Add support for hover pointer events (#3227)

These are implemented on macOS and Fuchsia.

content_handler/runtime_holder.cc

@@ -269,6 +269,25 @@ void RuntimeHolder::OnEvent(mozart::EventPtr event,
     pointer_data.physical_x = event->pointer_data->x;
     pointer_data.physical_y = event->pointer_data->y;
 
+    switch (pointer_data.change) {
+      case blink::PointerData::Change::kDown:
+        down_pointers_.insert(pointer_data.pointer);
+        break;
+      case blink::PointerData::Change::kCancel:
+      case blink::PointerData::Change::kUp:
+        down_pointers_.erase(pointer_data.pointer);
+        break;
+      case blink::PointerData::Change::kMove:
+        if (down_pointers_.count(pointer_data.pointer) == 0)
+          pointer_data.change = blink::PointerData::Change::kHover;
+        break;
+      case blink::PointerData::Change::kAdd:
+      case blink::PointerData::Change::kRemove:
+      case blink::PointerData::Change::kHover:
+        FTL_DCHECK(down_pointers_.count(pointer_data.pointer) == 0);
+        break;
+    }
+
     blink::PointerDataPacket packet(1);
     packet.SetPointerData(0, pointer_data);
     runtime_->DispatchPointerDataPacket(packet);

content_handler/runtime_holder.h

@@ -7,6 +7,8 @@
 
 #include <mx/channel.h>
 
+#include <unordered_set>
+
 #include "apps/modular/services/application/application_environment.fidl.h"
 #include "apps/modular/services/application/service_provider.fidl.h"
 #include "apps/mozart/services/input/input_connection.fidl.h"
@@ -89,6 +91,8 @@ class RuntimeHolder : public blink::RuntimeDelegate,
   mozart::ViewPropertiesPtr view_properties_;
   uint32_t scene_version_ = mozart::kSceneVersionNone;
 
+  unordered_set<int> down_pointers_;
+
   bool pending_invalidation_ = false;
   OnInvalidationCallback deferred_invalidation_callback_;
   bool is_ready_to_draw_ = false;

lib/ui/hooks.dart

@@ -94,14 +94,14 @@ PointerDataPacket _unpackPointerDataPacket(ByteData packet) {
   const int kBytesPerPointerData = _kPointerDataFieldCount * kStride;
   final int length = packet.lengthInBytes ~/ kBytesPerPointerData;
   assert(length * kBytesPerPointerData == packet.lengthInBytes);
-  List<PointerData> pointers = new List<PointerData>(length);
+  List<PointerData> data = new List<PointerData>(length);
   for (int i = 0; i < length; ++i) {
     int offset = i * _kPointerDataFieldCount;
-    pointers[i] = new PointerData(
+    data[i] = new PointerData(
       timeStamp: new Duration(microseconds: packet.getInt64(kStride * offset++, _kFakeHostEndian)),
-      pointer: packet.getInt64(kStride * offset++, _kFakeHostEndian),
       change: PointerChange.values[packet.getInt64(kStride * offset++, _kFakeHostEndian)],
       kind: PointerDeviceKind.values[packet.getInt64(kStride * offset++, _kFakeHostEndian)],
+      device: packet.getInt64(kStride * offset++, _kFakeHostEndian),
       physicalX: packet.getFloat64(kStride * offset++, _kFakeHostEndian),
       physicalY: packet.getFloat64(kStride * offset++, _kFakeHostEndian),
       buttons: packet.getInt64(kStride * offset++, _kFakeHostEndian),
@@ -120,5 +120,5 @@ PointerDataPacket _unpackPointerDataPacket(ByteData packet) {
     );
     assert(offset == (i + 1) * _kPointerDataFieldCount);
   }
-  return new PointerDataPacket(pointers: pointers);
+  return new PointerDataPacket(data: data);
 }

lib/ui/pointer.dart

@@ -21,10 +21,15 @@ enum PointerChange {
   /// detection range or might have been disconnected from the system entirely.
   remove,
 
+  /// The pointer has moved with respect to the device while not in contact with
+  /// the device.
+  hover,
+
   /// The pointer has made contact with the device.
   down,
 
-  /// The pointer has moved with respect to the device.
+  /// The pointer has moved with respect to the device while in contact with the
+  /// device.
   move,
 
   /// The pointer has stopped making contact with the device.
@@ -51,9 +56,9 @@ class PointerData {
   /// Creates an object that represents the state of a pointer.
   const PointerData({
     this.timeStamp: Duration.ZERO,
-    this.pointer: 0,
     this.change: PointerChange.cancel,
     this.kind: PointerDeviceKind.touch,
+    this.device: 0,
     this.physicalX: 0.0,
     this.physicalY: 0.0,
     this.buttons: 0,
@@ -74,14 +79,15 @@ class PointerData {
   /// Time of event dispatch, relative to an arbitrary timeline.
   final Duration timeStamp;
 
-  /// Unique identifier for the pointer, potentially reused.
-  final int pointer;
-
+  /// How the pointer has changed since the last report.
   final PointerChange change;
 
   /// 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;
+
   /// X coordinate of the position of the pointer, in physical pixels in the
   /// global coordinate space.
   final double physicalX;
@@ -188,9 +194,9 @@ class PointerData {
   String toStringFull() {
     return '$runtimeType('
              'timeStamp: $timeStamp, '
-             'pointer: $pointer, '
-             'change:: $change, '
+             'change: $change, '
              'kind: $kind, '
+             'device: $device, '
              'physicalX: $physicalX, '
              'physicalY: $physicalY, '
              'buttons: $buttons, '
@@ -212,10 +218,10 @@ class PointerData {
 /// A sequence of reports about the state of pointers.
 class PointerDataPacket {
   /// Creates a packet of pointer data reports.
-  const PointerDataPacket({ this.pointers: const <PointerData>[] });
+  const PointerDataPacket({ this.data: const <PointerData>[] });
 
   /// Data about the individual pointers in this packet.
   ///
   /// This list might contain multiple pieces of data about the same pointer.
-  final List<PointerData> pointers;
+  final List<PointerData> data;
 }

lib/ui/window/pointer_data.h

@@ -16,6 +16,7 @@ struct alignas(8) PointerData {
     kCancel,
     kAdd,
     kRemove,
+    kHover,
     kDown,
     kMove,
     kUp,
@@ -30,9 +31,9 @@ struct alignas(8) PointerData {
   };
 
   int64_t time_stamp;
-  int64_t pointer;
   Change change;
   DeviceKind kind;
+  int64_t device;
   double physical_x;
   double physical_y;
   int64_t buttons;

shell/platform/android/io/flutter/view/FlutterView.java

@@ -329,9 +329,9 @@ public class FlutterView extends SurfaceView
         long timeStamp = event.getEventTime() * 1000; // Convert from milliseconds to microseconds.
 
         packet.putLong(timeStamp); // time_stamp
-        packet.putLong(event.getPointerId(pointerIndex)); // pointer
         packet.putLong(pointerChange); // change
         packet.putLong(pointerKind); // kind
+        packet.putLong(event.getPointerId(pointerIndex)); // device
         packet.putDouble(event.getX(pointerIndex)); // physical_x
         packet.putDouble(event.getY(pointerIndex)); // physical_y
 

shell/platform/darwin/desktop/sky_window.mm

@@ -39,6 +39,7 @@ static inline blink::PointerData::Change PointerChangeFromNSEventPhase(
 
 @implementation SkyWindow {
   std::unique_ptr<shell::PlatformViewMac> _platformView;
+  bool _mouseIsDown;
 }
 
 @synthesize renderSurface = _renderSurface;
@@ -118,6 +119,25 @@ static inline blink::PointerData::Change PointerChangeFromNSEventPhase(
   pointer_data.pressure = 1.0;
   pointer_data.pressure_max = 1.0;
 
+  switch (pointer_data.change) {
+    case blink::PointerData::Change::kDown:
+      _mouseIsDown = true;
+      break;
+    case blink::PointerData::Change::kCancel:
+    case blink::PointerData::Change::kUp:
+      _mouseIsDown = false;
+      break;
+    case blink::PointerData::Change::kMove:
+      if (!_mouseIsDown)
+        pointer_data.change = blink::PointerData::Change::kHover;
+      break;
+    case blink::PointerData::Change::kAdd:
+    case blink::PointerData::Change::kRemove:
+    case blink::PointerData::Change::kHover:
+      FTL_DCHECK(!_mouseIsDown);
+      break;
+  }
+
   blink::Threads::UI()->PostTask(
       [ engine = _platformView->engine().GetWeakPtr(), pointer_data ] {
         if (engine.get()) {

shell/platform/darwin/ios/framework/Source/FlutterViewController.mm

@@ -267,21 +267,21 @@ static inline PointerChangeMapperPhase PointerChangePhaseFromUITouchPhase(
 
   int i = 0;
   for (UITouch* touch in touches) {
-    int touch_identifier = 0;
+    int device_id = 0;
 
     switch (eventTypePhase.second) {
       case Accessed:
-        touch_identifier = _touchMapper.identifierOf(touch);
+        device_id = _touchMapper.identifierOf(touch);
         break;
       case Added:
-        touch_identifier = _touchMapper.registerTouch(touch);
+        device_id = _touchMapper.registerTouch(touch);
         break;
       case Removed:
-        touch_identifier = _touchMapper.unregisterTouch(touch);
+        device_id = _touchMapper.unregisterTouch(touch);
         break;
     }
 
-    DCHECK(touch_identifier != 0);
+    DCHECK(device_id != 0);
     CGPoint windowCoordinates = [touch locationInView:nil];
 
     blink::PointerData pointer_data;
@@ -291,7 +291,7 @@ static inline PointerChangeMapperPhase PointerChangePhaseFromUITouchPhase(
     pointer_data.time_stamp = touch.timestamp * kMicrosecondsPerSecond;
     pointer_data.change = eventTypePhase.first;
     pointer_data.kind = blink::PointerData::DeviceKind::kTouch;
-    pointer_data.pointer = touch_identifier;
+    pointer_data.device = device_id;
     pointer_data.physical_x = windowCoordinates.x * scale;
     pointer_data.physical_y = windowCoordinates.y * scale;
     pointer_data.pressure = 1.0;