bug#51277: 27.1; menu-set-font not loading correct font

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 19 Oct 2021 09:08:20 -0400
> From: Jesse Sheidlower <jester@panix.com>
> Cc: 51277@debbugs.gnu.org
> 
> > Sorry, I meant to say "M-:" instead of "M-x".  It was a typo.
> 
> OK, in this case, yes, it produces the, um, desired effect: Emacs
> displays with the "Book", rather than the "Bold", version of that font.

OK, so at least you have a workaround for this strange problem.

> Yes, it works correctly with certain other fonts. For example, DejaVu
> Sans Mono Book is correctly displayed by menu-set-font and correctly
> loaded by Emacs.
> 
> I do note that the filename of the "Book" variant of DejaVu Sans Mono
> does not contain the word "Book"; the filename is simply DejaVuSans.ttf.
> I don't know if that's relevant.

I don't think it is, no.

> Given that the recipe "emacs -Q -fn 'Operator Mono SSm'" followed by
> "M-: (set-face-attribute 'default nil :weight 'book) RET" does produce
> the desired result, does that tell us anything useful about what's going
> on, to either fix Emacs or to communicate something with Hoefler about
> fixing their font?

It puzzles me, I expected that set-face-attribute won't work as well.
Now I don't know what to think.  Hmm... maybe the font processing log
will give a clue?  In "emacs -Q", do

  M-: (setq font-log nil) RET

then repeat the recipe with selecting that problematic font, and after
that go to *scratch* and type

  (pp font-log) C-j

where C-j should be typed with cursor after the closing paren of
"(pp font-log)".  Then post the result here.