7

C-[ is equivalent to the escape key on US English keyboards, thus, any attempt at binding it will mess up M- behaviour.

Emacs seems to have no trouble telling <escape> and C-[ apart in GUI frames. The following works fine and bindings starting with M- remain to be working:

(global-set-key (kbd "<escape>") (lambda () (interactive) (message "<escape>")))

However, if I bind

(global-set-key (kbd "C-[") (lambda () (interactive) (message "C-[")))

suddenly emacs goes crazy and binding like M-x break. Moreover, pressing C-[ refuses to trigger the bound lambda. Interestingly enough, C-x @ c [ (apply modifier control to open bracket) still says C-[ is undefined.

Is there any way of binding something to C-[ without breaking emacs?

0

The following solution is a bit kludky, but seems to work:

Let ~/.xbindkeysrc contain the following:

"xvkbd -xsendevent -text '\[Control_L]\[F13]'"
  m:0x14 + c:34

"xvkbd -xsendevent -text '\[Control_L]\[F14]'"
  m:0x14 + c:35

Now xbindkeys will translate C-[ to C-<f13> and C-] to C-<f14>, so they can be bound in emacs freely. You will probably want to bind abort-recursive-edit to something other than C-], for example, C-S-g.

The downside is that now C-[ is broken in every application except Emacs, which could be fixed by adding some logic to test whether the key combination is being sent to emacs...

  • FWIW, I don't think there's anything special about C-]. – Malabarba Jan 31 '15 at 13:25
  • Yeah, me neither, but for some odd reason my C-] binding stopped working after I fired up Xbindkeys, so I rebound that one, too. – Kristóf Marussy Jan 31 '15 at 13:28

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