Re: display-supports-face-attributes-p question

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Sun, 29 Aug 2021 21:54:38 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >       if (! FONT_OBJECT_P (attrs[LFACE_FONT_INDEX]))
> >     attrs[LFACE_FONT_INDEX]
> >       = font_load_for_lface (f, attrs, Ffont_spec (0, NULL));
> 
> Before:
>     #<font-spec nil haiku Noto\ Sans\ Mono nil iso8859-1 normal nil normal 12 
> nil 100 0 ((:user-spec . "monospace"))>
> 
> And after:
>     #<font-object "-haiku-Noto Sans 
> Mono-normal-normal-normal-*-12-*-*-*-m-0-iso8859-1">
> 
> I don't exactly understand what the code does, but that seems wrong.  I
> think both the spec and the object should be italic?

No, only the second one.  The first one is generic, with the :slant
slot unspecified.

So it looks like the problem is inside font_load_for_lface.  Please
step into it, then into font_find_for_lface that one calls, and tell
what is the value of 'entities' here:

              for (l = 0; SYMBOLP (adstyle[l]); l++)
                {
                  ASET (work, FONT_ADSTYLE_INDEX, adstyle[l]);
                  entities = font_list_entities (f, work); <<<<<<<<<<<<<<<
                  if (! NILP (entities))

It should be a list of font-entity objects, at least some of which
have the 'italic' value in the :slant slot.

Or maybe the code behaves differently in your case, and doesn't even
get to that place?  If so, please try to figure out why.