Re: Tab bar tabs landed on master

[Juri Linkov]

>> >> C-2 C-TAB switches to the second next tab
>> >> C-- C-TAB switches to the previous tab
>> >
>> > This seems to have broken the C-x 6 prefix when invoking commands
>> > without an argument.  E.g., "C-x 6 f" errors out as "undefined" and
>> > "C-x 6 2" invokes 2-Column mode.  I guess this is not intentional?
>>
>> Now 2-Column mode uses only its primary mnemonic binding prefix `f2'.
>> And for backward-compatibility still binds `C-x 6' when its package is 
>> loaded.
>
> Does it mean the tab-bar related "C-x 6" prefix conflicts with 2C?  If
> so, perhaps we should use "C-x 7" instead, as long as the genie is not
> far from the bottle.

"C-x 6" is the perfect prefix for tab commands because it's easier to
remember as continuation of the sequence with window prefix "C-x 4"
and frame prefix "C-x 5":

C-x 4 - window commands
C-x 5 - frame commands
C-x 6 - tab commands

> I'd like to avoid backward-incompatible changes if possible.

Actually it's not quite backward-incompatible because it's still
available after loading two-column.el.

Also please read this comment in two-column.el that admits it's not mnemonic:

  ;; This one is for historical reasons and simple keyboards, it is not
  ;; at all mnemonic.  All usual sequences containing 2 were used, and
  ;; f2 could not be set up in a standard way under Emacs 18.
  (global-set-key "\C-x6" '2C-command)

>> > Btw, it's a pity that C-TAB and C-S-TAB aren't normally supported on
>> > TTY frames.  It would be nice to have a supported short binding, or at
>> > least to have "C-x 6 o" switch to the "other" tab.
>>
>> Ergus said that in xterm it is possible to use only C-TAB, but not
>> C-S-TAB.  I tried, and indeed C-TAB works in -nw, and even C-S-TAB
>> is available as [backtab].
>
> Don't judge by xterm, it's an exception more than the rule.  Even with
> PuTTY (which generally emulates xterm), C-TAB yields nothing in Emacs.

And [backtab] can't be used even on xterm, because it's bound to
other commands in some modes, e.g. to Info-prev-reference in Info-mode.