add option to show warnings on wallet close, add warning for ongoing submarine swap

Author: f321x

electrum/gui/messages.py

@@ -61,11 +61,15 @@ def to_rtf(msg):
     _("Please remain online until the funding transaction is confirmed.") + "\n\n" +
     _('The swap will be finalized once your transaction is confirmed.') + " " +
     _("After the funding transaction is mined, the server will reveal the preimage needed to "
-      "fulfill the pending received lightning HTLCs. The HTLCs expire in {} blocks. "
+      "fulfill the pending received lightning HTLCs.")
+)
+
+MSG_FORWARD_SWAP_HTLC_EXPIRY = _(
+      "The HTLCs expire in {} blocks. "
       "You will need to be online after the funding transaction is confirmed but before the HTLCs expire, "
       "to claim your money. If you go offline for several days while the swap is pending, "
       "you risk losing the swap amount!").format(MIN_FINAL_CLTV_DELTA_FOR_CLIENT)
-)
+
 
 MSG_REVERSE_SWAP_FUNDING_MEMPOOL = (
     _('The funding transaction has been detected.') + " " +

electrum/gui/qt/__init__.py

@@ -27,7 +27,7 @@
 import signal
 import sys
 import threading
-from typing import Optional, TYPE_CHECKING, List, Sequence
+from typing import Optional, TYPE_CHECKING, List, Sequence, Callable
 
 try:
     import PyQt6

electrum/gui/qt/main_window.py

@@ -2619,8 +2619,46 @@ def settings_dialog(self):
         if d.need_restart:
             self.show_warning(_('Please restart Electrum to activate the new GUI settings'), title=_('Success'))
 
+    def _show_closing_warnings(self) -> bool:
+        """Show any closing warnings and return True if the user chose to quit anyways."""
+        for callback in self.wallet.closing_warning_callbacks:
+            try:
+                warning: Optional[str] = callback()
+            except Exception:
+                self.logger.exception("Closing warning callback failed: ")
+                continue
+            if warning:
+                # build custom QMessageBox to change button strings and color
+                box = QMessageBox()
+                box.setWindowTitle(_("Don't close Electrum yet!"))
+                box.setText(_("An ongoing operation may get interrupted!"))
+                box.setInformativeText(str(warning))
+                box.setMaximumWidth(400)
+                box.setIcon(QMessageBox.Icon.Warning)
+                box.setStyleSheet("QMessageBox { border: 3px solid #d9534f; }")
+
+                # Add custom buttons
+                cancel_button = box.addButton(_("Cancel"), QMessageBox.ButtonRole.RejectRole)
+                box.setDefaultButton(cancel_button)
+                close_anyway_button = box.addButton(_("Close anyways"), QMessageBox.ButtonRole.AcceptRole)
+                close_anyway_button.setStyleSheet("background-color: #d9534f;")
+
+                if text_label := box.findChild(QLabel):
+                    text_label.setWordWrap(True)
+
+                box.exec()
+                if box.clickedButton() == cancel_button:
+                    break
+        else:
+            # user chose to cancel all warnings or there were no warnings
+            return True
+        return False
+
     def closeEvent(self, event):
         # note that closeEvent is NOT called if the user quits with Ctrl-C
+        if not self._show_closing_warnings():
+            event.ignore()
+            return
         self.clean_up()
         event.accept()
 
@@ -2809,7 +2847,16 @@ def on_swap_result(self, txid: Optional[str], *, is_reverse: bool):
             if is_reverse:
                 msg += messages.MSG_REVERSE_SWAP_FUNDING_MEMPOOL
             else:
-                msg += messages.MSG_FORWARD_SWAP_FUNDING_MEMPOOL
+                msg += messages.MSG_FORWARD_SWAP_FUNDING_MEMPOOL + messages.MSG_FORWARD_SWAP_HTLC_EXPIRY
+
+            def wallet_closing_warning_callback() -> Optional[str]:
+                # gets called when the wallet GUI is closed
+                warning = messages.MSG_REVERSE_SWAP_FUNDING_MEMPOOL if is_reverse \
+                    else messages.MSG_FORWARD_SWAP_FUNDING_MEMPOOL
+                if self.wallet.adb.get_tx_height(txid).height < 1:
+                    return _("Ongoing submarine swap") + ": " + warning
+            self.wallet.register_closing_warning_callback(wallet_closing_warning_callback)
+
             self.show_message_signal.emit(msg)
         else:
             msg += _("Lightning funds were not received.")  # FIXME should this not depend on is_reverse?

electrum/wallet.py

@@ -34,7 +34,8 @@
 from functools import partial
 from collections import defaultdict
 from decimal import Decimal
-from typing import TYPE_CHECKING, List, Optional, Tuple, Union, NamedTuple, Sequence, Dict, Any, Set, Iterable, Mapping
+from typing import (TYPE_CHECKING, List, Optional, Tuple, Union, NamedTuple, Sequence,
+                    Dict, Any, Set, Iterable, Mapping, Callable)
 from abc import ABC, abstractmethod
 import itertools
 import threading
@@ -401,6 +402,7 @@ def __init__(self, db: WalletDB, *, config: SimpleConfig):
         db.load_addresses(self.wallet_type)
         self.keystore = None  # type: Optional[KeyStore]  # will be set by load_keystore
         self._password_in_memory = None  # see self.unlock
+        self.closing_warning_callbacks = []  # type: List[Callable[[], Optional[str]]]
         Logger.__init__(self)
 
         self.network = None
@@ -3456,6 +3458,21 @@ def add_future_tx(self, sweep_info: 'SweepInfo', wanted_height: int):
         util.trigger_callback('wallet_updated', self)
         self.adb.set_future_tx(tx.txid(), wanted_height=wanted_height)
 
+    def register_closing_warning_callback(
+        self,
+        callback: Callable[[], Optional[str]],
+        *,
+        only_gui: Optional[bool] = True
+    ) -> None:
+        """
+        Registers a callback that will be called when the wallet is closed. If the callback
+        returns a string it will be shown to the user as a warning to prevent them closing the wallet.
+        """
+        if only_gui and not self.config.get("cmd") == "gui":
+            return
+        self.logger.debug(f"registering wallet closing warning callback")
+        self.closing_warning_callbacks.append(callback)
+
 
 class Simple_Wallet(Abstract_Wallet):
     # wallet with a single keystore