Added reading of volume from Denon devices that support it, and reopen socket if needed

mopidy/mixers/denon.py

@@ -6,14 +6,19 @@ from mopidy.settings import MIXER_PORT
 
 class DenonMixer(BaseMixer):
     def __init__(self):
-        self._device = Serial(port=MIXER_PORT)
+        self._device = Serial(port=MIXER_PORT, timeout=0.2)
         self._levels = ['99']+["%(#)02d"% {'#': v} for v in range(0,99)]
         self._volume = None
 
     def _get_volume(self):
-        # The Denon spec doesnt seem to document
-        # how to query the volume, so we keep the
-        # state internally
+        try:
+            self._device.write('MV?\r')
+            vol = self._device.read(2)
+            if vol:
+                return self._levels.index(int(vol))
+        except:
+            pass # No support for volume query on device
+
         return self._volume
 
     def _set_volume(self, volume):
@@ -23,5 +28,7 @@ class DenonMixer(BaseMixer):
         elif volume > 99:
             volume = 99
 
-        self._volume = volume
+        if not self._device.isOpen():
+            self._device.open()
         self._device.write('MV%s\r'% self._levels[volume])
+        self._volume = volume

tests/mixers/denontest.py

@@ -3,13 +3,24 @@ import os
 
 from mopidy.mixers.denon import DenonMixer
 
+class DenonMixerDeviceMock(object):
+    def __init__(self):
+        self._open = True
+        self.ret_val = bytes('00')
+
+    def write(self, x):
+        pass
+    def read(self, x):
+        return self.ret_val
+    def isOpen(self):
+        return self._open
+    def open(self):
+        self._open = True
+
 class DenonMixerTest(unittest.TestCase):
     def setUp(self):
         self.m = DenonMixer()
-        self.m._device = os.tmpfile() # "Mock" :-)
-
-    def tearDown(self):
-        self.m._device.close()
+        self.m._device = DenonMixerDeviceMock()
 
     def test_volume_is_None_initially(self):
         self.assertEqual(self.m.volume, None)
@@ -29,3 +40,8 @@ class DenonMixerTest(unittest.TestCase):
     def test_volume_set_to_above_max_results_in_max(self):
         self.m.volume = 110
         self.assertEqual(self.m.volume, 99)
+
+    def test_reopen_device(self):
+        self.m._device._open = False
+        self.m.volume = 10
+        self.assertTrue(self.m._device._open)