bug#72309: propertized-buffer-identification with maximum width

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sat, 27 Jul 2024 09:22:21 +0000
> From: Heime <heimeborgia@protonmail.com>
> Cc: 72309@debbugs.gnu.org
> 
> On Saturday, July 27th, 2024 at 5:48 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
> > tags 72309 notabug
> > thanks
> > 
> > > Date: Fri, 26 Jul 2024 19:04:14 +0000
> > > From: Heime via "Bug reports for GNU Emacs,
> > > the Swiss army knife of text editors" bug-gnu-emacs@gnu.org
> > > 
> > > propertized-buffer-identification could be improved so that when using a
> > > maximum width there are three dots and a space at the end to indicate
> > > that the buffer name has been truncated.
> > 
> > 
> > Emacs doesn't truncate the buffer name shown on the mode line, so no
> > ellipsis should be needed, ever. IOW, the maximum width is basically
> > infinity.
> > 
> > Where did you see the buffer name truncated on the mode line?
> 
> 
> There is this construct
> 
>  (width rest…)
> 
> which specifies truncation or padding of the results of rest. 
> 
> If used on the buffer name it just truncates without specification 
> that truncation occurred.

Where in the Emacs code did you see that?  I cannot find anything like
that in bindings.el, which is where we have the code used for
displaying the buffer name on the mode line.