In a paper, I need to use the abbreviated form of Figure as in "see Fig. 2". To avoid line breaks between Fig. and the number itself, I place a ~ in between. However in that case, the inserted space is way too much and a \, looks a lot better.
So the question is, how can I protect the Figure expressions from line breaks but also reduce the space to \,?
\, is defined as
\DeclareRobustCommand{\,}{%
\relax\ifmmode\mskip\thinmuskip\else\thinspace\fi
}
\def\thinspace{\kern .16667em }
Thus it is basically a \kern. It is not followed by glue, therefore there is no line break caused by \, in:
see~Fig.\,2
A fast test:
\documentclass{article}
\begin{document}
\parbox{0pt}{%
\hspace{0pt}% allow hyphenation for the first word
see~Fig.\,2
}
\end{document}
As expected, there is an overfull \hbox warning:
Overfull \hbox (38.80566pt too wide) in paragraph at lines 9--9
\OT1/cmr/m/n/10 see Fig.2
And the line is unbroken:
\, can bite: a user wanted to add it in front of words (I don't really know why); if that word was at the beginning of a paragraph, the kern was added as a vertical space, because of how \kern works. In this case it's safe, though, because it will always be preceded by a character.
\kern at the beginning of a paragraph detects that it's in vertical mode, and that's how the kern is applied. like \hbox in that location, it doesn't switch into horizontal, but remains in vertical mode, usually causing the user to scratch his/her head in (at least momentary) confusion.
Sep 16, 2013 at 12:24
\thinspace should include \leavevmode, as it's documented as a text command.