Improved password wrapper.

Doesn't require any particular argument order of the wrapped
function.
Caller can tell if the user cancelled the request or not.
Optionally handles parent window hints.

gui/qt/main_window.py

@@ -1081,7 +1081,31 @@ class ElectrumWindow(QMainWindow):
         self.completions.setStringList(l)
 
     def protected(func):
-        return lambda s, *args: s.do_protect(func, args)
+        '''Password request wrapper.  The password is passed to the function
+        as the 'password' named argument.  Return value is a 2-element
+        tuple: (Cancelled, Result) where Cancelled is True if the user
+        cancels the password request, otherwise False.  Result is the
+        return value of the wrapped function, or None if cancelled.
+        '''
+        def request_password(self, *args, **kwargs):
+            parent = kwargs.get('parent', self)
+            if self.wallet.use_encryption:
+                while True:
+                    password = self.password_dialog(parent=parent)
+                    if not password:
+                        return True, None
+                    try:
+                        self.wallet.check_password(password)
+                        break
+                    except Exception as e:
+                        QMessageBox.warning(parent, _('Error'), str(e), _('OK'))
+                        continue
+            else:
+                password = None
+
+            kwargs['password'] = password
+            return False, func(self, *args, **kwargs)
+        return request_password
 
     def read_send_tab(self):
         if self.payment_request and self.payment_request.has_expired():
@@ -1896,29 +1920,6 @@ class ElectrumWindow(QMainWindow):
         d = QRDialog(data, self, title)
         d.exec_()
 
-
-    def do_protect(self, func, args):
-        if self.wallet.use_encryption:
-            while True:
-                password = self.password_dialog()
-                if not password:
-                    return
-                try:
-                    self.wallet.check_password(password)
-                    break
-                except Exception as e:
-                    QMessageBox.warning(self, _('Error'), str(e), _('OK'))
-                    continue
-        else:
-            password = None
-
-        if args != (False,):
-            args = (self,) + args + (password,)
-        else:
-            args = (self, password)
-        apply(func, args)
-
-
     def show_public_keys(self, address):
         if not address: return
         try:
@@ -2098,8 +2099,10 @@ class ElectrumWindow(QMainWindow):
     def show_warning(self, msg):
         QMessageBox.warning(self, _('Warning'), msg, _('OK'))
 
-    def password_dialog(self, msg=None):
-        d = QDialog(self)
+    def password_dialog(self, msg=None, parent=None):
+        if parent == None:
+            parent = self
+        d = QDialog(parent)
         d.setModal(1)
         d.setWindowTitle(_("Enter Password"))
         pw = QLineEdit()