Scanner wedge mode (#437)

* Add code_scan_listener package

* Implement wedge controller widget

* Update barcode settings widget

- Allow user to choose which barcode scanner to use

* Fix typo

* Select barcode scanner widget based on user preference

* Fix rendering issues for wedge controller

* Update release notes

* Add unit test for wedge scanner widget

- Required some tweaks to other code

* Use better library

- https://github.com/fuadreza/flutter_barcode_listener
- Fork of https://github.com/shaxxx/flutter_barcode_listener
- Properly handles key "case" issues (shift, essentially)
- Verified that it works correctly for multiple character types

* Local copy of code, rather than relying on package which is not available on pub.dev

* Fix unit test

analysis_options.yaml

@@ -79,3 +79,4 @@ linter:
     no_leading_underscores_for_local_identifiers: false
 
     use_super_parameters: false
+

assets/release_notes.md

@@ -1,6 +1,7 @@
 ### 0.13.0 - October 2023
 ---
 
+- Adds "wedge scanner" mode, allowing use with external barcode readers
 - Add ability to scan in received items using supplier barcodes
 - Store API token, rather than username:password
 - Ensure that user will lose access if token is revoked by server

lib/app_colors.dart

@@ -6,6 +6,11 @@ const Color COLOR_GRAY_LIGHT = Color.fromRGBO(150, 150, 150, 1);
 // Return an "action" color based on the current theme
 Color get COLOR_ACTION {
 
+  // OneContext might not have context, e.g. in testing
+  if (!OneContext.hasContext) {
+    return Colors.lightBlue;
+  }
+
   BuildContext? context = OneContext().context;
 
   if (context != null) {

lib/barcode/barcode.dart

@@ -2,6 +2,7 @@ import "package:flutter/material.dart";
 
 import "package:flutter_speed_dial/flutter_speed_dial.dart";
 import "package:font_awesome_flutter/font_awesome_flutter.dart";
+import "package:inventree/preferences.dart";
 import "package:one_context/one_context.dart";
 
 
@@ -11,6 +12,7 @@ import "package:inventree/helpers.dart";
 import "package:inventree/l10.dart";
 
 import "package:inventree/barcode/camera_controller.dart";
+import "package:inventree/barcode/wedge_controller.dart";
 import "package:inventree/barcode/controller.dart";
 import "package:inventree/barcode/handler.dart";
 import "package:inventree/barcode/tones.dart";
@@ -44,6 +46,19 @@ Future<Object?> scanBarcode(BuildContext context, {BarcodeHandler? handler}) asy
   
   InvenTreeBarcodeController controller = CameraBarcodeController(handler);
 
+  // Select barcode controller based on user preference
+  final int barcodeControllerType = await InvenTreeSettingsManager().getValue(INV_BARCODE_SCAN_TYPE, BARCODE_CONTROLLER_CAMERA) as int;
+
+  switch (barcodeControllerType) {
+    case BARCODE_CONTROLLER_WEDGE:
+      controller = WedgeBarcodeController(handler);
+      break;
+    case BARCODE_CONTROLLER_CAMERA:
+    default:
+      // Already set as default option
+      break;
+  }
+
   return Navigator.of(context).push(
     PageRouteBuilder(
       pageBuilder: (context, _, __) => controller,

lib/barcode/controller.dart

@@ -58,9 +58,9 @@ class InvenTreeBarcodeControllerState extends State<InvenTreeBarcodeController>
       processingBarcode = true;
     });
 
-    BuildContext? context = OneContext().context;
+    BuildContext? context = OneContext.hasContext ? OneContext().context : null;
 
-    showLoadingOverlay(context!);
+    showLoadingOverlay(context);
     await pauseScan();
 
     await widget.handler.processBarcode(data);

lib/barcode/flutter_barcode_listener.dart

@@ -0,0 +1,175 @@
+
+/*
+ * Custom keyboard listener which allows the app to act as a keyboard "wedge",
+ * and intercept barcodes from any compatible scanner.
+ *
+ * Note: This code was copied from https://github.com/fuadreza/flutter_barcode_listener/blob/master/lib/flutter_barcode_listener.dart
+ *
+ * If that code becomes available on pub.dev, we can remove this file and reference that library
+ */
+
+import "dart:async";
+
+import "package:flutter/material.dart";
+import "package:flutter/services.dart";
+
+typedef BarcodeScannedCallback = void Function(String barcode);
+
+/// This widget will listen for raw PHYSICAL keyboard events
+/// even when other controls have primary focus.
+/// It will buffer all characters coming in specifed `bufferDuration` time frame
+/// that end with line feed character and call callback function with result.
+/// Keep in mind this widget will listen for events even when not visible.
+/// Windows seems to be using the [RawKeyDownEvent] instead of the
+/// [RawKeyUpEvent], this behaviour can be managed by setting [useKeyDownEvent].
+class BarcodeKeyboardListener extends StatefulWidget {
+
+  /// This widget will listen for raw PHYSICAL keyboard events
+  /// even when other controls have primary focus.
+  /// It will buffer all characters coming in specifed `bufferDuration` time frame
+  /// that end with line feed character and call callback function with result.
+  /// Keep in mind this widget will listen for events even when not visible.
+  const BarcodeKeyboardListener(
+      {Key? key,
+
+        /// Child widget to be displayed.
+        required this.child,
+
+        /// Callback to be called when barcode is scanned.
+        required Function(String) onBarcodeScanned,
+
+        /// When experiencing issueswith empty barcodes on Windows,
+        /// set this value to true. Default value is `false`.
+        this.useKeyDownEvent = false,
+
+        /// Maximum time between two key events.
+        /// If time between two key events is longer than this value
+        /// previous keys will be ignored.
+        Duration bufferDuration = hundredMs})
+      : _onBarcodeScanned = onBarcodeScanned,
+        _bufferDuration = bufferDuration,
+        super(key: key);
+
+  final Widget child;
+  final BarcodeScannedCallback _onBarcodeScanned;
+  final Duration _bufferDuration;
+  final bool useKeyDownEvent;
+
+  @override
+  _BarcodeKeyboardListenerState createState() => _BarcodeKeyboardListenerState(
+      _onBarcodeScanned, _bufferDuration, useKeyDownEvent);
+}
+
+const Duration aSecond = Duration(seconds: 1);
+const Duration hundredMs = Duration(milliseconds: 100);
+const String lineFeed = "\n";
+
+class _BarcodeKeyboardListenerState extends State<BarcodeKeyboardListener> {
+
+  _BarcodeKeyboardListenerState(this._onBarcodeScannedCallback,
+      this._bufferDuration, this._useKeyDownEvent) {
+    RawKeyboard.instance.addListener(_keyBoardCallback);
+    _keyboardSubscription =
+        _controller.stream.where((char) => char != null).listen(onKeyEvent);
+  }
+
+  List<String> _scannedChars = [];
+  DateTime? _lastScannedCharCodeTime;
+  late StreamSubscription<String?> _keyboardSubscription;
+
+  final BarcodeScannedCallback _onBarcodeScannedCallback;
+  final Duration _bufferDuration;
+
+  final _controller = StreamController<String?>();
+
+  final bool _useKeyDownEvent;
+
+  bool _isShiftPressed = false;
+  void onKeyEvent(String? char) {
+    //remove any pending characters older than bufferDuration value
+    checkPendingCharCodesToClear();
+    _lastScannedCharCodeTime = DateTime.now();
+    if (char == lineFeed) {
+      _onBarcodeScannedCallback.call(_scannedChars.join());
+      resetScannedCharCodes();
+    } else {
+      //add character to list of scanned characters;
+      _scannedChars.add(char!);
+    }
+  }
+
+  void checkPendingCharCodesToClear() {
+    if (_lastScannedCharCodeTime != null) {
+      if (_lastScannedCharCodeTime!
+          .isBefore(DateTime.now().subtract(_bufferDuration))) {
+        resetScannedCharCodes();
+      }
+    }
+  }
+
+  void resetScannedCharCodes() {
+    _lastScannedCharCodeTime = null;
+    _scannedChars = [];
+  }
+
+  void addScannedCharCode(String charCode) {
+    _scannedChars.add(charCode);
+  }
+
+  void _keyBoardCallback(RawKeyEvent keyEvent) {
+    if (keyEvent.logicalKey.keyId > 255 &&
+        keyEvent.data.logicalKey != LogicalKeyboardKey.enter &&
+        keyEvent.data.logicalKey != LogicalKeyboardKey.shiftLeft) return;
+    if ((!_useKeyDownEvent && keyEvent is RawKeyUpEvent) ||
+        (_useKeyDownEvent && keyEvent is RawKeyDownEvent)) {
+      if (keyEvent.data is RawKeyEventDataAndroid) {
+        if (keyEvent.data.logicalKey == LogicalKeyboardKey.shiftLeft) {
+          _isShiftPressed = true;
+        } else {
+          if (_isShiftPressed) {
+            _isShiftPressed = false;
+            _controller.sink.add(String.fromCharCode(
+                ((keyEvent.data) as RawKeyEventDataAndroid).codePoint).toUpperCase());
+          } else {
+            _controller.sink.add(String.fromCharCode(
+                ((keyEvent.data) as RawKeyEventDataAndroid).codePoint));
+          }
+        }
+      } else if (keyEvent.data is RawKeyEventDataFuchsia) {
+        _controller.sink.add(String.fromCharCode(
+            ((keyEvent.data) as RawKeyEventDataFuchsia).codePoint));
+      } else if (keyEvent.data.logicalKey == LogicalKeyboardKey.enter) {
+        _controller.sink.add(lineFeed);
+      } else if (keyEvent.data is RawKeyEventDataWeb) {
+        _controller.sink.add(((keyEvent.data) as RawKeyEventDataWeb).keyLabel);
+      } else if (keyEvent.data is RawKeyEventDataLinux) {
+        _controller.sink
+            .add(((keyEvent.data) as RawKeyEventDataLinux).keyLabel);
+      } else if (keyEvent.data is RawKeyEventDataWindows) {
+        _controller.sink.add(String.fromCharCode(
+            ((keyEvent.data) as RawKeyEventDataWindows).keyCode));
+      } else if (keyEvent.data is RawKeyEventDataMacOs) {
+        _controller.sink
+            .add(((keyEvent.data) as RawKeyEventDataMacOs).characters);
+      } else if (keyEvent.data is RawKeyEventDataIos) {
+        _controller.sink
+            .add(((keyEvent.data) as RawKeyEventDataIos).characters);
+      } else {
+        _controller.sink.add(keyEvent.character);
+      }
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return widget.child;
+  }
+
+  @override
+  void dispose() {
+    _keyboardSubscription.cancel();
+    _controller.close();
+    RawKeyboard.instance.removeListener(_keyBoardCallback);
+    super.dispose();
+  }
+}

lib/barcode/wedge_controller.dart

@@ -0,0 +1,102 @@
+
+import "package:flutter/material.dart";
+import "package:font_awesome_flutter/font_awesome_flutter.dart";
+
+import "package:inventree/app_colors.dart";
+import "package:inventree/barcode/controller.dart";
+import "package:inventree/barcode/handler.dart";
+import "package:inventree/barcode/flutter_barcode_listener.dart";
+import "package:inventree/l10.dart";
+import "package:inventree/helpers.dart";
+
+/*
+ * Barcode controller which acts as a keyboard wedge,
+ * intercepting barcode data which is entered as rapid keyboard presses
+ */
+class WedgeBarcodeController extends InvenTreeBarcodeController {
+
+  const WedgeBarcodeController(BarcodeHandler handler, {Key? key}) : super(handler, key: key);
+
+  @override
+  State<StatefulWidget> createState() => _WedgeBarcodeControllerState();
+
+}
+
+
+class _WedgeBarcodeControllerState extends InvenTreeBarcodeControllerState {
+
+  _WedgeBarcodeControllerState() : super();
+
+  bool canScan = true;
+
+  bool get scanning => mounted && canScan;
+
+  @override
+  Future<void> pauseScan() async {
+
+    if (mounted) {
+      setState(() {
+        canScan = false;
+      });
+    }
+  }
+
+  @override
+  Future<void> resumeScan() async {
+
+    if (mounted) {
+      setState(() {
+        canScan = true;
+      });
+    }
+  }
+
+  @override
+  Widget build(BuildContext context) {
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(L10().scanBarcode),
+      ),
+      backgroundColor: Colors.black.withOpacity(0.9),
+      body: Center(
+        child: Column(
+          mainAxisAlignment: MainAxisAlignment.center,
+          children: [
+            Spacer(flex: 5),
+            FaIcon(FontAwesomeIcons.barcode, size: 64),
+            Spacer(flex: 5),
+            BarcodeKeyboardListener(
+              useKeyDownEvent: true,
+              child: SizedBox(
+                child: CircularProgressIndicator(
+                  color: scanning ? COLOR_ACTION : COLOR_PROGRESS
+                ),
+                width: 64,
+                height: 64,
+              ),
+              onBarcodeScanned: (String barcode) {
+                debug("scanned: ${barcode}");
+                if (scanning) {
+                  // Process the barcode data
+                  handleBarcodeData(barcode);
+                }
+              },
+            ),
+            Spacer(flex: 5),
+            Padding(
+              child: Text(
+                widget.handler.getOverlayText(context),
+                style: TextStyle(
+                  fontWeight: FontWeight.bold,
+                  color: Colors.white)
+              ),
+              padding: EdgeInsets.all(20),
+            )
+          ],
+        )
+      )
+    );
+  }
+
+}

lib/l10n/app_en.arb

@@ -118,6 +118,12 @@
   "barcodeScanAssign": "Scan to assign barcode",
   "@barcodeScanAssign": {},
 
+  "barcodeScanController": "Scanner Input",
+  "@barcodeScanController": {},
+
+  "barcodeScanControllerDetail": "Select barcode scanner input source",
+  "@barcodeScanControllerDetail": {},
+
   "barcodeScanDelay": "Barcode Scan Delay",
   "@barcodeScanDelay": {},
 
@@ -169,6 +175,12 @@
   "building": "Building",
   "@building": {},
 
+  "cameraInternal": "Internal Camera",
+  "@cameraInternal": {},
+
+  "cameraInternalDetail": "Use internal camera to read barcodes",
+  "@cameraInternalDetail": {},
+
   "cancel": "Cancel",
   "@cancel": {
     "description": "Cancel"
@@ -1003,6 +1015,12 @@
   "scanIntoLocationDetail": "Scan this item into location",
   "@scanIntoLocationDetail": {},
 
+  "scannerExternal": "External Scanner",
+  "@scannerExternal": {},
+
+  "scannerExternalDetail": "Use external scanner to read barcodes (wedge mode)",
+  "@scannerExternalDetail": {},
+
   "scanReceivedParts": "Scan Received Parts",
   "@scanReceivedParts": {},
 

lib/preferences.dart

@@ -40,6 +40,11 @@ const String INV_STRICT_HTTPS = "strictHttps";
 
 // Barcode settings
 const String INV_BARCODE_SCAN_DELAY = "barcodeScanDelay";
+const String INV_BARCODE_SCAN_TYPE = "barcodeScanType";
+
+// Barcode scanner types
+const int BARCODE_CONTROLLER_CAMERA = 0;
+const int BARCODE_CONTROLLER_WEDGE = 1;
 
 /*
  * Class for storing InvenTree preferences in a NoSql DB

lib/settings/barcode_settings.dart

@@ -1,7 +1,9 @@
 import "package:flutter/material.dart";
 import "package:font_awesome_flutter/font_awesome_flutter.dart";
+
 import "package:inventree/l10.dart";
 import "package:inventree/preferences.dart";
+import "package:inventree/widget/dialogs.dart";
 
 
 class InvenTreeBarcodeSettingsWidget extends StatefulWidget {
@@ -15,6 +17,7 @@ class _InvenTreeBarcodeSettingsState extends State<InvenTreeBarcodeSettingsWidge
  _InvenTreeBarcodeSettingsState();
 
  int barcodeScanDelay = 500;
+ int barcodeScanType = BARCODE_CONTROLLER_CAMERA;
 
  final TextEditingController _barcodeScanDelayController = TextEditingController();
 
@@ -26,6 +29,7 @@ class _InvenTreeBarcodeSettingsState extends State<InvenTreeBarcodeSettingsWidge
 
   Future<void> loadSettings() async {
     barcodeScanDelay = await InvenTreeSettingsManager().getValue(INV_BARCODE_SCAN_DELAY, 500) as int;
+    barcodeScanType = await InvenTreeSettingsManager().getValue(INV_BARCODE_SCAN_TYPE, BARCODE_CONTROLLER_CAMERA) as int;
 
     if (mounted) {
       setState(() {
@@ -89,11 +93,55 @@ class _InvenTreeBarcodeSettingsState extends State<InvenTreeBarcodeSettingsWidge
 
   @override
   Widget build(BuildContext context) {
+
+    // Construct an icon for the barcode scanner input
+    Widget? barcodeInputIcon;
+
+    switch (barcodeScanType) {
+      case BARCODE_CONTROLLER_WEDGE:
+        barcodeInputIcon = Icon(Icons.barcode_reader);
+        break;
+      case BARCODE_CONTROLLER_CAMERA:
+      default:
+        barcodeInputIcon = FaIcon(FontAwesomeIcons.camera);
+        break;
+    }
+
     return Scaffold(
       appBar: AppBar(title: Text(L10().barcodes)),
       body: Container(
         child: ListView(
           children: [
+            ListTile(
+              title: Text(L10().barcodeScanController),
+              subtitle: Text(L10().barcodeScanControllerDetail),
+              leading: Icon(Icons.qr_code_scanner),
+              trailing: barcodeInputIcon,
+              onTap: () async {
+                choiceDialog(
+                  L10().barcodeScanController,
+                  [
+                    ListTile(
+                      title: Text(L10().cameraInternal),
+                      subtitle: Text(L10().cameraInternalDetail),
+                      leading: FaIcon(FontAwesomeIcons.camera),
+                    ),
+                    ListTile(
+                      title: Text(L10().scannerExternal),
+                      subtitle: Text(L10().scannerExternalDetail),
+                      leading: Icon(Icons.barcode_reader),
+                    )
+                  ],
+                  onSelected: (idx) async {
+                    barcodeScanType = idx as int;
+                    InvenTreeSettingsManager().setValue(INV_BARCODE_SCAN_TYPE, barcodeScanType);
+                    if (mounted) {
+                      setState(() {});
+                    }
+                  }
+                );
+              }
+            ),
             ListTile(
               title: Text(L10().barcodeScanDelay),
               subtitle: Text(L10().barcodeScanDelayDetail),
@@ -104,7 +152,7 @@ class _InvenTreeBarcodeSettingsState extends State<InvenTreeBarcodeSettingsWidge
                   _editBarcodeScanDelay(context);
                 },
               ),
-            )
+            ),
           ],
         )
       )

lib/widget/progress.dart

@@ -14,7 +14,12 @@ Widget progressIndicator() {
 }
 
 
-void showLoadingOverlay(BuildContext context) {
+void showLoadingOverlay(BuildContext? context) {
+
+  if (context == null) {
+    return;
+  }
+
   Loader.show(
     context,
     themeData: Theme.of(context).copyWith(colorScheme: ColorScheme.fromSwatch())

test/wedge_scanner_test.dart

@@ -0,0 +1,32 @@
+
+
+import "package:flutter/material.dart";
+import "package:flutter/services.dart";
+import "package:flutter_test/flutter_test.dart";
+import "package:inventree/barcode/barcode.dart";
+import "package:inventree/barcode/wedge_controller.dart";
+import "package:inventree/helpers.dart";
+
+
+void main() {
+  testWidgets("Wedge Scanner Test", (tester) async {
+
+    await tester.pumpWidget(
+      MaterialApp(
+        home: WedgeBarcodeController(BarcodeScanHandler())
+      )
+    );
+
+    // Generate some keyboard data
+    await simulateKeyDownEvent(LogicalKeyboardKey.keyA);
+    await simulateKeyDownEvent(LogicalKeyboardKey.keyB);
+    await simulateKeyDownEvent(LogicalKeyboardKey.keyC);
+    await simulateKeyDownEvent(LogicalKeyboardKey.enter);
+
+    // Check debug output
+    debugContains("scanned: abc");
+    debugContains("No match for barcode");
+    debugContains("Server Error");
+
+  });
+}