fix: Correct D-Bus signal handling and agent capability

Co-authored-by: aider (gemini/gemini-2.5-pro) <aider@aider.chat>

main.py

@@ -14,7 +14,7 @@ from dbus_next.aio import MessageBus
 from dbus_next.service import ServiceInterface, method
 from dbus_next.constants import BusType
 from dbus_next.errors import DBusError
-from dbus_next import Variant
+from dbus_next import Variant, Message, MessageType
 
 
 bus = None
@@ -27,7 +27,7 @@ DEVICE_IFACE = 'org.bluez.Device1'
 AGENT_IFACE = 'org.bluez.Agent1'
 AGENT_MANAGER_IFACE = 'org.bluez.AgentManager1'
 AGENT_PATH = '/io/bluetooth_speaker/agent'
-CAPABILITY = 'NoInputNoOutput'
+CAPABILITY = 'DisplayYesNo'
 CALLS_SERVICE_UUID = '0000111e-0000-1000-8000-00805f9b34fb'
 AUDIO_SERVICE_UUID = '0000110d-0000-1000-8000-00805f9b34fb'
 
@@ -167,18 +167,27 @@ async def monitor_unpairing():
 
     adapter_iface = adapter_obj.get_interface(ADAPTER_IFACE)
 
-    def _properties_changed_handler(interface_name, changed_properties, invalidated_properties, msg):
+    def _properties_changed_handler(msg):
+        if msg.message_type != MessageType.SIGNAL or msg.member != 'PropertiesChanged' or msg.interface != 'org.freedesktop.DBus.Properties':
+            return
+
+        interface_name, changed_properties, invalidated_properties = msg.body
+
         if interface_name == DEVICE_IFACE and 'Paired' in changed_properties and not changed_properties['Paired'].value:
             device_path = msg.path
             logging.info(f"Device {device_path} was unpaired by the remote host. Removing it.")
             asyncio.create_task(adapter_iface.call_remove_device(device_path))
 
-    bus.add_signal_receiver(
-        _properties_changed_handler,
-        signal_name='PropertiesChanged',
-        dbus_interface='org.freedesktop.DBus.Properties',
-        path_namespace='/org/bluez'
-    )
+    bus.add_message_handler(_properties_changed_handler)
+
+    await bus.call(
+        Message(
+            destination='org.freedesktop.DBus',
+            path='/org/freedesktop/DBus',
+            interface='org.freedesktop.DBus',
+            member='AddMatch',
+            signature='s',
+            body=[f"type='signal',interface='org.freedesktop.DBus.Properties',member='PropertiesChanged',path_namespace='/org/bluez'"]))
     
     # Keep the task alive to listen for signals
     while True: