fix #4575

electrum/gui/kivy/main_window.py

@@ -391,9 +391,16 @@ class ElectrumWindow(App):
         popup.export = self.export_private_keys
         popup.open()
 
-    def qr_dialog(self, title, data, show_text=False):
+    def qr_dialog(self, title, data, show_text=False, text_for_clipboard=None):
         from .uix.dialogs.qr_dialog import QRDialog
-        popup = QRDialog(title, data, show_text)
+        def on_qr_failure():
+            popup.dismiss()
+            msg = _('Failed to display QR code.')
+            if text_for_clipboard:
+                msg += '\n' + _('Text copied to clipboard.')
+                self._clipboard.copy(text_for_clipboard)
+            Clock.schedule_once(lambda dt: self.show_info(msg))
+        popup = QRDialog(title, data, show_text, on_qr_failure)
         popup.open()
 
     def scan_qr(self, on_complete):

electrum/gui/kivy/uix/dialogs/qr_dialog.py

@@ -36,11 +36,12 @@ Builder.load_string('''
 ''')
 
 class QRDialog(Factory.Popup):
-    def __init__(self, title, data, show_text):
+    def __init__(self, title, data, show_text, failure_cb=None):
         Factory.Popup.__init__(self)
         self.title = title
         self.data = data
         self.show_text = show_text
+        self.failure_cb = failure_cb
 
     def on_open(self):
-        self.ids.qr.set_data(self.data)
+        self.ids.qr.set_data(self.data, self.failure_cb)

electrum/gui/kivy/uix/dialogs/tx_dialog.py

@@ -179,6 +179,7 @@ class TxDialog(Factory.Popup):
 
     def show_qr(self):
         from electrum.bitcoin import base_encode, bfh
-        text = bfh(str(self.tx))
+        raw_tx = str(self.tx)
+        text = bfh(raw_tx)
         text = base_encode(text, base=43)
-        self.app.qr_dialog(_("Raw Transaction"), text)
+        self.app.qr_dialog(_("Raw Transaction"), text, text_for_clipboard=raw_tx)

electrum/gui/kivy/uix/qrcodewidget.py

@@ -5,6 +5,7 @@ from threading import Thread
 from functools import partial
 
 import qrcode
+from qrcode import exceptions
 
 from kivy.uix.floatlayout import FloatLayout
 from kivy.graphics.texture import Texture
@@ -50,15 +51,23 @@ class QRCodeWidget(FloatLayout):
         self.data = None
         self.qr = None
         self._qrtexture = None
+        self.failure_cb = None
 
     def on_data(self, instance, value):
         if not (self.canvas or value):
             return
+        try:
             self.update_qr()
+        except qrcode.exceptions.DataOverflowError:
+            if self.failure_cb:
+                self.failure_cb()
+            else:
+                raise
 
-    def set_data(self, data):
+    def set_data(self, data, failure_cb=None):
         if self.data == data:
             return
+        self.failure_cb = failure_cb
         MinSize = 210 if len(data) < 128 else 500
         self.setMinimumSize((MinSize, MinSize))
         self.data = data

electrum/gui/qt/transaction_dialog.py

@@ -31,6 +31,9 @@ from PyQt5.QtCore import *
 from PyQt5.QtGui import *
 from PyQt5.QtWidgets import *
 
+import qrcode
+from qrcode import exceptions
+
 from electrum.bitcoin import base_encode
 from electrum.i18n import _
 from electrum.plugin import run_hook
@@ -183,8 +186,11 @@ class TxDialog(QDialog, MessageBoxMixin):
         text = base_encode(text, base=43)
         try:
             self.main_window.show_qrcode(text, 'Transaction', parent=self)
+        except qrcode.exceptions.DataOverflowError:
+            self.show_error(_('Failed to display QR code.') + '\n' +
+                            _('Transaction is too large in size.'))
         except Exception as e:
-            self.show_message(str(e))
+            self.show_error(_('Failed to display QR code.') + '\n' + str(e))
 
     def sign(self):
         def sign_done(success):