Re: Adding new variable for face-list in internal-make-lisp-face.

[Eli Zaretskii <eliz@gnu.org>]

> Date:  Sat, 04 Nov 2017 10:46:17 -0700
> From:  Keith David Bershatsky <esq@lawlist.com>
> Cc:  emacs-devel@gnu.org
> 
> I ran into one little `emacs_abort` snag this morning while trying the following two test snippets, which came about when I changed the face background with `face-remap-add-relative` on a face that had been previously defined with `defface`.
> 
> Should I run a pre-test for all 15 cases in lookup_basic_face to see if it would throw an `emacs_abort`, and then *only* call lookup_basic_face if success is guaranteed?
> 
> Alternatively, perhaps using it.face_id obviates the need to use lookup_basic_face?
> 
> TEST SNIPPETS:
> 
>   struct face *tab_face = FACE_FROM_ID (f, lookup_basic_face (f, it.face_id));
>   Lisp_Object tab_bg = tab_face->lface[LFACE_BACKGROUND_INDEX];
>   AUTO_STRING (my_string_one, "IT background:  %s");
>   CALLN (Fmessage, my_string_one, tab_bg);

You only need to call lookup_basic_face if it.face_id is a basic face
AND face-remapping-alist is non-nil.  If it.face_id is not a basic
face, lookup_basic_face will abort, and you should call lookup_face
instead.  For a remapped non-basic face you will have to look up
face-remapping-alist manually and then use lookup_named_face.