In Qt 6 QApplication::exit now behaves like QApplication::quit in Qt 5

src/calibre/gui2/splash_screen.py

@@ -113,7 +113,7 @@ class SplashScreen(QSplashScreen):
         if not self.develop:
             return QSplashScreen.keyPressEvent(self, ev)
         ev.accept()
-        QApplication.instance().quit()
+        QApplication.instance().exit()
 
 
 def main():

src/calibre/gui2/tweak_book/boss.py

@@ -1882,7 +1882,7 @@ class Boss(QObject):
         if not self.confirm_quit():
             return False
         self.shutdown()
-        QApplication.instance().quit()
+        QApplication.instance().exit()
         return True
 
     def confirm_quit(self):
@@ -1935,7 +1935,7 @@ class Boss(QObject):
     def check_terminal_save(self):
         if self.doing_terminal_save and not self.save_manager.has_tasks:  # terminal save could have been aborted
             self.shutdown()
-            QApplication.instance().quit()
+            QApplication.instance().exit()
 
     def shutdown(self):
         self.save_state()

src/calibre/gui2/ui.py

@@ -1086,7 +1086,7 @@ class Main(MainWindow, MainWindowMixin, DeviceMixin, EmailMixin,  # {{{
         if self.system_tray_icon is not None and self.restart_after_quit:
             # Needed on windows to prevent multiple systray icons
             self.system_tray_icon.setVisible(False)
-        QApplication.instance().quit()
+        QApplication.instance().exit()
 
     def donate(self, *args):
         from calibre.utils.localization import localize_website_link