setspace with nodisplayskipstretch causes side effects

[maresb]

I suspect that the problem described in this stackexchange post is a setspace bug. Namely, the following code at the bottom of setspace.sty causes significant side effects, even with \displayskipstretch=1 (e.g. with the nodisplayskipstretch option):

\everydisplay\expandafter{%
  \the\everydisplay
  \abovedisplayskip \displayskipstretch\abovedisplayskip
  \belowdisplayskip \displayskipstretch\belowdisplayskip
  \abovedisplayshortskip \displayskipstretch\abovedisplayshortskip
  \belowdisplayshortskip \displayskipstretch\belowdisplayshortskip
}

For a particular document I was working on, these side effects increased my page length from 97 to 100 pages.

[davidcarlisle]

multiplying the skips by 1.0 removes the stretch and shrink components, It is hard to say if that is a bug or a design decision, as far as I can tell, setspace has always multiplied the displayskips in this way (originally using \baselinestretch then since 1998 \displayskipstretch.

Rather than using 1.0 you could use no multiplier at all adding

\setdisplayskipstretch{}

after loading setspace allows all three footnotes to fit on the first page in that tex.sx example.

[maresb]

Thank you David, that command works very well for me. I have added a corresponding answer on my original tex.sx question. In addition, I wrote a new answer for the tex.sx question about Equations and Double-Spacing.

Thank you very much for the explanation (and more generally for your countless contributions to LaTeX). I can't resist congratulating you on your impending 500,000 tex.sx rep. (You're currently at 499,920!)

[davidcarlisle]

oh wow I had completely forgotten this. I just came here to open an issue based on

https://tex.stackexchange.com/questions/525629/reducing-vertical-space-before-and-after-using-align

which is the same issue.

If we were to scale the display skip without losing stretch then the code used for skip4 below could be used.

\documentclass{article}

\usepackage{setspace}

\singlespacing

\begin{document}

\showthe\abovedisplayskip
\skip0=1.2\abovedisplayskip
\skip2=\glueexpr\abovedisplayskip*12/10\relax
\skip4=1.2\abovedisplayskip \ifnum\gluestretchorder\abovedisplayskip=0
       plus 1.2\gluestretch\abovedisplayskip minus 1.2\glueshrink\abovedisplayskip 
       \fi
\showthe\skip0
\showthe\skip2
\showthe\skip4
xxx
\[\showthe\abovedisplayskip a=b\]
\end{document}