bug#73777: set-fontset-font doesn't set :size for specific characters when using some fonts

[Eli Zaretskii]

> From: Rodrigo Morales <rodrigo-mailing-lists@morales.pe>
> Date: Sat, 12 Oct 2024 14:10:25 -0500
> 
> 
> I am using GNU Emacs 29.4 in Ubuntu 22.04.5 LTS.
> 
> Today, I was trying to change the font size for the character =“= (#x201C, 
> LEFT DOUBLE QUOTATION MARK) using the sexp shown below. I noticed an 
> inconsistency: that sexp only sets the size for the character =“= when 
> specific fonts are used.
> 
> #+BEGIN_SRC elisp
> (set-fontset-font t ?“ (font-spec :family "Noto Sans Mono" :size 50))
> #+END_SRC

Before I start digging into how we handle :size in a fontset, I have
two questions:

 . did you reset use-default-font-for-symbols to nil? without that,
   Emacs prefers to use the default face's font for punctuation and
   symbols, effectively disregarding the fontsets
 . which fonts did you find problematic in this case? you say
   "specific fonts", but it is not clear which fonts exhibit this
   behavior

Thanks.