Re: \hrule issue

in luatex you can (although I forget the syntax) but not classic tex. A
kern or a skip with no stretch component will never stretch, but a skip
with any stretch component will stretch arbitrarily large, just with
suitable badness if over stretched.

On Mon, 4 Aug 2025 at 13:11, Rodolfo Medina <[email protected]>
wrote:

> Thanks, David, it is clear.  If I set \parskip=0pt then TeX won't stretch
> that
> vertical space at all: the TeXbook says that in plain TeX it is set
> \parskip=0pt plus1pt, so if I set \parskip=0pt I'm implicitely setting
> `plus0pt' and so forbidding the parskip's stretchability.  But then I
> wonder
> why TeX is allowed to stretch the 1pt enormousely whereas the 0pt not at
> all.
> Suppose I want that a certain \vskip must have a maximum stretchability
> that
> TeX is not allowed to increase: is it possibile to tell TeX not to overcome
> anyway a certain amount of stretchability that I decide to set for a
> certain
> \vskip?
>
> Rodolfo
>
>