Use QThreadPool to manage fades

app/music.py

@@ -10,9 +10,53 @@ from time import sleep
 
 from log import log
 
+from PyQt5.QtCore import (
+    QRunnable,
+    QThreadPool,
+)
+
 lock = threading.Lock()
 
 
+class FadeTrack(QRunnable):
+
+    def __init__(self, player: vlc.MediaPlayer) -> None:
+        super().__init__()
+        self.player = player
+
+    def run(self):
+        """
+        Implementation of fading the player
+        """
+
+        if not self.player:
+            return
+
+        fade_time = Config.FADE_TIME / 1000
+        steps = Config.FADE_STEPS
+        sleep_time = fade_time / steps
+        original_volume = self.player.audio_get_volume()
+
+        # We reduce volume by one mesure first, then by two measures,
+        # then three, and so on.
+        # The sum of the arithmetic sequence 1, 2, 3, ..n is
+        # (n**2 + n) / 2
+        total_measures_count = (steps**2 + steps) / 2
+
+        measures_to_reduce_by = 0
+
+        for i in range(1, steps + 1):
+            measures_to_reduce_by += i
+            volume_factor = 1 - (
+                measures_to_reduce_by / total_measures_count)
+            self.player.audio_set_volume(int(original_volume * volume_factor))
+            sleep(sleep_time)
+
+        self.player.stop()
+        log.debug(f"Releasing player {self.player=}")
+        self.player.release()
+
+
 class Music:
     """
     Manage the playing of music tracks
@@ -37,46 +81,15 @@ class Music:
         if not self.player.get_position() > 0 and self.player.is_playing():
             return
 
-        thread = threading.Thread(target=self._fade)
-        thread.start()
-
-    def _fade(self) -> None:
-        """
-        Implementation of fading the current track in a separate thread.
-        """
-
         # Take a copy of current player to allow another track to be
         # started without interfering here
         with lock:
             p = self.player
             self.player = None
 
-        # Sanity check
-        if not p:
-            return
-
-        fade_time = Config.FADE_TIME / 1000
-        steps = Config.FADE_STEPS
-        sleep_time = fade_time / steps
-
-        # We reduce volume by one mesure first, then by two measures,
-        # then three, and so on.
-        # The sum of the arithmetic sequence 1, 2, 3, ..n is
-        # (n**2 + n) / 2
-        total_measures_count = (steps**2 + steps) / 2
-
-        measures_to_reduce_by = 0
-        for i in range(1, steps + 1):
-            measures_to_reduce_by += i
-            volume_factor = 1 - (
-                measures_to_reduce_by / total_measures_count)
-            p.audio_set_volume(int(self.max_volume * volume_factor))
-            sleep(sleep_time)
-
-        with lock:
-            p.stop()
-            log.debug(f"Releasing player {p=}")
-            p.release()
+        pool = QThreadPool.globalInstance()
+        fader = FadeTrack(p)
+        pool.start(fader)
 
     def get_playtime(self) -> Optional[int]:
         """Return elapsed play time"""
@@ -117,13 +130,6 @@ class Music:
 
         return status
 
-#
-#     def set_position(self, ms):
-#         """Set current play time in milliseconds from start"""
-#
-#         with lock:
-#             return self.player.set_time(ms)
-
     def set_volume(self, volume, set_default=True):
         """Set maximum volume used for player"""
 
@@ -138,13 +144,15 @@ class Music:
     def stop(self) -> float:
         """Immediately stop playing"""
 
-        with lock:
-            if not self.player:
-                return 0.0
+        if not self.player:
+            return 0.0
 
-            position = self.player.get_position()
-            self.player.stop()
-            self.player.release()
-            # Ensure we don't reference player after release
-            self.player = None
+        p = self.player
+        self.player = None
+
+        with lock:
+            position = p.get_position()
+            p.stop()
+            p.release()
+            p = None
             return position