header: Create a BackgroundRow ListBox row

This widget will be added to the Volume popover and allow configuring a
lower volume for background listening while focusing on tasks.

Implements: #50 ("Background Music Mode")
Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

emmental/header/volume.py

@@ -2,6 +2,7 @@
 """A custom Gtk.Box with controls for adjusting the volume."""
 from gi.repository import GObject
 from gi.repository import Gtk
+from gi.repository import Adw
 
 STEP_SIZE = 0.05
 
@@ -55,3 +56,27 @@ class VolumeRow(Gtk.ListBoxRow):
 
     def __value_changed(self, range: Gtk.Range) -> None:
         self.volume = range.get_value()
+
+
+class BackgroundRow(Adw.ExpanderRow):
+    """A VolumeRow for setting Background Listening volume."""
+
+    enabled = GObject.Property(type=bool, default=False)
+    volume = GObject.Property(type=float, default=0.5)
+
+    def __init__(self):
+        """Initialize the BackgroundRow."""
+        super().__init__(title="Background Listening",
+                         subtitle="Decrease the volume to help focus")
+        self._switch = Gtk.Switch(valign=Gtk.Align.CENTER)
+        self._volume = VolumeRow(volume=self.volume)
+
+        self.add_prefix(self._switch)
+        self.add_row(self._volume)
+
+        self._switch.bind_property("active", self, "expanded",
+                                   GObject.BindingFlags.BIDIRECTIONAL)
+        self.bind_property("enabled", self._switch, "active",
+                           GObject.BindingFlags.BIDIRECTIONAL)
+        self.bind_property("volume", self._volume, "volume",
+                           GObject.BindingFlags.BIDIRECTIONAL)

tests/header/test_volume.py

@@ -4,6 +4,7 @@ import unittest
 import emmental.header.volume
 import tests.util
 from gi.repository import Gtk
+from gi.repository import Adw
 
 
 class TestVolumeRow(unittest.TestCase):
@@ -109,3 +110,58 @@ class TestVolumeRow(unittest.TestCase):
             with self.subTest(value=value):
                 self.assertEqual(format_value(self.vol._scale, value/100),
                                  f"{value} %")
+
+
+class TestBackgroundRow(unittest.TestCase):
+    """Test case for our Background Listening volume row."""
+
+    def setUp(self):
+        """Set up common variables."""
+        self.background = emmental.header.volume.BackgroundRow()
+
+    def test_init(self):
+        """Test that the Background Listening row was set up properly."""
+        self.assertIsInstance(self.background, Adw.ExpanderRow)
+        self.assertEqual(self.background.get_title(), "Background Listening")
+        self.assertEqual(self.background.get_subtitle(),
+                         "Decrease the volume to help focus")
+
+        self.background.set_expanded(True)
+        self.assertTrue(self.background._switch.get_active())
+        self.background.set_expanded(False)
+        self.assertFalse(self.background._switch.get_active())
+
+    def test_switch(self):
+        """Check that the BackgroundRow switch works as intended."""
+        self.assertIsInstance(self.background._switch, Gtk.Switch)
+        self.assertEqual(self.background._switch.get_valign(),
+                         Gtk.Align.CENTER)
+        self.assertFalse(self.background._switch.get_active())
+
+        self.background._switch.set_active(True)
+        self.assertTrue(self.background.get_expanded())
+        self.background._switch.set_active(False)
+        self.assertFalse(self.background.get_expanded())
+
+    def test_volume(self):
+        """Check the VolumeRow instance inside the Expander."""
+        self.assertIsInstance(self.background._volume,
+                              emmental.header.volume.VolumeRow)
+        self.assertEqual(self.background.volume, 0.5)
+        self.assertEqual(self.background._volume.volume, 0.5)
+
+        self.background.volume = 0.75
+        self.assertEqual(self.background._volume.volume, 0.75)
+
+        self.background._volume.volume = 0.25
+        self.assertEqual(self.background.volume, 0.25)
+
+    def test_enabled(self):
+        """Check the BackgroundRow enabled property."""
+        self.assertFalse(self.background.enabled)
+
+        self.background.enabled = True
+        self.assertTrue(self.background._switch.get_active())
+
+        self.background._switch.set_active(False)
+        self.assertFalse(self.background.enabled)