Horizontal and Vertical Draggables

packages/flutter/lib/src/gestures/multidrag.dart

@@ -252,6 +252,61 @@ class ImmediateMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_Im
   }
 }
 
+
+class _HorizontalPointerState extends MultiDragPointerState {
+  _HorizontalPointerState(Point initialPosition) : super(initialPosition);
+
+  void checkForResolutionAfterMove() {
+    assert(pendingDelta != null);
+    if (pendingDelta.dx.abs() > kTouchSlop)
+      resolve(GestureDisposition.accepted);
+  }
+
+  void accepted(GestureMultiDragStartCallback starter) {
+    starter(initialPosition);
+  }
+}
+
+class HorizontalMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_HorizontalPointerState> {
+  HorizontalMultiDragGestureRecognizer({
+    PointerRouter pointerRouter,
+    GestureArena gestureArena,
+    GestureMultiDragStartCallback onStart
+  }) : super(pointerRouter: pointerRouter, gestureArena: gestureArena, onStart: onStart);
+
+  _HorizontalPointerState createNewPointerState(PointerDownEvent event) {
+    return new _HorizontalPointerState(event.position);
+  }
+}
+
+
+class _VerticalPointerState extends MultiDragPointerState {
+  _VerticalPointerState(Point initialPosition) : super(initialPosition);
+
+  void checkForResolutionAfterMove() {
+    assert(pendingDelta != null);
+    if (pendingDelta.dy.abs() > kTouchSlop)
+      resolve(GestureDisposition.accepted);
+  }
+
+  void accepted(GestureMultiDragStartCallback starter) {
+    starter(initialPosition);
+  }
+}
+
+class VerticalMultiDragGestureRecognizer extends MultiDragGestureRecognizer<_VerticalPointerState> {
+  VerticalMultiDragGestureRecognizer({
+    PointerRouter pointerRouter,
+    GestureArena gestureArena,
+    GestureMultiDragStartCallback onStart
+  }) : super(pointerRouter: pointerRouter, gestureArena: gestureArena, onStart: onStart);
+
+  _VerticalPointerState createNewPointerState(PointerDownEvent event) {
+    return new _VerticalPointerState(event.position);
+  }
+}
+
+
 class _DelayedPointerState extends MultiDragPointerState {
   _DelayedPointerState(Point initialPosition, Duration delay) : super(initialPosition) {
     assert(delay != null);

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

@@ -118,6 +118,70 @@ class Draggable<T> extends DraggableBase<T> {
   }
 }
 
+/// Makes its child draggable. When competing with other gestures,
+/// this will only start the drag horizontally.
+class HorizontalDraggable<T> extends DraggableBase<T> {
+  HorizontalDraggable({
+    Key key,
+    T data,
+    Widget child,
+    Widget childWhenDragging,
+    Widget feedback,
+    Offset feedbackOffset: Offset.zero,
+    DragAnchor dragAnchor: DragAnchor.child,
+    int maxSimultaneousDrags
+  }) : super(
+    key: key,
+    data: data,
+    child: child,
+    childWhenDragging: childWhenDragging,
+    feedback: feedback,
+    feedbackOffset: feedbackOffset,
+    dragAnchor: dragAnchor,
+    maxSimultaneousDrags: maxSimultaneousDrags
+  );
+
+  MultiDragGestureRecognizer createRecognizer(PointerRouter router, GestureArena arena, GestureMultiDragStartCallback starter) {
+    return new HorizontalMultiDragGestureRecognizer(
+      pointerRouter: router,
+      gestureArena: arena,
+      onStart: starter
+    );
+  }
+}
+
+/// Makes its child draggable. When competing with other gestures,
+/// this will only start the drag vertically.
+class VerticalDraggable<T> extends DraggableBase<T> {
+  VerticalDraggable({
+    Key key,
+    T data,
+    Widget child,
+    Widget childWhenDragging,
+    Widget feedback,
+    Offset feedbackOffset: Offset.zero,
+    DragAnchor dragAnchor: DragAnchor.child,
+    int maxSimultaneousDrags
+  }) : super(
+    key: key,
+    data: data,
+    child: child,
+    childWhenDragging: childWhenDragging,
+    feedback: feedback,
+    feedbackOffset: feedbackOffset,
+    dragAnchor: dragAnchor,
+    maxSimultaneousDrags: maxSimultaneousDrags
+  );
+
+  MultiDragGestureRecognizer createRecognizer(PointerRouter router, GestureArena arena, GestureMultiDragStartCallback starter) {
+    return new VerticalMultiDragGestureRecognizer(
+      pointerRouter: router,
+      gestureArena: arena,
+      onStart: starter
+    );
+  }
+}
+
 /// Makes its child draggable starting from long press.
 class LongPressDraggable<T> extends DraggableBase<T> {
   LongPressDraggable({

packages/flutter/test/widget/draggable_test.dart

@@ -338,6 +338,232 @@ void main() {
       tester.dispatchEvent(pointer.up(), firstLocation);
       tester.pump();
       expect(events, equals(<String>['drop']));
+    });
+  });
+
+  test('Drag and drop - horizontal and vertical draggables in vertical block', () {
+    testWidgets((WidgetTester tester) {
+      TestPointer pointer = new TestPointer(7);
+
+      List<String> events = <String>[];
+      Point firstLocation, secondLocation, thirdLocation;
+
+      tester.pumpWidget(new MaterialApp(
+        routes: <String, RouteBuilder>{
+          '/': (RouteArguments args) {
+            return new Block(
+              children: <Widget>[
+                new DragTarget(
+                  builder: (context, data, rejects) {
+                    return new Text('Target');
+                  },
+                  onAccept: (data) {
+                    events.add('drop $data');
+                  }
+                ),
+                new Container(height: 400.0),
+                new HorizontalDraggable(
+                  data: 1,
+                  child: new Text('H'),
+                  feedback: new Text('Dragging')
+                ),
+                new VerticalDraggable(
+                  data: 2,
+                  child: new Text('V'),
+                  feedback: new Text('Dragging')
+                ),
+                new Container(height: 500.0),
+                new Container(height: 500.0),
+                new Container(height: 500.0),
+                new Container(height: 500.0),
+              ]
+            );
+          },
+        }
+      ));
+
+      expect(events, isEmpty);
+      expect(tester.findText('Target'), isNotNull);
+      expect(tester.findText('H'), isNotNull);
+      expect(tester.findText('V'), isNotNull);
+
+      // vertical draggable drags vertically
+      expect(events, isEmpty);
+      firstLocation = tester.getCenter(tester.findText('V'));
+      secondLocation = tester.getCenter(tester.findText('Target'));
+      tester.dispatchEvent(pointer.down(firstLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(secondLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.up(), firstLocation);
+      tester.pump();
+      expect(events, equals(<String>['drop 2']));
+      expect(tester.getCenter(tester.findText('Target')).y, greaterThan(0.0));
+      events.clear();
+
+      // horizontal draggable drags horizontally
+      expect(events, isEmpty);
+      firstLocation = tester.getTopLeft(tester.findText('H'));
+      secondLocation = tester.getTopRight(tester.findText('H'));
+      thirdLocation = tester.getCenter(tester.findText('Target'));
+      tester.dispatchEvent(pointer.down(firstLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(secondLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(thirdLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.up(), firstLocation);
+      tester.pump();
+      expect(events, equals(<String>['drop 1']));
+      expect(tester.getCenter(tester.findText('Target')).y, greaterThan(0.0));
+      events.clear();
+
+      // vertical draggable drags horizontally when there's no competition
+      // from other gesture detectors
+      expect(events, isEmpty);
+      firstLocation = tester.getTopLeft(tester.findText('V'));
+      secondLocation = tester.getTopRight(tester.findText('V'));
+      thirdLocation = tester.getCenter(tester.findText('Target'));
+      tester.dispatchEvent(pointer.down(firstLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(secondLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(thirdLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.up(), firstLocation);
+      tester.pump();
+      expect(events, equals(<String>['drop 2']));
+      expect(tester.getCenter(tester.findText('Target')).y, greaterThan(0.0));
+      events.clear();
+
+      // horizontal draggable doesn't drag vertically when there is competition
+      // for vertical gestures
+      expect(events, isEmpty);
+      firstLocation = tester.getCenter(tester.findText('H'));
+      secondLocation = tester.getCenter(tester.findText('Target'));
+      tester.dispatchEvent(pointer.down(firstLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(secondLocation), firstLocation);
+      tester.pump(); // scrolls off screen!
+      tester.dispatchEvent(pointer.up(), firstLocation);
+      tester.pump();
+      expect(events, equals(<String>[]));
+      expect(tester.getCenter(tester.findText('Target')).y, lessThan(0.0));
+      events.clear();
+
+    });
+  });
+
+  test('Drag and drop - horizontal and vertical draggables in horizontal block', () {
+    testWidgets((WidgetTester tester) {
+      TestPointer pointer = new TestPointer(7);
+
+      List<String> events = <String>[];
+      Point firstLocation, secondLocation, thirdLocation;
+
+      tester.pumpWidget(new MaterialApp(
+        routes: <String, RouteBuilder>{
+          '/': (RouteArguments args) {
+            return new Block(
+              scrollDirection: Axis.horizontal,
+              children: <Widget>[
+                new DragTarget(
+                  builder: (context, data, rejects) {
+                    return new Text('Target');
+                  },
+                  onAccept: (data) {
+                    events.add('drop $data');
+                  }
+                ),
+                new Container(width: 400.0),
+                new HorizontalDraggable(
+                  data: 1,
+                  child: new Text('H'),
+                  feedback: new Text('Dragging')
+                ),
+                new VerticalDraggable(
+                  data: 2,
+                  child: new Text('V'),
+                  feedback: new Text('Dragging')
+                ),
+                new Container(width: 500.0),
+                new Container(width: 500.0),
+                new Container(width: 500.0),
+                new Container(width: 500.0),
+              ]
+            );
+          },
+        }
+      ));
+
+      expect(events, isEmpty);
+      expect(tester.findText('Target'), isNotNull);
+      expect(tester.findText('H'), isNotNull);
+      expect(tester.findText('V'), isNotNull);
+
+      // horizontal draggable drags horizontally
+      expect(events, isEmpty);
+      firstLocation = tester.getCenter(tester.findText('H'));
+      secondLocation = tester.getCenter(tester.findText('Target'));
+      tester.dispatchEvent(pointer.down(firstLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(secondLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.up(), firstLocation);
+      tester.pump();
+      expect(events, equals(<String>['drop 1']));
+      expect(tester.getCenter(tester.findText('Target')).x, greaterThan(0.0));
+      events.clear();
+
+      // vertical draggable drags vertically
+      expect(events, isEmpty);
+      firstLocation = tester.getTopLeft(tester.findText('V'));
+      secondLocation = tester.getBottomLeft(tester.findText('V'));
+      thirdLocation = tester.getCenter(tester.findText('Target'));
+      tester.dispatchEvent(pointer.down(firstLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(secondLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(thirdLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.up(), firstLocation);
+      tester.pump();
+      expect(events, equals(<String>['drop 2']));
+      expect(tester.getCenter(tester.findText('Target')).x, greaterThan(0.0));
+      events.clear();
+
+      // horizontal draggable drags vertically when there's no competition
+      // from other gesture detectors
+      expect(events, isEmpty);
+      firstLocation = tester.getTopLeft(tester.findText('H'));
+      secondLocation = tester.getBottomLeft(tester.findText('H'));
+      thirdLocation = tester.getCenter(tester.findText('Target'));
+      tester.dispatchEvent(pointer.down(firstLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(secondLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(thirdLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.up(), firstLocation);
+      tester.pump();
+      expect(events, equals(<String>['drop 1']));
+      expect(tester.getCenter(tester.findText('Target')).x, greaterThan(0.0));
+      events.clear();
+
+      // vertical draggable doesn't drag horizontally when there is competition
+      // for horizontal gestures
+      expect(events, isEmpty);
+      firstLocation = tester.getCenter(tester.findText('V'));
+      secondLocation = tester.getCenter(tester.findText('Target'));
+      tester.dispatchEvent(pointer.down(firstLocation), firstLocation);
+      tester.pump();
+      tester.dispatchEvent(pointer.move(secondLocation), firstLocation);
+      tester.pump(); // scrolls off screen!
+      tester.dispatchEvent(pointer.up(), firstLocation);
+      tester.pump();
+      expect(events, equals(<String>[]));
+      expect(tester.getCenter(tester.findText('Target')).x, lessThan(0.0));
+      events.clear();
 
     });
   });