bug#66317: Project mode-line

[Dmitry Gutov]

On 10/10/2023 10:10, Eshel Yaron wrote:
> Juri Linkov <juri@linkov.net> writes:
>
> > > > > > > > Agreed.  No need to support it in older versions.  Moreover,
> > > > > > > > I'm trying to add another option to join project and vc indicators
> > > > > > > > on the mode-line that won't be possible to support in older versions.
> > > > > > > Then that needs to be explained in the docstring. project.el is installable
> > > > > > > in older versions.
> > > > > > Hopefully I explained this sufficiently well in the docstring
> > > > > > both for users of older versions and users who customized the
> > > > > > default mode line.
> > > > > Not sure: I imagine that most users don't customize mode-line-format
> > > > > themselves, and thus don't know which contents it has.
> > > > >
> > > > > I would append some clarification that in Emacs 30 the mode-line has that
> > > > > element by default.
> > > > I'm not sure if this helps because a user might run Emacs 30
> > > > and still using some package that heavily modifies the mode line.
> > > > This will puzzle the user: why it doesn't work in Emacs 30
> > > > as documented.
> > >
> > > Hence "by default".
> > >
> > > Mode-line package authors might be helped out by this explanation as well.
> >
> > Maybe this would be sufficient:
> >
> > diff --git a/lisp/progmodes/project.el b/lisp/progmodes/project.el
> > index 2475d7c403e..1d6c9c1cf1b 100644
> > --- a/lisp/progmodes/project.el
> > +++ b/lisp/progmodes/project.el
> > @@ -2109,7 +2109,8 @@ project-uniquify-dirname-transform
> >   (defcustom project-mode-line nil
> >     "Show the current project name with the menu on the mode line.
> >   This feature requires the presence of the following item in
> > -`mode-line-format': `(project-mode-line project-mode-line-format)'."
> > +`mode-line-format': `(project-mode-line project-mode-line-format)'
> > +that already exists by default in Emacs 30."
>
> To me, this description looks a bit too implementation-focused.  How
> about the following?

I'm fine with either, but...

>      Show the name of the current project on the mode line.
>
>      This option only works in Emacs 30 or later, for a similar effect in
>      Emacs 29 or earlier add `project-mode-line-format' to your
>      `mode-line-format' instead of using this option.

There might be a problem in the fact that it still won't work in Emacs 
30 if the user had customized the mode-line (or installed one of the 
packages that do).

Also: "in addition", not "instead".