WIP of #125: screen locking detection

separate backends implemented via a 'multi' meta-backend.
Uses config like this:

```
backends: [multi]
multi:
    locked:
        pushover:
            user_key: user-api-key
    unfocused:
        default: {}
    focused: {}

```
This config would cause no notifications if the shell is focused, desktop
notifications when unfocused, and pushover notifications when the screen is
locked. Freaking magic. 🎉

ntfy/backends/multi.py

@@ -0,0 +1,25 @@
+from importlib import import_module
+try:
+    from ..terminal import is_focused
+except ImportError:
+    def is_focused():
+        return True
+from ..screensaver import is_locked
+
+
+def notify(title,
+           message,
+           locked=None,
+           focused=None,
+           unfocused=None,
+           retcode=None):
+    for condition, options in ((is_locked, locked),
+                               (is_focused, focused),
+                               (lambda: not is_focused(), unfocused)):
+        for backend_name, backend_options in options.items():
+            if not condition():
+                continue
+            backend = import_module('ntfy.backends.{}'.format(
+                backend_options.get('backend', backend_name)))
+            backend_options.pop('backend', None)
+            backend.notify(title, message, retcode=retcode, **backend_options)

ntfy/cli.py

@@ -31,6 +31,7 @@
 
     def is_focused():
         return True
+from .screensaver import is_locked
 
 
 def run_cmd(args):
@@ -62,6 +63,8 @@ def run_cmd(args):
         retcode = process.returncode
     if args.longer_than is not None and duration <= args.longer_than:
         return None, None
+    if args.locked_only and not is_locked():
+        return None, None
     if args.unfocused_only and is_focused():
         return None, None
     message = _result_message(args.command if not args.hide_command else None,
@@ -228,6 +231,12 @@ def default_sender(args):
     type=int,
     metavar='N',
     help="Only notify if the command runs longer than N seconds")
+done_parser.add_argument(
+    '--locked-only',
+    action='store_true',
+    default=False,
+    dest='locked_only',
+    help='Only notify if the screen is locked')
 done_parser.add_argument(
     '-b',
     '--background-only',
@@ -281,6 +290,12 @@ def default_sender(args):
     type=int,
     metavar='N',
     help="Only notify if the command runs longer than N seconds")
+shell_integration_parser.add_argument(
+    '--locked-only',
+    action='store_true',
+    default=False,
+    dest='locked_only',
+    help='Only notify if the screen is locked')
 shell_integration_parser.add_argument(
     '-f',
     '--foreground-too',

ntfy/screensaver.py

@@ -0,0 +1,106 @@
+from shlex import split
+from subprocess import check_output, check_call, CalledProcessError, PIPE
+
+# some adapted from
+# https://github.com/mtorromeo/xdg-utils/blob/master/scripts/xdg-screensaver.in#L540
+
+
+def xscreensaver_detect():
+    try:
+        check_call(split('pgrep xscreensaver'), stdout=PIPE)
+    except (CalledProcessError, OSError):
+        return False
+    else:
+        return True
+
+
+def xscreensaver_is_locked():
+    return 'screen locked' in check_output(split('xscreensaver-command -time'))
+
+
+def lightlocker_detect():
+    try:
+        check_call(split('pgrep light-locker'), stdout=PIPE)
+    except (CalledProcessError, OSError):
+        return False
+    else:
+        return True
+
+
+def lightlocker_is_active():
+    return 'The screensaver is active' in check_output(split(
+        'light-locker-command -q'))
+
+
+def gnomescreensaver_detect():
+    try:
+        import dbus
+    except ImportError:
+        return False
+    bus = dbus.SessionBus()
+    dbus_obj = bus.get_object('org.freedesktop.DBus',
+                              '/org/freedesktop/DBus')
+    dbus_iface = dbus.Interface(dbus_obj,
+                                dbus_interface='org.freedesktop.DBus')
+    try:
+        dbus_iface.GetNameOwner('org.gnome.ScreenSaver')
+    except dbus.DBusException as e:
+        if e.get_dbus_name() == 'org.freedesktop.DBus.Error.NameHasNoOwner':
+            return False
+        else:
+            raise e
+    else:
+        return True
+
+
+def gnomescreensaver_is_locked():
+    import dbus
+    bus = dbus.SessionBus()
+    dbus_obj = bus.get_object('org.gnome.ScreenSaver',
+                              '/org/gnome/ScreenSaver')
+    dbus_iface = dbus.Interface(dbus_obj,
+                                dbus_interface='org.gnome.ScreenSaver')
+    return bool(dbus_iface.GetActive())
+
+
+def matescreensaver_detect():
+    try:
+        import dbus
+    except ImportError:
+        return False
+    bus = dbus.SessionBus()
+    dbus_obj = bus.get_object('org.freedesktop.DBus',
+                              '/org/freedesktop/DBus')
+    dbus_iface = dbus.Interface(dbus_obj,
+                                dbus_interface='org.freedesktop.DBus')
+    try:
+        dbus_iface.GetNameOwner('org.mate.ScreenSaver')
+    except dbus.DBusException as e:
+        if e.get_dbus_name() == 'org.freedesktop.DBus.Error.NameHasNoOwner':
+            return False
+        else:
+            raise e
+    else:
+        return True
+
+
+def matescreensaver_is_locked():
+    import dbus
+    bus = dbus.SessionBus()
+    dbus_obj = bus.get_object('org.mate.ScreenSaver',
+                              '/org/mate/ScreenSaver')
+    dbus_iface = dbus.Interface(dbus_obj,
+                                dbus_interface='org.mate.ScreenSaver')
+    return bool(dbus_iface.GetActive())
+
+
+def is_locked():
+    if xscreensaver_detect():
+        return xscreensaver_is_locked()
+    if lightlocker_detect():
+        return lightlocker_is_active()
+    if gnomescreensaver_detect():
+        return gnomescreensaver_is_locked()
+    if matescreensaver_detect():
+        return matescreensaver_is_locked()
+    return True

tests/test_cli.py

@@ -24,6 +24,7 @@ def test_default(self, mock_Popen):
         args.pid = None
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         self.assertEqual(('"true" succeeded in 0:00 minutes', 0), run_cmd(args))
 
     @patch('ntfy.cli.Popen')
@@ -36,6 +37,7 @@ def test_emoji(self, mock_Popen):
         args.no_emoji = False
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         self.assertEqual((':white_check_mark: "true" succeeded in 0:00 minutes', 0),
                          run_cmd(args))
 
@@ -55,6 +57,7 @@ def test_longerthan(self, mock_Popen):
         args.pid = None
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         self.assertEqual((None, None), run_cmd(args))
 
     @patch('ntfy.cli.Popen')
@@ -66,6 +69,7 @@ def test_failure(self, mock_Popen):
         args.pid = None
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         self.assertEqual(('"false" failed (code 42) in 0:00 minutes', 42), run_cmd(args))
 
     @patch('ntfy.cli.Popen')
@@ -77,6 +81,7 @@ def test_stdout(self, mock_Popen):
         args.pid = None
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         # not actually used
         args.stdout = True
         args.stderr = False
@@ -91,6 +96,7 @@ def test_stderr(self, mock_Popen):
         args.pid = None
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         # not actually used
         args.stdout = False
         args.stderr = True
@@ -105,6 +111,7 @@ def test_stdout_and_stderr(self, mock_Popen):
         args.pid = None
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         # not actually used
         args.stdout = True
         args.stderr = True
@@ -119,6 +126,7 @@ def test_failure_stdout_and_stderr(self, mock_Popen):
         args.pid = None
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         # not actually used
         args.stdout = True
         args.stderr = True
@@ -143,6 +151,7 @@ def test_formatter(self):
         args.longer_than = -1
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         self.assertEqual(('"true" succeeded in 1:05 minutes', 0), run_cmd(args))
 
     def test_formatter_failure(self):
@@ -153,6 +162,7 @@ def test_formatter_failure(self):
         args.longer_than = -1
         args.unfocused_only = False
         args.hide_command = False
+        args.locked_only = False
         self.assertEqual(('"false" failed (code 1) in 0:10 minutes', 1), run_cmd(args))
 
 
@@ -186,6 +196,7 @@ def test_watch_pid(self, mock_process):
         args = MagicMock()
         args.pid = 1
         args.unfocused_only = False
+        args.locked_only = False
         self.assertEqual('PID[1]: "cmd" finished in 0:00 minutes',
                          run_cmd(args)[0])