show capacity of channel backups in GUI

electrum/gui/kivy/uix/dialogs/lightning_channels.py

@@ -461,7 +461,7 @@ class ChannelDetailsPopup(Popup, Logger):
         self.channel_id = bh2u(chan.channel_id)
         self.funding_txid = chan.funding_outpoint.txid
         self.short_id = format_short_channel_id(chan.short_channel_id)
-        self.capacity = self.app.format_amount_and_units(chan.constraints.capacity)
+        self.capacity = self.app.format_amount_and_units(chan.get_capacity())
         self.state = chan.get_state_for_GUI()
         self.local_ctn = chan.get_latest_ctn(LOCAL)
         self.remote_ctn = chan.get_latest_ctn(REMOTE)

electrum/gui/qt/channel_details.py

@@ -169,7 +169,7 @@ class ChannelDetailsDialog(QtWidgets.QDialog):
         form_layout.addRow(_('State:'), SelectableLabel(chan.get_state_for_GUI()))
         self.initiator = 'Local' if chan.constraints.is_initiator else 'Remote'
         form_layout.addRow(_('Initiator:'), SelectableLabel(self.initiator))
-        self.capacity = self.window.format_amount_and_units(chan.constraints.capacity)
+        self.capacity = self.window.format_amount_and_units(chan.get_capacity())
         form_layout.addRow(_('Capacity:'), SelectableLabel(self.capacity))
         self.can_send_label = SelectableLabel()
         self.can_receive_label = SelectableLabel()

electrum/gui/qt/channels_list.py

@@ -85,10 +85,7 @@ class ChannelsList(MyTreeView):
         status = chan.get_state_for_GUI()
         closed = chan.is_closed()
         node_alias = self.lnworker.get_node_alias(chan.node_id) or chan.node_id.hex()
-        if isinstance(chan, Channel):
-            capacity_str = self.parent.format_amount(chan.constraints.capacity, whitespaces=True)
-        else:
-            capacity_str = ''
+        capacity_str = self.parent.format_amount(chan.get_capacity(), whitespaces=True)
         return {
             self.Columns.SHORT_CHANID: chan.short_id_for_GUI(),
             self.Columns.NODE_ALIAS: node_alias,

electrum/lnchannel.py

@@ -446,6 +446,9 @@ class ChannelBackup(AbstractChannel):
         self.lnworker = lnworker
         self.short_channel_id = None
 
+    def get_capacity(self):
+        return self.lnworker.lnwatcher.get_tx_delta(self.funding_outpoint.txid, self.cb.funding_address)
+
     def is_backup(self):
         return True
 
@@ -538,6 +541,9 @@ class Channel(AbstractChannel):
         self._receive_fail_reasons = {}  # type: Dict[int, (bytes, OnionRoutingFailure)]
         self._ignore_max_htlc_value = False  # used in tests
 
+    def get_capacity(self):
+        return self.constraints.capacity
+
     def is_initiator(self):
         return self.constraints.is_initiator