Disable Lightline on Nerdtree

Question

I would like to disable or hide Lightline (i.e. vim's statusline) when my cursor is in Nerdtree, while keeping it activated for other buffers.

Here is what I mean:

How can I achieve this?

Lightline's developper says it is not possible with Lightline itself : issue 193, issue 76

So I tried setlocal statusline=%#Normal# when I BufEnter nerdtree filetype, as suggested here :

augroup filetype_nerdtree
    autocmd!
    autocmd BufEnter,FileType nerdtree setlocal statusline=%#Normal#
augroup END

... which seems to work only when I toggle Nerdtree (:NERDTreeToggle). As soon I move my cursor to another buffer, Lightline fills vim's statusline up again with whatever I put in my g:lightline variable (in both Nerdreee and other buffers).

I use neovim 0.3.8.

Answer 1

It's a hack, but you could try this:

augroup filetype_nerdtree
    au!
    au FileType nerdtree call s:disable_lightline_on_nerdtree()
    au WinEnter,BufWinEnter,TabEnter * call s:disable_lightline_on_nerdtree()
augroup END

fu s:disable_lightline_on_nerdtree() abort
    let nerdtree_winnr = index(map(range(1, winnr('$')), {_,v -> getbufvar(winbufnr(v), '&ft')}), 'nerdtree') + 1
    call timer_start(0, {-> nerdtree_winnr && setwinvar(nerdtree_winnr, '&stl', '%#Normal#')})
endfu

---

I'm still trying to understand what your snippet do because I am new to vim scripting. But I guess it basically sets window's statusline to%#Normal# whenever the corresponding buffer is equal to 'nerdtree', on WinLeave and TabEnter events, does it ?

Yes, that's what it does. Although, now I think that WinEnter, BufWinEnter and TabEnter is a better set of events.

This displays the number of the last window in the current tab page:

:echo winnr('$')

This displays the numbers of all the windows in the current tab page, as a list:

:echo range(1, winnr('$'))

This displays the filetypes of the buffers displayed in all the windows of the current tab page:

                                   ┌ iterates over the numbers of the windows
                                   │              ┌ evaluates to the number of the buffer displayed in the window whose number is v
                                   │              ├─────────┐
:echo map(range(1, winnr('$')), {_,v -> getbufvar(winbufnr(v), '&ft')})
                                        ├───────────────────────────┘
                                        └ evaluates to the filetype of the buffer whose number is winbufnr(v)

This displays the number of the window displaying a nerdtree buffer (or 0 if there is none):

:echo index(map(range(1, winnr('$')), {_,v -> getbufvar(winbufnr(v), '&ft')}), 'nerdtree') + 1

Finally, this sets the local value of the 'statusline' option bound to the window displaying the nerdtree buffer to %#Normal#:

:call setwinvar(index(map(range(1, winnr('$')), {_,v -> getbufvar(winbufnr(v), '&ft')}), 'nerdtree') + 1, '&stl', '%#Normal#')

Now you could execute this last function call directly from an autocmd, but there would still be 2 issues:

1. the function would be called even when there is no nerdtree buffer displayed in the tab page, which would disable the status line in the current window
2. Lightline would still update the status line contents of the nerdtree window after your function call, undoing your reset

To fix 1., you need a guard which makes sure that a window is currently displaying a nerdtree buffer:

let nerdtree_winnr = index(map(range(1, winnr('$')), {_,v -> getbufvar(winbufnr(v), '&ft')}), 'nerdtree') + 1
if nerdtree_winnr
    call setwinvar(nerdtree_winnr, '&stl', '%#Normal#')
endif

To fix 2., you need to delay the function call until Lightline has finished updating all the status lines. You can do so with a timer:

call timer_start(0, {-> nerdtree_winnr && setwinvar(nerdtree_winnr, '&stl', '%#Normal#')})
     ^^^^^^^^^^^        ^^^^^^^^^^^^^^^^^
     timer              guard

---

You can make the nesting of function calls inside index() a little more readable, using the method call operator -> (introduced in 8.1.1803):

let nerdtree_winnr = winnr('$')->range()->map({_,v -> winbufnr(v+1)->getbufvar('&ft')})->index('nerdtree') + 1

---

It works very well, I don't see any flickering.

I can definitely see some flickering. If – in the future – you do too, try to replace the timer with a one-shot autocmd listening to the SafeState event (introduced in 8.1.2044):

let nerdtree_winnr = index(map(range(1, winnr('$')), {_,v -> getbufvar(winbufnr(v), '&ft')}), 'nerdtree') + 1
if nerdtree_winnr
    exe 'au SafeState * ++once call setwinvar('..nerdtree_winnr..', "&stl", "%#Normal#")'
    "                   ^^^^^^
    "                   fire only once
endif

During my limited tests, it seemed to fix the issue.

---

If one day you decide to use your own status line, you could use this template to achieve a similar effect:

filetype on
set ls=2
fu s:snr() abort
    return matchstr(expand('<sfile>'), '.*\zs<SNR>\d\+_')
endfu
let s:snr = get(s:, 'snr', s:snr())
let &stl = '%!'..s:snr..'stl()'
fu s:stl() abort
    return getbufvar(winbufnr(g:statusline_winid), '&ft', '') is# 'nerdtree'
        \ ? '%#Normal#'
        \ : '...'
    "        ^^^
    "        here, write the contents of your status line for filetypes other than nerdtree
endfu

It requires the patch 8.1.1372 to be able to inspect g:statusline_winid. The latter is a temporary global variable which contains the ID of the window to which the status line currently being drawn belongs.

---

Note that neither the method call operator ->, nor the SafeState event, nor the g:statusline_winid variable are available in Nvim.

If you know C, you could try to port the relevant Vim patches.

---

For more info, see:

:h index()
:h map()
:h range()
:h winnr()
:h getbufvar()
:h winbufnr()
:h setwinvar()
:h timer_start()
:h lambda
:h SafeState
:h autocmd-once
:h g:statusline_winid

Answer 2

Of course, your attempt won't work, because Lightline forcefully updates status line content on many auto events. That's quite obvious from its code and was clearly stated by the author in the issues you've quoted.

The only solution is to exclude some specific buffers from such update, but, again, as the author said he is not going to do so for several reasons.

Therefore, you have either (1) fork Lightline and add such functionality yourself, or (2) drop it and build a status line of your own, preferably without any tricky event-driven auto-updates, so Vim can manage everything by himself (using expression re-evaluation).

Personally, I prefer (2) even though Vim is not perfect and things may go out of sync on rare occasions.