bug#70637: :box vertical bar artifacts at 'display boundaries

[Eli Zaretskii]

> From: JD Smith <jdtsmith@gmail.com>
> Date: Thu, 9 May 2024 09:31:28 -0400
> Cc: 70637@debbugs.gnu.org
> 
> I presume this is a more general issue than just :box.  One idea is to add a 
> warning to the Elisp section "Display
> Specs That Replace The Text", perhaps at the end:
> 
>  Note: certain `face' attributes such as `:box' can lead to display artifacts 
> when applied to the replacing
>  text in a `display' specification.  These attributes may be incorrectly 
> merged with adjacent non-`display'
>  `face' properties.  This can be mitigated by applying the `face' attributes 
> directly to the text being
>  replaced, rather than (or in addition to) the `display' replacement text 
> itself.

Actually, this is specific to :box, since only for that attribute we
need to determine the beginning and the end of the box.

> Maybe a bit too wordy.

Yes, I agree.  If you can reword it to be specific to :box and to
include an example, I think it would be good.

Thanks.