Remove all timer deadlocks by using idle_add priority for them.

Add util.idle_timeout_add() to register timers with the same priority as
idle_add(). Change the IdleTimeout to also use the idle_add() priority.
This eliminates the chance of a timer blocking any idle_add from
running.

Change most timeout_add's to idle_timeout_add. Change the timer in
DownloadStatusModel::get_next() back to an idle_add.

src/gpodder/gtkui/download.py

@@ -195,10 +195,7 @@ class DownloadStatusModel(Gtk.ListStore):
     # as only the main thread is allowed to manipulate the list store.
     def get_next(self):
         dqr = DequeueRequest()
-        # this can not be idle_add because update_downloads_list() is called from a higher
-        # priority timeout_add and would spin forever, never calling this.
-        from gi.repository import GLib
-        GLib.timeout_add(0, self.__get_next, dqr)
+        util.idle_add(self.__get_next, dqr)
         return dqr.dequeue()
 
     def _work_gen(self):

src/gpodder/gtkui/interface/progress.py

@@ -50,6 +50,7 @@ class ProgressIndicator(object):
         self._initial_message = None
         self._initial_progress = None
         self._progress_set = False
+        # use timeout_add, not util.idle_timeout_add, so it updates before Gtk+ redraws the dialog
         self.source_id = GLib.timeout_add(self.DELAY, self._create_progress)
 
         self.set_max_ticks(max_ticks)
@@ -111,6 +112,7 @@ class ProgressIndicator(object):
         self._update_gui()
 
         # previous self.source_id timeout is removed when this returns False
+        # use timeout_add, not util.idle_timeout_add, so it updates before Gtk+ redraws the dialog
         self.source_id = GLib.timeout_add(self.INTERVAL, self._update_gui)
         return False
 

src/gpodder/gtkui/interface/searchtree.py

@@ -48,6 +48,7 @@ class SearchTree:
         if self.search_box.get_property('visible'):
             if self._search_timeout is not None:
                 GLib.source_remove(self._search_timeout)
+            # use timeout_add, not util.idle_timeout_add, so it updates the TreeView before background tasks
             self._search_timeout = GLib.timeout_add(
                     self.config.ui.gtk.live_search_delay,
                     self.set_search_term, editable.get_chars(0, -1))

src/gpodder/gtkui/main.py

@@ -2431,7 +2431,7 @@ class gPodder(BuilderWidget, dbus.service.Object):
         if remaining_seconds > 3600:
             # timeout an hour early in the event daylight savings changes the clock forward
             remaining_seconds = remaining_seconds - 3600
-        GLib.timeout_add(remaining_seconds * 1000, self.refresh_episode_dates)
+        util.idle_timeout_add(remaining_seconds * 1000, self.refresh_episode_dates)
 
     def update_podcast_list_model(self, urls=None, selected=False, select_url=None,
             sections_changed=False):
@@ -3821,8 +3821,7 @@ class gPodder(BuilderWidget, dbus.service.Object):
             interval = 60 * 1000 * self.config.auto.update.frequency
             logger.debug('Setting up auto update timer with interval %d.',
                     self.config.auto.update.frequency)
-            self._auto_update_timer_source_id = GLib.timeout_add(
-                    interval, self._on_auto_update_timer)
+            self._auto_update_timer_source_id = util.idle_timeout_add(interval, self._on_auto_update_timer)
 
     def _on_auto_update_timer(self):
         if self.config.check_connection and not util.connection_available():

src/gpodder/util.py

@@ -1320,8 +1320,25 @@ def idle_add(func, *args):
         func(*args)
 
 
+def idle_timeout_add(milliseconds, func, *args):
+    """Run a function in the main GUI thread at regular intervals, at idle priority
+
+    PRIORITY_HIGH           -100
+    PRIORITY_DEFAULT        0        timeout_add()
+    PRIORITY_HIGH_IDLE      100
+    resizing                110
+    redraw                  120
+    PRIORITY_DEFAULT_IDLE   200      idle_add()
+    PRIORITY_LOW            300
+    """
+    if not gpodder.ui.gtk:
+        raise Exception('util.idle_timeout_add() is only supported by Gtk+')
+    from gi.repository import GLib
+    return GLib.timeout_add(milliseconds, func, *args, priority=GLib.PRIORITY_DEFAULT_IDLE)
+
+
 class IdleTimeout(object):
-    """Run a function in the main GUI thread at regular intervals since the last run
+    """Run a function in the main GUI thread at regular intervals since the last run, at idle priority
 
     A simple timeout_add() continuously calls the function if it exceeds the interval,
     which lags the UI and prevents idle_add() calls from happening. This class restarts
@@ -1333,13 +1350,13 @@ class IdleTimeout(object):
         self.milliseconds = milliseconds
         self.func = func
         from gi.repository import GLib
-        self.id = GLib.timeout_add(milliseconds, self._callback, *args)
+        self.id = GLib.timeout_add(milliseconds, self._callback, *args, priority=GLib.PRIORITY_DEFAULT_IDLE)
 
     def _callback(self, *args):
         self.cancel()
         if self.func(*args):
             from gi.repository import GLib
-            self.id = GLib.timeout_add(self.milliseconds, self._callback, *args)
+            self.id = GLib.timeout_add(self.milliseconds, self._callback, *args, priority=GLib.PRIORITY_DEFAULT_IDLE)
 
     def cancel(self):
         if self.id: