/*
* Copyright (C) 2012, Google 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.
* 3.  Neither the name of Apple Inc. ("Apple") nor the names of
*     its contributors may be used to endorse or promote products derived
*     from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "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 OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* 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 "AccessibilityNodeObject.h"

#include "AXLogger.h"
#include "AXObjectCache.h"
#include "AccessibilityImageMapLink.h"
#include "AccessibilityLabel.h"
#include "AccessibilityList.h"
#include "AccessibilityListBox.h"
#include "AccessibilitySpinButton.h"
#include "AccessibilityTable.h"
#include "ComposedTreeIterator.h"
#include "DateComponents.h"
#include "Editing.h"
#include "ElementAncestorIteratorInlines.h"
#include "ElementChildIteratorInlines.h"
#include "Event.h"
#include "EventHandler.h"
#include "EventNames.h"
#include "FloatRect.h"
#include "FrameLoader.h"
#include "FrameSelection.h"
#include "HTMLAudioElement.h"
#include "HTMLCanvasElement.h"
#include "HTMLDetailsElement.h"
#include "HTMLFieldSetElement.h"
#include "HTMLFormElement.h"
#include "HTMLImageElement.h"
#include "HTMLInputElement.h"
#include "HTMLLabelElement.h"
#include "HTMLLegendElement.h"
#include "HTMLNames.h"
#include "HTMLOptionElement.h"
#include "HTMLParagraphElement.h"
#include "HTMLParserIdioms.h"
#include "HTMLSelectElement.h"
#include "HTMLSlotElement.h"
#include "HTMLSummaryElement.h"
#include "HTMLTextAreaElement.h"
#include "HTMLTextFormControlElement.h"
#include "HTMLVideoElement.h"
#include "HitTestSource.h"
#include "KeyboardEvent.h"
#include "LocalFrame.h"
#include "LocalFrameView.h"
#include "LocalizedStrings.h"
#include "MathMLElement.h"
#include "MathMLNames.h"
#include "NodeList.h"
#include "NodeTraversal.h"
#include "ProgressTracker.h"
#include "RenderImage.h"
#include "RenderTableCell.h"
#include "RenderView.h"
#include "SVGElement.h"
#include "ShadowRoot.h"
#include "Text.h"
#include "TextControlInnerElements.h"
#include "TextIterator.h"
#include "UserGestureIndicator.h"
#include "VisibleUnits.h"
#include <wtf/Scope.h>
#include <wtf/SetForScope.h>
#include <wtf/StdLibExtras.h>
#include <wtf/text/StringBuilder.h>
#include <wtf/unicode/CharacterNames.h>

namespace WebCore {

using namespace HTMLNames;

static String accessibleNameForNode(Node&, Node* labelledbyNode = nullptr);
static void appendNameToStringBuilder(StringBuilder&, String&&, bool prependSpace = true);

AccessibilityNodeObject::AccessibilityNodeObject(AXID axID, Node* node)
    : AccessibilityObject(axID)
    , m_node(node)
{
}

AccessibilityNodeObject::~AccessibilityNodeObject()
{
    ASSERT(isDetached());
}

void AccessibilityNodeObject::init()
{
#ifndef NDEBUG
    ASSERT(!m_initialized);
    m_initialized = true;
#endif
    AccessibilityObject::init();
}

Ref<AccessibilityNodeObject> AccessibilityNodeObject::create(AXID axID, Node& node)
{
    return adoptRef(*new AccessibilityNodeObject(axID, &node));
}

void AccessibilityNodeObject::detachRemoteParts(AccessibilityDetachmentType detachmentType)
{
    // AccessibilityObject calls clearChildren.
    AccessibilityObject::detachRemoteParts(detachmentType);
    m_node = nullptr;
}

AccessibilityObject* AccessibilityNodeObject::firstChild() const
{
    auto* currentChild = node() ? node()->firstChild() : nullptr;
    if (!currentChild)
        return nullptr;

    auto* cache = axObjectCache();
    if (!cache)
        return nullptr;

    auto* axCurrentChild = cache->getOrCreate(*currentChild);
    while (!axCurrentChild && currentChild) {
        currentChild = currentChild->nextSibling();
        axCurrentChild = cache->getOrCreate(currentChild);
    }
    return axCurrentChild;
}

AccessibilityObject* AccessibilityNodeObject::lastChild() const
{
    if (!node())
        return nullptr;

    Node* lastChild = node()->lastChild();
    if (!lastChild)
        return nullptr;

    auto objectCache = axObjectCache();
    return objectCache ? objectCache->getOrCreate(*lastChild) : nullptr;
}

AccessibilityObject* AccessibilityNodeObject::previousSibling() const
{
    if (!node())
        return nullptr;

    Node* previousSibling = node()->previousSibling();
    if (!previousSibling)
        return nullptr;

    auto objectCache = axObjectCache();
    return objectCache ? objectCache->getOrCreate(*previousSibling) : nullptr;
}

AccessibilityObject* AccessibilityNodeObject::nextSibling() const
{
    if (!node())
        return nullptr;

    Node* nextSibling = node()->nextSibling();
    if (!nextSibling)
        return nullptr;

    auto objectCache = axObjectCache();
    return objectCache ? objectCache->getOrCreate(*nextSibling) : nullptr;
}

AccessibilityObject* AccessibilityNodeObject::ownerParentObject() const
{
    auto owners = this->owners();
    ASSERT(owners.size() <= 1);
    return owners.size() ? dynamicDowncast<AccessibilityObject>(owners.first().get()) : nullptr;
}

AccessibilityObject* AccessibilityNodeObject::parentObject() const
{
    RefPtr node = this->node();
    if (!node)
        return nullptr;

    if (auto* ownerParent = ownerParentObject())
        return ownerParent;

    CheckedPtr cache = axObjectCache();
#if USE(ATSPI)
    // FIXME: Consider removing this ATSPI-only branch with https://bugs.webkit.org/show_bug.cgi?id=282117.
    return cache ? cache->getOrCreate(node->parentNode()) : nullptr;
#else
    return cache ? cache->getOrCreate(composedParentIgnoringDocumentFragments(*node)) : nullptr;
#endif // USE(ATSPI)
}

LayoutRect AccessibilityNodeObject::checkboxOrRadioRect() const
{
    auto labels = Accessibility::labelsForElement(element());
    if (labels.isEmpty())
        return boundingBoxRect();

    auto* cache = axObjectCache();
    if (!cache)
        return boundingBoxRect();

    // A checkbox or radio button should encompass its label.
    auto selfRect = boundingBoxRect();
    for (auto& label : labels) {
        if (label->renderer()) {
            if (auto* axLabel = cache->getOrCreate(label.get()))
                selfRect.unite(axLabel->elementRect());
        }
    }
    return selfRect;
}

LayoutRect AccessibilityNodeObject::elementRect() const
{
    if (RefPtr input = dynamicDowncast<HTMLInputElement>(node()); input && (input->isCheckbox() || input->isRadioButton()))
        return checkboxOrRadioRect();

    return boundingBoxRect();
}

LayoutRect AccessibilityNodeObject::boundingBoxRect() const
{
    if (hasDisplayContents()) {
        LayoutRect contentsRect;
        for (const auto& child : const_cast<AccessibilityNodeObject*>(this)->unignoredChildren())
            contentsRect.unite(child->elementRect());

        if (!contentsRect.isEmpty())
            return contentsRect;
    }

    // Non-display:contents AccessibilityNodeObjects have no mechanism to return a size or position.
    // Instead, let's return a box at the position of an ancestor that does have a position, make it
    // the width of that ancestor, and about the height of a line of text, so it's clear this object is
    // a descendant of that ancestor.
    for (RefPtr<AccessibilityObject> ancestor = parentObject(); ancestor; ancestor = ancestor->parentObject()) {
        if (!ancestor->renderer())
            continue;
        auto ancestorRect = ancestor->elementRect();
        if (ancestorRect.isEmpty())
            continue;

        return {
            ancestorRect.location(),
            LayoutSize(ancestorRect.width(), LayoutUnit(std::min(10.0f, ancestorRect.height().toFloat())))
        };
    }
    return { };
}

Document* AccessibilityNodeObject::document() const
{
    if (!node())
        return nullptr;
    return &node()->document();
}

LocalFrameView* AccessibilityNodeObject::documentFrameView() const
{
    if (auto* node = this->node())
        return node->document().view();
    return AccessibilityObject::documentFrameView();
}

AccessibilityRole AccessibilityNodeObject::determineAccessibilityRole()
{
    AXTRACE("AccessibilityNodeObject::determineAccessibilityRole"_s);
    if ((m_ariaRole = determineAriaRoleAttribute()) != AccessibilityRole::Unknown)
        return m_ariaRole;

    return determineAccessibilityRoleFromNode();
}

bool AccessibilityNodeObject::matchesTextAreaRole() const
{
    return is<HTMLTextAreaElement>(node()) || hasContentEditableAttributeSet();
}

AccessibilityRole AccessibilityNodeObject::determineAccessibilityRoleFromNode(TreatStyleFormatGroupAsInline treatStyleFormatGroupAsInline) const
{
    AXTRACE("AccessibilityNodeObject::determineAccessibilityRoleFromNode"_s);

    RefPtr node = this->node();
    if (!node)
        return AccessibilityRole::Unknown;

    if (node->isTextNode())
        return AccessibilityRole::StaticText;

    RefPtr element = dynamicDowncast<HTMLElement>(*node);
    if (!element)
        return AccessibilityRole::Unknown;

    if (element->isLink())
        return AccessibilityRole::WebCoreLink;
    if (RefPtr selectElement = dynamicDowncast<HTMLSelectElement>(*element))
        return selectElement->multiple() ? AccessibilityRole::ListBox : AccessibilityRole::PopUpButton;
    if (is<HTMLImageElement>(*element) && element->hasAttributeWithoutSynchronization(usemapAttr))
        return AccessibilityRole::ImageMap;

    if (element->hasTagName(liTag))
        return AccessibilityRole::ListItem;
    if (element->hasTagName(buttonTag))
        return buttonRoleType();
    if (element->hasTagName(legendTag))
        return AccessibilityRole::Legend;
    if (element->hasTagName(canvasTag))
        return AccessibilityRole::Canvas;

    if (RefPtr input = dynamicDowncast<HTMLInputElement>(*element))
        return roleFromInputElement(*input);

    if (matchesTextAreaRole())
        return AccessibilityRole::TextArea;

    if (headingLevel())
        return AccessibilityRole::Heading;

    if (element->hasTagName(codeTag))
        return AccessibilityRole::Code;
    if (element->hasTagName(delTag) || element->hasTagName(sTag))
        return AccessibilityRole::Deletion;
    if (element->hasTagName(insTag))
        return AccessibilityRole::Insertion;
    if (element->hasTagName(subTag))
        return AccessibilityRole::Subscript;
    if (element->hasTagName(supTag))
        return AccessibilityRole::Superscript;
    if (element->hasTagName(strongTag))
        return AccessibilityRole::Strong;

    if (element->hasTagName(kbdTag)
        || element->hasTagName(preTag)
        || element->hasTagName(sampTag)
        || element->hasTagName(varTag)
        || element->hasTagName(citeTag))
        return treatStyleFormatGroupAsInline == TreatStyleFormatGroupAsInline::Yes ? AccessibilityRole::Inline : AccessibilityRole::TextGroup;

    if (element->hasTagName(ddTag))
        return AccessibilityRole::DescriptionListDetail;
    if (element->hasTagName(dtTag))
        return AccessibilityRole::DescriptionListTerm;
    if (element->hasTagName(dlTag))
        return AccessibilityRole::DescriptionList;

    if (element->hasTagName(menuTag)
        || element->hasTagName(olTag)
        || element->hasTagName(ulTag))
        return AccessibilityRole::List;

    if (element->hasTagName(fieldsetTag))
        return AccessibilityRole::Group;
    if (element->hasTagName(figureTag))
        return AccessibilityRole::Figure;
    if (element->hasTagName(pTag))
        return AccessibilityRole::Paragraph;

    if (is<HTMLLabelElement>(*element))
        return AccessibilityRole::Label;
    if (element->hasTagName(dfnTag)) {
        // Confusingly, the `dfn` element represents a term being defined, making it equivalent to the "term" ARIA
        // role rather than the "definition" ARIA role. The "definition" ARIA role has no HTML equivalent.
        // https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-dfn-element
        // https://w3c.github.io/aria/#term and https://w3c.github.io/aria/#definition
        return AccessibilityRole::Term;
    }
    if (element->hasTagName(divTag) && !isNonNativeTextControl())
        return AccessibilityRole::Generic;
    if (is<HTMLFormElement>(*element))
        return AccessibilityRole::Form;
    if (element->hasTagName(articleTag))
        return AccessibilityRole::DocumentArticle;
    if (element->hasTagName(mainTag))
        return AccessibilityRole::LandmarkMain;
    if (element->hasTagName(navTag))
        return AccessibilityRole::LandmarkNavigation;

    if (element->hasTagName(asideTag)) {
        if (ariaRoleAttribute() == AccessibilityRole::LandmarkComplementary || !isDescendantOfElementType({ asideTag, articleTag, sectionTag, navTag }))
            return AccessibilityRole::LandmarkComplementary;

        // https://w3c.github.io/html-aam/#el-aside
        // When within a sectioning content elements, complementary landmarks must have accnames to acquire the role.
        return WebCore::hasAccNameAttribute(*element) ? AccessibilityRole::LandmarkComplementary : AccessibilityRole::Generic;
    }

    if (element->hasTagName(searchTag))
        return AccessibilityRole::LandmarkSearch;

    if (element->hasTagName(sectionTag)) {
        // https://w3c.github.io/html-aam/#el-section
        // The default role attribute value for the section element, region, became a landmark in ARIA 1.1.
        // The HTML AAM spec says it is "strongly recommended" that ATs only convey and provide navigation
        // for section elements which have names.
        return WebCore::hasAccNameAttribute(*element) ? AccessibilityRole::LandmarkRegion : AccessibilityRole::TextGroup;
    }
    if (element->hasTagName(addressTag))
        return AccessibilityRole::Group;
    if (element->hasTagName(blockquoteTag))
        return AccessibilityRole::Blockquote;
    if (element->hasTagName(captionTag) || element->hasTagName(figcaptionTag))
        return AccessibilityRole::Caption;
    if (element->hasTagName(dialogTag))
        return AccessibilityRole::ApplicationDialog;
    if (element->hasTagName(markTag) || equalLettersIgnoringASCIICase(getAttribute(roleAttr), "mark"_s))
        return AccessibilityRole::Mark;
    if (is<HTMLDetailsElement>(*element))
        return AccessibilityRole::Details;
    if (RefPtr summaryElement = dynamicDowncast<HTMLSummaryElement>(*element); summaryElement && summaryElement->isActiveSummary())
        return AccessibilityRole::Summary;

    // http://rawgit.com/w3c/aria/master/html-aam/html-aam.html
    // Output elements should be mapped to status role.
    if (isOutput())
        return AccessibilityRole::ApplicationStatus;

#if ENABLE(VIDEO)
    if (is<HTMLVideoElement>(*element))
        return AccessibilityRole::Video;
    if (is<HTMLAudioElement>(*element))
        return AccessibilityRole::Audio;
#endif

#if ENABLE(MODEL_ELEMENT)
    if (element->hasTagName(modelTag))
        return AccessibilityRole::Model;
#endif

    // The HTML element should not be exposed as an element. That's what the RenderView element does.
    if (element->hasTagName(htmlTag))
        return AccessibilityRole::Ignored;

    // There should only be one banner/contentInfo per page. If header/footer are being used within an article or section then it should not be exposed as whole page's banner/contentInfo.
    // https://w3c.github.io/html-aam/#el-header
    if (element->hasTagName(headerTag)) {
        if (!isDescendantOfElementType({ articleTag, asideTag, mainTag, navTag, sectionTag }))
            return AccessibilityRole::LandmarkBanner;
        return AccessibilityRole::Generic;
    }

    // http://webkit.org/b/190138 Footers should become contentInfo's if scoped to body (and consequently become a landmark).
    // It should remain a footer if scoped to main, sectioning elements (article, aside, nav, section) or root sectioning element (blockquote, details, dialog, fieldset, figure, td).
    // https://w3c.github.io/html-aam/#el-footer
    if (element->hasTagName(footerTag)) {
        if (!isDescendantOfElementType({ articleTag, asideTag, navTag, sectionTag, mainTag, blockquoteTag, detailsTag, dialogTag, fieldsetTag, figureTag, tdTag }))
            return AccessibilityRole::LandmarkContentInfo;
        return AccessibilityRole::Footer;
    }

    if (element->hasTagName(timeTag))
        return AccessibilityRole::Time;
    if (element->hasTagName(hrTag))
        return AccessibilityRole::HorizontalRule;
    if (element->hasTagName(emTag))
        return AccessibilityRole::Emphasis;
    if (element->hasTagName(hgroupTag))
        return AccessibilityRole::Group;

    // If the element does not have role, but it has ARIA attributes, or accepts tab focus, accessibility should fallback to exposing it as a group.
    if (supportsARIAAttributes() || canSetFocusAttribute() || element->isFocusable())
        return AccessibilityRole::Group;

    return AccessibilityRole::Unknown;
}

AccessibilityRole AccessibilityNodeObject::roleFromInputElement(const HTMLInputElement& input) const
{
    AXTRACE("AccessibilityNodeObject::roleFromInputElement"_s);
    ASSERT(dynamicDowncast<HTMLInputElement>(node()) == &input);

    if (input.isTextButton())
        return buttonRoleType();
    if (input.isSwitch())
        return AccessibilityRole::Switch;
    if (input.isCheckbox())
        return AccessibilityRole::Checkbox;
    if (input.isRadioButton())
        return AccessibilityRole::RadioButton;

    if (input.isTextField()) {
        // Text fields may have a combobox ancestor, in which case we want to return role combobox.
        // This was ARIA 1.1 practice, but it has been recommended against since. Keeping this heuristics here in order to support those sites that are still using this structure.
        bool foundCombobox = false;
        for (RefPtr ancestor = parentObject(); ancestor; ancestor = ancestor->parentObject()) {
            if (ancestor->isComboBox()) {
                foundCombobox = true;
                break;
            }
            if (!ancestor->isGroup() && ancestor->roleValue() != AccessibilityRole::Generic)
                break;
        }
        if (foundCombobox)
            return AccessibilityRole::ComboBox;

        return input.isSearchField() ? AccessibilityRole::SearchField : AccessibilityRole::TextField;
    }

    if (input.isDateField() || input.isDateTimeLocalField() || input.isMonthField() || input.isTimeField() || input.isWeekField())
        return AccessibilityRole::DateTime;
    if (input.isFileUpload())
        return AccessibilityRole::Button;
    if (input.isColorControl())
        return AccessibilityRole::ColorWell;
    if (input.isInputTypeHidden())
        return AccessibilityRole::Ignored;
    if (input.isRangeControl())
        return AccessibilityRole::Slider;

    // All other input type is treated as a text field.
    return AccessibilityRole::TextField;
}

bool AccessibilityNodeObject::isDescendantOfElementType(const HashSet<QualifiedName>& tagNames) const
{
    if (!m_node)
        return false;

    for (auto& ancestorElement : ancestorsOfType<Element>(*m_node)) {
        if (tagNames.contains(ancestorElement.tagQName()))
            return true;
    }
    return false;
}

void AccessibilityNodeObject::updateChildrenIfNecessary()
{
    if (needsToUpdateChildren())
        clearChildren();

    AccessibilityObject::updateChildrenIfNecessary();
}

void AccessibilityNodeObject::clearChildren()
{
    AccessibilityObject::clearChildren();
    m_childrenDirty = false;
}

void AccessibilityNodeObject::updateOwnedChildren()
{
    for (Ref child : ownedObjects()) {
        // If the child already exists as a DOM child, but is also in the owned objects, then
        // we need to re-order this child in the aria-owns order.
        m_children.removeFirst(child);
        addChild(downcast<AccessibilityObject>(child.get()));
    }
}

void AccessibilityNodeObject::addChildren()
{
    // If the need to add more children in addition to existing children arises,
    // childrenChanged should have been called, leaving the object with no children.
    ASSERT(!m_childrenInitialized);
    m_childrenInitialized = true;

    auto clearDirtySubtree = makeScopeExit([&] {
        m_subtreeDirty = false;
    });

    RefPtr node = this->node();
    if (!node || !canHaveChildren())
        return;

    // The only time we add children from the DOM tree to a node with a renderer is when it's a canvas.
    if (renderer() && !node->hasTagName(canvasTag))
        return;

    CheckedPtr cache = axObjectCache();
    if (!cache)
        return;

#if USE(ATSPI)
    // FIXME: Consider removing this ATSPI-only branch with https://bugs.webkit.org/show_bug.cgi?id=282117.
    for (auto* child = node->firstChild(); child; child = child->nextSibling())
        addChild(cache->getOrCreate(*child));
#else
    if (auto* containerNode = dynamicDowncast<ContainerNode>(*node)) {
        for (Ref child : composedTreeChildren(*containerNode))
            addChild(cache->getOrCreate(child.get()));
    }
#endif // USE(ATSPI)

    updateOwnedChildren();
}

bool AccessibilityNodeObject::canHaveChildren() const
{
    // When <noscript> is not being used (its renderer() == 0), ignore its children.
    if (node() && !renderer() && node()->hasTagName(noscriptTag))
        return false;
    // If this is an AccessibilityRenderObject, then it's okay if this object
    // doesn't have a node - there are some renderers that don't have associated
    // nodes, like scroll areas and css-generated text.

    // Elements that should not have children.
    switch (roleValue()) {
    case AccessibilityRole::Button:
#if !USE(ATSPI)
    // GTK/ATSPI layout tests expect popup buttons to have children.
    case AccessibilityRole::PopUpButton:
#endif
    case AccessibilityRole::Checkbox:
    case AccessibilityRole::RadioButton:
    case AccessibilityRole::Tab:
    case AccessibilityRole::ToggleButton:
    case AccessibilityRole::StaticText:
    case AccessibilityRole::ListBoxOption:
    case AccessibilityRole::ScrollBar:
    case AccessibilityRole::ProgressIndicator:
    case AccessibilityRole::Switch:
    case AccessibilityRole::MenuItemCheckbox:
    case AccessibilityRole::MenuItemRadio:
    case AccessibilityRole::Splitter:
    case AccessibilityRole::Meter:
        return false;
    default:
        return true;
    }
}

AXCoreObject::AccessibilityChildrenVector AccessibilityNodeObject::visibleChildren()
{
    // Only listboxes are asked for their visible children.
    // Native list boxes would be AccessibilityListBoxes, so only check for aria list boxes.
    if (ariaRoleAttribute() != AccessibilityRole::ListBox)
        return { };

    if (!childrenInitialized())
        addChildren();

    AccessibilityChildrenVector result;
    for (const auto& child : unignoredChildren()) {
        if (!child->isOffScreen())
            result.append(child);
    }
    return result;
}

bool AccessibilityNodeObject::computeIsIgnored() const
{
#ifndef NDEBUG
    // Double-check that an AccessibilityObject is never accessed before
    // it's been initialized.
    ASSERT(m_initialized);
#endif
    if (!node())
        return true;

    // Handle non-rendered text that is exposed through aria-hidden=false.
    if (node() && node()->isTextNode() && !renderer()) {
        // Fallback content in iframe nodes should be ignored.
        if (node()->parentNode() && node()->parentNode()->hasTagName(iframeTag) && node()->parentNode()->renderer())
            return true;

        // Whitespace only text elements should be ignored when they have no renderer.
        if (stringValue().containsOnly<isASCIIWhitespace>())
            return true;
    }

    AccessibilityObjectInclusion decision = defaultObjectInclusion();
    if (decision == AccessibilityObjectInclusion::IncludeObject)
        return false;
    if (decision == AccessibilityObjectInclusion::IgnoreObject)
        return true;

    auto role = roleValue();
    return role == AccessibilityRole::Ignored || role == AccessibilityRole::Unknown;
}

bool AccessibilityNodeObject::canvasHasFallbackContent() const
{
    RefPtr canvasElement = dynamicDowncast<HTMLCanvasElement>(node());
    // If it has any children that are elements, we'll assume it might be fallback
    // content. If it has no children or its only children are not elements
    // (e.g. just text nodes), it doesn't have fallback content.
    return canvasElement && childrenOfType<Element>(*canvasElement).first();
}

bool AccessibilityNodeObject::isNativeTextControl() const
{
    if (is<HTMLTextAreaElement>(node()))
        return true;

    RefPtr input = dynamicDowncast<HTMLInputElement>(node());
    return input && (input->isText() || input->isNumberField());
}

bool AccessibilityNodeObject::isSearchField() const
{
    Node* node = this->node();
    if (!node)
        return false;

    if (roleValue() == AccessibilityRole::SearchField)
        return true;

    RefPtr inputElement = dynamicDowncast<HTMLInputElement>(*node);
    if (!inputElement)
        return false;

    // Some websites don't label their search fields as such. However, they will
    // use the word "search" in either the form or input type. This won't catch every case,
    // but it will catch google.com for example.

    // Check the node name of the input type, sometimes it's "search".
    const AtomString& nameAttribute = getAttribute(nameAttr);
    if (nameAttribute.containsIgnoringASCIICase("search"_s))
        return true;

    // Check the form action and the name, which will sometimes be "search".
    RefPtr form = inputElement->form();
    if (form && (form->name().containsIgnoringASCIICase("search"_s) || form->action().containsIgnoringASCIICase("search"_s)))
        return true;

    return false;
}

bool AccessibilityNodeObject::isNativeImage() const
{
    Node* node = this->node();
    if (!node)
        return false;

    if (is<HTMLImageElement>(*node))
        return true;

    if (node->hasTagName(appletTag) || node->hasTagName(embedTag) || node->hasTagName(objectTag))
        return true;

    if (RefPtr input = dynamicDowncast<HTMLInputElement>(*node))
        return input->isImageButton();

    return false;
}

bool AccessibilityNodeObject::isSecureField() const
{
    RefPtr input = dynamicDowncast<HTMLInputElement>(node());
    if (!input || ariaRoleAttribute() != AccessibilityRole::Unknown)
        return false;
    return input->isSecureField();
}

bool AccessibilityNodeObject::isInputImage() const
{
    if (roleValue() != AccessibilityRole::Button)
        return false;
    RefPtr input = dynamicDowncast<HTMLInputElement>(node());
    return input && input->isImageButton();
}

bool AccessibilityNodeObject::isEnabled() const
{
    // ARIA says that the disabled status applies to the current element and all descendant elements.
    for (AccessibilityObject* object = const_cast<AccessibilityNodeObject*>(this); object; object = object->parentObject()) {
        const AtomString& disabledStatus = object->getAttribute(aria_disabledAttr);
        if (equalLettersIgnoringASCIICase(disabledStatus, "true"_s))
            return false;
        if (equalLettersIgnoringASCIICase(disabledStatus, "false"_s))
            break;
    }

    if (roleValue() == AccessibilityRole::HorizontalRule)
        return false;

    RefPtr element = dynamicDowncast<Element>(node());
    return !element || !element->isDisabledFormControl();
}

bool AccessibilityNodeObject::isIndeterminate() const
{
    if (supportsCheckedState())
        return checkboxOrRadioValue() == AccessibilityButtonState::Mixed;

    // We handle this for native <progress> elements in AccessibilityProgressIndicator::isIndeterminate.
    if (ariaRoleAttribute() == AccessibilityRole::ProgressIndicator)
        return !hasARIAValueNow();

    return false;
}

bool AccessibilityNodeObject::isPressed() const
{
    if (!isButton())
        return false;

    Node* node = this->node();
    if (!node)
        return false;

    // If this is an toggle button, check the aria-pressed attribute rather than node()->active()
    if (isToggleButton())
        return equalLettersIgnoringASCIICase(getAttribute(aria_pressedAttr), "true"_s);

    RefPtr element = dynamicDowncast<Element>(*node);
    return element && element->active();
}

bool AccessibilityNodeObject::isChecked() const
{
    Node* node = this->node();
    if (!node)
        return false;

    // First test for native checkedness semantics
    if (RefPtr input = dynamicDowncast<HTMLInputElement>(*node))
        return input->matchesCheckedPseudoClass();

    // Else, if this is an ARIA checkbox or radio, respect the aria-checked attribute
    bool validRole = false;
    switch (ariaRoleAttribute()) {
    case AccessibilityRole::RadioButton:
    case AccessibilityRole::Checkbox:
    case AccessibilityRole::MenuItem:
    case AccessibilityRole::MenuItemCheckbox:
    case AccessibilityRole::MenuItemRadio:
    case AccessibilityRole::Switch:
    case AccessibilityRole::TreeItem:
        validRole = true;
        break;
    default:
        break;
    }

    if (validRole && equalLettersIgnoringASCIICase(getAttribute(aria_checkedAttr), "true"_s))
        return true;

    return false;
}

bool AccessibilityNodeObject::isMultiSelectable() const
{
    const AtomString& ariaMultiSelectable = getAttribute(aria_multiselectableAttr);
    if (equalLettersIgnoringASCIICase(ariaMultiSelectable, "true"_s))
        return true;
    if (equalLettersIgnoringASCIICase(ariaMultiSelectable, "false"_s))
        return false;

    RefPtr select = dynamicDowncast<HTMLSelectElement>(node());
    return select && select->multiple();
}

bool AccessibilityNodeObject::isRequired() const
{
    RefPtr formControlElement = dynamicDowncast<HTMLFormControlElement>(node());
    if (formControlElement && formControlElement->isRequired())
        return true;

    const AtomString& requiredValue = getAttribute(aria_requiredAttr);
    if (equalLettersIgnoringASCIICase(requiredValue, "true"_s))
        return true;
    if (equalLettersIgnoringASCIICase(requiredValue, "false"_s))
        return false;

    return false;
}

String AccessibilityNodeObject::accessKey() const
{
    auto* element = this->element();
    return element ? element->attributeWithoutSynchronization(accesskeyAttr) : String();
}

bool AccessibilityNodeObject::supportsDropping() const
{
    return determineDropEffects().size();
}

bool AccessibilityNodeObject::supportsDragging() const
{
    const AtomString& grabbed = getAttribute(aria_grabbedAttr);
    return equalLettersIgnoringASCIICase(grabbed, "true"_s) || equalLettersIgnoringASCIICase(grabbed, "false"_s) || hasAttribute(draggableAttr);
}

bool AccessibilityNodeObject::isGrabbed()
{
#if ENABLE(DRAG_SUPPORT)
    if (RefPtr localMainFrame = this->localMainFrame()) {
        if (localMainFrame->eventHandler().draggingElement() == element())
            return true;
    }
#endif

    return elementAttributeValue(aria_grabbedAttr);
}

Vector<String> AccessibilityNodeObject::determineDropEffects() const
{
    // Order is aria-dropeffect, dropzone, webkitdropzone
    const AtomString& dropEffects = getAttribute(aria_dropeffectAttr);
    if (!dropEffects.isEmpty())
        return makeStringByReplacingAll(dropEffects.string(), '\n', ' ').split(' ');

    auto dropzone = getAttribute(dropzoneAttr);
    if (!dropzone.isEmpty())
        return Vector<String> { dropzone };

    auto webkitdropzone = getAttribute(webkitdropzoneAttr);
    if (!webkitdropzone.isEmpty())
        return Vector<String> { webkitdropzone };

    // FIXME: We should return drop effects for elements with `dragenter` and `dragover` event handlers.
    // dropzone and webkitdropzone used to serve this purpose, but are deprecated in favor of the
    // aforementioned event handlers.
    //
    // https://html.spec.whatwg.org/dev/obsolete.html:
    // "dropzone on all elements: Use script to handle the dragenter and dragover events instead."
    return { };
}

bool AccessibilityNodeObject::supportsARIAOwns() const
{
    return !getAttribute(aria_ownsAttr).isEmpty();
}

AXCoreObject::AccessibilityChildrenVector AccessibilityNodeObject::radioButtonGroup() const
{
    AccessibilityChildrenVector result;

    if (auto* input = dynamicDowncast<HTMLInputElement>(node())) {
        auto radioButtonGroup = input->radioButtonGroup();
        result.reserveInitialCapacity(radioButtonGroup.size());

        WeakPtr cache = axObjectCache();
        for (auto& radioSibling : radioButtonGroup) {
            if (!cache)
                break;
            if (auto* object = cache->getOrCreate(radioSibling.ptr()))
                result.append(*object);
        }
    }

    return result;
}

unsigned AccessibilityNodeObject::headingLevel() const
{
    // headings can be in block flow and non-block flow
    Node* node = this->node();
    if (!node)
        return 0;

    if (isHeading()) {
        if (auto level = getIntegralAttribute(aria_levelAttr); level > 0)
            return level;
    }

    if (node->hasTagName(h1Tag))
        return 1;

    if (node->hasTagName(h2Tag))
        return 2;

    if (node->hasTagName(h3Tag))
        return 3;

    if (node->hasTagName(h4Tag))
        return 4;

    if (node->hasTagName(h5Tag))
        return 5;

    if (node->hasTagName(h6Tag))
        return 6;

    return 0;
}

String AccessibilityNodeObject::valueDescription() const
{
    if (!isRangeControl())
        return String();

    return getAttribute(aria_valuetextAttr).string();
}

float AccessibilityNodeObject::valueForRange() const
{
    if (RefPtr input = dynamicDowncast<HTMLInputElement>(node()); input && input->isRangeControl())
        return input->valueAsNumber();

    if (!isRangeControl())
        return 0.0f;

    // In ARIA 1.1, the implicit value for aria-valuenow on a spin button is 0.
    // For other roles, it is half way between aria-valuemin and aria-valuemax.
    auto& value = getAttribute(aria_valuenowAttr);
    if (!value.isEmpty())
        return value.toFloat();

    return isSpinButton() ? 0 : (minValueForRange() + maxValueForRange()) / 2;
}

float AccessibilityNodeObject::maxValueForRange() const
{
    if (RefPtr input = dynamicDowncast<HTMLInputElement>(node()); input && input->isRangeControl())
        return input->maximum();

    if (!isRangeControl())
        return 0.0f;

    auto& value = getAttribute(aria_valuemaxAttr);
    if (!value.isEmpty())
        return value.toFloat();

    // In ARIA 1.1, the implicit value for aria-valuemax on a spin button
    // is that there is no maximum value. For other roles, it is 100.
    return isSpinButton() ? std::numeric_limits<float>::max() : 100.0f;
}

float AccessibilityNodeObject::minValueForRange() const
{
    if (RefPtr input = dynamicDowncast<HTMLInputElement>(node()); input && input->isRangeControl())
        return input->minimum();

    if (!isRangeControl())
        return 0.0f;

    auto& value = getAttribute(aria_valueminAttr);
    if (!value.isEmpty())
        return value.toFloat();

    // In ARIA 1.1, the implicit value for aria-valuemin on a spin button
    // is that there is no minimum value. For other roles, it is 0.
    return isSpinButton() ? -std::numeric_limits<float>::max() : 0.0f;
}

float AccessibilityNodeObject::stepValueForRange() const
{
    return getAttribute(stepAttr).toFloat();
}

AccessibilityOrientation AccessibilityNodeObject::orientation() const
{
    const AtomString& ariaOrientation = getAttribute(aria_orientationAttr);
    if (equalLettersIgnoringASCIICase(ariaOrientation, "horizontal"_s))
        return AccessibilityOrientation::Horizontal;
    if (equalLettersIgnoringASCIICase(ariaOrientation, "vertical"_s))
        return AccessibilityOrientation::Vertical;
    if (equalLettersIgnoringASCIICase(ariaOrientation, "undefined"_s))
        return AccessibilityOrientation::Undefined;

    // In ARIA 1.1, the implicit value of aria-orientation changed from horizontal
    // to undefined on all roles that don't have their own role-specific values. In
    // addition, the implicit value of combobox became undefined.
    if (isComboBox() || isRadioGroup() || isTreeGrid())
        return AccessibilityOrientation::Undefined;

    if (isScrollbar() || isListBox() || isMenu() || isTree())
        return AccessibilityOrientation::Vertical;

    if (isMenuBar() || isSplitter() || isTabList() || isToolbar() || isSlider())
        return AccessibilityOrientation::Horizontal;

    return AccessibilityObject::orientation();
}

bool AccessibilityNodeObject::isBusy() const
{
    return elementAttributeValue(aria_busyAttr);
}

bool AccessibilityNodeObject::isRadioInput() const
{
    auto* inputElement = dynamicDowncast<HTMLInputElement>(node());
    return inputElement ? inputElement->isRadioButton() : false;
}

bool AccessibilityNodeObject::isFieldset() const
{
    Node* node = this->node();
    if (!node)
        return false;

    return node->hasTagName(fieldsetTag);
}

AccessibilityButtonState AccessibilityNodeObject::checkboxOrRadioValue() const
{
    if (auto* input = dynamicDowncast<HTMLInputElement>(node()); input && (input->isCheckbox() || input->isRadioButton()))
        return input->indeterminate() && !input->isSwitch() ? AccessibilityButtonState::Mixed : isChecked() ? AccessibilityButtonState::On : AccessibilityButtonState::Off;

    return AccessibilityObject::checkboxOrRadioValue();
}

#if ENABLE(AX_THREAD_TEXT_APIS)
TextEmissionBehavior AccessibilityNodeObject::emitTextAfterBehavior() const
{
    RefPtr node = this->node();
    if (!node)
        return TextEmissionBehavior::None;

    if (is<HTMLParagraphElement>(*node)) {
        // TextIterator only emits a double-newline for paragraphs conditionally (see shouldEmitExtraNewlineForNode)
        // based on collapsed margin size. But the spec (https://html.spec.whatwg.org/multipage/dom.html#the-innertext-idl-attribute) says:
        //   > If node is a p element, then append 2 (a required line break count) at the beginning and end of items.
        // And Chrome seems to follow the spec: https://chromium.googlesource.com/chromium/src.git/+/8ff781cd5c1aabca068247de9a3f143645e80422
        // WebKit tried to make this change in TextIterator, but it was reverted:
        // https://github.com/WebKit/WebKit/commit/d206c2daf7219264b2c9b0cf0ee4cdce2450445b
        //
        // It's easier to unconditionally emit a double newline, so let's do that for now, since it's more spec-compliant anyways.
        return TextEmissionBehavior::DoubleNewline;
    }

    if (WebCore::shouldEmitNewlinesBeforeAndAfterNode(*node))
        return TextEmissionBehavior::Newline;

    if (CheckedPtr cell = dynamicDowncast<RenderTableCell>(node->renderer()); cell && cell->nextCell()) {
        // https://html.spec.whatwg.org/multipage/dom.html#the-innertext-idl-attribute
        // > If node's computed value of 'display' is 'table-cell', and node's CSS box is not the last 'table-cell'
        // > box of its enclosing 'table-row' box, then append a string containing a single U+0009 TAB code point to items.
        return TextEmissionBehavior::Tab;
    }
    return TextEmissionBehavior::None;
}
#endif // ENABLE(AX_THREAD_TEXT_APIS)

Element* AccessibilityNodeObject::anchorElement() const
{
    Node* node = this->node();
    if (!node)
        return nullptr;

    AXObjectCache* cache = axObjectCache();
    if (!cache)
        return nullptr;

    // search up the DOM tree for an anchor element
    // NOTE: this assumes that any non-image with an anchor is an HTMLAnchorElement
    for ( ; node; node = node->parentNode()) {
        if (is<HTMLAnchorElement>(*node) || (node->renderer() && cache->getOrCreate(node->renderer())->isLink()))
            return downcast<Element>(node);
    }

    return nullptr;
}

RefPtr<Element> AccessibilityNodeObject::popoverTargetElement() const
{
    WeakPtr formControlElement = dynamicDowncast<HTMLFormControlElement>(node());
    return formControlElement ? formControlElement->popoverTargetElement() : nullptr;
}

AccessibilityObject* AccessibilityNodeObject::internalLinkElement() const
{
    // We don't currently support ARIA links as internal link elements, so exit early if anchorElement() is not a native HTMLAnchorElement.
    WeakPtr anchor = dynamicDowncast<HTMLAnchorElement>(anchorElement());
    if (!anchor)
        return nullptr;

    auto linkURL = anchor->href();
    auto fragmentIdentifier = linkURL.fragmentIdentifier();
    if (fragmentIdentifier.isEmpty())
        return nullptr;

    // Check if URL is the same as current URL
    auto* document = this->document();
    if (!document || !equalIgnoringFragmentIdentifier(document->url(), linkURL))
        return nullptr;

    RefPtr linkedNode = document->findAnchor(fragmentIdentifier);
    // The element we find may not be accessible, so find the first accessible object.
    return firstAccessibleObjectFromNode(linkedNode.get());
}

bool AccessibilityNodeObject::toggleDetailsAncestor()
{
    for (auto* node = this->node(); node; node = node->parentOrShadowHostNode()) {
        if (auto* details = dynamicDowncast<HTMLDetailsElement>(node)) {
            details->toggleOpen();
            return true;
        }
    }
    return false;
}

static RefPtr<Element> nodeActionElement(Node& node)
{
    if (RefPtr input = dynamicDowncast<HTMLInputElement>(node)) {
        if (!input->isDisabledFormControl() && (input->isRadioButton() || input->isCheckbox() || input->isTextButton() || input->isFileUpload() || input->isImageButton()))
            return input;
    } else if (node.hasTagName(buttonTag) || node.hasTagName(selectTag))
        return &downcast<Element>(node);

    return nullptr;
}

static Element* nativeActionElement(Node* start)
{
    if (!start)
        return nullptr;

    // Do a deep-dive to see if any nodes should be used as the action element.
    // We have to look at Nodes, since this method should only be called on objects that do not have children (like buttons).
    // It solves the problem when authors put role="button" on a group and leave the actual button inside the group.

    for (Node* child = start->firstChild(); child; child = child->nextSibling()) {
        if (RefPtr element = nodeActionElement(*child))
            return element.get();

        if (Element* subChild = nativeActionElement(child))
            return subChild;
    }
    return nullptr;
}

Element* AccessibilityNodeObject::actionElement() const
{
    Node* node = this->node();
    if (!node)
        return nullptr;

    if (RefPtr element = nodeActionElement(*node))
        return element.get();

    if (AccessibilityObject::isARIAInput(ariaRoleAttribute()))
        return downcast<Element>(node);

    switch (roleValue()) {
    case AccessibilityRole::Button:
    case AccessibilityRole::PopUpButton:
    case AccessibilityRole::ToggleButton:
    case AccessibilityRole::Tab:
    case AccessibilityRole::MenuItem:
    case AccessibilityRole::MenuItemCheckbox:
    case AccessibilityRole::MenuItemRadio:
    case AccessibilityRole::ListItem:
        // Check if the author is hiding the real control element inside the ARIA element.
        if (Element* nativeElement = nativeActionElement(node))
            return nativeElement;
        return downcast<Element>(node);
    default:
        break;
    }

    if (auto* element = anchorElement())
        return element;

    if (auto* clickableObject = this->clickableSelfOrAncestor())
        return clickableObject->element();

    return nullptr;
}

bool AccessibilityNodeObject::hasClickHandler() const
{
    RefPtr element = this->element();
    return element && element->hasAnyEventListeners({ eventNames().clickEvent, eventNames().mousedownEvent, eventNames().mouseupEvent });
}

bool AccessibilityNodeObject::isDescendantOfBarrenParent() const
{
    if (!m_isIgnoredFromParentData.isNull())
        return m_isIgnoredFromParentData.isDescendantOfBarrenParent;

    for (AccessibilityObject* object = parentObject(); object; object = object->parentObject()) {
        if (!object->canHaveChildren())
            return true;
    }

    return false;
}

void AccessibilityNodeObject::alterRangeValue(StepAction stepAction)
{
    if (roleValue() != AccessibilityRole::Slider && roleValue() != AccessibilityRole::SpinButton)
        return;

    auto element = this->element();
    if (!element || element->isDisabledFormControl())
        return;

    if (!getAttribute(stepAttr).isEmpty())
        changeValueByStep(stepAction);
    else
        changeValueByPercent(stepAction == StepAction::Increment ? 5 : -5);
}

void AccessibilityNodeObject::increment()
{
    UserGestureIndicator gestureIndicator(IsProcessingUserGesture::Yes, document());
    alterRangeValue(StepAction::Increment);
}

void AccessibilityNodeObject::decrement()
{
    UserGestureIndicator gestureIndicator(IsProcessingUserGesture::Yes, document());
    alterRangeValue(StepAction::Decrement);
}

static bool dispatchSimulatedKeyboardUpDownEvent(AccessibilityObject* object, const KeyboardEvent::Init& keyInit)
{
    // In case the keyboard event causes this element to be removed.
    Ref<AccessibilityObject> protectedObject(*object);

    bool handled = false;
    if (auto* node = object->node()) {
        auto event = KeyboardEvent::create(eventNames().keydownEvent, keyInit, Event::IsTrusted::Yes);
        node->dispatchEvent(event);
        handled |= event->defaultHandled();
    }

    // Ensure node is still valid and wasn't removed after the keydown.
    if (auto* node = object->node()) {
        auto event = KeyboardEvent::create(eventNames().keyupEvent, keyInit, Event::IsTrusted::Yes);
        node->dispatchEvent(event);
        handled |= event->defaultHandled();
    }
    return handled;
}

static void InitializeLegacyKeyInitProperties(KeyboardEvent::Init &keyInit, const AccessibilityObject& object)
{
    keyInit.which = keyInit.keyCode;
    keyInit.code = keyInit.key;

    keyInit.view = object.document()->windowProxy();
    keyInit.cancelable = true;
    keyInit.composed = true;
    keyInit.bubbles = true;
}

bool AccessibilityNodeObject::performDismissAction()
{
    auto keyInit = KeyboardEvent::Init();
    keyInit.key = "Escape"_s;
    keyInit.keyCode = 0x1b;
    keyInit.keyIdentifier = "U+001B"_s;
    InitializeLegacyKeyInitProperties(keyInit, *this);

    return dispatchSimulatedKeyboardUpDownEvent(this, keyInit);
}

// Fire a keyboard event if we were not able to set this value natively.
bool AccessibilityNodeObject::postKeyboardKeysForValueChange(StepAction stepAction)
{
    auto keyInit = KeyboardEvent::Init();
    bool isLTR = page()->userInterfaceLayoutDirection() == UserInterfaceLayoutDirection::LTR;
    // https://w3c.github.io/aria/#spinbutton
    // `spinbutton` elements don't have an implicit orientation, but the spec does say:
    //     > Authors SHOULD also ensure the up and down arrows on a keyboard perform the increment and decrement functions
    // So let's force a vertical orientation for `spinbutton`s so we simulate the correct keypress (either up or down).
    bool vertical = orientation() == AccessibilityOrientation::Vertical || roleValue() == AccessibilityRole::SpinButton;

    // The goal is to mimic existing keyboard dispatch completely, so that this is indistinguishable from a real key press.
    typedef enum { left = 37, up = 38, right = 39, down = 40 } keyCode;
    keyInit.key = stepAction == StepAction::Increment ? (vertical ? "ArrowUp"_s : (isLTR ? "ArrowRight"_s : "ArrowLeft"_s)) : (vertical ? "ArrowDown"_s : (isLTR ? "ArrowLeft"_s : "ArrowRight"_s));
    keyInit.keyCode = stepAction == StepAction::Increment ? (vertical ? keyCode::up : (isLTR ? keyCode::right : keyCode::left)) : (vertical ? keyCode::down : (isLTR ? keyCode::left : keyCode::right));
    keyInit.keyIdentifier = stepAction == StepAction::Increment ? (vertical ? "Up"_s : (isLTR ? "Right"_s : "Left"_s)) : (vertical ? "Down"_s : (isLTR ? "Left"_s : "Right"_s));

    InitializeLegacyKeyInitProperties(keyInit, *this);

    return dispatchSimulatedKeyboardUpDownEvent(this, keyInit);
}

void AccessibilityNodeObject::setNodeValue(StepAction stepAction, float value)
{
    bool didSet = setValue(String::number(value));

    if (didSet) {
        if (auto* cache = axObjectCache())
            cache->postNotification(this, document(), AXNotification::ValueChanged);
    } else
        postKeyboardKeysForValueChange(stepAction);
}

void AccessibilityNodeObject::changeValueByStep(StepAction stepAction)
{
    float step = stepValueForRange();
    float value = valueForRange();

    value += stepAction == StepAction::Increment ? step : -step;
    setNodeValue(stepAction, value);
}

void AccessibilityNodeObject::changeValueByPercent(float percentChange)
{
    if (!percentChange)
        return;

    float range = maxValueForRange() - minValueForRange();
    float step = range * (percentChange / 100);
    float value = valueForRange();

    // Make sure the specified percent will cause a change of one integer step or larger.
    if (std::abs(step) < 1)
        step = std::abs(percentChange) * (1 / percentChange);

    value += step;
    setNodeValue(percentChange > 0 ? StepAction::Increment : StepAction::Decrement, value);
}

bool AccessibilityNodeObject::elementAttributeValue(const QualifiedName& attributeName) const
{
    return equalLettersIgnoringASCIICase(getAttribute(attributeName), "true"_s);
}

const String AccessibilityNodeObject::liveRegionStatus() const
{
    const auto& liveRegionStatus = getAttribute(aria_liveAttr);
    if (liveRegionStatus.isEmpty())
        return defaultLiveRegionStatusForRole(roleValue());

    return liveRegionStatus;
}

const String AccessibilityNodeObject::liveRegionRelevant() const
{
    const auto& relevant = getAttribute(aria_relevantAttr);
    // Default aria-relevant = "additions text".
    if (relevant.isEmpty())
        return "additions text"_s;

    return relevant;
}

bool AccessibilityNodeObject::liveRegionAtomic() const
{
    const auto& atomic = getAttribute(aria_atomicAttr);
    if (equalLettersIgnoringASCIICase(atomic, "true"_s))
        return true;
    if (equalLettersIgnoringASCIICase(atomic, "false"_s))
        return false;

    // WAI-ARIA "alert" and "status" roles have an implicit aria-atomic value of true.
    switch (roleValue()) {
    case AccessibilityRole::ApplicationAlert:
    case AccessibilityRole::ApplicationStatus:
        return true;
    default:
        return false;
    }
}

// This function is like a cross-platform version of - (WebCoreTextMarkerRange*)textMarkerRange. It returns
// a Range that we can convert to a WebCoreTextMarkerRange in the Obj-C file
VisiblePositionRange AccessibilityNodeObject::visiblePositionRange() const
{
    RefPtr node = this->node();
    if (!node)
        return VisiblePositionRange();

    VisiblePosition startPos = firstPositionInOrBeforeNode(node.get());
    VisiblePosition endPos = lastPositionInOrAfterNode(node.get());

    // the VisiblePositions are equal for nodes like buttons, so adjust for that
    // FIXME: Really?  [button, 0] and [button, 1] are distinct (before and after the button)
    // I expect this code is only hit for things like empty divs? In which case I don't think
    // the behavior is correct here -- eseidel
    if (startPos == endPos) {
        endPos = endPos.next();
        if (endPos.isNull())
            endPos = startPos;
    }

    return { WTFMove(startPos), WTFMove(endPos) };
}

VisiblePositionRange AccessibilityNodeObject::selectedVisiblePositionRange() const
{
    auto* document = this->document();
    if (auto* localFrame = document ? document->frame() : nullptr) {
        if (auto selection = localFrame->selection().selection(); !selection.isNone())
            return selection;
    }
    return { };
}

int AccessibilityNodeObject::indexForVisiblePosition(const VisiblePosition& position) const
{
    RefPtr node = this->node();
    if (!node)
        return 0;
    // We need to consider replaced elements for GTK, as they will be
    // presented with the 'object replacement character' (0xFFFC).
    TextIteratorBehaviors behaviors;
#if USE(ATSPI)
    behaviors.add(TextIteratorBehavior::EmitsObjectReplacementCharacters);
#endif
    return WebCore::indexForVisiblePosition(*node, position, behaviors);
}

VisiblePosition AccessibilityNodeObject::visiblePositionForIndex(int index) const
{
    RefPtr node = this->node();
    if (!node)
        return { };
#if USE(ATSPI)
    // We need to consider replaced elements for GTK, as they will be presented with the 'object replacement character' (0xFFFC).
    return WebCore::visiblePositionForIndex(index, node.get(), TextIteratorBehavior::EmitsObjectReplacementCharacters);
#else
    return visiblePositionForIndexUsingCharacterIterator(*node, index);
#endif
}

VisiblePositionRange AccessibilityNodeObject::visiblePositionRangeForLine(unsigned lineCount) const
{
    if (!lineCount)
        return { };

    auto* document = this->document();
    auto* renderView = document ? document->renderView() : nullptr;
    if (!renderView)
        return { };

    // iterate over the lines
    // FIXME: This is wrong when lineNumber is lineCount+1, because nextLinePosition takes you to the last offset of the last line.
    VisiblePosition position = renderView->positionForPoint(IntPoint(), HitTestSource::User, nullptr);
    while (--lineCount) {
        auto previousLinePosition = position;
        position = nextLinePosition(position, 0);
        if (position.isNull() || position == previousLinePosition)
            return VisiblePositionRange();
    }

    // make a caret selection for the marker position, then extend it to the line
    // NOTE: Ignores results of sel.modify because it returns false when starting at an empty line.
    // The resulting selection in that case will be a caret at position.
    FrameSelection selection;
    selection.setSelection(position);
    selection.modify(FrameSelection::Alteration::Extend, SelectionDirection::Right, TextGranularity::LineBoundary);
    return selection.selection();
}

bool AccessibilityNodeObject::isGenericFocusableElement() const
{
    if (!canSetFocusAttribute())
        return false;

    // If it's a control, it's not generic.
    if (isControl())
        return false;

    AccessibilityRole role = roleValue();
    if (role == AccessibilityRole::Video || role == AccessibilityRole::Audio)
        return false;

    // If it has an aria role, it's not generic.
    if (m_ariaRole != AccessibilityRole::Unknown)
        return false;

    // If the content editable attribute is set on this element, that's the reason
    // it's focusable, and existing logic should handle this case already - so it's not a
    // generic focusable element.

    if (hasContentEditableAttributeSet())
        return false;

    // The web area and body element are both focusable, but existing logic handles these
    // cases already, so we don't need to include them here.
    if (role == AccessibilityRole::WebArea)
        return false;
    if (node() && node()->hasTagName(bodyTag))
        return false;

    // An SVG root is focusable by default, but it's probably not interactive, so don't
    // include it. It can still be made accessible by giving it an ARIA role.
    if (role == AccessibilityRole::SVGRoot)
        return false;

    return true;
}

AccessibilityObject* AccessibilityNodeObject::controlForLabelElement() const
{
    auto* labelElement = labelElementContainer();
    return labelElement ? axObjectCache()->getOrCreate(Accessibility::controlForLabelElement(*labelElement).get()) : nullptr;
}

String AccessibilityNodeObject::ariaAccessibilityDescription() const
{
    String ariaLabeledBy = ariaLabeledByAttribute();
    if (!ariaLabeledBy.isEmpty())
        return ariaLabeledBy;

    auto ariaLabel = getAttributeTrimmed(aria_labelAttr);
    if (!ariaLabel.isEmpty())
        return ariaLabel;

    return String();
}

AccessibilityObject* AccessibilityNodeObject::captionForFigure() const
{
    if (!isFigureElement())
        return nullptr;

    AXObjectCache* cache = axObjectCache();
    if (!cache)
        return nullptr;

    Node* node = this->node();
    for (Node* child = node->firstChild(); child; child = child->nextSibling()) {
        if (child->hasTagName(figcaptionTag))
            return cache->getOrCreate(*child);
    }
    return nullptr;
}

bool AccessibilityNodeObject::usesAltTagForTextComputation() const
{
    bool usesAltTag = isImage() || isInputImage() || isNativeImage() || isCanvas() || (node() && node()->hasTagName(imgTag));
#if ENABLE(MODEL_ELEMENT)
    usesAltTag |= isModel();
#endif
    return usesAltTag;
}

bool AccessibilityNodeObject::isLabelable() const
{
    Node* node = this->node();
    if (!node)
        return false;
    return is<HTMLInputElement>(*node) || isControl() || isProgressIndicator() || isMeter();
}

String AccessibilityNodeObject::textAsLabelFor(const AccessibilityObject& labeledObject) const
{
    auto labelAttribute = getAttributeTrimmed(aria_labelAttr);
    if (!labelAttribute.isEmpty())
        return labelAttribute;

    labelAttribute = getAttribute(altAttr);
    if (!labelAttribute.isEmpty())
        return labelAttribute;

    labelAttribute = getAttribute(titleAttr);
    if (!labelAttribute.isEmpty())
        return labelAttribute;

    if (isAccessibilityLabelInstance()) {
        StringBuilder builder;
        for (const auto& child : const_cast<AccessibilityNodeObject*>(this)->unignoredChildren()) {
            if (child.ptr() == &labeledObject)
                continue;

            if (child->isListBox()) {
                auto selectedChildren = child->selectedChildren();
                for (const auto& selectedGrandChild : selectedChildren)
                    appendNameToStringBuilder(builder, accessibleNameForNode(*selectedGrandChild->node()));
                continue;
            }

            if (child->isComboBox()) {
                appendNameToStringBuilder(builder, child->stringValue());
                continue;
            }

            if (child->isTextControl()) {
                appendNameToStringBuilder(builder, child->text());
                continue;
            }

            if (child->isSlider() || child->isSpinButton()) {
                appendNameToStringBuilder(builder, String::number(child->valueForRange()));
                continue;
            }

            appendNameToStringBuilder(builder, child->textUnderElement());
        }
        if (builder.length())
            return builder.toString().trim(isASCIIWhitespace).simplifyWhiteSpace(isHTMLSpaceButNotLineBreak);
    }

    String text = this->text();
    if (!text.isEmpty())
        return text;
    return textUnderElement();
}

String AccessibilityNodeObject::textForLabelElements(Vector<Ref<HTMLElement>>&& labelElements) const
{
    // https://www.w3.org/TR/html-aam-1.0/#input-type-text-input-type-password-input-type-number-input-type-search-input-type-tel-input-type-email-input-type-url-and-textarea-element-accessible-name-computation
    // "...if more than one label is associated; concatenate by DOM order, delimited by spaces."
    StringBuilder result;

    WeakPtr cache = axObjectCache();
    for (auto& labelElement : labelElements) {
        RefPtr label = cache ? cache->getOrCreate(labelElement.ptr()) : nullptr;
        if (!label)
            continue;

        if (label.get() == this) {
            // This object labels itself, so use its textAsLabel.
            appendNameToStringBuilder(result, textAsLabelFor(*this));
            continue;
        }

        auto ariaLabeledBy = label->ariaLabeledByAttribute();
        if (!ariaLabeledBy.isEmpty())
            appendNameToStringBuilder(result, WTFMove(ariaLabeledBy));
#if PLATFORM(COCOA)
        else if (auto* axLabel = dynamicDowncast<AccessibilityLabel>(*label))
            appendNameToStringBuilder(result, axLabel->textAsLabelFor(*this));
#endif
        else
            appendNameToStringBuilder(result, accessibleNameForNode(labelElement.get()));
    }

    return result.toString();
}

HTMLLabelElement* AccessibilityNodeObject::labelElementContainer() const
{
    // The control element should not be considered part of the label.
    if (isControl())
        return nullptr;

    // Find an ancestor label element.
    for (auto* parentNode = node(); parentNode; parentNode = parentNode->parentNode()) {
        if (auto* label = dynamicDowncast<HTMLLabelElement>(*parentNode))
            return label;
    }
    return nullptr;
}

void AccessibilityNodeObject::labelText(Vector<AccessibilityText>& textOrder) const
{
    RefPtr element = this->element();
    if (!element)
        return;

    Vector<Ref<HTMLElement>> elementLabels;
    auto axLabels = labeledByObjects();
    if (axLabels.size()) {
        elementLabels.appendVector(WTF::compactMap(axLabels, [] (auto& axLabel) {
            return RefPtr { dynamicDowncast<HTMLElement>(axLabel->element()) };
        }));
    }
    if (!elementLabels.size())
        elementLabels = Accessibility::labelsForElement(element.get());

    String label = textForLabelElements(WTFMove(elementLabels));
    if (!label.isEmpty()) {
        textOrder.append({ WTFMove(label), isMeter() ? AccessibilityTextSource::Alternative : AccessibilityTextSource::LabelByElement });
        return;
    }

    auto ariaLabel = getAttributeTrimmed(aria_labelAttr);
    if (!ariaLabel.isEmpty()) {
        textOrder.append({ WTFMove(ariaLabel), AccessibilityTextSource::LabelByElement });
        return;
    }
}

bool AccessibilityNodeObject::hasTextAlternative() const
{
    // ARIA: section 2A, bullet #3 says if aria-labeledby or aria-label appears, it should
    // override the "label" element association.
    return ariaAccessibilityDescription().length();
}

void AccessibilityNodeObject::alternativeText(Vector<AccessibilityText>& textOrder) const
{
    if (isWebArea()) {
        String webAreaText = alternativeTextForWebArea();
        if (!webAreaText.isEmpty())
            textOrder.append(AccessibilityText(webAreaText, AccessibilityTextSource::Alternative));
        return;
    }

    ariaLabeledByText(textOrder);

    auto ariaLabel = getAttributeTrimmed(aria_labelAttr);
    if (!ariaLabel.isEmpty())
        textOrder.append(AccessibilityText(ariaLabel, AccessibilityTextSource::Alternative));

    if (usesAltTagForTextComputation()) {
        if (auto* renderImage = dynamicDowncast<RenderImage>(renderer())) {
            String renderAltText = renderImage->altText();

            // RenderImage will return title as a fallback from altText, but we don't want title here because we consider that in helpText.
            if (!renderAltText.isEmpty() && renderAltText != getAttribute(titleAttr)) {
                textOrder.append(AccessibilityText(renderAltText, AccessibilityTextSource::Alternative));
                return;
            }
        }
        // Images should use alt as long as the attribute is present, even if empty.
        // Otherwise, it should fallback to other methods, like the title attribute.
        const AtomString& alt = getAttribute(altAttr);
        if (!alt.isEmpty())
            textOrder.append(AccessibilityText(alt, AccessibilityTextSource::Alternative));
    }

    Node* node = this->node();
    if (!node)
        return;

    auto objectCache = axObjectCache();
    // The fieldset element derives its alternative text from the first associated legend element if one is available.
    if (RefPtr fieldset = dynamicDowncast<HTMLFieldSetElement>(*node); fieldset && objectCache) {
        AccessibilityObject* object = objectCache->getOrCreate(fieldset->legend());
        if (object && !object->isHidden())
            textOrder.append(AccessibilityText(accessibleNameForNode(*object->node()), AccessibilityTextSource::Alternative));
    }

    // The figure element derives its alternative text from the first associated figcaption element if one is available.
    if (isFigureElement()) {
        AccessibilityObject* captionForFigure = this->captionForFigure();
        if (captionForFigure && !captionForFigure->isHidden())
            textOrder.append(AccessibilityText(accessibleNameForNode(*captionForFigure->node()), AccessibilityTextSource::Alternative));
    }

    // Tree items missing a label are labeled by all child elements.
    if (isTreeItem() && ariaLabel.isEmpty() && ariaLabeledByAttribute().isEmpty())
        textOrder.append(AccessibilityText(accessibleNameForNode(*node), AccessibilityTextSource::Alternative));

#if ENABLE(MATHML)
    if (node->isMathMLElement())
        textOrder.append(AccessibilityText(getAttribute(MathMLNames::alttextAttr), AccessibilityTextSource::Alternative));
#endif
}

void AccessibilityNodeObject::visibleText(Vector<AccessibilityText>& textOrder) const
{
    WeakPtr node = this->node();
    if (!node)
        return;

    if (RefPtr input = dynamicDowncast<HTMLInputElement>(*node); input && input->isTextButton()) {
        textOrder.append(AccessibilityText(input->valueWithDefault(), AccessibilityTextSource::Visible));
        return;
    }

    // If this node isn't rendered, there's no inner text we can extract from a select element.
    if (!isAccessibilityRenderObject() && node->hasTagName(selectTag))
        return;

    if (dependsOnTextUnderElement()) {
        TextUnderElementMode mode;

        // Headings often include links as direct children. Those links need to be included in text under element.
        if (isHeading())
            mode.includeFocusableContent = true;

        String text = textUnderElement(mode);
        if (!text.isEmpty())
            textOrder.append(AccessibilityText(text, AccessibilityTextSource::Children));
    }
}

void AccessibilityNodeObject::helpText(Vector<AccessibilityText>& textOrder) const
{
    const AtomString& ariaHelp = getAttribute(aria_helpAttr);
    if (UNLIKELY(!ariaHelp.isEmpty()))
        textOrder.append(AccessibilityText(ariaHelp, AccessibilityTextSource::Help));

#if !PLATFORM(COCOA)
    String describedBy = ariaDescribedByAttribute();
    if (!describedBy.isEmpty())
        textOrder.append(AccessibilityText(describedBy, AccessibilityTextSource::Summary));
#endif

    if (isControl()) {
        // For controls, use their fieldset parent's described-by text if available.
        auto matchFunc = [] (const AccessibilityObject& object) {
            return object.isFieldset() && !object.ariaDescribedByAttribute().isEmpty();
        };
        if (const auto* parent = Accessibility::findAncestor<AccessibilityObject>(*this, false, WTFMove(matchFunc)))
            textOrder.append(AccessibilityText(parent->ariaDescribedByAttribute(), AccessibilityTextSource::Summary));
    }

    // Summary attribute used as help text on tables.
    const AtomString& summary = getAttribute(summaryAttr);
    if (!summary.isEmpty())
        textOrder.append(AccessibilityText(summary, AccessibilityTextSource::Summary));

    // The title attribute should be used as help text unless it is already being used as descriptive text.
    // However, when the title attribute is the only text alternative provided, it may be exposed as the
    // descriptive text. This is problematic in the case of meters because the HTML spec suggests authors
    // can expose units through this attribute. Therefore, if the element is a meter, change its source
    // type to AccessibilityTextSource::Help.
    const AtomString& title = getAttribute(titleAttr);
    if (!title.isEmpty()) {
        if (!isMeter() && !roleIgnoresTitle())
            textOrder.append(AccessibilityText(title, AccessibilityTextSource::TitleTag));
        else
            textOrder.append(AccessibilityText(title, AccessibilityTextSource::Help));
    }
}

void AccessibilityNodeObject::accessibilityText(Vector<AccessibilityText>& textOrder) const
{
    labelText(textOrder);
    alternativeText(textOrder);
    visibleText(textOrder);
    helpText(textOrder);

    String placeholder = placeholderValue();
    if (!placeholder.isEmpty())
        textOrder.append(AccessibilityText(placeholder, AccessibilityTextSource::Placeholder));
}

void AccessibilityNodeObject::ariaLabeledByText(Vector<AccessibilityText>& textOrder) const
{
    String ariaLabeledBy = ariaLabeledByAttribute();
    if (!ariaLabeledBy.isEmpty())
        textOrder.append(AccessibilityText(ariaLabeledBy, AccessibilityTextSource::Alternative));
}

String AccessibilityNodeObject::alternativeTextForWebArea() const
{
    // The WebArea description should follow this order:
    //     aria-label on the <html>
    //     title on the <html>
    //     <title> inside the <head> (of it was set through JS)
    //     name on the <html>
    // For iframes:
    //     aria-label on the <iframe>
    //     title on the <iframe>
    //     name on the <iframe>

    Document* document = this->document();
    if (!document)
        return String();

    // Check if the HTML element has an aria-label for the webpage.
    if (Element* documentElement = document->documentElement()) {
        const AtomString& ariaLabel = documentElement->attributeWithoutSynchronization(aria_labelAttr);
        if (!ariaLabel.isEmpty())
            return ariaLabel;
    }

    if (auto* owner = document->ownerElement()) {
        if (owner->hasTagName(frameTag) || owner->hasTagName(iframeTag)) {
            const AtomString& title = owner->attributeWithoutSynchronization(titleAttr);
            if (!title.isEmpty())
                return title;
        }
        return owner->getNameAttribute();
    }

    String documentTitle = document->title();
    if (!documentTitle.isEmpty())
        return documentTitle;

    if (auto* body = document->bodyOrFrameset())
        return body->getNameAttribute();

    return String();
}

String AccessibilityNodeObject::description() const
{
    // Static text should not have a description, it should only have a stringValue.
    if (roleValue() == AccessibilityRole::StaticText)
        return { };

    String ariaDescription = ariaAccessibilityDescription();
    if (!ariaDescription.isEmpty())
        return ariaDescription;

    if (usesAltTagForTextComputation()) {
        // Images should use alt as long as the attribute is present, even if empty.
        // Otherwise, it should fallback to other methods, like the title attribute.
        const AtomString& alt = getAttribute(altAttr);
        if (!alt.isNull())
            return alt;
    }

#if ENABLE(MATHML)
    if (is<MathMLElement>(node()))
        return getAttribute(MathMLNames::alttextAttr);
#endif

    // An element's descriptive text is comprised of title() (what's visible on the screen) and description() (other descriptive text).
    // Both are used to generate what a screen reader speaks.
    // If this point is reached (i.e. there's no accessibilityDescription) and there's no title(), we should fallback to using the title attribute.
    // The title attribute is normally used as help text (because it is a tooltip), but if there is nothing else available, this should be used (according to ARIA).
    // https://bugs.webkit.org/show_bug.cgi?id=170475: An exception is when the element is semantically unimportant. In those cases, title text should remain as help text.
    if (!roleIgnoresTitle()) {
        // title() can be an expensive operation because it can invoke textUnderElement for all descendants. Thus call it last.
        auto titleAttribute = getAttribute(titleAttr);
        if (!titleAttribute.isEmpty() && title().isEmpty())
            return titleAttribute;
    }

    return { };
}

// Returns whether the role was not intended to play a semantically meaningful part of the
// accessibility hierarchy. This applies to generic groups like <div>'s with no role value set.
bool AccessibilityNodeObject::roleIgnoresTitle() const
{
    if (ariaRoleAttribute() != AccessibilityRole::Unknown)
        return false;

    switch (roleValue()) {
    case AccessibilityRole::Generic:
    case AccessibilityRole::Unknown:
        return true;
    default:
        return false;
    }
}

String AccessibilityNodeObject::helpText() const
{
    WeakPtr node = this->node();
    if (!node)
        return { };

    const auto& ariaHelp = getAttribute(aria_helpAttr);
    if (UNLIKELY(!ariaHelp.isEmpty()))
        return ariaHelp;

    String describedBy = ariaDescribedByAttribute();
    if (!describedBy.isEmpty())
        return describedBy;

    String description = this->description();
    for (Node* ancestor = node.get(); ancestor; ancestor = ancestor->parentNode()) {
        if (auto* element = dynamicDowncast<HTMLElement>(ancestor)) {
            const auto& summary = element->getAttribute(summaryAttr);
            if (!summary.isEmpty())
                return summary;

            // The title attribute should be used as help text unless it is already being used as descriptive text.
            const auto& title = element->getAttribute(titleAttr);
            if (!title.isEmpty() && description != title)
                return title;
        }

        auto* cache = axObjectCache();
        if (!cache)
            return { };

        // Only take help text from an ancestor element if its a group or an unknown role. If help was
        // added to those kinds of elements, it is likely it was meant for a child element.
        if (auto* axAncestor = cache->getOrCreate(*ancestor)) {
            if (!axAncestor->isGroup() && axAncestor->roleValue() != AccessibilityRole::Unknown)
                break;
        }
    }

    return { };
}

URL AccessibilityNodeObject::url() const
{
    auto* node = this->node();
    if (RefPtr anchor = dynamicDowncast<HTMLAnchorElement>(node); anchor && isLink())
        return anchor->href();

    if (RefPtr image = dynamicDowncast<HTMLImageElement>(node); image && isImage())
        return image->src();

    if (RefPtr input = dynamicDowncast<HTMLInputElement>(node); input && isInputImage())
        return input->src();

#if ENABLE(VIDEO)
    if (RefPtr video = dynamicDowncast<HTMLVideoElement>(node); video && isVideo())
        return video->currentSrc();
#endif

    return URL();
}

unsigned AccessibilityNodeObject::hierarchicalLevel() const
{
    RefPtr element = dynamicDowncast<Element>(node());
    if (!element)
        return 0;

    if (!element->attributeWithoutSynchronization(aria_levelAttr).isEmpty())
        return element->getIntegralAttribute(aria_levelAttr);

    // Only tree item will calculate its level through the DOM currently.
    if (roleValue() != AccessibilityRole::TreeItem)
        return 0;

    // Hierarchy leveling starts at 1, to match the aria-level spec.
    // We measure tree hierarchy by the number of groups that the item is within.
    unsigned level = 1;
    for (AccessibilityObject* parent = parentObject(); parent; parent = parent->parentObject()) {
        AccessibilityRole parentRole = parent->ariaRoleAttribute();
        if (parentRole == AccessibilityRole::Group)
            level++;
        else if (parentRole == AccessibilityRole::Tree)
            break;
    }

    return level;
}

void AccessibilityNodeObject::setIsExpanded(bool expand)
{
    if (RefPtr details = dynamicDowncast<HTMLDetailsElement>(node())) {
        if (expand != details->hasAttribute(openAttr))
            details->toggleOpen();
    }
}

// When building the textUnderElement for an object, determine whether or not
// we should include the inner text of this given descendant object or skip it.
static bool shouldUseAccessibilityObjectInnerText(AccessibilityObject& object, TextUnderElementMode mode)
{
#if USE(ATSPI)
    // Only ATSPI ever sets IncludeAllChildren.
    // Do not use any heuristic if we are explicitly asking to include all the children.
    if (mode.childrenInclusion == TextUnderElementMode::Children::IncludeAllChildren)
        return true;
#endif // USE(ATSPI)

    // Consider this hypothetical example:
    // <div tabindex=0>
    //   <h2>
    //     Table of contents
    //   </h2>
    //   <a href="#start">Jump to start of book</a>
    //   <ul>
    //     <li><a href="#1">Chapter 1</a></li>
    //     <li><a href="#1">Chapter 2</a></li>
    //   </ul>
    // </div>
    //
    // The goal is to return a reasonable title for the outer container div, because
    // it's focusable - but without making its title be the full inner text, which is
    // quite long. As a heuristic, skip links, controls, and elements that are usually
    // containers with lots of children.

    // ARIA states that certain elements are not allowed to expose their children content for name calculation.
    if (mode.childrenInclusion == TextUnderElementMode::Children::IncludeNameFromContentsChildren
        && !object.accessibleNameDerivesFromContent())
        return false;

    if (equalLettersIgnoringASCIICase(object.getAttribute(aria_hiddenAttr), "true"_s))
        return false;

    // If something doesn't expose any children, then we can always take the inner text content.
    // This is what we want when someone puts an <a> inside a <button> for example.
    if (object.isDescendantOfBarrenParent())
        return true;

    // Skip focusable children, so we don't include the text of links and controls.
    if (object.canSetFocusAttribute() && !mode.includeFocusableContent)
        return false;

    // Skip big container elements like lists, tables, etc.
    if (is<AccessibilityList>(object))
        return false;

    if (auto* table = dynamicDowncast<AccessibilityTable>(object); table && table->isExposable())
        return false;

    if (object.isTree() || object.isCanvas())
        return false;

#if ENABLE(MODEL_ELEMENT)
    if (object.isModel())
        return false;
#endif

    return true;
}

static void appendNameToStringBuilder(StringBuilder& builder, String&& text, bool prependSpace)
{
    if (text.isEmpty())
        return;

    if (prependSpace && !isHTMLLineBreak(text[0]) && builder.length() && !isHTMLLineBreak(builder[builder.length() - 1]))
        builder.append(' ');
    builder.append(WTFMove(text));
}


static bool displayTypeNeedsSpace(DisplayType type)
{
    return type == DisplayType::Block
        || type == DisplayType::InlineBlock
        || type == DisplayType::InlineFlex
        || type == DisplayType::InlineGrid
        || type == DisplayType::InlineTable
        || type == DisplayType::TableCell;
}

static bool needsSpaceFromDisplay(AccessibilityObject& axObject)
{
    CheckedPtr renderer = axObject.renderer();
    if (is<RenderText>(renderer)) {
        // Never add a space for RenderTexts. They are inherently inline, but take their parent's style, which may
        // be block, erroneously adding a space.
        return false;
    }

    const auto* style = renderer ? &renderer->style() : nullptr;
    if (!style)
        style = axObject.style();

    return style ? displayTypeNeedsSpace(style->display()) : false;
}

static bool shouldPrependSpace(AccessibilityObject& object, AccessibilityObject* previousObject)
{
    return needsSpaceFromDisplay(object)
        || (previousObject && needsSpaceFromDisplay(*previousObject))
        || object.isControl()
        || (previousObject && previousObject->isControl());
}

String AccessibilityNodeObject::textUnderElement(TextUnderElementMode mode) const
{
    RefPtr node = this->node();
    if (auto* text = dynamicDowncast<Text>(node.get()))
        return !mode.isHidden() ? text->wholeText() : emptyString();

    const auto* style = this->style();
    mode.inHiddenSubtree = WebCore::isRenderHidden(style);
    // The Accname specification states that if the current node is hidden, and not directly
    // referenced by aria-labelledby or aria-describedby, and is not a host language text
    // alternative, the empty string should be returned.
    if (mode.isHidden() && node && !ancestorsOfType<HTMLCanvasElement>(*node).first()) {
        if (!labelForObjects().isEmpty() || !descriptionForObjects().isEmpty()) {
            // This object is a hidden label or description for another object, so ignore hidden states for our
            // subtree text under element traversals too.
            //
            // https://w3c.github.io/accname/#comp_labelledby
            // "The result of LabelledBy Recursion in combination with Hidden Not Referenced means that user
            // agents MUST include all nodes in the subtree as part of the accessible name or accessible
            // description, when the node referenced by aria-labelledby or aria-describedby is hidden."
            mode.considerHiddenState = false;
        } else if (style && style->display() == DisplayType::None) {
            // Unlike visibility:visible + visiblity:visible where the latter can override the former in a subtree,
            // display:none guarantees nothing within will be rendered, so we can exit early.
            return { };
        }
    }

    StringBuilder builder;
    RefPtr<AccessibilityObject> previous;
    bool previousRequiresSpace = false;
    auto appendTextUnderElement = [&] (auto& object) {
        // We don't want to trim whitespace in these intermediate calls to textUnderElement, as doing so will wipe out
        // spaces we need to build the string properly. If anything (depending on the original `mode`), we will trim
        // whitespace at the very end.
        SetForScope resetModeTrim(mode.trimWhitespace, TrimWhitespace::No);

        auto childText = object.textUnderElement(mode);
        if (childText.length()) {
            appendNameToStringBuilder(builder, WTFMove(childText), previousRequiresSpace || shouldPrependSpace(object, previous.get()));
            previousRequiresSpace = false;
        }
    };

    auto childIterator = AXChildIterator(*this);
    for (auto child = childIterator.begin(); child != childIterator.end(); previous = child.ptr(), ++child) {
        if (mode.ignoredChildNode && child->node() == mode.ignoredChildNode)
            continue;

        if (mode.isHidden()) {
            // If we are within a hidden context, don't add any text for this node. Instead, fan out downwards
            // to search for un-hidden nodes (e.g. visibility:visible nodes within a visibility:hidden ancestor).
            appendTextUnderElement(*child);
            continue;
        }

        bool shouldDeriveNameFromAuthor = (mode.childrenInclusion == TextUnderElementMode::Children::IncludeNameFromContentsChildren && !child->accessibleNameDerivesFromContent());
        if (shouldDeriveNameFromAuthor) {
            auto nameForNode = accessibleNameForNode(*child->node());
            bool nameIsEmpty = nameForNode.isEmpty();
            appendNameToStringBuilder(builder, WTFMove(nameForNode));
            // Separate author-provided text with a space.
            previousRequiresSpace = previousRequiresSpace || !nameIsEmpty;
            continue;
        }

        if (!shouldUseAccessibilityObjectInnerText(*child, mode))
            continue;

        if (auto* accessibilityNodeObject = dynamicDowncast<AccessibilityNodeObject>(*child)) {
            // We should ignore the child if it's labeled by this node.
            // This could happen when this node labels multiple child nodes and we didn't
            // skip in the above ignoredChildNode check.
            auto labeledByElements = accessibilityNodeObject->ariaLabeledByElements();
            if (labeledByElements.containsIf([&](auto& element) { return element.ptr() == node; }))
                continue;

            Vector<AccessibilityText> textOrder;
            accessibilityNodeObject->alternativeText(textOrder);
            if (textOrder.size() > 0 && textOrder[0].text.length()) {
                appendNameToStringBuilder(builder, WTFMove(textOrder[0].text));
                // Alternative text (e.g. from aria-label, aria-labelledby, alt, etc) requires space separation.
                previousRequiresSpace = true;
                continue;
            }
        }

        appendTextUnderElement(*child);
    }

    auto result = builder.toString();
    return mode.trimWhitespace == TrimWhitespace::Yes
        ? result.trim(isASCIIWhitespace).simplifyWhiteSpace(isHTMLSpaceButNotLineBreak)
        : result;
}

String AccessibilityNodeObject::title() const
{
    WeakPtr node = this->node();
    if (!node)
        return { };

    if (RefPtr input = dynamicDowncast<HTMLInputElement>(*node); input && input->isTextButton())
        return input->valueWithDefault();

    if (isLabelable()) {
        auto labels = Accessibility::labelsForElement(element());
        // Use the label text as the title if there's no ARIA override.
        if (!labels.isEmpty() && !ariaAccessibilityDescription().length())
            return textForLabelElements(WTFMove(labels));
    }

    // For <select> elements, title should be empty if they are not rendered or have role PopUpButton.
    if (node && node->hasTagName(selectTag)
        && (!isAccessibilityRenderObject() || roleValue() == AccessibilityRole::PopUpButton))
        return { };

    switch (roleValue()) {
    case AccessibilityRole::Button:
    case AccessibilityRole::Checkbox:
    case AccessibilityRole::ListBoxOption:
    case AccessibilityRole::ListItem:
    case AccessibilityRole::MenuItem:
    case AccessibilityRole::MenuItemCheckbox:
    case AccessibilityRole::MenuItemRadio:
    case AccessibilityRole::PopUpButton:
    case AccessibilityRole::RadioButton:
    case AccessibilityRole::Switch:
    case AccessibilityRole::Tab:
    case AccessibilityRole::ToggleButton:
        return textUnderElement();
    // SVGRoots should not use the text under itself as a title. That could include the text of objects like <text>.
    case AccessibilityRole::SVGRoot:
        return String();
    default:
        break;
    }

    if (isLink())
        return textUnderElement();
    if (isHeading())
        return textUnderElement({ TextUnderElementMode::Children::SkipIgnoredChildren, true });

    return { };
}

String AccessibilityNodeObject::text() const
{
    if (isSecureField())
        return secureFieldValue();

    // Static text can be either an element with role="text", aka ARIA static text, or inline rendered text.
    // In the former case, prefer any alt text that may have been specified.
    // If no alt text is present, fallback to the inline static text case where textUnderElement is used.
    if (isARIAStaticText()) {
        Vector<AccessibilityText> textOrder;
        alternativeText(textOrder);
        if (textOrder.size() > 0 && textOrder[0].text.length())
            return textOrder[0].text;
    }

    if (roleValue() == AccessibilityRole::StaticText)
        return textUnderElement();

    if (!isTextControl())
        return { };

    RefPtr element = dynamicDowncast<Element>(node());
    if (RefPtr formControl = dynamicDowncast<HTMLTextFormControlElement>(element); formControl && isNativeTextControl())
        return formControl->value();
    return element ? element->innerText() : String();
}

String AccessibilityNodeObject::stringValue() const
{
    Node* node = this->node();
    if (!node)
        return { };

    if (isARIAStaticText()) {
        String staticText = text();
        if (!staticText.length())
            staticText = textUnderElement();
        return staticText;
    }

    if (node->isTextNode())
        return textUnderElement();

    if (RefPtr selectElement = dynamicDowncast<HTMLSelectElement>(*node)) {
        int selectedIndex = selectElement->selectedIndex();
        auto& listItems = selectElement->listItems();
        if (selectedIndex >= 0 && static_cast<size_t>(selectedIndex) < listItems.size()) {
            if (RefPtr selectedItem = listItems[selectedIndex].get()) {
                auto overriddenDescription = selectedItem->attributeTrimmedWithDefaultARIA(aria_labelAttr);
                if (!overriddenDescription.isEmpty())
                    return overriddenDescription;
            }
        }
        if (!selectElement->multiple())
            return selectElement->value();
        return { };
    }

    if (isComboBox()) {
        for (const auto& child : const_cast<AccessibilityNodeObject*>(this)->unignoredChildren()) {
            if (!child->isListBox())
                continue;

            if (auto selectedChildren = child->selectedChildren(); selectedChildren.size())
                return selectedChildren.first()->stringValue();
            break;
        }
    }

    if (isTextControl())
        return text();

    // FIXME: We might need to implement a value here for more types
    // FIXME: It would be better not to advertise a value at all for the types for which we don't implement one;
    // this would require subclassing or making accessibilityAttributeNames do something other than return a
    // single static array.
    return { };
}

WallTime AccessibilityNodeObject::dateTimeValue() const
{
    if (!isDateTime())
        return { };

    auto* input = dynamicDowncast<HTMLInputElement>(node());
    return input ? input->accessibilityValueAsDate() : WallTime();
}

DateComponentsType AccessibilityObject::dateTimeComponentsType() const
{
    if (!isDateTime())
        return DateComponentsType::Invalid;

    auto* input = dynamicDowncast<HTMLInputElement>(node());
    return input ? input->dateType() : DateComponentsType::Invalid;
}

SRGBA<uint8_t> AccessibilityNodeObject::colorValue() const
{
    if (!isColorWell())
        return Color::black;

    RefPtr input = dynamicDowncast<HTMLInputElement>(node());
    if (!input)
        return Color::black;

    return input->valueAsColor().toColorTypeLossy<SRGBA<uint8_t>>();
}

// This function implements the ARIA accessible name as described by the Mozilla
// ARIA Implementer's Guide.
static String accessibleNameForNode(Node& node, Node* labelledbyNode)
{
    auto* element = dynamicDowncast<Element>(node);

    auto ariaLabel = element ? element->attributeTrimmedWithDefaultARIA(aria_labelAttr) : nullAtom();
    if (!ariaLabel.isEmpty())
        return ariaLabel;

    const AtomString& alt = element ? element->attributeWithoutSynchronization(altAttr) : nullAtom();
    if (!alt.isEmpty())
        return alt;

    // If the node can be turned into an AX object, we can use standard name computation rules.
    // If however, the node cannot (because there's no renderer e.g.) fallback to using the basic text underneath.
    auto* cache = node.document().axObjectCache();
    RefPtr axObject = cache ? cache->getOrCreate(node) : nullptr;
    if (axObject) {
        String valueDescription = axObject->valueDescription();
        if (!valueDescription.isEmpty())
            return valueDescription;

        // The Accname specification states that if the name is being calculated for a combobox
        // or listbox inside a labeling element, return the text alternative of the chosen option.
        AXCoreObject::AccessibilityChildrenVector selectedChildren;
        if (axObject->isListBox())
            selectedChildren = axObject->selectedChildren();
        else if (axObject->isComboBox()) {
            for (const auto& child : axObject->unignoredChildren()) {
                if (child->isListBox()) {
                    selectedChildren = child->selectedChildren();
                    break;
                }
            }
        }

        StringBuilder builder;
        for (const auto& child : selectedChildren)
            appendNameToStringBuilder(builder, accessibleNameForNode(*child->node()));

        String childText = builder.toString();
        if (!childText.isEmpty())
            return childText;
    }

    if (auto* input = dynamicDowncast<HTMLInputElement>(element)) {
        String inputValue = input->value();
        if (input->isPasswordField()) {
            StringBuilder passwordValue;
            passwordValue.reserveCapacity(inputValue.length());
            for (size_t i = 0; i < inputValue.length(); i++)
                passwordValue.append(String::fromUTF8("•"));
            return passwordValue.toString();
        }
        return inputValue;
    }
    if (auto* option = dynamicDowncast<HTMLOptionElement>(element))
        return option->value();

    String text;
    if (axObject) {
        if (axObject->accessibleNameDerivesFromContent())
            text = axObject->textUnderElement({ TextUnderElementMode::Children::IncludeNameFromContentsChildren, true, true, false, TrimWhitespace::Yes, labelledbyNode });
    } else
        text = (element ? element->innerText() : node.textContent()).simplifyWhiteSpace(isASCIIWhitespace);

    if (!text.isEmpty())
        return text;

    const AtomString& title = element ? element->attributeWithoutSynchronization(titleAttr) : nullAtom();
    if (!title.isEmpty())
        return title;

    auto* slotElement = dynamicDowncast<HTMLSlotElement>(node);
    // Compute the accessible name for a slot's contents only if it's being used to label another node.
    if (auto* assignedNodes = (slotElement && labelledbyNode) ? slotElement->assignedNodes() : nullptr) {
        StringBuilder builder;
        for (const auto& assignedNode : *assignedNodes)
            appendNameToStringBuilder(builder, accessibleNameForNode(*assignedNode));

        auto assignedNodesText = builder.toString();
        if (!assignedNodesText.isEmpty())
            return assignedNodesText;
    }

    return { };
}

String AccessibilityNodeObject::accessibilityDescriptionForChildren() const
{
    Node* node = this->node();
    if (!node)
        return String();

    AXObjectCache* cache = axObjectCache();
    if (!cache)
        return String();

    StringBuilder builder;
    for (Node* child = node->firstChild(); child; child = child->nextSibling()) {
        if (!is<Element>(child))
            continue;

        if (AccessibilityObject* axObject = cache->getOrCreate(*child)) {
            String description = axObject->ariaLabeledByAttribute();
            if (description.isEmpty())
                description = accessibleNameForNode(*child);
            appendNameToStringBuilder(builder, WTFMove(description));
        }
    }

    return builder.toString();
}

String AccessibilityNodeObject::descriptionForElements(const Vector<Ref<Element>>& elements) const
{
    StringBuilder builder;
    for (auto& element : elements)
        appendNameToStringBuilder(builder, accessibleNameForNode(element.get(), node()));
    return builder.toString();
}

String AccessibilityNodeObject::ariaDescribedByAttribute() const
{
    return descriptionForElements(elementsFromAttribute(aria_describedbyAttr));
}

Vector<Ref<Element>> AccessibilityNodeObject::ariaLabeledByElements() const
{
    // FIXME: should walk the DOM elements only once.
    auto elements = elementsFromAttribute(aria_labelledbyAttr);
    if (elements.size())
        return elements;
    return elementsFromAttribute(aria_labeledbyAttr);
}


String AccessibilityNodeObject::ariaLabeledByAttribute() const
{
    return descriptionForElements(ariaLabeledByElements());
}

bool AccessibilityNodeObject::hasAccNameAttribute() const
{
    auto* element = this->element();
    return element && WebCore::hasAccNameAttribute(*element);
}

bool AccessibilityNodeObject::hasAttributesRequiredForInclusion() const
{
    RefPtr element = this->element();
    if (!element)
        return false;

    if (WebCore::hasAccNameAttribute(*element))
        return true;

#if ENABLE(MATHML)
    if (element->attributeWithoutSynchronization(MathMLNames::alttextAttr).length())
        return true;
#endif

    if (element->attributeWithoutSynchronization(altAttr).length() || UNLIKELY(element->attributeWithoutSynchronization(aria_helpAttr).length()))
        return true;

    return false;
}

bool AccessibilityNodeObject::isFocused() const
{
    if (!m_node)
        return false;

    auto& document = node()->document();
    auto* focusedElement = document.focusedElement();
    if (!focusedElement)
        return false;

    if (focusedElement == node())
        return true;

    // A web area is represented by the Document node in the DOM tree which isn't focusable.
    // Instead, check if the frame's selection is focused.
    if (roleValue() != AccessibilityRole::WebArea)
        return false;

    auto* frame = document.frame();
    return frame ? frame->selection().isFocusedAndActive() : false;
}

void AccessibilityNodeObject::setFocused(bool on)
{
    // Call the base class setFocused to ensure the view is focused and active.
    AccessibilityObject::setFocused(on);

    if (!canSetFocusAttribute())
        return;

    auto* document = this->document();

    // This is needed or else focus won't always go into iframes with different origins.
    UserGestureIndicator gestureIndicator(IsProcessingUserGesture::Yes, document);

    // Handle clearing focus.
    if (!on || !is<Element>(node())) {
        document->setFocusedElement(nullptr);
        return;
    }

    // When a node is told to set focus, that can cause it to be deallocated, which means that doing
    // anything else inside this object will crash. To fix this, we added a RefPtr to protect this object
    // long enough for duration.
    RefPtr<AccessibilityObject> protectedThis(this);

    // If this node is already the currently focused node, then calling focus() won't do anything.
    // That is a problem when focus is removed from the webpage to chrome, and then returns.
    // In these cases, we need to do what keyboard and mouse focus do, which is reset focus first.
    if (document->focusedElement() == node())
        document->setFocusedElement(nullptr);

    // If we return from setFocusedElement and our element has been removed from a tree, axObjectCache() may be null.
    if (auto* cache = axObjectCache()) {
        cache->setIsSynchronizingSelection(true);
        downcast<Element>(*m_node).focus();
        cache->setIsSynchronizingSelection(false);
    }
}

bool AccessibilityNodeObject::canSetFocusAttribute() const
{
    Node* node = this->node();
    if (!node)
        return false;

    if (isWebArea())
        return true;

    // NOTE: It would be more accurate to ask the document whether setFocusedElement() would
    // do anything. For example, setFocusedElement() will do nothing if the current focused
    // node will not relinquish the focus.
    RefPtr element = dynamicDowncast<Element>(*node);
    return element && !element->isDisabledFormControl() && element->supportsFocus();
}

bool AccessibilityNodeObject::canSetValueAttribute() const
{
    Node* node = this->node();
    if (!node)
        return false;

    // The host-language readonly attribute trumps aria-readonly.
    if (RefPtr textarea = dynamicDowncast<HTMLTextAreaElement>(*node))
        return !textarea->isReadOnly();
    if (RefPtr input = dynamicDowncast<HTMLInputElement>(*node); input && input->isTextField())
        return !input->isReadOnly();

    String readOnly = readOnlyValue();
    if (!readOnly.isEmpty())
        return readOnly == "true"_s ? false : true;

    if (isNonNativeTextControl())
        return true;

    if (isMeter())
        return false;

    if (isProgressIndicator() || isSlider() || isScrollbar())
        return true;

#if USE(ATSPI)
    // In ATSPI, input types which support aria-readonly are treated as having a
    // settable value if the user can modify the widget's value or its state.
    if (supportsReadOnly())
        return true;

    if (isRadioButton()) {
        auto radioGroup = radioGroupAncestor();
        return radioGroup ? radioGroup->readOnlyValue() != "true"_s : true;
    }
#endif

    if (isWebArea()) {
        Document* document = this->document();
        if (!document)
            return false;

        if (HTMLElement* body = document->bodyOrFrameset()) {
            if (body->hasEditableStyle())
                return true;
        }

        return document->hasEditableStyle();
    }

    return node->hasEditableStyle();
}

AccessibilityRole AccessibilityNodeObject::determineAriaRoleAttribute() const
{
    const AtomString& ariaRole = getAttribute(roleAttr);
    if (ariaRole.isNull() || ariaRole.isEmpty())
        return AccessibilityRole::Unknown;

    AccessibilityRole role = ariaRoleToWebCoreRole(ariaRole);

    // ARIA states if an item can get focus, it should not be presentational.
    if (role == AccessibilityRole::Presentational && canSetFocusAttribute())
        return AccessibilityRole::Unknown;

    if (role == AccessibilityRole::Button)
        role = buttonRoleType();

    // If ariaRoleToWebCoreRole computed AccessibilityRole::TextField, we need to figure out if we should use the single-line WebCore textbox role (AccessibilityRole::TextField)
    // or the multi-line WebCore textbox role (AccessibilityRole::TextArea) because the "textbox" ARIA role is overloaded and can mean either.
    if (role == AccessibilityRole::TextField) {
        auto ariaMultiline = getAttribute(aria_multilineAttr);
        if (equalLettersIgnoringASCIICase(ariaMultiline, "true"_s) || (!equalLettersIgnoringASCIICase(ariaMultiline, "false"_s) && matchesTextAreaRole()))
            role = AccessibilityRole::TextArea;
    }

    role = remapAriaRoleDueToParent(role);

    // Presentational roles are invalidated by the presence of ARIA attributes.
    if (role == AccessibilityRole::Presentational && supportsARIAAttributes())
        role = AccessibilityRole::Unknown;

    // https://w3c.github.io/aria/#document-handling_author-errors_roles
    // In situations where an author has not specified names for the form and
    // region landmarks, it is considered an authoring error. The user agent
    // MUST treat such element as if no role had been provided.
    if ((role == AccessibilityRole::LandmarkRegion || role == AccessibilityRole::Form) && !hasAccNameAttribute()) {
        // If a region has no label, but it does have a fallback role, use that instead.
        auto nextRole = ariaRoleToWebCoreRole(ariaRole, [] (const AccessibilityRole& skipRole) {
            return skipRole == AccessibilityRole::LandmarkRegion;
        });
        if (nextRole != role)
            role = nextRole;
        else
            role = AccessibilityRole::Unknown;
    }
    if (enumToUnderlyingType(role))
        return role;

    return AccessibilityRole::Unknown;
}

AccessibilityRole AccessibilityNodeObject::remapAriaRoleDueToParent(AccessibilityRole role) const
{
    // Some objects change their role based on their parent.
    // However, asking for the unignoredParent calls isIgnored(), which can trigger a loop.
    // While inside the call stack of creating an element, we need to avoid isIgnored().
    // https://bugs.webkit.org/show_bug.cgi?id=65174

    if (role != AccessibilityRole::ListBoxOption && role != AccessibilityRole::MenuItem)
        return role;

    for (AccessibilityObject* parent = parentObject(); parent && !parent->isIgnored(); parent = parent->parentObject()) {
        AccessibilityRole parentAriaRole = parent->ariaRoleAttribute();

        // Selects and listboxes both have options as child roles, but they map to different roles within WebCore.
        if (role == AccessibilityRole::ListBoxOption && parentAriaRole == AccessibilityRole::Menu)
            return AccessibilityRole::MenuItem;

        // If the parent had a different role, then we don't need to continue searching up the chain.
        if (parentAriaRole != AccessibilityRole::Unknown)
            break;
    }

    return role;
}

bool AccessibilityNodeObject::canSetSelectedAttribute() const
{
    // Elements that can be selected
    switch (roleValue()) {
    case AccessibilityRole::Cell:
    case AccessibilityRole::GridCell:
    case AccessibilityRole::RowHeader:
    case AccessibilityRole::Row:
    case AccessibilityRole::TabList:
    case AccessibilityRole::Tab:
    case AccessibilityRole::TreeGrid:
    case AccessibilityRole::TreeItem:
    case AccessibilityRole::Tree:
    case AccessibilityRole::MenuItemCheckbox:
    case AccessibilityRole::MenuItemRadio:
    case AccessibilityRole::MenuItem:
        return isEnabled();
    default:
        return false;
    }
}

namespace Accessibility {

RefPtr<HTMLElement> controlForLabelElement(const HTMLLabelElement& label)
{
    auto control = label.control();
    // Make sure the corresponding control isn't a descendant of this label that's in the middle of being destroyed.
    if (!control || (control->renderer() && !control->renderer()->parent()))
        return nullptr;
    return control;
}

Vector<Ref<HTMLElement>> labelsForElement(Element* element)
{
    RefPtr htmlElement = dynamicDowncast<HTMLElement>(element);
    if (!htmlElement || !htmlElement->isLabelable())
        return { };

    Vector<Ref<HTMLElement>> result;
    const auto& idAttribute = htmlElement->getIdAttribute();
    if (!idAttribute.isEmpty()) {
        if (htmlElement->hasAttributeWithoutSynchronization(aria_labelAttr))
            return { };

        if (auto* treeScopeLabels = htmlElement->treeScope().labelElementsForId(idAttribute); treeScopeLabels && !treeScopeLabels->isEmpty()) {
            result.appendVector(WTF::compactMap(*treeScopeLabels, [] (auto& label) {
                return RefPtr { dynamicDowncast<HTMLLabelElement>(label.get()) };
            }));
            if (result.size())
                return result;
        }
    }

    if (htmlElement->hasAttributeWithoutSynchronization(aria_labelAttr))
        return { };

    if (RefPtr nearestLabel = ancestorsOfType<HTMLLabelElement>(*htmlElement).first()) {
        // Only use the nearest label if it isn't pointing at something else.
        const auto& forAttribute = nearestLabel->attributeWithoutSynchronization(forAttr);
        if (forAttribute.isEmpty() || forAttribute == idAttribute)
            return { nearestLabel.releaseNonNull() };
    }
    return { };
}

} // namespace Accessibility

} // namespace WebCore