Lightline.vim: How to show buffer number with filename?

[ayutheos]

How do I make lightline display buffer number together with filename e.g. 3:filename.txt in both active and inactive windows?

[itchyny]

let g:lightline = {
    \ 'component': {
    \   'filename': '%n:%t'
    \ }
    \ }

[ayutheos]

Thanks for the quick reply. I forgot to add that I'm using your sample setting with named components. What do I need to modify to add the buffer number?

function! MyFilename()
  let fname = expand('%:t')
  return fname == 'ControlP' ? g:lightline.ctrlp_item :
        \ ('' != MyReadonly() ? MyReadonly() . ' ' : '') .
        \ ('' != fname ? fname : '[No Name]') .
        \ ('' != MyModified() ? ' ' . MyModified() : '')
endfunction

[itchyny]

function! MyFilename()
  let fname = expand('%:t')
  let nr = bufnr('')
  return nr . ':' . (fname == 'ControlP' ? g:lightline.ctrlp_item :
        \ ('' != MyReadonly() ? MyReadonly() . ' ' : '') .
        \ ('' != fname ? fname : '[No Name]') .
        \ ('' != MyModified() ? ' ' . MyModified() : ''))
endfunction

[ayutheos]

Thanks! :)