How to rebind Ctrl-[ in .vimrc

Question

In vim, Ctrl + [ acts like Esc by default. However, I would like to rebind Ctrl + [ to perform a custom action. (Specifically, to Ctrl-t because I find it more natural for [ and ] to have complementary actions for ctags.)

However, when I execute the command:

:nnoremap <C-[> <Ct>

then my arrow key navigation get messed up. I'm not sure what happens, but clearly that's not the ideal way to do it.

I've tried to unbind Ctrl + [ but vim reports that it wasn't bound, and I've tried some tricks like first binding Ctrl + [ to itself and then unbinding. Always the same result.

Side note: Interestingly, when I add it to my .vimrc (as the last command) it's even worse. Something nondeterministic happens and vim opens randomly in one of these 3 states:

• The bottom status line says "E73: tag stack empty", implying it received a Ctrl + t -esque command, however the if I hit a nav key like j , it deletes the current and bottom line and then puts me into insert mode. (Happens ~70% of the time.)

• Sometimes it's in replace mode. (Happens ~15% of the time.)

• Sometimes it's in normal mode. (Happens ~15% of the time.)

How can I properly remap Ctrl + [ to a different function in .vimrc ?

Answer 1

You can't rebind Ctrl [ . Pressing the Escape key in a terminal sends Ctrl [ , just like pressing the Tab key sends Ctrl I . There's no separate Esc code.

Vim is probably acting crazily when you try this because basically every ANSI key sequence starts with Ctrl [ , so your rebinding is firing on all terminal input , and whatever else is in the key sequence looks like more commands to vim.

Answer 2

Due to the way that the keyboard input is handled internally, this unfortunately isn't generally possible today, even in GVIM. Some key combinations, like Ctrl + non-alphabetic cannot be mapped, and Ctrl + letter vs. Ctrl + Shift + letter cannot be distinguished. (Unless your terminal sends a distinct termcap code for it, which most don't.) In insert or command-line mode, try typing the key combination. If nothing happens / is inserted, you cannot use that key combination. This also applies to <Tab> / <CI> , <CR> / <CM> / <Esc> / <C-[> etc. (Only exception is <BS> / <CH> .) This is a known pain point, and the subject of various discussions on vim_dev and the #vim IRC channel.

Some people (foremost Paul LeoNerd Evans) want to fix that (even for console Vim in terminals that support this), and have floated various proposals, cp. http://groups.google.com/group/vim_dev/browse_thread/thread/626e83fa4588b32a/bfbcb22f37a8a1f8

But as of today, no patches or volunteers have yet come forward, though many have expressed a desire to have this in a future Vim 8 major release.