widget/BasicEvents.h
author Valentin Gosu <valentin.gosu@gmail.com>
Fri, 02 Nov 2018 17:38:37 -0400
changeset 501038 8016d0d1a391f1327a0375fb6d4f20228b2784aa
parent 490571 971943621f6e52daa0e94e48c3d846567978ff26
child 503724 27e0f9af668581b82b1ceadc64f38a39fdef904b
permissions -rw-r--r--
Bug 1503725 - Do not deallocate nsThreadShutdownContext when leaking thread. r=erahm, a=RyanVM Sometimes when we call ShutdownWithTimeout on a thread pool, the unresponsive thread that we leak will actually complete before the main thread is done. In that case, the thread will dereference the thread shutdown context, so we must intentionally leak it too. Differential Revision: https://phabricator.services.mozilla.com/D10645

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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_BasicEvents_h__
#define mozilla_BasicEvents_h__

#include <stdint.h>

#include "mozilla/dom/EventTarget.h"
#include "mozilla/EventForwards.h"
#include "mozilla/TimeStamp.h"
#include "nsCOMPtr.h"
#include "nsAtom.h"
#include "nsISupportsImpl.h"
#include "nsIWidget.h"
#include "nsString.h"
#include "Units.h"

#ifdef DEBUG
#include "nsXULAppAPI.h"
#endif // #ifdef DEBUG

namespace IPC {
template<typename T>
struct ParamTraits;
} // namespace IPC

namespace mozilla {

class EventTargetChainItem;

enum class CrossProcessForwarding
{
  // eStop prevents the event to be sent to remote process.
  eStop,
  // eAllow keeps current state of the event whether it's sent to remote
  // process.  In other words, eAllow does NOT mean that making the event
  // sent to remote process when IsCrossProcessForwardingStopped() returns
  // true.
  eAllow,
};

/******************************************************************************
 * mozilla::BaseEventFlags
 *
 * BaseEventFlags must be a POD struct for safe to use memcpy (including
 * in ParamTraits<BaseEventFlags>).  So don't make virtual methods, constructor,
 * destructor and operators.
 * This is necessary for VC which is NOT C++0x compiler.
 ******************************************************************************/

struct BaseEventFlags
{
public:
  // If mIsTrusted is true, the event is a trusted event.  Otherwise, it's
  // an untrusted event.
  bool    mIsTrusted : 1;
  // If mInBubblingPhase is true, the event is in bubbling phase or target
  // phase.
  bool    mInBubblingPhase : 1;
  // If mInCapturePhase is true, the event is in capture phase or target phase.
  bool    mInCapturePhase : 1;
  // If mInSystemGroup is true, the event is being dispatched in system group.
  bool    mInSystemGroup: 1;
  // If mCancelable is true, the event can be consumed.  I.e., calling
  // dom::Event::PreventDefault() can prevent the default action.
  bool    mCancelable : 1;
  // If mBubbles is true, the event can bubble.  Otherwise, cannot be handled
  // in bubbling phase.
  bool    mBubbles : 1;
  // If mPropagationStopped is true, dom::Event::StopPropagation() or
  // dom::Event::StopImmediatePropagation() has been called.
  bool    mPropagationStopped : 1;
  // If mImmediatePropagationStopped is true,
  // dom::Event::StopImmediatePropagation() has been called.
  // Note that mPropagationStopped must be true when this is true.
  bool    mImmediatePropagationStopped : 1;
  // If mDefaultPrevented is true, the event has been consumed.
  // E.g., dom::Event::PreventDefault() has been called or
  // the default action has been performed.
  bool    mDefaultPrevented : 1;
  // If mDefaultPreventedByContent is true, the event has been
  // consumed by content.
  // Note that mDefaultPrevented must be true when this is true.
  bool    mDefaultPreventedByContent : 1;
  // If mDefaultPreventedByChrome is true, the event has been
  // consumed by chrome.
  // Note that mDefaultPrevented must be true when this is true.
  bool    mDefaultPreventedByChrome : 1;
  // mMultipleActionsPrevented may be used when default handling don't want to
  // be prevented, but only one of the event targets should handle the event.
  // For example, when a <label> element is in another <label> element and
  // the first <label> element is clicked, that one may set this true.
  // Then, the second <label> element won't handle the event.
  bool    mMultipleActionsPrevented : 1;
  // If mIsBeingDispatched is true, the DOM event created from the event is
  // dispatching into the DOM tree and not completed.
  bool    mIsBeingDispatched : 1;
  // If mDispatchedAtLeastOnce is true, the event has been dispatched
  // as a DOM event and the dispatch has been completed.
  bool    mDispatchedAtLeastOnce : 1;
  // If mIsSynthesizedForTests is true, the event has been synthesized for
  // automated tests or something hacky approach of an add-on.
  bool    mIsSynthesizedForTests : 1;
  // If mExceptionWasRaised is true, one of the event handlers has raised an
  // exception.
  bool    mExceptionWasRaised : 1;
  // If mRetargetToNonNativeAnonymous is true and the target is in a non-native
  // native anonymous subtree, the event target is set to mOriginalTarget.
  bool    mRetargetToNonNativeAnonymous : 1;
  // If mNoContentDispatch is true, the event is never dispatched to the
  // event handlers which are added to the contents, onfoo attributes and
  // properties.  Note that this flag is ignored when
  // EventChainPreVisitor::mForceContentDispatch is set true.  For exapmle,
  // window and document object sets it true.  Therefore, web applications
  // can handle the event if they add event listeners to the window or the
  // document.
  // XXX This is an ancient and broken feature, don't use this for new bug
  //     as far as possible.
  bool    mNoContentDispatch : 1;
  // If mOnlyChromeDispatch is true, the event is dispatched to only chrome.
  bool    mOnlyChromeDispatch : 1;
  // Indicates if the key combination is reserved by chrome.  This is set by
  // MarkAsReservedByChrome().
  bool mIsReservedByChrome : 1;
  // If mOnlySystemGroupDispatchInContent is true, event listeners added to
  // the default group for non-chrome EventTarget won't be called.
  // Be aware, if this is true, EventDispatcher needs to check if each event
  // listener is added to chrome node, so, don't set this to true for the
  // events which are fired a lot of times like eMouseMove.
  bool    mOnlySystemGroupDispatchInContent : 1;
  // The event's action will be handled by APZ. The main thread should not
  // perform its associated action. This is currently only relevant for
  // wheel and touch events.
  bool mHandledByAPZ : 1;
  // True if the event is currently being handled by an event listener that
  // was registered as a passive listener.
  bool mInPassiveListener: 1;
  // If mComposed is true, the event fired by nodes in shadow DOM can cross the
  // boundary of shadow DOM and light DOM.
  bool mComposed : 1;
  // Similar to mComposed. Set it to true to allow events cross the boundary
  // between native non-anonymous content and native anonymouse content
  bool mComposedInNativeAnonymousContent : 1;
  // Set to true for events which are suppressed or delayed so that later a
  // DelayedEvent of it is dispatched. This is used when parent side process
  // the key event after content side, and may drop the event if the event
  // was suppressed or delayed in contents side.
  // It is also set to true for the events (in a DelayedInputEvent), which will
  // be dispatched afterwards.
  bool mIsSuppressedOrDelayed : 1;
  // Certain mouse events can be marked as positionless to return 0 from
  // coordinate related getters.
  bool mIsPositionless : 1;

  // Flags managing state of propagation between processes.
  // Note the the following flags shouldn't be referred directly.  Use utility
  // methods instead.

  // If mNoRemoteProcessDispatch is true, the event is not allowed to be sent
  // to remote process.
  bool mNoRemoteProcessDispatch : 1;
  // If mWantReplyFromContentProcess is true, the event will be redispatched
  // in the parent process after the content process has handled it. Useful
  // for when the parent process need the know first how the event was used
  // by content before handling it itself.
  bool mWantReplyFromContentProcess : 1;
  // If mPostedToRemoteProcess is true, the event has been posted to the
  // remote process (but it's not handled yet if it's not a duplicated event
  // instance).
  bool mPostedToRemoteProcess : 1;

  // If the event is being handled in target phase, returns true.
  inline bool InTargetPhase() const
  {
    return (mInBubblingPhase && mInCapturePhase);
  }

  /**
   * Helper methods for methods of DOM Event.
   */
  inline void StopPropagation()
  {
    mPropagationStopped = true;
  }
  inline void StopImmediatePropagation()
  {
    StopPropagation();
    mImmediatePropagationStopped = true;
  }
  inline void PreventDefault(bool aCalledByDefaultHandler = true)
  {
    if (!mCancelable) {
      return;
    }
    mDefaultPrevented = true;
    // Note that even if preventDefault() has already been called by chrome,
    // a call of preventDefault() by content needs to overwrite
    // mDefaultPreventedByContent to true because in such case, defaultPrevented
    // must be true when web apps check it after they call preventDefault().
    if (aCalledByDefaultHandler) {
      StopCrossProcessForwarding();
      mDefaultPreventedByChrome = true;
    } else {
      mDefaultPreventedByContent = true;
    }
  }
  // This should be used only before dispatching events into the DOM tree.
  inline void
  PreventDefaultBeforeDispatch(CrossProcessForwarding aCrossProcessForwarding)
  {
    if (!mCancelable) {
      return;
    }
    mDefaultPrevented = true;
    if (aCrossProcessForwarding == CrossProcessForwarding::eStop) {
      StopCrossProcessForwarding();
    }
  }
  inline bool DefaultPrevented() const
  {
    return mDefaultPrevented;
  }
  inline bool DefaultPreventedByContent() const
  {
    MOZ_ASSERT(!mDefaultPreventedByContent || DefaultPrevented());
    return mDefaultPreventedByContent;
  }
  inline bool IsTrusted() const
  {
    return mIsTrusted;
  }
  inline bool PropagationStopped() const
  {
    return mPropagationStopped;
  }

  // Helper methods to access flags managing state of propagation between
  // processes.

  /**
   * Prevent to be dispatched to remote process.
   */
  inline void StopCrossProcessForwarding()
  {
    MOZ_ASSERT(!mPostedToRemoteProcess);
    mNoRemoteProcessDispatch = true;
    mWantReplyFromContentProcess = false;
  }
  /**
   * Return true if the event shouldn't be dispatched to remote process.
   */
  inline bool IsCrossProcessForwardingStopped() const
  {
    return mNoRemoteProcessDispatch;
  }
  /**
   * Mark the event as waiting reply from remote process.
   * If the caller needs to win other keyboard event handlers in chrome,
   * the caller should call StopPropagation() too.
   * Otherwise, if the caller just needs to know if the event is consumed by
   * either content or chrome, it should just call this because the event
   * may be reserved by chrome and it needs to be dispatched into the DOM
   * tree in chrome for checking if it's reserved before being sent to any
   * remote processes.
   */
  inline void MarkAsWaitingReplyFromRemoteProcess()
  {
    MOZ_ASSERT(!mPostedToRemoteProcess);
    mNoRemoteProcessDispatch = false;
    mWantReplyFromContentProcess = true;
  }
  /**
   * Reset "waiting reply from remote process" state.  This is useful when
   * you dispatch a copy of an event coming from different process.
   */
  inline void ResetWaitingReplyFromRemoteProcessState()
  {
    if (IsWaitingReplyFromRemoteProcess()) {
      // FYI: mWantReplyFromContentProcess is also used for indicating
      //      "handled in remote process" state.  Therefore, only when
      //      IsWaitingReplyFromRemoteProcess() returns true, this should
      //      reset the flag.
      mWantReplyFromContentProcess = false;
    }
  }
  /**
   * Return true if the event handler should wait reply event.  I.e., if this
   * returns true, any event handler should do nothing with the event.
   */
  inline bool IsWaitingReplyFromRemoteProcess() const
  {
    return !mNoRemoteProcessDispatch && mWantReplyFromContentProcess;
  }
  /**
   * Mark the event as already handled in the remote process.  This should be
   * called when initializing reply events.
   */
  inline void MarkAsHandledInRemoteProcess()
  {
    mNoRemoteProcessDispatch = true;
    mWantReplyFromContentProcess = true;
    mPostedToRemoteProcess = false;
  }
  /**
   * Return true if the event has already been handled in the remote process.
   */
  inline bool IsHandledInRemoteProcess() const
  {
    return mNoRemoteProcessDispatch && mWantReplyFromContentProcess;
  }
  /**
   * Return true if the event should be sent back to its parent process.
   */
  inline bool WantReplyFromContentProcess() const
  {
    MOZ_ASSERT(!XRE_IsParentProcess());
    return IsWaitingReplyFromRemoteProcess();
  }
  /**
   * Mark the event has already posted to a remote process.
   */
  inline void MarkAsPostedToRemoteProcess()
  {
    MOZ_ASSERT(!IsCrossProcessForwardingStopped());
    mPostedToRemoteProcess = true;
  }
  /**
   * Reset the cross process dispatching state.  This should be used when a
   * process receives the event because the state is in the sender.
   */
  inline void ResetCrossProcessDispatchingState()
  {
    MOZ_ASSERT(!IsCrossProcessForwardingStopped());
    mPostedToRemoteProcess = false;
    // Ignore propagation state in the different process if it's marked as
    // "waiting reply from remote process" because the process needs to
    // stop propagation in the process until receiving a reply event.
    if (IsWaitingReplyFromRemoteProcess()) {
      mPropagationStopped = mImmediatePropagationStopped = false;
    }
  }
  /**
   * Return true if the event has been posted to a remote process.
   * Note that MarkAsPostedToRemoteProcess() is called by
   * ParamTraits<mozilla::WidgetEvent>.  Therefore, it *might* be possible
   * that posting the event failed even if this returns true.  But that must
   * really rare.  If that'd be problem for you, you should unmark this in
   * TabParent or somewhere.
   */
  inline bool HasBeenPostedToRemoteProcess() const
  {
    return mPostedToRemoteProcess;
  }
  /**
   * Mark the event is reserved by chrome.  I.e., shouldn't be dispatched to
   * content because it shouldn't be cancelable.
   */
  inline void MarkAsReservedByChrome()
  {
    MOZ_ASSERT(!mPostedToRemoteProcess);
    mIsReservedByChrome = true;
    // For reserved commands (such as Open New Tab), we don't need to wait for
    // the content to answer, neither to give a chance for content to override
    // its behavior.
    StopCrossProcessForwarding();
    // If the event is reserved by chrome, we shouldn't expose the event to
    // web contents because such events shouldn't be cancelable.  So, it's not
    // good behavior to fire such events but to ignore the defaultPrevented
    // attribute value in chrome.
    mOnlySystemGroupDispatchInContent = true;
  }
  /**
   * Return true if the event is reserved by chrome.
   */
  inline bool IsReservedByChrome() const
  {
    MOZ_ASSERT(!mIsReservedByChrome ||
               (IsCrossProcessForwardingStopped() &&
                mOnlySystemGroupDispatchInContent));
    return mIsReservedByChrome;
  }

  inline void Clear()
  {
    SetRawFlags(0);
  }
  // Get if either the instance's bit or the aOther's bit is true, the
  // instance's bit becomes true.  In other words, this works like:
  // eventFlags |= aOther;
  inline void Union(const BaseEventFlags& aOther)
  {
    RawFlags rawFlags = GetRawFlags() | aOther.GetRawFlags();
    SetRawFlags(rawFlags);
  }

private:
  typedef uint32_t RawFlags;

  inline void SetRawFlags(RawFlags aRawFlags)
  {
    static_assert(sizeof(BaseEventFlags) <= sizeof(RawFlags),
      "mozilla::EventFlags must not be bigger than the RawFlags");
    memcpy(this, &aRawFlags, sizeof(BaseEventFlags));
  }
  inline RawFlags GetRawFlags() const
  {
    RawFlags result = 0;
    memcpy(&result, this, sizeof(BaseEventFlags));
    return result;
  }
};

/******************************************************************************
 * mozilla::EventFlags
 ******************************************************************************/

struct EventFlags : public BaseEventFlags
{
  EventFlags()
  {
    Clear();
  }
};

/******************************************************************************
 * mozilla::WidgetEventTime
 ******************************************************************************/

class WidgetEventTime
{
public:
  // Elapsed time, in milliseconds, from a platform-specific zero time
  // to the time the message was created
  uint64_t mTime;
  // Timestamp when the message was created. Set in parallel to 'time' until we
  // determine if it is safe to drop 'time' (see bug 77992).
  TimeStamp mTimeStamp;

  WidgetEventTime()
    : mTime(0)
    , mTimeStamp(TimeStamp::Now())
  {
  }

  WidgetEventTime(uint64_t aTime,
                  TimeStamp aTimeStamp)
    : mTime(aTime)
    , mTimeStamp(aTimeStamp)
  {
  }

  void AssignEventTime(const WidgetEventTime& aOther)
  {
    mTime = aOther.mTime;
    mTimeStamp = aOther.mTimeStamp;
  }
};

/******************************************************************************
 * mozilla::WidgetEvent
 ******************************************************************************/

class WidgetEvent : public WidgetEventTime
{
private:
  void SetDefaultCancelableAndBubbles()
  {
    switch (mClass) {
      case eEditorInputEventClass:
        mFlags.mCancelable = false;
        mFlags.mBubbles = mFlags.mIsTrusted;
        break;
      case eMouseEventClass:
        mFlags.mCancelable = (mMessage != eMouseEnter &&
                              mMessage != eMouseLeave);
        mFlags.mBubbles = (mMessage != eMouseEnter &&
                           mMessage != eMouseLeave);
        break;
      case ePointerEventClass:
        mFlags.mCancelable = (mMessage != ePointerEnter &&
                              mMessage != ePointerLeave &&
                              mMessage != ePointerCancel &&
                              mMessage != ePointerGotCapture &&
                              mMessage != ePointerLostCapture);
        mFlags.mBubbles = (mMessage != ePointerEnter &&
                           mMessage != ePointerLeave);
        break;
      case eDragEventClass:
        mFlags.mCancelable = (mMessage != eDragExit &&
                              mMessage != eDragLeave &&
                              mMessage != eDragEnd);
        mFlags.mBubbles = true;
        break;
      case eSMILTimeEventClass:
        mFlags.mCancelable = false;
        mFlags.mBubbles = false;
        break;
      case eTransitionEventClass:
      case eAnimationEventClass:
        mFlags.mCancelable = false;
        mFlags.mBubbles = true;
        break;
      case eCompositionEventClass:
        // XXX compositionstart is cancelable in draft of DOM3 Events.
        //     However, it doesn't make sense for us, we cannot cancel
        //     composition when we send compositionstart event.
        mFlags.mCancelable = false;
        mFlags.mBubbles = true;
        break;
      default:
        if (mMessage == eResize) {
          mFlags.mCancelable = false;
        } else {
          mFlags.mCancelable = true;
        }
        mFlags.mBubbles = true;
        break;
    }
  }

protected:
  WidgetEvent(bool aIsTrusted,
              EventMessage aMessage,
              EventClassID aEventClassID)
    : WidgetEventTime()
    , mClass(aEventClassID)
    , mMessage(aMessage)
    , mRefPoint(0, 0)
    , mLastRefPoint(0, 0)
    , mFocusSequenceNumber(0)
    , mSpecifiedEventType(nullptr)
    , mPath(nullptr)
  {
    MOZ_COUNT_CTOR(WidgetEvent);
    mFlags.Clear();
    mFlags.mIsTrusted = aIsTrusted;
    SetDefaultCancelableAndBubbles();
    SetDefaultComposed();
    SetDefaultComposedInNativeAnonymousContent();
  }

  WidgetEvent()
    : WidgetEventTime()
    , mPath(nullptr)
  {
    MOZ_COUNT_CTOR(WidgetEvent);
  }

public:
  WidgetEvent(bool aIsTrusted, EventMessage aMessage)
    : WidgetEvent(aIsTrusted, aMessage, eBasicEventClass)
  {
  }

  virtual ~WidgetEvent()
  {
    MOZ_COUNT_DTOR(WidgetEvent);
  }

  WidgetEvent(const WidgetEvent& aOther)
    : WidgetEventTime()
  {
    MOZ_COUNT_CTOR(WidgetEvent);
    *this = aOther;
  }
  WidgetEvent& operator=(const WidgetEvent& aOther) = default;

  WidgetEvent(WidgetEvent&& aOther)
    : WidgetEventTime(std::move(aOther))
    , mClass(aOther.mClass)
    , mMessage(aOther.mMessage)
    , mRefPoint(std::move(aOther.mRefPoint))
    , mLastRefPoint(std::move(aOther.mLastRefPoint))
    , mFocusSequenceNumber(aOther.mFocusSequenceNumber)
    , mFlags(std::move(aOther.mFlags))
    , mSpecifiedEventType(std::move(aOther.mSpecifiedEventType))
    , mSpecifiedEventTypeString(std::move(aOther.mSpecifiedEventTypeString))
    , mTarget(std::move(aOther.mTarget))
    , mCurrentTarget(std::move(aOther.mCurrentTarget))
    , mOriginalTarget(std::move(aOther.mOriginalTarget))
    , mRelatedTarget(std::move(aOther.mRelatedTarget))
    , mOriginalRelatedTarget(std::move(aOther.mOriginalRelatedTarget))
    , mPath(std::move(aOther.mPath))
  {
    MOZ_COUNT_CTOR(WidgetEvent);
  }
  WidgetEvent& operator=(WidgetEvent&& aOther) = default;

  virtual WidgetEvent* Duplicate() const
  {
    MOZ_ASSERT(mClass == eBasicEventClass,
               "Duplicate() must be overridden by sub class");
    WidgetEvent* result = new WidgetEvent(false, mMessage);
    result->AssignEventData(*this, true);
    result->mFlags = mFlags;
    return result;
  }

  EventClassID mClass;
  EventMessage mMessage;
  // Relative to the widget of the event, or if there is no widget then it is
  // in screen coordinates. Not modified by layout code.
  LayoutDeviceIntPoint mRefPoint;
  // The previous mRefPoint, if known, used to calculate mouse movement deltas.
  LayoutDeviceIntPoint mLastRefPoint;
  // The sequence number of the last potentially focus changing event handled
  // by APZ. This is used to track when that event has been processed by content,
  // and focus can be reconfirmed for async keyboard scrolling.
  uint64_t mFocusSequenceNumber;
  // See BaseEventFlags definition for the detail.
  BaseEventFlags mFlags;

  // If JS creates an event with unknown event type or known event type but
  // for different event interface, the event type is stored to this.
  // NOTE: This is always used if the instance is a WidgetCommandEvent instance.
  RefPtr<nsAtom> mSpecifiedEventType;

  // nsAtom isn't available on non-main thread due to unsafe.  Therefore,
  // mSpecifiedEventTypeString is used instead of mSpecifiedEventType if
  // the event is created in non-main thread.
  nsString mSpecifiedEventTypeString;

  // Event targets, needed by DOM Events
  // Note that when you need event target for DOM event, you should use
  // Get*DOMEventTarget() instead of accessing these members directly.
  nsCOMPtr<dom::EventTarget> mTarget;
  nsCOMPtr<dom::EventTarget> mCurrentTarget;
  nsCOMPtr<dom::EventTarget> mOriginalTarget;

  /// The possible related target
  nsCOMPtr<dom::EventTarget> mRelatedTarget;
  nsCOMPtr<dom::EventTarget> mOriginalRelatedTarget;

  nsTArray<EventTargetChainItem>* mPath;

  dom::EventTarget* GetDOMEventTarget() const;
  dom::EventTarget* GetCurrentDOMEventTarget() const;
  dom::EventTarget* GetOriginalDOMEventTarget() const;

  void AssignEventData(const WidgetEvent& aEvent, bool aCopyTargets)
  {
    // mClass should be initialized with the constructor.
    // mMessage should be initialized with the constructor.
    mRefPoint = aEvent.mRefPoint;
    // mLastRefPoint doesn't need to be copied.
    mFocusSequenceNumber = aEvent.mFocusSequenceNumber;
    AssignEventTime(aEvent);
    // mFlags should be copied manually if it's necessary.
    mSpecifiedEventType = aEvent.mSpecifiedEventType;
    // mSpecifiedEventTypeString should be copied manually if it's necessary.
    mTarget = aCopyTargets ? aEvent.mTarget : nullptr;
    mCurrentTarget = aCopyTargets ? aEvent.mCurrentTarget : nullptr;
    mOriginalTarget = aCopyTargets ? aEvent.mOriginalTarget : nullptr;
    mRelatedTarget = aCopyTargets ? aEvent.mRelatedTarget : nullptr;
    mOriginalRelatedTarget =
      aCopyTargets ? aEvent.mOriginalRelatedTarget : nullptr;
  }

  /**
   * Helper methods for methods of DOM Event.
   */
  void StopPropagation() { mFlags.StopPropagation(); }
  void StopImmediatePropagation() { mFlags.StopImmediatePropagation(); }
  void PreventDefault(bool aCalledByDefaultHandler = true,
                      nsIPrincipal* aPrincipal = nullptr);

  void
  PreventDefaultBeforeDispatch(CrossProcessForwarding aCrossProcessForwarding)
  {
    mFlags.PreventDefaultBeforeDispatch(aCrossProcessForwarding);
  }
  bool DefaultPrevented() const { return mFlags.DefaultPrevented(); }
  bool DefaultPreventedByContent() const
  {
    return mFlags.DefaultPreventedByContent();
  }
  bool IsTrusted() const { return mFlags.IsTrusted(); }
  bool PropagationStopped() const { return mFlags.PropagationStopped(); }

  /**
   * Prevent to be dispatched to remote process.
   */
  inline void StopCrossProcessForwarding()
  {
    mFlags.StopCrossProcessForwarding();
  }
  /**
   * Return true if the event shouldn't be dispatched to remote process.
   */
  inline bool IsCrossProcessForwardingStopped() const
  {
    return mFlags.IsCrossProcessForwardingStopped();
  }
  /**
   * Mark the event as waiting reply from remote process.
   * Note that this also stops immediate propagation in current process.
   */
  inline void MarkAsWaitingReplyFromRemoteProcess()
  {
    mFlags.MarkAsWaitingReplyFromRemoteProcess();
  }
  /**
   * Reset "waiting reply from remote process" state.  This is useful when
   * you dispatch a copy of an event coming from different process.
   */
  inline void ResetWaitingReplyFromRemoteProcessState()
  {
    mFlags.ResetWaitingReplyFromRemoteProcessState();
  }
  /**
   * Return true if the event handler should wait reply event.  I.e., if this
   * returns true, any event handler should do nothing with the event.
   */
  inline bool IsWaitingReplyFromRemoteProcess() const
  {
    return mFlags.IsWaitingReplyFromRemoteProcess();
  }
  /**
   * Mark the event as already handled in the remote process.  This should be
   * called when initializing reply events.
   */
  inline void MarkAsHandledInRemoteProcess()
  {
    mFlags.MarkAsHandledInRemoteProcess();
  }
  /**
   * Return true if the event has already been handled in the remote process.
   * I.e., if this returns true, the event is a reply event.
   */
  inline bool IsHandledInRemoteProcess() const
  {
    return mFlags.IsHandledInRemoteProcess();
  }
  /**
   * Return true if the event should be sent back to its parent process.
   * So, usual event handlers shouldn't call this.
   */
  inline bool WantReplyFromContentProcess() const
  {
    return mFlags.WantReplyFromContentProcess();
  }
  /**
   * Mark the event has already posted to a remote process.
   */
  inline void MarkAsPostedToRemoteProcess()
  {
    mFlags.MarkAsPostedToRemoteProcess();
  }
  /**
   * Reset the cross process dispatching state.  This should be used when a
   * process receives the event because the state is in the sender.
   */
  inline void ResetCrossProcessDispatchingState()
  {
    mFlags.ResetCrossProcessDispatchingState();
  }
  /**
   * Return true if the event has been posted to a remote process.
   */
  inline bool HasBeenPostedToRemoteProcess() const
  {
    return mFlags.HasBeenPostedToRemoteProcess();
  }
  /**
   * Mark the event is reserved by chrome.  I.e., shouldn't be dispatched to
   * content because it shouldn't be cancelable.
   */
  inline void MarkAsReservedByChrome()
  {
    mFlags.MarkAsReservedByChrome();
  }
  /**
   * Return true if the event is reserved by chrome.
   */
  inline bool IsReservedByChrome() const
  {
    return mFlags.IsReservedByChrome();
  }

  /**
   * Utils for checking event types
   */

  /**
   * As*Event() returns the pointer of the instance only when the instance is
   * the class or one of its derived class.
   */
#define NS_ROOT_EVENT_CLASS(aPrefix, aName)
#define NS_EVENT_CLASS(aPrefix, aName) \
  virtual aPrefix##aName* As##aName(); \
  const aPrefix##aName* As##aName() const;

#include "mozilla/EventClassList.h"

#undef NS_EVENT_CLASS
#undef NS_ROOT_EVENT_CLASS

  /**
   * Returns true if the event is a query content event.
   */
  bool IsQueryContentEvent() const;
  /**
   * Returns true if the event is a selection event.
   */
  bool IsSelectionEvent() const;
  /**
   * Returns true if the event is a content command event.
   */
  bool IsContentCommandEvent() const;
  /**
   * Returns true if the event is a native event deliverer event for plugin.
   */
  bool IsNativeEventDelivererForPlugin() const;

  /**
   * Returns true if the event mMessage is one of mouse events.
   */
  bool HasMouseEventMessage() const;
  /**
   * Returns true if the event mMessage is one of drag events.
   */
  bool HasDragEventMessage() const;
  /**
   * Returns true if aMessage or mMessage is one of key events.
   */
  static bool IsKeyEventMessage(EventMessage aMessage);
  bool HasKeyEventMessage() const
  {
    return IsKeyEventMessage(mMessage);
  }
  /**
   * Returns true if the event mMessage is one of composition events or text
   * event.
   */
  bool HasIMEEventMessage() const;
  /**
   * Returns true if the event mMessage is one of plugin activation events.
   */
  bool HasPluginActivationEventMessage() const;

  /**
   * Returns true if the event can be sent to remote process.
   */
  bool CanBeSentToRemoteProcess() const;
  /**
   * Returns true if the original target is a remote process and the event
   * will be posted to the remote process later.
   */
  bool WillBeSentToRemoteProcess() const;
  /**
   * Returns true if the event is native event deliverer event for plugin and
   * it should be retarted to focused document.
   */
  bool IsRetargetedNativeEventDelivererForPlugin() const;
  /**
   * Returns true if the event is native event deliverer event for plugin and
   * it should NOT be retarted to focused document.
   */
  bool IsNonRetargetedNativeEventDelivererForPlugin() const;
  /**
   * Returns true if the event is related to IME handling.  It includes
   * IME events, query content events and selection events.
   * Be careful when you use this.
   */
  bool IsIMERelatedEvent() const;

  /**
   * Whether the event should be handled by the frame of the mouse cursor
   * position or not.  When it should be handled there (e.g., the mouse events),
   * this returns true.
   */
  bool IsUsingCoordinates() const;
  /**
   * Whether the event should be handled by the focused DOM window in the
   * same top level window's or not.  E.g., key events, IME related events
   * (including the query content events, they are used in IME transaction)
   * should be handled by the (last) focused window rather than the dispatched
   * window.
   *
   * NOTE: Even if this returns true, the event isn't going to be handled by the
   * application level active DOM window which is on another top level window.
   * So, when the event is fired on a deactive window, the event is going to be
   * handled by the last focused DOM window in the last focused window.
   */
  bool IsTargetedAtFocusedWindow() const;
  /**
   * Whether the event should be handled by the focused content or not.  E.g.,
   * key events, IME related events and other input events which are not handled
   * by the frame of the mouse cursor position.
   *
   * NOTE: Even if this returns true, the event isn't going to be handled by the
   * application level active DOM window which is on another top level window.
   * So, when the event is fired on a deactive window, the event is going to be
   * handled by the last focused DOM element of the last focused DOM window in
   * the last focused window.
   */
  bool IsTargetedAtFocusedContent() const;
  /**
   * Whether the event should cause a DOM event.
   */
  bool IsAllowedToDispatchDOMEvent() const;
  /**
   * Whether the event should be dispatched in system group.
   */
  bool IsAllowedToDispatchInSystemGroup() const;
  /**
   * Whether the event should be blocked for fingerprinting resistance.
   */
  bool IsBlockedForFingerprintingResistance() const;
  /**
   * Initialize mComposed
   */
  void SetDefaultComposed()
  {
    switch (mClass) {
      case eCompositionEventClass:
        mFlags.mComposed = mMessage == eCompositionStart ||
                           mMessage == eCompositionUpdate ||
                           mMessage == eCompositionEnd;
        break;
      case eDragEventClass:
        // All drag & drop events are composed
        mFlags.mComposed = mMessage == eDrag || mMessage == eDragEnd ||
                           mMessage == eDragEnter || mMessage == eDragExit ||
                           mMessage == eDragLeave || mMessage == eDragOver ||
                           mMessage == eDragStart || mMessage == eDrop;
        break;
      case eEditorInputEventClass:
        mFlags.mComposed = mMessage == eEditorInput;
        break;
      case eFocusEventClass:
        mFlags.mComposed = mMessage == eBlur || mMessage == eFocus ||
                           mMessage == eFocusOut || mMessage == eFocusIn;
        break;
      case eKeyboardEventClass:
        mFlags.mComposed = mMessage == eKeyDown || mMessage == eKeyUp ||
                           mMessage == eKeyPress;
        break;
      case eMouseEventClass:
        mFlags.mComposed = mMessage == eMouseClick ||
                           mMessage == eMouseDoubleClick ||
                           mMessage == eMouseAuxClick ||
                           mMessage == eMouseDown || mMessage == eMouseUp ||
                           mMessage == eMouseOver || mMessage == eMouseOut ||
                           mMessage == eMouseMove || mMessage == eContextMenu;
        break;
      case ePointerEventClass:
        // All pointer events are composed
        mFlags.mComposed = mMessage == ePointerDown ||
                           mMessage == ePointerMove || mMessage == ePointerUp ||
                           mMessage == ePointerCancel ||
                           mMessage == ePointerOver ||
                           mMessage == ePointerOut ||
                           mMessage == ePointerGotCapture ||
                           mMessage == ePointerLostCapture;
        break;
      case eTouchEventClass:
        // All touch events are composed
        mFlags.mComposed = mMessage == eTouchStart || mMessage == eTouchEnd ||
                           mMessage == eTouchMove || mMessage == eTouchCancel;
        break;
      case eUIEventClass:
        mFlags.mComposed = mMessage == eLegacyDOMFocusIn ||
                           mMessage == eLegacyDOMFocusOut ||
                           mMessage == eLegacyDOMActivate;
        break;
      case eWheelEventClass:
        // All wheel events are composed
        mFlags.mComposed = mMessage == eWheel;
        break;
      default:
        mFlags.mComposed = false;
        break;
    }
  }

  void SetComposed(const nsAString& aEventTypeArg)
  {
    mFlags.mComposed = // composition events
                       aEventTypeArg.EqualsLiteral("compositionstart") ||
                       aEventTypeArg.EqualsLiteral("compositionupdate") ||
                       aEventTypeArg.EqualsLiteral("compositionend") ||
                       // drag and drop events
                       aEventTypeArg.EqualsLiteral("dragstart") ||
                       aEventTypeArg.EqualsLiteral("drag") ||
                       aEventTypeArg.EqualsLiteral("dragenter") ||
                       aEventTypeArg.EqualsLiteral("dragexit") ||
                       aEventTypeArg.EqualsLiteral("dragleave") ||
                       aEventTypeArg.EqualsLiteral("dragover") ||
                       aEventTypeArg.EqualsLiteral("drop") ||
                       aEventTypeArg.EqualsLiteral("dropend") ||
                       // editor input events
                       aEventTypeArg.EqualsLiteral("input") ||
                       aEventTypeArg.EqualsLiteral("beforeinput") ||
                       // focus events
                       aEventTypeArg.EqualsLiteral("blur") ||
                       aEventTypeArg.EqualsLiteral("focus") ||
                       aEventTypeArg.EqualsLiteral("focusin") ||
                       aEventTypeArg.EqualsLiteral("focusout") ||
                       // keyboard events
                       aEventTypeArg.EqualsLiteral("keydown") ||
                       aEventTypeArg.EqualsLiteral("keyup") ||
                       aEventTypeArg.EqualsLiteral("keypress") ||
                       // mouse events
                       aEventTypeArg.EqualsLiteral("click") ||
                       aEventTypeArg.EqualsLiteral("dblclick") ||
                       aEventTypeArg.EqualsLiteral("mousedown") ||
                       aEventTypeArg.EqualsLiteral("mouseup") ||
                       aEventTypeArg.EqualsLiteral("mouseenter") ||
                       aEventTypeArg.EqualsLiteral("mouseleave") ||
                       aEventTypeArg.EqualsLiteral("mouseover") ||
                       aEventTypeArg.EqualsLiteral("mouseout") ||
                       aEventTypeArg.EqualsLiteral("mousemove") ||
                       aEventTypeArg.EqualsLiteral("contextmenu") ||
                       // pointer events
                       aEventTypeArg.EqualsLiteral("pointerdown") ||
                       aEventTypeArg.EqualsLiteral("pointermove") ||
                       aEventTypeArg.EqualsLiteral("pointerup") ||
                       aEventTypeArg.EqualsLiteral("pointercancel") ||
                       aEventTypeArg.EqualsLiteral("pointerover") ||
                       aEventTypeArg.EqualsLiteral("pointerout") ||
                       aEventTypeArg.EqualsLiteral("pointerenter") ||
                       aEventTypeArg.EqualsLiteral("pointerleave") ||
                       aEventTypeArg.EqualsLiteral("gotpointercapture") ||
                       aEventTypeArg.EqualsLiteral("lostpointercapture") ||
                       // touch events
                       aEventTypeArg.EqualsLiteral("touchstart") ||
                       aEventTypeArg.EqualsLiteral("touchend") ||
                       aEventTypeArg.EqualsLiteral("touchmove") ||
                       aEventTypeArg.EqualsLiteral("touchcancel") ||
                       // UI legacy events
                       aEventTypeArg.EqualsLiteral("DOMFocusIn") ||
                       aEventTypeArg.EqualsLiteral("DOMFocusOut") ||
                       aEventTypeArg.EqualsLiteral("DOMActivate") ||
                       // wheel events
                       aEventTypeArg.EqualsLiteral("wheel");
  }

  void SetComposed(bool aComposed)
  {
    mFlags.mComposed = aComposed;
  }

  void SetDefaultComposedInNativeAnonymousContent()
  {
    // For compatibility concerns, we set mComposedInNativeAnonymousContent to
    // false for those events we want to stop propagation.
    //
    // nsVideoFrame may create anonymous image element which fires eLoad,
    // eLoadStart, eLoadEnd, eLoadError. We don't want these events cross
    // the boundary of NAC
    mFlags.mComposedInNativeAnonymousContent = mMessage != eLoad &&
                                               mMessage != eLoadStart &&
                                               mMessage != eLoadEnd &&
                                               mMessage != eLoadError;
  }

  bool IsUserAction() const;
};

/******************************************************************************
 * mozilla::NativeEventData
 *
 * WidgetGUIEvent's mPluginEvent member used to be a void* pointer,
 * used to reference external, OS-specific data structures.
 *
 * That void* pointer wasn't serializable by itself, causing
 * certain plugin events not to function in e10s. See bug 586656.
 *
 * To make this serializable, we changed this void* pointer into
 * a proper buffer, and copy these external data structures into this
 * buffer.
 *
 * That buffer is NativeEventData::mBuffer below.
 *
 * We wrap this in that NativeEventData class providing operators to
 * be compatible with existing code that was written around
 * the old void* field.
 ******************************************************************************/

class NativeEventData final
{
  nsTArray<uint8_t> mBuffer;

  friend struct IPC::ParamTraits<mozilla::NativeEventData>;

public:

  explicit operator bool() const
  {
    return !mBuffer.IsEmpty();
  }

  template<typename T>
  explicit operator const T*() const
  {
    return mBuffer.IsEmpty()
           ? nullptr
           : reinterpret_cast<const T*>(mBuffer.Elements());
  }

  template <typename T>
  void Copy(const T& other)
  {
    static_assert(!mozilla::IsPointer<T>::value, "Don't want a pointer!");
    mBuffer.SetLength(sizeof(T));
    memcpy(mBuffer.Elements(), &other, mBuffer.Length());
  }

  void Clear()
  {
    mBuffer.Clear();
  }
};

/******************************************************************************
 * mozilla::WidgetGUIEvent
 ******************************************************************************/

class WidgetGUIEvent : public WidgetEvent
{
protected:
  WidgetGUIEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget,
                 EventClassID aEventClassID)
    : WidgetEvent(aIsTrusted, aMessage, aEventClassID)
    , mWidget(aWidget)
  {
  }

  WidgetGUIEvent()
  {
  }

public:
  virtual WidgetGUIEvent* AsGUIEvent() override { return this; }

  WidgetGUIEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget)
    : WidgetEvent(aIsTrusted, aMessage, eGUIEventClass)
    , mWidget(aWidget)
  {
  }

  virtual WidgetEvent* Duplicate() const override
  {
    MOZ_ASSERT(mClass == eGUIEventClass,
               "Duplicate() must be overridden by sub class");
    // Not copying widget, it is a weak reference.
    WidgetGUIEvent* result = new WidgetGUIEvent(false, mMessage, nullptr);
    result->AssignGUIEventData(*this, true);
    result->mFlags = mFlags;
    return result;
  }

  // Originator of the event
  nsCOMPtr<nsIWidget> mWidget;

  /*
   * Ideally though, we wouldn't allow arbitrary reinterpret_cast'ing here;
   * instead, we would at least store type information here so that
   * this class can't be used to reinterpret one structure type into another.
   * We can also wonder if it would be possible to properly extend
   * WidgetGUIEvent and other Event classes to remove the need for this
   * mPluginEvent field.
   */
  typedef NativeEventData PluginEvent;

  // Event for NPAPI plugin
  PluginEvent mPluginEvent;

  void AssignGUIEventData(const WidgetGUIEvent& aEvent, bool aCopyTargets)
  {
    AssignEventData(aEvent, aCopyTargets);

    // widget should be initialized with the constructor.

    mPluginEvent = aEvent.mPluginEvent;
  }
};

/******************************************************************************
 * mozilla::Modifier
 *
 * All modifier keys should be defined here.  This is used for managing
 * modifier states for DOM Level 3 or later.
 ******************************************************************************/

enum Modifier
{
  MODIFIER_NONE       = 0x0000,
  MODIFIER_ALT        = 0x0001,
  MODIFIER_ALTGRAPH   = 0x0002,
  MODIFIER_CAPSLOCK   = 0x0004,
  MODIFIER_CONTROL    = 0x0008,
  MODIFIER_FN         = 0x0010,
  MODIFIER_FNLOCK     = 0x0020,
  MODIFIER_META       = 0x0040,
  MODIFIER_NUMLOCK    = 0x0080,
  MODIFIER_SCROLLLOCK = 0x0100,
  MODIFIER_SHIFT      = 0x0200,
  MODIFIER_SYMBOL     = 0x0400,
  MODIFIER_SYMBOLLOCK = 0x0800,
  MODIFIER_OS         = 0x1000
};

/******************************************************************************
 * Modifier key names.
 ******************************************************************************/

#define NS_DOM_KEYNAME_ALT        "Alt"
#define NS_DOM_KEYNAME_ALTGRAPH   "AltGraph"
#define NS_DOM_KEYNAME_CAPSLOCK   "CapsLock"
#define NS_DOM_KEYNAME_CONTROL    "Control"
#define NS_DOM_KEYNAME_FN         "Fn"
#define NS_DOM_KEYNAME_FNLOCK     "FnLock"
#define NS_DOM_KEYNAME_META       "Meta"
#define NS_DOM_KEYNAME_NUMLOCK    "NumLock"
#define NS_DOM_KEYNAME_SCROLLLOCK "ScrollLock"
#define NS_DOM_KEYNAME_SHIFT      "Shift"
#define NS_DOM_KEYNAME_SYMBOL     "Symbol"
#define NS_DOM_KEYNAME_SYMBOLLOCK "SymbolLock"
#define NS_DOM_KEYNAME_OS         "OS"

/******************************************************************************
 * mozilla::Modifiers
 ******************************************************************************/

typedef uint16_t Modifiers;

class MOZ_STACK_CLASS GetModifiersName final : public nsAutoCString
{
public:
  explicit GetModifiersName(Modifiers aModifiers)
  {
    if (aModifiers & MODIFIER_ALT) {
      AssignLiteral(NS_DOM_KEYNAME_ALT);
    }
    if (aModifiers & MODIFIER_ALTGRAPH) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_ALTGRAPH);
    }
    if (aModifiers & MODIFIER_CAPSLOCK) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_CAPSLOCK);
    }
    if (aModifiers & MODIFIER_CONTROL) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_CONTROL);
    }
    if (aModifiers & MODIFIER_FN) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_FN);
    }
    if (aModifiers & MODIFIER_FNLOCK) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_FNLOCK);
    }
    if (aModifiers & MODIFIER_META) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_META);
    }
    if (aModifiers & MODIFIER_NUMLOCK) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_NUMLOCK);
    }
    if (aModifiers & MODIFIER_SCROLLLOCK) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_SCROLLLOCK);
    }
    if (aModifiers & MODIFIER_SHIFT) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_SHIFT);
    }
    if (aModifiers & MODIFIER_SYMBOL) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_SYMBOL);
    }
    if (aModifiers & MODIFIER_SYMBOLLOCK) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_SYMBOLLOCK);
    }
    if (aModifiers & MODIFIER_OS) {
      MaybeAppendSeparator();
      AppendLiteral(NS_DOM_KEYNAME_OS);
    }
    if (IsEmpty()) {
      AssignLiteral("none");
    }
  }

private:
  void MaybeAppendSeparator()
  {
    if (!IsEmpty()) {
      AppendLiteral(" | ");
    }
  }
};

/******************************************************************************
 * mozilla::WidgetInputEvent
 ******************************************************************************/

class WidgetInputEvent : public WidgetGUIEvent
{
protected:
  WidgetInputEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget,
                   EventClassID aEventClassID)
    : WidgetGUIEvent(aIsTrusted, aMessage, aWidget, aEventClassID)
    , mModifiers(0)
  {
  }

  WidgetInputEvent()
    : mModifiers(0)
  {
  }

public:
  virtual WidgetInputEvent* AsInputEvent() override { return this; }

  WidgetInputEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget)
    : WidgetGUIEvent(aIsTrusted, aMessage, aWidget, eInputEventClass)
    , mModifiers(0)
  {
  }

  virtual WidgetEvent* Duplicate() const override
  {
    MOZ_ASSERT(mClass == eInputEventClass,
               "Duplicate() must be overridden by sub class");
    // Not copying widget, it is a weak reference.
    WidgetInputEvent* result = new WidgetInputEvent(false, mMessage, nullptr);
    result->AssignInputEventData(*this, true);
    result->mFlags = mFlags;
    return result;
  }


  /**
   * Returns a modifier of "Accel" virtual modifier which is used for shortcut
   * key.
   */
  static Modifier AccelModifier();

  /**
   * GetModifier() returns a modifier flag which is activated by aDOMKeyName.
   */
  static Modifier GetModifier(const nsAString& aDOMKeyName);

  // true indicates the accel key on the environment is down
  bool IsAccel() const
  {
    return ((mModifiers & AccelModifier()) != 0);
  }

  // true indicates the shift key is down
  bool IsShift() const
  {
    return ((mModifiers & MODIFIER_SHIFT) != 0);
  }
  // true indicates the control key is down
  bool IsControl() const
  {
    return ((mModifiers & MODIFIER_CONTROL) != 0);
  }
  // true indicates the alt key is down
  bool IsAlt() const
  {
    return ((mModifiers & MODIFIER_ALT) != 0);
  }
  // true indicates the meta key is down (or, on Mac, the Command key)
  bool IsMeta() const
  {
    return ((mModifiers & MODIFIER_META) != 0);
  }
  // true indicates the win key is down on Windows. Or the Super or Hyper key
  // is down on Linux.
  bool IsOS() const
  {
    return ((mModifiers & MODIFIER_OS) != 0);
  }
  // true indicates the alt graph key is down
  // NOTE: on Mac, the option key press causes both IsAlt() and IsAltGrpah()
  //       return true.
  bool IsAltGraph() const
  {
    return ((mModifiers & MODIFIER_ALTGRAPH) != 0);
  }
  // true indicates the CapLock LED is turn on.
  bool IsCapsLocked() const
  {
    return ((mModifiers & MODIFIER_CAPSLOCK) != 0);
  }
  // true indicates the NumLock LED is turn on.
  bool IsNumLocked() const
  {
    return ((mModifiers & MODIFIER_NUMLOCK) != 0);
  }
  // true indicates the ScrollLock LED is turn on.
  bool IsScrollLocked() const
  {
    return ((mModifiers & MODIFIER_SCROLLLOCK) != 0);
  }

  // true indicates the Fn key is down, but this is not supported by native
  // key event on any platform.
  bool IsFn() const
  {
    return ((mModifiers & MODIFIER_FN) != 0);
  }
  // true indicates the FnLock LED is turn on, but we don't know such
  // keyboards nor platforms.
  bool IsFnLocked() const
  {
    return ((mModifiers & MODIFIER_FNLOCK) != 0);
  }
  // true indicates the Symbol is down, but this is not supported by native
  // key event on any platforms.
  bool IsSymbol() const
  {
    return ((mModifiers & MODIFIER_SYMBOL) != 0);
  }
  // true indicates the SymbolLock LED is turn on, but we don't know such
  // keyboards nor platforms.
  bool IsSymbolLocked() const
  {
    return ((mModifiers & MODIFIER_SYMBOLLOCK) != 0);
  }

  void InitBasicModifiers(bool aCtrlKey,
                          bool aAltKey,
                          bool aShiftKey,
                          bool aMetaKey)
  {
    mModifiers = 0;
    if (aCtrlKey) {
      mModifiers |= MODIFIER_CONTROL;
    }
    if (aAltKey) {
      mModifiers |= MODIFIER_ALT;
    }
    if (aShiftKey) {
      mModifiers |= MODIFIER_SHIFT;
    }
    if (aMetaKey) {
      mModifiers |= MODIFIER_META;
    }
  }

  Modifiers mModifiers;

  void AssignInputEventData(const WidgetInputEvent& aEvent, bool aCopyTargets)
  {
    AssignGUIEventData(aEvent, aCopyTargets);

    mModifiers = aEvent.mModifiers;
  }
};

/******************************************************************************
 * mozilla::InternalUIEvent
 *
 * XXX Why this inherits WidgetGUIEvent rather than WidgetEvent?
 ******************************************************************************/

class InternalUIEvent : public WidgetGUIEvent
{
protected:
  InternalUIEvent()
    : mDetail(0)
    , mCausedByUntrustedEvent(false)
  {
  }

  InternalUIEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget,
                  EventClassID aEventClassID)
    : WidgetGUIEvent(aIsTrusted, aMessage, aWidget, aEventClassID)
    , mDetail(0)
    , mCausedByUntrustedEvent(false)
  {
  }

  InternalUIEvent(bool aIsTrusted, EventMessage aMessage,
                  EventClassID aEventClassID)
    : WidgetGUIEvent(aIsTrusted, aMessage, nullptr, aEventClassID)
    , mDetail(0)
    , mCausedByUntrustedEvent(false)
  {
  }

public:
  virtual InternalUIEvent* AsUIEvent() override { return this; }

  /**
   * If the UIEvent is caused by another event (e.g., click event),
   * aEventCausesThisEvent should be the event.  If there is no such event,
   * this should be nullptr.
   */
  InternalUIEvent(bool aIsTrusted, EventMessage aMessage,
                  const WidgetEvent* aEventCausesThisEvent)
    : WidgetGUIEvent(aIsTrusted, aMessage, nullptr, eUIEventClass)
    , mDetail(0)
    , mCausedByUntrustedEvent(
        aEventCausesThisEvent && !aEventCausesThisEvent->IsTrusted())
  {
  }

  virtual WidgetEvent* Duplicate() const override
  {
    MOZ_ASSERT(mClass == eUIEventClass,
               "Duplicate() must be overridden by sub class");
    InternalUIEvent* result = new InternalUIEvent(false, mMessage, nullptr);
    result->AssignUIEventData(*this, true);
    result->mFlags = mFlags;
    return result;
  }

  int32_t mDetail;
  // mCausedByUntrustedEvent is true if the event is caused by untrusted event.
  bool mCausedByUntrustedEvent;

  // If you check the event is a trusted event and NOT caused by an untrusted
  // event, IsTrustable() returns what you expected.
  bool IsTrustable() const
  {
    return IsTrusted() && !mCausedByUntrustedEvent;
  }

  void AssignUIEventData(const InternalUIEvent& aEvent, bool aCopyTargets)
  {
    AssignGUIEventData(aEvent, aCopyTargets);

    mDetail = aEvent.mDetail;
    mCausedByUntrustedEvent = aEvent.mCausedByUntrustedEvent;
  }
};

} // namespace mozilla

#endif // mozilla_BasicEvents_h__