bug#30553: 26.0.91; underline appears beneath line-spacing rather than beneath text

[Eli Zaretskii <eliz@gnu.org>]

> From: Aaron Jensen <aaronjensen@gmail.com>
> Date: Wed, 28 Feb 2018 09:41:50 -0800
> Cc: Alp Aker <alptekin.aker@gmail.com>, 30553@debbugs.gnu.org
> 
> On Wed, Feb 28, 2018 at 8:14 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> > Fbuffer_local_value can signal an error, which is a no-no in display
> > code.  So it's best not to use it.  buffer_local_value is better in
> > that regard, I think (although for built-in variables, I think the
> > danger is mainly academic).
> 
> Ah, that's good to know. When would it return Qunbound? It looked like
> from the docs it would return it if it wasn't bound in the
> buffer--does that mean it does or it doesn't fall back to the default
> value or the value set via setq? I'm afraid I don't know exactly how
> this works.

If there's no buffer-local value, it returns the global value.  Only
if the variable is entirely unbound (as in "void variable"), it will
return Qunbound.

> Does this mean that I'd have to do similar code as you suggested for
> the int?

Yes.

> Is there an example of coercing a potentially unbound bool?

Just treat Qunbound as the default value of the respective variable.

Thanks.