Pass the current window as a parameter to the render method

This change simplifies the code somewhat as the BufLeave, etc. autocmds
aren't required anymore.

plugin/vim/powerline.vim

@@ -20,22 +20,20 @@ else
 	endfunction
 endif
 
-function! Powerline(winnr)
+function! Powerline(winnr, current)
-	return s:pyeval('pl.renderer.render('. a:winnr .')')
+	return s:pyeval('pl.renderer.render('. a:winnr .', '. a:current .')')
 endfunction
 
-function! s:UpdateAllWindows()
+function! s:UpdateWindows()
+	if ! exists('w:window_id')
+		let w:window_id = s:pyeval('str(uuid.uuid4())')
+	endif
 	for winnr in range(1, winnr('$'))
-		if getwinvar(winnr, 'window_id') is# ''
+		call setwinvar(winnr, '&statusline', '%!Powerline('. winnr .', '. (w:window_id == getwinvar(winnr, 'window_id')) .')')
-			call setwinvar(winnr, 'window_id', s:pyeval('str(uuid.uuid4())'))
-		endif
-
-		call setwinvar(winnr, '&statusline', '%!Powerline('. winnr .')')
 	endfor
 endfunction
 
 augroup Powerline
 	autocmd!
-	autocmd BufEnter,BufWinEnter,WinEnter * let w:current = 1 | call s:UpdateAllWindows()
+	autocmd BufEnter,BufWinEnter,WinEnter * call s:UpdateWindows()
-	autocmd BufLeave,BufWinLeave,WinLeave * let w:current = 0
 augroup END

powerline/ext/vim/renderer.py

@@ -21,16 +21,14 @@ class VimRenderer(Renderer):
 		self.hl_groups = {}
 		self.window_cache = {}
 
-	def render(self, winnr):
+	def render(self, winnr, current):
 		'''Render all segments.
 
 		This method handles replacing of the percent placeholder for vim
 		statuslines, and it caches segment contents which are retrieved and
 		used in non-current windows.
 		'''
-		current = vim_getwinvar(winnr, 'current')
 		window_id = vim_getwinvar(winnr, 'window_id')
-
 		winwidth = vim_winwidth(winnr)
 
 		if current: