bug#55842: 29.0.50; Using shorthand syntax in keymap-global-set

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 55842@debbugs.gnu.org
> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Thu, 09 Jun 2022 15:35:02 +0200
> 
> > 1. emacs -Q
> > 2. In scratch, eval (key-valid-p "C-TAB") => t
> > 3. In scratch, eval (keymap-global-set "C-TAB" #'other-window)
> > 4. Try 'C-h k Ctrl-Tab' => C-<tab> is undefined
> > 5. In scratch, eval (keymap-global-set "C-<tab>" #'other-window)
> > 6. 'C-h k Ctrl-Tab' returns the expected result.
> >
> > Am I missing something about shorthands?  Reading the docstring of
> > `key-valid-p', I thought the item 3. above should also work.
> 
> TAB is a complicated issue in Emacs, unfortunately.
> 
> "C-TAB" is just a different way to write "C-i", because TAB and C-i are
> the same in most terminals.
> 
> If you want to bind the C-<tab> key stroke, you have to specify it as
> such.  (And it won't work in most terminals, only in GUI Emacs.)
> 
> (key-valid-p "C-TAB") could signal an error to help lessen the
> confusion, I guess?  (And C-RET and C-LFD.)  Anybody got an opinion
> here?

Without thinking about this too much, my opinion is that if the new
APIs are to be the replacement for the obsolete ones, they had better
supported the same syntax, because I don't believe there's a single
Emacs user out there who doesn't have some key bindings in their init
files.  If the syntax is incompatible, how can we ever convince the
majority to switch?