From c570a9806513784341a7cb7caa72f4a8957d4c78 Mon Sep 17 00:00:00 2001
From: ZyX <kp-pav@yandex.ru>
Date: Sat, 28 Jun 2014 19:01:12 +0400
Subject: [PATCH] Add watcher option

Ref #818
---
 docs/source/configuration.rst  | 13 +++++
 powerline/__init__.py          | 46 +++++++++++-----
 powerline/lib/config.py        | 41 +++++++++++++-
 powerline/lib/file_watcher.py  | 52 ++++++++++++------
 powerline/lib/vcs/__init__.py  | 36 +++++++------
 powerline/lib/vcs/bzr.py       | 20 +++++--
 powerline/lib/vcs/git.py       | 97 ++++++++++++++++------------------
 powerline/lib/vcs/mercurial.py | 22 ++++++--
 powerline/lint/__init__.py     |  5 +-
 powerline/lint/inspect.py      |  2 +
 powerline/segment.py           | 14 +++--
 powerline/segments/common.py   |  7 +--
 powerline/segments/vim.py      | 12 +++--
 powerline/theme.py             |  7 ++-
 tests/lib/config_mock.py       |  7 ++-
 tests/test_config_reload.py    |  1 +
 tests/test_configuration.py    |  3 +-
 tests/test_lib.py              | 23 ++++----
 tests/test_segments.py         | 60 +++++++++++++--------
 19 files changed, 313 insertions(+), 155 deletions(-)

diff --git a/docs/source/configuration.rst b/docs/source/configuration.rst
index 0ab55695..b8e70ce6 100644
--- a/docs/source/configuration.rst
+++ b/docs/source/configuration.rst
@@ -128,6 +128,19 @@ Common configuration is a subdictionary that is a value of ``common`` key in
     letters, Cyrillic letters). Valid values: any positive integer; it is 
     suggested that you only set it to 1 (default) or 2.
 
+``watcher``
+    Select filesystem watcher. Variants are
+
+    =======  ===================================
+    Variant  Description
+    =======  ===================================
+    auto     Selects most performant watcher.
+    inotify  Select inotify watcher. Linux only.
+    stat     Select stat-based polling watcher.
+    =======  ===================================
+
+    Default is ``auto``.
+
 .. _config-common-additional_escapes:
 
 ``additional_escapes``
diff --git a/powerline/__init__.py b/powerline/__init__.py
index bc023f61..83678be4 100644
--- a/powerline/__init__.py
+++ b/powerline/__init__.py
@@ -63,7 +63,7 @@ class PowerlineLogger(object):
 _fallback_logger = None
 
 
-def _get_fallback_logger():
+def get_fallback_logger():
 	global _fallback_logger
 	if _fallback_logger:
 		return _fallback_logger
@@ -179,15 +179,31 @@ class Powerline(object):
 			self.common_config = config['common']
 			if self.common_config != self.prev_common_config:
 				common_config_differs = True
+
 				self.prev_common_config = self.common_config
-				self.common_config['paths'] = [os.path.expanduser(path) for path in self.common_config.get('paths', [])]
+
+				self.common_config.setdefault('paths', [])
+				self.common_config.setdefault('watcher', 'auto')
+				self.common_config.setdefault('log_level', 'WARNING')
+				self.common_config.setdefault('log_format', '%(asctime)s:%(levelname)s:%(message)s')
+				self.common_config.setdefault('term_truecolor', False)
+				self.common_config.setdefault('ambiwidth', 1)
+				self.common_config.setdefault('additional_escapes', None)
+				self.common_config.setdefault('reload_config', True)
+				self.common_config.setdefault('interval', None)
+				self.common_config.setdefault('log_file', None)
+
+				self.common_config['paths'] = [
+					os.path.expanduser(path) for path in self.common_config['paths']
+				]
+
 				self.import_paths = self.common_config['paths']
 
 				if not self.logger:
-					log_format = self.common_config.get('log_format', '%(asctime)s:%(levelname)s:%(message)s')
+					log_format = self.common_config['log_format']
 					formatter = logging.Formatter(log_format)
 
-					level = getattr(logging, self.common_config.get('log_level', 'WARNING'))
+					level = getattr(logging, self.common_config['log_level'])
 					handler = self.get_log_handler()
 					handler.setLevel(level)
 					handler.setFormatter(formatter)
@@ -198,15 +214,17 @@ class Powerline(object):
 
 				if not self.pl:
 					self.pl = PowerlineLogger(self.use_daemon_threads, self.logger, self.ext)
-					if not self.config_loader.pl:
-						self.config_loader.pl = self.pl
+					self.config_loader.pl = self.pl
+
+				if not self.run_once:
+					self.config_loader.set_watcher(self.common_config['watcher'])
 
 				self.renderer_options.update(
 					pl=self.pl,
-					term_truecolor=self.common_config.get('term_truecolor', False),
-					ambiwidth=self.common_config.get('ambiwidth', 1),
-					tmux_escape=self.common_config.get('additional_escapes') == 'tmux',
-					screen_escape=self.common_config.get('additional_escapes') == 'screen',
+					term_truecolor=self.common_config['term_truecolor'],
+					ambiwidth=self.common_config['ambiwidth'],
+					tmux_escape=self.common_config['additional_escapes'] == 'tmux',
+					screen_escape=self.common_config['additional_escapes'] == 'screen',
 					theme_kwargs={
 						'ext': self.ext,
 						'common_config': self.common_config,
@@ -215,8 +233,8 @@ class Powerline(object):
 					},
 				)
 
-				if not self.run_once and self.common_config.get('reload_config', True):
-					interval = self.common_config.get('interval', None)
+				if not self.run_once and self.common_config['reload_config']:
+					interval = self.common_config['interval']
 					self.config_loader.set_interval(interval)
 					self.run_loader_update = (interval is None)
 					if interval is not None and not self.config_loader.is_alive():
@@ -278,7 +296,7 @@ class Powerline(object):
 
 		:return: logging.Handler subclass.
 		'''
-		log_file = self.common_config.get('log_file', None)
+		log_file = self.common_config['log_file']
 		if log_file:
 			log_file = os.path.expanduser(log_file)
 			log_dir = os.path.dirname(log_file)
@@ -473,5 +491,5 @@ class Powerline(object):
 	def exception(self, msg, *args, **kwargs):
 		if 'prefix' not in kwargs:
 			kwargs['prefix'] = 'powerline'
-		pl = getattr(self, 'pl', None) or _get_fallback_logger()
+		pl = getattr(self, 'pl', None) or get_fallback_logger()
 		return pl.exception(msg, *args, **kwargs)
diff --git a/powerline/lib/config.py b/powerline/lib/config.py
index de2d9902..8dd50afe 100644
--- a/powerline/lib/config.py
+++ b/powerline/lib/config.py
@@ -28,14 +28,41 @@ class DummyWatcher(object):
 		pass
 
 
+class DeferredWatcher(object):
+	def __init__(self, *args, **kwargs):
+		self.args = args
+		self.kwargs = kwargs
+		self.calls = []
+
+	def __call__(self, *args, **kwargs):
+		self.calls.append(('__call__', args, kwargs))
+
+	def watch(self, *args, **kwargs):
+		self.calls.append(('watch', args, kwargs))
+
+	def unwatch(self, *args, **kwargs):
+		self.calls.append(('unwatch', args, kwargs))
+
+	def transfer_calls(self, watcher):
+		for attr, args, kwargs in self.calls:
+			getattr(watcher, attr)(*args, **kwargs)
+
+
 class ConfigLoader(MultiRunnedThread):
-	def __init__(self, shutdown_event=None, watcher=None, load=load_json_config, run_once=False):
+	def __init__(self, shutdown_event=None, watcher=None, watcher_type=None, load=load_json_config, run_once=False):
 		super(ConfigLoader, self).__init__()
 		self.shutdown_event = shutdown_event or Event()
 		if run_once:
 			self.watcher = DummyWatcher()
+			self.watcher_type = 'dummy'
 		else:
-			self.watcher = watcher or create_file_watcher()
+			self.watcher = watcher or DeferredWatcher()
+			if watcher:
+				if not watcher_type:
+					raise ValueError('When specifying watcher you must also specify watcher type')
+				self.watcher_type = watcher_type
+			else:
+				self.watcher_type = 'deferred'
 		self._load = load
 
 		self.pl = None
@@ -47,6 +74,16 @@ class ConfigLoader(MultiRunnedThread):
 		self.missing = defaultdict(set)
 		self.loaded = {}
 
+	def set_watcher(self, watcher_type, force=False):
+		if watcher_type == self.watcher_type:
+			return
+		watcher = create_file_watcher(self.pl, watcher_type)
+		with self.lock:
+			if self.watcher_type == 'deferred':
+				self.watcher.transfer_calls(watcher)
+			self.watcher = watcher
+			self.watcher_type = watcher_type
+
 	def set_pl(self, pl):
 		self.pl = pl
 
diff --git a/powerline/lib/file_watcher.py b/powerline/lib/file_watcher.py
index 21524e3b..ffb337f2 100644
--- a/powerline/lib/file_watcher.py
+++ b/powerline/lib/file_watcher.py
@@ -19,8 +19,6 @@ def realpath(path):
 
 
 class INotifyWatch(INotify):
-	is_stat_based = False
-
 	def __init__(self, expire_time=10):
 		super(INotifyWatch, self).__init__()
 		self.watches = {}
@@ -147,8 +145,6 @@ class INotifyWatch(INotify):
 
 
 class StatWatch(object):
-	is_stat_based = True
-
 	def __init__(self):
 		self.watches = {}
 		self.lock = RLock()
@@ -184,29 +180,51 @@ class StatWatch(object):
 			self.watches.clear()
 
 
-def create_file_watcher(use_stat=False, expire_time=10):
+def create_file_watcher(pl, watcher_type='auto', expire_time=10):
 	'''
-	Create an object that can watch for changes to specified files. To use:
+	Create an object that can watch for changes to specified files
 
-	watcher = create_file_watcher()
-	watcher(path1) # Will return True if path1 has changed since the last time this was called. Always returns True the first time.
-	watcher.unwatch(path1)
+	Use ``.__call__()`` method of the returned object to start watching the file 
+	or check whether file has changed since last call.
 
-	Uses inotify if available, otherwise tracks mtimes. expire_time is the
-	number of minutes after the last query for a given path for the inotify
-	watch for that path to be automatically removed. This conserves kernel
+	Use ``.unwatch()`` method of the returned object to stop watching the file.
+
+	Uses inotify if available, otherwise tracks mtimes. expire_time is the 
+	number of minutes after the last query for a given path for the inotify 
+	watch for that path to be automatically removed. This conserves kernel 
 	resources.
+
+	:param PowerlineLogger pl:
+		Logger.
+	:param str watcher_type:
+		One of ``inotify`` (linux only), ``stat``, ``auto``. Determines what 
+		watcher will be used. ``auto`` will use ``inotify`` if available.
+	:param int expire_time:
+		Number of minutes since last ``.__call__()`` before inotify watcher will 
+		stop watching given file.
 	'''
-	if use_stat:
+	if watcher_type == 'stat':
+		pl.debug('Using requested stat-based watcher', prefix='watcher')
 		return StatWatch()
-	try:
+	if watcher_type == 'inotify':
+		# Explicitly selected inotify watcher: do not catch INotifyError then.
+		pl.debug('Using requested inotify watcher', prefix='watcher')
 		return INotifyWatch(expire_time=expire_time)
-	except INotifyError:
-		pass
+
+	if sys.platform.startswith('linux'):
+		try:
+			pl.debug('Trying to use inotify watcher', prefix='watcher')
+			return INotifyWatch(expire_time=expire_time)
+		except INotifyError:
+			pl.info('Failed to create inotify watcher', prefix='watcher')
+
+	pl.debug('Using stat-based watcher')
 	return StatWatch()
 
+
 if __name__ == '__main__':
-	watcher = create_file_watcher()
+	from powerline import get_fallback_logger
+	watcher = create_file_watcher(get_fallback_logger())
 	print ('Using watcher: %s' % watcher.__class__.__name__)
 	print ('Watching %s, press Ctrl-C to quit' % sys.argv[-1])
 	watcher.watch(sys.argv[-1])
diff --git a/powerline/lib/vcs/__init__.py b/powerline/lib/vcs/__init__.py
index ff971c5d..1029bc3f 100644
--- a/powerline/lib/vcs/__init__.py
+++ b/powerline/lib/vcs/__init__.py
@@ -23,22 +23,20 @@ def generate_directories(path):
 _file_watcher = None
 
 
-def file_watcher():
+def file_watcher(create_watcher):
 	global _file_watcher
 	if _file_watcher is None:
-		from powerline.lib.file_watcher import create_file_watcher
-		_file_watcher = create_file_watcher()
+		_file_watcher = create_watcher()
 	return _file_watcher
 
 
 _branch_watcher = None
 
 
-def branch_watcher():
+def branch_watcher(create_watcher):
 	global _branch_watcher
 	if _branch_watcher is None:
-		from powerline.lib.file_watcher import create_file_watcher
-		_branch_watcher = create_file_watcher()
+		_branch_watcher = create_watcher()
 	return _branch_watcher
 
 
@@ -47,11 +45,11 @@ branch_lock = Lock()
 file_status_lock = Lock()
 
 
-def get_branch_name(directory, config_file, get_func):
+def get_branch_name(directory, config_file, get_func, create_watcher):
 	global branch_name_cache
 	with branch_lock:
 		# Check if the repo directory was moved/deleted
-		fw = branch_watcher()
+		fw = branch_watcher(create_watcher)
 		is_watched = fw.is_watched(directory)
 		try:
 			changed = fw(directory)
@@ -117,7 +115,7 @@ class FileStatusCache(dict):
 file_status_cache = FileStatusCache()
 
 
-def get_file_status(directory, dirstate_file, file_path, ignore_file_name, get_func, extra_ignore_files=()):
+def get_file_status(directory, dirstate_file, file_path, ignore_file_name, get_func, create_watcher, extra_ignore_files=()):
 	global file_status_cache
 	keypath = file_path if os.path.isabs(file_path) else os.path.join(directory, file_path)
 	file_status_cache.update_maps(keypath, directory, dirstate_file, ignore_file_name, extra_ignore_files)
@@ -129,7 +127,7 @@ def get_file_status(directory, dirstate_file, file_path, ignore_file_name, get_f
 			return ans
 
 		# Check if any relevant files have changed
-		file_changed = file_watcher()
+		file_changed = file_watcher(create_watcher)
 		changed = False
 		# Check if dirstate has changed
 		try:
@@ -217,7 +215,7 @@ vcs_props = (
 )
 
 
-def guess(path):
+def guess(path, create_watcher):
 	for directory in generate_directories(path):
 		for vcs, vcs_dir, check in vcs_props:
 			repo_dir = os.path.join(directory, vcs_dir)
@@ -227,20 +225,28 @@ def guess(path):
 				try:
 					if vcs not in globals():
 						globals()[vcs] = getattr(__import__('powerline.lib.vcs', fromlist=[vcs]), vcs)
-					return globals()[vcs].Repository(directory)
+					return globals()[vcs].Repository(directory, create_watcher)
 				except:
 					pass
 	return None
 
 
+def get_fallback_create_watcher():
+	from powerline.lib.file_watcher import create_file_watcher
+	from powerline import get_fallback_logger
+	from functools import partial
+	return partial(create_file_watcher, get_fallback_logger(), 'auto')
+
+
 def debug():
 	'''Test run guess(), repo.branch() and repo.status()
 
-	To use run python -c "from powerline.lib.vcs import debug; debug()" 
-	some_file_to_watch '''
+	To use::
+		python -c "from powerline.lib.vcs import debug; debug()" some_file_to_watch.
+	'''
 	import sys
 	dest = sys.argv[-1]
-	repo = guess(os.path.abspath(dest))
+	repo = guess(os.path.abspath(dest), get_fallback_create_watcher)
 	if repo is None:
 		print ('%s is not a recognized vcs repo' % dest)
 		raise SystemExit(1)
diff --git a/powerline/lib/vcs/bzr.py b/powerline/lib/vcs/bzr.py
index 9734572b..f8818bdc 100644
--- a/powerline/lib/vcs/bzr.py
+++ b/powerline/lib/vcs/bzr.py
@@ -39,10 +39,11 @@ state = None
 
 
 class Repository(object):
-	def __init__(self, directory):
+	def __init__(self, directory, create_watcher):
 		if isinstance(directory, bytes):
 			directory = directory.decode(sys.getfilesystemencoding() or sys.getdefaultencoding() or 'utf-8')
 		self.directory = os.path.abspath(directory)
+		self.create_watcher = create_watcher
 
 	def status(self, path=None):
 		'''Return status of repository or file.
@@ -57,8 +58,14 @@ class Repository(object):
 		those returned by bzr status -S
 		'''
 		if path is not None:
-			return get_file_status(self.directory, os.path.join(self.directory, '.bzr', 'checkout', 'dirstate'),
-								path, '.bzrignore', self.do_status)
+			return get_file_status(
+				directory=self.directory,
+				dirstate_file=os.path.join(self.directory, '.bzr', 'checkout', 'dirstate'),
+				file_path=path,
+				ignore_file_name='.bzrignore',
+				get_func=self.do_status,
+				create_watcher=self.create_watcher,
+			)
 		return self.do_status(self.directory, path)
 
 	def do_status(self, directory, path):
@@ -93,4 +100,9 @@ class Repository(object):
 
 	def branch(self):
 		config_file = os.path.join(self.directory, '.bzr', 'branch', 'branch.conf')
-		return get_branch_name(self.directory, config_file, branch_name_from_config_file)
+		return get_branch_name(
+			directory=self.directory,
+			config_file=config_file,
+			get_func=branch_name_from_config_file,
+			create_watcher=self.create_watcher,
+		)
diff --git a/powerline/lib/vcs/git.py b/powerline/lib/vcs/git.py
index 5339ca4e..3bf60562 100644
--- a/powerline/lib/vcs/git.py
+++ b/powerline/lib/vcs/git.py
@@ -6,7 +6,7 @@ import os
 import sys
 import re
 
-from powerline.lib.vcs import get_branch_name as _get_branch_name, get_file_status
+from powerline.lib.vcs import get_branch_name, get_file_status
 from powerline.lib.shell import readlines
 
 
@@ -40,32 +40,57 @@ def git_directory(directory):
 		return path
 
 
-def get_branch_name(base_dir):
-	head = os.path.join(git_directory(base_dir), 'HEAD')
-	return _get_branch_name(base_dir, head, branch_name_from_config_file)
+class GitRepository(object):
+	__slots__ = ('directory', 'create_watcher')
 
+	def __init__(self, directory, create_watcher):
+		self.directory = os.path.abspath(directory)
+		self.create_watcher = create_watcher
 
-def do_status(directory, path, func):
-	if path:
-		gitd = git_directory(directory)
-		# We need HEAD as without it using fugitive to commit causes the
-		# current file's status (and only the current file) to not be updated
-		# for some reason I cannot be bothered to figure out.
-		return get_file_status(
-			directory, os.path.join(gitd, 'index'),
-			path, '.gitignore', func, extra_ignore_files=tuple(os.path.join(gitd, x) for x in ('logs/HEAD', 'info/exclude')))
-	return func(directory, path)
+	def status(self, path=None):
+		'''Return status of repository or file.
+
+		Without file argument: returns status of the repository:
+
+		:First column: working directory status (D: dirty / space)
+		:Second column: index status (I: index dirty / space)
+		:Third column: presence of untracked files (U: untracked files / space)
+		:None: repository clean
+
+		With file argument: returns status of this file. Output is
+		equivalent to the first two columns of "git status --porcelain"
+		(except for merge statuses as they are not supported by libgit2).
+		'''
+		if path:
+			gitd = git_directory(self.directory)
+			# We need HEAD as without it using fugitive to commit causes the
+			# current file's status (and only the current file) to not be updated
+			# for some reason I cannot be bothered to figure out.
+			return get_file_status(
+				directory=self.directory,
+				dirstate_file=os.path.join(gitd, 'index'),
+				file_path=path,
+				ignore_file_name='.gitignore',
+				get_func=self.do_status,
+				create_watcher=self.create_watcher,
+				extra_ignore_files=tuple(os.path.join(gitd, x) for x in ('logs/HEAD', 'info/exclude')),
+			)
+		return self.do_status(self.directory, path)
+
+	def branch(self):
+		head = os.path.join(git_directory(self.directory), 'HEAD')
+		return get_branch_name(
+			directory=self.directory,
+			config_file=head,
+			get_func=branch_name_from_config_file,
+			create_watcher=self.create_watcher,
+		)
 
 
 try:
 	import pygit2 as git
 
-	class Repository(object):
-		__slots__ = ('directory',)
-
-		def __init__(self, directory):
-			self.directory = os.path.abspath(directory)
-
+	class Repository(GitRepository):
 		@staticmethod
 		def ignore_event(path, name):
 			return False
@@ -121,32 +146,8 @@ try:
 						index_column = 'I'
 				r = wt_column + index_column + untracked_column
 				return r if r != '   ' else None
-
-		def status(self, path=None):
-			'''Return status of repository or file.
-
-			Without file argument: returns status of the repository:
-
-			:First column: working directory status (D: dirty / space)
-			:Second column: index status (I: index dirty / space)
-			:Third column: presence of untracked files (U: untracked files / space)
-			:None: repository clean
-
-			With file argument: returns status of this file. Output is
-			equivalent to the first two columns of "git status --porcelain"
-			(except for merge statuses as they are not supported by libgit2).
-			'''
-			return do_status(self.directory, path, self.do_status)
-
-		def branch(self):
-			return get_branch_name(self.directory)
 except ImportError:
-	class Repository(object):
-		__slots__ = ('directory',)
-
-		def __init__(self, directory):
-			self.directory = os.path.abspath(directory)
-
+	class Repository(GitRepository):
 		@staticmethod
 		def ignore_event(path, name):
 			# Ignore changes to the index.lock file, since they happen 
@@ -182,9 +183,3 @@ except ImportError:
 
 				r = wt_column + index_column + untracked_column
 				return r if r != '   ' else None
-
-		def status(self, path=None):
-			return do_status(self.directory, path, self.do_status)
-
-		def branch(self):
-			return get_branch_name(self.directory)
diff --git a/powerline/lib/vcs/mercurial.py b/powerline/lib/vcs/mercurial.py
index 2aa890cd..cebd7960 100644
--- a/powerline/lib/vcs/mercurial.py
+++ b/powerline/lib/vcs/mercurial.py
@@ -18,15 +18,16 @@ def branch_name_from_config_file(directory, config_file):
 
 
 class Repository(object):
-	__slots__ = ('directory', 'ui')
+	__slots__ = ('directory', 'ui', 'create_watcher')
 
 	statuses = 'MARDUI'
 	repo_statuses = (1, 1, 1, 1, 2)
 	repo_statuses_str = (None, 'D ', ' U', 'DU')
 
-	def __init__(self, directory):
+	def __init__(self, directory, create_watcher):
 		self.directory = os.path.abspath(directory)
 		self.ui = ui.ui()
+		self.create_watcher = create_watcher
 
 	def _repo(self, directory):
 		# Cannot create this object once and use always: when repository updates
@@ -47,8 +48,14 @@ class Repository(object):
 		"U"nknown, "I"gnored, (None)Clean.
 		'''
 		if path:
-			return get_file_status(self.directory, os.path.join(self.directory, '.hg', 'dirstate'),
-					path, '.hgignore', self.do_status)
+			return get_file_status(
+				directory=self.directory,
+				dirstate_file=os.path.join(self.directory, '.hg', 'dirstate'),
+				file_path=path,
+				ignore_file_name='.hgignore',
+				get_func=self.do_status,
+				create_watcher=self.create_watcher,
+			)
 		return self.do_status(self.directory, path)
 
 	def do_status(self, directory, path):
@@ -69,4 +76,9 @@ class Repository(object):
 
 	def branch(self):
 		config_file = os.path.join(self.directory, '.hg', 'branch')
-		return get_branch_name(self.directory, config_file, branch_name_from_config_file)
+		return get_branch_name(
+			directory=self.directory,
+			config_file=config_file,
+			get_func=branch_name_from_config_file,
+			create_watcher=self.create_watcher,
+		)
diff --git a/powerline/lint/__init__.py b/powerline/lint/__init__.py
index 9f73b9a8..928f144e 100644
--- a/powerline/lint/__init__.py
+++ b/powerline/lint/__init__.py
@@ -460,13 +460,14 @@ main_spec = (Spec(
 		# only for existence of the path, not for it being a directory
 		paths=Spec().list((lambda value, *args: (True, True, not os.path.exists(os.path.expanduser(value.value)))),
 					lambda value: 'path does not exist: {0}'.format(value)).optional(),
-		log_file=Spec().type(str).func(lambda value, *args: (True, True, not os.path.isdir(os.path.dirname(os.path.expanduser(value)))),
+		log_file=Spec().type(unicode).func(lambda value, *args: (True, True, not os.path.isdir(os.path.dirname(os.path.expanduser(value)))),
 						lambda value: 'directory does not exist: {0}'.format(os.path.dirname(value))).optional(),
 		log_level=Spec().re('^[A-Z]+$').func(lambda value, *args: (True, True, not hasattr(logging, value)),
 										lambda value: 'unknown debugging level {0}'.format(value)).optional(),
-		log_format=Spec().type(str).optional(),
+		log_format=Spec().type(unicode).optional(),
 		interval=Spec().either(Spec().cmp('gt', 0.0), Spec().type(type(None))).optional(),
 		reload_config=Spec().type(bool).optional(),
+		watcher=Spec().type(unicode).oneof(set(('auto', 'inotify', 'stat'))).optional(),
 	).context_message('Error while loading common configuration (key {key})'),
 	ext=Spec(
 		vim=Spec(
diff --git a/powerline/lint/inspect.py b/powerline/lint/inspect.py
index 294f2f59..345f1a5c 100644
--- a/powerline/lint/inspect.py
+++ b/powerline/lint/inspect.py
@@ -25,6 +25,8 @@ def getconfigargspec(obj):
 					if (arg == 'self' or
 							(arg == 'segment_info' and
 								getattr(obj, 'powerline_requires_segment_info', None)) or
+							(arg == 'create_watcher' and
+								getattr(obj, 'powerline_requires_filesystem_watcher', None)) or
 							(arg == 'pl') or
 							(method.startswith('render') and (1 if argspec.args[0] == 'self' else 0) + i == len(argspec.args)) or
 							arg in args):
diff --git a/powerline/segment.py b/powerline/segment.py
index b842c62a..cf495c87 100644
--- a/powerline/segment.py
+++ b/powerline/segment.py
@@ -1,6 +1,8 @@
 # vim:fileencoding=utf-8:noet
 
-from __future__ import absolute_import
+from __future__ import absolute_import, unicode_literals, division, print_function
+
+from powerline.lib.file_watcher import create_file_watcher
 import sys
 
 
@@ -52,15 +54,15 @@ def get_attr_func(contents_func, key, args):
 		return None
 	else:
 		if args is None:
-			return lambda : func()
+			return lambda: func()
 		else:
 			return lambda pl, shutdown_event: func(pl=pl, shutdown_event=shutdown_event, **args)
 
 
-def gen_segment_getter(pl, ext, path, theme_configs, default_module=None):
+def gen_segment_getter(pl, ext, common_config, theme_configs, default_module=None):
 	data = {
 		'default_module': default_module or 'powerline.segments.' + ext,
-		'path': path,
+		'path': common_config['paths'],
 	}
 
 	def get_key(segment, module, key, default=None):
@@ -90,6 +92,10 @@ def gen_segment_getter(pl, ext, path, theme_configs, default_module=None):
 			startup_func = get_attr_func(_contents_func, 'startup', args)
 			shutdown_func = get_attr_func(_contents_func, 'shutdown', None)
 
+			if hasattr(_contents_func, 'powerline_requires_filesystem_watcher'):
+				create_watcher = lambda: create_file_watcher(pl, common_config['watcher'])
+				args['create_watcher'] = create_watcher
+
 			if hasattr(_contents_func, 'powerline_requires_segment_info'):
 				contents_func = lambda pl, segment_info: _contents_func(pl=pl, segment_info=segment_info, **args)
 			else:
diff --git a/powerline/segments/common.py b/powerline/segments/common.py
index 5c22416c..775b38e2 100644
--- a/powerline/segments/common.py
+++ b/powerline/segments/common.py
@@ -18,7 +18,7 @@ from powerline.lib.threaded import ThreadedSegment, KwThreadedSegment, with_docs
 from powerline.lib.monotonic import monotonic
 from powerline.lib.humanize_bytes import humanize_bytes
 from powerline.lib.unicode import u
-from powerline.theme import requires_segment_info
+from powerline.theme import requires_segment_info, requires_filesystem_watcher
 from collections import namedtuple
 
 
@@ -51,8 +51,9 @@ def hostname(pl, segment_info, only_if_ssh=False, exclude_domain=False):
 	return socket.gethostname()
 
 
+@requires_filesystem_watcher
 @requires_segment_info
-def branch(pl, segment_info, status_colors=False):
+def branch(pl, segment_info, create_watcher, status_colors=False):
 	'''Return the current VCS branch.
 
 	:param bool status_colors:
@@ -61,7 +62,7 @@ def branch(pl, segment_info, status_colors=False):
 	Highlight groups used: ``branch_clean``, ``branch_dirty``, ``branch``.
 	'''
 	name = segment_info['getcwd']()
-	repo = guess(path=name)
+	repo = guess(path=name, create_watcher=create_watcher)
 	if repo is not None:
 		branch = repo.branch()
 		scol = ['branch']
diff --git a/powerline/segments/vim.py b/powerline/segments/vim.py
index 9161c729..f1647dee 100644
--- a/powerline/segments/vim.py
+++ b/powerline/segments/vim.py
@@ -10,7 +10,7 @@ except ImportError:
 
 from powerline.bindings.vim import (vim_get_func, getbufvar, vim_getbufoption,
 									buffer_name, vim_getwinvar)
-from powerline.theme import requires_segment_info
+from powerline.theme import requires_segment_info, requires_filesystem_watcher
 from powerline.lib import add_divider_highlight_group
 from powerline.lib.vcs import guess, tree_status
 from powerline.lib.humanize_bytes import humanize_bytes
@@ -368,8 +368,9 @@ def modified_buffers(pl, text='+ ', join_str=','):
 	return None
 
 
+@requires_filesystem_watcher
 @requires_segment_info
-def branch(pl, segment_info, status_colors=False):
+def branch(pl, segment_info, create_watcher, status_colors=False):
 	'''Return the current working branch.
 
 	:param bool status_colors:
@@ -382,7 +383,7 @@ def branch(pl, segment_info, status_colors=False):
 	name = segment_info['buffer'].name
 	skip = not (name and (not vim_getbufoption(segment_info, 'buftype')))
 	if not skip:
-		repo = guess(path=name)
+		repo = guess(path=name, create_watcher=create_watcher)
 		if repo is not None:
 			branch = repo.branch()
 			scol = ['branch']
@@ -396,8 +397,9 @@ def branch(pl, segment_info, status_colors=False):
 			}]
 
 
+@requires_filesystem_watcher
 @requires_segment_info
-def file_vcs_status(pl, segment_info):
+def file_vcs_status(pl, segment_info, create_watcher):
 	'''Return the VCS status for this buffer.
 
 	Highlight groups used: ``file_vcs_status``.
@@ -405,7 +407,7 @@ def file_vcs_status(pl, segment_info):
 	name = segment_info['buffer'].name
 	skip = not (name and (not vim_getbufoption(segment_info, 'buftype')))
 	if not skip:
-		repo = guess(path=name)
+		repo = guess(path=name, create_watcher=create_watcher)
 		if repo is not None:
 			status = repo.status(os.path.relpath(name, repo.directory))
 			if not status:
diff --git a/powerline/theme.py b/powerline/theme.py
index c6157e8f..6450fab3 100644
--- a/powerline/theme.py
+++ b/powerline/theme.py
@@ -10,6 +10,11 @@ def requires_segment_info(func):
 	return func
 
 
+def requires_filesystem_watcher(func):
+	func.powerline_requires_filesystem_watcher = True
+	return func
+
+
 def new_empty_segment_line():
 	return {
 		'left': [],
@@ -37,7 +42,7 @@ class Theme(object):
 		theme_configs = [theme_config]
 		if top_theme_config:
 			theme_configs.append(top_theme_config)
-		get_segment = gen_segment_getter(pl, ext, common_config['paths'], theme_configs, theme_config.get('default_module'))
+		get_segment = gen_segment_getter(pl, ext, common_config, theme_configs, theme_config.get('default_module'))
 		for segdict in itertools.chain((theme_config['segments'],),
 										theme_config['segments'].get('above', ())):
 			self.segments.append(new_empty_segment_line())
diff --git a/tests/lib/config_mock.py b/tests/lib/config_mock.py
index 2ad78853..f4f50624 100644
--- a/tests/lib/config_mock.py
+++ b/tests/lib/config_mock.py
@@ -138,7 +138,12 @@ def get_powerline_raw(PowerlineClass, **kwargs):
 	else:
 		renderer = SimpleRenderer
 	pl = PowerlineClass(
-		config_loader=ConfigLoader(load=load_json_config, watcher=watcher, run_once=kwargs.get('run_once')),
+		config_loader=ConfigLoader(
+			load=load_json_config,
+			watcher=watcher,
+			watcher_type='test',
+			run_once=kwargs.get('run_once')
+		),
 		**kwargs
 	)
 	pl._watcher = watcher
diff --git a/tests/test_config_reload.py b/tests/test_config_reload.py
index f3ce58aa..4d33128e 100644
--- a/tests/test_config_reload.py
+++ b/tests/test_config_reload.py
@@ -23,6 +23,7 @@ config = {
 			},
 			'spaces': 0,
 			'interval': 0,
+			'watcher': 'test',
 		},
 		'ext': {
 			'test': {
diff --git a/tests/test_configuration.py b/tests/test_configuration.py
index d6e64f40..343f90ba 100644
--- a/tests/test_configuration.py
+++ b/tests/test_configuration.py
@@ -4,7 +4,7 @@ import tests.vim as vim_module
 import powerline as powerline_module
 from tests import TestCase
 from tests.lib import replace_item
-from tests.lib.config_mock import swap_attributes, get_powerline, pop_events
+from tests.lib.config_mock import swap_attributes, get_powerline
 from tests.lib.config_mock import get_powerline_raw
 from functools import wraps
 from copy import deepcopy
@@ -27,6 +27,7 @@ config = {
 			},
 			'spaces': 0,
 			'interval': 0,
+			'watcher': 'test',
 		},
 		'ext': {
 			'test': {
diff --git a/tests/test_lib.py b/tests/test_lib.py
index 6c306615..0bbae4e4 100644
--- a/tests/test_lib.py
+++ b/tests/test_lib.py
@@ -3,9 +3,11 @@ from __future__ import division
 
 from powerline.lib import mergedicts, add_divider_highlight_group, REMOVE_THIS_KEY
 from powerline.lib.humanize_bytes import humanize_bytes
-from powerline.lib.vcs import guess
+from powerline.lib.vcs import guess, get_fallback_create_watcher
 from powerline.lib.threaded import ThreadedSegment, KwThreadedSegment
 from powerline.lib.monotonic import monotonic
+from powerline.lib.file_watcher import create_file_watcher, INotifyError
+from powerline import get_fallback_logger
 import threading
 import os
 import sys
@@ -384,9 +386,9 @@ class TestFilesystemWatchers(TestCase):
 		self.fail('The change to {0} was not detected'.format(path))
 
 	def test_file_watcher(self):
-		from powerline.lib.file_watcher import create_file_watcher
-		w = create_file_watcher(use_stat=False)
-		if w.is_stat_based:
+		try:
+			w = create_file_watcher(pl=get_fallback_logger(), watcher_type='inotify')
+		except INotifyError:
 			raise SkipTest('This test is not suitable for a stat based file watcher')
 		f1, f2, f3 = map(lambda x: os.path.join(INOTIFY_DIR, 'file%d' % x), (1, 2, 3))
 		with open(f1, 'wb'):
@@ -485,7 +487,8 @@ class TestVCS(TestCase):
 			self.assertEqual(ans, q)
 
 	def test_git(self):
-		repo = guess(path=GIT_REPO)
+		create_watcher = get_fallback_create_watcher()
+		repo = guess(path=GIT_REPO, create_watcher=create_watcher)
 		self.assertNotEqual(repo, None)
 		self.assertEqual(repo.branch(), 'master')
 		self.assertEqual(repo.status(), None)
@@ -520,7 +523,8 @@ class TestVCS(TestCase):
 
 	if use_mercurial:
 		def test_mercurial(self):
-			repo = guess(path=HG_REPO)
+			create_watcher = get_fallback_create_watcher()
+			repo = guess(path=HG_REPO, create_watcher=create_watcher)
 			self.assertNotEqual(repo, None)
 			self.assertEqual(repo.branch(), 'default')
 			self.assertEqual(repo.status(), None)
@@ -536,7 +540,8 @@ class TestVCS(TestCase):
 
 	if use_bzr:
 		def test_bzr(self):
-			repo = guess(path=BZR_REPO)
+			create_watcher = get_fallback_create_watcher()
+			repo = guess(path=BZR_REPO, create_watcher=create_watcher)
 			self.assertNotEqual(repo, None, 'No bzr repo found. Do you have bzr installed?')
 			self.assertEqual(repo.branch(), 'test_powerline')
 			self.assertEqual(repo.status(), None)
@@ -587,7 +592,7 @@ class TestVCS(TestCase):
 				os.mkdir(d)
 				call(['bzr', 'init', '-q'], cwd=d)
 				call(['bzr', 'nick', '-q', x], cwd=d)
-				repo = guess(path=d)
+				repo = guess(path=d, create_watcher=create_watcher)
 				self.assertEqual(repo.branch(), x)
 				self.assertFalse(repo.status())
 				if x == 'b1':
@@ -598,7 +603,7 @@ class TestVCS(TestCase):
 			os.rename(os.path.join(BZR_REPO, 'b'), os.path.join(BZR_REPO, 'b2'))
 			for x, y in (('b1', 'b2'), ('b2', 'b1')):
 				d = os.path.join(BZR_REPO, x)
-				repo = guess(path=d)
+				repo = guess(path=d, create_watcher=create_watcher)
 				self.do_branch_rename_test(repo, y)
 				if x == 'b1':
 					self.assertFalse(repo.status())
diff --git a/tests/test_segments.py b/tests/test_segments.py
index ddd264f2..497a58ab 100644
--- a/tests/test_segments.py
+++ b/tests/test_segments.py
@@ -3,9 +3,11 @@
 from __future__ import unicode_literals
 
 from powerline.segments import shell, common
+from powerline.lib.vcs import get_fallback_create_watcher
 import tests.vim as vim_module
 import sys
 import os
+from functools import partial
 from tests.lib import Args, urllib_read, replace_attr, new_module, replace_module_module, replace_env, Pl
 from tests import TestCase
 
@@ -13,6 +15,16 @@ from tests import TestCase
 vim = None
 
 
+def get_dummy_guess(**kwargs):
+	if 'directory' in kwargs:
+		def guess(path, create_watcher):
+			return Args(branch=lambda: os.path.basename(path), **kwargs)
+	else:
+		def guess(path, create_watcher):
+			return Args(branch=lambda: os.path.basename(path), directory=path, **kwargs)
+	return guess
+
+
 class TestShell(TestCase):
 	def test_last_status(self):
 		pl = Pl()
@@ -201,23 +213,25 @@ class TestCommon(TestCase):
 
 	def test_branch(self):
 		pl = Pl()
+		create_watcher = get_fallback_create_watcher()
 		segment_info = {'getcwd': os.getcwd}
-		with replace_attr(common, 'guess', lambda path: Args(branch=lambda: os.path.basename(path), status=lambda: None, directory='/tmp/tests')):
+		branch = partial(common.branch, pl=pl, create_watcher=create_watcher)
+		with replace_attr(common, 'guess', get_dummy_guess(status=lambda: None, directory='/tmp/tests')):
 			with replace_attr(common, 'tree_status', lambda repo, pl: None):
-				self.assertEqual(common.branch(pl=pl, segment_info=segment_info, status_colors=False),
+				self.assertEqual(branch(segment_info=segment_info, status_colors=False),
 						[{'highlight_group': ['branch'], 'contents': 'tests'}])
-				self.assertEqual(common.branch(pl=pl, segment_info=segment_info, status_colors=True),
+				self.assertEqual(branch(segment_info=segment_info, status_colors=True),
 						[{'contents': 'tests', 'highlight_group': ['branch_clean', 'branch']}])
-		with replace_attr(common, 'guess', lambda path: Args(branch=lambda: os.path.basename(path), status=lambda: 'D  ', directory='/tmp/tests')):
+		with replace_attr(common, 'guess', get_dummy_guess(status=lambda: 'D  ', directory='/tmp/tests')):
 			with replace_attr(common, 'tree_status', lambda repo, pl: 'D '):
-				self.assertEqual(common.branch(pl=pl, segment_info=segment_info, status_colors=False),
+				self.assertEqual(branch(segment_info=segment_info, status_colors=False),
 						[{'highlight_group': ['branch'], 'contents': 'tests'}])
-				self.assertEqual(common.branch(pl=pl, segment_info=segment_info, status_colors=True),
+				self.assertEqual(branch(segment_info=segment_info, status_colors=True),
 						[{'contents': 'tests', 'highlight_group': ['branch_dirty', 'branch']}])
-				self.assertEqual(common.branch(pl=pl, segment_info=segment_info, status_colors=False),
+				self.assertEqual(branch(segment_info=segment_info, status_colors=False),
 						[{'highlight_group': ['branch'], 'contents': 'tests'}])
-		with replace_attr(common, 'guess', lambda path: None):
-			self.assertEqual(common.branch(pl=pl, segment_info=segment_info, status_colors=False), None)
+		with replace_attr(common, 'guess', lambda path, create_watcher: None):
+			self.assertEqual(branch(segment_info=segment_info, status_colors=False), None)
 
 	def test_cwd(self):
 		new_os = new_module('os', path=os.path, sep='/')
@@ -705,32 +719,36 @@ class TestVim(TestCase):
 
 	def test_branch(self):
 		pl = Pl()
+		create_watcher = get_fallback_create_watcher()
+		branch = partial(vim.branch, pl=pl, create_watcher=create_watcher)
 		with vim_module._with('buffer', '/foo') as segment_info:
-			with replace_attr(vim, 'guess', lambda path: Args(branch=lambda: os.path.basename(path), status=lambda: None, directory=path)):
+			with replace_attr(vim, 'guess', get_dummy_guess(status=lambda: None)):
 				with replace_attr(vim, 'tree_status', lambda repo, pl: None):
-					self.assertEqual(vim.branch(pl=pl, segment_info=segment_info, status_colors=False),
+					self.assertEqual(branch(segment_info=segment_info, status_colors=False),
 							[{'divider_highlight_group': 'branch:divider', 'highlight_group': ['branch'], 'contents': 'foo'}])
-					self.assertEqual(vim.branch(pl=pl, segment_info=segment_info, status_colors=True),
+					self.assertEqual(branch(segment_info=segment_info, status_colors=True),
 							[{'divider_highlight_group': 'branch:divider', 'highlight_group': ['branch_clean', 'branch'], 'contents': 'foo'}])
-			with replace_attr(vim, 'guess', lambda path: Args(branch=lambda: os.path.basename(path), status=lambda: 'DU', directory=path)):
+			with replace_attr(vim, 'guess', get_dummy_guess(status=lambda: 'DU')):
 				with replace_attr(vim, 'tree_status', lambda repo, pl: 'DU'):
-					self.assertEqual(vim.branch(pl=pl, segment_info=segment_info, status_colors=False),
+					self.assertEqual(branch(segment_info=segment_info, status_colors=False),
 							[{'divider_highlight_group': 'branch:divider', 'highlight_group': ['branch'], 'contents': 'foo'}])
-					self.assertEqual(vim.branch(pl=pl, segment_info=segment_info, status_colors=True),
+					self.assertEqual(branch(segment_info=segment_info, status_colors=True),
 							[{'divider_highlight_group': 'branch:divider', 'highlight_group': ['branch_dirty', 'branch'], 'contents': 'foo'}])
 
 	def test_file_vcs_status(self):
 		pl = Pl()
+		create_watcher = get_fallback_create_watcher()
+		file_vcs_status = partial(vim.file_vcs_status, pl=pl, create_watcher=create_watcher)
 		with vim_module._with('buffer', '/foo') as segment_info:
-			with replace_attr(vim, 'guess', lambda path: Args(branch=lambda: os.path.basename(path), status=lambda file: 'M', directory=path)):
-				self.assertEqual(vim.file_vcs_status(pl=pl, segment_info=segment_info),
+			with replace_attr(vim, 'guess', get_dummy_guess(status=lambda file: 'M')):
+				self.assertEqual(file_vcs_status(segment_info=segment_info),
 						[{'highlight_group': ['file_vcs_status_M', 'file_vcs_status'], 'contents': 'M'}])
-			with replace_attr(vim, 'guess', lambda path: Args(branch=lambda: os.path.basename(path), status=lambda file: None, directory=path)):
-				self.assertEqual(vim.file_vcs_status(pl=pl, segment_info=segment_info), None)
+			with replace_attr(vim, 'guess', get_dummy_guess(status=lambda file: None)):
+				self.assertEqual(file_vcs_status(segment_info=segment_info), None)
 		with vim_module._with('buffer', '/bar') as segment_info:
 			with vim_module._with('bufoptions', buftype='nofile'):
-				with replace_attr(vim, 'guess', lambda path: Args(branch=lambda: os.path.basename(path), status=lambda file: 'M', directory=path)):
-					self.assertEqual(vim.file_vcs_status(pl=pl, segment_info=segment_info), None)
+				with replace_attr(vim, 'guess', get_dummy_guess(status=lambda file: 'M')):
+					self.assertEqual(file_vcs_status(segment_info=segment_info), None)
 
 old_cwd = None