How to compute the remaining space on the current page

Question

Is there a way to compute the remaining space on the current page and issue an optional command?

Answer 1

See the needspace package. It might do what you need, or at least give inspiration for whatever it is you're trying to do :-) Namely, the \pagegoal and \pagetotal registers should help.

Answer 2

In ConTeXt, \testpage[n] checks if there is enough space for n lines.

Answer 3

Here is a small example demonstrating how the accepted answer's \pagetotal etc behave -- note they only seem to change after a \par (click for high resolution image):

Here is the code used for it:

\documentclass{article}

% http://www.tug.org/utilities/plain/cseq.html#pagedepth-rp
\def\tpageitemsB{%
  \the\pagetotal;%
  \the\pagegoal;%
  \the\pagedepth;%
  \the\pagestretch;%
  \the\pageshrink;%
  \the\pagefilstretch;%
  \the\pagefillstretch;%
  \the\pagefilllstretch%
}
\begin{document}

\tpageitemsB: ligula aliquet magna,  \\
\tpageitemsB:  Morbi ac orci et nisl \\
\tpageitemsB: Suspendisse ut massa.  \\
\tpageitemsB: a nulla. Cum sociis na \\
\tpageitemsB: dis parturient montes, \\
\tpageitemsB: Aliquam tincidunt urna \\
\tpageitemsB: vestibulum turpis. Pel \\
\tpageitemsB: mauris.                \\

\noindent
\tpageitemsB: Nulla malesuada porttitor  \par\noindent
\tpageitemsB: congue non, volutpat       \par\noindent
\tpageitemsB: libero. Vi- vamus viverra  \par\noindent
\tpageitemsB: nonummy pel- lentesque     \par\noindent
\tpageitemsB: semper elit. Proin fer     \par\noindent
\tpageitemsB: diam turpis, molestie vita \par\noindent
\tpageitemsB: nec, leo. Maecenas lacinia \\
\tpageitemsB: eleifend at, accumsan nec, \\
\tpageitemsB: Morbi blandit ligula feugi \\
\tpageitemsB: consequat lorem. Sed lacin \\
\tpageitemsB: Pellentesque tincidunt pur \\
\tpageitemsB: non enim. Praesent euis    \\
\tpageitemsB: mobibendum quam in telus.  \\
\tpageitemsB: lectus. Donec et mi. Nam v \\
\tpageitemsB: Vestibu- lum pellentesque  \\
\tpageitemsB:\\
\tpageitemsB: Quisque ullamcorper placer \\
\tpageitemsB: Morbi vel justo vitae lacu \\
\tpageitemsB: Lorem ipsum do- lor sit am \\
\tpageitemsB: adipiscing elit. In hac ha \\
\tpageitemsB: Integer tempus convallis a \\
\tpageitemsB: Nunc elementum fermentum w \\
\tpageitemsB: imperdiet, enim sed gravid \\
\tpageitemsB: odio placerat quam, ac pul \\
\tpageitemsB: enim. Nunc vitae tortor. P \\
\tpageitemsB: amet nisl. Vi- vamus quis  \\
\tpageitemsB: vehicula.                  \\

\noindent
\tpageitemsB: Fusce mauris. Vestibulum l \\
\tpageitemsB: Sed bibendum, nulla a fauc \\
\tpageitemsB: ultricies tellus, ac venen \\
\tpageitemsB: Vestibulum diam. Aliquam p \\
\tpageitemsB: sagittis posuere, turpis l \\
\tpageitemsB: hendrerit risus eros eget  \\
\tpageitemsB: erat in sapien mattis port \\
\tpageitemsB: porttitor. Nulla facilisi. \\
\tpageitemsB: com- modo facilisis. Morbi \\
\tpageitemsB: dignissim inter- dum, just \\
\tpageitemsB: et vehicula libero dui cur \\
\tpageitemsB: ligula sed lacus. Duis cur \\
\tpageitemsB: ac magna. Cras nulla. Null \\
\tpageitemsB: leo. Quisque egestas wisi  \\

\end{document}