Replace awesome-client with a Python-native dbus interface.

Instead of spawning awesome-client every couple of seconds to update the
widget, use Python's own native dbus interface. Fewer system resources used by
avoiding the spawn as well as removing noise on the dbus caused by open+close.

Signed-off-by: Bryce Chidester <bryce@cobryce.com>

powerline/bindings/wm/awesome.py

@@ -1,27 +1,14 @@
 # vim:fileencoding=utf-8:noet
 from __future__ import (unicode_literals, division, absolute_import, print_function)
 
-import sys
-
 from threading import Thread, Event
 from time import sleep
-from subprocess import Popen, PIPE
+import dbus
 
 from powerline import Powerline
 from powerline.lib.monotonic import monotonic
 
 
-def read_to_log(pl, client):
-	for line in client.stdout:
-		if line:
-			pl.info(line, prefix='awesome-client')
-	for line in client.stderr:
-		if line:
-			pl.error(line, prefix='awesome-client')
-	if client.wait():
-		pl.error('Client exited with {0}', client.returncode, prefix='awesome')
-
-
 def run(thread_shutdown_event=None, pl_shutdown_event=None, pl_config_loader=None,
         interval=None):
 	powerline = Powerline(
@@ -32,6 +19,18 @@ def run(thread_shutdown_event=None, pl_shutdown_event=None, pl_config_loader=Non
 	)
 	powerline.update_renderer()
 
+	try:
+		session_bus = dbus.SessionBus()
+	except Exception as e:
+		powerline.pl.exception('Failed to connect to session bus: {0}', str(e))
+		raise
+	try:
+		awesome_client = session_bus.get_object('org.naquadah.awesome.awful', '/')
+	except dbus.exceptions.DBusException as e:
+		powerline.pl.exception('Failed to locate Awesome service on dbus: {0}', str(e))
+		raise
+	awesome_eval = awesome_client.get_dbus_method('Eval', dbus_interface='org.naquadah.awesome.awful.Remote')
+
 	if not thread_shutdown_event:
 		thread_shutdown_event = powerline.shutdown_event
 
@@ -41,10 +40,10 @@ def run(thread_shutdown_event=None, pl_shutdown_event=None, pl_config_loader=Non
 		start_time = monotonic()
 		s = powerline.render(side='right')
 		request = 'powerline_widget:set_markup(\'' + s.translate({'\'': '\\\'', '\\': '\\\\'}) + '\')\n'
-		client = Popen(['awesome-client'], shell=False, stdout=PIPE, stderr=PIPE, stdin=PIPE)
-		client.stdin.write(request.encode('utf-8'))
-		client.stdin.close()
-		read_to_log(powerline.pl, client)
+		try:
+			awesome_eval(request.encode('utf-8'))
+		except dbus.exceptions.DBusException as e:
+			powerline.pl.exception('Failure while signaling Awesome on dbus: {0}', str(e))
 		thread_shutdown_event.wait(max(used_interval - (monotonic() - start_time), 0.1))