Allow long press delay duration for LongPressDraggable to be adjustable (#74592)

packages/flutter/lib/src/widgets/drag_target.dart

@@ -398,6 +398,7 @@ class LongPressDraggable<T extends Object> extends Draggable<T> {
     VoidCallback? onDragCompleted,
     this.hapticFeedbackOnStart = true,
     bool ignoringFeedbackSemantics = true,
+    this.delay = kLongPressTimeout,
   }) : super(
     key: key,
     child: child,
@@ -419,9 +420,14 @@ class LongPressDraggable<T extends Object> extends Draggable<T> {
   /// Whether haptic feedback should be triggered on drag start.
   final bool hapticFeedbackOnStart;
 
+  /// The duration that a user has to press down before a long press is registered.
+  ///
+  /// Defaults to [kLongPressTimeout].
+  final Duration delay;
+
   @override
   DelayedMultiDragGestureRecognizer createRecognizer(GestureMultiDragStartCallback onStart) {
-    return DelayedMultiDragGestureRecognizer()
+    return DelayedMultiDragGestureRecognizer(delay: delay)
       ..onStart = (Offset position) {
         final Drag? result = onStart(position);
         if (result != null && hapticFeedbackOnStart)

packages/flutter/test/widgets/draggable_test.dart

@@ -2452,6 +2452,73 @@ void main() {
     expect(onDragStartedCalled, isTrue);
   });
 
+  testWidgets('Custom long press delay for LongPressDraggable', (WidgetTester tester) async {
+    bool onDragStartedCalled = false;
+    await tester.pumpWidget(MaterialApp(
+      home: LongPressDraggable<int>(
+        data: 1,
+        delay: const Duration(seconds: 2),
+        child: const Text('Source'),
+        feedback: const Text('Dragging'),
+        onDragStarted: () {
+          onDragStartedCalled = true;
+        },
+      ),
+    ));
+    expect(find.text('Source'), findsOneWidget);
+    expect(find.text('Dragging'), findsNothing);
+    expect(onDragStartedCalled, isFalse);
+    final Offset firstLocation = tester.getCenter(find.text('Source'));
+    await tester.startGesture(firstLocation, pointer: 7);
+    await tester.pump();
+    expect(find.text('Source'), findsOneWidget);
+    expect(find.text('Dragging'), findsNothing);
+    expect(onDragStartedCalled, isFalse);
+    // Halfway into the long press duration.
+    await tester.pump(const Duration(seconds: 1));
+    expect(find.text('Source'), findsOneWidget);
+    expect(find.text('Dragging'), findsNothing);
+    expect(onDragStartedCalled, isFalse);
+    // Long press draggable should be showing.
+    await tester.pump(const Duration(seconds: 1));
+    expect(find.text('Source'), findsOneWidget);
+    expect(find.text('Dragging'), findsOneWidget);
+    expect(onDragStartedCalled, isTrue);
+  });
+
+  testWidgets('Default long press delay for LongPressDraggable', (WidgetTester tester) async {
+    bool onDragStartedCalled = false;
+    await tester.pumpWidget(MaterialApp(
+      home: LongPressDraggable<int>(
+        data: 1,
+        child: const Text('Source'),
+        feedback: const Text('Dragging'),
+        onDragStarted: () {
+          onDragStartedCalled = true;
+        },
+      ),
+    ));
+    expect(find.text('Source'), findsOneWidget);
+    expect(find.text('Dragging'), findsNothing);
+    expect(onDragStartedCalled, isFalse);
+    final Offset firstLocation = tester.getCenter(find.text('Source'));
+    await tester.startGesture(firstLocation, pointer: 7);
+    await tester.pump();
+    expect(find.text('Source'), findsOneWidget);
+    expect(find.text('Dragging'), findsNothing);
+    expect(onDragStartedCalled, isFalse);
+    // Halfway into the long press duration.
+    await tester.pump(const Duration(milliseconds: 250));
+    expect(find.text('Source'), findsOneWidget);
+    expect(find.text('Dragging'), findsNothing);
+    expect(onDragStartedCalled, isFalse);
+    // Long press draggable should be showing.
+    await tester.pump(const Duration(milliseconds: 250));
+    expect(find.text('Source'), findsOneWidget);
+    expect(find.text('Dragging'), findsOneWidget);
+    expect(onDragStartedCalled, isTrue);
+  });
+
   testWidgets('long-press draggable calls Haptic Feedback onStart', (WidgetTester tester) async {
     await _testLongPressDraggableHapticFeedback(tester: tester, hapticFeedbackOnStart: true, expectedHapticFeedbackCount: 1);
   });