Require a two-finger double tap for connection options

Co-authored-by: Terp <5856f6900e8e0a4e0ea1f4f8d2ee33e4753d2119bc122f94ecafc660b46c0511@buzz.block.builderlab.xyz>
Signed-off-by: kenny lopez <klopez4212@gmail.com>

mobile/lib/features/pairing/pairing_page.dart

@@ -14,6 +14,7 @@ import 'package:flutter/foundation.dart';
 import '../../shared/widgets/frosted_app_bar.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter/semantics.dart';
+import 'package:flutter/gestures.dart';
 import 'package:flutter_hooks/flutter_hooks.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:buzz/shared/theme/buzz_icons.dart';
@@ -36,6 +37,7 @@ part 'pairing_page/onboarding_background.dart';
 part 'pairing_page/onboarding_colors.dart';
 part 'pairing_page/onboarding_glass_button.dart';
 part 'pairing_page/pairing_welcome_view.dart';
+part 'pairing_page/two_finger_double_tap.dart';
 part 'pairing_page/community_link_form.dart';
 part 'pairing_page/onboarding_connection_view.dart';
 part 'pairing_page/sas_verification_view.dart';

mobile/lib/features/pairing/pairing_page/pairing_welcome_view.dart

@@ -345,10 +345,7 @@ class _PairingWelcomeView extends HookWidget {
               child: Column(
                 children: [
                   Expanded(
-                    // Keep double-tap recognition off the action buttons so
-                    // their single taps do not wait for the double-tap timeout.
-                    child: GestureDetector(
-                      behavior: HitTestBehavior.opaque,
+                    child: _TwoFingerDoubleTapSurface(
                       onDoubleTap: canRevealOptions ? revealOptions : null,
                       child: Center(
                         child: Column(

mobile/lib/features/pairing/pairing_page/two_finger_double_tap.dart

@@ -0,0 +1,83 @@
+part of '../pairing_page.dart';
+
+class _TwoFingerDoubleTapSurface extends HookWidget {
+  const _TwoFingerDoubleTapSurface({required this.child, this.onDoubleTap});
+
+  final Widget child;
+  final VoidCallback? onDoubleTap;
+
+  @override
+  Widget build(BuildContext context) {
+    final taps = useMemoized(_TwoFingerTapTracker.new, [onDoubleTap != null]);
+    return Listener(
+      behavior: HitTestBehavior.opaque,
+      onPointerDown: onDoubleTap == null ? null : taps.down,
+      onPointerMove: onDoubleTap == null ? null : taps.move,
+      onPointerCancel: onDoubleTap == null ? null : (_) => taps.cancel(),
+      onPointerUp: onDoubleTap == null
+          ? null
+          : (event) => taps.up(event, onDoubleTap!),
+      child: child,
+    );
+  }
+}
+
+// Observe two short, stationary two-finger chords without competing with taps
+// or scrolling in Flutter's gesture arena.
+class _TwoFingerTapTracker {
+  final _starts = <int, Offset>{};
+  final _down = <int>{};
+  Duration _started = Duration.zero;
+  Duration? _previousEnd;
+  Offset? _previousCenter;
+  bool _valid = true;
+
+  void down(PointerDownEvent event) {
+    if (_down.isEmpty) {
+      _starts.clear();
+      _started = event.timeStamp;
+      _valid = true;
+    }
+    _starts[event.pointer] = event.position;
+    _down.add(event.pointer);
+    if (_starts.length > 2) _valid = false;
+  }
+
+  void move(PointerMoveEvent event) {
+    final start = _starts[event.pointer];
+    if (start != null && (event.position - start).distance > kTouchSlop) {
+      _valid = false;
+    }
+  }
+
+  void cancel() {
+    _down.clear();
+    _starts.clear();
+    _previousEnd = null;
+    _previousCenter = null;
+    _valid = false;
+  }
+
+  void up(PointerUpEvent event, VoidCallback onDoubleTap) {
+    if (!_down.remove(event.pointer) || _down.isNotEmpty) return;
+    if (!_valid ||
+        _starts.length != 2 ||
+        event.timeStamp - _started > kDoubleTapTimeout) {
+      cancel();
+      return;
+    }
+    final center = (_starts.values.first + _starts.values.last) / 2;
+    final gap = _previousEnd == null ? null : _started - _previousEnd!;
+    final isDouble =
+        gap != null &&
+        gap >= kDoubleTapMinTime &&
+        gap <= kDoubleTapTimeout &&
+        (center - _previousCenter!).distance <= kDoubleTapSlop;
+    _previousEnd = event.timeStamp;
+    _previousCenter = center;
+    if (isDouble) {
+      cancel();
+      onDoubleTap();
+    }
+  }
+}

mobile/test/features/onboarding/hosted_communities_test.dart

@@ -298,7 +298,27 @@ void main() {
 }
 
 Future<void> revealOptions(WidgetTester tester) async {
+  // Ordinary double taps must not expose the hidden connection options.
   await tester.tapAt(const Offset(24, 120));
   await tester.pump(const Duration(milliseconds: 50));
   await tester.tapAt(const Offset(24, 120));
+  await tester.pumpAndSettle();
+  expect(find.text('Use a pairing code').hitTestable(), findsNothing);
+
+  for (var tap = 0; tap < 2; tap++) {
+    final first = await tester.createGesture(pointer: 11);
+    final second = await tester.createGesture(pointer: 12);
+    await first.down(
+      const Offset(24, 120),
+      timeStamp: Duration(milliseconds: tap * 70),
+    );
+    await second.down(
+      const Offset(70, 120),
+      timeStamp: Duration(milliseconds: tap * 70),
+    );
+    await tester.pump(const Duration(milliseconds: 20));
+    await first.up(timeStamp: Duration(milliseconds: tap * 70 + 20));
+    await second.up(timeStamp: Duration(milliseconds: tap * 70 + 20));
+    await tester.pump(const Duration(milliseconds: 50));
+  }
 }