Implemented call transfer

blink/contacts.py

@@ -3030,6 +3030,8 @@ class ContactDetailModel(QAbstractListModel):
 
 
 class ContactListView(QListView):
+    implements(IObserver)
+
     def __init__(self, parent=None):
         super(ContactListView, self).__init__(parent)
         self.setItemDelegate(ContactDelegate(self))
@@ -3053,9 +3055,14 @@ class ContactListView(QListView):
         self.actions.send_files = QAction("Send File(s)...", self, triggered=self._AH_SendFiles)
         self.actions.request_screen = QAction("Request Screen", self, triggered=self._AH_RequestScreen)
         self.actions.share_my_screen = QAction("Share My Screen", self, triggered=self._AH_ShareMyScreen)
+        self.actions.transfer_call = QAction("Transfer Active Call", self, triggered=self._AH_TransferCall)
         self.drop_indicator_index = QModelIndex()
         self.needs_restore = False
         self.doubleClicked.connect(self._SH_DoubleClicked)  # activated is emitted on single click
+        notification_center = NotificationCenter()
+        notification_center.add_observer(self, 'BlinkSessionDidChangeState')
+        notification_center.add_observer(self, 'BlinkSessionDidRemoveStream')
+        notification_center.add_observer(self, 'BlinkActiveSessionDidChange')
 
     def selectionChanged(self, selected, deselected):
         super(ContactListView, self).selectionChanged(selected, deselected)
@@ -3125,6 +3132,7 @@ class ContactListView(QListView):
             menu.addAction(self.actions.send_files)
             menu.addAction(self.actions.request_screen)
             menu.addAction(self.actions.share_my_screen)
+            menu.addAction(self.actions.transfer_call)
             menu.addSeparator()
             menu.addAction(self.actions.add_group)
             menu.addAction(self.actions.add_contact)
@@ -3133,7 +3141,9 @@ class ContactListView(QListView):
             menu.addAction(self.actions.undo_last_delete)
             self.actions.undo_last_delete.setText(undo_delete_text)
             account_manager = AccountManager()
+            session_manager = SessionManager()
             can_call = account_manager.default_account is not None and contact.uri is not None
+            can_transfer = contact.uri is not None and session_manager.active_session is not None and session_manager.active_session.state == 'connected'
             self.actions.start_audio_call.setEnabled(can_call)
             self.actions.start_video_call.setEnabled(can_call)
             self.actions.start_chat_session.setEnabled(can_call)
@@ -3141,6 +3151,7 @@ class ContactListView(QListView):
             self.actions.send_files.setEnabled(can_call)
             self.actions.request_screen.setEnabled(can_call)
             self.actions.share_my_screen.setEnabled(can_call)
+            self.actions.transfer_call.setEnabled(can_transfer)
             self.actions.edit_item.setEnabled(contact.editable)
             self.actions.delete_item.setEnabled(contact.deletable)
             self.actions.undo_last_delete.setEnabled(len(model.deleted_items) > 0)
@@ -3385,6 +3396,11 @@ class ContactListView(QListView):
         session_manager = SessionManager()
         session_manager.create_session(contact, contact.uri, [StreamDescription('screen-sharing', mode='server'), StreamDescription('audio')])
 
+    def _AH_TransferCall(self):
+        contact = self.selectionModel().selectedIndexes()[0].data(Qt.UserRole)
+        session_manager = SessionManager()
+        session_manager.active_session.transfer(contact.uri)
+
     def _DH_ApplicationXBlinkGroupList(self, event, index, rect, item):
         model = self.model()
         groups = model.items[GroupList]
@@ -3455,8 +3471,39 @@ class ContactListView(QListView):
             session_manager = SessionManager()
             session_manager.create_session(item, item.uri, item.preferred_media.stream_descriptions, connect=item.preferred_media.autoconnect)
 
+    @run_in_gui_thread
+    def handle_notification(self, notification):
+        handler = getattr(self, '_NH_%s' % notification.name, Null)
+        handler(notification)
+
+    def _NH_BlinkSessionDidChangeState(self, notification):
+        session_manager = SessionManager()
+        if notification.sender is session_manager.active_session and self.context_menu.isVisible():
+            selected_items = [index.data(Qt.UserRole) for index in self.selectionModel().selectedIndexes()]
+            if len(selected_items) == 1 and isinstance(selected_items[0], Contact):
+                contact = selected_items[0]
+                self.actions.transfer_call.setEnabled(contact.uri is not None and notification.sender.state == 'connected')
+
+    def _NH_BlinkSessionDidRemoveStream(self, notification):
+        session_manager = SessionManager()
+        if notification.sender is session_manager.active_session and self.context_menu.isVisible():
+            selected_items = [index.data(Qt.UserRole) for index in self.selectionModel().selectedIndexes()]
+            if len(selected_items) == 1 and isinstance(selected_items[0], Contact):
+                contact = selected_items[0]
+                self.actions.transfer_call.setEnabled(contact.uri is not None and 'audio' in notification.sender.streams)
+
+    def _NH_BlinkActiveSessionDidChange(self, notification):
+        if self.context_menu.isVisible():
+            selected_items = [index.data(Qt.UserRole) for index in self.selectionModel().selectedIndexes()]
+            if len(selected_items) == 1 and isinstance(selected_items[0], Contact):
+                contact = selected_items[0]
+                active_session = notification.data.active_session
+                self.actions.transfer_call.setEnabled(contact.uri is not None and active_session is not None and active_session.state == 'connected')
+
 
 class ContactSearchListView(QListView):
+    implements(IObserver)
+
     def __init__(self, parent=None):
         super(ContactSearchListView, self).__init__(parent)
         self.setItemDelegate(ContactDelegate(self))
@@ -3478,8 +3525,13 @@ class ContactSearchListView(QListView):
         self.actions.send_files = QAction("Send File(s)...", self, triggered=self._AH_SendFiles)
         self.actions.request_screen = QAction("Request Screen", self, triggered=self._AH_RequestScreen)
         self.actions.share_my_screen = QAction("Share My Screen", self, triggered=self._AH_ShareMyScreen)
+        self.actions.transfer_call = QAction("Transfer Active Call", self, triggered=self._AH_TransferCall)
         self.drop_indicator_index = QModelIndex()
         self.doubleClicked.connect(self._SH_DoubleClicked)  # activated is emitted on single click
+        notification_center = NotificationCenter()
+        notification_center.add_observer(self, 'BlinkSessionDidChangeState')
+        notification_center.add_observer(self, 'BlinkSessionDidRemoveStream')
+        notification_center.add_observer(self, 'BlinkActiveSessionDidChange')
 
     def selectionChanged(self, selected, deselected):
         super(ContactSearchListView, self).selectionChanged(selected, deselected)
@@ -3536,13 +3588,16 @@ class ContactSearchListView(QListView):
             menu.addAction(self.actions.send_files)
             menu.addAction(self.actions.request_screen)
             menu.addAction(self.actions.share_my_screen)
+            menu.addAction(self.actions.transfer_call)
             menu.addSeparator()
             menu.addAction(self.actions.edit_item)
             menu.addAction(self.actions.delete_item)
             menu.addAction(self.actions.undo_last_delete)
             self.actions.undo_last_delete.setText(undo_delete_text)
             account_manager = AccountManager()
+            session_manager = SessionManager()
             can_call = account_manager.default_account is not None and contact.uri is not None
+            can_transfer = contact.uri is not None and session_manager.active_session is not None and session_manager.active_session.state == 'connected'
             self.actions.start_audio_call.setEnabled(can_call)
             self.actions.start_video_call.setEnabled(can_call)
             self.actions.start_chat_session.setEnabled(can_call)
@@ -3550,6 +3605,7 @@ class ContactSearchListView(QListView):
             self.actions.send_files.setEnabled(can_call)
             self.actions.request_screen.setEnabled(can_call)
             self.actions.share_my_screen.setEnabled(can_call)
+            self.actions.transfer_call.setEnabled(can_transfer)
             self.actions.edit_item.setEnabled(contact.editable)
             self.actions.delete_item.setEnabled(contact.deletable)
             self.actions.undo_last_delete.setEnabled(len(source_model.deleted_items) > 0)
@@ -3730,6 +3786,11 @@ class ContactSearchListView(QListView):
         session_manager = SessionManager()
         session_manager.create_session(contact, contact.uri, [StreamDescription('screen-sharing', mode='server'), StreamDescription('audio')])
 
+    def _AH_TransferCall(self):
+        contact = self.selectionModel().selectedIndexes()[0].data(Qt.UserRole)
+        session_manager = SessionManager()
+        session_manager.active_session.transfer(contact.uri)
+
     def _DH_TextUriList(self, event, index, rect, item):
         if index.isValid():
             event.accept(rect)
@@ -3746,8 +3807,39 @@ class ContactSearchListView(QListView):
             session_manager = SessionManager()
             session_manager.create_session(item, item.uri, item.preferred_media.stream_descriptions, connect=item.preferred_media.autoconnect)
 
+    @run_in_gui_thread
+    def handle_notification(self, notification):
+        handler = getattr(self, '_NH_%s' % notification.name, Null)
+        handler(notification)
+
+    def _NH_BlinkSessionDidChangeState(self, notification):
+        session_manager = SessionManager()
+        if notification.sender is session_manager.active_session and self.context_menu.isVisible():
+            selected_items = [index.data(Qt.UserRole) for index in self.selectionModel().selectedIndexes()]
+            if len(selected_items) == 1 and isinstance(selected_items[0], Contact):
+                contact = selected_items[0]
+                self.actions.transfer_call.setEnabled(contact.uri is not None and notification.sender.state == 'connected')
+
+    def _NH_BlinkSessionDidRemoveStream(self, notification):
+        session_manager = SessionManager()
+        if notification.sender is session_manager.active_session and self.context_menu.isVisible():
+            selected_items = [index.data(Qt.UserRole) for index in self.selectionModel().selectedIndexes()]
+            if len(selected_items) == 1 and isinstance(selected_items[0], Contact):
+                contact = selected_items[0]
+                self.actions.transfer_call.setEnabled(contact.uri is not None and 'audio' in notification.sender.streams)
+
+    def _NH_BlinkActiveSessionDidChange(self, notification):
+        if self.context_menu.isVisible():
+            selected_items = [index.data(Qt.UserRole) for index in self.selectionModel().selectedIndexes()]
+            if len(selected_items) == 1 and isinstance(selected_items[0], Contact):
+                contact = selected_items[0]
+                active_session = notification.data.active_session
+                self.actions.transfer_call.setEnabled(contact.uri is not None and active_session is not None and active_session.state == 'connected')
+
 
 class ContactDetailView(QListView):
+    implements(IObserver)
+
     def __init__(self, contact_list):
         super(ContactDetailView, self).__init__(contact_list.parent())
         palette = self.palette()
@@ -3778,9 +3870,14 @@ class ContactDetailView(QListView):
         self.actions.send_files = QAction("Send File(s)...", self, triggered=self._AH_SendFiles)
         self.actions.request_screen = QAction("Request Screen", self, triggered=self._AH_RequestScreen)
         self.actions.share_my_screen = QAction("Share My Screen", self, triggered=self._AH_ShareMyScreen)
+        self.actions.transfer_call = QAction("Transfer Active Call", self, triggered=self._AH_TransferCall)
         self.drop_indicator_index = QModelIndex()
         self.doubleClicked.connect(self._SH_DoubleClicked)  # activated is emitted on single click
         contact_list.installEventFilter(self)
+        notification_center = NotificationCenter()
+        notification_center.add_observer(self, 'BlinkSessionDidChangeState')
+        notification_center.add_observer(self, 'BlinkSessionDidRemoveStream')
+        notification_center.add_observer(self, 'BlinkActiveSessionDidChange')
 
     def setModel(self, model):
         old_model = self.model() or Null
@@ -3812,6 +3909,7 @@ class ContactDetailView(QListView):
 
     def contextMenuEvent(self, event):
         account_manager = AccountManager()
+        session_manager = SessionManager()
         model = self.model()
         selected_indexes = self.selectionModel().selectedIndexes()
         selected_item = selected_indexes[0].data(Qt.UserRole) if selected_indexes else None
@@ -3825,6 +3923,7 @@ class ContactDetailView(QListView):
         menu.addAction(self.actions.send_files)
         menu.addAction(self.actions.request_screen)
         menu.addAction(self.actions.share_my_screen)
+        menu.addAction(self.actions.transfer_call)
         menu.addSeparator()
         if isinstance(selected_item, ContactURI) and model.contact_detail.editable:
             menu.addAction(self.actions.make_uri_default)
@@ -3832,6 +3931,7 @@ class ContactDetailView(QListView):
         menu.addAction(self.actions.edit_contact)
         menu.addAction(self.actions.delete_contact)
         can_call = account_manager.default_account is not None and contact_has_uris
+        can_transfer = contact_has_uris and session_manager.active_session is not None and session_manager.active_session.state == 'connected'
         self.actions.start_audio_call.setEnabled(can_call)
         self.actions.start_video_call.setEnabled(can_call)
         self.actions.start_chat_session.setEnabled(can_call)
@@ -3839,6 +3939,7 @@ class ContactDetailView(QListView):
         self.actions.send_files.setEnabled(can_call)
         self.actions.request_screen.setEnabled(can_call)
         self.actions.share_my_screen.setEnabled(can_call)
+        self.actions.transfer_call.setEnabled(can_transfer)
         self.actions.edit_contact.setEnabled(model.contact_detail.editable)
         self.actions.delete_contact.setEnabled(model.contact_detail.deletable)
         menu.exec_(event.globalPos())
@@ -4004,6 +4105,17 @@ class ContactDetailView(QListView):
         session_manager = SessionManager()
         session_manager.create_session(contact, selected_uri, [StreamDescription('screen-sharing', mode='server'), StreamDescription('audio')])
 
+    def _AH_TransferCall(self):
+        contact = self.contact_list.selectionModel().selectedIndexes()[0].data(Qt.UserRole)
+        selected_indexes = self.selectionModel().selectedIndexes()
+        item = selected_indexes[0].data(Qt.UserRole) if selected_indexes else None
+        if isinstance(item, ContactURI):
+            selected_uri = item.uri
+        else:
+            selected_uri = contact.uri
+        session_manager = SessionManager()
+        session_manager.active_session.transfer(selected_uri)
+
     def _DH_ApplicationXBlinkSession(self, event, index, rect, item):
         event.ignore(rect)
 
@@ -4044,6 +4156,29 @@ class ContactDetailView(QListView):
         session_manager = SessionManager()
         session_manager.create_session(contact, selected_uri, contact.preferred_media.stream_descriptions, connect=contact.preferred_media.autoconnect)
 
+    @run_in_gui_thread
+    def handle_notification(self, notification):
+        handler = getattr(self, '_NH_%s' % notification.name, Null)
+        handler(notification)
+
+    def _NH_BlinkSessionDidChangeState(self, notification):
+        session_manager = SessionManager()
+        if notification.sender is session_manager.active_session and self.context_menu.isVisible():
+            contact_has_uris = self.model().rowCount() > 1
+            self.actions.transfer_call.setEnabled(contact_has_uris and notification.sender.state == 'connected')
+
+    def _NH_BlinkSessionDidRemoveStream(self, notification):
+        session_manager = SessionManager()
+        if notification.sender is session_manager.active_session and self.context_menu.isVisible():
+            contact_has_uris = self.model().rowCount() > 1
+            self.actions.transfer_call.setEnabled(contact_has_uris and 'audio' in notification.sender.streams)
+
+    def _NH_BlinkActiveSessionDidChange(self, notification):
+        if self.context_menu.isVisible():
+            contact_has_uris = self.model().rowCount() > 1
+            active_session = notification.data.active_session
+            self.actions.transfer_call.setEnabled(contact_has_uris and active_session is not None and active_session.state == 'connected')
+
 
 # The contact editor dialog
 #

blink/mainwindow.py

@@ -54,6 +54,7 @@ class MainWindow(base_class, ui_class):
         notification_center.add_observer(self, name='SIPAccountGotPendingWatcher')
         notification_center.add_observer(self, name='BlinkSessionNewOutgoing')
         notification_center.add_observer(self, name='BlinkSessionDidReinitializeForOutgoing')
+        notification_center.add_observer(self, name='BlinkSessionTransferNewOutgoing')
         notification_center.add_observer(self, name='BlinkFileTransferNewIncoming')
         notification_center.add_observer(self, name='BlinkFileTransferNewOutgoing')
         notification_center.add_observer(self, sender=AccountManager())
@@ -907,6 +908,10 @@ class MainWindow(base_class, ui_class):
     def _NH_BlinkSessionDidReinitializeForOutgoing(self, notification):
         self.search_box.clear()
 
+    def _NH_BlinkSessionTransferNewOutgoing(self, notification):
+        self.search_box.clear()
+        self.switch_view_button.view = SwitchViewButton.SessionView
+
     def _NH_BlinkFileTransferNewIncoming(self, notification):
         self.filetransfer_window.show(activate=QApplication.activeWindow() is not None)
 

blink/sessions.py

@@ -37,7 +37,7 @@ from sipsimple.configuration.datatypes import Path
 from sipsimple.configuration.settings import SIPSimpleSettings
 from sipsimple.core import SIPCoreError, SIPURI, ToHeader
 from sipsimple.lookup import DNSLookup
-from sipsimple.session import Session
+from sipsimple.session import Session, IllegalStateError
 from sipsimple.streams import MediaStreamRegistry
 from sipsimple.streams.msrp.filetransfer import FileSelector
 from sipsimple.streams.msrp.screensharing import ExternalVNCServerHandler, ExternalVNCViewerHandler, ScreenSharingStream
@@ -470,6 +470,9 @@ class BlinkSession(BlinkSessionBase):
         self.remote_hold = False
         self.recording = False
 
+        self.transfer_state = None
+        self.transfer_direction = None
+
         self.info = SessionInfo()
 
         self._sibling = None
@@ -655,6 +658,43 @@ class BlinkSession(BlinkSessionBase):
             notification_center.post_notification('BlinkSessionNewOutgoing', sender=self)
         notification_center.post_notification('BlinkSessionInfoUpdated', sender=self, data=NotificationData(elements={'session', 'media', 'statistics'}))
 
+    def init_transfer(self, sip_session, streams, contact, contact_uri, reinitialize=False):
+        assert self.state in (None, 'initialized', 'ended')
+        assert self.contact is None or contact.settings is self.contact.settings
+        notification_center = NotificationCenter()
+        if reinitialize:
+            notification_center.post_notification('BlinkSessionWillReinitialize', sender=self)
+            self._initialize(reinitialize=True)
+        else:
+            self._delete_when_done = len(streams) == 1 and streams[0].type == 'audio'
+        self.direction = 'outgoing'
+        self.sip_session = sip_session
+        self.account = sip_session.account
+        self.contact = contact
+        self.contact_uri = contact_uri
+        self.uri = self._normalize_uri(contact_uri.uri)
+        self.stream_descriptions = StreamSet(StreamDescription(stream.type) for stream in streams)
+
+        self.state = 'initialized'
+        if reinitialize:
+            notification_center.post_notification('BlinkSessionDidReinitializeForOutgoing', sender=self)
+        else:
+            notification_center.post_notification('BlinkSessionNewOutgoing', sender=self)
+
+        self.streams.extend(streams)
+
+        self.info._update(self)
+        notification_center.post_notification('BlinkSessionInfoUpdated', sender=self, data=NotificationData(elements={'session', 'media', 'statistics'}))
+
+        self.state = 'connecting/dns_lookup'
+        notification_center.post_notification('BlinkSessionWillConnect', sender=self, data=NotificationData(sibling=None))
+        notification_center.post_notification('BlinkSessionConnectionProgress', sender=self, data=NotificationData(stage='dns_lookup'))
+
+        self.stream_descriptions = None
+
+        self.state = 'connecting'
+        notification_center.post_notification('BlinkSessionConnectionProgress', sender=self, data=NotificationData(stage='connecting'))
+
     def connect(self):
         assert self.direction == 'outgoing' and self.state == 'initialized'
         notification_center = NotificationCenter()
@@ -768,6 +808,15 @@ class BlinkSession(BlinkSessionBase):
             self.recording = False
             audio_stream.stop_recording()
 
+    def transfer(self, contact_uri, replaced_session=None):
+        if self.state != 'connected':
+            return
+        replaced_sip_session = None if replaced_session is None else replaced_session.sip_session
+        try:
+            self.sip_session.transfer(self._parse_uri(contact_uri.uri), replaced_session=replaced_sip_session)
+        except IllegalStateError:
+            pass
+
     def end(self, delete=False):
         if self.state == 'ending':
             self._delete_requested = delete
@@ -981,6 +1030,30 @@ class BlinkSession(BlinkSessionBase):
         elif self.streams.types.isdisjoint({'audio', 'video'}):
             self.unhold()
 
+    def _NH_SIPSessionTransferNewIncoming(self, notification):
+        self.transfer_state = 'active'
+        self.transfer_direction = 'incoming'
+        notification.center.post_notification('BlinkSessionTransferNewIncoming', sender=self, data=notification.data)
+
+    def _NH_SIPSessionTransferNewOutgoing(self, notification):
+        self.transfer_state = 'active'
+        self.transfer_direction = 'outgoing'
+        notification.center.post_notification('BlinkSessionTransferNewOutgoing', sender=self, data=notification.data)
+
+    def _NH_SIPSessionTransferDidStart(self, notification):
+        notification.center.post_notification('BlinkSessionTransferDidStart', sender=self, data=notification.data)
+
+    def _NH_SIPSessionTransferDidEnd(self, notification):
+        self.transfer_state = 'completed'
+        notification.center.post_notification('BlinkSessionTransferDidEnd', sender=self, data=notification.data)
+
+    def _NH_SIPSessionTransferDidFail(self, notification):
+        self.transfer_state = 'failed'
+        notification.center.post_notification('BlinkSessionTransferDidFail', sender=self, data=notification.data)
+
+    def _NH_SIPSessionTransferGotProgress(self, notification):
+        notification.center.post_notification('BlinkSessionTransferGotProgress', sender=self, data=notification.data)
+
     def _NH_MediaStreamDidStart(self, notification):
         stream = notification.sender
         audio_stream = self.streams.get('audio')
@@ -1558,7 +1631,7 @@ class DraggedAudioSessionWidget(base_class, ui_class):
         if self.in_conference:
             self.note_label.setText(u'Drop outside the conference to detach')
         else:
-            self.note_label.setText(u'Drop on a session to conference them')
+            self.note_label.setText(u'<p><b>Drop</b>:&nbsp;Conference&nbsp; <b>Alt+Drop</b>:&nbsp;Transfer</p>')
 
     def paintEvent(self, event):
         painter = QPainter(self)
@@ -1602,6 +1675,9 @@ class AudioSessionItem(object):
         self.blink_session = session
         self.blink_session.items.audio = self
 
+        self.status_context = None
+        self.__saved_status = None  # to store skipped status messages during a context change
+
         self.widget = Null
         self.status = None
         self.type = 'Audio'
@@ -1676,8 +1752,17 @@ class AudioSessionItem(object):
         return self.__dict__['status']
 
     def _set_status(self, value):
-        if self.__dict__.get('status', Null) == value:
+        old_status = self.__dict__.get('status', Null)
+        new_status = value
+        if old_status == new_status:
             return
+        if old_status is not None and old_status is not Null:
+            context = None if new_status is None else new_status.context
+            if self.status_context == old_status.context != context:
+                self.__saved_status = value       # preserve the status that is skipped because of context mismatch
+                return
+            elif old_status.context != context and context is not None:
+                self.__saved_status = old_status  # preserve the status that was there prior to switching the context
         self.__dict__['status'] = value
         self.widget.status_label.value = value
 
@@ -1796,7 +1881,8 @@ class AudioSessionItem(object):
 
     def _reset_status(self, expected_status):
         if self.status == expected_status:
-            self.status = None
+            self.status = self.__saved_status
+        self.__saved_status = None
 
     def _SH_HangupButtonClicked(self):
         self.end()
@@ -1928,6 +2014,26 @@ class AudioSessionItem(object):
                 self.status = Status(notification.data.reason)
             self._cleanup()
 
+    def _NH_BlinkSessionTransferNewOutgoing(self, notification):
+        if self.blink_session.state == 'connected':
+            self.status_context = 'transfer'
+            self.status = Status('Transfer: Trying', context='transfer')
+
+    def _NH_BlinkSessionTransferDidEnd(self, notification):
+        if self.blink_session.transfer_direction == 'outgoing':
+            self.status = Status('Transfer: Succeeded', context='transfer')
+
+    def _NH_BlinkSessionTransferDidFail(self, notification):
+        if self.blink_session.state == 'connected' and self.blink_session.transfer_direction == 'outgoing':
+            reason = 'Decline' if notification.data.code == 603 else notification.data.reason
+            self.status = Status("Transfer: {}".format(reason), context='transfer')
+            call_later(3, self._reset_status, self.status)
+        self.status_context = None
+
+    def _NH_BlinkSessionTransferGotProgress(self, notification):
+        if self.blink_session.state == 'connected' and notification.data.code < 200:  # final answers are handled in DidEnd and DiDFail
+            self.status = Status("Transfer: {}".format(notification.data.reason), context='transfer')
+
     def _NH_MediaStreamWillEnd(self, notification):
         stream = notification.sender
         if stream.type == 'audio' and stream.blink_session.items.audio is self:
@@ -2022,7 +2128,7 @@ class AudioSessionModel(QAbstractListModel):
         return None
 
     def supportedDropActions(self):
-        return Qt.CopyAction | Qt.MoveAction
+        return Qt.CopyAction | Qt.MoveAction | Qt.LinkAction
 
     def mimeTypes(self):
         return ['application/x-blink-session-list']
@@ -2057,7 +2163,10 @@ class AudioSessionModel(QAbstractListModel):
         selection_model = session_list.selectionModel()
         source = session_list.dragged_session
         target = self.sessions[index.row()] if index.isValid() else None
-        if source.client_conference is None:  # the dragged session is not in a conference yet
+
+        if action == Qt.LinkAction:  # call transfer
+            source.blink_session.transfer(target.blink_session.contact_uri, replaced_session=target.blink_session)
+        elif source.client_conference is None:  # the dragged session is not in a conference yet
             if target.client_conference is not None:
                 source_row = self.sessions.index(source)
                 target_row = self.sessions.index(target.client_conference.sessions[-1].items.audio) + 1
@@ -2088,6 +2197,7 @@ class AudioSessionModel(QAbstractListModel):
                 session.active = source.active or target.active
             if source.active:
                 source.client_conference.unhold()
+            self.structureChanged.emit()
         else:  # the dragged session is in a conference
             dragged = source
             sibling = next(session.items.audio for session in dragged.client_conference.sessions if session.items.audio is not dragged)
@@ -2127,7 +2237,7 @@ class AudioSessionModel(QAbstractListModel):
                 session_list.scrollTo(self.index(self.sessions.index(sibling)), session_list.PositionAtCenter)
             dragged.widget.selected = False
             dragged.active = False
-        self.structureChanged.emit()
+            self.structureChanged.emit()
         return True
 
     def _DH_ApplicationXBlinkContactList(self, mime_data, action, index):
@@ -2515,10 +2625,8 @@ class AudioSessionListView(QListView):
         if not acceptable_mime_types:
             event.ignore()
         elif event_source is not self and 'application/x-blink-session-list' in provided_mime_types:
-            event.ignore() # we don't handle drops for blink sessions from other sources
+            event.ignore()  # we don't handle drops for blink sessions from other sources
         else:
-            if event_source is self:
-                event.setDropAction(Qt.MoveAction)
             event.accept()
 
     def dragLeaveEvent(self, event):
@@ -2528,8 +2636,6 @@ class AudioSessionListView(QListView):
 
     def dragMoveEvent(self, event):
         super(AudioSessionListView, self).dragMoveEvent(event)
-        if event.source() is self:
-            event.setDropAction(Qt.MoveAction)
 
         model = self.model()
 
@@ -2551,7 +2657,10 @@ class AudioSessionListView(QListView):
     def dropEvent(self, event):
         model = self.model()
         if event.source() is self:
-            event.setDropAction(Qt.MoveAction)
+            if event.keyboardModifiers() & Qt.AltModifier:
+                event.setDropAction(Qt.LinkAction)
+            else:
+                event.setDropAction(Qt.MoveAction)
         for session in self.model().sessions:
             session.widget.drop_indicator = False
         if model.handleDroppedData(event.mimeData(), event.dropAction(), self.indexAt(event.pos())):
@@ -2565,9 +2674,19 @@ class AudioSessionListView(QListView):
             rect = self.viewport().rect()
             rect.setTop(self.visualRect(model.index(len(model.sessions)-1)).bottom())
             if dragged_session.client_conference is not None:
+                event.setDropAction(Qt.MoveAction)
                 event.accept(rect)
             else:
                 event.ignore(rect)
+        elif event.keyboardModifiers() & Qt.AltModifier and dragged_session.client_conference is None:
+            if dragged_session is session or session.client_conference is not None or session.blink_session.state != 'connected':
+                event.ignore(rect)
+            elif dragged_session.blink_session.transfer_state in ('active', 'completed') or session.blink_session.transfer_state in ('active', 'completed'):
+                event.ignore(rect)
+            else:
+                session.widget.drop_indicator = True
+                event.setDropAction(Qt.LinkAction)  # it might not be LinkAction if other keyboard modifiers are active
+                event.accept(rect)
         else:
             conference = dragged_session.client_conference or Null
             if dragged_session is session or session.blink_session in conference.sessions:
@@ -2579,6 +2698,7 @@ class AudioSessionListView(QListView):
                             sibling.items.audio.widget.drop_indicator = True
                     else:
                         session.widget.drop_indicator = True
+                event.setDropAction(Qt.MoveAction)
                 event.accept(rect)
 
     def _DH_ApplicationXBlinkContactList(self, event, index, rect, session):
@@ -5091,6 +5211,88 @@ class IncomingFileTransferRequest(QObject):
         self.rejected.emit(self, self.dialog.reject_mode)
 
 
+ui_class, base_class = uic.loadUiType(Resources.get('incoming_calltransfer_dialog.ui'))
+
+class IncomingCallTransferDialog(IncomingDialogBase, ui_class):
+    def __init__(self, parent=None):
+        super(IncomingCallTransferDialog, self).__init__(parent)
+        self.setWindowFlags(Qt.WindowStaysOnTopHint)
+        self.setAttribute(Qt.WA_DeleteOnClose)
+        with Resources.directory:
+            self.setupUi(self)
+        font = self.username_label.font()
+        font.setPointSizeF(self.uri_label.fontInfo().pointSizeF() + 3)
+        font.setFamily("Sans Serif")
+        self.username_label.setFont(font)
+        font = self.transfer_label.font()
+        font.setPointSizeF(self.uri_label.fontInfo().pointSizeF() - 1)
+        self.transfer_label.setFont(font)
+        self.slot = None
+        self.reject_mode = 'reject'
+
+    def show(self, activate=True):
+        self.setAttribute(Qt.WA_ShowWithoutActivating, not activate)
+        super(IncomingCallTransferDialog, self).show()
+
+del ui_class, base_class
+
+
+class IncomingCallTransferRequest(QObject):
+    finished = pyqtSignal(object)
+    accepted = pyqtSignal(object)
+    rejected = pyqtSignal(object, str)
+
+    priority = 0
+    stream_types = {'audio'}
+
+    def __init__(self, dialog, contact, contact_uri, session):
+        super(IncomingCallTransferRequest, self).__init__()
+        self.dialog = dialog
+        self.contact = contact
+        self.contact_uri = contact_uri
+        self.session = session
+
+        self.dialog.setWindowTitle(u'Incoming Call Transfer')
+        self.dialog.setWindowIconText(u'Incoming Call Transfer')
+
+        self.dialog.uri_label.setText(contact_uri.uri)
+        self.dialog.username_label.setText(contact.name)
+        if contact.pixmap:
+            self.dialog.user_icon.setPixmap(contact.pixmap)
+        self.dialog.transfer_label.setText(u'would like to transfer you to {.uri}'.format(contact_uri))
+
+        self.dialog.finished.connect(self._SH_DialogFinished)
+        self.dialog.accepted.connect(self._SH_DialogAccepted)
+        self.dialog.rejected.connect(self._SH_DialogRejected)
+
+    def __eq__(self, other):
+        return self is other
+
+    def __ne__(self, other):
+        return self is not other
+
+    def __lt__(self, other):
+        return self.priority < other.priority
+
+    def __le__(self, other):
+        return self.priority <= other.priority
+
+    def __gt__(self, other):
+        return self.priority > other.priority
+
+    def __ge__(self, other):
+        return self.priority >= other.priority
+
+    def _SH_DialogFinished(self):
+        self.finished.emit(self)
+
+    def _SH_DialogAccepted(self):
+        self.accepted.emit(self)
+
+    def _SH_DialogRejected(self):
+        self.rejected.emit(self, self.dialog.reject_mode)
+
+
 ui_class, base_class = uic.loadUiType(Resources.get('conference_dialog.ui'))
 
 class ConferenceDialog(base_class, ui_class):
@@ -5210,6 +5412,7 @@ class SessionManager(object):
         self._filetransfer_tone_timer.setSingleShot(True)
 
         notification_center = NotificationCenter()
+        notification_center.add_observer(self, name='SIPSessionNewOutgoing')
         notification_center.add_observer(self, name='SIPSessionNewIncoming')
         notification_center.add_observer(self, name='SIPSessionDidFail')
 
@@ -5395,6 +5598,18 @@ class SessionManager(object):
         if mode == 'reject':
             incoming_request.session.reject(603)
 
+    def _SH_IncomingCallTransferRequestAccepted(self, incoming_request):
+        try:
+            incoming_request.session.accept_transfer()
+        except IllegalStateError:
+            pass
+
+    def _SH_IncomingCallTransferRequestRejected(self, incoming_request, mode):
+        try:
+            incoming_request.session.reject_transfer()
+        except IllegalStateError:
+            pass
+
     @run_in_gui_thread
     def handle_notification(self, notification):
         handler = getattr(self, '_NH_%s' % notification.name, Null)
@@ -5457,6 +5672,20 @@ class SessionManager(object):
         incoming_request.dialog.show(activate=QApplication.activeWindow() is not None and self.incoming_requests.index(incoming_request) == 0)
         self.update_ringtone()
 
+    def _NH_SIPSessionNewOutgoing(self, notification):
+        sip_session = notification.sender
+        if sip_session.transfer_info is not None:
+            from blink.contacts import URIUtils
+
+            contact, contact_uri = URIUtils.find_contact(sip_session.remote_identity.uri)
+            try:
+                blink_session = next(session for session in self.sessions if session.reusable and session.contact.settings is contact.settings)
+                reinitialize = True
+            except StopIteration:
+                blink_session = BlinkSession()
+                reinitialize = False
+            blink_session.init_transfer(sip_session, notification.data.streams, contact, contact_uri, reinitialize=reinitialize)
+
     def _NH_SIPSessionDidFail(self, notification):
         if notification.sender.direction == 'incoming':
             for incoming_request in self.incoming_requests[notification.sender]:
@@ -5510,6 +5739,28 @@ class SessionManager(object):
         self.sessions.remove(notification.sender)
         notification.center.remove_observer(self, sender=notification.sender)
 
+    def _NH_BlinkSessionTransferNewIncoming(self, notification):
+        from blink.contacts import URIUtils
+
+        session = notification.sender.sip_session
+        contact, contact_uri = URIUtils.find_contact(notification.data.transfer_destination)
+
+        dialog = IncomingCallTransferDialog()  # Build the dialog without a parent in order to be displayed on the current workspace on Linux.
+        incoming_request = IncomingCallTransferRequest(dialog, contact, contact_uri, session)
+        incoming_request.finished.connect(self._SH_IncomingRequestFinished)
+        incoming_request.accepted.connect(self._SH_IncomingCallTransferRequestAccepted)
+        incoming_request.rejected.connect(self._SH_IncomingCallTransferRequestRejected)
+
+        bisect.insort_right(self.incoming_requests, incoming_request)
+        incoming_request.dialog.show(activate=QApplication.activeWindow() is not None and self.incoming_requests.index(incoming_request) == 0)
+        self.update_ringtone()
+
+    def _NH_BlinkSessionTransferDidFail(self, notification):
+        for request in self.incoming_requests[notification.sender.sip_session, IncomingCallTransferRequest]:
+            request.dialog.hide()
+            self.incoming_requests.remove(request)
+        self.update_ringtone()
+
     def _NH_BlinkFileTransferWasCreated(self, notification):
         self.file_transfers.append(notification.sender)
         notification.center.add_observer(self, sender=notification.sender)

resources/incoming_calltransfer_dialog.ui

+<?xml version="1.0" encoding="UTF-8"?>
+<ui version="4.0">
+ <class>Dialog</class>
+ <widget class="QDialog" name="Dialog">
+  <property name="geometry">
+   <rect>
+    <x>0</x>
+    <y>0</y>
+    <width>480</width>
+    <height>165</height>
+   </rect>
+  </property>
+  <property name="minimumSize">
+   <size>
+    <width>480</width>
+    <height>165</height>
+   </size>
+  </property>
+  <property name="maximumSize">
+   <size>
+    <width>16777215</width>
+    <height>165</height>
+   </size>
+  </property>
+  <property name="windowTitle">
+   <string>Incoming Call Transfer</string>
+  </property>
+  <property name="windowIcon">
+   <iconset>
+    <normaloff>icons/blink48.png</normaloff>icons/blink48.png</iconset>
+  </property>
+  <layout class="QVBoxLayout" name="dialog_layout">
+   <property name="spacing">
+    <number>34</number>
+   </property>
+   <property name="margin">
+    <number>8</number>
+   </property>
+   <item>
+    <widget class="QFrame" name="frame">
+     <property name="styleSheet">
+      <string>QFrame#frame {
+	background-color: #f8f8f8;
+	border-color: #545454;
+	border-radius: 4px;
+	border-width: 2px;
+	border-style: solid;
+}
+
+
+</string>
+     </property>
+     <property name="frameShape">
+      <enum>QFrame::StyledPanel</enum>
+     </property>
+     <property name="frameShadow">
+      <enum>QFrame::Sunken</enum>
+     </property>
+     <layout class="QGridLayout" name="frame_layout">
+      <property name="topMargin">
+       <number>7</number>
+      </property>
+      <property name="bottomMargin">
+       <number>7</number>
+      </property>
+      <property name="verticalSpacing">
+       <number>0</number>
+      </property>
+      <item row="0" column="1">
+       <widget class="QLabel" name="username_label">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="font">
+         <font>
+          <family>Sans Serif</family>
+          <pointsize>12</pointsize>
+          <weight>75</weight>
+          <bold>true</bold>
+         </font>
+        </property>
+        <property name="text">
+         <string>Caller name</string>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignLeading|Qt::AlignLeft|Qt::AlignVCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item row="1" column="1">
+       <widget class="QLabel" name="uri_label">
+        <property name="sizePolicy">
+         <sizepolicy hsizetype="Expanding" vsizetype="Fixed">
+          <horstretch>0</horstretch>
+          <verstretch>0</verstretch>
+         </sizepolicy>
+        </property>
+        <property name="palette">
+         <palette>
+          <active>
+           <colorrole role="WindowText">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>68</red>
+              <green>68</green>
+              <blue>68</blue>
+             </color>
+            </brush>
+           </colorrole>
+           <colorrole role="Text">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>68</red>
+              <green>68</green>
+              <blue>68</blue>
+             </color>
+            </brush>
+           </colorrole>
+          </active>
+          <inactive>
+           <colorrole role="WindowText">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>68</red>
+              <green>68</green>
+              <blue>68</blue>
+             </color>
+            </brush>
+           </colorrole>
+           <colorrole role="Text">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>68</red>
+              <green>68</green>
+              <blue>68</blue>
+             </color>
+            </brush>
+           </colorrole>
+          </inactive>
+          <disabled>
+           <colorrole role="WindowText">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>118</red>
+              <green>118</green>
+              <blue>117</blue>
+             </color>
+            </brush>
+           </colorrole>
+           <colorrole role="Text">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>118</red>
+              <green>118</green>
+              <blue>117</blue>
+             </color>
+            </brush>
+           </colorrole>
+          </disabled>
+         </palette>
+        </property>
+        <property name="text">
+         <string>Caller URI</string>
+        </property>
+        <property name="indent">
+         <number>1</number>
+        </property>
+       </widget>
+      </item>
+      <item row="0" column="0" rowspan="2">
+       <widget class="QLabel" name="user_icon">
+        <property name="minimumSize">
+         <size>
+          <width>36</width>
+          <height>36</height>
+         </size>
+        </property>
+        <property name="maximumSize">
+         <size>
+          <width>36</width>
+          <height>36</height>
+         </size>
+        </property>
+        <property name="pixmap">
+         <pixmap>icons/default-avatar.png</pixmap>
+        </property>
+        <property name="alignment">
+         <set>Qt::AlignCenter</set>
+        </property>
+       </widget>
+      </item>
+      <item row="2" column="0" colspan="2">
+       <spacer name="frame_spacer">
+        <property name="orientation">
+         <enum>Qt::Vertical</enum>
+        </property>
+        <property name="sizeHint" stdset="0">
+         <size>
+          <width>0</width>
+          <height>0</height>
+         </size>
+        </property>
+       </spacer>
+      </item>
+      <item row="3" column="0" colspan="2">
+       <widget class="QLabel" name="transfer_label">
+        <property name="palette">
+         <palette>
+          <active>
+           <colorrole role="WindowText">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>68</red>
+              <green>68</green>
+              <blue>68</blue>
+             </color>
+            </brush>
+           </colorrole>
+           <colorrole role="Text">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>68</red>
+              <green>68</green>
+              <blue>68</blue>
+             </color>
+            </brush>
+           </colorrole>
+          </active>
+          <inactive>
+           <colorrole role="WindowText">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>68</red>
+              <green>68</green>
+              <blue>68</blue>
+             </color>
+            </brush>
+           </colorrole>
+           <colorrole role="Text">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>68</red>
+              <green>68</green>
+              <blue>68</blue>
+             </color>
+            </brush>
+           </colorrole>
+          </inactive>
+          <disabled>
+           <colorrole role="WindowText">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>118</red>
+              <green>118</green>
+              <blue>117</blue>
+             </color>
+            </brush>
+           </colorrole>
+           <colorrole role="Text">
+            <brush brushstyle="SolidPattern">
+             <color alpha="255">
+              <red>118</red>
+              <green>118</green>
+              <blue>117</blue>
+             </color>
+            </brush>
+           </colorrole>
+          </disabled>
+         </palette>
+        </property>
+        <property name="text">
+         <string extracomment="is offering to share his screen">would like to transfer you to user@domain</string>
+        </property>
+        <property name="indent">
+         <number>3</number>
+        </property>
+       </widget>
+      </item>
+     </layout>
+    </widget>
+   </item>
+   <item>
+    <layout class="QHBoxLayout" name="button_layout">
+     <property name="spacing">
+      <number>5</number>
+     </property>
+     <item>
+      <widget class="QPushButton" name="reject_button">
+       <property name="minimumSize">
+        <size>
+         <width>85</width>
+         <height>24</height>
+        </size>
+       </property>
+       <property name="maximumSize">
+        <size>
+         <width>16777215</width>
+         <height>24</height>
+        </size>
+       </property>
+       <property name="text">
+        <string>Reject</string>
+       </property>
+      </widget>
+     </item>
+     <item>
+      <spacer name="button_spacer">
+       <property name="orientation">
+        <enum>Qt::Horizontal</enum>
+       </property>
+       <property name="sizeHint" stdset="0">
+        <size>
+         <width>40</width>
+         <height>20</height>
+        </size>
+       </property>
+      </spacer>
+     </item>
+     <item>
+      <widget class="QPushButton" name="accept_button">
+       <property name="minimumSize">
+        <size>
+         <width>85</width>
+         <height>24</height>
+        </size>
+       </property>
+       <property name="maximumSize">
+        <size>
+         <width>16777215</width>
+         <height>24</height>
+        </size>
+       </property>
+       <property name="text">
+        <string>Accept</string>
+       </property>
+       <property name="default">
+        <bool>true</bool>
+       </property>
+      </widget>
+     </item>
+    </layout>
+   </item>
+  </layout>
+ </widget>
+ <tabstops>
+  <tabstop>accept_button</tabstop>
+  <tabstop>reject_button</tabstop>
+ </tabstops>
+ <resources/>
+ <connections>
+  <connection>
+   <sender>accept_button</sender>
+   <signal>clicked()</signal>
+   <receiver>Dialog</receiver>
+   <slot>accept()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>345</x>
+     <y>117</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>196</x>
+     <y>67</y>
+    </hint>
+   </hints>
+  </connection>
+  <connection>
+   <sender>reject_button</sender>
+   <signal>clicked()</signal>
+   <receiver>Dialog</receiver>
+   <slot>reject()</slot>
+   <hints>
+    <hint type="sourcelabel">
+     <x>48</x>
+     <y>117</y>
+    </hint>
+    <hint type="destinationlabel">
+     <x>196</x>
+     <y>67</y>
+    </hint>
+   </hints>
+  </connection>
+ </connections>
+</ui>