add inactive statusline funcrefs into the pipeline.

autoload/airline.vim

@@ -5,6 +5,7 @@ let g:airline_statusline_funcrefs = get(g:, 'airline_statusline_funcrefs', [])
 
 let s:sections = ['a','b','c','gutter','x','y','z','warning']
 let s:highlighter = airline#highlighter#new()
+let s:inactive_funcrefs = []
 
 function! airline#add_statusline_func(name)
   call airline#add_statusline_funcref(function(a:name))
@@ -21,6 +22,10 @@ function! airline#remove_statusline_func(name)
   endif
 endfunction
 
+function! airline#add_inactive_statusline_func(name)
+  call add(s:inactive_funcrefs, function(a:name))
+endfunction
+
 function! airline#load_theme()
   call s:highlighter.load_theme()
   call airline#extensions#load_theme()
@@ -96,25 +101,27 @@ function! airline#update_statusline()
   for nr in filter(range(1, winnr('$')), 'v:val != winnr()')
     call setwinvar(nr, 'airline_active', 0)
     let context = { 'winnr': nr, 'active': 0 }
-    let builder = airline#builder#new(context, s:highlighter)
-    call setwinvar(nr, '&statusline', airline#get_statusline(builder, nr, 0))
+    call s:invoke_funcrefs(context, s:inactive_funcrefs)
   endfor
 
-  let w:airline_active = 1
-
   unlet! w:airline_render_left
   unlet! w:airline_render_right
   for section in s:sections
     unlet! w:airline_section_{section}
   endfor
 
+  let w:airline_active = 1
   let context = { 'winnr': winnr(), 'active': 1 }
-  let builder = airline#builder#new(context, s:highlighter)
-  let err = airline#util#exec_funcrefs(g:airline_statusline_funcrefs, builder)
+  call s:invoke_funcrefs(context, g:airline_statusline_funcrefs)
+endfunction
+
+function! s:invoke_funcrefs(context, funcrefs)
+  let builder = airline#builder#new(a:context, s:highlighter)
+  let err = airline#util#exec_funcrefs(a:funcrefs, builder, a:context)
   if err == 0
-    call setwinvar(winnr(), '&statusline', airline#get_statusline(builder, winnr(), 1))
+    call setwinvar(a:context.winnr, '&statusline', airline#get_statusline(builder, a:context.winnr, a:context.active))
   elseif err == 1
-    call setwinvar(winnr(), '&statusline', builder.build())
+    call setwinvar(a:context.winnr, '&statusline', builder.build())
   endif
 endfunction
 

autoload/airline/extensions.vim

@@ -8,6 +8,9 @@ endfunction
 function! s:ext.add_statusline_funcref(function) dict
   call airline#add_statusline_funcref(a:function)
 endfunction
+function! s:ext.add_inactive_statusline_func(name) dict
+  call airline#add_inactive_statusline_func(a:name)
+endfunction
 
 let s:script_path = expand('<sfile>:p:h')
 

doc/airline.txt

@@ -302,6 +302,12 @@ statuslines to your liking.  Here is an example: >
 <
 The second variable is the context, which is a dictionary containing various
 values such as whether the statusline is active or not, and the window number.
+>
+  context = {
+    'winnr': 'the window number for the statusline',
+    'active': 'whether the window is active or not',
+  }
+<
 
                                              *airline-pipeline-return-codes*
 The pipeline accepts various return codes and can be used to determine the