Defer create_renderer (and thus thread creation) until .render call

May fix problem discussed in #397

Also fix documentation for Powerline.render().

powerline/__init__.py

@@ -113,7 +113,12 @@ class Powerline(object):
 		self.find_config_file = lambda cfg_path: find_config_file(config_paths, cfg_path)
 
 		self.cr_kwargs_lock = Lock()
-		self.create_renderer_kwargs = {}
+		self.create_renderer_kwargs = {
+			'load_main': True,
+			'load_colors': True,
+			'load_colorscheme': True,
+			'load_theme': True,
+		}
 		self.shutdown_event = shutdown_event or Event()
 		self.config_loader = config_loader or ConfigLoader(shutdown_event=self.shutdown_event)
 
@@ -123,8 +128,6 @@ class Powerline(object):
 		self.prev_ext_config = None
 		self.pl = None
 
-		self.create_renderer(load_main=True, load_colors=True, load_colorscheme=True, load_theme=True)
-
 	def create_renderer(self, load_main=False, load_colors=False, load_colorscheme=False, load_theme=False):
 		'''(Re)create renderer object. Can be used after Powerline object was 
 		successfully initialized. If any of the below parameters except 
@@ -342,18 +345,25 @@ class Powerline(object):
 		'''
 		return None
 
-	def render(self, *args, **kwargs):
-		'''Lock renderer from modifications and pass all arguments further to 
-		``self.renderer.render()``.
-		'''
+	def update_renderer(self):
+		'''Updates/creates a renderer if needed.'''
+		create_renderer_kwargs = None
 		with self.cr_kwargs_lock:
 			if self.create_renderer_kwargs:
-				try:
-					self.create_renderer(**self.create_renderer_kwargs)
-				except Exception as e:
-					self.pl.exception('Failed to create renderer: {0}', str(e))
-				finally:
-					self.create_renderer_kwargs.clear()
+				create_renderer_kwargs = self.create_renderer_kwargs.copy()
+		if create_renderer_kwargs:
+			try:
+				self.create_renderer(**create_renderer_kwargs)
+			except Exception as e:
+				self.pl.exception('Failed to create renderer: {0}', str(e))
+			finally:
+				self.create_renderer_kwargs.clear()
+
+	def render(self, *args, **kwargs):
+		'''Update/create renderer if needed and pass all arguments further to 
+		``self.renderer.render()``.
+		'''
+		self.update_renderer()
 		return self.renderer.render(*args, **kwargs)
 
 	def shutdown(self):

powerline/vim.py

@@ -46,6 +46,7 @@ class VimPowerline(Powerline):
 			``True`` if theme was added successfully and ``False`` if theme with 
 			the same matcher already exists.
 		'''
+		self.update_renderer()
 		key = self.get_matcher(key)
 		try:
 			self.renderer.add_local_theme(key, {'config': config})

tests/test_config_reload.py

@@ -128,8 +128,8 @@ class TestConfigReload(TestCase):
 	def test_reload_main(self):
 		with get_powerline(run_once=False) as p:
 			with replace_item(globals(), 'config', deepcopy(config)):
-				self.assertAccessEvents('config', 'colors', 'colorschemes/test/default', 'themes/test/default')
 				self.assertEqual(p.render(), '<1 2 1> s<2 4 False>>><3 4 4>g<4 False False>>><None None None>')
+				self.assertAccessEvents('config', 'colors', 'colorschemes/test/default', 'themes/test/default')
 
 				config['config']['common']['spaces'] = 1
 				add_watcher_events(p, 'config')