Add scroll gestures and use them in Scrollable

This patch replaces the scroll gestures used by Scrollable with ones detected
by the ScrollGestureDetector.

packages/flutter/lib/gestures/recognizer.dart

@@ -9,6 +9,8 @@ import 'package:sky/base/pointer_router.dart';
 import 'package:sky/gestures/arena.dart';
 import 'package:sky/gestures/constants.dart';
 
+export 'package:sky/base/pointer_router.dart' show PointerRouter;
+
 abstract class GestureRecognizer extends GestureArenaMember {
   GestureRecognizer({ PointerRouter router }) : _router = router;
 
@@ -21,8 +23,8 @@ abstract class GestureRecognizer extends GestureArenaMember {
   void addPointer(sky.PointerEvent event);
 
   void handleEvent(sky.PointerEvent event);
-  void acceptGesture(int key);
-  void rejectGesture(int key);
+  void acceptGesture(int pointer) { }
+  void rejectGesture(int pointer) { }
   void didStopTrackingLastPointer();
 
   void resolve(GestureDisposition disposition) {
@@ -115,9 +117,6 @@ abstract class PrimaryPointerGestureRecognizer extends GestureRecognizer {
     assert(deadline == null);
   }
 
-  void acceptGesture(int pointer) {
-  }
-
   void rejectGesture(int pointer) {
     _stopTimer();
     if (pointer == primaryPointer)

packages/flutter/lib/gestures/scroll.dart

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:sky' as sky;
+
+import 'package:sky/gestures/arena.dart';
+import 'package:sky/gestures/recognizer.dart';
+import 'package:sky/gestures/constants.dart';
+
+enum ScrollState {
+  ready,
+  possible,
+  accepted
+}
+
+typedef void GestureScrollStartCallback(sky.Offset scrollDelta);
+typedef void GestureScrollUpdateCallback(sky.Offset scrollDelta);
+typedef void GestureScrollEndCallback();
+
+sky.Offset _getScrollOffset(sky.PointerEvent event) {
+  // Notice that we negate dy because scroll offsets go in the opposite direction.
+  return new sky.Offset(event.dx, -event.dy);
+}
+
+class ScrollGestureRecognizer extends GestureRecognizer {
+  ScrollGestureRecognizer({ PointerRouter router, this.onScrollStart, this.onScrollUpdate, this.onScrollEnd })
+    : super(router: router);
+
+  GestureScrollStartCallback onScrollStart;
+  GestureScrollUpdateCallback onScrollUpdate;
+  GestureScrollEndCallback onScrollEnd;
+
+  ScrollState state = ScrollState.ready;
+  sky.Offset pendingScrollOffset;
+
+  void addPointer(sky.PointerEvent event) {
+    startTrackingPointer(event.pointer);
+    if (state == ScrollState.ready) {
+      state = ScrollState.possible;
+      pendingScrollOffset = sky.Offset.zero;
+    }
+  }
+
+  void handleEvent(sky.PointerEvent event) {
+    assert(state != ScrollState.ready);
+    if (event.type == 'pointermove') {
+      sky.Offset offset = _getScrollOffset(event);
+      if (state == ScrollState.accepted) {
+        onScrollUpdate(offset);
+      } else {
+        pendingScrollOffset += offset;
+        if (pendingScrollOffset.distance > kTouchSlop)
+          resolve(GestureDisposition.accepted);
+      }
+    }
+    stopTrackingIfPointerNoLongerDown(event);
+  }
+
+  void acceptGesture(int pointer) {
+    if (state != ScrollState.accepted) {
+      state = ScrollState.accepted;
+      sky.Offset offset = pendingScrollOffset;
+      pendingScrollOffset = null;
+      onScrollStart(offset);
+    }
+  }
+
+  void didStopTrackingLastPointer() {
+     bool wasAccepted = (state == ScrollState.accepted);
+     state = ScrollState.ready;
+     if (wasAccepted)
+      onScrollEnd();
+  }
+
+}

packages/flutter/lib/gestures/show_press.dart

@@ -4,7 +4,6 @@
 
 import 'dart:sky' as sky;
 
-import 'package:sky/base/pointer_router.dart';
 import 'package:sky/gestures/arena.dart';
 import 'package:sky/gestures/constants.dart';
 import 'package:sky/gestures/recognizer.dart';

packages/flutter/lib/gestures/tap.dart

@@ -4,7 +4,6 @@
 
 import 'dart:sky' as sky;
 
-import 'package:sky/base/pointer_router.dart';
 import 'package:sky/gestures/arena.dart';
 import 'package:sky/gestures/recognizer.dart';
 

packages/flutter/lib/widgets/gesture_detector.dart

@@ -4,9 +4,9 @@
 
 import 'dart:sky' as sky;
 
-import 'package:sky/base/pointer_router.dart';
 import 'package:sky/gestures/long_press.dart';
 import 'package:sky/gestures/recognizer.dart';
+import 'package:sky/gestures/scroll.dart';
 import 'package:sky/gestures/show_press.dart';
 import 'package:sky/gestures/tap.dart';
 import 'package:sky/rendering/sky_binding.dart';
@@ -18,19 +18,28 @@ class GestureDetector extends StatefulComponent {
     this.child,
     this.onTap,
     this.onShowPress,
-    this.onLongPress
+    this.onLongPress,
+    this.onScrollStart,
+    this.onScrollUpdate,
+    this.onScrollEnd
   }) : super(key: key);
 
   Widget child;
   GestureTapListener onTap;
   GestureShowPressListener onShowPress;
   GestureLongPressListener onLongPress;
+  GestureScrollStartCallback onScrollStart;
+  GestureScrollUpdateCallback onScrollUpdate;
+  GestureScrollEndCallback onScrollEnd;
 
   void syncConstructorArguments(GestureDetector source) {
     child = source.child;
     onTap = source.onTap;
     onShowPress = source.onShowPress;
     onLongPress = source.onLongPress;
+    onScrollStart = source.onScrollStart;
+    onScrollUpdate = source.onScrollUpdate;
+    onScrollEnd = source.onScrollEnd;
     _syncGestureListeners();
   }
 
@@ -57,6 +66,13 @@ class GestureDetector extends StatefulComponent {
     return _longPress;
   }
 
+  ScrollGestureRecognizer _scroll;
+  ScrollGestureRecognizer _ensureScroll() {
+    if (_scroll == null)
+      _scroll = new ScrollGestureRecognizer(router: _router);
+    return _scroll;
+  }
+
   void didMount() {
     super.didMount();
     _syncGestureListeners();
@@ -67,12 +83,14 @@ class GestureDetector extends StatefulComponent {
     _tap = _ensureDisposed(_tap);
     _showPress = _ensureDisposed(_showPress);
     _longPress = _ensureDisposed(_longPress);
+    _scroll = _ensureDisposed(_scroll);
   }
 
   void _syncGestureListeners() {
     _syncTap();
     _syncShowPress();
     _syncLongPress();
+    _syncScroll();
   }
 
   void _syncTap() {
@@ -96,6 +114,17 @@ class GestureDetector extends StatefulComponent {
       _ensureLongPress().onLongPress = onLongPress;
   }
 
+  void _syncScroll() {
+    if (onScrollStart == null && onScrollUpdate == null && onScrollEnd == null) {
+      _scroll = _ensureDisposed(_scroll);
+    } else {
+      _ensureScroll()
+        ..onScrollStart = onScrollStart
+        ..onScrollUpdate = onScrollUpdate
+        ..onScrollEnd = onScrollEnd;
+    }
+  }
+
   GestureRecognizer _ensureDisposed(GestureRecognizer recognizer) {
     if (recognizer != null)
       recognizer.dispose();
@@ -109,6 +138,8 @@ class GestureDetector extends StatefulComponent {
       _showPress.addPointer(event);
     if (_longPress != null)
       _longPress.addPointer(event);
+    if (_scroll != null)
+      _scroll.addPointer(event);
     return EventDisposition.processed;
   }
 

packages/flutter/lib/widgets/scrollable.dart

@@ -8,8 +8,8 @@ import 'dart:sky' as sky;
 
 import 'package:newton/newton.dart';
 import 'package:sky/animation/animated_simulation.dart';
-import 'package:sky/animation/animation_performance.dart';
 import 'package:sky/animation/animated_value.dart';
+import 'package:sky/animation/animation_performance.dart';
 import 'package:sky/animation/curves.dart';
 import 'package:sky/animation/scroll_behavior.dart';
 import 'package:sky/gestures/constants.dart';
@@ -17,6 +17,7 @@ import 'package:sky/rendering/box.dart';
 import 'package:sky/rendering/viewport.dart';
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/framework.dart';
+import 'package:sky/widgets/gesture_detector.dart';
 import 'package:sky/widgets/mixed_viewport.dart';
 import 'package:sky/widgets/scrollable.dart';
 
@@ -83,15 +84,17 @@ abstract class Scrollable extends StatefulComponent {
   Widget buildContent();
 
   Widget build() {
-    return new Listener(
-      child: buildContent(),
-      onPointerDown: _handlePointerDown,
-      onPointerUp: _handlePointerUpOrCancel,
-      onPointerCancel: _handlePointerUpOrCancel,
-      onGestureFlingStart: _handleFlingStart,
-      onGestureFlingCancel: _handleFlingCancel,
-      onGestureScrollUpdate: _handleScrollUpdate,
-      onWheel: _handleWheel
+    return new GestureDetector(
+      onScrollStart: _handleScrollOffset,
+      onScrollUpdate: _handleScrollOffset,
+      onScrollEnd: _maybeSettleScrollOffset,
+      child: new Listener(
+        child: buildContent(),
+        onPointerDown: _handlePointerDown,
+        onGestureFlingStart: _handleFlingStart,
+        onGestureFlingCancel: _handleFlingCancel,
+        onWheel: _handleWheel
+      )
     );
   }
 
@@ -171,9 +174,8 @@ abstract class Scrollable extends StatefulComponent {
     return EventDisposition.processed;
   }
 
-  EventDisposition _handleScrollUpdate(sky.GestureEvent event) {
-    scrollBy(scrollDirection == ScrollDirection.horizontal ? event.dx : -event.dy);
-    return EventDisposition.processed;
+  void _handleScrollOffset(Offset offset) {
+    scrollBy(scrollDirection == ScrollDirection.horizontal ? offset.dx : offset.dy);
   }
 
   EventDisposition _handleFlingStart(sky.GestureEvent event) {
@@ -187,11 +189,6 @@ abstract class Scrollable extends StatefulComponent {
       settleScrollOffset();
   }
 
-  EventDisposition _handlePointerUpOrCancel(_) {
-    _maybeSettleScrollOffset();
-    return EventDisposition.processed;
-  }
-
   EventDisposition _handleFlingCancel(sky.GestureEvent event) {
     _maybeSettleScrollOffset();
     return EventDisposition.processed;

packages/unit/test/gestures/scroll_test.dart

+import 'dart:sky' as sky;
+
+import 'package:sky/base/pointer_router.dart';
+import 'package:sky/gestures/scroll.dart';
+import 'package:test/test.dart';
+
+import '../engine/mock_events.dart';
+
+TestPointerEvent down = new TestPointerEvent(
+  pointer: 5,
+  type: 'pointerdown',
+  x: 10.0,
+  y: 10.0
+);
+
+TestPointerEvent move1 = new TestPointerEvent(
+  pointer: 5,
+  type: 'pointermove',
+  x: 20.0,
+  y: 20.0,
+  dx: 10.0,
+  dy: 10.0
+);
+
+TestPointerEvent move2 = new TestPointerEvent(
+  pointer: 5,
+  type: 'pointermove',
+  x: 20.0,
+  y: 25.0,
+  dx: 0.0,
+  dy: 5.0
+);
+
+TestPointerEvent up = new TestPointerEvent(
+  pointer: 5,
+  type: 'pointerup',
+  x: 20.0,
+  y: 25.0
+);
+
+void main() {
+  test('Should recognize scroll', () {
+    PointerRouter router = new PointerRouter();
+    ScrollGestureRecognizer scroll = new ScrollGestureRecognizer(router: router);
+
+    sky.Offset startOffset;
+    scroll.onScrollStart = (sky.Offset offset) {
+      startOffset = offset;
+    };
+
+    sky.Offset updateOffset;
+    scroll.onScrollUpdate = (sky.Offset offset) {
+      updateOffset = offset;
+    };
+
+    bool didEndScroll = false;
+    scroll.onScrollEnd = () {
+      didEndScroll = true;
+    };
+
+    scroll.addPointer(down);
+    expect(startOffset, isNull);
+    expect(updateOffset, isNull);
+    expect(didEndScroll, isFalse);
+
+    router.handleEvent(down, null);
+    expect(startOffset, isNull);
+    expect(updateOffset, isNull);
+    expect(didEndScroll, isFalse);
+
+    router.handleEvent(move1, null);
+    expect(startOffset, new sky.Offset(10.0, -10.0));
+    startOffset = null;
+    expect(updateOffset, isNull);
+    expect(didEndScroll, isFalse);
+
+    router.handleEvent(move2, null);
+    expect(startOffset, isNull);
+    expect(updateOffset, new sky.Offset(0.0, -5.0));
+    updateOffset = null;
+    expect(didEndScroll, isFalse);
+
+    router.handleEvent(up, null);
+    expect(startOffset, isNull);
+    expect(updateOffset, isNull);
+    expect(didEndScroll, isTrue);
+    didEndScroll = false;
+
+    scroll.dispose();
+  });
+}

packages/unit/test/widget/widget_tester.dart

@@ -83,26 +83,39 @@ class WidgetTester {
     return box.localToGlobal(box.size.center(Point.origin));
   }
 
+  HitTestResult _hitTest(Point location) => SkyBinding.instance.hitTest(location);
+
+  EventDisposition _dispatchEvent(sky.Event event, HitTestResult result) {
+    return SkyBinding.instance.dispatchEvent(event, result);
+  }
+
   void tap(Widget widget) {
     Point location = getCenter(widget);
-    dispatchEvent(new TestPointerEvent(type: 'pointerdown', x: location.x, y: location.y), location);
-    dispatchEvent(new TestPointerEvent(type: 'pointerup', x: location.x, y: location.y), location);
+    HitTestResult result = _hitTest(location);
+    _dispatchEvent(new TestPointerEvent(type: 'pointerdown', x: location.x, y: location.y), result);
+    _dispatchEvent(new TestPointerEvent(type: 'pointerup', x: location.x, y: location.y), result);
   }
 
   void scroll(Widget widget, Offset offset) {
-    dispatchEvent(new TestGestureEvent(type: 'gesturescrollstart'), getCenter(widget));
-    dispatchEvent(new TestGestureEvent(
-      type: 'gesturescrollupdate',
-      dx: offset.dx,
-      dy: offset.dy), getCenter(widget));
-    // pointerup to trigger scroll settling in Scrollable<T>
-    dispatchEvent(new TestPointerEvent(
-      type: 'pointerup', down: false, primary: true), getCenter(widget));
+    Point startLocation = getCenter(widget);
+    HitTestResult result = _hitTest(startLocation);
+    _dispatchEvent(new TestPointerEvent(type: 'pointerdown', x: startLocation.x, y: startLocation.y), result);
+    Point endLocation = startLocation + offset;
+    _dispatchEvent(
+      new TestPointerEvent(
+        type: 'pointermove',
+        x: endLocation.x,
+        y: endLocation.y,
+        dx: offset.dx,
+        dy: offset.dy
+      ),
+      result
+    );
+    _dispatchEvent(new TestPointerEvent(type: 'pointerup', x: endLocation.x, y: endLocation.y), result);
   }
 
-  void dispatchEvent(sky.Event event, Point position) {
-    HitTestResult result = SkyBinding.instance.hitTest(position);
-    SkyBinding.instance.dispatchEvent(event, result);
+  void dispatchEvent(sky.Event event, Point location) {
+    _dispatchEvent(event, _hitTest(location));
   }
 
   void pumpFrame(WidgetBuilder builder, [double frameTimeMs = 0.0]) {