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

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Tue, 11 Jan 2022 08:47:34 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Can you post some tests to run and see if it works OK?
> 
> Here you go:
> 
>   ;; Underline should appear at 3 pixels above the descent line.
>   (set-face-attribute 'default nil :underline '(:position 3))
> 
>   ;; Underline should appear at the descent line.
>   (set-face-attribute 'default nil :underline '(:position 0))
> 
>   ;; Underline should appear at the descent line.
>   (set-face-attribute 'default nil :underline '(:position t))
> 
>   ;; Underline should appear at the default location determined by
>   ;; x-use-underline-position-properties.
>   (set-face-attribute 'default nil :underline '(:position nil))

The last one signals an error:

  Debugger entered--Lisp error: (error "Invalid face underline" :position nil)
    internal-set-lisp-face-attribute(default :underline (:position nil) 0)
    set-face-attribute(default nil :underline (:position nil))
    eval((set-face-attribute 'default nil :underline '(:position nil)) t)
    eval-expression((set-face-attribute 'default nil :underline '(:position 
nil)) nil nil 127)
    funcall-interactively(eval-expression (set-face-attribute 'default nil 
:underline '(:position nil)) nil nil 127)
    call-interactively(eval-expression nil nil)
    command-execute(eval-expression)

The rest seem to work correctly.