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 08:47:17 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > What would you like me to elaborate on? the :extend attribute? or
> > something else?
> 
> Yes, specifically the issues encountered while adding it.

There were too many, search the debbugs database.  Basically, how to
merge faces with different values of the attribute, how to inherit the
attribute, etc.

> > For example, what does it mean when a face specifies this new
> > attribute, but doesn't specify :underline?  Or what if it does specify
> > :underline, but its style is 'wave'?
> 
> If :underline isn't specified but this new attribute is, then the
> underline should just not be drawn.  As for a wave, it can be drawn at
> the descent line as well.

Those are your opinions, but they are not necessarily correct/evident,
and I can envision use cases and/or users who would have different
expectations.

It is better to avoid the need to resolve these issues in the first
place.