convert the highlighter into a singleton.

autoload/airline.vim

@@ -4,7 +4,6 @@
 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)
@@ -27,7 +26,7 @@ function! airline#add_inactive_statusline_func(name)
 endfunction
 
 function! airline#load_theme()
-  call s:highlighter.load_theme()
+  call airline#highlighter#load_theme()
   call airline#extensions#load_theme()
 endfunction
 
@@ -116,7 +115,7 @@ function! airline#update_statusline()
 endfunction
 
 function! s:invoke_funcrefs(context, funcrefs)
-  let builder = airline#builder#new(a:context, s:highlighter)
+  let builder = airline#builder#new(a:context)
   let err = airline#util#exec_funcrefs(a:funcrefs, builder, a:context)
   if err == 0
     call setwinvar(a:context.winnr, '&statusline', airline#get_statusline(builder, a:context.winnr, a:context.active))
@@ -152,7 +151,7 @@ function! airline#check_mode()
 
   let mode_string = join(l:mode)
   if get(w:, 'airline_lastmode', '') != mode_string
-    call s:highlighter.highlight(l:mode)
+    call airline#highlighter#highlight(l:mode)
     let w:airline_lastmode = mode_string
   endif
   return ''

autoload/airline/builder.vim

@@ -10,7 +10,7 @@ endfunction
 
 function! s:prototype.add_section(group, contents)
   if self._curgroup != ''
-    call self._highlighter.add_separator(self._curgroup, a:group, self._side)
+    call airline#highlighter#add_separator(self._curgroup, a:group, self._side)
     let self._line .= '%#'.self._curgroup.'_to_'.a:group.'#'
     let self._line .= self._side ? g:airline_left_sep : g:airline_right_sep
   endif
@@ -30,10 +30,9 @@ function! s:prototype.build()
   return self._line
 endfunction
 
-function! airline#builder#new(context, highlighter)
+function! airline#builder#new(context)
   let builder = copy(s:prototype)
   let builder._context = a:context
-  let builder._highlighter = a:highlighter
   let builder._side = 1
   let builder._curgroup = ''
   let builder._line = '%{airline#check_mode()}'

autoload/airline/highlighter.vim

@@ -2,6 +2,7 @@
 " vim: et ts=2 sts=2 sw=2
 
 let s:is_win32term = (has('win32') || has('win64')) && !has('gui_running')
+let s:separators = {}
 
 function! s:gui2cui(rgb, fallback)
   if a:rgb == ''
@@ -42,38 +43,31 @@ function! s:exec_separator(dict, from, to, inverse, suffix)
   call airline#highlighter#exec(group, colors)
 endfunction
 
-function! airline#highlighter#new()
-  let highlighter = {}
-  let highlighter._separators = {}
-
-  function! highlighter.load_theme()
-    call self.highlight(['inactive'])
-    call self.highlight(['normal'])
-  endfunction
-
-  function! highlighter.add_separator(from, to, inverse)
-    let self._separators[a:from.a:to] = [a:from, a:to, a:inverse]
-  endfunction
-
-  function! highlighter.highlight(modes)
-    " draw the base mode, followed by any overrides
-    let mapped = map(a:modes, 'v:val == a:modes[0] ? v:val : a:modes[0]."_".v:val')
-    let suffix = a:modes[0] == 'inactive' ? '_inactive' : ''
-    for mode in mapped
-      if exists('g:airline#themes#{g:airline_theme}#palette[mode]')
-        let dict = g:airline#themes#{g:airline_theme}#palette[mode]
-        for kvp in items(dict)
-          call airline#highlighter#exec(kvp[0].suffix, kvp[1])
-        endfor
-
-        " TODO: optimize this
-        for sep in items(self._separators)
-          call <sid>exec_separator(dict, sep[1][0], sep[1][1], sep[1][2], suffix)
-        endfor
-      endif
-    endfor
-  endfunction
-
-  return highlighter
+function! airline#highlighter#load_theme()
+  call airline#highlighter#highlight(['inactive'])
+  call airline#highlighter#highlight(['normal'])
+endfunction
+
+function! airline#highlighter#add_separator(from, to, inverse)
+  let s:separators[a:from.a:to] = [a:from, a:to, a:inverse]
+endfunction
+
+function! airline#highlighter#highlight(modes)
+  " draw the base mode, followed by any overrides
+  let mapped = map(a:modes, 'v:val == a:modes[0] ? v:val : a:modes[0]."_".v:val')
+  let suffix = a:modes[0] == 'inactive' ? '_inactive' : ''
+  for mode in mapped
+    if exists('g:airline#themes#{g:airline_theme}#palette[mode]')
+      let dict = g:airline#themes#{g:airline_theme}#palette[mode]
+      for kvp in items(dict)
+        call airline#highlighter#exec(kvp[0].suffix, kvp[1])
+      endfor
+
+      " TODO: optimize this
+      for sep in items(s:separators)
+        call <sid>exec_separator(dict, sep[1][0], sep[1][1], sep[1][2], suffix)
+      endfor
+    endif
+  endfor
 endfunction