vim-airline-themes/autoload/airline/extensions/bufferline.vim

" MIT License. Copyright (c) 2013 Bailey Ling.
" vim: et ts=2 sts=2 sw=2

function! airline#extensions#bufferline#apply(...)
  " revert to default in non-active splits
  for nr in filter(range(1, winnr('$')), 'v:val != winnr()')
    if matchstr(getwinvar(nr, '&statusline'), '%{bufferline') != ''
      call setwinvar(nr, 'airline_section_c', '%f%m')
      call setwinvar(nr, '&statusline', airline#get_statusline(nr, 0))
    endif
  endfor

  " check for other plugin overrides first
  if !exists('w:airline_section_c')
    let w:airline_section_c = '%{bufferline#refresh_status()}'.bufferline#get_status_string()
  endif
endfunction

function! airline#extensions#bufferline#init(ext)
  highlight AlBl_active gui=bold cterm=bold term=bold
  highlight link AlBl_inactive airline_c
  let g:bufferline_inactive_highlight = 'AlBl_inactive'
  let g:bufferline_active_highlight = 'AlBl_active'
  let g:bufferline_active_buffer_left = ''
  let g:bufferline_active_buffer_right = ''
  let g:bufferline_separator = ' '

  if g:airline_section_c == '%f%m'
    call a:ext.add_statusline_func('airline#extensions#bufferline#apply')
  endif
endfunction