/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this file,
 * You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_dom_WheelEvent_h_
#define mozilla_dom_WheelEvent_h_

#include "mozilla/dom/MouseEvent.h"
#include "mozilla/dom/WheelEventBinding.h"
#include "mozilla/EventForwards.h"

namespace mozilla {
namespace dom {

class WheelEvent : public MouseEvent {
 public:
  WheelEvent(EventTarget* aOwner, nsPresContext* aPresContext,
             WidgetWheelEvent* aWheelEvent);

  NS_INLINE_DECL_REFCOUNTING_INHERITED(WheelEvent, MouseEvent)

  static already_AddRefed<WheelEvent> Constructor(const GlobalObject& aGlobal,
                                                  const nsAString& aType,
                                                  const WheelEventInit& aParam);

  virtual JSObject* WrapObjectInternal(
      JSContext* aCx, JS::Handle<JSObject*> aGivenProto) override {
    return WheelEvent_Binding::Wrap(aCx, this, aGivenProto);
  }

  // NOTE: DeltaX(), DeltaY() and DeltaZ() return CSS pixels when deltaMode is
  //       DOM_DELTA_PIXEL. (The internal event's delta values are device pixels
  //       if it's dispatched by widget)
  double DeltaX(CallerType);
  double DeltaY(CallerType);
  double DeltaZ(CallerType);
  uint32_t DeltaMode(CallerType);

  void InitWheelEvent(const nsAString& aType, bool aCanBubble, bool aCancelable,
                      nsGlobalWindowInner* aView, int32_t aDetail,
                      int32_t aScreenX, int32_t aScreenY, int32_t aClientX,
                      int32_t aClientY, uint16_t aButton,
                      EventTarget* aRelatedTarget,
                      const nsAString& aModifiersList, double aDeltaX,
                      double aDeltaY, double aDeltaZ, uint32_t aDeltaMode);

 protected:
  ~WheelEvent() = default;

  double ToWebExposedDelta(const WidgetWheelEvent&, double aDelta, CallerType);

 private:
  int32_t mAppUnitsPerDevPixel;
  enum class DeltaModeCheckingState : uint8_t {
    // Neither deltaMode nor the delta values have been accessed.
    Unknown,
    // The delta values have been accessed, without checking deltaMode first.
    Unchecked,
    // The deltaMode has been checked.
    Checked,
  };

  // For compat reasons, we might expose a DOM_DELTA_LINE event as
  // DOM_DELTA_PIXEL instead. Whether we do that depends on whether the event
  // has been asked for the deltaMode before the deltas. If it has, we assume
  // that the page will correctly handle DOM_DELTA_LINE. This variable tracks
  // that state. See bug 1392460.
  DeltaModeCheckingState mDeltaModeCheckingState =
      DeltaModeCheckingState::Unknown;
};

}  // namespace dom
}  // namespace mozilla

already_AddRefed<mozilla::dom::WheelEvent> NS_NewDOMWheelEvent(
    mozilla::dom::EventTarget* aOwner, nsPresContext* aPresContext,
    mozilla::WidgetWheelEvent* aEvent);

#endif  // mozilla_dom_WheelEvent_h_