Qt: display number of tasks (window._coroutines_scheduled) in toolbar.

Disable rebalance/swap suggestions attached to requests/invoices if there is an ongoing task.
Note: This assumes that all tasks are lightning payments, which is true for the moment.

electrum/gui/qt/main_window.py

@@ -343,9 +343,11 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
                     on_result(res)
             finally:
                 self._coroutines_scheduled.discard(fut)
+                self.need_update.set()
 
         fut = asyncio.run_coroutine_threadsafe(wrapper(), self.network.asyncio_loop)
         self._coroutines_scheduled.add(fut)
+        self.need_update.set()
 
     def on_fx_history(self):
         self.history_model.refresh('fx_history')
@@ -1028,6 +1030,15 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         if self.status_button:
             self.status_button.setIcon(icon)
 
+        num_tasks = self.num_tasks()
+        self.tasks_label.setText("(%d %s)"%(num_tasks, _("tasks")))
+        self.tasks_label.setVisible(num_tasks > 0)
+
+    def num_tasks(self):
+        # For the moment, all the coroutines in this set are outgoing LN payments,
+        # so we can use this to disable buttons for rebalance/swap suggestions
+        return len(self._coroutines_scheduled)
+
     def update_wallet(self):
         self.update_status()
         if self.wallet.is_up_to_date() or not self.network or not self.network.is_connected():
@@ -1330,22 +1341,22 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         elif not can_receive_lightning:
             self.receive_rebalance_button.suggestion = self.wallet.lnworker.suggest_rebalance_to_receive(amount_sat)
             self.receive_swap_button.suggestion = self.wallet.lnworker.suggest_swap_to_receive(amount_sat)
-            ln_help = _('Your Lightning channels do not have the capacity to receive this amount.')
             can_rebalance = bool(self.receive_rebalance_button.suggestion)
             can_swap = bool(self.receive_swap_button.suggestion)
+            lnaddr = ''
+            ln_help = _('You do not have the capacity to receive that amount with Lightning.')
             if can_rebalance:
-                ln_help += '\n\n' + _('You may have that capacity after rebalancing your channels.')
+                ln_help += '\n\n' + _('You may have that capacity if you rebalance your channels.')
             elif can_swap:
-                ln_help += '\n\n' + _('You may have that capacity after swapping some of your funds.')
-            lnaddr = ''
+                ln_help += '\n\n' + _('You may have that capacity if you swap some of your funds.')
         else:
             ln_help = ''
             can_rebalance = False
             can_swap = False
-        self.receive_rebalance_button.setEnabled(can_rebalance)
         self.receive_rebalance_button.setVisible(can_rebalance)
-        self.receive_swap_button.setEnabled(can_swap)
         self.receive_swap_button.setVisible(can_swap)
+        self.receive_rebalance_button.setEnabled(can_rebalance and self.num_tasks() == 0)
+        self.receive_swap_button.setEnabled(can_swap and self.num_tasks() == 0)
         icon_name = "lightning.png" if lnaddr else "lightning_disconnected.png"
         self.receive_tabs.setTabIcon(2, read_QIcon(icon_name))
         # encode lightning invoices as uppercase so QR encoding can use
@@ -1747,7 +1758,8 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
             can_pay_onchain = invoice.get_address() and self.wallet.can_pay_onchain(invoice.get_outputs(), coins=coins)
             can_pay_with_new_channel = self.wallet.lnworker.suggest_funding_amount(amount_sat, coins=coins)
             can_pay_with_swap = self.wallet.lnworker.suggest_swap_to_send(amount_sat, coins=coins)
-            can_rebalance = self.wallet.lnworker.suggest_rebalance_to_send(amount_sat)
+            rebalance_suggestion = self.wallet.lnworker.suggest_rebalance_to_send(amount_sat)
+            can_rebalance = bool(rebalance_suggestion) and self.num_tasks() == 0
             choices = {}
             if can_rebalance:
                 msg = ''.join([
@@ -1782,7 +1794,7 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
             if r is not None:
                 self.save_pending_invoice()
                 if r == 0:
-                    chan1, chan2, delta = can_rebalance
+                    chan1, chan2, delta = rebalance_suggestion
                     self.rebalance_dialog(chan1, chan2, amount_sat=delta)
                 elif r == 1:
                     amount_sat, min_amount_sat = can_pay_with_new_channel
@@ -2540,6 +2552,9 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         self.update_check_button.hide()
         sb.addPermanentWidget(self.update_check_button)
 
+        self.tasks_label = QLabel('')
+        sb.addPermanentWidget(self.tasks_label)
+
         self.password_button = StatusBarButton(QIcon(), _("Password"), self.change_password_dialog)
         sb.addPermanentWidget(self.password_button)
 
@@ -3754,3 +3769,4 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         amount_msat = amount_e.get_amount() * 1000
         coro = self.wallet.lnworker.rebalance_channels(d.chan_from, d.chan_to, amount_msat=amount_msat)
         self.run_coroutine_from_thread(coro)
+        self.update_current_request()