hww: fix some threading issues in wizard

fixes #3377
related: #6064  (passphrase dialog not rendered correctly)

electrum/base_wizard.py

@@ -158,6 +158,13 @@ class BaseWizard(Logger):
                 exc = e
         self.waiting_dialog(do_upgrade, _('Upgrading wallet format...'), on_finished=on_finished)
 
+    def run_task_without_blocking_gui(self, task, *, msg: str = None) -> Any:
+        """Perform a task in a thread without blocking the GUI.
+        Returns the result of 'task', or raises the same exception.
+        This method blocks until 'task' is finished.
+        """
+        raise NotImplementedError()
+
     def load_2fa(self):
         self.data['wallet_type'] = '2fa'
         self.data['use_trustedcoin'] = True
@@ -421,6 +428,7 @@ class BaseWizard(Logger):
     def on_hw_derivation(self, name, device_info: 'DeviceInfo', derivation, xtype):
         from .keystore import hardware_keystore
         devmgr = self.plugins.device_manager
+        assert isinstance(self.plugin, HW_PluginBase)
         try:
             xpub = self.plugin.get_xpub(device_info.device.id_, derivation, xtype, self)
             client = devmgr.client_by_id(device_info.device.id_)

electrum/gui/qt/installwizard.py

@@ -529,6 +529,26 @@ class InstallWizard(QDialog, MessageBoxMixin, BaseWizard):
         if on_finished:
             on_finished()
 
+    def run_task_without_blocking_gui(self, task, *, msg=None):
+        assert self.gui_thread == threading.current_thread(), 'must be called from GUI thread'
+        if msg is None:
+            msg = _("Please wait...")
+
+        exc = None  # type: Optional[Exception]
+        res = None
+        def task_wrapper():
+            nonlocal exc
+            nonlocal res
+            try:
+                task()
+            except Exception as e:
+                exc = e
+        self.waiting_dialog(task_wrapper, msg=msg)
+        if exc is None:
+            return res
+        else:
+            raise exc
+
     @wizard_dialog
     def choice_dialog(self, title, message, choices, run_next):
         c_values = [x[0] for x in choices]

electrum/plugins/digitalbitbox/digitalbitbox.py

@@ -707,7 +707,8 @@ class DigitalBitboxPlugin(HW_PluginBase):
         client = self.scan_and_create_client_for_device(device_id=device_id, wizard=wizard)
         if purpose == HWD_SETUP_NEW_WALLET:
             client.setupRunning = True
-        client.get_xpub("m/44'/0'", 'standard')
+        wizard.run_task_without_blocking_gui(
+            task=lambda: client.get_xpub("m/44'/0'", 'standard'))
 
 
     def is_mobile_paired(self):

electrum/plugins/hw_wallet/plugin.py

@@ -78,6 +78,8 @@ class HW_PluginBase(BasePlugin):
         """Called when creating a new wallet or when using the device to decrypt
         an existing wallet. Select the device to use.  If the device is
         uninitialized, go through the initialization process.
+
+        Runs in GUI thread.
         """
         raise NotImplementedError()
 

electrum/plugins/keepkey/keepkey.py

@@ -279,7 +279,8 @@ class KeepKeyPlugin(HW_PluginBase):
         client = self.scan_and_create_client_for_device(device_id=device_id, wizard=wizard)
         if not device_info.initialized:
             self.initialize_device(device_id, wizard, client.handler)
-        client.get_xpub('m', 'standard')
+        wizard.run_task_without_blocking_gui(
+            task=lambda: client.get_xpub("m", 'standard'))
         client.used()
 
     def get_xpub(self, device_id, derivation, xtype, wizard):

electrum/plugins/ledger/ledger.py

@@ -591,7 +591,8 @@ class LedgerPlugin(HW_PluginBase):
     def setup_device(self, device_info, wizard, purpose):
         device_id = device_info.device.id_
         client = self.scan_and_create_client_for_device(device_id=device_id, wizard=wizard)
-        client.get_xpub("m/44'/0'", 'standard') # TODO replace by direct derivation once Nano S > 1.1
+        wizard.run_task_without_blocking_gui(
+            task=lambda: client.get_xpub("m/44'/0'", 'standard'))  # TODO replace by direct derivation once Nano S > 1.1
 
     def get_xpub(self, device_id, derivation, xtype, wizard):
         if xtype not in self.SUPPORTED_XTYPES:

electrum/plugins/safe_t/safe_t.py

@@ -253,7 +253,8 @@ class SafeTPlugin(HW_PluginBase):
         client = self.scan_and_create_client_for_device(device_id=device_id, wizard=wizard)
         if not device_info.initialized:
             self.initialize_device(device_id, wizard, client.handler)
-        client.get_xpub('m', 'standard')
+        wizard.run_task_without_blocking_gui(
+            task=lambda: client.get_xpub("m", 'standard'))
         client.used()
 
     def get_xpub(self, device_id, derivation, xtype, wizard):

electrum/plugins/trezor/trezor.py

@@ -280,7 +280,8 @@ class TrezorPlugin(HW_PluginBase):
         if not device_info.initialized:
             self.initialize_device(device_id, wizard, client.handler)
         is_creating_wallet = purpose == HWD_SETUP_NEW_WALLET
-        client.get_xpub('m', 'standard', creating=is_creating_wallet)
+        wizard.run_task_without_blocking_gui(
+            task=lambda: client.get_xpub('m', 'standard', creating=is_creating_wallet))
         client.used()
 
     def get_xpub(self, device_id, derivation, xtype, wizard):