Allow users to define custom before/after callbacks (#3)

README.md

@@ -26,6 +26,31 @@ Configuration
 - `g:goyo_margin_top` (default: 4)
 - `g:goyo_margin_bottom` (default: 4)
 - `g:goyo_linenr` (default: 0)
+- `g:goyo_callbacks` ([before_funcref, after_funcref])
+
+### Callbacks
+
+By default, [vim-airline](https://github.com/bling/vim-airline),
+[vim-powerline](https://github.com/Lokaltog/vim-powerline),
+[powerline](https://github.com/Lokaltog/powerline), and
+[vim-gitgutter](https://github.com/airblade/vim-gitgutter) are temporarily
+disabled while in Goyo mode.
+
+If you have other plugins that you want to disable/enable, or if you want to
+change the default settings of Goyo window, you can define before and after
+callbacks as follows in your .vimrc.
+
+```vim
+function! s:goyo_before()
+  "
+endfunction
+
+function! s:goyo_after()
+  "
+endfunction
+
+let g:goyo_callbacks = [function('s:goyo_before'), function('s:goyo_after')]
+```
 
 Inspiration
 -----------

plugin/goyo.vim

@@ -168,6 +168,10 @@ function! s:goyo_on(width)
 
   let &statusline = repeat(' ', winwidth(0))
 
+  if exists('g:goyo_callbacks[0]')
+    call g:goyo_callbacks[0]()
+  endif
+
   augroup goyo
     autocmd!
     autocmd BufWinLeave <buffer> call s:goyo_off()
@@ -231,6 +235,10 @@ function! s:goyo_off()
   if exists('#Powerline')
     doautocmd Powerline ColorScheme
   endif
+
+  if exists('g:goyo_callbacks[1]')
+    call g:goyo_callbacks[1]()
+  endif
 endfunction
 
 function! s:goyo(...)