Dont store a reference to the DB in the scheduler

src/calibre/gui2/actions/fetch_news.py

@@ -28,17 +28,14 @@ class FetchNewsAction(InterfaceAction):
     def genesis(self):
         self.conversion_jobs = {}
 
-    def init_scheduler(self, db):
+    def init_scheduler(self):
         from calibre.gui2.dialogs.scheduler import Scheduler
-        self.scheduler = Scheduler(self.gui, db)
+        self.scheduler = Scheduler(self.gui)
         self.scheduler.start_recipe_fetch.connect(self.download_scheduled_recipe, type=Qt.ConnectionType.QueuedConnection)
         self.qaction.setMenu(self.scheduler.news_menu)
         self.qaction.triggered.connect(
                 self.scheduler.show_dialog)
 
-    def library_changed(self, db):
-        self.scheduler.database_changed(db)
-
     def initialization_complete(self):
         self.connect_scheduler()
 

src/calibre/gui2/dialogs/scheduler.py

@@ -572,7 +572,7 @@ class Scheduler(QObject):
     delete_old_news = pyqtSignal(object)
     start_recipe_fetch = pyqtSignal(object)
 
-    def __init__(self, parent, db):
+    def __init__(self, parent):
         QObject.__init__(self, parent)
         self.internet_connection_failed = False
         self._parent = parent
@@ -584,7 +584,6 @@ class Scheduler(QObject):
         d.setModal(False)
 
         self.recipe_model = RecipeModel()
-        self.db = db
         self.lock = QRecursiveMutex()
         self.download_queue = set()
 
@@ -608,14 +607,22 @@ class Scheduler(QObject):
         self.oldest = gconf['oldest_news']
         QTimer.singleShot(5 * 1000, self.oldest_check)
 
-    def database_changed(self, db):
+    @property
-        self.db = db
+    def db(self):
+        from calibre.gui2.ui import get_gui
+        gui = get_gui()
+        if gui is not None:
+            return gui.current_db
 
     def oldest_check(self):
         if self.oldest > 0:
             delta = timedelta(days=self.oldest)
+            db = self.db
+            if db is None:
+                QTimer.singleShot(5 * 1000, self.oldest_check)
+                return
             try:
-                ids = list(self.db.tags_older_than(_('News'),
+                ids = list(db.tags_older_than(_('News'),
                     delta, must_have_authors=['calibre']))
             except:
                 # Happens if library is being switched

src/calibre/gui2/layout.py

@@ -326,7 +326,7 @@ class MainWindowMixin:  # {{{
     def __init__(self, *args, **kwargs):
         pass
 
-    def init_main_window_mixin(self, db):
+    def init_main_window_mixin(self):
         self.setObjectName('MainWindow')
         self.setWindowIcon(QIcon.ic('lt.png'))
         self.setWindowTitle(__appname__)
@@ -340,7 +340,7 @@ class MainWindowMixin:  # {{{
         self.resize(1012, 740)
         self.location_manager = LocationManager(self)
 
-        self.iactions['Fetch News'].init_scheduler(db)
+        self.iactions['Fetch News'].init_scheduler()
 
         self.search_bar = SearchBar(self)
         self.bars_manager = BarsManager(self.donate_action,

src/calibre/gui2/ui.py

@@ -232,7 +232,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin,  # {{{
                 _('&Donate to support calibre'), self)
         for st in self.istores.values():
             st.do_genesis()
-        MainWindowMixin.init_main_window_mixin(self, db)
+        MainWindowMixin.init_main_window_mixin(self)
 
         # Jobs Button {{{
         self.job_manager = JobManager()