implement a basic Start/StopListening

This implements the ListeningStopped signal (especially the EAGAIN if we're
already listening) but does not yet actually trigger the listening on the
device.

There is still no timeout, and no signal gets emitted.
The current way of testing this is:
- call StartListening() on the DBus device
- start discovery on the adapter by some other mean
- press the button on the device -> the sync will happen
- call StopDiscovery()
- press the button on the device -> the sync will *not* happen

tuhi.py

@@ -119,6 +119,10 @@ class TuhiDevice(GObject.Object):
         self._tuhi_dbus_device = device
         self._tuhi_dbus_device.connect('pair-requested', self._on_pair_requested)
 
+    @property
+    def listening(self):
+        return self._tuhi_dbus_device.listening
+
     def connect_device(self):
         self._bluez_device.connect_device()
 
@@ -264,8 +268,12 @@ class Tuhi(GObject.Object):
                 d.dbus_device = self.server.create_device(d)
                 self.devices[bluez_device.address] = d
 
+        d = self.devices[bluez_device.address]
+
         if Tuhi._is_pairing_device(bluez_device):
             logger.debug('{}: call Pair() on device'.format(bluez_device.objpath))
+        elif d.listening:
+            d.connect_device()
 
 
 def main(args):

tuhi/dbusserver.py

@@ -12,6 +12,7 @@
 #
 
 import logging
+import errno
 
 from gi.repository import GObject, Gio, GLib
 
@@ -45,6 +46,9 @@ INTROSPECTION_XML = """
     <property type='s' name='Name' access='read'/>
     <property type='s' name='Address' access='read'/>
     <property type='uu' name='Dimensions' access='read'/>
+    <property type='b' name='Listening' access='read'>
+      <annotation name='org.freedesktop.DBus.Property.EmitsChangedSignal' value='true'/>
+    </property>
     <property type='u' name='DrawingsAvailable' access='read'>
       <annotation name='org.freedesktop.DBus.Property.EmitsChangedSignal' value='true'/>
     </property>
@@ -53,7 +57,11 @@ INTROSPECTION_XML = """
       <arg name='result' type='i' direction='out'/>
     </method>
 
-    <method name='Listen'>
+    <method name='StartListening'>
+      <annotation name='org.freedesktop.DBus.Method.NoReply' value='true'/>
+    </method>
+
+    <method name='StopListening'>
       <annotation name='org.freedesktop.DBus.Method.NoReply' value='true'/>
     </method>
 
@@ -94,6 +102,7 @@ class TuhiDBusDevice(GObject.Object):
         self.width, self.height = 0, 0
         self.drawings = []
         self.paired = device.paired
+        self._listening = False
         objpath = device.address.replace(':', '_')
         self.objpath = "{}/{}".format(BASE_PATH, objpath)
 
@@ -101,6 +110,34 @@ class TuhiDBusDevice(GObject.Object):
         self._dbusid = self._register_object(connection)
         device.connect('notify::paired', self._on_device_paired)
 
+    @GObject.Property
+    def listening(self):
+        return self._listening
+
+    @listening.setter
+    def listening(self, value):
+        if self._listening == value:
+            return
+
+        self._listening = value
+
+        props = GLib.VariantBuilder(GLib.VariantType('a{sv}'))
+        de = GLib.Variant.new_dict_entry(GLib.Variant.new_string('Listening'),
+                                         GLib.Variant.new_variant(
+                                             GLib.Variant.new_boolean(value)))
+        props.add_value(de)
+        props = props.end()
+        inval_props = GLib.VariantBuilder(GLib.VariantType('as'))
+        inval_props = inval_props.end()
+
+        self._connection.emit_signal(None, self.objpath,
+                                     "org.freedesktop.DBus.Properties",
+                                     "PropertiesChanged",
+                                     GLib.Variant.new_tuple(
+                                         GLib.Variant.new_string(INTF_DEVICE),
+                                         props,
+                                         inval_props))
+
     @GObject.Property
     def paired(self):
         return self._paired
@@ -132,8 +169,11 @@ class TuhiDBusDevice(GObject.Object):
             self._pair()
             result = GLib.Variant.new_int32(0)
             invocation.return_value(GLib.Variant.new_tuple(result))
-        elif methodname == 'Listen':
-            self._listen()
+        elif methodname == 'StartListening':
+            self._start_listening(connection, sender)
+            invocation.return_value()
+        elif methodname == 'StopListening':
+            self._stop_listening(connection, sender)
             invocation.return_value()
         elif methodname == 'GetJSONData':
             json = GLib.Variant.new_string(self._json_data(args))
@@ -153,6 +193,8 @@ class TuhiDBusDevice(GObject.Object):
             return GLib.Variant.new_tuple(w, h)
         elif propname == 'DrawingsAvailable':
             return GLib.Variant.new_uint32(len(self.drawings))
+        elif propname == 'Listening':
+            return GLib.Variant.new_boolean(self.listening)
 
         return None
 
@@ -165,10 +207,29 @@ class TuhiDBusDevice(GObject.Object):
     def _on_device_paired(self, device, pspec):
         self.paired = device.paired
 
-    def _listen(self):
-        # FIXME: start listen asynchronously
-        # FIXME: update property when listen finishes
-        pass
+    def _start_listening(self, connection, sender):
+        if self.listening:
+            logger.debug("{} - already listening".format(self))
+            status = GLib.Variant.new_int32(-errno.EAGAIN)
+            status = GLib.Variant.new_tuple(status)
+            connection.emit_signal(sender, self.objpath, INTF_DEVICE,
+                                   "ListeningStopped", status)
+            return
+
+        # FIXME: notify the server to start discovery
+        self.listening = True
+
+    def _stop_listening(self, connection, sender):
+        if not self.listening:
+            return
+
+        # FIXME: notify the server to stop discovery
+        self.listening = False
+
+        status = GLib.Variant.new_int32(0)
+        status = GLib.Variant.new_tuple(status)
+        connection.emit_signal(sender, self.objpath, INTF_DEVICE,
+                               "ListeningStopped", status)
 
     def _json_data(self, args):
         index = args[0]