Qt PayToEdit: add option to scan QR code from screen(shot)

this ports the following commits:
448376e441
6053f6f696

electrum/gui/qt/qrreader/__init__.py

@@ -22,14 +22,15 @@
 # Note: this module is safe to import on all platforms.
 
 import sys
-from typing import Callable, Optional, TYPE_CHECKING, Mapping
+from typing import Callable, Optional, TYPE_CHECKING, Mapping, Sequence
 
 from PyQt5.QtWidgets import QMessageBox, QWidget
+from PyQt5.QtGui import QImage
 
 from electrum.i18n import _
 from electrum.util import UserFacingException
 from electrum.logging import get_logger
-from electrum.qrreader import MissingQrDetectionLib
+from electrum.qrreader import get_qr_reader, QrCodeResult, MissingQrDetectionLib
 
 from electrum.gui.qt.util import MessageBoxMixin, custom_message_box
 
@@ -47,12 +48,26 @@ def scan_qrcode(
         config: 'SimpleConfig',
         callback: Callable[[bool, str, Optional[str]], None],
 ) -> None:
+    """Scans QR code using camera."""
     if sys.platform == 'darwin' or sys.platform in ('windows', 'win32'):
         _scan_qrcode_using_qtmultimedia(parent=parent, config=config, callback=callback)
     else:  # desktop Linux and similar
         _scan_qrcode_using_zbar(parent=parent, config=config, callback=callback)
 
 
+def scan_qr_from_image(image: QImage) -> Sequence[QrCodeResult]:
+    """Might raise exception: MissingQrDetectionLib."""
+    qr_reader = get_qr_reader()
+    image_y800 = image.convertToFormat(QImage.Format_Grayscale8)
+    res = qr_reader.read_qr_code(
+        image_y800.constBits().__int__(), image_y800.byteCount(),
+        image_y800.bytesPerLine(),
+        image_y800.width(),
+        image_y800.height()
+    )
+    return res
+
+
 def find_system_cameras() -> Mapping[str, str]:
     """Returns a camera_description -> camera_path map."""
     if sys.platform == 'darwin' or sys.platform in ('windows', 'win32'):

electrum/gui/qt/qrtextedit.py

@@ -30,7 +30,9 @@ class ScanQRTextEdit(ButtonsTextEdit, MessageBoxMixin):
 
     def contextMenuEvent(self, e):
         m = self.createStandardContextMenu()
-        m.addAction(_("Read QR code"), self.on_qr_input_btn)
+        m.addSeparator()
+        m.addAction(_("Read QR code from camera"), self.on_qr_from_camera_input_btn)
+        m.addAction(_("Read QR code from screen"), self.on_qr_from_screenshot_input_btn)
         m.exec_(e.globalPos())
 
 
@@ -46,6 +48,8 @@ class ScanShowQRTextEdit(ButtonsTextEdit, MessageBoxMixin):
 
     def contextMenuEvent(self, e):
         m = self.createStandardContextMenu()
-        m.addAction(_("Read QR code"), self.on_qr_input_btn)
+        m.addSeparator()
+        m.addAction(_("Read QR code from camera"), self.on_qr_from_camera_input_btn)
+        m.addAction(_("Read QR code from screen"), self.on_qr_from_screenshot_input_btn)
         m.addAction(_("Show as QR code"), self.on_qr_show_btn)
         m.exec_(e.globalPos())

electrum/gui/qt/util.py

@@ -30,6 +30,7 @@ from electrum.i18n import _, languages
 from electrum.util import FileImportFailed, FileExportFailed, make_aiohttp_session, resource_path
 from electrum.invoices import PR_UNPAID, PR_PAID, PR_EXPIRED, PR_INFLIGHT, PR_UNKNOWN, PR_FAILED, PR_ROUTING, PR_UNCONFIRMED
 from electrum.logging import Logger
+from electrum.qrreader import MissingQrDetectionLib
 
 if TYPE_CHECKING:
     from .main_window import ElectrumWindow
@@ -879,7 +880,7 @@ class OverlayControlMixin:
         # The old code positioned the items the other way around, so we just insert at position 0 instead
         self.overlay_layout.insertWidget(0, widget)
 
-    def addButton(self, icon_name: str, on_click, tooltip: str) -> QAbstractButton:
+    def addButton(self, icon_name: str, on_click, tooltip: str) -> QPushButton:
         button = QPushButton(self.overlay_widget)
         button.setToolTip(tooltip)
         button.setIcon(read_QIcon(icon_name))
@@ -943,7 +944,7 @@ class OverlayControlMixin:
     ):
         if setText is None:
             setText = self.setText
-        def qr_input():
+        def qr_from_camera_input() -> None:
             def cb(success: bool, error: str, data):
                 if not success:
                     if error:
@@ -960,10 +961,39 @@ class OverlayControlMixin:
             from .qrreader import scan_qrcode
             scan_qrcode(parent=self, config=config, callback=cb)
 
+        def qr_from_screenshot_input() -> None:
+            from .qrreader import scan_qr_from_image
+            scanned_qr = None
+            for screen in QApplication.instance().screens():
+                try:
+                    scan_result = scan_qr_from_image(screen.grabWindow(0).toImage())
+                except MissingQrDetectionLib as e:
+                    show_error(_("Unable to scan image.") + "\n" + repr(e))
+                    return
+                if len(scan_result) > 0:
+                    if (scanned_qr is not None) or len(scan_result) > 1:
+                        show_error(_("More than one QR code was found on the screen."))
+                        return
+                    scanned_qr = scan_result
+            if scanned_qr is None:
+                show_error(_("No QR code was found on the screen."))
+                return
+            data = scanned_qr[0].data
+            if allow_multi:
+                new_text = self.text() + data + '\n'
+            else:
+                new_text = data
+            setText(new_text)
+
         icon = "camera_white.png" if ColorScheme.dark_scheme else "camera_dark.png"
-        self.addButton(icon, qr_input, _("Read QR code"))
-        # side-effect: we export this method:
-        self.on_qr_input_btn = qr_input
+        btn = self.addButton(icon, lambda: None, _("Read QR code"))
+        menu = QMenu()
+        menu.addAction(_("Read QR code from camera"), qr_from_camera_input)
+        menu.addAction(_("Read QR code from screen"), qr_from_screenshot_input)
+        btn.setMenu(menu)
+        # side-effect: we export these methods:
+        self.on_qr_from_camera_input_btn = qr_from_camera_input
+        self.on_qr_from_screenshot_input_btn = qr_from_screenshot_input
 
     def add_file_input_button(
             self,