Pass on original pointer event timestamps to drag events (#11988)

* Record original pointer event timestamp

* review

* review

* review

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

@@ -52,9 +52,15 @@ class DragStartDetails {
   /// Creates details for a [GestureDragStartCallback].
   ///
   /// The [globalPosition] argument must not be null.
-  DragStartDetails({ this.globalPosition: Offset.zero })
+  DragStartDetails({ this.sourceTimeStamp, this.globalPosition: Offset.zero })
     : assert(globalPosition != null);
 
+  /// Recorded timestamp of the source pointer event that triggered the drag
+  /// event.
+  ///
+  /// Could be null if triggered from proxied events such as accessibility.
+  final Duration sourceTimeStamp;
+
   /// The global position at which the pointer contacted the screen.
   ///
   /// Defaults to the origin if not specified in the constructor.
@@ -94,6 +100,7 @@ class DragUpdateDetails {
   ///
   /// The [globalPosition] argument must be provided and must not be null.
   DragUpdateDetails({
+    this.sourceTimeStamp,
     this.delta: Offset.zero,
     this.primaryDelta,
     @required this.globalPosition
@@ -102,6 +109,12 @@ class DragUpdateDetails {
            || (primaryDelta == delta.dx && delta.dy == 0.0)
            || (primaryDelta == delta.dy && delta.dx == 0.0));
 
+  /// Recorded timestamp of the source pointer event that triggered the drag
+  /// event.
+  ///
+  /// Could be null if triggered from proxied events such as accessibility.
+  final Duration sourceTimeStamp;
+
   /// The amount the pointer has moved since the previous update.
   ///
   /// If the [GestureDragUpdateCallback] is for a one-dimensional drag (e.g.,

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

@@ -101,6 +101,7 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
   _DragState _state = _DragState.ready;
   Offset _initialPosition;
   Offset _pendingDragOffset;
+  Duration _lastPendingEventTimestamp;
 
   bool _isFlingGesture(VelocityEstimate estimate);
   Offset _getDeltaForDetails(Offset delta);
@@ -117,6 +118,7 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
       _state = _DragState.possible;
       _initialPosition = event.position;
       _pendingDragOffset = Offset.zero;
+      _lastPendingEventTimestamp = event.timeStamp;
       if (onDown != null)
         invokeCallback<Null>('onDown', () => onDown(new DragDownDetails(globalPosition: _initialPosition))); // ignore: STRONG_MODE_INVALID_CAST_FUNCTION_EXPR, https://github.com/dart-lang/sdk/issues/27504
     } else if (_state == _DragState.accepted) {
@@ -139,6 +141,7 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
       if (_state == _DragState.accepted) {
         if (onUpdate != null) {
           invokeCallback<Null>('onUpdate', () => onUpdate(new DragUpdateDetails( // ignore: STRONG_MODE_INVALID_CAST_FUNCTION_EXPR, https://github.com/dart-lang/sdk/issues/27504
+            sourceTimeStamp: event.timeStamp,
             delta: _getDeltaForDetails(delta),
             primaryDelta: _getPrimaryValueFromOffset(delta),
             globalPosition: event.position,
@@ -146,6 +149,7 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
         }
       } else {
         _pendingDragOffset += delta;
+        _lastPendingEventTimestamp = event.timeStamp;
         if (_hasSufficientPendingDragDeltaToAccept)
           resolve(GestureDisposition.accepted);
       }
@@ -158,14 +162,18 @@ abstract class DragGestureRecognizer extends OneSequenceGestureRecognizer {
     if (_state != _DragState.accepted) {
       _state = _DragState.accepted;
       final Offset delta = _pendingDragOffset;
+      final Duration timestamp = _lastPendingEventTimestamp;
       _pendingDragOffset = Offset.zero;
+      _lastPendingEventTimestamp = null;
       if (onStart != null) {
         invokeCallback<Null>('onStart', () => onStart(new DragStartDetails( // ignore: STRONG_MODE_INVALID_CAST_FUNCTION_EXPR, https://github.com/dart-lang/sdk/issues/27504
+          sourceTimeStamp: timestamp,
           globalPosition: _initialPosition,
         )));
       }
       if (delta != Offset.zero && onUpdate != null) {
         invokeCallback<Null>('onUpdate', () => onUpdate(new DragUpdateDetails( // ignore: STRONG_MODE_INVALID_CAST_FUNCTION_EXPR, https://github.com/dart-lang/sdk/issues/27504
+          sourceTimeStamp: timestamp,
           delta: _getDeltaForDetails(delta),
           primaryDelta: _getPrimaryValueFromOffset(delta),
           globalPosition: _initialPosition,

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

@@ -45,6 +45,8 @@ abstract class MultiDragPointerState {
   Offset get pendingDelta => _pendingDelta;
   Offset _pendingDelta = Offset.zero;
 
+  Duration _lastPendingEventTimestamp;
+
   GestureArenaEntry _arenaEntry;
   void _setArenaEntry(GestureArenaEntry entry) {
     assert(_arenaEntry == null);
@@ -68,12 +70,14 @@ abstract class MultiDragPointerState {
       assert(pendingDelta == null);
       // Call client last to avoid reentrancy.
       _client.update(new DragUpdateDetails(
+        sourceTimeStamp: event.timeStamp,
         delta: event.delta,
         globalPosition: event.position,
       ));
     } else {
       assert(pendingDelta != null);
       _pendingDelta += event.delta;
+      _lastPendingEventTimestamp = event.timeStamp;
       checkForResolutionAfterMove();
     }
   }
@@ -101,6 +105,7 @@ abstract class MultiDragPointerState {
     assert(_client == null);
     assert(pendingDelta != null);
     _pendingDelta = null;
+    _lastPendingEventTimestamp = null;
     _arenaEntry = null;
   }
 
@@ -111,10 +116,12 @@ abstract class MultiDragPointerState {
     assert(pendingDelta != null);
     _client = client;
     final DragUpdateDetails details = new DragUpdateDetails(
+      sourceTimeStamp: _lastPendingEventTimestamp,
       delta: pendingDelta,
       globalPosition: initialPosition,
     );
     _pendingDelta = null;
+    _lastPendingEventTimestamp = null;
     // Call client last to avoid reentrancy.
     _client.update(details);
   }
@@ -131,6 +138,7 @@ abstract class MultiDragPointerState {
     } else {
       assert(pendingDelta != null);
       _pendingDelta = null;
+      _lastPendingEventTimestamp = null;
     }
   }
 
@@ -145,6 +153,7 @@ abstract class MultiDragPointerState {
     } else {
       assert(pendingDelta != null);
       _pendingDelta = null;
+      _lastPendingEventTimestamp = null;
     }
   }
 

packages/flutter/test/gestures/drag_test.dart

@@ -133,6 +133,37 @@ void main() {
     drag.dispose();
   });
 
+  testGesture('Should report original timestamps', (GestureTester tester) {
+    final HorizontalDragGestureRecognizer drag = new HorizontalDragGestureRecognizer();
+
+    Duration startTimestamp;
+    drag.onStart = (DragStartDetails details) {
+      startTimestamp = details.sourceTimeStamp;
+    };
+
+    Duration updatedTimestamp;
+    drag.onUpdate = (DragUpdateDetails details) {
+      updatedTimestamp = details.sourceTimeStamp;
+    };
+
+    final TestPointer pointer = new TestPointer(5);
+    final PointerDownEvent down = pointer.down(const Offset(10.0, 10.0), timeStamp: const Duration(milliseconds: 100));
+    drag.addPointer(down);
+    tester.closeArena(5);
+    expect(startTimestamp, isNull);
+
+    tester.route(down);
+    expect(startTimestamp, const Duration(milliseconds: 100));
+
+    tester.route(pointer.move(const Offset(20.0, 25.0), timeStamp: const Duration(milliseconds: 200)));
+    expect(updatedTimestamp, const Duration(milliseconds: 200));
+
+    tester.route(pointer.move(const Offset(20.0, 25.0), timeStamp: const Duration(milliseconds: 300)));
+    expect(updatedTimestamp, const Duration(milliseconds: 300));
+
+    drag.dispose();
+  });
+
   testGesture('Drag with multiple pointers', (GestureTester tester) {
     final HorizontalDragGestureRecognizer drag1 = new HorizontalDragGestureRecognizer();
     final VerticalDragGestureRecognizer drag2 = new VerticalDragGestureRecognizer();