Restart timers after hibernation/sleep (#1511)

Schedules get missed, if system has been in hibernation/sleep state as
described in https://github.com/borgbase/vorta/issues/1214
Although, timers should be refreshed every 15min, it seems that all timers get
deranged by sleep state and schedules is still missed in most cases. This seems
to be a general issue with the underlying QTimer implementation.

This fix doesn't distinguish host OS and has only by tested on Linux.
If 'org.freedesktop.login1.Manager' is not available, Vorta simple doesn't
get notified if system awakes again. No no impact on other OS is expected

Co-authored-by: yfprojects <62463991+real-yfprojects@users.noreply.github.com>

src/vorta/scheduler.py

@@ -4,7 +4,7 @@ import threading
 from datetime import datetime as dt
 from datetime import timedelta
 from typing import Dict, NamedTuple, Optional, Tuple, Union
-from PyQt5 import QtCore
+from PyQt5 import QtCore, QtDBus
 from PyQt5.QtCore import QTimer
 from PyQt5.QtWidgets import QApplication
 from vorta import application
@@ -58,6 +58,25 @@ class VortaScheduler(QtCore.QObject):
         # connect signals
         self.app.backup_finished_event.connect(lambda res: self.set_timer_for_profile(res['params']['profile_id']))
 
+        # connect to `systemd-logind` to receive sleep/resume events
+        # The signal `PrepareForSleep` will be emitted before and after hibernation.
+        service = "org.freedesktop.login1"
+        path = "/org/freedesktop/login1"
+        interface = "org.freedesktop.login1.Manager"
+        name = "PrepareForSleep"
+        bus = QtDBus.QDBusConnection.systemBus()
+        if bus.isConnected() and bus.interface().isServiceRegistered(service).value():
+            self.bus = bus
+            self.bus.connect(service, path, interface, name, "b", self.loginSuspendNotify)
+        else:
+            logger.warn('Failed to connect to DBUS interface to detect sleep/resume events')
+
+    @QtCore.pyqtSlot(bool)
+    def loginSuspendNotify(self, suspend: bool):
+        if not suspend:
+            logger.debug("Got login suspend/resume notification")
+            self.reload_all_timers()
+
     def tr(self, *args, **kwargs):
         scope = self.__class__.__name__
         return translate(scope, *args, **kwargs)