[Tex/LaTex] How to use \SetSinglespace from setspace

Question

The file setspace.sty documents the command \SetSinglespace:

% GT:  Tue 10 Dec 1996:  Instead of fixing singlespacing to exact unity,
% allow user to redefine it (only slightly, please!) from its initial
% value of unity, in the case when a particular font is slightly larger
% or slightly smaller than its point size would indicate.  This change
% affects setspace's single spacing commands, and LaTeX's footnote and
% float environments.  The one and a half, double, and arbitrary
% spacing commands are unaltered.

which is followed by

\newcommand{\SetSinglespace}[1]{%
  \def\setspace@singlespace{#1}%
}

% Here's the default single line spacing value.
\SetSinglespace{1}

I was under the impression that I could use \SetSinglespace to change the behavior of “single spacing”. When using Fira Sans in my documents, I want to use the font’s recommended leading, which is 1.4 times the font size. I tried

\documentclass{article}
\usepackage[sfdefault]{FiraSans}
\usepackage[nodisplayskipstretch]{setspace}
\SetSinglespace{1.167}% 1.4/1.2
%\setstretch{1.167}

\usepackage{blindtext}

\begin{document}
\blindtext
\end{document}

But it had no effect.

Note that \setstretch{1.167} is not a solution, as it turns off line stretching in footnotes and floats. In my case the line stretching is desired.

Answer 1

You have set the skip for use when \singlespacing is active. However, you never make this active.

\documentclass{article}
\usepackage[sfdefault]{FiraSans}
\usepackage[nodisplayskipstretch]{setspace}
\SetSinglespace{1.167}% 1.4/1.2
\singlespacing

\usepackage{blindtext}

\begin{document}
\blindtext
\end{document}