qt: even more clean-up before exiting

related: https://github.com/spesmilo/electrum/issues/6889#issuecomment-812776695

electrum/gui/qt/__init__.py

@@ -88,6 +88,10 @@ class QNetworkUpdatedSignalObject(QObject):
 
 class ElectrumGui(Logger):
 
+    network_dialog: Optional['NetworkDialog']
+    lightning_dialog: Optional['LightningDialog']
+    watchtower_dialog: Optional['WatchtowerDialog']
+
     @profiler
     def __init__(self, config: 'SimpleConfig', daemon: 'Daemon', plugins: 'Plugins'):
         set_language(config.get('language', get_default_language()))
@@ -111,6 +115,7 @@ class ElectrumGui(Logger):
         self.app = QElectrumApplication(sys.argv)
         self.app.installEventFilter(self.efilter)
         self.app.setWindowIcon(read_QIcon("electrum.png"))
+        self._cleaned_up = False
         # timer
         self.timer = QTimer(self.app)
         self.timer.setSingleShot(False)
@@ -199,15 +204,40 @@ class ElectrumGui(Logger):
                 for w in self.windows:
                     w.hide()
 
-    def close(self):
-        for window in self.windows:
+    def _cleanup_before_exit(self):
+        if self._cleaned_up:
+            return
+        self._cleaned_up = True
+        self.app.new_window_signal.disconnect()
+        self.efilter = None
+        # If there are still some open windows, try to clean them up.
+        for window in list(self.windows):
             window.close()
+            window.clean_up()
         if self.network_dialog:
             self.network_dialog.close()
+            self.network_dialog.clean_up()
+            self.network_dialog = None
+        self.network_updated_signal_obj = None
         if self.lightning_dialog:
             self.lightning_dialog.close()
+            self.lightning_dialog = None
         if self.watchtower_dialog:
             self.watchtower_dialog.close()
+            self.watchtower_dialog = None
+        # Shut down the timer cleanly
+        self.timer.stop()
+        self.timer = None
+        # clipboard persistence. see http://www.mail-archive.com/pyqt@riverbankcomputing.com/msg17328.html
+        event = QtCore.QEvent(QtCore.QEvent.Clipboard)
+        self.app.sendEvent(self.app.clipboard(), event)
+        if self.tray:
+            self.tray.hide()
+            self.tray.deleteLater()
+            self.tray = None
+
+    def close(self):
+        self._cleanup_before_exit()
         self.app.quit()
 
     def new_window(self, path, uri=None):
@@ -232,8 +262,10 @@ class ElectrumGui(Logger):
             self.network_dialog.show()
             self.network_dialog.raise_()
             return
-        self.network_dialog = NetworkDialog(self.daemon.network, self.config,
-                                self.network_updated_signal_obj)
+        self.network_dialog = NetworkDialog(
+            network=self.daemon.network,
+            config=self.config,
+            network_updated_signal_obj=self.network_updated_signal_obj)
         self.network_dialog.show()
 
     def _create_window_for_wallet(self, wallet):
@@ -382,18 +414,7 @@ class ElectrumGui(Logger):
         self.app.lastWindowClosed.connect(quit_after_last_window)
 
         def clean_up():
-            # If there are still some open windows, try to clean them up.
-            for window in list(self.windows):
-                window.clean_up()
-            # Shut down the timer cleanly
-            self.timer.stop()
-            # clipboard persistence. see http://www.mail-archive.com/pyqt@riverbankcomputing.com/msg17328.html
-            event = QtCore.QEvent(QtCore.QEvent.Clipboard)
-            self.app.sendEvent(self.app.clipboard(), event)
-            if self.tray:
-                self.tray.hide()
-                self.tray.deleteLater()
-                self.tray = None
+            self._cleanup_before_exit()
         self.app.aboutToQuit.connect(clean_up)
 
         # main loop

electrum/gui/qt/network_dialog.py

@@ -27,6 +27,7 @@ import socket
 import time
 from enum import IntEnum
 from typing import Tuple, TYPE_CHECKING
+import threading
 
 from PyQt5.QtCore import Qt, pyqtSignal, QThread
 from PyQt5.QtWidgets import (QTreeWidget, QTreeWidgetItem, QMenu, QGridLayout, QComboBox,
@@ -53,7 +54,7 @@ protocol_names = ['TCP', 'SSL']
 protocol_letters = 'ts'
 
 class NetworkDialog(QDialog):
-    def __init__(self, network, config, network_updated_signal_obj):
+    def __init__(self, *, network: Network, config: 'SimpleConfig', network_updated_signal_obj):
         QDialog.__init__(self)
         self.setWindowTitle(_('Network'))
         self.setMinimumSize(500, 500)
@@ -68,19 +69,20 @@ class NetworkDialog(QDialog):
         self._cleaned_up = False
 
     def on_network(self, event, *args):
-        self.network_updated_signal_obj.network_updated_signal.emit(event, args)
+        signal_obj = self.network_updated_signal_obj
+        if signal_obj:
+            signal_obj.network_updated_signal.emit(event, args)
 
     def on_update(self):
         self.nlayout.update()
 
-    def closeEvent(self, event):
-        if not self._cleaned_up:
-            self._cleaned_up = True
-            self.clean_up()
-        event.accept()
-
     def clean_up(self):
+        if self._cleaned_up:
+            return
+        self._cleaned_up = True
         self.nlayout.clean_up()
+        self.network_updated_signal_obj.network_updated_signal.disconnect()
+        self.network_updated_signal_obj = None
 
 
 class NodesListWidget(QTreeWidget):
@@ -320,8 +322,7 @@ class NetworkChoiceLayout(object):
     def clean_up(self):
         if self.td:
             self.td.found_proxy.disconnect()
-            self.td.exit()
-            self.td.wait()
+            self.td.stop()
             self.td = None
 
     def check_disable_proxy(self, b):
@@ -463,6 +464,7 @@ class TorDetector(QThread):
 
     def __init__(self):
         QThread.__init__(self)
+        self._stop_event = threading.Event()
 
     def run(self):
         # Probable ports for Tor to listen at
@@ -475,7 +477,14 @@ class TorDetector(QThread):
                     break
             else:
                 self.found_proxy.emit(None)
-            time.sleep(10)
+            stopping = self._stop_event.wait(10)
+            if stopping:
+                return
+
+    def stop(self):
+        self._stop_event.set()
+        self.exit()
+        self.wait()
 
     @staticmethod
     def is_tor_port(net_addr: Tuple[str, int]) -> bool: