Re: Changing font weight with buffer-face-mode-invoke

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 26 Jun 2024 19:32:35 +0000
> From: Heime <heimeborgia@protonmail.com>
> Cc: help-gnu-emacs@gnu.org
> 
> On Wednesday, June 26th, 2024 at 6:39 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
> > I think you want list-fonts. See the node "Low-Level Font" in the
> > ELisp manual, it describes this stuff.
> 
> Have done the following tools.  But am getting
> 
> Debugger entered--Lisp error: (wrong-type-argument stringp #<font-entity ftcrhb urw URW\ Chancery\ L nil iso10646-1 medium italic normal 0 nil nil 0 ((:font-entity "/usr/share/fonts/X11/Type1/z003034l.pfb" . 0))>)
>   string-match("-" #<font-entity ftcrhb urw URW\ Chancery\ L nil iso10646-1 medium italic normal 0 nil nil 0 ((:font-entity "/usr/share/fonts/X11/Type1/z003034l.pfb" . 0))> 0)
>   split-string(#<f

list-font returns font _entities_, which are not strings.  So they
cannot be passed to split-string.

> (defun mon-font-info (font)
> 
>   "Get font attributes for FONT."
> 
>   (let ((attrs (split-string font "-")))
> 
>     (vector (nth 1 attrs)     ; Weight
> 
>             (nth 2 attrs)     ; Slant
> 
>             (nth 3 attrs))))  ; Width

Since in your case FONT is a font entity, not a font name, the way to
get attributes of FONT is to use font-get (passing it the attribute
you are interested in as the 2nd argument).