[module/pulseaudio] somewhat experimental immediate update

try to immediately update pulseaudio, if pactl subscribe exists & allows
us to monitor update.

see #913

bumblebee_status/modules/core/pulseaudio.py

@@ -33,12 +33,17 @@ Requires the following executable:
 """
 
 import re
+import os
 import logging
 import functools
+import threading
+import subprocess
+import select
 
 import core.module
 import core.widget
 import core.input
+import core.event
 
 import util.cli
 import util.graph
@@ -103,6 +108,42 @@ class Module(core.module.Module):
         for event in events:
             core.input.register(self, button=event["button"], cmd=event["action"])
 
+        self.__monitor = threading.Thread(target=self.__subscribe, args=())
+        self.__monitor.start()
+
+    def __subscribe(self):
+        self.update2()
+        core.event.trigger("update", [self.id], redraw_only=True)
+        core.event.trigger("draw")
+        try:
+            proc = subprocess.Popen("pactl subscribe",
+                stdout = subprocess.PIPE,
+                stderr = subprocess.PIPE,
+                shell = True
+            )
+        except:
+            return
+        os.set_blocking(proc.stdout.fileno(), False)
+        while threading.main_thread().is_alive():
+            r, w, e = select.select([proc.stdout], [], [], 1)
+
+            if not (r or w or e):
+                continue # timeout
+
+            line = 'test'
+            update = False
+            while line:
+                line = proc.stdout.readline().decode("ascii", errors="ignore")
+                if "client" in line:
+                    update = True
+
+            if update:
+                self.update2()
+                core.event.trigger("update", [self.id], redraw_only=True)
+                core.event.trigger("draw")
+                while proc.stdout.readline().decode("ascii", errors="ignore"):
+                    pass
+
     def set_volume(self, amount):
         util.cli.execute(
             "pactl set-{}-{} @DEFAULT_{}@ {}".format(
@@ -200,6 +241,11 @@ class Module(core.module.Module):
         return output
 
     def update(self):
+        if self.__monitor.is_alive():
+            return
+        self.update2()
+
+    def update2(self):
         try:
             self._failed = False
             channel = "sinks" if self._channel == "sink" else "sources"