bug#69454: Not possible to insert an empty vtable

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 30 Apr 2024 18:20:36 -0500
> Cc: eric.marsden@risk-engineering.org, larsi@gnus.org, 69454@debbugs.gnu.org
> From: Adam Porter <adam@alphapapa.net>
> 
> >> In order to support empty vtables, the column width issue would have to be
> >> resolved, of course. My suggestion (again coming from my use-case) would be that
> >> if some columns have no :width slot, the remaining available width (i.e., the
> >> window width minus the explicit column widths) is divided evenly between them.
> > 
> > Sounds reasonable, but I don't use vtables.  Adam, WDYT?
> 
> Well, I'm not sure how useful it would be to calculate the widths of 
> columns and show them if there are no data objects to render in them; 
> especially, if the columns have to be recalculated and the table has to 
> be re-rendered as soon as objects are shown in it.  It would seem to 
> merely serve as confirmation of which columns are defined in the vtable.
> 
> IOW, it seems that, if there are no objects to show, it might be just as 
> good to short-circuit the columns and just insert some kind of "[no 
> objects]" string.

That's also reasonable.

> I don't have a strong opinion on this, though.  I think I would 
> generally favor whichever approach required the smallest change to the code.

Agreed.  Patches welcome.