qt: replace BlockingWaitingDialog with RunCoroutineDialog

RunCoroutineDialog has a run() method that blocks the thread
without blocking the GUI (using exec), and a Cancel button
that cancels the coroutine.

main_window.run_coroutine_dialog() is a wrapper that returns
the coroutine result and may raise exceptions.

BlockingWaitingDialog was removed is transaction_dialog,
where it was not particularly useful.

electrum/gui/qt/confirm_tx_dialog.py

@@ -42,7 +42,7 @@ from electrum.simple_config import SimpleConfig
 from electrum.bitcoin import DummyAddress
 
 from .util import (WindowModalDialog, ColorScheme, HelpLabel, Buttons, CancelButton,
-                   BlockingWaitingDialog, PasswordLineEdit, WWLabel, read_QIcon)
+                   PasswordLineEdit, WWLabel, read_QIcon)
 
 from .fee_slider import FeeSlider, FeeComboBox
 
@@ -619,7 +619,7 @@ class ConfirmTxDialog(TxEditor):
             title=_("New Transaction"), # todo: adapt title for channel funding tx, swaps
             allow_preview=allow_preview)
 
-        BlockingWaitingDialog(window, _("Preparing transaction..."), self.update)
+        self.update()
 
     def _update_amount_label(self):
         tx = self.tx

electrum/gui/qt/main_window.py

@@ -90,7 +90,7 @@ from .util import (read_QIcon, ColorScheme, text_dialog, icon_path, WaitingDialo
                    import_meta_gui, export_meta_gui,
                    filename_field, address_field, char_width_in_lineedit, webopen,
                    TRANSACTION_FILE_EXTENSION_FILTER_ANY, MONOSPACE_FONT,
-                   getOpenFileName, getSaveFileName, BlockingWaitingDialog, font_height)
+                   getOpenFileName, getSaveFileName, font_height)
 from .util import ButtonsLineEdit, ShowQRLineEdit
 from .util import QtEventListener, qt_event_listener, event_listener
 from .wizard.wallet import WIF_HELP_TEXT
@@ -301,26 +301,11 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger, QtEventListener):
             self._update_check_thread.checked.connect(on_version_received)
             self._update_check_thread.start()
 
-    def run_coroutine_dialog(self, coro, text, on_result, on_cancelled):
-        """ run coroutine in a waiting dialog, with a Cancel button that cancels the coroutine """
-        from electrum import util
-        loop = util.get_asyncio_loop()
-        assert util.get_running_loop() != loop, 'must not be called from asyncio thread'
-        future = asyncio.run_coroutine_threadsafe(coro, loop)
-        def task():
-            try:
-                return future.result()
-            except concurrent.futures.CancelledError:
-                on_cancelled()
-        try:
-            WaitingDialog(
-                self, text, task,
-                on_success=on_result,
-                on_error=self.on_error,
-                on_cancel=future.cancel)
-        except Exception as e:
-            self.show_error(str(e))
-            raise
+    def run_coroutine_dialog(self, coro, text):
+        """ run coroutine in a waiting dialog, with a Cancel button that cancels the coroutine"""
+        from .util import RunCoroutineDialog
+        d = RunCoroutineDialog(self, text, coro)
+        return d.run()
 
     def run_coroutine_from_thread(self, coro, name, on_result=None):
         if self._cleaned_up:
@@ -1180,10 +1165,9 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger, QtEventListener):
         if not self.wallet.lnworker.num_sats_can_send() and not self.wallet.lnworker.num_sats_can_receive():
             self.show_error(_("You do not have liquidity in your active channels."))
             return
-        def get_pairs_thread():
-            self.network.run_from_another_thread(self.wallet.lnworker.swap_manager.get_pairs())
         try:
-            BlockingWaitingDialog(self, _('Please wait...'), get_pairs_thread)
+            self.run_coroutine_dialog(
+                self.wallet.lnworker.swap_manager.get_pairs(), _('Please wait...'))
         except SwapServerError as e:
             self.show_error(str(e))
             return

electrum/gui/qt/swap_dialog.py

@@ -4,7 +4,7 @@ from PyQt6.QtCore import pyqtSignal
 from PyQt6.QtWidgets import QLabel, QVBoxLayout, QGridLayout, QPushButton
 
 from electrum.i18n import _
-from electrum.util import NotEnoughFunds, NoDynamicFeeEstimates
+from electrum.util import NotEnoughFunds, NoDynamicFeeEstimates, UserCancelled
 from electrum.bitcoin import DummyAddress
 from electrum.transaction import PartialTxOutput, PartialTransaction
 
@@ -319,25 +319,33 @@ class SwapDialog(WindowModalDialog, QtEventListener):
         recv_amount = self.recv_amount_e.get_amount()
         self.ok_button.setEnabled(bool(send_amount) and bool(recv_amount))
 
-    def do_normal_swap(self, lightning_amount, onchain_amount, password):
+    async def _do_normal_swap(self, lightning_amount, onchain_amount, password):
         dummy_tx = self._create_tx(onchain_amount)
         assert dummy_tx
         sm = self.swap_manager
+        swap, invoice = await sm.request_normal_swap(
+            lightning_amount_sat=lightning_amount,
+            expected_onchain_amount_sat=onchain_amount,
+            channels=self.channels,
+        )
+        self._current_swap = swap
+        tx = sm.create_funding_tx(swap, dummy_tx, password=password)
+        txid = await sm.wait_for_htlcs_and_broadcast(swap=swap, invoice=invoice, tx=tx)
+        return txid
+
+    def do_normal_swap(self, lightning_amount, onchain_amount, password):
         self._current_swap = None
-        async def coro():
-            swap, invoice = await sm.request_normal_swap(
-                lightning_amount_sat=lightning_amount,
-                expected_onchain_amount_sat=onchain_amount,
-                channels=self.channels,
-            )
-            self._current_swap = swap
-            tx = sm.create_funding_tx(swap, dummy_tx, password=password)
-            txid = await sm.wait_for_htlcs_and_broadcast(swap=swap, invoice=invoice, tx=tx)
-            return txid
-        self.window.run_coroutine_dialog(
-            coro(), _('Awaiting swap payment...'),
-            on_result=lambda funding_txid: self.window.on_swap_result(funding_txid, is_reverse=False),
-            on_cancelled=lambda: sm.cancel_normal_swap(self._current_swap))
+        coro = self._do_normal_swap(lightning_amount, onchain_amount, password)
+        try:
+            funding_txid = self.window.run_coroutine_dialog(coro, _('Awaiting swap payment...'))
+        except UserCancelled:
+            self.swap_manager.cancel_normal_swap(self._current_swap)
+            self.window.show_message(_('Swap cancelled'))
+            return
+        except Exception as e:
+            self.window.show_error(str(e))
+            return
+        self.window.on_swap_result(funding_txid, is_reverse=False)
 
     def get_description(self):
         onchain_funds = "onchain funds"

electrum/gui/qt/transaction_dialog.py

@@ -62,7 +62,7 @@ from .util import (MessageBoxMixin, read_QIcon, Buttons, icon_path,
                    char_width_in_lineedit, TRANSACTION_FILE_EXTENSION_FILTER_SEPARATE,
                    TRANSACTION_FILE_EXTENSION_FILTER_ONLY_COMPLETE_TX,
                    TRANSACTION_FILE_EXTENSION_FILTER_ONLY_PARTIAL_TX,
-                   BlockingWaitingDialog, getSaveFileName, ColorSchemeItem,
+                   getSaveFileName, ColorSchemeItem,
                    get_iconname_qrcode, VLine, WaitingDialog)
 from .rate_limiter import rate_limited
 from .my_treeview import create_toolbar_with_menu, QMenuWithConfig
@@ -582,11 +582,9 @@ class TxDialog(QDialog, MessageBoxMixin):
         # FIXME for PSBTs, we do a blocking fetch, as the missing data might be needed for e.g. signing
         # - otherwise, the missing data is for display-completeness only, e.g. fee, input addresses (we do it async)
         if not tx.is_complete() and tx.is_missing_info_from_network():
-            BlockingWaitingDialog(
-                self,
+            self.main_window.run_coroutine_dialog(
+                tx.add_info_from_network(self.wallet.network, timeout=10),
                 _("Adding info to tx, from network..."),
-                lambda: Network.run_from_another_thread(
-                    tx.add_info_from_network(self.wallet.network, timeout=10)),
             )
         else:
             self.maybe_fetch_txin_data()

electrum/gui/qt/util.py

@@ -21,7 +21,7 @@ from PyQt6.QtWidgets import (QPushButton, QLabel, QMessageBox, QHBoxLayout, QVBo
 
 from electrum.i18n import _
 from electrum.util import FileImportFailed, FileExportFailed, resource_path
-from electrum.util import EventListener, event_listener, get_logger
+from electrum.util import EventListener, event_listener, get_logger, UserCancelled
 from electrum.invoices import PR_UNPAID, PR_PAID, PR_EXPIRED, PR_INFLIGHT, PR_UNKNOWN, PR_FAILED, PR_ROUTING, PR_UNCONFIRMED, PR_BROADCASTING, PR_BROADCAST
 from electrum.logging import Logger
 from electrum.qrreader import MissingQrDetectionLib
@@ -371,32 +371,32 @@ class WaitingDialog(WindowModalDialog):
         self.message_label.setText(msg)
 
 
-class BlockingWaitingDialog(WindowModalDialog):
-    """Shows a waiting dialog whilst running a task.
-    Should be called from the GUI thread. The GUI thread will be blocked while
-    the task is running; the point of the dialog is to provide feedback
-    to the user regarding what is going on.
-    """
-    def __init__(self, parent: QWidget, message: str, task: Callable[[], Any]):
-        assert parent
-        if isinstance(parent, MessageBoxMixin):
-            parent = parent.top_level_window()
-        WindowModalDialog.__init__(self, parent, _("Please wait"))
-        self.message_label = QLabel(message)
-        vbox = QVBoxLayout(self)
-        vbox.addWidget(self.message_label)
-        self.finished.connect(self.deleteLater)  # see #3956
-        # show popup
-        self.show()
-        # refresh GUI; needed for popup to appear and for message_label to get drawn
-        QCoreApplication.processEvents()
-        QCoreApplication.processEvents()
-        try:
-            # block and run given task
-            task()
-        finally:
-            # close popup
-            self.accept()
+class RunCoroutineDialog(WaitingDialog):
+
+    def __init__(self, parent: QWidget, message: str, coroutine):
+        from electrum import util
+        import asyncio
+        import concurrent.futures
+        loop = util.get_asyncio_loop()
+        assert util.get_running_loop() != loop, 'must not be called from asyncio thread'
+        self._exception = None
+        self._result = None
+        self._future = asyncio.run_coroutine_threadsafe(coroutine, loop)
+        def task():
+            try:
+                self._result = self._future.result()
+            except concurrent.futures.CancelledError:
+                self._exception = UserCancelled
+            except Exception as e:
+                self._exception = e
+        WaitingDialog.__init__(self, parent, message, task, on_cancel=self._future.cancel)
+
+    def run(self):
+        self.exec()
+        if self._exception:
+            raise self._exception
+        else:
+            return self._result
 
 
 def line_dialog(parent, title, label, ok_label, default=None):