Qt: add info about force closing

electrum/gui/qt/channels_list.py

@@ -98,10 +98,16 @@ class ChannelsList(MyTreeView):
         WaitingDialog(self, 'please wait..', task, self.on_success, self.on_failure)
 
     def force_close(self, channel_id):
+        chan = self.lnworker.channels[channel_id]
+        to_self_delay = chan.config[REMOTE].to_self_delay
         if self.lnworker.wallet.is_lightning_backup():
             msg = _('WARNING: force-closing from an old state might result in fund loss.\nAre you sure?')
         else:
-            msg = _('Force-close channel?\nReclaimed funds will not be immediately available.')
+            msg = _('Force-close channel?') + '\n\n'\
+                  + _(f'Funds retrieved from this channel will not be available before {to_self_delay} blocks after forced closure.') + ' '\
+                  + _('After that delay, funds will be sent to an address derived from your wallet seed.') + '\n\n'\
+                  + _('In the meantime, channel funds will not be recoverable from your seed, and will be lost if you lose your wallet.') + ' '\
+                  + _('To avoid that, you should backup your wallet after you force close the channel.')
         if self.parent.question(msg):
             def task():
                 coro = self.lnworker.force_close_channel(channel_id)