Add support for pointer hover (#6884)

bin/internal/engine.version

-ce8b187914f599e8e579fab829671fb2f07064b7
+d1bc4c4850ee155430b3ff66609a225364048257

examples/layers/raw/touch_input.dart

@@ -79,15 +79,15 @@ void beginFrame(Duration timeStamp) {
 void handlePointerDataPacket(ui.PointerDataPacket packet) {
   // The pointer packet contains a number of pointer movements, which we iterate
   // through and process.
-  for (ui.PointerData pointer in packet.pointers) {
-    if (pointer.change == ui.PointerChange.down) {
+  for (ui.PointerData datum in packet.data) {
+    if (datum.change == ui.PointerChange.down) {
       // If the pointer went down, we change the color of the circle to blue.
       color = const ui.Color(0xFF0000FF);
       // Rather than calling paint() synchronously, we ask the engine to
       // schedule a frame. The engine will call onBeginFrame when it is actually
       // time to produce the frame.
       ui.window.scheduleFrame();
-    } else if (pointer.change == ui.PointerChange.up) {
+    } else if (datum.change == ui.PointerChange.up) {
       // Similarly, if the pointer went up, we change the color of the circle to
       // green and schedule a frame. It's harmless to call scheduleFrame many
       // times because the engine will ignore redundant requests up until the

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

@@ -29,7 +29,7 @@ abstract class GestureBinding extends BindingBase implements HitTestable, HitTes
   static GestureBinding _instance;
 
   void _handlePointerDataPacket(ui.PointerDataPacket packet) {
-    _pendingPointerEvents.addAll(PointerEventConverter.expand(packet.pointers, ui.window.devicePixelRatio));
+    _pendingPointerEvents.addAll(PointerEventConverter.expand(packet.data, ui.window.devicePixelRatio));
     _flushPointerEventQueue();
   }
 

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

@@ -36,6 +36,13 @@ class PointerEventConverter {
   // Map from platform pointer identifiers to PointerEvent pointer identifiers.
   static Map<int, _PointerState> _pointers = <int, _PointerState>{};
 
+  static _PointerState _ensureStateForPointer(ui.PointerData datum, Point position) {
+    return _pointers.putIfAbsent(
+      datum.device,
+      () => new _PointerState(position)
+    );
+  }
+
   /// Expand the given packet of pointer data into a sequence of framework pointer events.
   static Iterable<PointerEvent> expand(Iterable<ui.PointerData> data, double devicePixelRatio) sync* {
     for (ui.PointerData datum in data) {
@@ -43,19 +50,14 @@ class PointerEventConverter {
       final Duration timeStamp = datum.timeStamp;
       final PointerDeviceKind kind = datum.kind;
       switch (datum.change) {
-        case ui.PointerChange.down:
-          assert(!_pointers.containsKey(datum.pointer));
-          _PointerState state = _pointers.putIfAbsent(
-            datum.pointer,
-            () => new _PointerState(position)
-          );
+        case ui.PointerChange.add:
+          assert(!_pointers.containsKey(datum.device));
+          _PointerState state = _ensureStateForPointer(datum, position);
           assert(state.lastPosition == position);
-          state.startNewPointer();
-          state.setDown();
           yield new PointerAddedEvent(
             timeStamp: timeStamp,
-            pointer: state.pointer,
             kind: kind,
+            device: datum.device,
             position: position,
             obscured: datum.obscured,
             pressureMin: datum.pressureMin,
@@ -67,10 +69,108 @@ class PointerEventConverter {
             orientation: datum.orientation,
             tilt: datum.tilt
           );
+          break;
+        case ui.PointerChange.hover:
+          final bool alreadyAdded = _pointers.containsKey(datum.device);
+          _PointerState state = _ensureStateForPointer(datum, position);
+          assert(!state.down);
+          if (!alreadyAdded) {
+            assert(state.lastPosition == position);
+            yield new PointerAddedEvent(
+              timeStamp: timeStamp,
+              kind: kind,
+              device: datum.device,
+              position: position,
+              obscured: datum.obscured,
+              pressureMin: datum.pressureMin,
+              pressureMax: datum.pressureMax,
+              distance: datum.distance,
+              distanceMax: datum.distanceMax,
+              radiusMin: datum.radiusMin,
+              radiusMax: datum.radiusMax,
+              orientation: datum.orientation,
+              tilt: datum.tilt
+            );
+          }
+          Offset offset = position - state.lastPosition;
+          state.lastPosition = position;
+          yield new PointerHoverEvent(
+            timeStamp: timeStamp,
+            kind: kind,
+            device: datum.device,
+            position: position,
+            delta: offset,
+            buttons: datum.buttons,
+            obscured: datum.obscured,
+            pressureMin: datum.pressureMin,
+            pressureMax: datum.pressureMax,
+            distance: datum.distance,
+            distanceMax: datum.distanceMax,
+            radiusMajor: datum.radiusMajor,
+            radiusMinor: datum.radiusMajor,
+            radiusMin: datum.radiusMin,
+            radiusMax: datum.radiusMax,
+            orientation: datum.orientation,
+            tilt: datum.tilt
+          );
+          state.lastPosition = position;
+          break;
+        case ui.PointerChange.down:
+          final bool alreadyAdded = _pointers.containsKey(datum.device);
+          _PointerState state = _ensureStateForPointer(datum, position);
+          assert(!state.down);
+          if (!alreadyAdded) {
+            assert(state.lastPosition == position);
+            yield new PointerAddedEvent(
+              timeStamp: timeStamp,
+              kind: kind,
+              device: datum.device,
+              position: position,
+              obscured: datum.obscured,
+              pressureMin: datum.pressureMin,
+              pressureMax: datum.pressureMax,
+              distance: datum.distance,
+              distanceMax: datum.distanceMax,
+              radiusMin: datum.radiusMin,
+              radiusMax: datum.radiusMax,
+              orientation: datum.orientation,
+              tilt: datum.tilt
+            );
+          }
+          if (state.lastPosition != position) {
+            // Not all sources of pointer packets respect the invariant that
+            // they hover the pointer to the down location before sending the
+            // down event. We restore the invariant here for our clients.
+            Offset offset = position - state.lastPosition;
+            state.lastPosition = position;
+            yield new PointerHoverEvent(
+              timeStamp: timeStamp,
+              kind: kind,
+              device: datum.device,
+              position: position,
+              delta: offset,
+              buttons: datum.buttons,
+              obscured: datum.obscured,
+              pressureMin: datum.pressureMin,
+              pressureMax: datum.pressureMax,
+              distance: datum.distance,
+              distanceMax: datum.distanceMax,
+              radiusMajor: datum.radiusMajor,
+              radiusMinor: datum.radiusMajor,
+              radiusMin: datum.radiusMin,
+              radiusMax: datum.radiusMax,
+              orientation: datum.orientation,
+              tilt: datum.tilt
+            );
+            state.lastPosition = position;
+          }
+          state.startNewPointer();
+          state.setDown();
           yield new PointerDownEvent(
             timeStamp: timeStamp,
             pointer: state.pointer,
             kind: kind,
+            device: datum.device,
             position: position,
             buttons: datum.buttons,
             obscured: datum.obscured,
@@ -90,8 +190,8 @@ class PointerEventConverter {
           // If the service starts supporting hover pointers, then it must also
           // start sending us ADDED and REMOVED data points.
           // See also: https://github.com/flutter/flutter/issues/720
-          assert(_pointers.containsKey(datum.pointer));
-          _PointerState state = _pointers[datum.pointer];
+          assert(_pointers.containsKey(datum.device));
+          _PointerState state = _pointers[datum.device];
           assert(state.down);
           Offset offset = position - state.lastPosition;
           state.lastPosition = position;
@@ -99,15 +199,14 @@ class PointerEventConverter {
             timeStamp: timeStamp,
             pointer: state.pointer,
             kind: kind,
+            device: datum.device,
             position: position,
             delta: offset,
-            down: state.down,
             buttons: datum.buttons,
             obscured: datum.obscured,
             pressure: datum.pressure,
             pressureMin: datum.pressureMin,
             pressureMax: datum.pressureMax,
-            distance: datum.distance,
             distanceMax: datum.distanceMax,
             radiusMajor: datum.radiusMajor,
             radiusMinor: datum.radiusMajor,
@@ -119,8 +218,8 @@ class PointerEventConverter {
           break;
         case ui.PointerChange.up:
         case ui.PointerChange.cancel:
-          assert(_pointers.containsKey(datum.pointer));
-          _PointerState state = _pointers[datum.pointer];
+          assert(_pointers.containsKey(datum.device));
+          _PointerState state = _pointers[datum.device];
           assert(state.down);
           if (position != state.lastPosition) {
             // Not all sources of pointer packets respect the invariant that
@@ -134,15 +233,14 @@ class PointerEventConverter {
               timeStamp: timeStamp,
               pointer: state.pointer,
               kind: kind,
+              device: datum.device,
               position: position,
               delta: offset,
-              down: state.down,
               buttons: datum.buttons,
               obscured: datum.obscured,
               pressure: datum.pressure,
               pressureMin: datum.pressureMin,
               pressureMax: datum.pressureMax,
-              distance: datum.distance,
               distanceMax: datum.distanceMax,
               radiusMajor: datum.radiusMajor,
               radiusMinor: datum.radiusMajor,
@@ -160,6 +258,7 @@ class PointerEventConverter {
               timeStamp: timeStamp,
               pointer: state.pointer,
               kind: kind,
+              device: datum.device,
               position: position,
               buttons: datum.buttons,
               obscured: datum.obscured,
@@ -176,6 +275,7 @@ class PointerEventConverter {
               timeStamp: timeStamp,
               pointer: state.pointer,
               kind: kind,
+              device: datum.device,
               position: position,
               buttons: datum.buttons,
               obscured: datum.obscured,
@@ -189,10 +289,13 @@ class PointerEventConverter {
               tilt: datum.tilt
             );
           }
+          _pointers.remove(datum.device);
+          break;
+        case ui.PointerChange.remove:
           yield new PointerRemovedEvent(
             timeStamp: timeStamp,
-            pointer: state.pointer,
             kind: kind,
+            device: datum.device,
             obscured: datum.obscured,
             pressureMin: datum.pressureMin,
             pressureMax: datum.pressureMax,
@@ -200,7 +303,6 @@ class PointerEventConverter {
             radiusMin: datum.radiusMin,
             radiusMax: datum.radiusMax
           );
-          _pointers.remove(datum.pointer);
           break;
         default:
           // TODO(ianh): once https://github.com/flutter/flutter/issues/720 is

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

@@ -76,6 +76,7 @@ abstract class PointerEvent {
     this.timeStamp: Duration.ZERO,
     this.pointer: 0,
     this.kind: PointerDeviceKind.touch,
+    this.device: 0,
     this.position: Point.origin,
     this.delta: Offset.zero,
     this.buttons: 0,
@@ -103,6 +104,9 @@ abstract class PointerEvent {
   /// The kind of input device for which the event was generated.
   final PointerDeviceKind kind;
 
+  /// Unique identifier for the pointing device, reused across interactions.
+  final int device;
+
   /// Coordinate of the position of the pointer, in logical pixels in the global
   /// coordinate space.
   final Point position;
@@ -219,6 +223,7 @@ abstract class PointerEvent {
              'timeStamp: $timeStamp, '
              'pointer: $pointer, '
              'kind: $kind, '
+             'device: $device, '
              'position: $position, '
              'delta: $delta, '
              'buttons: $buttons, '
@@ -250,8 +255,8 @@ class PointerAddedEvent extends PointerEvent {
   /// All of the argument must be non-null.
   const PointerAddedEvent({
     Duration timeStamp: Duration.ZERO,
-    int pointer: 0,
     PointerDeviceKind kind: PointerDeviceKind.touch,
+    int device: 0,
     Point position: Point.origin,
     bool obscured: false,
     double pressureMin: 1.0,
@@ -264,8 +269,8 @@ class PointerAddedEvent extends PointerEvent {
     double tilt: 0.0
   }) : super(
     timeStamp: timeStamp,
-    pointer: pointer,
     kind: kind,
+    device: device,
     position: position,
     obscured: obscured,
     pressureMin: pressureMin,
@@ -289,8 +294,8 @@ class PointerRemovedEvent extends PointerEvent {
   /// All of the argument must be non-null.
   const PointerRemovedEvent({
     Duration timeStamp: Duration.ZERO,
-    int pointer: 0,
     PointerDeviceKind kind: PointerDeviceKind.touch,
+    int device: 0,
     bool obscured: false,
     double pressureMin: 1.0,
     double pressureMax: 1.0,
@@ -299,8 +304,8 @@ class PointerRemovedEvent extends PointerEvent {
     double radiusMax: 0.0
   }) : super(
     timeStamp: timeStamp,
-    pointer: pointer,
     kind: kind,
+    device: device,
     position: null,
     obscured: obscured,
     pressureMin: pressureMin,
@@ -311,6 +316,57 @@ class PointerRemovedEvent extends PointerEvent {
   );
 }
 
+/// The pointer has moved with respect to the device while the pointer is not
+/// in contact with the device.
+///
+/// See also:
+///
+///  * [PointerMoveEvent], which reports movement while the pointer is in
+///    contact with the device.
+class PointerHoverEvent extends PointerEvent {
+  /// Creates a pointer hover event.
+  ///
+  /// All of the argument must be non-null.
+  const PointerHoverEvent({
+    Duration timeStamp: Duration.ZERO,
+    PointerDeviceKind kind: PointerDeviceKind.touch,
+    int device: 0,
+    Point position: Point.origin,
+    Offset delta: Offset.zero,
+    int buttons: 0,
+    bool obscured: false,
+    double pressureMin: 1.0,
+    double pressureMax: 1.0,
+    double distance: 0.0,
+    double distanceMax: 0.0,
+    double radiusMajor: 0.0,
+    double radiusMinor: 0.0,
+    double radiusMin: 0.0,
+    double radiusMax: 0.0,
+    double orientation: 0.0,
+    double tilt: 0.0
+  }) : super(
+    timeStamp: timeStamp,
+    kind: kind,
+    device: device,
+    position: position,
+    delta: delta,
+    buttons: buttons,
+    down: false,
+    obscured: obscured,
+    pressureMin: pressureMin,
+    pressureMax: pressureMax,
+    distance: distance,
+    distanceMax: distanceMax,
+    radiusMajor: radiusMajor,
+    radiusMinor: radiusMinor,
+    radiusMin: radiusMin,
+    radiusMax: radiusMax,
+    orientation: orientation,
+    tilt: tilt
+  );
+}
+
 /// The pointer has made contact with the device.
 class PointerDownEvent extends PointerEvent {
   /// Creates a pointer down event.
@@ -320,6 +376,7 @@ class PointerDownEvent extends PointerEvent {
     Duration timeStamp: Duration.ZERO,
     int pointer: 0,
     PointerDeviceKind kind: PointerDeviceKind.touch,
+    int device: 0,
     Point position: Point.origin,
     int buttons: 0,
     bool obscured: false,
@@ -337,6 +394,7 @@ class PointerDownEvent extends PointerEvent {
     timeStamp: timeStamp,
     pointer: pointer,
     kind: kind,
+    device: device,
     position: position,
     buttons: buttons,
     down: true,
@@ -355,7 +413,13 @@ class PointerDownEvent extends PointerEvent {
   );
 }
 
-/// The pointer has moved with respect to the device.
+/// The pointer has moved with respect to the device while the pointer is in
+/// contact with the device.
+///
+/// See also:
+///
+///  * [PointerHoverEvent], which reports movement while the pointer is not in
+///    contact with the device.
 class PointerMoveEvent extends PointerEvent {
   /// Creates a pointer move event.
   ///
@@ -364,15 +428,14 @@ class PointerMoveEvent extends PointerEvent {
     Duration timeStamp: Duration.ZERO,
     int pointer: 0,
     PointerDeviceKind kind: PointerDeviceKind.touch,
+    int device: 0,
     Point position: Point.origin,
     Offset delta: Offset.zero,
     int buttons: 0,
-    bool down: false,
     bool obscured: false,
     double pressure: 1.0,
     double pressureMin: 1.0,
     double pressureMax: 1.0,
-    double distance: 0.0,
     double distanceMax: 0.0,
     double radiusMajor: 0.0,
     double radiusMinor: 0.0,
@@ -384,15 +447,16 @@ class PointerMoveEvent extends PointerEvent {
     timeStamp: timeStamp,
     pointer: pointer,
     kind: kind,
+    device: device,
     position: position,
     delta: delta,
     buttons: buttons,
-    down: down,
+    down: true,
     obscured: obscured,
     pressure: pressure,
     pressureMin: pressureMin,
     pressureMax: pressureMax,
-    distance: distance,
+    distance: 0.0,
     distanceMax: distanceMax,
     radiusMajor: radiusMajor,
     radiusMinor: radiusMinor,
@@ -412,6 +476,7 @@ class PointerUpEvent extends PointerEvent {
     Duration timeStamp: Duration.ZERO,
     int pointer: 0,
     PointerDeviceKind kind: PointerDeviceKind.touch,
+    int device: 0,
     Point position: Point.origin,
     int buttons: 0,
     bool obscured: false,
@@ -427,8 +492,10 @@ class PointerUpEvent extends PointerEvent {
     timeStamp: timeStamp,
     pointer: pointer,
     kind: kind,
+    device: device,
     position: position,
     buttons: buttons,
+    down: false,
     obscured: obscured,
     pressureMin: pressureMin,
     pressureMax: pressureMax,
@@ -450,6 +517,7 @@ class PointerCancelEvent extends PointerEvent {
     Duration timeStamp: Duration.ZERO,
     int pointer: 0,
     PointerDeviceKind kind: PointerDeviceKind.touch,
+    int device: 0,
     Point position: Point.origin,
     int buttons: 0,
     bool obscured: false,
@@ -465,8 +533,10 @@ class PointerCancelEvent extends PointerEvent {
     timeStamp: timeStamp,
     pointer: pointer,
     kind: kind,
+    device: device,
     position: position,
     buttons: buttons,
+    down: false,
     obscured: obscured,
     pressureMin: pressureMin,
     pressureMax: pressureMax,

packages/flutter/test/gestures/gesture_binding_test.dart

@@ -34,7 +34,7 @@ void main() {
 
   test('Pointer tap events', () {
     ui.PointerDataPacket packet = new ui.PointerDataPacket(
-      pointers: <ui.PointerData>[
+      data: <ui.PointerData>[
         new ui.PointerData(change: ui.PointerChange.down),
         new ui.PointerData(change: ui.PointerChange.up),
       ]
@@ -51,7 +51,7 @@ void main() {
 
   test('Pointer move events', () {
     ui.PointerDataPacket packet = new ui.PointerDataPacket(
-      pointers: <ui.PointerData>[
+      data: <ui.PointerData>[
         new ui.PointerData(change: ui.PointerChange.down),
         new ui.PointerData(change: ui.PointerChange.move),
         new ui.PointerData(change: ui.PointerChange.up),
@@ -70,7 +70,7 @@ void main() {
 
   test('Synthetic move events', () {
     ui.PointerDataPacket packet = new ui.PointerDataPacket(
-      pointers: <ui.PointerData>[
+      data: <ui.PointerData>[
         new ui.PointerData(
           change: ui.PointerChange.down,
           physicalX: 1.0,
@@ -97,7 +97,7 @@ void main() {
 
   test('Pointer cancel events', () {
     ui.PointerDataPacket packet = new ui.PointerDataPacket(
-      pointers: <ui.PointerData>[
+      data: <ui.PointerData>[
         new ui.PointerData(change: ui.PointerChange.down),
         new ui.PointerData(change: ui.PointerChange.cancel),
       ]
@@ -114,7 +114,7 @@ void main() {
 
   test('Can cancel pointers', () {
     ui.PointerDataPacket packet = new ui.PointerDataPacket(
-      pointers: <ui.PointerData>[
+      data: <ui.PointerData>[
         new ui.PointerData(change: ui.PointerChange.down),
         new ui.PointerData(change: ui.PointerChange.up),
       ]

packages/flutter_test/lib/src/test_pointer.dart

@@ -66,7 +66,6 @@ class TestPointer {
     return new PointerMoveEvent(
       timeStamp: timeStamp,
       pointer: pointer,
-      down: _isDown,
       position: newLocation,
       delta: delta
     );