Make all single line paragraphs \noindent

Question

I want to make all multi-line paragraphs with indentation and all single line paragraphs without. Similar to what is described in Turn off paragraph indention for a single line.

But!

I need to auto-generate the LaTeX code, so I don't know in advance if the paragraph will be single or multi-line.

Is there any way to ask for that kind of style formatting?

Answer 1

In my opinion what you want to do makes for very bad typography.

Here's a very rudimentary method, that however only allows for normal paragraphs; lists or anything like that will break it.

\documentclass{article}

\def\testpar#1\par{%
  \sbox0{#1}%
  \ifdim\wd0<\columnwidth
    {\setbox0=\lastbox}#1\par
  \else
    #1\par
  \fi
}

\newenvironment{astounding}
  {\everypar={\testpar}}
  {}

\begin{document}

\begin{astounding}
This is a single line.

This line will be two lines long if I just add a few words
and more words until it is long enough.

\end{astounding}

\end{document}