ui: Add copy constructors to event types

We rely on the implicit copy constructors in a large number of places
in the code. However, the existance of ui::Event::Clone() makes people
think they have to use that method to copy events -- they don't, if
they have an event with a known type.

Write out the copy constructors to make that clear.

Bug: none
Test: existing events_unittests, other existing UI unittests
Change-Id: I18cd94bdc1cdec9d91c2987da3dd28356edd8568
Reviewed-on: https://chromium-review.googlesource.com/830674Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524488}

ui/events/event.cc

@@ -457,8 +457,7 @@ CancelModeEvent::~CancelModeEvent() {
 ////////////////////////////////////////////////////////////////////////////////
 // LocatedEvent
 
-LocatedEvent::~LocatedEvent() {
-}
+LocatedEvent::~LocatedEvent() = default;
 
 LocatedEvent::LocatedEvent(const base::NativeEvent& native_event)
     : Event(native_event,
@@ -476,6 +475,8 @@ LocatedEvent::LocatedEvent(EventType type,
       location_(location),
       root_location_(root_location) {}
 
+LocatedEvent::LocatedEvent(const LocatedEvent& copy) = default;
+
 void LocatedEvent::UpdateForRootTransform(
     const gfx::Transform& reversed_root_transform,
     const gfx::Transform& reversed_local_transform) {
@@ -542,17 +543,7 @@ PointerDetails::PointerDetails(EventPointerType pointer_type,
   offset = pointer_offset;
 }
 
-PointerDetails::PointerDetails(const PointerDetails& other)
-    : pointer_type(other.pointer_type),
-      radius_x(other.radius_x),
-      radius_y(other.radius_y),
-      force(other.force),
-      tilt_x(other.tilt_x),
-      tilt_y(other.tilt_y),
-      tangential_pressure(other.tangential_pressure),
-      twist(other.twist),
-      id(other.id),
-      offset(other.offset) {}
+PointerDetails::PointerDetails(const PointerDetails& other) = default;
 
 const PointerId PointerDetails::kUnknownPointerId = -1;
 
@@ -636,6 +627,10 @@ MouseEvent::MouseEvent(EventType type,
     SetType(ET_MOUSE_DRAGGED);
 }
 
+MouseEvent::MouseEvent(const MouseEvent& other) = default;
+
+MouseEvent::~MouseEvent() = default;
+
 // static
 bool MouseEvent::IsRepeatedClickEvent(
     const MouseEvent& event1,
@@ -811,6 +806,8 @@ MouseWheelEvent::MouseWheelEvent(const gfx::Vector2d& offset,
   SetType(ui::ET_MOUSEWHEEL);
 }
 
+MouseWheelEvent::~MouseWheelEvent() = default;
+
 #if defined(OS_WIN)
 // This value matches windows WHEEL_DELTA.
 // static
@@ -1449,6 +1446,10 @@ ScrollEvent::ScrollEvent(EventType type,
   latency()->set_source_event_type(ui::SourceEventType::WHEEL);
 }
 
+ScrollEvent::ScrollEvent(const ScrollEvent& other) = default;
+
+ScrollEvent::~ScrollEvent() = default;
+
 void ScrollEvent::Scale(const float factor) {
   x_offset_ *= factor;
   y_offset_ *= factor;
@@ -1475,7 +1476,8 @@ GestureEvent::GestureEvent(float x,
   latency()->set_source_event_type(ui::SourceEventType::TOUCH);
 }
 
-GestureEvent::~GestureEvent() {
-}
+GestureEvent::GestureEvent(const GestureEvent& other) = default;
+
+GestureEvent::~GestureEvent() = default;
 
 }  // namespace ui

ui/events/event.h

@@ -51,6 +51,8 @@ using PointerId = int32_t;
 
 class EVENTS_EXPORT Event {
  public:
+  // Copies an arbitrary event. If you have a typed event (e.g. a MouseEvent)
+  // just use its copy constructor.
   static std::unique_ptr<Event> Clone(const Event& event);
 
   virtual ~Event();
@@ -390,6 +392,8 @@ class EVENTS_EXPORT LocatedEvent : public Event {
  protected:
   friend class LocatedEventTestApi;
 
+  LocatedEvent(const LocatedEvent& copy);
+
   explicit LocatedEvent(const base::NativeEvent& native_event);
 
   // Create a new LocatedEvent which is identical to the provided model.
@@ -496,6 +500,8 @@ class EVENTS_EXPORT MouseEvent : public LocatedEvent {
  public:
   static const PointerId kMousePointerId;
 
+  // NOTE: On some platforms this will allow an event to be constructed from a
+  // void*, see base::NativeEvent.
   explicit MouseEvent(const base::NativeEvent& native_event);
 
   // |pointer_event.IsMousePointerEvent()| must be true.
@@ -539,6 +545,9 @@ class EVENTS_EXPORT MouseEvent : public LocatedEvent {
                  PointerDetails(EventPointerType::POINTER_TYPE_MOUSE,
                                 kMousePointerId));
 
+  MouseEvent(const MouseEvent& copy);
+  ~MouseEvent() override;
+
   // Conveniences to quickly test what button is down
   bool IsOnlyLeftMouseButton() const {
     return button_flags() == EF_LEFT_MOUSE_BUTTON;
@@ -635,7 +644,8 @@ class EVENTS_EXPORT MouseWheelEvent : public MouseEvent {
   explicit MouseWheelEvent(const ScrollEvent& scroll_event);
   explicit MouseWheelEvent(const PointerEvent& pointer_event);
   MouseWheelEvent(const MouseEvent& mouse_event, int x_offset, int y_offset);
-  MouseWheelEvent(const MouseWheelEvent& mouse_wheel_event);
+  MouseWheelEvent(const MouseWheelEvent& copy);
+  ~MouseWheelEvent() override;
 
   template <class T>
   MouseWheelEvent(const MouseWheelEvent& model,
@@ -998,6 +1008,9 @@ class EVENTS_EXPORT ScrollEvent : public MouseEvent {
               int finger_count,
               EventMomentumPhase momentum_phase = EventMomentumPhase::NONE);
 
+  ScrollEvent(const ScrollEvent& copy);
+  ~ScrollEvent() override;
+
   // Scale the scroll event's offset value.
   // This is useful in the multi-monitor setup where it needs to be scaled
   // to provide a consistent user experience.
@@ -1044,7 +1057,7 @@ class EVENTS_EXPORT GestureEvent : public LocatedEvent {
       : LocatedEvent(model, source, target),
         details_(model.details_) {
   }
-
+  GestureEvent(const GestureEvent& copy);
   ~GestureEvent() override;
 
   const GestureEventDetails& details() const { return details_; }