Start using signals to call for saving playlist

app/musicmuster.py

@@ -249,6 +249,17 @@ class ImportTrack(QObject):
             self.finished.emit(self.playlist)
 
 
+class MusicMusterSignals(QObject):
+    """
+    Class for all MusicMuster signals. See:
+     - https://zetcode.com/gui/pyqt5/eventssignals/
+     - https://stackoverflow.com/questions/62654525/
+        emit-a-signal-from-another-class-to-main-class
+    """
+
+    save_playlist_signal = pyqtSignal()
+
+
 class Window(QMainWindow, Ui_MainWindow):
     def __init__(self, parent=None, *args, **kwargs) -> None:
         super().__init__(*args, **kwargs)
@@ -267,6 +278,8 @@ class Window(QMainWindow, Ui_MainWindow):
         self.previous_track_position: Optional[float] = None
         self.selected_plrs: Optional[List[PlaylistRows]] = None
 
+        self.signals = MusicMusterSignals()
+
         # Set colours that will be used by playlist row stripes
         palette = QPalette()
         palette.setColor(QPalette.Base, QColor(Config.COLOUR_EVEN_PLAYLIST))
@@ -614,7 +627,8 @@ class Window(QMainWindow, Ui_MainWindow):
         assert playlist.id
 
         playlist_tab = PlaylistTab(
-            musicmuster=self, session=session, playlist_id=playlist.id)
+            musicmuster=self, session=session, playlist_id=playlist.id,
+            signals=self.signals)
         idx = self.tabPlaylist.addTab(playlist_tab, playlist.name)
         self.tabPlaylist.setCurrentIndex(idx)
 

app/playlists.py

@@ -8,7 +8,6 @@ from datetime import datetime, timedelta
 from typing import cast, List, Optional, TYPE_CHECKING, Union
 
 from PyQt5.QtCore import (
-    pyqtSignal,
     QEvent,
     QModelIndex,
     QObject,
@@ -60,7 +59,7 @@ from models import (
 )
 
 if TYPE_CHECKING:
-    from musicmuster import Window
+    from musicmuster import Window, MusicMusterSignals
 
 start_time_re = re.compile(r"@\d\d:\d\d:\d\d")
 HEADER_NOTES_COLUMN = 2
@@ -138,10 +137,11 @@ class PlaylistTab(QTableWidget):
 
     def __init__(self, musicmuster: "Window",
                  session: scoped_session,
-                 playlist_id: int, *args, **kwargs) -> None:
-        super().__init__(*args, **kwargs)
+                 playlist_id: int, signals: "MusicMusterSignals") -> None:
+        super().__init__()
         self.musicmuster: Window = musicmuster
         self.playlist_id = playlist_id
+        self.signals = signals
 
         # Set up widget
         self.menu: Optional[QMenu] = None
@@ -193,6 +193,7 @@ class PlaylistTab(QTableWidget):
         self.selecting_in_progress = False
         # Connect signals
         self.horizontalHeader().sectionResized.connect(self._column_resize)
+        self.signals.save_playlist_signal.connect(self._deferred_save)
 
         # Load playlist rows
         self.populate_display(session, self.playlist_id)
@@ -1292,6 +1293,15 @@ class PlaylistTab(QTableWidget):
                 cb.clear(mode=cb.Clipboard)
                 cb.setText(pathqs, mode=cb.Clipboard)
 
+    def _deferred_save(self) -> None:
+        """
+        Create session and save playlist
+        """
+
+        print("_deferred_save() called")
+        with Session() as session:
+            self.save_playlist(session)
+
     def _delete_rows(self) -> None:
         """
         Delete mutliple rows
@@ -1301,22 +1311,33 @@ class PlaylistTab(QTableWidget):
         - Save the playlist
         """
 
-        # Delete rows from database
-        plr_ids = self.get_selected_playlistrow_ids()
-        if not plr_ids:
-            return
-
-        # Get confirmation
-        row_count = len(plr_ids)
-        plural = 's' if row_count > 1 else ''
-        if not ask_yes_no("Delete rows",
-                          f"Really delete {row_count} row{plural}?"):
-            return
-
-        self.remove_selected_rows()
-
         with Session() as session:
-            QTimer.singleShot(0, lambda: self.save_playlist(session))
+            plrs = self.get_selected_playlistrows(session)
+            row_count = len(plrs)
+            if not row_count:
+                return
+
+            # Get confirmation
+            plural = 's' if row_count > 1 else ''
+            if not ask_yes_no("Delete rows",
+                              f"Really delete {row_count} row{plural}?"):
+                return
+
+            rows_to_delete = [a.row_number for a in plrs]
+
+            # Delete rows from database. Would be more efficient to
+            # query then have a single delete.
+            for plr in plrs:
+                session.delete(plr)
+
+            # Remove from display
+            self.remove_rows(rows_to_delete)
+
+            # Reset drag mode
+            self.setDragEnabled(False)
+
+            # QTimer.singleShot(0, lambda: self._deferred_save())
+            self.signals.save_playlist_signal.emit()
 
     def _drop_on(self, event):
         """