scheme_switcher.vim

function! s:RandomNumber(limit) 
  let components = split(reltimestr(reltime()), '\.')
  let microseconds = components[-1] + 0
  return microseconds % a:limit
endfunction

function! s:RandomScheme() 
  let choices = []
  for fname in globpath(&runtimepath, 'colors/*.vim', 1)
    let choices += [fnamemodify(fname, ':t:r')]
  endfor
  let index = s:RandomNumber(len(choices))
  execute 'colorscheme' fnameescape(choices[index])
endfunction

let s:total=1
function! functions#SwitchScheme()
  call feedkeys("f\e")
  if(s:total % 15 == 0)
    " update time is usually set to 4 seconds
    " So the scheme would be changed on 1 minute of inactivity
    call s:RandomScheme()
  endif
  let s:total += 1
endfunction