add CPFP (child pays for parent) dialog to the Qt GUI

gui/qt/history_list.py

@@ -142,7 +142,7 @@ class HistoryList(MyTreeWidget):
         height, conf, timestamp = self.wallet.get_tx_height(tx_hash)
         tx = self.wallet.transactions.get(tx_hash)
         is_relevant, is_mine, v, fee = self.wallet.get_wallet_delta(tx)
-        rbf = is_mine and height <=0 and tx and not tx.is_final()
+        is_unconfirmed = height <= 0
         menu = QMenu()
 
         menu.addAction(_("Copy %s")%column_title, lambda: self.parent.app.clipboard().setText(column_data))
@@ -150,8 +150,14 @@ class HistoryList(MyTreeWidget):
             menu.addAction(_("Edit %s")%column_title, lambda: self.editItem(item, column))
 
         menu.addAction(_("Details"), lambda: self.parent.show_transaction(tx))
-        if rbf:
+        if is_unconfirmed and tx:
-            menu.addAction(_("Increase fee"), lambda: self.parent.bump_fee_dialog(tx))
+            rbf = is_mine and not tx.is_final()
+            if rbf:
+                menu.addAction(_("Increase fee"), lambda: self.parent.bump_fee_dialog(tx))
+            else:
+                child_tx = self.wallet.cpfp(tx, 0)
+                if child_tx:
+                    menu.addAction(_("Child pays for parent"), lambda: self.parent.cpfp(tx, child_tx))
         if tx_URL:
             menu.addAction(_("View on block explorer"), lambda: webbrowser.open(tx_URL))
         menu.exec_(self.viewport().mapToGlobal(position))

gui/qt/main_window.py

@@ -2767,6 +2767,33 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, PrintError):
         vbox.addLayout(Buttons(CloseButton(d)))
         d.exec_()
 
+    def cpfp(self, parent_tx, new_tx):
+        total_size = parent_tx.estimated_size() + new_tx.estimated_size()
+        d = WindowModalDialog(self, _('Child Pays for Parent'))
+        vbox = QVBoxLayout(d)
+        vbox.addWidget(QLabel(_('Total size') + ': %d bytes'% total_size))
+        max_fee = new_tx.output_value()
+        vbox.addWidget(QLabel(_('Max fee') + ': %s'% self.format_amount(max_fee) + ' ' + self.base_unit()))
+        vbox.addWidget(QLabel(_('Child fee' + ':')))
+        fee_e = BTCAmountEdit(self.get_decimal_point)
+        fee = self.config.fee_per_kb() * total_size / 1000
+        fee_e.setAmount(fee)
+        vbox.addWidget(fee_e)
+        def on_rate(dyn, pos, fee_rate):
+            fee = fee_rate * total_size / 1000
+            fee_e.setAmount(min(max_fee, fee))
+        fee_slider = FeeSlider(self, self.config, on_rate)
+        vbox.addWidget(fee_slider)
+        vbox.addLayout(Buttons(CancelButton(d), OkButton(d)))
+        if not d.exec_():
+            return
+        fee = fee_e.get_amount()
+        if fee > max_fee:
+            self.show_error(_('Max fee exceeded'))
+            return
+        new_tx = self.wallet.cpfp(parent_tx, fee)
+        new_tx.set_sequence(0)
+        self.show_transaction(new_tx)
 
     def bump_fee_dialog(self, tx):
         is_relevant, is_mine, v, fee = self.wallet.get_wallet_delta(tx)

lib/wallet.py

@@ -1042,6 +1042,25 @@ class Abstract_Wallet(PrintError):
             raise BaseException(_('Cannot bump fee: cound not find suitable outputs'))
         return Transaction.from_io(inputs, outputs)
 
+    def cpfp(self, tx, fee):
+        txid = tx.txid()
+        for i, o in enumerate(tx.outputs()):
+            otype, address, value = o
+            if otype == TYPE_ADDRESS and self.is_mine(address):
+                break
+        else:
+            return
+        coins = self.get_addr_utxo(address)
+        for item in coins:
+            if item['prevout_hash'] == txid and item['prevout_n'] == i:
+                break
+        else:
+            return
+        self.add_input_info(item)
+        inputs = [item]
+        outputs = [(TYPE_ADDRESS, address, value - fee)]
+        return Transaction.from_io(inputs, outputs)
+
     def add_input_info(self, txin):
         # Add address for utxo that are in wallet
         if txin.get('scriptSig') == '':