Dynamic filename width

Consider the following minimal init.vim file:

let $DOTVIM = expand('$HOME/.config/nvim')

set runtimepath+=$DOTVIM/bundle/repos/github.com/Shougo/defx.nvim
filetype plugin indent on

call defx#custom#option('_', {
            \ 'winwidth': 30,
            \ 'split': 'vertical',
            \ 'direction': 'topleft',
            \ })
call defx#custom#column('filename', {
            \ 'min_width': 20,
            \ 'max_width': 20,
            \ })
nnoremap <C-l> <C-w>2>

Now, as in the GIF, do

1. Open and run :Defx ~/Desktop/bar where in the bar directory you have a file with a really long name such as asadjaslkdasdjaslkdasjdkladakl.txt
2. Once in the Defx window press <C-l> to increase the window width.

After 2. the Defx window width increases but the filename is still truncated. Can a new feature be added such that the filename width also increase dynamically with the window width? (vimfiler had this behaviour)

[Shougo]

You can improve the documentation. The PR is welcome.

[petobens]

I meant that the docs were not clear about what max_width_percent represents (at least for me) and whether we should use it over or combined with max_width. Thanks for the help.