bug#47234: 28.0.50; frame-inner-height fails without window system on tab-bar-height

[Eli Zaretskii <eliz@gnu.org>]

> From: Juri Linkov <juri@linkov.net>
> Cc: martin rudalics <rudalics@gmx.at>,  Eli Zaretskii <eliz@gnu.org>,  47234@debbugs.gnu.org
> Date: Thu, 18 Mar 2021 19:07:55 +0200
> 
> >>> Is the following close to TRT?
> >>
> >> If it produces the right result under all of the complications you
> >> mentioned, sure.
> >
> > Thanks, it does AFAICT.  Hopefully Juri can confirm/deny for certain.
> > (For example, I don't know when one would pick Ftab_bar_height over the
> > frame property tab-bar-lines - maybe the latter can be used
> > unconditionally?)
> 
> I agree with Martin that `tab-bar-height' should return a meaningful value
> on --without-x builds too.

How do you propose to do that?  The design and implementation of the
code in tab-bar-height was stolen from the tool bar, and that was
written for GUI frames.  The text-mode tab bar has an entirely
different design and implementation, similar to the text-mode menu
bar.  There's almost nothing in common between these two.

> Please note this should be fixed on the release branch in Emacs 27.2
> because the change in commit 6c5ddf0e0b was recently made in emacs-27.

Why does it have to be done in Emacs 27.2?

Please be aware that Emacs 27.2 is all but released at this point.

> I wonder why only tab-bar-height was added to frame-inner-height,
> why not menu-bar-height as well?  Moreover, such function as
> menu-bar-height doesn't exist at all.  Why only tab-bar-height is needed?

Maybe tab-bar-height is not needed in this case, either.  We could
instead modify the code that attempts to call it.