Source/WebCore/dom/CustomElementReactionQueue.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2015, 2016 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "CustomElementReactionQueue.h"

 #include "CustomElementRegistry.h"
 #include "DOMWindow.h"
 #include "Document.h"
 #include "Element.h"
 #include "HTMLNames.h"
 #include "JSCustomElementInterface.h"
 #include "JSDOMBinding.h"
 #include "Microtasks.h"
 #include <JavaScriptCore/CatchScope.h>
 #include <JavaScriptCore/Heap.h>
 #include <wtf/NeverDestroyed.h>
 #include <wtf/Optional.h>
 #include <wtf/Ref.h>
 #include <wtf/SetForScope.h>

 namespace WebCore {

 class CustomElementReactionQueueItem {
 public:
     enum class Type {
         ElementUpgrade,
         Connected,
         Disconnected,
         Adopted,
         AttributeChanged,
     };

     CustomElementReactionQueueItem(Type type)
         : m_type(type)
     { }

     CustomElementReactionQueueItem(Document& oldDocument, Document& newDocument)
         : m_type(Type::Adopted)
         , m_oldDocument(&oldDocument)
         , m_newDocument(&newDocument)
     { }

     CustomElementReactionQueueItem(const QualifiedName& attributeName, const AtomString& oldValue, const AtomString& newValue)
         : m_type(Type::AttributeChanged)
         , m_attributeName(attributeName)
         , m_oldValue(oldValue)
         , m_newValue(newValue)
     { }

     Type type() const { return m_type; }

     void invoke(Element& element, JSCustomElementInterface& elementInterface)
     {
         switch (m_type) {
         case Type::ElementUpgrade:
             elementInterface.upgradeElement(element);
             break;
         case Type::Connected:
             elementInterface.invokeConnectedCallback(element);
             break;
         case Type::Disconnected:
             elementInterface.invokeDisconnectedCallback(element);
             break;
         case Type::Adopted:
             elementInterface.invokeAdoptedCallback(element, *m_oldDocument, *m_newDocument);
             break;
         case Type::AttributeChanged:
             ASSERT(m_attributeName);
             elementInterface.invokeAttributeChangedCallback(element, m_attributeName.value(), m_oldValue, m_newValue);
             break;
         }
     }

 private:
     Type m_type;
     RefPtr<Document> m_oldDocument;
     RefPtr<Document> m_newDocument;
     Optional<QualifiedName> m_attributeName;
     AtomString m_oldValue;
     AtomString m_newValue;
 };

 CustomElementReactionQueue::CustomElementReactionQueue(JSCustomElementInterface& elementInterface)
     : m_interface(elementInterface)
 { }

 CustomElementReactionQueue::~CustomElementReactionQueue()
 {
     ASSERT(m_items.isEmpty());
 }

 void CustomElementReactionQueue::clear()
 {
     m_items.clear();
 }

 void CustomElementReactionQueue::enqueueElementUpgrade(Element& element, bool alreadyScheduledToUpgrade)
 {
     ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
     ASSERT(element.reactionQueue());
     auto& queue = *element.reactionQueue();
     if (alreadyScheduledToUpgrade) {
         ASSERT(queue.m_items.size() == 1);
         ASSERT(queue.m_items[0].type() == CustomElementReactionQueueItem::Type::ElementUpgrade);
     } else {
         queue.m_items.append({CustomElementReactionQueueItem::Type::ElementUpgrade});
         enqueueElementOnAppropriateElementQueue(element);
     }
 }

 void CustomElementReactionQueue::enqueueElementUpgradeIfDefined(Element& element)
 {
     ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
     ASSERT(element.isCustomElementUpgradeCandidate());
     auto* window = element.document().domWindow();
     if (!window)
         return;

     auto* registry = window->customElementRegistry();
     if (!registry)
         return;

     auto* elementInterface = registry->findInterface(element);
     if (!elementInterface)
         return;

     element.enqueueToUpgrade(*elementInterface);
 }

 void CustomElementReactionQueue::enqueueConnectedCallbackIfNeeded(Element& element)
 {
     ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
     ASSERT(element.isDefinedCustomElement());
     ASSERT(element.document().refCount() > 0);
     ASSERT(element.reactionQueue());
     auto& queue = *element.reactionQueue();
     if (!queue.m_interface->hasConnectedCallback())
         return;
     queue.m_items.append({CustomElementReactionQueueItem::Type::Connected});
     enqueueElementOnAppropriateElementQueue(element);
 }

 void CustomElementReactionQueue::enqueueDisconnectedCallbackIfNeeded(Element& element)
 {
     ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
     ASSERT(element.isDefinedCustomElement());
     if (element.document().refCount() <= 0)
         return; // Don't enqueue disconnectedCallback if the entire document is getting destructed.
     ASSERT(element.reactionQueue());
     auto& queue = *element.reactionQueue();
     if (!queue.m_interface->hasDisconnectedCallback())
         return;
     queue.m_items.append({CustomElementReactionQueueItem::Type::Disconnected});
     enqueueElementOnAppropriateElementQueue(element);
 }

 void CustomElementReactionQueue::enqueueAdoptedCallbackIfNeeded(Element& element, Document& oldDocument, Document& newDocument)
 {
     ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
     ASSERT(element.isDefinedCustomElement());
     ASSERT(element.document().refCount() > 0);
     ASSERT(element.reactionQueue());
     auto& queue = *element.reactionQueue();
     if (!queue.m_interface->hasAdoptedCallback())
         return;
     queue.m_items.append({oldDocument, newDocument});
     enqueueElementOnAppropriateElementQueue(element);
 }

 void CustomElementReactionQueue::enqueueAttributeChangedCallbackIfNeeded(Element& element, const QualifiedName& attributeName, const AtomString& oldValue, const AtomString& newValue)
 {
     ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
     ASSERT(element.isDefinedCustomElement());
     ASSERT(element.document().refCount() > 0);
     ASSERT(element.reactionQueue());
     auto& queue = *element.reactionQueue();
     if (!queue.m_interface->observesAttribute(attributeName.localName()))
         return;
     queue.m_items.append({attributeName, oldValue, newValue});
     enqueueElementOnAppropriateElementQueue(element);
 }

 void CustomElementReactionQueue::enqueuePostUpgradeReactions(Element& element)
 {
     ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
     ASSERT(element.isCustomElementUpgradeCandidate());
     if (!element.hasAttributes() && !element.isConnected())
         return;

     ASSERT(element.reactionQueue());
     auto& queue = *element.reactionQueue();

     if (element.hasAttributes()) {
         for (auto& attribute : element.attributesIterator()) {
             if (queue.m_interface->observesAttribute(attribute.localName()))
                 queue.m_items.append({attribute.name(), nullAtom(), attribute.value()});
         }
     }

     if (element.isConnected() && queue.m_interface->hasConnectedCallback())
         queue.m_items.append({CustomElementReactionQueueItem::Type::Connected});
 }

 bool CustomElementReactionQueue::observesStyleAttribute() const
 {
     return m_interface->observesAttribute(HTMLNames::styleAttr->localName());
 }

 void CustomElementReactionQueue::invokeAll(Element& element)
 {
     while (!m_items.isEmpty()) {
         Vector<CustomElementReactionQueueItem> items = WTFMove(m_items);
         for (auto& item : items)
             item.invoke(element, m_interface.get());
     }
 }

 inline void CustomElementReactionQueue::ElementQueue::add(Element& element)
 {
     ASSERT(!m_invoking);
     // FIXME: Avoid inserting the same element multiple times.
     m_elements.append(element);
 }

 inline void CustomElementReactionQueue::ElementQueue::invokeAll()
 {
     RELEASE_ASSERT(!m_invoking);
     SetForScope<bool> invoking(m_invoking, true);
     unsigned originalSize = m_elements.size();
     // It's possible for more elements to be enqueued if some IDL attributes were missing CEReactions.
     // Invoke callbacks slightly later here instead of crashing / ignoring those cases.
     for (unsigned i = 0; i < m_elements.size(); ++i) {
         auto& element = m_elements[i].get();
         auto* queue = element.reactionQueue();
         ASSERT(queue);
         queue->invokeAll(element);
     }
     ASSERT_UNUSED(originalSize, m_elements.size() == originalSize);
     m_elements.clear();
 }

 inline void CustomElementReactionQueue::ElementQueue::processQueue(JSC::ExecState* state)
 {
     if (!state) {
         invokeAll();
         return;
     }

     auto& vm = state->vm();
     JSC::JSLockHolder lock(vm);

     JSC::Exception* previousException = nullptr;
     {
         auto catchScope = DECLARE_CATCH_SCOPE(vm);
         previousException = catchScope.exception();
         if (previousException)
             catchScope.clearException();
     }

     invokeAll();

     if (previousException) {
         auto throwScope = DECLARE_THROW_SCOPE(vm);
         throwException(state, throwScope, previousException);
     }
 }

 // https://html.spec.whatwg.org/multipage/custom-elements.html#enqueue-an-element-on-the-appropriate-element-queue
 void CustomElementReactionQueue::enqueueElementOnAppropriateElementQueue(Element& element)
 {
     ASSERT(element.reactionQueue());
     if (!CustomElementReactionStack::s_currentProcessingStack) {
         auto& queue = ensureBackupQueue();
         queue.add(element);
         return;
     }

     auto*& queue = CustomElementReactionStack::s_currentProcessingStack->m_queue;
     if (!queue) // We use a raw pointer to avoid genearing code to delete it in ~CustomElementReactionStack.
         queue = new ElementQueue;
     queue->add(element);
 }

 #if !ASSERT_DISABLED
 unsigned CustomElementReactionDisallowedScope::s_customElementReactionDisallowedCount = 0;
 #endif

 CustomElementReactionStack* CustomElementReactionStack::s_currentProcessingStack = nullptr;

 void CustomElementReactionStack::processQueue(JSC::ExecState* state)
 {
     ASSERT(m_queue);
     m_queue->processQueue(state);
     delete m_queue;
     m_queue = nullptr;
 }

 class BackupElementQueueMicrotask final : public Microtask {
     WTF_MAKE_FAST_ALLOCATED;
 private:
     Result run() final
     {
         CustomElementReactionQueue::processBackupQueue();
         return Result::Done;
     }
 };

 static bool s_processingBackupElementQueue = false;

 CustomElementReactionQueue::ElementQueue& CustomElementReactionQueue::ensureBackupQueue()
 {
     if (!s_processingBackupElementQueue) {
         s_processingBackupElementQueue = true;
         MicrotaskQueue::mainThreadQueue().append(makeUnique<BackupElementQueueMicrotask>());
     }
     return backupElementQueue();
 }

 void CustomElementReactionQueue::processBackupQueue()
 {
     backupElementQueue().processQueue(nullptr);
     s_processingBackupElementQueue = false;
 }

 CustomElementReactionQueue::ElementQueue& CustomElementReactionQueue::backupElementQueue()
 {
     static NeverDestroyed<ElementQueue> queue;
     return queue.get();
 }

 }
	/*
	* Copyright (C) 2015, 2016 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
	* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
	* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
	* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
	* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
	* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
	* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
	* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "CustomElementReactionQueue.h"

	#include "CustomElementRegistry.h"
	#include "DOMWindow.h"
	#include "Document.h"
	#include "Element.h"
	#include "HTMLNames.h"
	#include "JSCustomElementInterface.h"
	#include "JSDOMBinding.h"
	#include "Microtasks.h"
	#include <JavaScriptCore/CatchScope.h>
	#include <JavaScriptCore/Heap.h>
	#include <wtf/NeverDestroyed.h>
	#include <wtf/Optional.h>
	#include <wtf/Ref.h>
	#include <wtf/SetForScope.h>

	namespace WebCore {

	class CustomElementReactionQueueItem {
	public:
	enum class Type {
	ElementUpgrade,
	Connected,
	Disconnected,
	Adopted,
	AttributeChanged,
	};

	CustomElementReactionQueueItem(Type type)
	: m_type(type)
	{ }

	CustomElementReactionQueueItem(Document& oldDocument, Document& newDocument)
	: m_type(Type::Adopted)
	, m_oldDocument(&oldDocument)
	, m_newDocument(&newDocument)
	{ }

	CustomElementReactionQueueItem(const QualifiedName& attributeName, const AtomString& oldValue, const AtomString& newValue)
	: m_type(Type::AttributeChanged)
	, m_attributeName(attributeName)
	, m_oldValue(oldValue)
	, m_newValue(newValue)
	{ }

	Type type() const { return m_type; }

	void invoke(Element& element, JSCustomElementInterface& elementInterface)
	{
	switch (m_type) {
	case Type::ElementUpgrade:
	elementInterface.upgradeElement(element);
	break;
	case Type::Connected:
	elementInterface.invokeConnectedCallback(element);
	break;
	case Type::Disconnected:
	elementInterface.invokeDisconnectedCallback(element);
	break;
	case Type::Adopted:
	elementInterface.invokeAdoptedCallback(element, m_oldDocument, m_newDocument);
	break;
	case Type::AttributeChanged:
	ASSERT(m_attributeName);
	elementInterface.invokeAttributeChangedCallback(element, m_attributeName.value(), m_oldValue, m_newValue);
	break;
	}
	}

	private:
	Type m_type;
	RefPtr<Document> m_oldDocument;
	RefPtr<Document> m_newDocument;
	Optional<QualifiedName> m_attributeName;
	AtomString m_oldValue;
	AtomString m_newValue;
	};

	CustomElementReactionQueue::CustomElementReactionQueue(JSCustomElementInterface& elementInterface)
	: m_interface(elementInterface)
	{ }

	CustomElementReactionQueue::~CustomElementReactionQueue()
	{
	ASSERT(m_items.isEmpty());
	}

	void CustomElementReactionQueue::clear()
	{
	m_items.clear();
	}

	void CustomElementReactionQueue::enqueueElementUpgrade(Element& element, bool alreadyScheduledToUpgrade)
	{
	ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
	ASSERT(element.reactionQueue());
	auto& queue = *element.reactionQueue();
	if (alreadyScheduledToUpgrade) {
	ASSERT(queue.m_items.size() == 1);
	ASSERT(queue.m_items[0].type() == CustomElementReactionQueueItem::Type::ElementUpgrade);
	} else {
	queue.m_items.append({CustomElementReactionQueueItem::Type::ElementUpgrade});
	enqueueElementOnAppropriateElementQueue(element);
	}
	}

	void CustomElementReactionQueue::enqueueElementUpgradeIfDefined(Element& element)
	{
	ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
	ASSERT(element.isCustomElementUpgradeCandidate());
	auto* window = element.document().domWindow();
	if (!window)
	return;

	auto* registry = window->customElementRegistry();
	if (!registry)
	return;

	auto* elementInterface = registry->findInterface(element);
	if (!elementInterface)
	return;

	element.enqueueToUpgrade(*elementInterface);
	}

	void CustomElementReactionQueue::enqueueConnectedCallbackIfNeeded(Element& element)
	{
	ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
	ASSERT(element.isDefinedCustomElement());
	ASSERT(element.document().refCount() > 0);
	ASSERT(element.reactionQueue());
	auto& queue = *element.reactionQueue();
	if (!queue.m_interface->hasConnectedCallback())
	return;
	queue.m_items.append({CustomElementReactionQueueItem::Type::Connected});
	enqueueElementOnAppropriateElementQueue(element);
	}

	void CustomElementReactionQueue::enqueueDisconnectedCallbackIfNeeded(Element& element)
	{
	ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
	ASSERT(element.isDefinedCustomElement());
	if (element.document().refCount() <= 0)
	return; // Don't enqueue disconnectedCallback if the entire document is getting destructed.
	ASSERT(element.reactionQueue());
	auto& queue = *element.reactionQueue();
	if (!queue.m_interface->hasDisconnectedCallback())
	return;
	queue.m_items.append({CustomElementReactionQueueItem::Type::Disconnected});
	enqueueElementOnAppropriateElementQueue(element);
	}

	void CustomElementReactionQueue::enqueueAdoptedCallbackIfNeeded(Element& element, Document& oldDocument, Document& newDocument)
	{
	ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
	ASSERT(element.isDefinedCustomElement());
	ASSERT(element.document().refCount() > 0);
	ASSERT(element.reactionQueue());
	auto& queue = *element.reactionQueue();
	if (!queue.m_interface->hasAdoptedCallback())
	return;
	queue.m_items.append({oldDocument, newDocument});
	enqueueElementOnAppropriateElementQueue(element);
	}

	void CustomElementReactionQueue::enqueueAttributeChangedCallbackIfNeeded(Element& element, const QualifiedName& attributeName, const AtomString& oldValue, const AtomString& newValue)
	{
	ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
	ASSERT(element.isDefinedCustomElement());
	ASSERT(element.document().refCount() > 0);
	ASSERT(element.reactionQueue());
	auto& queue = *element.reactionQueue();
	if (!queue.m_interface->observesAttribute(attributeName.localName()))
	return;
	queue.m_items.append({attributeName, oldValue, newValue});
	enqueueElementOnAppropriateElementQueue(element);
	}

	void CustomElementReactionQueue::enqueuePostUpgradeReactions(Element& element)
	{
	ASSERT(CustomElementReactionDisallowedScope::isReactionAllowed());
	ASSERT(element.isCustomElementUpgradeCandidate());
	if (!element.hasAttributes() && !element.isConnected())
	return;

	ASSERT(element.reactionQueue());
	auto& queue = *element.reactionQueue();

	if (element.hasAttributes()) {
	for (auto& attribute : element.attributesIterator()) {
	if (queue.m_interface->observesAttribute(attribute.localName()))
	queue.m_items.append({attribute.name(), nullAtom(), attribute.value()});
	}
	}

	if (element.isConnected() && queue.m_interface->hasConnectedCallback())
	queue.m_items.append({CustomElementReactionQueueItem::Type::Connected});
	}

	bool CustomElementReactionQueue::observesStyleAttribute() const
	{
	return m_interface->observesAttribute(HTMLNames::styleAttr->localName());
	}

	void CustomElementReactionQueue::invokeAll(Element& element)
	{
	while (!m_items.isEmpty()) {
	Vector<CustomElementReactionQueueItem> items = WTFMove(m_items);
	for (auto& item : items)
	item.invoke(element, m_interface.get());
	}
	}

	inline void CustomElementReactionQueue::ElementQueue::add(Element& element)
	{
	ASSERT(!m_invoking);
	// FIXME: Avoid inserting the same element multiple times.
	m_elements.append(element);
	}

	inline void CustomElementReactionQueue::ElementQueue::invokeAll()
	{
	RELEASE_ASSERT(!m_invoking);
	SetForScope<bool> invoking(m_invoking, true);
	unsigned originalSize = m_elements.size();
	// It's possible for more elements to be enqueued if some IDL attributes were missing CEReactions.
	// Invoke callbacks slightly later here instead of crashing / ignoring those cases.
	for (unsigned i = 0; i < m_elements.size(); ++i) {
	auto& element = m_elements[i].get();
	auto* queue = element.reactionQueue();
	ASSERT(queue);
	queue->invokeAll(element);
	}
	ASSERT_UNUSED(originalSize, m_elements.size() == originalSize);
	m_elements.clear();
	}

	inline void CustomElementReactionQueue::ElementQueue::processQueue(JSC::ExecState* state)
	{
	if (!state) {
	invokeAll();
	return;
	}

	auto& vm = state->vm();
	JSC::JSLockHolder lock(vm);

	JSC::Exception* previousException = nullptr;
	{
	auto catchScope = DECLARE_CATCH_SCOPE(vm);
	previousException = catchScope.exception();
	if (previousException)
	catchScope.clearException();
	}

	invokeAll();

	if (previousException) {
	auto throwScope = DECLARE_THROW_SCOPE(vm);
	throwException(state, throwScope, previousException);
	}
	}

	// https://html.spec.whatwg.org/multipage/custom-elements.html#enqueue-an-element-on-the-appropriate-element-queue
	void CustomElementReactionQueue::enqueueElementOnAppropriateElementQueue(Element& element)
	{
	ASSERT(element.reactionQueue());
	if (!CustomElementReactionStack::s_currentProcessingStack) {
	auto& queue = ensureBackupQueue();
	queue.add(element);
	return;
	}

	auto*& queue = CustomElementReactionStack::s_currentProcessingStack->m_queue;
	if (!queue) // We use a raw pointer to avoid genearing code to delete it in ~CustomElementReactionStack.
	queue = new ElementQueue;
	queue->add(element);
	}

	#if !ASSERT_DISABLED
	unsigned CustomElementReactionDisallowedScope::s_customElementReactionDisallowedCount = 0;
	#endif

	CustomElementReactionStack* CustomElementReactionStack::s_currentProcessingStack = nullptr;

	void CustomElementReactionStack::processQueue(JSC::ExecState* state)
	{
	ASSERT(m_queue);
	m_queue->processQueue(state);
	delete m_queue;
	m_queue = nullptr;
	}

	class BackupElementQueueMicrotask final : public Microtask {
	WTF_MAKE_FAST_ALLOCATED;
	private:
	Result run() final
	{
	CustomElementReactionQueue::processBackupQueue();
	return Result::Done;
	}
	};

	static bool s_processingBackupElementQueue = false;

	CustomElementReactionQueue::ElementQueue& CustomElementReactionQueue::ensureBackupQueue()
	{
	if (!s_processingBackupElementQueue) {
	s_processingBackupElementQueue = true;
	MicrotaskQueue::mainThreadQueue().append(makeUnique<BackupElementQueueMicrotask>());
	}
	return backupElementQueue();
	}

	void CustomElementReactionQueue::processBackupQueue()
	{
	backupElementQueue().processQueue(nullptr);
	s_processingBackupElementQueue = false;
	}

	CustomElementReactionQueue::ElementQueue& CustomElementReactionQueue::backupElementQueue()
	{
	static NeverDestroyed<ElementQueue> queue;
	return queue.get();
	}

	}