Formulary in LaTeX? Rendering complete subsection before pagebreak

Question

So i'm keeping my maths- and physics-formulas together in simple formularies in LaTeX. Right now i'm using the article class and sections / subsections for my structure, where each subsection / subsubsection stands for one formula with description:

\documentclass{article}

\begin{document}

\section{Ordinary Differential Equations}

\subsection{Solution Procedure for Ordinary Differential Equations
Some Text that describes how to solve odes
\subsection{Different Topic}
...

\end{document}

Everything is working fine and looking nice, however there's one thing that's annoying me:

I want to look on my formulas as whole! LaTeX is constructed to break subsections over multiple pages whenever the page is full, so i have to keep skimming over two pages because some formula / description was broken over automatically!

Is there something to add to my preamble that tells LaTeX to print subsections, so that the whole subsection is displayed on the same page? If not so, is there some other option (other documentclass and such) that i was missing out previously? Manual pagebreaks or newpage-commands seem to be just an ugly hack.

Bonus: if my desired behaviour is possible, what would LaTeX do, if one subsection doesn't fit on a single page?

All help is highly appreciated. Thanks in advance!

Answer 1

Grabbing the contents of a subsection seems not very reliable/stable without any change to the document. Therefore I built an environment (ssecenv) that typesets its contents in a box and checks the vertical space needed against the space left on the page.

The environment takes an optional star, an optional argument, and a mandatory argument -- just like the \subsection command.

\documentclass[]{article}

\usepackage{letltxmacro}
\usepackage{duckuments}
\usepackage{xparse}

\makeatletter
\newbox\tim@ssec
\newdimen\tim@spaceleft
\newdimen\tim@spaceneeded
\NewDocumentEnvironment{ssecenv}{ >{\tim@sProcessor}s >{\tim@OProcessor}O{} m }
  {%
    \par
    \setbox\tim@ssec\vbox\bgroup
      \subsection#1#2{#3}%
  }
  {%
    \egroup
    \tim@spaceleft=\textheight
    \advance\tim@spaceleft-\pagetotal
    \tim@spaceneeded=\ht\tim@ssec
    \advance\tim@spaceneeded\dp\tim@ssec
    \ifdim\tim@spaceneeded>\textheight
    \else
      \ifdim\tim@spaceleft<\tim@spaceneeded
        \clearpage
      \fi
    \fi
    \unvbox\tim@ssec
  }
\newcommand\tim@sProcessor[1]
  {%
    \IfBooleanTF{#1}{\def\ProcessedArgument{*}}{\def\ProcessedArgument{}}%
  }
\newcommand\tim@OProcessor[1]
  {%
    \if\relax\detokenize{#1}\relax
      \def\ProcessedArgument{}%
    \else
      \def\ProcessedArgument{[#1]}%
    \fi
  }
\makeatother

\begin{document}
\begin{ssecenv}[bar]{foo}
  \blindduck
\end{ssecenv}
\begin{ssecenv}*{foo}
  \blindduck
\end{ssecenv}
\begin{ssecenv}*[bar]{foo}
  \blindduck
\end{ssecenv}
\begin{ssecenv}{foo}
  \blindduck
  \blindduck
\end{ssecenv}
\end{document}