Defining my own key

Question

I saw the so called <Leader> in my vimrc quite often. But is there a way to define my own key in a similar manner? I mean I would like to define some sort of <Mykey> and use it further in my vimrc to define more complicated combinations. I mean something like this:

nnoremap <Mykey>u "some keystroke

This means that depending on how I define <Mykey> I get different combinations with it.

Answer 1

You can define your own <leader> key with:

let mapleader = "something"

You could also hack the <localleader> to get a second <leader>:

let localleader = "something else"

But <leader> and <localleader> are not special keys at all. Assuming your <leader> is set to , (the example in :help mapleader) the two mappings below are strictly equivalent:

nnoremap <leader>f :find *
nnoremap ,f        :find *

So, basically, you can use any normal key to function as <leader> without setting anything.

Answer 2

Vim has this abstraction, and it's <Leader> (and the <LocalLeader> variant which is meant for buffer-local mappings). Unfortunately, there's only one.

If you need a common prefix for a set of custom mappings, and you want to be able to change this in a single location, you can define a variable, and then use :execute to define the mappings.

Example

let g:MyKey = '<Leader>x'
execute 'nnoremap' g:MyKey . 'u' "some keystroke
execute 'nnoremap' g:MyKey . 'v' "another keystroke

Answer 3

Here's an interesting usage that I first saw (and wandered about) in Shougo's Unite plugin, which creates an artificial leader key "placeholder" (I'm quoting directly from the Unite's help file):

" The prefix key.
nnoremap    [unite]   <Nop>
nmap        f         [unite]

nnoremap <silent> [unite]c  :<C-u>UniteWithCurrentDir
        \ -buffer-name=files buffer bookmark file<CR>

... (etc.)

In the above example, the whole sequence of characters [unite] is mapped non-recursively in normal mode to do nothing (and thus, it becomes a "prefix"!) Then, a "leader" key is assigned to this complicated <Nop>; in this case, f.

What follows are the actual maps, in which every time you type f <some other char(s)>, Vim translates it to [unite] <some other char(s)> -- if the combination is defined (and typed in time), the map gets executed, otherwise -- the prefix is cancelled (because it gets resolved by itself to <Nop>, i.e. nothing) and it's like you didn't type it at all. Mind boggling.

I didn't test, but I think the way the sequence itself is defined (here, [unite]) is quite relevant -- if I got it right, it will create delays for any key combinations starting with [, [u, [un and so on. So you would always want to use a leader placeholder "string" that starts with characters you don't normally (pun) use by themselves.