Introduce TapDownDetails and TapUpDetails (#4431)

We have these details objects for the same reason we now have drag details
objects: future extensibility.

dev/manual_tests/overlay_geometry.dart

@@ -108,7 +108,7 @@ class CardBuilder extends LazyBlockDelegate {
     CardModel cardModel = cardModels[index];
     return new GestureDetector(
       key: cardModel.key,
-      onTapUp: (Point globalPosition) { onTapUp(cardModel.targetKey, globalPosition); },
+      onTapUp: (TapUpDetails details) { onTapUp(cardModel.targetKey, details.globalPosition); },
       child: new Card(
         key: cardModel.targetKey,
         color: cardModel.color,

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

@@ -56,7 +56,7 @@ class DragUpdateDetails {
   /// coordinates of [delta] and the other coordinate must be zero.
   DragUpdateDetails({
     this.delta: Offset.zero,
-    this.primaryDelta: 0.0
+    this.primaryDelta
   }) {
     assert(primaryDelta == null
         || (primaryDelta == delta.dx && delta.dy == 0.0)
@@ -90,7 +90,7 @@ class DragEndDetails {
   /// Creates details for a [GestureDragEndCallback].
   ///
   /// The [velocity] argument must not be null.
-  DragEndDetails({ this.velocity: Velocity.zero }) {
+  DragEndDetails({ this.velocity }) {
     assert(velocity != null);
   }
 
@@ -100,6 +100,9 @@ class DragEndDetails {
 
 /// Signature for when a pointer that was previously in contact with the screen
 /// and moving is no longer in contact with the screen.
+///
+/// The velocity at which the pointer was moving when it stopped contacting
+/// the screen is available in the `details`.
 typedef void GestureDragEndCallback(DragEndDetails details);
 
 /// Signature for when the pointer that previously triggered a

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

@@ -8,6 +8,7 @@ import 'dart:ui' show Point, Offset;
 import 'arena.dart';
 import 'binding.dart';
 import 'constants.dart';
+import 'drag.dart';
 import 'events.dart';
 import 'recognizer.dart';
 import 'velocity_tracker.dart';
@@ -17,12 +18,14 @@ typedef Drag GestureMultiDragStartCallback(Point position);
 
 /// Interface for receiving updates about drags from a [MultiDragGestureRecognizer].
 abstract class Drag {
-  /// The pointer has moved by the given offset.
+  /// The pointer has moved.
-  void move(Offset offset) { }
+  void update(DragUpdateDetails details) { }
 
-  /// The pointer is no longer in contact with the screen and was moving at a
+  /// The pointer is no longer in contact with the screen.
-  /// given velocity when it stopped contacting the screen.
+  ///
-  void end(Velocity velocity) { }
+  /// The velocity at which the pointer was moving when it stopped contacting
+  /// the screen is available in the `details`.
+  void end(DragEndDetails details) { }
 
   /// The input from the pointer is no longer directed towards this receiver.
   ///
@@ -76,7 +79,7 @@ abstract class MultiDragPointerState {
     _velocityTracker.addPosition(event.timeStamp, event.position);
     if (_client != null) {
       assert(pendingDelta == null);
-      _client.move(event.delta);
+      _client.update(new DragUpdateDetails(delta: event.delta));
     } else {
       assert(pendingDelta != null);
       _pendingDelta += event.delta;
@@ -113,7 +116,7 @@ abstract class MultiDragPointerState {
     assert(client != null);
     assert(pendingDelta != null);
     _client = client;
-    _client.move(pendingDelta);
+    _client.update(new DragUpdateDetails(delta: pendingDelta));
     _pendingDelta = null;
   }
 
@@ -121,7 +124,7 @@ abstract class MultiDragPointerState {
     assert(_arenaEntry != null);
     if (_client != null) {
       assert(pendingDelta == null);
-      _client.end(_velocityTracker.getVelocity());
+      _client.end(new DragEndDetails(velocity: _velocityTracker.getVelocity() ?? Velocity.zero));
       _client = null;
     } else {
       assert(pendingDelta != null);

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

@@ -11,6 +11,7 @@ import 'constants.dart';
 import 'events.dart';
 import 'pointer_router.dart';
 import 'recognizer.dart';
+import 'tap.dart';
 
 /// Signature for callback when the user has tapped the screen at the same
 /// location twice in quick succession.
@@ -18,11 +19,11 @@ typedef void GestureDoubleTapCallback();
 
 /// Signature used by [MultiTapGestureRecognizer] for when a pointer that might
 /// cause a tap has contacted the screen at a particular location.
-typedef void GestureMultiTapDownCallback(Point globalPosition, int pointer);
+typedef void GestureMultiTapDownCallback(int pointer, TapDownDetails details);
 
 /// Signature used by [MultiTapGestureRecognizer] for when a pointer that will
 /// trigger a tap has stopped contacting the screen at a particular location.
-typedef void GestureMultiTapUpCallback(Point globalPosition, int pointer);
+typedef void GestureMultiTapUpCallback(int pointer, TapUpDetails details);
 
 /// Signature used by [MultiTapGestureRecognizer] for when a tap has occurred.
 typedef void GestureMultiTapCallback(int pointer);
@@ -358,7 +359,7 @@ class MultiTapGestureRecognizer extends GestureRecognizer {
       longTapDelay: longTapDelay
     );
     if (onTapDown != null)
-      onTapDown(event.position, event.pointer);
+      onTapDown(event.pointer, new TapDownDetails(globalPosition: event.position));
   }
 
   @override
@@ -379,7 +380,7 @@ class MultiTapGestureRecognizer extends GestureRecognizer {
     _gestureMap.remove(pointer);
     if (resolution == _TapResolution.tap) {
       if (onTapUp != null)
-        onTapUp(globalPosition, pointer);
+        onTapUp(pointer, new TapUpDetails(globalPosition: globalPosition));
       if (onTap != null)
         onTap(pointer);
     } else {
@@ -391,7 +392,7 @@ class MultiTapGestureRecognizer extends GestureRecognizer {
   void _handleLongTap(int pointer, Point lastPosition) {
     assert(_gestureMap.containsKey(pointer));
     if (onLongTapDown != null)
-      onLongTapDown(lastPosition, pointer);
+      onLongTapDown(pointer, new TapDownDetails(globalPosition: lastPosition));
   }
 
   @override

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

@@ -7,13 +7,45 @@ import 'constants.dart';
 import 'events.dart';
 import 'recognizer.dart';
 
-/// Signature for when a pointer that might cause a tap has contacted the screen
+/// Details for [GestureTapDownCallback], such as position.
-/// at a particular location.
+class TapDownDetails {
-typedef void GestureTapDownCallback(Point globalPosition);
+  /// Creates details for a [GestureTapDownCallback].
+  ///
+  /// The [globalPosition] argument must not be null.
+  TapDownDetails({ this.globalPosition: Point.origin }) {
+    assert(globalPosition != null);
+  }
+
+  /// The global position at which the pointer contacted the screen.
+  final Point globalPosition;
+}
+
+/// Signature for when a pointer that might cause a tap has contacted the
+/// screen.
+///
+/// The position at which the pointer contacted the screen is available in the
+/// `details`.
+typedef void GestureTapDownCallback(TapDownDetails details);
+
+/// Details for [GestureTapUpCallback], such as position.
+class TapUpDetails {
+  /// Creates details for a [GestureTapUpCallback].
+  ///
+  /// The [globalPosition] argument must not be null.
+  TapUpDetails({ this.globalPosition: Point.origin }) {
+    assert(globalPosition != null);
+  }
+
+  /// The global position at which the pointer contacted the screen.
+  final Point globalPosition;
+}
 
 /// Signature for when a pointer that will trigger a tap has stopped contacting
-/// the screen at a particular location.
+/// the screen.
-typedef void GestureTapUpCallback(Point globalPosition);
+///
+/// The position at which the pointer stopped contacting the screen is available
+/// in the `details`.
+typedef void GestureTapUpCallback(TapUpDetails details);
 
 /// Signature for when a tap has occurred.
 typedef void GestureTapCallback();
@@ -102,7 +134,7 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
   void _checkDown() {
     if (!_sentTapDown) {
       if (onTapDown != null)
-        onTapDown(initialPosition);
+        onTapDown(new TapDownDetails(globalPosition: initialPosition));
       _sentTapDown = true;
     }
   }
@@ -111,7 +143,7 @@ class TapGestureRecognizer extends PrimaryPointerGestureRecognizer {
     if (_wonArena && _finalPosition != null) {
       resolve(GestureDisposition.accepted);
       if (onTapUp != null)
-        onTapUp(_finalPosition);
+        onTapUp(new TapUpDetails(globalPosition: _finalPosition));
       if (onTap != null)
         onTap();
       _reset();

packages/flutter/lib/src/material/ink_well.dart

@@ -127,14 +127,14 @@ class _InkResponseState<T extends InkResponse> extends State<T> {
       config.onHighlightChanged(value);
   }
 
-  void _handleTapDown(Point position) {
+  void _handleTapDown(TapDownDetails details) {
     RenderBox referenceBox = context.findRenderObject();
     assert(Material.of(context) != null);
     InkSplash splash;
     RectCallback rectCallback = config.getRectCallback(referenceBox);
     splash = Material.of(context).splashAt(
       referenceBox: referenceBox,
-      position: referenceBox.globalToLocal(position),
+      position: referenceBox.globalToLocal(details.globalPosition),
       color: Theme.of(context).splashColor,
       containedInkWell: config.containedInkWell,
       rectCallback: config.containedInkWell ? rectCallback : null,

packages/flutter/lib/src/material/toggleable.dart

@@ -213,9 +213,9 @@ abstract class RenderToggleable extends RenderConstrainedBox implements Semantic
     }
   }
 
-  void _handleTapDown(Point globalPosition) {
+  void _handleTapDown(TapDownDetails details) {
     if (isInteractive) {
-      _downPosition = globalToLocal(globalPosition);
+      _downPosition = globalToLocal(details.globalPosition);
       _reactionController.forward();
     }
   }
@@ -225,7 +225,7 @@ abstract class RenderToggleable extends RenderConstrainedBox implements Semantic
       onChanged(!_value);
   }
 
-  void _handleTapUp(Point globalPosition) {
+  void _handleTapUp(TapUpDetails details) {
     _downPosition = null;
     if (isInteractive)
       _reactionController.reverse();

packages/flutter/lib/src/rendering/editable_line.dart

@@ -217,8 +217,8 @@ class RenderEditableLine extends RenderBox {
 
   Point _lastTapDownPosition;
   Point _longPressPosition;
-  void _handleTapDown(Point globalPosition) {
+  void _handleTapDown(TapDownDetails details) {
-    _lastTapDownPosition = globalPosition + -paintOffset;
+    _lastTapDownPosition = details.globalPosition + -paintOffset;
   }
 
   void _handleTap() {

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

@@ -416,7 +416,7 @@ class _DragAvatar<T> extends Drag {
     _entry = new OverlayEntry(builder: _build);
     overlay.insert(_entry);
     _position = initialPosition;
-    update(initialPosition);
+    updateDrag(initialPosition);
   }
 
   final T data;
@@ -433,22 +433,22 @@ class _DragAvatar<T> extends Drag {
 
   // Drag API
   @override
-  void move(Offset offset) {
+  void update(DragUpdateDetails details) {
-    _position += offset;
+    _position += details.delta;
-    update(_position);
+    updateDrag(_position);
   }
 
   @override
-  void end(Velocity velocity) {
+  void end(DragEndDetails details) {
-    finish(_DragEndKind.dropped, velocity);
+    finishDrag(_DragEndKind.dropped, details.velocity);
   }
 
   @override
   void cancel() {
-    finish(_DragEndKind.canceled);
+    finishDrag(_DragEndKind.canceled);
   }
 
-  void update(Point globalPosition) {
+  void updateDrag(Point globalPosition) {
     _lastOffset = globalPosition - dragStartPoint;
     _entry.markNeedsBuild();
     HitTestResult result = new HitTestResult();
@@ -505,7 +505,7 @@ class _DragAvatar<T> extends Drag {
     _enteredTargets.clear();
   }
 
-  void finish(_DragEndKind endKind, [Velocity velocity]) {
+  void finishDrag(_DragEndKind endKind, [Velocity velocity]) {
     bool wasAccepted = false;
     if (endKind == _DragEndKind.dropped && _activeTarget != null) {
       _activeTarget.didDrop(data);

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

@@ -26,6 +26,8 @@ export 'package:flutter/gestures.dart' show
   GestureScaleStartCallback,
   GestureScaleUpdateCallback,
   GestureScaleEndCallback,
+  TapDownDetails,
+  TapUpDetails,
   Velocity;
 
 /// Signature for creating gesture recognizers.
@@ -479,9 +481,9 @@ class _GestureSemantics extends SingleChildRenderObjectWidget {
     TapGestureRecognizer recognizer = owner._recognizers[TapGestureRecognizer];
     assert(recognizer != null);
     if (recognizer.onTapDown != null)
-      recognizer.onTapDown(Point.origin);
+      recognizer.onTapDown(new TapDownDetails());
     if (recognizer.onTapUp != null)
-      recognizer.onTapUp(Point.origin);
+      recognizer.onTapUp(new TapUpDetails());
     if (recognizer.onTap != null)
       recognizer.onTap();
   }

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

@@ -28,7 +28,7 @@ class ModalBarrier extends StatelessWidget {
     return new Semantics(
       container: true,
       child: new GestureDetector(
-        onTapDown: (Point position) {
+        onTapDown: (TapDownDetails details) {
           if (dismissable)
             Navigator.pop(context);
         },