qrscanner: nicer error messages

electrum/gui/kivy/main_window.py

@@ -81,7 +81,8 @@ Label.register(
 
 
 from electrum.util import (NoDynamicFeeEstimates, NotEnoughFunds,
-                           BITCOIN_BIP21_URI_SCHEME, LIGHTNING_URI_SCHEME)
+                           BITCOIN_BIP21_URI_SCHEME, LIGHTNING_URI_SCHEME,
+                           UserFacingException)
 
 from .uix.dialogs.lightning_open_channel import LightningOpenChannelDialog
 from .uix.dialogs.lightning_channels import LightningChannelsDialog, SwapDialog
@@ -545,7 +546,10 @@ class ElectrumWindow(App, Logger):
             video_dev = self.electrum_config.get_video_device()
             data = qrscanner.scan_barcode(video_dev)
             on_complete(data)
+        except UserFacingException as e:
+            self.show_error(e)
         except BaseException as e:
+            self.logger.exception('camera error')
             self.show_error(repr(e))
 
     def do_share(self, data, title):

electrum/gui/qt/main_window.py

@@ -2701,7 +2701,11 @@ class ElectrumWindow(QMainWindow, MessageBoxMixin, Logger):
         from electrum import qrscanner
         try:
             data = qrscanner.scan_barcode(self.config.get_video_device())
+        except UserFacingException as e:
+            self.show_error(e)
+            return
         except BaseException as e:
+            self.logger.exception('camera error')
             self.show_error(repr(e))
             return
         if not data:

electrum/gui/qt/qrtextedit.py

@@ -3,6 +3,7 @@ from PyQt5.QtWidgets import QFileDialog
 from electrum.i18n import _
 from electrum.plugin import run_hook
 from electrum.simple_config import SimpleConfig
+from electrum.util import UserFacingException
 
 from .util import ButtonsTextEdit, MessageBoxMixin, ColorScheme, getOpenFileName
 
@@ -71,11 +72,14 @@ class ScanQRTextEdit(ButtonsTextEdit, MessageBoxMixin):
 
     def qr_input(self):
         from electrum import qrscanner
+        data = ''
         try:
             data = qrscanner.scan_barcode(self.config.get_video_device())
+        except UserFacingException as e:
+            self.show_error(e)
         except BaseException as e:
+            self.logger.exception('camera error')
             self.show_error(repr(e))
-            data = ''
         if not data:
             data = ''
         if self.allow_multi:

electrum/qrscanner.py

@@ -27,6 +27,8 @@ import os
 import sys
 import ctypes
 
+from .util import UserFacingException
+from .i18n import _
 from .logging import get_logger
 
 
@@ -53,7 +55,7 @@ except BaseException as e1:
 
 def scan_barcode_ctypes(device='', timeout=-1, display=True, threaded=False):
     if libzbar is None:
-        raise RuntimeError("Cannot start QR scanner; zbar not available.")
+        raise UserFacingException("Cannot start QR scanner: zbar not available.")
     libzbar.zbar_symbol_get_data.restype = ctypes.c_char_p
     libzbar.zbar_processor_create.restype = ctypes.POINTER(ctypes.c_int)
     libzbar.zbar_processor_get_results.restype = ctypes.POINTER(ctypes.c_int)
@@ -62,7 +64,9 @@ def scan_barcode_ctypes(device='', timeout=-1, display=True, threaded=False):
     proc = libzbar.zbar_processor_create(threaded)
     libzbar.zbar_processor_request_size(proc, 640, 480)
     if libzbar.zbar_processor_init(proc, device.encode('utf-8'), display) != 0:
-        raise RuntimeError("Can not start QR scanner; initialization failed.")
+        raise UserFacingException(
+            _("Cannot start QR scanner: initialization failed.") + "\n" +
+            _("Make sure you have a camera connected and enabled."))
     libzbar.zbar_processor_set_visible(proc)
     if libzbar.zbar_process_one(proc, timeout):
         symbols = libzbar.zbar_processor_get_results(proc)
@@ -85,7 +89,7 @@ def scan_barcode_osx(*args_ignored, **kwargs_ignored):
     root_ec_dir = os.path.abspath(os.path.dirname(__file__) + "/../")
     prog = root_ec_dir + "/" + "contrib/osx/CalinsQRReader/build/Release/CalinsQRReader.app/Contents/MacOS/CalinsQRReader"
     if not os.path.exists(prog):
-        raise RuntimeError("Cannot start QR scanner; helper app not found.")
+        raise UserFacingException("Cannot start QR scanner: helper app not found.")
     data = ''
     try:
         # This will run the "CalinsQRReader" helper app (which also gets bundled with the built .app)
@@ -96,7 +100,7 @@ def scan_barcode_osx(*args_ignored, **kwargs_ignored):
             data = p.stdout.read().decode('utf-8').strip()
         return data
     except OSError as e:
-        raise RuntimeError("Cannot start camera helper app; {}".format(e.strerror))
+        raise UserFacingException("Cannot start camera helper app: {}".format(e.strerror))
 
 scan_barcode = scan_barcode_osx if sys.platform == 'darwin' else scan_barcode_ctypes