nowplaying: Create a Seeker

This is a Gtk.Scale configured to be used to display track progress and
seek inside the track.

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

emmental/nowplaying/seeker.py

@@ -0,0 +1,50 @@
+# Copyright 2022 (c) Anna Schumaker.
+"""A Gtk.Scale configured for position tracking seeking."""
+from gi.repository import GObject
+from gi.repository import Gtk
+from gi.repository import Gst
+
+
+class Scale(Gtk.Scale):
+    """A Gtk.Scale configured for our application."""
+
+    def __init__(self, **kwargs):
+        """Initialize our Scale."""
+        super().__init__(margin_start=45, margin_end=45, draw_value=True,
+                         hexpand=True, **kwargs)
+        self._adjustment = Gtk.Adjustment.new(value=0, lower=0, upper=1,
+                                              step_increment=5*Gst.SECOND,
+                                              page_increment=30*Gst.SECOND,
+                                              page_size=0)
+        self.set_adjustment(self._adjustment)
+        self.set_format_value_func(self.format_value)
+
+    def format_value(self, scale: Gtk.Scale, value: float) -> str:
+        """Format the position and duration values."""
+        duration = round(self.duration * Gst.USECOND / Gst.SECOND)
+        position = round(value * Gst.USECOND / Gst.SECOND)
+        remaining = duration - position
+        (p_m, p_s) = divmod(position, 60)
+        (r_m, r_s) = divmod(remaining, 60)
+        return f"{p_m:02}:{p_s:02} / {r_m:02}:{r_s:02}"
+
+    @GObject.Property(type=float)
+    def duration(self) -> float:
+        """Get the duration of the current track."""
+        return self._adjustment.get_upper()
+
+    @duration.setter
+    def duration(self, newval: float) -> None:
+        """Set the duration of the current track."""
+        self.set_range(0, max(newval, 1))
+        self.emit("value-changed")
+
+    @GObject.Property(type=float)
+    def position(self) -> float:
+        """Get the position of the current track."""
+        return self.get_value()
+
+    @position.setter
+    def position(self, newval: float) -> None:
+        """Set the position of the current track."""
+        self.set_value(newval)

tests/nowplaying/test_seeker.py

@@ -0,0 +1,76 @@
+# Copyright 2022 (c) Anna Schumaker.
+"""Test our modified Gtk.Scale."""
+import unittest
+import emmental.nowplaying.seeker
+from gi.repository import Gtk
+from gi.repository import Gst
+
+
+class TestScale(unittest.TestCase):
+    """Tests our custom Gtk.Scale."""
+
+    def setUp(self):
+        """Set up common variables."""
+        self.scale = emmental.nowplaying.seeker.Scale()
+
+    def test_init(self):
+        """Test that the scale is configured correctly."""
+        self.assertIsInstance(self.scale, Gtk.Scale)
+        self.assertEqual(self.scale.get_margin_start(), 45)
+        self.assertEqual(self.scale.get_margin_end(), 45)
+        self.assertEqual(self.scale.get_orientation(),
+                         Gtk.Orientation.HORIZONTAL)
+        self.assertTrue(self.scale.get_draw_value())
+        self.assertTrue(self.scale.get_hexpand())
+
+    def test_adjustment(self):
+        """Test the underlying Gtk.Adjustment."""
+        self.assertIsInstance(self.scale._adjustment, Gtk.Adjustment)
+        self.assertEqual(self.scale.get_adjustment(), self.scale._adjustment)
+
+        self.assertEqual(self.scale._adjustment.get_value(), 0)
+        self.assertEqual(self.scale._adjustment.get_lower(), 0)
+        self.assertEqual(self.scale._adjustment.get_upper(), 1)
+        self.assertEqual(self.scale._adjustment.get_step_increment(),
+                         5 * Gst.SECOND)
+        self.assertEqual(self.scale._adjustment.get_page_increment(),
+                         30 * Gst.SECOND)
+        self.assertEqual(self.scale._adjustment.get_page_size(), 0)
+
+    def test_duration(self):
+        """Test the duration property."""
+        self.assertEqual(self.scale.duration, 1)
+
+        changed = unittest.mock.Mock()
+        self.scale.connect("value-changed", changed)
+
+        for (duration, expected) in [(5, 5), (10, 10), (0, 1)]:
+            with self.subTest(duration=duration, expected=expected):
+                changed.reset_mock()
+                self.scale.duration = duration
+                self.assertEqual(self.scale._adjustment.get_upper(), expected)
+                self.assertEqual(self.scale.duration, expected)
+                changed.assert_called_with(self.scale)
+
+    def test_position(self):
+        """Test the position property."""
+        self.assertEqual(self.scale.position, 0)
+        self.scale.duration = 10
+
+        for pos in range(12):
+            with self.subTest(pos=pos):
+                self.scale.position = pos
+                self.assertEqual(self.scale.get_value(), min(10, pos))
+                self.assertEqual(self.scale.position, min(10, pos))
+
+    def test_format_value(self):
+        """Test that the value is formatted correctly."""
+        for (pos, dur, text) in [(0, 0, "00:00 / 00:00"),
+                                 (10, 75, "00:10 / 01:05"),
+                                 (75, 720, "01:15 / 10:45"),
+                                 (660, 720, "11:00 / 01:00")]:
+            with self.subTest(pos=pos, dur=dur, text=text):
+                self.scale.duration = dur * Gst.SECOND / Gst.USECOND
+                position = pos * Gst.SECOND / Gst.USECOND
+                output = self.scale.format_value(self.scale, position)
+                self.assertEqual(output, text)