/*
 * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
 *           (C) 1999 Antti Koivisto (koivisto@kde.org)
 *           (C) 2001 Dirk Mueller (mueller@kde.org)
 *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
 * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
 * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
 * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
 * Copyright (C) 2011 Google Inc. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#ifndef Document_h
#define Document_h

#include "bindings/core/v8/ExceptionStatePlaceholder.h"
#include "bindings/core/v8/ScriptValue.h"
#include "core/CoreExport.h"
#include "core/dom/ContainerNode.h"
#include "core/dom/DocumentEncodingData.h"
#include "core/dom/DocumentInit.h"
#include "core/dom/DocumentLifecycle.h"
#include "core/dom/DocumentTiming.h"
#include "core/dom/ExecutionContext.h"
#include "core/dom/MutationObserver.h"
#include "core/dom/TextLinkColors.h"
#include "core/dom/TreeScope.h"
#include "core/dom/UserActionElementSet.h"
#include "core/dom/ViewportDescription.h"
#include "core/dom/custom/V0CustomElement.h"
#include "core/fetch/ClientHintsPreferences.h"
#include "core/frame/DOMTimerCoordinator.h"
#include "core/frame/HostsUsingFeatures.h"
#include "core/html/parser/ParserSynchronizationPolicy.h"
#include "core/page/PageVisibilityState.h"
#include "platform/Length.h"
#include "platform/Timer.h"
#include "platform/weborigin/KURL.h"
#include "platform/weborigin/ReferrerPolicy.h"
#include "public/platform/WebFocusType.h"
#include "wtf/HashSet.h"
#include "wtf/OwnPtr.h"
#include "wtf/PassOwnPtr.h"
#include "wtf/PassRefPtr.h"

namespace blink {

class AnimationClock;
class AnimationTimeline;
class AXObjectCache;
class Attr;
class CDATASection;
class CSSStyleDeclaration;
class CSSStyleSheet;
class CancellableTaskFactory;
class CanvasFontCache;
class CanvasRenderingContext2D;
class CanvasRenderingContext2DOrWebGLRenderingContext;
class CharacterData;
class ChromeClient;
class CompositorPendingAnimations;
class Comment;
class ConsoleMessage;
class ContextFeatures;
class V0CustomElementMicrotaskRunQueue;
class V0CustomElementRegistrationContext;
class DOMImplementation;
class DOMWindow;
class DocumentFragment;
class DocumentLoader;
class DocumentMarkerController;
class DocumentNameCollection;
class DocumentParser;
class DocumentState;
class DocumentType;
class Element;
class ElementDataCache;
class ElementRegistrationOptions;
class Event;
class EventFactoryBase;
class EventListener;
template <typename EventType>
class EventWithHitTestResults;
class ExceptionState;
class FloatQuad;
class FloatRect;
class FormController;
class Frame;
class FrameHost;
class FrameRequestCallback;
class FrameView;
class HTMLAllCollection;
class HTMLBodyElement;
class HTMLCanvasElement;
class HTMLCollection;
class HTMLDialogElement;
class HTMLElement;
class HTMLFrameOwnerElement;
class HTMLHeadElement;
class HTMLImportLoader;
class HTMLImportsController;
class HTMLLinkElement;
class HTMLScriptElementOrSVGScriptElement;
class HitTestRequest;
class IdleRequestCallback;
class IdleRequestOptions;
class InputDeviceCapabilities;
class IntersectionObserverController;
class LayoutPoint;
class LayoutView;
class LayoutViewItem;
class LiveNodeListBase;
class LocalDOMWindow;
class Locale;
class LocalFrame;
class Location;
class MainThreadTaskRunner;
class MediaQueryListListener;
class MediaQueryMatcher;
class NodeFilter;
class NodeIntersectionObserverData;
class NodeIterator;
class NthIndexCache;
class OriginAccessEntry;
class Page;
class PlatformMouseEvent;
class ProcessingInstruction;
class QualifiedName;
class Range;
class ResourceFetcher;
class RootScrollerController;
class SVGDocumentExtensions;
class SVGUseElement;
class ScriptRunner;
class ScriptableDocumentParser;
class ScriptedAnimationController;
class ScriptedIdleTaskController;
class SecurityOrigin;
class SegmentedString;
class SelectorQueryCache;
class SerializedScriptValue;
class Settings;
class SnapCoordinator;
class StyleEngine;
class StyleResolver;
class StyleSheet;
class StyleSheetList;
class Text;
class TextAutosizer;
class Touch;
class TouchList;
class TransformSource;
class TreeWalker;
class VisitedLinkState;
class VisualViewport;
class WebGLRenderingContext;
enum class SelectionBehaviorOnFocus;
struct AnnotatedRegionValue;
struct FocusParams;
struct IconURL;

using MouseEventWithHitTestResults = EventWithHitTestResults<PlatformMouseEvent>;
using ExceptionCode = int;

enum StyleResolverUpdateMode {
    // Discards the StyleResolver and rebuilds it.
    FullStyleUpdate,
    // Attempts to use StyleInvalidationAnalysis to avoid discarding the entire StyleResolver.
    AnalyzedStyleUpdate
};

enum NodeListInvalidationType {
    DoNotInvalidateOnAttributeChanges = 0,
    InvalidateOnClassAttrChange,
    InvalidateOnIdNameAttrChange,
    InvalidateOnNameAttrChange,
    InvalidateOnForAttrChange,
    InvalidateForFormControls,
    InvalidateOnHRefAttrChange,
    InvalidateOnAnyAttrChange,
};
const int numNodeListInvalidationTypes = InvalidateOnAnyAttrChange + 1;

enum DocumentClass {
    DefaultDocumentClass = 0,
    HTMLDocumentClass = 1,
    XHTMLDocumentClass = 1 << 1,
    ImageDocumentClass = 1 << 2,
    PluginDocumentClass = 1 << 3,
    MediaDocumentClass = 1 << 4,
    SVGDocumentClass = 1 << 5,
    XMLDocumentClass = 1 << 6,
};

enum ShadowCascadeOrder {
    ShadowCascadeNone,
    ShadowCascadeV0,
    ShadowCascadeV1
};

enum CreateElementFlags {
    CreatedByParser = 1 << 0,
    // Synchronous custom elements flag:
    // https://dom.spec.whatwg.org/#concept-create-element
    SynchronousCustomElements = 0 << 1,
    AsynchronousCustomElements = 1 << 1,

    // Aliases by callers.
    // Clone a node: https://dom.spec.whatwg.org/#concept-node-clone
    CreatedByCloneNode = AsynchronousCustomElements,
    CreatedByImportNode = CreatedByCloneNode,
    // https://dom.spec.whatwg.org/#dom-document-createelement
    CreatedByCreateElement = SynchronousCustomElements,
    // https://html.spec.whatwg.org/#create-an-element-for-the-token
    CreatedByFragmentParser = CreatedByParser | AsynchronousCustomElements,
};

using DocumentClassFlags = unsigned char;

class CORE_EXPORT Document : public ContainerNode, public TreeScope, public SecurityContext, public ExecutionContext, public Supplementable<Document> {
    DEFINE_WRAPPERTYPEINFO();
    USING_GARBAGE_COLLECTED_MIXIN(Document);
public:
    static Document* create(const DocumentInit& initializer = DocumentInit())
    {
        return new Document(initializer);
    }
    ~Document() override;

    MediaQueryMatcher& mediaQueryMatcher();

    void mediaQueryAffectingValueChanged();

    using SecurityContext::getSecurityOrigin;
    using SecurityContext::contentSecurityPolicy;
    using TreeScope::getElementById;

    bool canContainRangeEndPoint() const override { return true; }

    SelectorQueryCache& selectorQueryCache();

    // Focus Management.
    Element* activeElement() const;
    bool hasFocus() const;

    // DOM methods & attributes for Document

    DEFINE_ATTRIBUTE_EVENT_LISTENER(beforecopy);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(beforecut);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(beforepaste);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(copy);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(cut);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(paste);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(pointerlockchange);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(pointerlockerror);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(readystatechange);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(search);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(securitypolicyviolation);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(selectionchange);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(selectstart);
    DEFINE_ATTRIBUTE_EVENT_LISTENER(wheel);

    bool shouldMergeWithLegacyDescription(ViewportDescription::Type) const;
    bool shouldOverrideLegacyDescription(ViewportDescription::Type) const;
    void setViewportDescription(const ViewportDescription&);
    ViewportDescription viewportDescription() const;
    Length viewportDefaultMinWidth() const { return m_viewportDefaultMinWidth; }

    String outgoingReferrer() const override;

    void setDoctype(DocumentType*);
    DocumentType* doctype() const { return m_docType.get(); }

    DOMImplementation& implementation();

    Element* documentElement() const
    {
        return m_documentElement.get();
    }

    // Returns whether the Document has an AppCache manifest.
    bool hasAppCacheManifest() const;

    Location* location() const;

    Element* createElement(const AtomicString& name, ExceptionState&);
    DocumentFragment* createDocumentFragment();
    Text* createTextNode(const String& data);
    Comment* createComment(const String& data);
    CDATASection* createCDATASection(const String& data, ExceptionState&);
    ProcessingInstruction* createProcessingInstruction(const String& target, const String& data, ExceptionState&);
    Attr* createAttribute(const AtomicString& name, ExceptionState&);
    Attr* createAttributeNS(const AtomicString& namespaceURI, const AtomicString& qualifiedName, ExceptionState&, bool shouldIgnoreNamespaceChecks = false);
    Node* importNode(Node* importedNode, bool deep, ExceptionState&);
    Element* createElementNS(const AtomicString& namespaceURI, const AtomicString& qualifiedName, ExceptionState&);
    Element* createElement(const QualifiedName&, CreateElementFlags);

    Element* elementFromPoint(int x, int y) const;
    HeapVector<Member<Element>> elementsFromPoint(int x, int y) const;
    Range* caretRangeFromPoint(int x, int y);
    Element* scrollingElement();

    String readyState() const;

    AtomicString characterSet() const { return Document::encodingName(); }

    AtomicString encodingName() const;

    void setContent(const String&);

    String suggestedMIMEType() const;
    void setMimeType(const AtomicString&);
    AtomicString contentType() const; // DOM 4 document.contentType

    const AtomicString& contentLanguage() const { return m_contentLanguage; }
    void setContentLanguage(const AtomicString&);

    String xmlEncoding() const { return m_xmlEncoding; }
    String xmlVersion() const { return m_xmlVersion; }
    enum StandaloneStatus { StandaloneUnspecified, Standalone, NotStandalone };
    bool xmlStandalone() const { return m_xmlStandalone == Standalone; }
    StandaloneStatus xmlStandaloneStatus() const { return static_cast<StandaloneStatus>(m_xmlStandalone); }
    bool hasXMLDeclaration() const { return m_hasXMLDeclaration; }

    void setXMLEncoding(const String& encoding) { m_xmlEncoding = encoding; } // read-only property, only to be set from XMLDocumentParser
    void setXMLVersion(const String&, ExceptionState&);
    void setXMLStandalone(bool, ExceptionState&);
    void setHasXMLDeclaration(bool hasXMLDeclaration) { m_hasXMLDeclaration = hasXMLDeclaration ? 1 : 0; }

    String origin() const { return getSecurityOrigin()->toString(); }
    String suborigin() const { return getSecurityOrigin()->hasSuborigin() ? getSecurityOrigin()->suborigin()->name() : String(); }

    String visibilityState() const;
    PageVisibilityState pageVisibilityState() const;
    bool hidden() const;
    void didChangeVisibilityState();

    Node* adoptNode(Node* source, ExceptionState&);

    HTMLCollection* images();
    HTMLCollection* embeds();
    HTMLCollection* applets();
    HTMLCollection* links();
    HTMLCollection* forms();
    HTMLCollection* anchors();
    HTMLCollection* scripts();
    HTMLAllCollection* allForBinding();
    HTMLAllCollection* all();

    HTMLCollection* windowNamedItems(const AtomicString& name);
    DocumentNameCollection* documentNamedItems(const AtomicString& name);

    bool isHTMLDocument() const { return m_documentClasses & HTMLDocumentClass; }
    bool isXHTMLDocument() const { return m_documentClasses & XHTMLDocumentClass; }
    bool isXMLDocument() const { return m_documentClasses & XMLDocumentClass; }
    bool isImageDocument() const { return m_documentClasses & ImageDocumentClass; }
    bool isSVGDocument() const { return m_documentClasses & SVGDocumentClass; }
    bool isPluginDocument() const { return m_documentClasses & PluginDocumentClass; }
    bool isMediaDocument() const { return m_documentClasses & MediaDocumentClass; }

    bool hasSVGRootNode() const;

    bool isFrameSet() const;

    bool isSrcdocDocument() const { return m_isSrcdocDocument; }
    bool isMobileDocument() const { return m_isMobileDocument; }

    StyleResolver* styleResolver() const;
    StyleResolver& ensureStyleResolver() const;

    bool isViewSource() const { return m_isViewSource; }
    void setIsViewSource(bool);

    bool sawElementsInKnownNamespaces() const { return m_sawElementsInKnownNamespaces; }

    bool isRenderingReady() const { return haveImportsLoaded() && haveRenderBlockingStylesheetsLoaded(); }
    bool isScriptExecutionReady() const { return haveImportsLoaded() && haveScriptBlockingStylesheetsLoaded(); }

    // This is a DOM function.
    StyleSheetList& styleSheets();

    StyleEngine& styleEngine() { DCHECK(m_styleEngine.get()); return *m_styleEngine.get(); }

    bool gotoAnchorNeededAfterStylesheetsLoad() { return m_gotoAnchorNeededAfterStylesheetsLoad; }
    void setGotoAnchorNeededAfterStylesheetsLoad(bool b) { m_gotoAnchorNeededAfterStylesheetsLoad = b; }

    void scheduleUseShadowTreeUpdate(SVGUseElement&);
    void unscheduleUseShadowTreeUpdate(SVGUseElement&);

    // FIXME: SVG filters should change to store the filter on the ComputedStyle
    // instead of the LayoutObject so we can get rid of this hack.
    void scheduleSVGFilterLayerUpdateHack(Element&);
    void unscheduleSVGFilterLayerUpdateHack(Element&);

    void evaluateMediaQueryList();

    FormController& formController();
    DocumentState* formElementsState() const;
    void setStateForNewFormElements(const Vector<String>&);

    FrameView* view() const; // can be null
    LocalFrame* frame() const { return m_frame; } // can be null
    FrameHost* frameHost() const; // can be null
    Page* page() const; // can be null
    Settings* settings() const; // can be null

    float devicePixelRatio() const;

    Range* createRange();

    NodeIterator* createNodeIterator(Node* root, unsigned whatToShow, NodeFilter*);
    TreeWalker* createTreeWalker(Node* root, unsigned whatToShow, NodeFilter*);

    // Special support for editing
    Text* createEditingTextNode(const String&);

    void setupFontBuilder(ComputedStyle& documentStyle);

    bool needsLayoutTreeUpdate() const;
    bool needsLayoutTreeUpdateForNode(const Node&) const;
    // Update ComputedStyles and attach LayoutObjects if necessary, but don't
    // lay out.
    void updateStyleAndLayoutTree();
    // Same as updateStyleAndLayoutTree() except ignoring pending stylesheets.
    void updateStyleAndLayoutTreeIgnorePendingStylesheets();
    void updateStyleAndLayoutTreeForNode(const Node*);
    void updateStyleAndLayout();
    void layoutUpdated();
    enum RunPostLayoutTasks {
        RunPostLayoutTasksAsyhnchronously,
        RunPostLayoutTasksSynchronously,
    };
    void updateStyleAndLayoutIgnorePendingStylesheets(RunPostLayoutTasks = RunPostLayoutTasksAsyhnchronously);
    void updateStyleAndLayoutIgnorePendingStylesheetsForNode(Node*);
    PassRefPtr<ComputedStyle> styleForElementIgnoringPendingStylesheets(Element*);
    PassRefPtr<ComputedStyle> styleForPage(int pageIndex);

    // Returns true if page box (margin boxes and page borders) is visible.
    bool isPageBoxVisible(int pageIndex);

    // Returns the preferred page size and margins in pixels, assuming 96
    // pixels per inch. pageSize, marginTop, marginRight, marginBottom,
    // marginLeft must be initialized to the default values that are used if
    // auto is specified.
    void pageSizeAndMarginsInPixels(int pageIndex, IntSize& pageSize, int& marginTop, int& marginRight, int& marginBottom, int& marginLeft);

    ResourceFetcher* fetcher() { return m_fetcher.get(); }

    void attach(const AttachContext& = AttachContext()) override;
    void detach(const AttachContext& = AttachContext()) override;

    // If you have a Document, use layoutView() instead which is faster.
    void layoutObject() const = delete;

    LayoutView* layoutView() const { return m_layoutView; }
    LayoutViewItem layoutViewItem() const;

    Document& axObjectCacheOwner() const;
    AXObjectCache* existingAXObjectCache() const;
    AXObjectCache* axObjectCache() const;
    void clearAXObjectCache();

    // to get visually ordered hebrew and arabic pages right
    bool visuallyOrdered() const { return m_visuallyOrdered; }

    DocumentLoader* loader() const;

    // This is the DOM API document.open(). enteredDocument is the responsible
    // document of the entry settings object.
    void open(Document* enteredDocument, ExceptionState&);
    // This is used internally and does not handle exceptions.
    void open();
    DocumentParser* implicitOpen(ParserSynchronizationPolicy);

    // This is the DOM API document.close()
    void close(ExceptionState&);
    // This is used internally and does not handle exceptions.
    void close();
    // implicitClose() actually does the work of closing the input stream.
    void implicitClose();

    bool dispatchBeforeUnloadEvent(ChromeClient&, bool isReload, bool& didAllowNavigation);
    void dispatchUnloadEvents();

    enum PageDismissalType {
        NoDismissal,
        BeforeUnloadDismissal,
        PageHideDismissal,
        UnloadVisibilityChangeDismissal,
        UnloadDismissal
    };
    PageDismissalType pageDismissalEventBeingDispatched() const;

    void cancelParsing();

    void write(const SegmentedString& text, Document* enteredDocument = nullptr, ExceptionState& = ASSERT_NO_EXCEPTION);
    void write(const String& text, Document* enteredDocument = nullptr, ExceptionState& = ASSERT_NO_EXCEPTION);
    void writeln(const String& text, Document* enteredDocument = nullptr, ExceptionState& = ASSERT_NO_EXCEPTION);
    void write(LocalDOMWindow*, const Vector<String>& text, ExceptionState&);
    void writeln(LocalDOMWindow*, const Vector<String>& text, ExceptionState&);

    bool wellFormed() const { return m_wellFormed; }

    const KURL& url() const { return m_url; }
    void setURL(const KURL&);

    // To understand how these concepts relate to one another, please see the
    // comments surrounding their declaration.
    const KURL& baseURL() const { return m_baseURL; }
    void setBaseURLOverride(const KURL&);
    const KURL& baseURLOverride() const { return m_baseURLOverride; }
    const KURL& baseElementURL() const { return m_baseElementURL; }
    const AtomicString& baseTarget() const { return m_baseTarget; }
    void processBaseElement();

    // Creates URL based on passed relative url and this documents base URL.
    // Depending on base URL value it is possible that parent document
    // base URL will be used instead. Uses completeURLWithOverride internally.
    KURL completeURL(const String&) const;
    // Creates URL based on passed relative url and passed base URL override.
    // Depending on baseURLOverride value it is possible that parent document
    // base URL will be used instead of it. See baseURLForOverride function
    // for details.
    KURL completeURLWithOverride(const String&, const KURL& baseURLOverride) const;
    // Determines which base URL should be used given specified override.
    // If override is empty or is about:blank url and parent document exists
    // base URL of parent will be returned, passed base URL override otherwise.
    const KURL& baseURLForOverride(const KURL& baseURLOverride) const;

    String userAgent() const final;
    void disableEval(const String& errorMessage) final;

    CSSStyleSheet& elementSheet();

    virtual DocumentParser* createParser();
    DocumentParser* parser() const { return m_parser.get(); }
    ScriptableDocumentParser* scriptableDocumentParser() const;

    bool printing() const { return m_printing; }
    void setPrinting(bool isPrinting) { m_printing = isPrinting; }
    bool wasPrinting() const { return m_wasPrinting; }

    bool paginatedForScreen() const { return m_paginatedForScreen; }
    void setPaginatedForScreen(bool p) { m_paginatedForScreen = p; }

    bool paginated() const { return printing() || paginatedForScreen(); }

    enum CompatibilityMode { QuirksMode, LimitedQuirksMode, NoQuirksMode };

    void setCompatibilityMode(CompatibilityMode);
    CompatibilityMode getCompatibilityMode() const { return m_compatibilityMode; }

    String compatMode() const;

    bool inQuirksMode() const { return m_compatibilityMode == QuirksMode; }
    bool inLimitedQuirksMode() const { return m_compatibilityMode == LimitedQuirksMode; }
    bool inNoQuirksMode() const { return m_compatibilityMode == NoQuirksMode; }

    enum ReadyState {
        Loading,
        Interactive,
        Complete
    };
    void setReadyState(ReadyState);
    bool isLoadCompleted();

    enum ParsingState {
        Parsing,
        InDOMContentLoaded,
        FinishedParsing
    };
    void setParsingState(ParsingState);
    bool parsing() const { return m_parsingState == Parsing; }
    bool isInDOMContentLoaded() const { return m_parsingState == InDOMContentLoaded; }
    bool hasFinishedParsing() const { return m_parsingState == FinishedParsing; }

    bool shouldScheduleLayout() const;
    int elapsedTime() const;

    TextLinkColors& textLinkColors() { return m_textLinkColors; }
    VisitedLinkState& visitedLinkState() const { return *m_visitedLinkState; }

    MouseEventWithHitTestResults prepareMouseEvent(const HitTestRequest&, const LayoutPoint&, const PlatformMouseEvent&);

    /* Newly proposed CSS3 mechanism for selecting alternate
       stylesheets using the DOM. May be subject to change as
       spec matures. - dwh
    */
    String preferredStylesheetSet() const;
    String selectedStylesheetSet() const;
    void setSelectedStylesheetSet(const String&);

    bool setFocusedElement(Element*, const FocusParams&);
    void clearFocusedElement();
    Element* focusedElement() const { return m_focusedElement.get(); }
    UserActionElementSet& userActionElements()  { return m_userActionElements; }
    const UserActionElementSet& userActionElements() const { return m_userActionElements; }
    void setNeedsFocusedElementCheck();
    void setAutofocusElement(Element*);
    Element* autofocusElement() const { return m_autofocusElement.get(); }
    void setSequentialFocusNavigationStartingPoint(Node*);
    Element* sequentialFocusNavigationStartingPoint(WebFocusType) const;

    void setActiveHoverElement(Element*);
    Element* activeHoverElement() const { return m_activeHoverElement.get(); }

    Node* hoverNode() const { return m_hoverNode.get(); }

    void removeFocusedElementOfSubtree(Node*, bool amongChildrenOnly = false);
    void hoveredNodeDetached(Element&);
    void activeChainNodeDetached(Element&);

    void updateHoverActiveState(const HitTestRequest&, Element*);

    // Updates for :target (CSS3 selector).
    void setCSSTarget(Element*);
    Element* cssTarget() const { return m_cssTarget; }

    void scheduleLayoutTreeUpdateIfNeeded();
    bool hasPendingForcedStyleRecalc() const;

    void registerNodeList(const LiveNodeListBase*);
    void unregisterNodeList(const LiveNodeListBase*);
    void registerNodeListWithIdNameCache(const LiveNodeListBase*);
    void unregisterNodeListWithIdNameCache(const LiveNodeListBase*);
    bool shouldInvalidateNodeListCaches(const QualifiedName* attrName = nullptr) const;
    void invalidateNodeListCaches(const QualifiedName* attrName);

    void attachNodeIterator(NodeIterator*);
    void detachNodeIterator(NodeIterator*);
    void moveNodeIteratorsToNewDocument(Node&, Document&);

    void attachRange(Range*);
    void detachRange(Range*);

    void updateRangesAfterNodeMovedToAnotherDocument(const Node&);
    // nodeChildrenWillBeRemoved is used when removing all node children at once.
    void nodeChildrenWillBeRemoved(ContainerNode&);
    // nodeWillBeRemoved is only safe when removing one node at a time.
    void nodeWillBeRemoved(Node&);
    // Called just before a destructive update to some CharacterData.
    void dataWillChange(const CharacterData&);
    bool canAcceptChild(const Node& newChild, const Node* oldChild, ExceptionState&) const;

    void didInsertText(Node*, unsigned offset, unsigned length);
    void didRemoveText(Node*, unsigned offset, unsigned length);
    void didMergeTextNodes(Text& oldNode, unsigned offset);
    void didSplitTextNode(Text& oldNode);

    void clearDOMWindow() { m_domWindow = nullptr; }
    LocalDOMWindow* domWindow() const { return m_domWindow; }

    // Helper functions for forwarding LocalDOMWindow event related tasks to the LocalDOMWindow if it exists.
    void setWindowAttributeEventListener(const AtomicString& eventType, EventListener*);
    EventListener* getWindowAttributeEventListener(const AtomicString& eventType);

    static void registerEventFactory(PassOwnPtr<EventFactoryBase>);
    static Event* createEvent(ExecutionContext*, const String& eventType, ExceptionState&);

    // keep track of what types of event listeners are registered, so we don't
    // dispatch events unnecessarily
    enum ListenerType {
        DOMSUBTREEMODIFIED_LISTENER          = 1,
        DOMNODEINSERTED_LISTENER             = 1 << 1,
        DOMNODEREMOVED_LISTENER              = 1 << 2,
        DOMNODEREMOVEDFROMDOCUMENT_LISTENER  = 1 << 3,
        DOMNODEINSERTEDINTODOCUMENT_LISTENER = 1 << 4,
        DOMCHARACTERDATAMODIFIED_LISTENER    = 1 << 5,
        ANIMATIONEND_LISTENER                = 1 << 6,
        ANIMATIONSTART_LISTENER              = 1 << 7,
        ANIMATIONITERATION_LISTENER          = 1 << 8,
        TRANSITIONEND_LISTENER               = 1 << 9,
        SCROLL_LISTENER                      = 1 << 10
        // 5 bits remaining
    };

    bool hasListenerType(ListenerType listenerType) const { return (m_listenerTypes & listenerType); }
    void addListenerTypeIfNeeded(const AtomicString& eventType);

    bool hasMutationObserversOfType(MutationObserver::MutationType type) const
    {
        return m_mutationObserverTypes & type;
    }
    bool hasMutationObservers() const { return m_mutationObserverTypes; }
    void addMutationObserverTypes(MutationObserverOptions types) { m_mutationObserverTypes |= types; }

    IntersectionObserverController* intersectionObserverController();
    IntersectionObserverController& ensureIntersectionObserverController();
    NodeIntersectionObserverData& ensureIntersectionObserverData();

    void updateViewportDescription();
    void processReferrerPolicy(const String& policy);

    // Returns the owning element in the parent document. Returns nullptr if
    // this is the top level document or the owner is remote.
    HTMLFrameOwnerElement* localOwner() const;

    // Returns true if this document belongs to a frame that the parent document
    // made invisible (for instance by setting as style display:none).
    bool isInInvisibleSubframe() const;

    String title() const { return m_title; }
    void setTitle(const String&);

    Element* titleElement() const { return m_titleElement.get(); }
    void setTitleElement(Element*);
    void removeTitle(Element* titleElement);

    const AtomicString& dir();
    void setDir(const AtomicString&);

    String cookie(ExceptionState&) const;
    void setCookie(const String&, ExceptionState&);

    const AtomicString& referrer() const;

    String domain() const;
    void setDomain(const String& newDomain, ExceptionState&);

    String lastModified() const;

    // The cookieURL is used to query the cookie database for this document's
    // cookies. For example, if the cookie URL is http://example.com, we'll
    // use the non-Secure cookies for example.com when computing
    // document.cookie.
    //
    // Q: How is the cookieURL different from the document's URL?
    // A: The two URLs are the same almost all the time.  However, if one
    //    document inherits the security context of another document, it
    //    inherits its cookieURL but not its URL.
    //
    const KURL& cookieURL() const { return m_cookieURL; }
    void setCookieURL(const KURL& url) { m_cookieURL = url; }

    const KURL firstPartyForCookies() const;

    // The following implements the rule from HTML 4 for what valid names are.
    // To get this right for all the XML cases, we probably have to improve this or move it
    // and make it sensitive to the type of document.
    static bool isValidName(const String&);

    // The following breaks a qualified name into a prefix and a local name.
    // It also does a validity check, and returns false if the qualified name
    // is invalid.  It also sets ExceptionCode when name is invalid.
    static bool parseQualifiedName(const AtomicString& qualifiedName, AtomicString& prefix, AtomicString& localName, ExceptionState&);

    // Checks to make sure prefix and namespace do not conflict (per DOM Core 3)
    static bool hasValidNamespaceForElements(const QualifiedName&);
    static bool hasValidNamespaceForAttributes(const QualifiedName&);

    // "body element" as defined by HTML5 (https://html.spec.whatwg.org/multipage/dom.html#the-body-element-2).
    // That is, the first body or frameset child of the document element.
    HTMLElement* body() const;

    // "HTML body element" as defined by CSSOM View spec (http://dev.w3.org/csswg/cssom-view/#the-html-body-element).
    // That is, the first body child of the document element.
    HTMLBodyElement* firstBodyElement() const;

    void setBody(HTMLElement*, ExceptionState&);
    void willInsertBody();

    HTMLHeadElement* head() const;

    // Decide which element is to define the viewport's overflow policy. If |rootStyle| is set, use
    // that as the style for the root element, rather than obtaining it on our own. The reason for
    // this is that style may not have been associated with the elements yet - in which case it may
    // have been calculated on the fly (without associating it with the actual element) somewhere.
    Element* viewportDefiningElement(const ComputedStyle* rootStyle = nullptr) const;

    DocumentMarkerController& markers() const { return *m_markers; }

    bool execCommand(const String& command, bool showUI, const String& value, ExceptionState&);
    bool isRunningExecCommand() const { return m_isRunningExecCommand; }
    bool queryCommandEnabled(const String& command, ExceptionState&);
    bool queryCommandIndeterm(const String& command, ExceptionState&);
    bool queryCommandState(const String& command, ExceptionState&);
    bool queryCommandSupported(const String& command, ExceptionState&);
    String queryCommandValue(const String& command, ExceptionState&);

    KURL openSearchDescriptionURL();

    // designMode support
    bool inDesignMode() const { return m_designMode; }
    String designMode() const;
    void setDesignMode(const String&);

    Document* parentDocument() const;
    Document& topDocument() const;
    Document* contextDocument();

    ScriptRunner* scriptRunner() { return m_scriptRunner.get(); }

    Element* currentScript() const { return !m_currentScriptStack.isEmpty() ? m_currentScriptStack.last().get() : nullptr; }
    void currentScriptForBinding(HTMLScriptElementOrSVGScriptElement&) const;
    void pushCurrentScript(Element*);
    void popCurrentScript();

    void setTransformSource(PassOwnPtr<TransformSource>);
    TransformSource* transformSource() const { return m_transformSource.get(); }

    void incDOMTreeVersion() { DCHECK(m_lifecycle.stateAllowsTreeMutations()); m_domTreeVersion = ++s_globalTreeVersion; }
    uint64_t domTreeVersion() const { return m_domTreeVersion; }

    uint64_t styleVersion() const { return m_styleVersion; }

    enum PendingSheetLayout { NoLayoutWithPendingSheets, DidLayoutWithPendingSheets, IgnoreLayoutWithPendingSheets };

    bool didLayoutWithPendingStylesheets() const { return m_pendingSheetLayout == DidLayoutWithPendingSheets; }
    bool ignoreLayoutWithPendingStylesheets() const { return m_pendingSheetLayout == IgnoreLayoutWithPendingSheets; }

    bool hasNodesWithPlaceholderStyle() const { return m_hasNodesWithPlaceholderStyle; }
    void setHasNodesWithPlaceholderStyle() { m_hasNodesWithPlaceholderStyle = true; }

    Vector<IconURL> iconURLs(int iconTypesMask);

    Color themeColor() const;

    // Returns the HTMLLinkElement currently in use for the Web Manifest.
    // Returns null if there is no such element.
    HTMLLinkElement* linkManifest() const;

    void setUseSecureKeyboardEntryWhenActive(bool);
    bool useSecureKeyboardEntryWhenActive() const;

    void updateFocusAppearanceSoon(SelectionBehaviorOnFocus);
    void cancelFocusAppearanceUpdate();

    bool isDNSPrefetchEnabled() const { return m_isDNSPrefetchEnabled; }
    void parseDNSPrefetchControlHeader(const String&);

    // FIXME(crbug.com/305497): This should be removed once LocalDOMWindow is an ExecutionContext.
    void postTask(const WebTraceLocation&, std::unique_ptr<ExecutionContextTask>) override; // Executes the task on context's thread asynchronously.
    void postInspectorTask(const WebTraceLocation&, std::unique_ptr<ExecutionContextTask>);

    void tasksWereSuspended() final;
    void tasksWereResumed() final;
    void suspendScheduledTasks() final;
    void resumeScheduledTasks() final;
    bool tasksNeedSuspension() final;

    void finishedParsing();

    void setEncodingData(const DocumentEncodingData& newData);
    const WTF::TextEncoding& encoding() const { return m_encodingData.encoding(); }

    bool encodingWasDetectedHeuristically() const { return m_encodingData.wasDetectedHeuristically(); }
    bool sawDecodingError() const { return m_encodingData.sawDecodingError(); }

    void setAnnotatedRegionsDirty(bool f) { m_annotatedRegionsDirty = f; }
    bool annotatedRegionsDirty() const { return m_annotatedRegionsDirty; }
    bool hasAnnotatedRegions () const { return m_hasAnnotatedRegions; }
    void setHasAnnotatedRegions(bool f) { m_hasAnnotatedRegions = f; }
    const Vector<AnnotatedRegionValue>& annotatedRegions() const;
    void setAnnotatedRegions(const Vector<AnnotatedRegionValue>&);

    void removeAllEventListeners() final;

    const SVGDocumentExtensions* svgExtensions();
    SVGDocumentExtensions& accessSVGExtensions();

    void initContentSecurityPolicy(ContentSecurityPolicy* = nullptr);

    bool isSecureTransitionTo(const KURL&) const;

    bool allowInlineEventHandler(Node*, EventListener*, const String& contextURL, const WTF::OrdinalNumber& contextLine);
    bool allowExecutingScripts(Node*);

    void enforceSandboxFlags(SandboxFlags mask) override;

    void statePopped(PassRefPtr<SerializedScriptValue>);

    enum LoadEventProgress {
        LoadEventNotRun,
        LoadEventInProgress,
        LoadEventCompleted,
        BeforeUnloadEventInProgress,
        BeforeUnloadEventCompleted,
        PageHideInProgress,
        UnloadVisibilityChangeInProgress,
        UnloadEventInProgress,
        UnloadEventHandled
    };
    bool loadEventStillNeeded() const { return m_loadEventProgress == LoadEventNotRun; }
    bool processingLoadEvent() const { return m_loadEventProgress == LoadEventInProgress; }
    bool loadEventFinished() const { return m_loadEventProgress >= LoadEventCompleted; }
    bool unloadStarted() const { return m_loadEventProgress >= PageHideInProgress; }
    bool processingBeforeUnload() const { return m_loadEventProgress == BeforeUnloadEventInProgress; }
    void suppressLoadEvent();

    void setContainsPlugins() { m_containsPlugins = true; }
    bool containsPlugins() const { return m_containsPlugins; }

    bool isContextThread() const final;
    bool isJSExecutionForbidden() const final { return false; }

    bool containsValidityStyleRules() const { return m_containsValidityStyleRules; }
    void setContainsValidityStyleRules() { m_containsValidityStyleRules = true; }

    void enqueueResizeEvent();
    void enqueueScrollEventForNode(Node*);
    void enqueueAnimationFrameEvent(Event*);
    // Only one event for a target/event type combination will be dispatched per frame.
    void enqueueUniqueAnimationFrameEvent(Event*);
    void enqueueMediaQueryChangeListeners(HeapVector<Member<MediaQueryListListener>>&);
    void enqueueVisualViewportChangedEvent();

    void dispatchEventsForPrinting();

    bool hasFullscreenSupplement() const { return m_hasFullscreenSupplement; }
    void setHasFullscreenSupplement() { m_hasFullscreenSupplement = true; }

    void exitPointerLock();
    Element* pointerLockElement() const;

    // Used to allow element that loads data without going through a FrameLoader to delay the 'load' event.
    void incrementLoadEventDelayCount() { ++m_loadEventDelayCount; }
    void decrementLoadEventDelayCount();
    void checkLoadEventSoon();
    bool isDelayingLoadEvent();
    void loadPluginsSoon();

    Touch* createTouch(DOMWindow*, EventTarget*, int identifier, double pageX, double pageY, double screenX, double screenY, double radiusX, double radiusY, float rotationAngle, float force) const;
    TouchList* createTouchList(HeapVector<Member<Touch>>&) const;

    const DocumentTiming& timing() const { return m_documentTiming; }

    int requestAnimationFrame(FrameRequestCallback*);
    void cancelAnimationFrame(int id);
    void serviceScriptedAnimations(double monotonicAnimationStartTime);

    int requestIdleCallback(IdleRequestCallback*, const IdleRequestOptions&);
    void cancelIdleCallback(int id);

    EventTarget* errorEventTarget() final;
    void logExceptionToConsole(const String& errorMessage, PassOwnPtr<SourceLocation>) final;

    void initDNSPrefetch();

    bool isInDocumentWrite() const { return m_writeRecursionDepth > 0; }

    TextAutosizer* textAutosizer();

    Element* createElement(const AtomicString& localName, const AtomicString& typeExtension, ExceptionState&);
    Element* createElementNS(const AtomicString& namespaceURI, const AtomicString& qualifiedName, const AtomicString& typeExtension, ExceptionState&);
    ScriptValue registerElement(ScriptState*, const AtomicString& name, const ElementRegistrationOptions&, ExceptionState&, V0CustomElement::NameSet validNames = V0CustomElement::StandardNames);
    V0CustomElementRegistrationContext* registrationContext() { return m_registrationContext.get(); }
    V0CustomElementMicrotaskRunQueue* customElementMicrotaskRunQueue();

    void setImportsController(HTMLImportsController*);
    HTMLImportsController* importsController() const { return m_importsController; }
    HTMLImportLoader* importLoader() const;

    bool haveImportsLoaded() const;
    void didLoadAllImports();

    void adjustFloatQuadsForScrollAndAbsoluteZoom(Vector<FloatQuad>&, LayoutObject&);
    void adjustFloatRectForScrollAndAbsoluteZoom(FloatRect&, LayoutObject&);

    void setContextFeatures(ContextFeatures&);
    ContextFeatures& contextFeatures() const { return *m_contextFeatures; }

    ElementDataCache* elementDataCache() { return m_elementDataCache.get(); }

    void didLoadAllScriptBlockingResources();
    void didRemoveAllPendingStylesheet();

    bool inStyleRecalc() const { return m_lifecycle.state() == DocumentLifecycle::InStyleRecalc; }

    // Return a Locale for the default locale if the argument is null or empty.
    Locale& getCachedLocale(const AtomicString& locale = nullAtom);

    AnimationClock& animationClock();
    AnimationTimeline& timeline() const { return *m_timeline; }
    CompositorPendingAnimations& compositorPendingAnimations() { return *m_compositorPendingAnimations; }

    void addToTopLayer(Element*, const Element* before = nullptr);
    void removeFromTopLayer(Element*);
    const HeapVector<Member<Element>>& topLayerElements() const { return m_topLayerElements; }
    HTMLDialogElement* activeModalDialog() const;

    // A non-null m_templateDocumentHost implies that |this| was created by ensureTemplateDocument().
    bool isTemplateDocument() const { return !!m_templateDocumentHost; }
    Document& ensureTemplateDocument();
    Document* templateDocumentHost() { return m_templateDocumentHost; }

    // TODO(thestig): Rename these and related functions, since we can call them
    // for labels and input fields outside of forms as well.
    void didAssociateFormControl(Element*);
    void removeFormAssociation(Element*);

    void addConsoleMessage(ConsoleMessage*) final;

    LocalDOMWindow* executingWindow() final;
    LocalFrame* executingFrame();

    DocumentLifecycle& lifecycle() { return m_lifecycle; }
    bool isActive() const { return m_lifecycle.isActive(); }
    bool isDetached() const { return m_lifecycle.state() >= DocumentLifecycle::Stopping; }
    bool isStopped() const { return m_lifecycle.state() == DocumentLifecycle::Stopped; }

    enum HttpRefreshType {
        HttpRefreshFromHeader,
        HttpRefreshFromMetaTag
    };
    void maybeHandleHttpRefresh(const String&, HttpRefreshType);

    void updateSecurityOrigin(PassRefPtr<SecurityOrigin>);

    void setHasViewportUnits() { m_hasViewportUnits = true; }
    bool hasViewportUnits() const { return m_hasViewportUnits; }
    void notifyResizeForViewportUnits();

    void updateStyleInvalidationIfNeeded();

    DECLARE_VIRTUAL_TRACE();

    DECLARE_VIRTUAL_TRACE_WRAPPERS();

    bool hasSVGFilterElementsRequiringLayerUpdate() const { return m_layerUpdateSVGFilterElements.size(); }

    AtomicString convertLocalName(const AtomicString&);

    void platformColorsChanged();

    DOMTimerCoordinator* timers() final;

    v8::Local<v8::Object> wrap(v8::Isolate*, v8::Local<v8::Object> creationContext) override;
    v8::Local<v8::Object> associateWithWrapper(v8::Isolate*, const WrapperTypeInfo*, v8::Local<v8::Object> wrapper) override WARN_UNUSED_RETURN;

    HostsUsingFeatures::Value& HostsUsingFeaturesValue() { return m_hostsUsingFeaturesValue; }

    NthIndexCache* nthIndexCache() const { return m_nthIndexCache; }

    bool isSecureContext(String& errorMessage, const SecureContextCheck = StandardSecureContextCheck) const override;
    bool isSecureContext(const SecureContextCheck = StandardSecureContextCheck) const override;

    ClientHintsPreferences& clientHintsPreferences() { return m_clientHintsPreferences; }

    CanvasFontCache* canvasFontCache();

    // Used by unit tests so that all parsing will be main thread for
    // controlling parsing and chunking precisely.
    static void setThreadedParsingEnabledForTesting(bool);
    static bool threadedParsingEnabledForTesting();

    void incrementNodeCount() { m_nodeCount++; }
    void decrementNodeCount()
    {
        DCHECK_GT(m_nodeCount, 0);
        m_nodeCount--;
    }
    int nodeCount() const { return m_nodeCount; }

    SnapCoordinator* snapCoordinator();

    WebTaskRunner* loadingTaskRunner() const;
    WebTaskRunner* timerTaskRunner() const;

    void enforceStrictMixedContentChecking();

    bool mayContainV0Shadow() const { return m_mayContainV0Shadow; }

    ShadowCascadeOrder shadowCascadeOrder() const { return m_shadowCascadeOrder; }
    void setShadowCascadeOrder(ShadowCascadeOrder);

    bool containsV1ShadowTree() const { return m_shadowCascadeOrder == ShadowCascadeOrder::ShadowCascadeV1; }

    Element* rootScroller() const;
    void setRootScroller(Element*, ExceptionState&);
    bool isEffectiveRootScroller(const Element&) const;

    bool isInMainFrame() const;

protected:
    Document(const DocumentInit&, DocumentClassFlags = DefaultDocumentClass);

    void didUpdateSecurityOrigin() final;

    void clearXMLVersion() { m_xmlVersion = String(); }

    virtual Document* cloneDocumentWithoutChildren();

    bool importContainerNodeChildren(ContainerNode* oldContainerNode, ContainerNode* newContainerNode, ExceptionState&);
    void lockCompatibilityMode() { m_compatibilityModeLocked = true; }
    ParserSynchronizationPolicy getParserSynchronizationPolicy() const { return m_parserSyncPolicy; }

private:
    friend class IgnoreDestructiveWriteCountIncrementer;
    friend class NthIndexCache;

    bool isDocumentFragment() const = delete; // This will catch anyone doing an unnecessary check.
    bool isDocumentNode() const = delete; // This will catch anyone doing an unnecessary check.
    bool isElementNode() const = delete; // This will catch anyone doing an unnecessary check.

    ScriptedAnimationController& ensureScriptedAnimationController();
    ScriptedIdleTaskController& ensureScriptedIdleTaskController();
    void initSecurityContext(const DocumentInit&);
    SecurityContext& securityContext() final { return *this; }
    EventQueue* getEventQueue() const final;

    bool hasPendingVisualUpdate() const { return m_lifecycle.state() == DocumentLifecycle::VisualUpdatePending; }

    bool shouldScheduleLayoutTreeUpdate() const;
    void scheduleLayoutTreeUpdate();

    bool needsFullLayoutTreeUpdate() const;

    void inheritHtmlAndBodyElementStyles(StyleRecalcChange);

    bool dirtyElementsForLayerUpdate();

    void updateUseShadowTreesIfNeeded();
    void evaluateMediaQueryListIfNeeded();

    void updateStyle();
    void notifyLayoutTreeOfSubtreeChanges();

    void detachParser();

    void beginLifecycleUpdatesIfRenderingReady();

    bool isDocument() const final { return true; }

    void childrenChanged(const ChildrenChange&) override;

    String nodeName() const final;
    NodeType getNodeType() const final;
    bool childTypeAllowed(NodeType) const final;
    Node* cloneNode(bool deep) final;
    void cloneDataFromDocument(const Document&);
    bool isSecureContextImpl(String* errorMessage, const SecureContextCheck priviligeContextCheck) const;

    ShadowCascadeOrder m_shadowCascadeOrder = ShadowCascadeNone;

    const KURL& virtualURL() const final; // Same as url(), but needed for ExecutionContext to implement it without a performance loss for direct calls.
    KURL virtualCompleteURL(const String&) const final; // Same as completeURL() for the same reason as above.

    void reportBlockedScriptExecutionToInspector(const String& directiveText) final;

    void updateTitle(const String&);
    void updateFocusAppearanceTimerFired(Timer<Document>*);
    void updateBaseURL();

    void executeScriptsWaitingForResources();

    void loadEventDelayTimerFired(Timer<Document>*);
    void pluginLoadingTimerFired(Timer<Document>*);

    void addListenerType(ListenerType listenerType) { m_listenerTypes |= listenerType; }
    void addMutationEventListenerTypeIfEnabled(ListenerType);

    void didAssociateFormControlsTimerFired(Timer<Document>*);

    void clearFocusedElementSoon();
    void clearFocusedElementTimerFired(Timer<Document>*);

    bool haveScriptBlockingStylesheetsLoaded() const;
    bool haveRenderBlockingStylesheetsLoaded() const;
    void styleResolverMayHaveChanged();

    void setHoverNode(Node*);

    using EventFactorySet = HashSet<OwnPtr<EventFactoryBase>>;
    static EventFactorySet& eventFactories();

    void setNthIndexCache(NthIndexCache* nthIndexCache) { DCHECK(!m_nthIndexCache || !nthIndexCache); m_nthIndexCache = nthIndexCache; }

    const OriginAccessEntry& accessEntryFromURL();

    DocumentLifecycle m_lifecycle;

    bool m_hasNodesWithPlaceholderStyle;
    bool m_evaluateMediaQueriesOnStyleRecalc;

    // If we do ignore the pending stylesheet count, then we need to add a boolean
    // to track that this happened so that we can do a full repaint when the stylesheets
    // do eventually load.
    PendingSheetLayout m_pendingSheetLayout;

    Member<LocalFrame> m_frame;
    Member<LocalDOMWindow> m_domWindow;
    Member<HTMLImportsController> m_importsController;

    Member<ResourceFetcher> m_fetcher;
    Member<DocumentParser> m_parser;
    Member<ContextFeatures> m_contextFeatures;

    bool m_wellFormed;

    // Document URLs.
    KURL m_url; // Document.URL: The URL from which this document was retrieved.
    KURL m_baseURL; // Node.baseURI: The URL to use when resolving relative URLs.
    KURL m_baseURLOverride; // An alternative base URL that takes precedence over m_baseURL (but not m_baseElementURL).
    KURL m_baseElementURL; // The URL set by the <base> element.
    KURL m_cookieURL; // The URL to use for cookie access.
    OwnPtr<OriginAccessEntry> m_accessEntryFromURL;

    AtomicString m_baseTarget;

    // Mime-type of the document in case it was cloned or created by XHR.
    AtomicString m_mimeType;

    Member<DocumentType> m_docType;
    Member<DOMImplementation> m_implementation;

    Member<CSSStyleSheet> m_elemSheet;

    bool m_printing;
    bool m_wasPrinting;
    bool m_paginatedForScreen;

    CompatibilityMode m_compatibilityMode;
    bool m_compatibilityModeLocked; // This is cheaper than making setCompatibilityMode virtual.

    OwnPtr<CancellableTaskFactory> m_executeScriptsWaitingForResourcesTask;

    bool m_hasAutofocused;
    Timer<Document> m_clearFocusedElementTimer;
    Member<Element> m_autofocusElement;
    Member<Element> m_focusedElement;
    Member<Range> m_sequentialFocusNavigationStartingPoint;
    Member<Node> m_hoverNode;
    Member<Element> m_activeHoverElement;
    Member<Element> m_documentElement;
    UserActionElementSet m_userActionElements;
    Member<RootScrollerController> m_rootScrollerController;

    uint64_t m_domTreeVersion;
    static uint64_t s_globalTreeVersion;

    uint64_t m_styleVersion;

    HeapHashSet<WeakMember<NodeIterator>> m_nodeIterators;
    using AttachedRangeSet = HeapHashSet<WeakMember<Range>>;
    AttachedRangeSet m_ranges;

    unsigned short m_listenerTypes;

    MutationObserverOptions m_mutationObserverTypes;

    Member<StyleEngine> m_styleEngine;
    Member<StyleSheetList> m_styleSheetList;

    Member<FormController> m_formController;

    TextLinkColors m_textLinkColors;
    const Member<VisitedLinkState> m_visitedLinkState;

    bool m_visuallyOrdered;
    ReadyState m_readyState;
    ParsingState m_parsingState;

    bool m_gotoAnchorNeededAfterStylesheetsLoad;
    bool m_isDNSPrefetchEnabled;
    bool m_haveExplicitlyDisabledDNSPrefetch;
    bool m_containsValidityStyleRules;
    bool m_containsPlugins;
    SelectionBehaviorOnFocus m_updateFocusAppearanceSelectionBahavior;

    // http://www.whatwg.org/specs/web-apps/current-work/#ignore-destructive-writes-counter
    unsigned m_ignoreDestructiveWriteCount;

    String m_title;
    String m_rawTitle;
    Member<Element> m_titleElement;

    Member<AXObjectCache> m_axObjectCache;
    Member<DocumentMarkerController> m_markers;

    Timer<Document> m_updateFocusAppearanceTimer;

    Member<Element> m_cssTarget;

    LoadEventProgress m_loadEventProgress;

    double m_startTime;

    Member<ScriptRunner> m_scriptRunner;

    HeapVector<Member<Element>> m_currentScriptStack;

    OwnPtr<TransformSource> m_transformSource;

    String m_xmlEncoding;
    String m_xmlVersion;
    unsigned m_xmlStandalone : 2;
    unsigned m_hasXMLDeclaration : 1;

    AtomicString m_contentLanguage;

    DocumentEncodingData m_encodingData;

    bool m_designMode;
    bool m_isRunningExecCommand;

    HeapHashSet<WeakMember<const LiveNodeListBase>> m_listsInvalidatedAtDocument;
    // Oilpan keeps track of all registered NodeLists.
    // TODO(Oilpan): improve - only need to know if a NodeList
    // is currently alive or not for the different types.
    HeapHashSet<WeakMember<const LiveNodeListBase>> m_nodeLists[numNodeListInvalidationTypes];

    Member<SVGDocumentExtensions> m_svgExtensions;

    Vector<AnnotatedRegionValue> m_annotatedRegions;
    bool m_hasAnnotatedRegions;
    bool m_annotatedRegionsDirty;

    OwnPtr<SelectorQueryCache> m_selectorQueryCache;

    // It is safe to keep a raw, untraced pointer to this stack-allocated
    // cache object: it is set upon the cache object being allocated on
    // the stack and cleared upon leaving its allocated scope. Hence it
    // is acceptable not to trace it -- should a conservative GC occur,
    // the cache object's references will be traced by a stack walk.
    GC_PLUGIN_IGNORE("461878")
    NthIndexCache* m_nthIndexCache = nullptr;

    bool m_useSecureKeyboardEntryWhenActive;

    DocumentClassFlags m_documentClasses;

    bool m_isViewSource;
    bool m_sawElementsInKnownNamespaces;
    bool m_isSrcdocDocument;
    bool m_isMobileDocument;

    LayoutView* m_layoutView;

    WeakMember<Document> m_contextDocument;

    bool m_hasFullscreenSupplement; // For early return in Fullscreen::fromIfExists()

    HeapVector<Member<Element>> m_topLayerElements;

    int m_loadEventDelayCount;
    Timer<Document> m_loadEventDelayTimer;
    Timer<Document> m_pluginLoadingTimer;

    ViewportDescription m_viewportDescription;
    ViewportDescription m_legacyViewportDescription;
    Length m_viewportDefaultMinWidth;

    ReferrerPolicy m_referrerPolicy;

    DocumentTiming m_documentTiming;
    Member<MediaQueryMatcher> m_mediaQueryMatcher;
    bool m_writeRecursionIsTooDeep;
    unsigned m_writeRecursionDepth;

    Member<ScriptedAnimationController> m_scriptedAnimationController;
    Member<ScriptedIdleTaskController> m_scriptedIdleTaskController;
    OwnPtr<MainThreadTaskRunner> m_taskRunner;
    Member<TextAutosizer> m_textAutosizer;

    Member<V0CustomElementRegistrationContext> m_registrationContext;
    Member<V0CustomElementMicrotaskRunQueue> m_customElementMicrotaskRunQueue;

    void elementDataCacheClearTimerFired(Timer<Document>*);
    Timer<Document> m_elementDataCacheClearTimer;

    Member<ElementDataCache> m_elementDataCache;

    using LocaleIdentifierToLocaleMap = HashMap<AtomicString, OwnPtr<Locale>>;
    LocaleIdentifierToLocaleMap m_localeCache;

    Member<AnimationTimeline> m_timeline;
    Member<CompositorPendingAnimations> m_compositorPendingAnimations;

    Member<Document> m_templateDocument;
    Member<Document> m_templateDocumentHost;

    Timer<Document> m_didAssociateFormControlsTimer;
    HeapHashSet<Member<Element>> m_associatedFormControls;

    HeapHashSet<Member<SVGUseElement>> m_useElementsNeedingUpdate;
    HeapHashSet<Member<Element>> m_layerUpdateSVGFilterElements;

    DOMTimerCoordinator m_timers;

    bool m_hasViewportUnits;

    ParserSynchronizationPolicy m_parserSyncPolicy;

    HostsUsingFeatures::Value m_hostsUsingFeaturesValue;

    ClientHintsPreferences m_clientHintsPreferences;

    Member<CanvasFontCache> m_canvasFontCache;

    Member<IntersectionObserverController> m_intersectionObserverController;
    Member<NodeIntersectionObserverData> m_intersectionObserverData;

    int m_nodeCount;

    bool m_mayContainV0Shadow = false;

    Member<SnapCoordinator> m_snapCoordinator;
};

extern template class CORE_EXTERN_TEMPLATE_EXPORT Supplement<Document>;

inline bool Document::shouldOverrideLegacyDescription(ViewportDescription::Type origin) const
{
    // The different (legacy) meta tags have different priorities based on the type
    // regardless of which order they appear in the DOM. The priority is given by the
    // ViewportDescription::Type enum.
    return origin >= m_legacyViewportDescription.type;
}

inline void Document::scheduleLayoutTreeUpdateIfNeeded()
{
    // Inline early out to avoid the function calls below.
    if (hasPendingVisualUpdate())
        return;
    if (shouldScheduleLayoutTreeUpdate() && needsLayoutTreeUpdate())
        scheduleLayoutTreeUpdate();
}

DEFINE_TYPE_CASTS(Document, ExecutionContext, context, context->isDocument(), context.isDocument());
DEFINE_NODE_TYPE_CASTS(Document, isDocumentNode());

#define DEFINE_DOCUMENT_TYPE_CASTS(thisType) \
    DEFINE_TYPE_CASTS(thisType, Document, document, document->is##thisType(), document.is##thisType())

// This is needed to avoid ambiguous overloads with the Node and TreeScope versions.
DEFINE_COMPARISON_OPERATORS_WITH_REFERENCES(Document)

// Put these methods here, because they require the Document definition, but we really want to inline them.

inline bool Node::isDocumentNode() const
{
    return this == document();
}

Node* eventTargetNodeForDocument(Document*);

DEFINE_TYPE_CASTS(TreeScope, Document, document, true, true);

} // namespace blink

#ifndef NDEBUG
// Outside the WebCore namespace for ease of invocation from gdb.
CORE_EXPORT void showLiveDocumentInstances();
#endif

#endif // Document_h