Keep running when the last dialog closes and stop workers before exit

With start_minimized enabled the main window is hidden, so a dialog
such as the resync prompt can be the only top-level window. Closing it
triggered Qt's default quit-on-last-window-closed, the application was
torn down while the worker QThread was still running, and Qt aborted
the process ("QThread: Destroyed while thread is still running"). The
onedrive client was left behind orphaned.

OneDriveGUI is a tray application, so it no longer quits when its last
window closes; quitting is explicit via the tray menu or the Quit
button. All workers are stopped from QApplication.aboutToQuit, so no
worker thread outlives the application, and the Quit action now ends
the event loop with QApplication.quit() instead of raising SystemExit
from a slot.

Fixes #297

src/onedrive_gui/OneDriveGUI.py

@@ -20,6 +20,10 @@ app = QApplication(sys.argv)
 app.setApplicationName("OneDriveGUI")
 app.setDesktopFileName("OneDriveGUI")
 app.setWindowIcon(QIcon(DIR_PATH + "/resources/images/icons8-cloud-80.png"))
+# OneDriveGUI lives in the system tray: closing a dialog while the main window is
+# hidden (e.g. the resync prompt with start_minimized) must not quit the app and
+# destroy the still-running worker threads (#297). Quitting is explicit.
+app.setQuitOnLastWindowClosed(False)
 
 
 from .options import gui_settings, global_config, version

src/onedrive_gui/main_window.py

@@ -206,6 +206,10 @@ class MainWindow(QMainWindow, Ui_MainWindow):
             "tooltip_text": "",
         }
 
+        # Stop the clients and their worker threads before the application is torn
+        # down; destroying a QThread that is still running aborts the process.
+        QApplication.instance().aboutToQuit.connect(self.stop_all_workers)
+
         self.refresh_process_status = QTimer()
         self.refresh_process_status.setSingleShot(False)
         self.refresh_process_status.timeout.connect(self.onedrive_process_status)
@@ -288,19 +292,16 @@ class MainWindow(QMainWindow, Ui_MainWindow):
 
         if close_question == QMessageBox.Yes:
             logging.info("Quitting OneDriveGUI")
-            workers_to_stop = []
-
-            for worker in workers:
-                workers_to_stop.append(worker)
-
-            for worker in workers_to_stop:
-                workers[worker].stop_worker()
-
-            sys.exit()
+            self.stop_all_workers()
+            QApplication.instance().quit()
 
         elif close_question == QMessageBox.No:
             logging.info("[GUI] Keeping OneDriveGUI running.")
 
+    def stop_all_workers(self):
+        for profile_name in list(workers):
+            workers[profile_name].stop_worker()
+
     def stop_onedrive_monitor(self, profile_name):
         if profile_name in workers:
             workers[profile_name].stop_worker()