bug#64799: [PATCH] Add 'project-prompt-key' face

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 27 Jul 2023 04:01:17 +0300
> Cc: philipk@posteo.net, 64799@debbugs.gnu.org
> From: Dmitry Gutov <dmitry@gutov.dev>
> 
> On 26/07/2023 14:10, Eli Zaretskii wrote:
> > Beware: the 'bold' face changes the metrics of the font glyphs (wrt
> > the 'medium' variant), and at least with some fonts could cause a
> > small 1- or 2-pixel vertical resize of the mini-window, which is
> > generally distracting and even annoying.
> 
> Only non-monospaced font, though, right? Or ones without a 'bold' variant.

No, not only those.  I'm talking about the _vertical_ metrics, so
whether the font is monospaced is not relevant.  Try marking files for
deletion in Dired, and you will see that, at least with some fonts and
some sizes.  Here on MS-Windows the default face's font (Courier New)
does that, for some sizes of the font.  I have customized
eldoc-highlight-function-argument to use 'underline' instead of 'bold'
for that very reason.

> Anyway, we're talking about switching from 'bold' to 'help-key-binding', 
> which uses the default weight.

That's fine.  I was under the impression that 'bold' is also being
considered, and wanted to warn about this.