Re: Variable pitch text filling

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: emacs-devel@gnu.org
> Date: Wed, 01 Dec 2021 15:33:47 +0100
> 
> > We already have 1), it just needs some loving care, AFAIU?  What is
> > missing in min-width to provide 1) ?
> 
> For min-width provides both 1) and 2), but it's inefficient for both, so
> I think it makes sense to allow both these things in the char-spacing
> (or whatever we're calling it) thing.
> 
> As a practical matter, `min-width' doesn't support nesting now, and we'd
> have to make it recursive to allow having both a `min-width' on a series
> of characters and on separate characters (as we need in the U:--- thing
> in the mode line), which would further make `min-width' more inefficient.

In what way is min-width inefficient?

I'm not sure I understand the "recursive" part: if some string has a
certain value of some text property, then every character of that
string has that same value of that property, and thus you cannot have
some of those characters have the same property with a different
value.  So how can the "recursive" part work in practice?