make parsing lightning qr codes more robust

electrum/gui/kivy/uix/screens.py

@@ -253,7 +253,7 @@ class SendScreen(CScreen):
             self.payment_request = None
 
     def do_paste(self):
-        data = self.app._clipboard.paste()
+        data = self.app._clipboard.paste().strip()
         if not data:
             self.app.show_info(_("Clipboard is empty"))
             return
@@ -267,9 +267,12 @@ class SendScreen(CScreen):
         if tx:
             self.app.tx_dialog(tx)
             return
+        lower = data.lower()
+        if lower.startswith('lightning:ln'):
+            lower = lower[10:]
         # try to decode as URI/address
-        if data.startswith('ln'):
-            self.set_ln_invoice(data.rstrip())
+        if lower.startswith('ln'):
+            self.set_ln_invoice(lower)
         else:
             self.set_URI(data)
             # save automatically

electrum/gui/qt/paytoedit.py

@@ -131,12 +131,12 @@ class PayToEdit(CompletionTextEdit, ScanQRTextEdit, Logger):
             if data.startswith("bitcoin:"):
                 self.win.pay_to_URI(data)
                 return
-            l = data.lower()
-            if l.startswith("lightning:"):
-                data = l[10:]
-            if data.startswith("ln"):
-                self.win.parse_lightning_invoice(data)
-                self.lightning_invoice = data
+            lower = data.lower()
+            if lower.startswith("lightning:ln"):
+                lower = lower[10:]
+            if lower.startswith("ln"):
+                self.win.parse_lightning_invoice(lower)
+                self.lightning_invoice = lower
                 return
             try:
                 self.payto_address = self.parse_output(data)