Text Formatting ⇒ thinsp | Amount of Stretch and Shrinkage

[Laurentius]

thinsp makes \thinspace stretchable, but the stretch should be 1/2 and the shrinkage 1/3; how is that done, if it isn't already so?

This seems to define the stretchability

Code: Select all

\def\stretchthinspace{%
  \nobreak\hskip\thinsp@thinamount\fontdimen2\font%
  \@plus\thinsp@thinamount\fontdimen2\font%
  \@minus\thinsp@thinamount\fontdimen4\font%
  \relax%
}

but I don't understand what \fontdimen does.