Add KeyboardArrowListener to experiment with hz arrow key support on lists

lib/ui/common/keyboard_arrows_listener.dart

@@ -0,0 +1,56 @@
+import 'package:wonders/common_libs.dart';
+
+class ArrowDir {
+  ArrowDir(this.hz, this.vt);
+  int hz;
+  int vt;
+
+  bool get isNotZero => hz != 0 || vt != 0;
+}
+
+class KeyboardArrowsListener extends StatefulWidget {
+  const KeyboardArrowsListener({Key? key, required this.child, required this.onArrow}) : super(key: key);
+  final Widget child;
+  final void Function(ArrowDir dir) onArrow;
+  @override
+  State<KeyboardArrowsListener> createState() => _KeyboardArrowsListenerState();
+}
+
+class _KeyboardArrowsListenerState extends State<KeyboardArrowsListener> {
+  final FocusNode _focusNode = FocusNode();
+
+  @override
+  Widget build(BuildContext context) {
+    return RawKeyboardListener(
+      autofocus: true,
+      focusNode: _focusNode,
+      onKey: _handleKey,
+      child: widget.child,
+    );
+  }
+
+  void _handleKey(RawKeyEvent event) {
+    if (event is! RawKeyDownEvent) return;
+    if (event.repeat) return;
+    final arrowDir = ArrowDir(0, 0);
+    if (event.logicalKey == LogicalKeyboardKey.arrowLeft) {
+      arrowDir.hz = -1;
+    } else if (event.logicalKey == LogicalKeyboardKey.arrowRight) {
+      arrowDir.hz = 1;
+    }
+    if (event.logicalKey == LogicalKeyboardKey.arrowUp) {
+      arrowDir.vt = 1;
+    } else if (event.logicalKey == LogicalKeyboardKey.arrowDown) {
+      arrowDir.vt = -1;
+    }
+    if (arrowDir.isNotZero) {
+      widget.onArrow(arrowDir);
+    }
+  }
+
+  @override
+  void dispose() {
+    _focusNode.dispose();
+    super.dispose();
+  }
+}