Replace vspace at the end of the page

Question

I'm typesetting a text with sections separated by the \vspace{1em} (sections have no titles). Sometimes the end of section coincides with the end of page. In this case the reader cannot see the end of section separator. I want to implement the following solution of this problem. When the new section ends at the end of the page, I want to replace the \vspace separator with, say, three stars ***. How can I do this?

Answer 1

The memoir class provides for this kind of anonymous division. The \plainfancybreak macro inserts some blank space between paragraphs in the middle of a page or something more fancy if the break occurs at the start or end of a page. Please read the manual for details on how to use this (texdoc memoir section 6.7 Fancy Anonymous Breaks, pp 108 -- 110)

Answer 2

The following might not be fool-proof (depending on your document construction), but it's worth a try:

\documentclass{article}

\usepackage{lipsum}\sloppy% Just for this example

% Taken from http://tex.stackexchange.com/a/36726/5764
% Taken from the needspace package (http://ctan.org/pkg/needspace)
\makeatletter
% \needspace{<len>}{<less than len>}{<more than len>}
\newcommand{\needspace}[3]{\par \penalty-100\begingroup
  \setlength{\dimen@}{#1}%
  \dimen@ii\pagegoal \advance\dimen@ii-\pagetotal
  \ifdim \dimen@>\dimen@ii
    #3
  \else
    #2
  \fi\endgroup}
\makeatother

\renewcommand{\section}{%
  \unskip\par
  \needspace{3\baselineskip}
    {\vspace{1em}}
    {\newpage\noindent\makebox[\linewidth]{* \quad * \quad *}%
     \par}%
}

\begin{document}

\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]

\end{document}

Some code from needspace checks for the available space on the current page, and conditions on what to output if there's (not) enough space.

---

The following uses the footer to insert a "\section break" that coincides with a page break:

\documentclass{article}

\usepackage{lipsum}\sloppy% Just for this example
\usepackage{fancyhdr}

% Taken from http://tex.stackexchange.com/a/36726/5764
% Taken from the needspace package (http://ctan.org/pkg/needspace)
\makeatletter
% \needspace{<len>}{<less than len>}{<more than len>}
\newcommand{\needspace}[3]{\par \penalty-100\begingroup
  \setlength{\dimen@}{#1}%
  \dimen@ii\pagegoal \advance\dimen@ii-\pagetotal
  \ifdim \dimen@>\dimen@ii
    #3
  \else
    #2
  \fi\endgroup}
\makeatother

\renewcommand{\section}{%
  \unskip\par
  \needspace{3\baselineskip}
    {\vspace{1em}}
    {\renewcommand{\sectionend}{* \quad * \quad *}%
     \newpage
     \renewcommand{\sectionend}{}}%
}

\newcommand{\sectionend}{}
\pagestyle{fancy}
\fancyhf{}% Clear fancy header/footer
\renewcommand{\headrulewidth}{0pt}% No header rule
\fancyfoot[C]{\begin{tabular}[b]{@{}c@{}} \sectionend \\ \thepage \end{tabular}}

\begin{document}

\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]
\section\lipsum[1-4]

\end{document}