light vim fold text

foldtext.vim

" class Foo(Bar):                                                           │
"     └── [ 13 ] ────•

set fillchars="fold: "

setlocal foldtext=ManualFillCharText()

function! ManualFillCharText()
  " TODO: make it support the tabs/spaces/different width
  let total = (v:foldend - v:foldstart)
  let init_chars = repeat('    ', foldlevel(v:foldstart))
  let actual = init_chars . '└──' . ' [ ' . total . ' ] '
  return actual . '────•'
endfunction