Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1335 insertions, 0 deletions

diff --git a/widget/BasicEvents.h b/widget/BasicEvents.h
new file mode 100644
index 0000000000..b3707f1cf4
--- /dev/null
+++ b/widget/BasicEvents.h
@@ -0,0 +1,1335 @@
+/* -*- 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 <type_traits>
+
+#include "mozilla/EventForwards.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/dom/EventTarget.h"
+#include "mozilla/layers/LayersTypes.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
+
+class nsIPrincipal;
+
+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 mInTargetPhase is true, the event is in target phase.
+  bool mInTargetPhase : 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 in the process.
+  // So, this is false even if the event has already been dispatched
+  // in another process.
+  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;
+  // If mOnlySystemGroupDispatch is true, the event will be dispatched only to
+  // event listeners added in the system group.
+  bool mOnlySystemGroupDispatch : 1;
+  // The event's action will be handled by APZ. The main thread should not
+  // perform its associated action.
+  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 mCameFromAnotherProcess is true, the event came from another process.
+  bool mCameFromAnotherProcess : 1;
+
+  /**
+   * 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 remote 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.
+    // Note that the propagation stopped flag is important for the reply event
+    // handler in the main process because it's used for making whether it's
+    // ignored by the remote process or not.
+    if (!XRE_IsParentProcess() && IsWaitingReplyFromRemoteProcess()) {
+      mPropagationStopped = mImmediatePropagationStopped = false;
+    }
+    // mDispatchedAtLeastOnce indicates the state in current process.
+    mDispatchedAtLeastOnce = 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
+   * BrowserParent or somewhere.
+   */
+  inline bool HasBeenPostedToRemoteProcess() const {
+    return mPostedToRemoteProcess;
+  }
+  /**
+   * Return true if the event came from another process.
+   */
+  inline bool CameFromAnotherProcess() const { return mCameFromAnotherProcess; }
+  /**
+   * Mark the event as coming from another process.
+   */
+  inline void MarkAsComingFromAnotherProcess() {
+    mCameFromAnotherProcess = true;
+  }
+  /**
+   * 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 uint64_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:
+  // Timestamp when the message was created.
+  TimeStamp mTimeStamp;
+
+  WidgetEventTime() : mTimeStamp(TimeStamp::Now()) {}
+
+  explicit WidgetEventTime(const WidgetEventTime* aTime)
+      : mTimeStamp(aTime ? aTime->mTimeStamp : TimeStamp::Now()) {
+    MOZ_ASSERT(aTime != this);
+    MOZ_ASSERT_IF(aTime, !aTime->mTimeStamp.IsNull());
+  }
+
+  explicit WidgetEventTime(TimeStamp aTimeStamp) : mTimeStamp(aTimeStamp) {}
+
+  void AssignEventTime(const WidgetEventTime& aOther) {
+    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 || mMessage == eMozVisualResize ||
+            mMessage == eMozVisualScroll || mMessage == eEditorInput ||
+            mMessage == eFormSelect) {
+          mFlags.mCancelable = false;
+        } else {
+          mFlags.mCancelable = true;
+        }
+        mFlags.mBubbles = true;
+        break;
+    }
+  }
+
+ protected:
+  WidgetEvent(bool aIsTrusted, EventMessage aMessage,
+              EventClassID aEventClassID,
+              const WidgetEventTime* aTime = nullptr)
+      : WidgetEventTime(aTime),
+        mClass(aEventClassID),
+        mMessage(aMessage),
+        mRefPoint(0, 0),
+        mLastRefPoint(0, 0),
+        mFocusSequenceNumber(0),
+        mSpecifiedEventType(nullptr),
+        mPath(nullptr),
+        mLayersId(layers::LayersId{0}) {
+    MOZ_COUNT_CTOR(WidgetEvent);
+    mFlags.Clear();
+    mFlags.mIsTrusted = aIsTrusted;
+    SetDefaultCancelableAndBubbles();
+    SetDefaultComposed();
+    SetDefaultComposedInNativeAnonymousContent();
+  }
+
+  WidgetEvent() : mPath(nullptr) { MOZ_COUNT_CTOR(WidgetEvent); }
+
+ public:
+  WidgetEvent(bool aIsTrusted, EventMessage aMessage,
+              const WidgetEventTime* aTime = nullptr)
+      : WidgetEvent(aIsTrusted, aMessage, eBasicEventClass, aTime) {}
+
+  MOZ_COUNTED_DTOR_VIRTUAL(WidgetEvent)
+
+  WidgetEvent(const WidgetEvent& aOther) : WidgetEventTime(aOther) {
+    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, this);
+    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.
+  // This is in visual coordinates, i.e. the correct RelativeTo value that
+  // expresses what this is relative to is `{viewportFrame, Visual}`, where
+  // `viewportFrame` is the viewport frame of the widget's root document.
+  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
+  //       or "input" event is dispatched with dom::Event class.
+  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;
+
+  // The LayersId of the content process that this event should be
+  // dispatched to. This field is only used in the chrome process
+  // and doesn't get remoted to child processes.
+  layers::LayersId mLayersId;
+
+  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;
+    // mLayersId intentionally not copied, since it's not used within content
+    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();
+  }
+  /**
+   * Return true if the event came from another process.
+   */
+  inline bool CameFromAnotherProcess() const {
+    return mFlags.CameFromAnotherProcess();
+  }
+  /**
+   * Mark the event as coming from another process.
+   */
+  inline void MarkAsComingFromAnotherProcess() {
+    mFlags.MarkAsComingFromAnotherProcess();
+  }
+  /**
+   * 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 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 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 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;
+  /**
+   * Whether the event handler can flush pending notifications or not.
+   */
+  bool AllowFlushingPendingNotifications() const;
+  /**
+   * Initialize mComposed
+   */
+  void SetDefaultComposed() {
+    switch (mClass) {
+      case eClipboardEventClass:
+        mFlags.mComposed = true;
+        break;
+      case eCompositionEventClass:
+        mFlags.mComposed =
+            mMessage == eCompositionStart || mMessage == eCompositionUpdate ||
+            mMessage == eCompositionChange || 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 || mMessage == eEditorBeforeInput;
+        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 || mMessage == eXULPopupShowing ||
+            mMessage == eXULPopupHiding || mMessage == eXULPopupShown ||
+            mMessage == eXULPopupHidden;
+        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;
+      case eMouseScrollEventClass:
+        // Legacy mouse scroll events are composed too, for consistency with
+        // wheel.
+        mFlags.mComposed = mMessage == eLegacyMouseLineOrPageScroll ||
+                           mMessage == eLegacyMousePixelScroll;
+        break;
+      default:
+        mFlags.mComposed = false;
+        break;
+    }
+  }
+
+  void SetComposed(const nsAString& aEventTypeArg) {
+    mFlags.mComposed =  // composition events
+        aEventTypeArg.EqualsLiteral("compositionstart") ||
+        aEventTypeArg.EqualsLiteral("compositionupdate") ||
+        aEventTypeArg.EqualsLiteral("compositionend") ||
+        aEventTypeArg.EqualsLiteral("text") ||
+        // 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::WidgetGUIEvent
+ ******************************************************************************/
+
+class WidgetGUIEvent : public WidgetEvent {
+ protected:
+  WidgetGUIEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget,
+                 EventClassID aEventClassID,
+                 const WidgetEventTime* aTime = nullptr)
+      : WidgetEvent(aIsTrusted, aMessage, aEventClassID, aTime),
+        mWidget(aWidget) {}
+
+  WidgetGUIEvent() = default;
+
+ public:
+  virtual WidgetGUIEvent* AsGUIEvent() override { return this; }
+
+  WidgetGUIEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget,
+                 const WidgetEventTime* aTime = nullptr)
+      : WidgetEvent(aIsTrusted, aMessage, eGUIEventClass, aTime),
+        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, this);
+    result->AssignGUIEventData(*this, true);
+    result->mFlags = mFlags;
+    return result;
+  }
+
+  // Originator of the event
+  nsCOMPtr<nsIWidget> mWidget;
+
+  void AssignGUIEventData(const WidgetGUIEvent& aEvent, bool aCopyTargets) {
+    AssignEventData(aEvent, aCopyTargets);
+    // widget should be initialized with the constructor.
+  }
+};
+
+/******************************************************************************
+ * 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 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 (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,
+                   const WidgetEventTime* aTime = nullptr)
+      : WidgetGUIEvent(aIsTrusted, aMessage, aWidget, aEventClassID, aTime),
+        mModifiers(0) {}
+
+  WidgetInputEvent() : mModifiers(0) {}
+
+ public:
+  virtual WidgetInputEvent* AsInputEvent() override { return this; }
+
+  WidgetInputEvent(bool aIsTrusted, EventMessage aMessage, nsIWidget* aWidget,
+                   const WidgetEventTime* aTime = nullptr)
+      : WidgetGUIEvent(aIsTrusted, aMessage, aWidget, eInputEventClass, aTime),
+        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, this);
+    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 (Command key on macOS, Windows logo key
+  // on Windows, Super/Hyper key on Linux, Meta key on Android).
+  bool IsMeta() const { return ((mModifiers & MODIFIER_META) != 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,
+                  const WidgetEventTime* aTime = nullptr)
+      : WidgetGUIEvent(aIsTrusted, aMessage, aWidget, aEventClassID, aTime),
+        mDetail(0),
+        mCausedByUntrustedEvent(false) {}
+
+  InternalUIEvent(bool aIsTrusted, EventMessage aMessage,
+                  EventClassID aEventClassID,
+                  const WidgetEventTime* aTime = nullptr)
+      : WidgetGUIEvent(aIsTrusted, aMessage, nullptr, aEventClassID, aTime),
+        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,
+                  const WidgetEventTime* aTime = nullptr)
+      : WidgetGUIEvent(aIsTrusted, aMessage, nullptr, eUIEventClass, aTime),
+        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, this);
+    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__