Re: Making `x-underline-at-descent-line' a face attribute

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Fri, 07 Jan 2022 20:33:41 +0800
> 
> Judging by the contents of that function, it's a hash of the internal
> vector representation of a face, and not of a struct face itself.

You've just understood the difference between the "Lisp face" and
"realized face".  Well, more or less, anyway.