Unmap all combinations starting with certain key

Question

I am experimenting with default key mappings and am considering remapping the g key entirely. But first I would like to turn off all the existing mappings that g has. For now I am using this kind of hack:

" disable all g maps
let g:netrw_nogx = 1 " allows disabling gx
let s:chars1 = map(range(char2nr('a'), char2nr('x')), 'nr2char(v:val)')
let s:chars2 = map(range(char2nr('A'), char2nr('Z')), 'nr2char(v:val)')
let s:chars = s:chars1 + s:chars2
let s:chars = s:chars+['0','1','2','3','4','5','6','7','8','9','+','-','=','_']
let s:chars = s:chars+['~','`','!','@','#','$','%','^','&','*','(',')','/','?']
let s:chars = s:chars+['[',']','{','}','\','\|',':',';','"',"'",'<',">",'.',',']

for char in s:chars
  execute 'noremap g' . char . ' <nop>'
endfor

But this is very messy and g<ctrl-_> maps are still left in.

Is there some cleaner way to accomplish this?

Answer 1

Suppressing the built-in g

Here's a mapping that will suppress all g-prefixed bindings, and only allow custom mappings that begin with g.

function! SuppressG()
  let c = nr2char(getchar())
  if maparg('g'.c, 'n') != ''
    return 'g'.c
  else
    return '\<Nop>'
  endif
endfunction

nnoremap <expr> g SuppressG()

The idea is to make a top-level mapping for g itself that then reads a single character from the keyboard. If a Normal mode mapping to g followed by the input character exists, return that. Otherwise, return <Nop>. It works with chords, too.

The effect is that when you haven't defined any other mappings beginning with g, all of Vim's built-in bindings beginning with g will do nothing. For example, ge, which normally moves backwards to the end of a word, would now be a no-op.

Creating a custom mapping

If you also defined a custom mapping to ge, then your mapping would take effect. Example:

nnoremap ge G

Now ge moves to the last line of the buffer, but all other g bindings still do nothing.

Restoring built-ins

You can also restore the g mappings you want to keep. For example:

nnoremap gg gg

This makes gg once again move to the first line of the buffer.

Answer 2

If your version of vim is recent enough, you could obtain all the mappings starting with g thanks to getcompletion('g', 'mapping').

However, you won't know the mode associated, you'd need to filter the list with mapcheck().

Of course, you won't obtain the default keybindings this way.

Answer 3

A small generalization to tommcdo's excellent suggestion:

function! SuppressAllStartingWith(c1)
  let c2 = nr2char(getchar())
  if maparg(a:c1.c2, 'n') != ''
    return a:c1.c2
  else
    return '\<Nop>'
  endif
endfunction

Then you can use it like so:

nnoremap <expr> q SuppressAllStartingWith('q')
nnoremap <expr> z SuppressAllStartingWith('z')

As for motivation, in command mode I'm always fat-fingering 'z' when I'm heading for 'x', or 'q' when I'm heading for 'a', and I'm tired of that.