[macOS] Added QR scanner facility using platform-native helper app.

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "contrib/deterministic-build/electrum-locale"]
 	path = contrib/deterministic-build/electrum-locale
 	url = https://github.com/spesmilo/electrum-locale
+[submodule "contrib/CalinsQRReader"]
+	path = contrib/CalinsQRReader
+	url = https://github.com/spesmilo/CalinsQRReader

contrib/CalinsQRReader

@@ -0,0 +1 @@
+Subproject commit 20189155a461cf7fbad14357e58fbc8e7c964608

contrib/build-osx/base.sh

@@ -21,7 +21,7 @@ function DoCodeSignMaybe { # ARGS: infoName fileOrDirName codesignIdentity
     identity="$3"
     deep=""
     if [ -z "$identity" ]; then
-        # we are ok with them not passing anything -- master script calls us always even if no identity is specified
+        # we are ok with them not passing anything; master script calls us unconditionally even if no identity is specified
         return
     fi
     if [ -d "$file" ]; then

contrib/build-osx/make_osx

@@ -16,6 +16,7 @@ export PYTHONHASHSEED=22
 VERSION=`git describe --tags --dirty --always`
 
 which brew > /dev/null 2>&1 || fail "Please install brew from https://brew.sh/ to continue"
+which xcodebuild > /dev/null 2>&1 || fail "Please install Xcode and xcode command line tools to continue"
 
 # Code Signing: See https://developer.apple.com/library/archive/documentation/Security/Conceptual/CodeSigningGuide/Procedures/Procedures.html
 APP_SIGN=""
@@ -87,6 +88,14 @@ popd
 cp $BUILDDIR/secp256k1/.libs/libsecp256k1.0.dylib contrib/build-osx
 DoCodeSignMaybe "libsecp256k1" "contrib/build-osx/libsecp256k1.0.dylib" "$APP_SIGN" # If APP_SIGN is empty will be a noop
 
+info "Building CalinsQRReader..."
+d=contrib/CalinsQRReader
+pushd $d
+rm -fr build
+xcodebuild || fail "Could not build CalinsQRReader"
+popd
+DoCodeSignMaybe "CalinsQRReader.app" "${d}/build/Release/CalinsQRReader.app" "$APP_SIGN" # If APP_SIGN is empty will be a noop
+
 
 info "Installing requirements..."
 python3 -m pip install -Ir ./contrib/deterministic-build/requirements.txt --user && \

contrib/build-osx/osx.spec

@@ -41,6 +41,9 @@ datas += collect_data_files('btchip')
 datas += collect_data_files('keepkeylib')
 datas += collect_data_files('ckcc')
 
+# Add the QR Scanner helper app
+datas += [(electrum + "contrib/CalinsQRReader/build/Release/CalinsQRReader.app", "./contrib/CalinsQRReader/build/Release/CalinsQRReader.app")]
+
 # Add libusb so Trezor and Safe-T mini will work
 binaries = [(electrum + "contrib/build-osx/libusb-1.0.dylib", ".")]
 binaries += [(electrum + "contrib/build-osx/libsecp256k1.0.dylib", ".")]

electrum/qrscanner.py

@@ -40,7 +40,7 @@ except BaseException:
     libzbar = None
 
 
-def scan_barcode(device='', timeout=-1, display=True, threaded=False, try_again=True):
+def scan_barcode_ctypes(device='', timeout=-1, display=True, threaded=False, try_again=True):
     if libzbar is None:
         raise RuntimeError("Cannot start QR scanner; zbar not available.")
     libzbar.zbar_symbol_get_data.restype = ctypes.c_char_p
@@ -69,6 +69,29 @@ def scan_barcode(device='', timeout=-1, display=True, threaded=False, try_again=
     data = libzbar.zbar_symbol_get_data(symbol)
     return data.decode('utf8')
 
+def scan_barcode_osx(*args_ignored, **kwargs_ignored):
+    import subprocess
+    # NOTE: This code needs to be modified if the positions of this file changes with respect to the helper app!
+    # This assumes the built macOS .app bundle which ends up putting the helper app in
+    # .app/contrib/CalinsQRReader/build/Release/CalinsQRReader.app.
+    root_ec_dir = os.path.abspath(os.path.dirname(__file__) + "/../")
+    prog = root_ec_dir + "/" + "contrib/CalinsQRReader/build/Release/CalinsQRReader.app/Contents/MacOS/CalinsQRReader"
+    if not os.path.exists(prog):
+        raise RuntimeError("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)
+        # Just like the zbar implementation -- the main app will hang until the QR window returns a QR code
+        # (or is closed). Communication with the subprocess is done via stdout.
+        # See contrib/CalinsQRReader for the helper app source code.
+        with subprocess.Popen([prog], stdout=subprocess.PIPE) as p:
+            data = p.stdout.read().decode('utf-8').strip()
+        return data
+    except OSError as e:
+        raise RuntimeError("Cannot start camera helper app; {}".format(e.strerror))
+
+scan_barcode = scan_barcode_osx if sys.platform == 'darwin' else scan_barcode_ctypes
+
 def _find_system_cameras():
     device_root = "/sys/class/video4linux"
     devices = {} # Name -> device