urna. Nulla
  ullamcorper vestibulum turpis. Pellentesque cursus luctus
  mauris.
  \end{hangingpar}      

  \begin{hangingparII}{3em}
  Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Ut
  purus elit, vestibu- lum ut, placerat ac, adipiscing vitae,
  felis. Curabitur dictum gravida mauris.  Nam dui ligula,
  fringilla a, euismod sodales, sollicitudin vel, wisi.
  \[
    \sin^2(x) + \cos^2(x) = 1
  \]
  Morbi auctor lorem non justo. Nam lacus libero, pretium at,
  lobortis vitae, ultricies et, tellus. Donec aliquet, tortor sed
  accumsan bibendum, erat ligula aliquet magna, vitae ornare odio
  metus a mi. Morbi ac orci et nisl hendrerit mollis. 

  Suspendisse ut massa. Cras nec ante. Pellentesque a nulla. Cum
  sociis natoque penatibus et magnis dis parturient montes,
  nascetur ridiculus mus. Aliquam tincidunt urna. Nulla
  ullamcorper vestibulum turpis. Pellentesque cursus luctus
  mauris.

  \end{hangingparII}      

\end{document}

Answer 2

Redefining thebibliography with the help of \parshape can be a solution.

Add these lines to your preamble and adjust the length of \listindent to your needs.

\newlength\listindent
\setlength\listindent{50pt}
\newlength\labellength

\let\oldthebibliography\thebibliography
\let\oldendthebibliography\endthebibliography
\renewenvironment{thebibliography}[1]
 {%
  \settowidth{\labellength}{#1}\addtolength{\labellength}{1em}%
  \oldthebibliography{#1}%
  \parshape=2%
    \labellength \linewidth%
    \listindent \dimexpr\linewidth-\listindent+\labellength\relax%
  }{%
   \oldendthebibliography%
  }

MWE:

\documentclass{article}

\newlength\listindent
\setlength\listindent{50pt}
\newlength\labellength

\let\oldthebibliography\thebibliography
\let\oldendthebibliography\endthebibliography
\renewenvironment{thebibliography}[1]
 {%
  \settowidth{\labellength}{#1}\addtolength{\labellength}{1em}%
  \oldthebibliography{#1}%
  \parshape=2%
    \labellength \linewidth%
    \listindent \dimexpr\linewidth-\listindent+\labellength\relax%
  }{%
   \oldendthebibliography%
  }


\begin{document}

\begin{thebibliography}{9}
    \bibitem{item1} text text text text text text text text text text text text text
     text text text text text text text text text text text text text text text text
     text text text text text text text text text text text text text text text text
    \bibitem{item2} text text text text text text text text text text text text text
     text text text text text text text text text text text text text text text text
     text text text text text text text text text text text text text text text text
\end{thebibliography}

\end{document}

Output: