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diff --git a/dom/events/AsyncEventDispatcher.h b/dom/events/AsyncEventDispatcher.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_AsyncEventDispatcher_h_
+#define mozilla_AsyncEventDispatcher_h_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/dom/Event.h"
+#include "nsCOMPtr.h"
+#include "mozilla/dom/Document.h"
+#include "nsString.h"
+#include "nsThreadUtils.h"
+
+class nsINode;
+
+namespace mozilla {
+
+/**
+ * Use AsyncEventDispatcher to fire a DOM event that requires safe a stable DOM.
+ * For example, you may need to fire an event from within layout, but
+ * want to ensure that the event handler doesn't mutate the DOM at
+ * the wrong time, in order to avoid resulting instability.
+ */
+
+class AsyncEventDispatcher : public CancelableRunnable {
+ public:
+ /**
+ * If aOnlyChromeDispatch is true, the event is dispatched to only
+ * chrome node. In that case, if aTarget is already a chrome node,
+ * the event is dispatched to it, otherwise the dispatch path starts
+ * at the first chrome ancestor of that target.
+ */
+ AsyncEventDispatcher(
+ dom::EventTarget* aTarget, const nsAString& aEventType,
+ CanBubble aCanBubble,
+ ChromeOnlyDispatch aOnlyChromeDispatch = ChromeOnlyDispatch::eNo,
+ Composed aComposed = Composed::eDefault)
+ : CancelableRunnable("AsyncEventDispatcher"),
+ mTarget(aTarget),
+ mEventType(aEventType),
+ mEventMessage(eUnidentifiedEvent),
+ mCanBubble(aCanBubble),
+ mOnlyChromeDispatch(aOnlyChromeDispatch),
+ mComposed(aComposed) {}
+
+ /**
+ * If aOnlyChromeDispatch is true, the event is dispatched to only
+ * chrome node. In that case, if aTarget is already a chrome node,
+ * the event is dispatched to it, otherwise the dispatch path starts
+ * at the first chrome ancestor of that target.
+ */
+ AsyncEventDispatcher(nsINode* aTarget, mozilla::EventMessage aEventMessage,
+ CanBubble aCanBubble,
+ ChromeOnlyDispatch aOnlyChromeDispatch)
+ : CancelableRunnable("AsyncEventDispatcher"),
+ mTarget(aTarget),
+ mEventMessage(aEventMessage),
+ mCanBubble(aCanBubble),
+ mOnlyChromeDispatch(aOnlyChromeDispatch) {
+ mEventType.SetIsVoid(true);
+ MOZ_ASSERT(mEventMessage != eUnidentifiedEvent);
+ }
+
+ AsyncEventDispatcher(dom::EventTarget* aTarget,
+ mozilla::EventMessage aEventMessage,
+ CanBubble aCanBubble)
+ : CancelableRunnable("AsyncEventDispatcher"),
+ mTarget(aTarget),
+ mEventMessage(aEventMessage),
+ mCanBubble(aCanBubble) {
+ mEventType.SetIsVoid(true);
+ MOZ_ASSERT(mEventMessage != eUnidentifiedEvent);
+ }
+
+ /**
+ * aEvent must have been created without Widget*Event and Internal*Event
+ * because this constructor assumes that it's safe to use aEvent
+ * asynchronously (i.e., after all objects allocated in the stack are
+ * destroyed).
+ */
+ AsyncEventDispatcher(
+ dom::EventTarget* aTarget, dom::Event* aEvent,
+ ChromeOnlyDispatch aOnlyChromeDispatch = ChromeOnlyDispatch::eNo)
+ : CancelableRunnable("AsyncEventDispatcher"),
+ mTarget(aTarget),
+ mEvent(aEvent),
+ mEventMessage(eUnidentifiedEvent),
+ mOnlyChromeDispatch(aOnlyChromeDispatch) {
+ MOZ_ASSERT(
+ aEvent->IsSafeToBeDispatchedAsynchronously(),
+ "The DOM event should be created without Widget*Event and "
+ "Internal*Event "
+ "because if it needs to be safe to be dispatched asynchronously");
+ }
+
+ AsyncEventDispatcher(dom::EventTarget* aTarget, WidgetEvent& aEvent);
+
+ MOZ_CAN_RUN_SCRIPT_BOUNDARY NS_IMETHOD Run() override;
+ nsresult Cancel() override;
+ nsresult PostDOMEvent();
+
+ /**
+ * Dispatch event immediately if it's safe to dispatch the event.
+ * Otherwise, posting the event into the queue to dispatch it when it's safe.
+ *
+ * Note that this method allows callers to call itself with unsafe aTarget
+ * because its lifetime is guaranteed by this method (in the case of
+ * synchronous dispatching) or AsyncEventDispatcher (in the case of
+ * asynchronous dispatching).
+ */
+ MOZ_CAN_RUN_SCRIPT_BOUNDARY static void RunDOMEventWhenSafe(
+ dom::EventTarget& aTarget, const nsAString& aEventType,
+ CanBubble aCanBubble,
+ ChromeOnlyDispatch aOnlyChromeDispatch = ChromeOnlyDispatch::eNo,
+ Composed aComposed = Composed::eDefault);
+
+ /**
+ * Dispatch event immediately if it's safe to dispatch the event.
+ * Otherwise, posting the event into the queue to dispatch it when it's safe.
+ *
+ * NOTE: Only this is now marked as MOZ_CAN_RUN_SCRIPT because all callers
+ * have already had safe smart pointers for both aTarget and aEvent.
+ * If you need to use this in a hot path without smart pointers, you may need
+ * to create unsafe version of this method for avoiding the extra add/release
+ * refcount cost in the case of asynchronous dispatching.
+ */
+ MOZ_CAN_RUN_SCRIPT static void RunDOMEventWhenSafe(
+ dom::EventTarget& aTarget, dom::Event& aEvent,
+ ChromeOnlyDispatch aOnlyChromeDispatch = ChromeOnlyDispatch::eNo);
+
+ /**
+ * Dispatch event immediately if it's safe to dispatch the event.
+ * Otherwise, posting the event into the queue to dispatch it when it's safe.
+ *
+ * Note that this method allows callers to call itself with unsafe aTarget
+ * because its lifetime is guaranteed by EventDispatcher (in the case of
+ * synchronous dispatching) or AsyncEventDispatcher (in the case of
+ * asynchronous dispatching).
+ */
+ MOZ_CAN_RUN_SCRIPT_BOUNDARY static nsresult RunDOMEventWhenSafe(
+ nsINode& aTarget, WidgetEvent& aEvent,
+ nsEventStatus* aEventStatus = nullptr);
+
+ // Calling this causes the Run() method to check that
+ // mTarget->IsInComposedDoc(). mTarget must be an nsINode or else we'll
+ // assert.
+ void RequireNodeInDocument();
+
+ protected:
+ void RunDOMEventWhenSafe();
+ MOZ_CAN_RUN_SCRIPT static void DispatchEventOnTarget(
+ dom::EventTarget* aTarget, dom::Event* aEvent,
+ ChromeOnlyDispatch aOnlyChromeDispatch, Composed aComposed);
+ MOZ_CAN_RUN_SCRIPT static void DispatchEventOnTarget(
+ dom::EventTarget* aTarget, const nsAString& aEventType,
+ CanBubble aCanBubble, ChromeOnlyDispatch aOnlyChromeDispatch,
+ Composed aComposed);
+
+ public:
+ nsCOMPtr<dom::EventTarget> mTarget;
+ RefPtr<dom::Event> mEvent;
+ // If mEventType is set, mEventMessage will be eUnidentifiedEvent.
+ // If mEventMessage is set, mEventType will be void.
+ // They can never both be set at the same time.
+ nsString mEventType;
+ EventMessage mEventMessage;
+ CanBubble mCanBubble = CanBubble::eNo;
+ ChromeOnlyDispatch mOnlyChromeDispatch = ChromeOnlyDispatch::eNo;
+ Composed mComposed = Composed::eDefault;
+ bool mCanceled = false;
+ bool mCheckStillInDoc = false;
+};
+
+class LoadBlockingAsyncEventDispatcher final : public AsyncEventDispatcher {
+ public:
+ LoadBlockingAsyncEventDispatcher(nsINode* aEventNode,
+ const nsAString& aEventType,
+ CanBubble aBubbles,
+ ChromeOnlyDispatch aDispatchChromeOnly)
+ : AsyncEventDispatcher(aEventNode, aEventType, aBubbles,
+ aDispatchChromeOnly),
+ mBlockedDoc(aEventNode->OwnerDoc()) {
+ if (mBlockedDoc) {
+ mBlockedDoc->BlockOnload();
+ }
+ }
+
+ LoadBlockingAsyncEventDispatcher(nsINode* aEventNode, dom::Event* aEvent)
+ : AsyncEventDispatcher(aEventNode, aEvent),
+ mBlockedDoc(aEventNode->OwnerDoc()) {
+ if (mBlockedDoc) {
+ mBlockedDoc->BlockOnload();
+ }
+ }
+
+ ~LoadBlockingAsyncEventDispatcher();
+
+ private:
+ RefPtr<dom::Document> mBlockedDoc;
+};
+
+} // namespace mozilla
+
+#endif // mozilla_AsyncEventDispatcher_h_
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