bug#37667: 27.0.50; Tab Bar display problems with more than 5 tabs

[Juri Linkov]

> To reproduce, invoke Emacs from the src directory:
>
>   ./emacs -Q
>
> and then type:
>
>   C-x 6 f xdisp.c RET
>   C-x 6 f dispnew.c RET
>   C-x 6 f dispextern.h RET
>   C-x 6 f window.c RET
>   C-x 6 f frame.c RET
>
> The 6th button is displayed partially on the 1st tab-bar line, and the
> rest on the 2nd line, which I don't think is pretty.
>
> If you do the same in a -nw session, the 6th tab will not be visible
> at all (it looks like display_tab_bar assumes there's always just one
> tab-bar line?).

What are the possible options?

1. Use something like word-wrap in the tab-bar to wrap
   to the second line non-broken tabs at tab boundaries;

2. Disable wrapping to the second line since it's not supported in -nw;

3. Then truncate tab names to fit all tabs into the first line;

4. Or don't truncate but allow scrolling tabs with mouse wheel;