bug#67404: 30.0.50; Issue with :box face attribute

[Eli Zaretskii]

> Date: Thu, 23 Nov 2023 16:23:15 +0100
> From: David Ponce <da_vid@orange.fr>
> 
> Hello,
> 
> The below face with specified :box attribute can be defined and further
> used without problem:
> 
> (defface test-face
>    '((t
>       (:box (:style released-button :line-width (3 . 0)))
>       ))
>    "Test face.")
> 
> (insert (propertize "XXXXX" 'face 'test-face))
> 
> However, it is not possible to apply any change to this face with
> `customize-face', for example to change :line-width (3 . 0) to
> :line-width (2 . 0), or to add a :foreground color, etc.  This fails
> with the message "set-face-attribute: Invalid face box: :line-width,
> <value>, :style, <value>", and the :box attribute is discarded.
> 
> AFAICS, :box attribute with any zero :line-width value works as
> expected: the box line with zero width is not displayed.  But zero is
> not considered as a valid value by `set-face-attribute' (in fact, the
> internal function `internal-set-lisp-face-attribute').
> 
> For consistency, a zero :line-width value either should be accepted by
> `internal-set-lisp-face-attribute', or never accepted at all.

Mauro, any comments about these issues?