minimal-autocomplete.vim

set cot=menu,menuone

ino <BS> <BS><C-r>=getline('.')[col('.')-3:col('.')-2]=~#'\k\k'?!pumvisible()?"\<lt>C-n>\<lt>C-p>":'':pumvisible()?"\<lt>C-y>":''<CR>
inoremap <expr> <CR>    pumvisible() ? "\<C-y>" : ""
inoremap <expr> <Tab>   pumvisible() ? "\<C-n>" : "\<Tab>"
inoremap <expr> <S-Tab> pumvisible() ? "\<C-p>" : "\<S-Tab>"

function! s:skinny_insert(char)
  if !pumvisible() && !exists('s:skinny_complete') &&
              \ getline('.')[col('.') - 2].a:char =~# '\k\k'
    let s:skinny_complete = 1
    noautocmd call feedkeys("\<C-n>\<C-p>", "nt")
  endif
endfunction

augroup SkinnyAutoComplete
  autocmd!
  autocmd InsertCharPre * call <SID>skinny_insert(v:char)
  autocmd CompleteDone * if exists('s:skinny_complete') | unlet s:skinny_complete | endif
augroup END