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

[Eli Zaretskii <eliz@gnu.org>]

> From: "Basil L. Contovounesios" <contovob@tcd.ie>
> Cc: 47234@debbugs.gnu.org,  juri@linkov.net
> Date: Thu, 18 Mar 2021 14:57:52 +0000
> 
> > TRT is to teach Emacs to return the tab-bar height on TTY frames as
> > well.  But I don't think defining tab-bar-height on TTY frames is the
> > right way: the tab-bar is always 1 line high on those frames, so we
> > could simply use that hardcoded value instead of signaling an error, I
> > think.
> 
> I'm not familiar with the tab bar, but I get the impression it's not
> that simple.

To be sure, I didn't mean to use just the number 1 there.

> IIUC no lines should be subtracted if tab-bar-mode is off,
> and even if it's on, the tab bar can be hidden subject to tab-bar-show.
> That's why I was wondering whether this logic can/should be packed into
> a single place (whether Ftab_bar_height or other I don't know).
> 
> Is the following close to TRT?

If it produces the right result under all of the complications you
mentioned, sure.

Thanks.