third_party/WebKit/Source/modules/accessibility/AXLayoutObject.cpp

/*
* Copyright (C) 2008 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1.  Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
* 2.  Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in the
*     documentation and/or other materials provided with the distribution.
* 3.  Neither the name of Apple Computer, 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;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#include "modules/accessibility/AXLayoutObject.h"

#include "bindings/core/v8/ExceptionStatePlaceholder.h"
#include "core/CSSPropertyNames.h"
#include "core/InputTypeNames.h"
#include "core/dom/ElementTraversal.h"
#include "core/dom/Range.h"
#include "core/dom/shadow/ShadowRoot.h"
#include "core/editing/EditingUtilities.h"
#include "core/editing/FrameSelection.h"
#include "core/editing/RenderedPosition.h"
#include "core/editing/TextAffinity.h"
#include "core/editing/VisibleUnits.h"
#include "core/editing/iterators/CharacterIterator.h"
#include "core/editing/iterators/TextIterator.h"
#include "core/frame/FrameOwner.h"
#include "core/frame/FrameView.h"
#include "core/frame/LocalFrame.h"
#include "core/frame/Settings.h"
#include "core/html/HTMLFrameOwnerElement.h"
#include "core/html/HTMLImageElement.h"
#include "core/html/HTMLInputElement.h"
#include "core/html/HTMLLabelElement.h"
#include "core/html/HTMLOptionElement.h"
#include "core/html/HTMLSelectElement.h"
#include "core/html/HTMLTextAreaElement.h"
#include "core/html/LabelsNodeList.h"
#include "core/html/shadow/ShadowElementNames.h"
#include "core/layout/HitTestResult.h"
#include "core/layout/LayoutFileUploadControl.h"
#include "core/layout/LayoutHTMLCanvas.h"
#include "core/layout/LayoutImage.h"
#include "core/layout/LayoutInline.h"
#include "core/layout/LayoutListMarker.h"
#include "core/layout/LayoutMenuList.h"
#include "core/layout/LayoutTextControl.h"
#include "core/layout/LayoutView.h"
#include "core/layout/api/LayoutAPIShim.h"
#include "core/layout/api/LineLayoutAPIShim.h"
#include "core/loader/ProgressTracker.h"
#include "core/page/Page.h"
#include "core/paint/PaintLayer.h"
#include "core/style/ComputedStyleConstants.h"
#include "core/svg/SVGDocumentExtensions.h"
#include "core/svg/SVGSVGElement.h"
#include "core/svg/graphics/SVGImage.h"
#include "modules/accessibility/AXImageMapLink.h"
#include "modules/accessibility/AXInlineTextBox.h"
#include "modules/accessibility/AXObjectCacheImpl.h"
#include "modules/accessibility/AXSVGRoot.h"
#include "modules/accessibility/AXSpinButton.h"
#include "modules/accessibility/AXTable.h"
#include "platform/fonts/FontTraits.h"
#include "platform/geometry/TransformState.h"
#include "platform/text/PlatformLocale.h"
#include "platform/text/TextDirection.h"
#include "wtf/StdLibExtras.h"

using blink::WebLocalizedString;

namespace blink {

using namespace HTMLNames;

static inline LayoutObject* firstChildInContinuation(const LayoutInline& layoutObject)
{
    LayoutBoxModelObject* r = layoutObject.continuation();

    while (r) {
        if (r->isLayoutBlock())
            return r;
        if (LayoutObject* child = r->slowFirstChild())
            return child;
        r = toLayoutInline(r)->continuation();
    }

    return 0;
}

static inline bool isInlineWithContinuation(LayoutObject* object)
{
    if (!object->isBoxModelObject())
        return false;

    LayoutBoxModelObject* layoutObject = toLayoutBoxModelObject(object);
    if (!layoutObject->isLayoutInline())
        return false;

    return toLayoutInline(layoutObject)->continuation();
}

static inline LayoutObject* firstChildConsideringContinuation(LayoutObject* layoutObject)
{
    LayoutObject* firstChild = layoutObject->slowFirstChild();

    if (!firstChild && isInlineWithContinuation(layoutObject))
        firstChild = firstChildInContinuation(toLayoutInline(*layoutObject));

    return firstChild;
}

static inline LayoutInline* startOfContinuations(LayoutObject* r)
{
    if (r->isInlineElementContinuation()) {
        return toLayoutInline(r->node()->layoutObject());
    }

    // Blocks with a previous continuation always have a next continuation
    if (r->isLayoutBlockFlow() && toLayoutBlockFlow(r)->inlineElementContinuation())
        return toLayoutInline(toLayoutBlockFlow(r)->inlineElementContinuation()->node()->layoutObject());

    return 0;
}

static inline LayoutObject* endOfContinuations(LayoutObject* layoutObject)
{
    LayoutObject* prev = layoutObject;
    LayoutObject* cur = layoutObject;

    if (!cur->isLayoutInline() && !cur->isLayoutBlockFlow())
        return layoutObject;

    while (cur) {
        prev = cur;
        if (cur->isLayoutInline()) {
            cur = toLayoutInline(cur)->inlineElementContinuation();
            ASSERT(cur || !toLayoutInline(prev)->continuation());
        } else {
            cur = toLayoutBlockFlow(cur)->inlineElementContinuation();
        }
    }

    return prev;
}

static inline bool lastChildHasContinuation(LayoutObject* layoutObject)
{
    LayoutObject* lastChild = layoutObject->slowLastChild();
    return lastChild && isInlineWithContinuation(lastChild);
}

static LayoutBoxModelObject* nextContinuation(LayoutObject* layoutObject)
{
    ASSERT(layoutObject);
    if (layoutObject->isLayoutInline() && !layoutObject->isAtomicInlineLevel())
        return toLayoutInline(layoutObject)->continuation();
    if (layoutObject->isLayoutBlockFlow())
        return toLayoutBlockFlow(layoutObject)->inlineElementContinuation();
    return 0;
}

AXLayoutObject::AXLayoutObject(LayoutObject* layoutObject, AXObjectCacheImpl& axObjectCache)
    : AXNodeObject(layoutObject->node(), axObjectCache)
    , m_layoutObject(layoutObject)
    , m_cachedElementRectDirty(true)
{
#if ENABLE(ASSERT)
    m_layoutObject->setHasAXObject(true);
#endif
}

AXLayoutObject* AXLayoutObject::create(LayoutObject* layoutObject, AXObjectCacheImpl& axObjectCache)
{
    return new AXLayoutObject(layoutObject, axObjectCache);
}

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

LayoutRect AXLayoutObject::elementRect() const
{
    if (!m_explicitElementRect.isEmpty()) {
        LayoutRect bounds = m_explicitElementRect;
        AXObject* canvas = axObjectCache().objectFromAXID(m_explicitContainerID);
        if (canvas)
            bounds.moveBy(canvas->elementRect().location());
        return bounds;
    }

    // FIXME(dmazzoni): use relative bounds instead since this is a bottleneck.
    // http://crbug.com/618120
    return computeElementRect();
}

SkMatrix44 AXLayoutObject::transformFromLocalParentFrame() const
{
    if (!m_layoutObject)
        return SkMatrix44();
    LayoutView* layoutView = toLayoutView(LayoutAPIShim::layoutObjectFrom(documentFrameView()->layoutViewItem()));

    FrameView* parentFrameView = documentFrameView()->parentFrameView();
    if (!parentFrameView)
        return SkMatrix44();
    LayoutView* parentLayoutView = toLayoutView(LayoutAPIShim::layoutObjectFrom(parentFrameView->layoutViewItem()));

    TransformationMatrix accumulatedTransform = layoutView->localToAncestorTransform(parentLayoutView, TraverseDocumentBoundaries);
    IntPoint scrollPosition = documentFrameView()->scrollPosition();
    accumulatedTransform.translate(scrollPosition.x(), scrollPosition.y());
    return TransformationMatrix::toSkMatrix44(accumulatedTransform);
}

LayoutBoxModelObject* AXLayoutObject::getLayoutBoxModelObject() const
{
    if (!m_layoutObject || !m_layoutObject->isBoxModelObject())
        return 0;
    return toLayoutBoxModelObject(m_layoutObject);
}

ScrollableArea* AXLayoutObject::getScrollableAreaIfScrollable() const
{
    if (isWebArea())
        return documentFrameView();

    if (!m_layoutObject || !m_layoutObject->isBox())
        return 0;

    LayoutBox* box = toLayoutBox(m_layoutObject);
    if (!box->canBeScrolledAndHasScrollableArea())
        return 0;

    return box->getScrollableArea();
}

void AXLayoutObject::getRelativeBounds(AXObject** outContainer, FloatRect& outBoundsInContainer, SkMatrix44& outContainerTransform) const
{
    *outContainer = nullptr;
    outBoundsInContainer = FloatRect();
    outContainerTransform.setIdentity();

    // First check if it has explicit bounds, for example if this element is tied to a
    // canvas path. When explicit coordinates are provided, the ID of the explicit container
    // element that the coordinates are relative to must be provided too.
    if (!m_explicitElementRect.isEmpty()) {
        *outContainer = axObjectCache().objectFromAXID(m_explicitContainerID);
        if (*outContainer) {
            outBoundsInContainer = FloatRect(m_explicitElementRect);
            return;
        }
    }

    if (!m_layoutObject)
        return;

    if (isWebArea()) {
        if (m_layoutObject->frame()->view())
            outBoundsInContainer.setSize(FloatSize(m_layoutObject->frame()->view()->contentsSize()));
        return;
    }

    // First compute the container. The container must be an ancestor in the accessibility tree, and
    // its LayoutObject must be an ancestor in the layout tree. Get the first such ancestor that's
    // either scrollable or has a paint layer.
    AXObject* container = parentObjectUnignored();
    LayoutObject* containerLayoutObject = nullptr;
    while (container) {
        containerLayoutObject = container->getLayoutObject();
        if (containerLayoutObject && containerLayoutObject->isBoxModelObject() && m_layoutObject->isDescendantOf(containerLayoutObject)) {
            if (container->isScrollableContainer() || containerLayoutObject->hasLayer())
                break;
        }

        container = container->parentObjectUnignored();
    }

    if (!container)
        return;
    *outContainer = container;

    // Next get the local bounds of this LayoutObject, which is typically
    // a rect at point (0, 0) with the width and height of the LayoutObject.
    LayoutRect localBounds;
    if (m_layoutObject->isText()) {
        Vector<FloatQuad> quads;
        toLayoutText(m_layoutObject)->quads(quads, LayoutText::ClipToEllipsis, LayoutText::LocalQuads);
        for (const FloatQuad& quad : quads)
            localBounds.unite(LayoutRect(quad.boundingBox()));
    } else if (m_layoutObject->isLayoutInline()) {
        Vector<LayoutRect> rects;
        toLayoutInline(m_layoutObject)->addOutlineRects(rects, LayoutPoint(), LayoutObject::IncludeBlockVisualOverflow);
        localBounds = unionRect(rects);
    } else if (m_layoutObject->isBox()) {
        localBounds = LayoutRect(LayoutPoint(), toLayoutBox(m_layoutObject)->size());
    } else if (m_layoutObject->isSVG()) {
        localBounds = LayoutRect(m_layoutObject->strokeBoundingBox());
    } else {
        DCHECK(false);
    }
    outBoundsInContainer = FloatRect(localBounds);

    // If the container has a scroll offset, subtract that out because we want our
    // bounds to be relative to the *unscrolled* position of the container object.
    ScrollableArea* scrollableArea = container->getScrollableAreaIfScrollable();
    if (scrollableArea && !container->isWebArea()) {
        IntPoint scrollPosition = scrollableArea->scrollPosition();
        outBoundsInContainer.move(FloatSize(scrollPosition.x(), scrollPosition.y()));
    }

    // Compute the transform between the container's coordinate space and this object.
    // If the transform is just a simple translation, apply that to the bounding box, but
    // if it's a non-trivial transformation like a rotation, scaling, etc. then return
    // the full matrix instead.
    TransformationMatrix transform = m_layoutObject->localToAncestorTransform(toLayoutBoxModelObject(containerLayoutObject));
    if (transform.isIdentityOr2DTranslation()) {
        outBoundsInContainer.move(transform.to2DTranslation());
    } else {
        outContainerTransform = TransformationMatrix::toSkMatrix44(transform);
    }
}

static bool isImageOrAltText(LayoutBoxModelObject* box, Node* node)
{
    if (box && box->isImage())
        return true;
    if (isHTMLImageElement(node))
        return true;
    if (isHTMLInputElement(node) && toHTMLInputElement(node)->hasFallbackContent())
        return true;
    return false;
}

AccessibilityRole AXLayoutObject::nativeAccessibilityRoleIgnoringAria() const
{
    Node* node = m_layoutObject->node();
    LayoutBoxModelObject* cssBox = getLayoutBoxModelObject();

    if ((cssBox && cssBox->isListItem()) || isHTMLLIElement(node))
        return ListItemRole;
    if (m_layoutObject->isListMarker())
        return ListMarkerRole;
    if (m_layoutObject->isBR())
        return LineBreakRole;
    if (m_layoutObject->isText())
        return StaticTextRole;
    if (cssBox && isImageOrAltText(cssBox, node)) {
        if (node && node->isLink())
            return ImageMapRole;
        if (isHTMLInputElement(node))
            return ariaHasPopup() ? PopUpButtonRole : ButtonRole;
        if (isSVGImage())
            return SVGRootRole;
        return ImageRole;
    }
    // Note: if JavaScript is disabled, the layoutObject won't be a LayoutHTMLCanvas.
    if (isHTMLCanvasElement(node) && m_layoutObject->isCanvas())
        return CanvasRole;

    if (cssBox && cssBox->isLayoutView())
        return WebAreaRole;

    if (m_layoutObject->isSVGImage())
        return ImageRole;
    if (m_layoutObject->isSVGRoot())
        return SVGRootRole;

    // Table sections should be ignored.
    if (m_layoutObject->isTableSection())
        return IgnoredRole;

    if (m_layoutObject->isHR())
        return SplitterRole;

    return AXNodeObject::nativeAccessibilityRoleIgnoringAria();
}

AccessibilityRole AXLayoutObject::determineAccessibilityRole()
{
    if (!m_layoutObject)
        return UnknownRole;

    if ((m_ariaRole = determineAriaRoleAttribute()) != UnknownRole)
        return m_ariaRole;

    AccessibilityRole role = nativeAccessibilityRoleIgnoringAria();
    if (role != UnknownRole)
        return role;

    if (m_layoutObject->isLayoutBlockFlow())
        return GroupRole;

    // If the element does not have role, but it has ARIA attributes, accessibility should fallback to exposing it as a group.
    if (supportsARIAAttributes())
        return GroupRole;

    return UnknownRole;
}

void AXLayoutObject::init()
{
    AXNodeObject::init();
}

void AXLayoutObject::detach()
{
    AXNodeObject::detach();

    detachRemoteSVGRoot();

#if ENABLE(ASSERT)
    if (m_layoutObject)
        m_layoutObject->setHasAXObject(false);
#endif
    m_layoutObject = 0;
}

//
// Check object role or purpose.
//

static bool isLinkable(const AXObject& object)
{
    if (!object.getLayoutObject())
        return false;

    // See https://wiki.mozilla.org/Accessibility/AT-Windows-API for the elements
    // Mozilla considers linkable.
    return object.isLink() || object.isImage() || object.getLayoutObject()->isText();
}

// Requires layoutObject to be present because it relies on style
// user-modify. Don't move this logic to AXNodeObject.
bool AXLayoutObject::isEditable() const
{
    if (getLayoutObject() && getLayoutObject()->isTextControl())
        return true;

    m_layoutObject->document().updateStyleAndLayoutTree();
    if (getNode() && hasEditableStyle(*getNode()))
        return true;

    if (isWebArea()) {
        Document& document = getLayoutObject()->document();
        HTMLElement* body = document.body();
        if (body && hasEditableStyle(*body))
            return true;

        return hasEditableStyle(document);
    }

    return AXNodeObject::isEditable();
}

// Requires layoutObject to be present because it relies on style
// user-modify. Don't move this logic to AXNodeObject.
bool AXLayoutObject::isRichlyEditable() const
{
    m_layoutObject->document().updateStyleAndLayoutTree();
    if (getNode() && hasRichlyEditableStyle(*getNode()))
        return true;

    if (isWebArea()) {
        Document& document = m_layoutObject->document();
        HTMLElement* body = document.body();
        if (body && hasRichlyEditableStyle(*body))
            return true;

        return hasRichlyEditableStyle(document);
    }

    return AXNodeObject::isRichlyEditable();
}

bool AXLayoutObject::isLinked() const
{
    if (!isLinkable(*this))
        return false;

    Element* anchor = anchorElement();
    if (!isHTMLAnchorElement(anchor))
        return false;

    return !toHTMLAnchorElement(*anchor).href().isEmpty();
}

bool AXLayoutObject::isLoaded() const
{
    return !m_layoutObject->document().parser();
}

bool AXLayoutObject::isOffScreen() const
{
    ASSERT(m_layoutObject);
    IntRect contentRect = pixelSnappedIntRect(m_layoutObject->absoluteClippedOverflowRect());
    FrameView* view = m_layoutObject->frame()->view();
    IntRect viewRect = view->visibleContentRect();
    viewRect.intersect(contentRect);
    return viewRect.isEmpty();
}

bool AXLayoutObject::isReadOnly() const
{
    ASSERT(m_layoutObject);

    if (isWebArea()) {
        Document& document = m_layoutObject->document();
        HTMLElement* body = document.body();
        if (body && hasEditableStyle(*body))
            return false;

        return !hasEditableStyle(document);
    }

    return AXNodeObject::isReadOnly();
}

bool AXLayoutObject::isVisited() const
{
    // FIXME: Is it a privacy violation to expose visited information to accessibility APIs?
    return m_layoutObject->style()->isLink() && m_layoutObject->style()->insideLink() == InsideVisitedLink;
}

//
// Check object state.
//

bool AXLayoutObject::isFocused() const
{
    if (!getDocument())
        return false;

    Element* focusedElement = getDocument()->focusedElement();
    if (!focusedElement)
        return false;
    AXObject* focusedObject = axObjectCache().getOrCreate(focusedElement);
    if (!focusedObject || !focusedObject->isAXLayoutObject())
        return false;

    // A web area is represented by the Document node in the DOM tree, which isn't focusable.
    // Check instead if the frame's selection controller is focused
    if (focusedObject == this
        || (roleValue() == WebAreaRole && getDocument()->frame()->selection().isFocusedAndActive()))
        return true;

    return false;
}

bool AXLayoutObject::isSelected() const
{
    if (!getLayoutObject() || !getNode())
        return false;

    const AtomicString& ariaSelected = getAttribute(aria_selectedAttr);
    if (equalIgnoringCase(ariaSelected, "true"))
        return true;

    AXObject* focusedObject = axObjectCache().focusedObject();
    if (ariaRoleAttribute() == ListBoxOptionRole && focusedObject
        && focusedObject->activeDescendant() == this) {
        return true;
    }

    if (isTabItem() && isTabItemSelected())
        return true;

    return false;
}

//
// Whether objects are ignored, i.e. not included in the tree.
//

AXObjectInclusion AXLayoutObject::defaultObjectInclusion(IgnoredReasons* ignoredReasons) const
{
    // The following cases can apply to any element that's a subclass of AXLayoutObject.

    if (!m_layoutObject) {
        if (ignoredReasons)
            ignoredReasons->append(IgnoredReason(AXNotRendered));
        return IgnoreObject;
    }

    if (m_layoutObject->style()->visibility() != EVisibility::Visible) {
        // aria-hidden is meant to override visibility as the determinant in AX hierarchy inclusion.
        if (equalIgnoringCase(getAttribute(aria_hiddenAttr), "false"))
            return DefaultBehavior;

        if (ignoredReasons)
            ignoredReasons->append(IgnoredReason(AXNotVisible));
        return IgnoreObject;
    }

    return AXObject::defaultObjectInclusion(ignoredReasons);
}

bool AXLayoutObject::computeAccessibilityIsIgnored(IgnoredReasons* ignoredReasons) const
{
#if ENABLE(ASSERT)
    ASSERT(m_initialized);
#endif

    if (!m_layoutObject)
        return true;

    // Check first if any of the common reasons cause this element to be ignored.
    // Then process other use cases that need to be applied to all the various roles
    // that AXLayoutObjects take on.
    AXObjectInclusion decision = defaultObjectInclusion(ignoredReasons);
    if (decision == IncludeObject)
        return false;
    if (decision == IgnoreObject)
        return true;

    // If this element is within a parent that cannot have children, it should not be exposed
    if (isDescendantOfLeafNode()) {
        if (ignoredReasons)
            ignoredReasons->append(IgnoredReason(AXAncestorIsLeafNode, leafNodeAncestor()));
        return true;
    }

    if (roleValue() == IgnoredRole) {
        if (ignoredReasons)
            ignoredReasons->append(IgnoredReason(AXUninteresting));
        return true;
    }

    if (hasInheritedPresentationalRole()) {
        if (ignoredReasons) {
            const AXObject* inheritsFrom = inheritsPresentationalRoleFrom();
            if (inheritsFrom == this)
                ignoredReasons->append(IgnoredReason(AXPresentationalRole));
            else
                ignoredReasons->append(IgnoredReason(AXInheritsPresentation, inheritsFrom));
        }
        return true;
    }

    // An ARIA tree can only have tree items and static text as children.
    if (AXObject* treeAncestor = treeAncestorDisallowingChild()) {
        if (ignoredReasons)
            ignoredReasons->append(IgnoredReason(AXAncestorDisallowsChild, treeAncestor));
        return true;
    }

    // A LayoutPart is an iframe element or embedded object element or something like
    // that. We don't want to ignore those.
    if (m_layoutObject->isLayoutPart())
        return false;

    // Make sure renderers with layers stay in the tree.
    if (getLayoutObject() && getLayoutObject()->hasLayer() && getNode() && getNode()->hasChildren())
        return false;

    // find out if this element is inside of a label element.
    // if so, it may be ignored because it's the label for a checkbox or radio button
    AXObject* controlObject = correspondingControlForLabelElement();
    if (controlObject && controlObject->isCheckboxOrRadio() && controlObject->nameFromLabelElement()) {
        if (ignoredReasons) {
            HTMLLabelElement* label = labelElementContainer();
            if (label && label != getNode()) {
                AXObject* labelAXObject = axObjectCache().getOrCreate(label);
                ignoredReasons->append(IgnoredReason(AXLabelContainer, labelAXObject));
            }

            ignoredReasons->append(IgnoredReason(AXLabelFor, controlObject));
        }
        return true;
    }

    if (m_layoutObject->isBR())
        return false;

    if (m_layoutObject->isText()) {
        // static text beneath MenuItems and MenuButtons are just reported along with the menu item, so it's ignored on an individual level
        AXObject* parent = parentObjectUnignored();
        if (parent && (parent->ariaRoleAttribute() == MenuItemRole || parent->ariaRoleAttribute() == MenuButtonRole)) {
            if (ignoredReasons)
                ignoredReasons->append(IgnoredReason(AXStaticTextUsedAsNameFor, parent));
            return true;
        }
        LayoutText* layoutText = toLayoutText(m_layoutObject);
        if (!layoutText->hasTextBoxes()) {
            if (ignoredReasons)
                ignoredReasons->append(IgnoredReason(AXEmptyText));
            return true;
        }

        // Don't ignore static text in editable text controls.
        for (AXObject* parent = parentObject(); parent; parent = parent->parentObject()) {
            if (parent->roleValue() == TextFieldRole)
                return false;
        }

        // text elements that are just empty whitespace should not be returned
        // FIXME(dmazzoni): we probably shouldn't ignore this if the style is 'pre', or similar...
        if (layoutText->text().impl()->containsOnlyWhitespace()) {
            if (ignoredReasons)
                ignoredReasons->append(IgnoredReason(AXEmptyText));
            return true;
        }
        return false;
    }
    if (isHeading())
        return false;

    if (isLandmarkRelated())
        return false;

    if (isLink())
        return false;

    // all controls are accessible
    if (isControl())
        return false;

    if (ariaRoleAttribute() != UnknownRole)
        return false;

    // don't ignore labels, because they serve as TitleUIElements
    Node* node = m_layoutObject->node();
    if (isHTMLLabelElement(node))
        return false;

    // Anything that is content editable should not be ignored.
    // However, one cannot just call node->hasEditableStyle() since that will ask if its parents
    // are also editable. Only the top level content editable region should be exposed.
    if (hasContentEditableAttributeSet())
        return false;

    if (roleValue() == AbbrRole)
        return false;

    // List items play an important role in defining the structure of lists. They should not be ignored.
    if (roleValue() == ListItemRole)
        return false;

    if (roleValue() == BlockquoteRole)
        return false;

    if (roleValue() == DialogRole)
        return false;

    if (roleValue() == FigcaptionRole)
        return false;

    if (roleValue() == FigureRole)
        return false;

    if (roleValue() == DetailsRole)
        return false;

    if (roleValue() == MarkRole)
        return false;

    if (roleValue() == MathRole)
        return false;

    if (roleValue() == MeterRole)
        return false;

    if (roleValue() == RubyRole)
        return false;

    if (roleValue() == SplitterRole)
        return false;

    if (roleValue() == TimeRole)
        return false;

    // if this element has aria attributes on it, it should not be ignored.
    if (supportsARIAAttributes())
        return false;

    // <span> tags are inline tags and not meant to convey information if they have no other aria
    // information on them. If we don't ignore them, they may emit signals expected to come from
    // their parent. In addition, because included spans are GroupRole objects, and GroupRole
    // objects are often containers with meaningful information, the inclusion of a span can have
    // the side effect of causing the immediate parent accessible to be ignored. This is especially
    // problematic for platforms which have distinct roles for textual block elements.
    if (isHTMLSpanElement(node)) {
        if (ignoredReasons)
            ignoredReasons->append(IgnoredReason(AXUninteresting));
        return true;
    }

    // ignore images seemingly used as spacers
    if (isImage()) {
        // If the image can take focus, it should not be ignored, lest the user not be able to interact with something important.
        if (canSetFocusAttribute())
            return false;

        if (node && node->isElementNode()) {
            Element* elt = toElement(node);
            const AtomicString& alt = elt->getAttribute(altAttr);
            // don't ignore an image that has an alt tag
            if (!alt.getString().containsOnlyWhitespace())
                return false;
            // informal standard is to ignore images with zero-length alt strings
            if (!alt.isNull()) {
                if (ignoredReasons)
                    ignoredReasons->append(IgnoredReason(AXEmptyAlt));
                return true;
            }
        }

        if (isNativeImage() && m_layoutObject->isImage()) {
            // check for one-dimensional image
            LayoutImage* image = toLayoutImage(m_layoutObject);
            if (image->size().height() <= 1 || image->size().width() <= 1) {
                if (ignoredReasons)
                    ignoredReasons->append(IgnoredReason(AXProbablyPresentational));
                return true;
            }

            // check whether laid out image was stretched from one-dimensional file image
            if (image->cachedImage()) {
                LayoutSize imageSize = image->cachedImage()->imageSize(LayoutObject::shouldRespectImageOrientation(m_layoutObject), image->view()->zoomFactor());
                if (imageSize.height() <= 1 || imageSize.width() <= 1) {
                    if (ignoredReasons)
                        ignoredReasons->append(IgnoredReason(AXProbablyPresentational));
                    return true;
                }
                return false;
            }
        }
        return false;
    }

    if (isCanvas()) {
        if (canvasHasFallbackContent())
            return false;
        LayoutHTMLCanvas* canvas = toLayoutHTMLCanvas(m_layoutObject);
        if (canvas->size().height() <= 1 || canvas->size().width() <= 1) {
            if (ignoredReasons)
                ignoredReasons->append(IgnoredReason(AXProbablyPresentational));
            return true;
        }
        // Otherwise fall through; use presence of help text, title, or description to decide.
    }

    if (isWebArea() || m_layoutObject->isListMarker())
        return false;

    // Using the help text, title or accessibility description (so we
    // check if there's some kind of accessible name for the element)
    // to decide an element's visibility is not as definitive as
    // previous checks, so this should remain as one of the last.
    //
    // These checks are simplified in the interest of execution speed;
    // for example, any element having an alt attribute will make it
    // not ignored, rather than just images.
    if (!getAttribute(aria_helpAttr).isEmpty() || !getAttribute(aria_describedbyAttr).isEmpty() || !getAttribute(altAttr).isEmpty() || !getAttribute(titleAttr).isEmpty())
        return false;

    // Don't ignore generic focusable elements like <div tabindex=0>
    // unless they're completely empty, with no children.
    if (isGenericFocusableElement() && node->hasChildren())
        return false;

    if (!ariaAccessibilityDescription().isEmpty())
        return false;

    if (isScrollableContainer())
        return false;

    // Ignore layout objects that are block flows with inline children. These
    // are usually dummy layout objects that pad out the tree, but there are
    // some exceptions below.
    if (m_layoutObject->isLayoutBlockFlow() && m_layoutObject->childrenInline() && !canSetFocusAttribute()) {
        // If the layout object has any plain text in it, that text will be
        // inside a LineBox, so the layout object will have a first LineBox.
        bool hasAnyText = !!toLayoutBlockFlow(m_layoutObject)->firstLineBox();

        // Always include interesting-looking objects.
        if (hasAnyText || mouseButtonListener())
            return false;

        if (ignoredReasons)
            ignoredReasons->append(IgnoredReason(AXUninteresting));
        return true;
    }

    // By default, objects should be ignored so that the AX hierarchy is not
    // filled with unnecessary items.
    if (ignoredReasons)
        ignoredReasons->append(IgnoredReason(AXUninteresting));
    return true;
}

//
// Properties of static elements.
//

const AtomicString& AXLayoutObject::accessKey() const
{
    Node* node = m_layoutObject->node();
    if (!node)
        return nullAtom;
    if (!node->isElementNode())
        return nullAtom;
    return toElement(node)->getAttribute(accesskeyAttr);
}

RGBA32 AXLayoutObject::computeBackgroundColor() const
{
    if (!getLayoutObject())
        return AXNodeObject::backgroundColor();

    Color blendedColor = Color::transparent;
    // Color::blend should be called like this: background.blend(foreground).
    for (LayoutObject* layoutObject = getLayoutObject(); layoutObject;
        layoutObject = layoutObject->parent()) {
        const AXObject* axParent = axObjectCache().getOrCreate(layoutObject);
        if (axParent && axParent != this) {
            Color parentColor = axParent->backgroundColor();
            blendedColor = parentColor.blend(blendedColor);
            return blendedColor.rgb();
        }

        const ComputedStyle* style = layoutObject->style();
        if (!style || !style->hasBackground())
            continue;

        Color currentColor = style->visitedDependentColor(CSSPropertyBackgroundColor);
        blendedColor = currentColor.blend(blendedColor);
        // Continue blending until we get no transparency.
        if (!blendedColor.hasAlpha())
            break;
    }

    // If we still have some transparency, blend in the document base color.
    if (blendedColor.hasAlpha()) {
        FrameView* view = documentFrameView();
        if (view) {
            Color documentBaseColor = view->baseBackgroundColor();
            blendedColor = documentBaseColor.blend(blendedColor);
        } else {
            // Default to a white background.
            blendedColor.blendWithWhite();
        }
    }

    return blendedColor.rgb();
}

RGBA32 AXLayoutObject::color() const
{
    if (!getLayoutObject() || isColorWell())
        return AXNodeObject::color();

    const ComputedStyle* style = getLayoutObject()->style();
    if (!style)
        return AXNodeObject::color();

    Color color = style->visitedDependentColor(CSSPropertyColor);
    return color.rgb();
}

String AXLayoutObject::fontFamily() const
{
    if (!getLayoutObject())
        return AXNodeObject::fontFamily();

    const ComputedStyle* style = getLayoutObject()->style();
    if (!style)
        return AXNodeObject::fontFamily();

    FontDescription& fontDescription = const_cast<FontDescription&>(style->getFontDescription());
    return fontDescription.firstFamily().family();
}

// Font size is in pixels.
float AXLayoutObject::fontSize() const
{
    if (!getLayoutObject())
        return AXNodeObject::fontSize();

    const ComputedStyle* style = getLayoutObject()->style();
    if (!style)
        return AXNodeObject::fontSize();

    return style->computedFontSize();
}

String AXLayoutObject::text() const
{
    if (isPasswordFieldAndShouldHideValue()) {
        if (!getLayoutObject())
            return String();

        const ComputedStyle* style = getLayoutObject()->style();
        if (!style)
            return String();

        unsigned unmaskedTextLength = AXNodeObject::text().length();
        if (!unmaskedTextLength)
            return String();

        UChar maskCharacter = 0;
        switch (style->textSecurity()) {
        case TSNONE:
            break; // Fall through to the non-password branch.
        case TSDISC:
            maskCharacter = bulletCharacter;
            break;
        case TSCIRCLE:
            maskCharacter = whiteBulletCharacter;
            break;
        case TSSQUARE:
            maskCharacter = blackSquareCharacter;
            break;
        }
        if (maskCharacter) {
            StringBuilder maskedText;
            maskedText.reserveCapacity(unmaskedTextLength);
            for (unsigned i = 0; i < unmaskedTextLength; ++i)
                maskedText.append(maskCharacter);
            return maskedText.toString();
        }
    }

    return AXNodeObject::text();
}

AccessibilityTextDirection AXLayoutObject::textDirection() const
{
    if (!getLayoutObject())
        return AXNodeObject::textDirection();

    const ComputedStyle* style = getLayoutObject()->style();
    if (!style)
        return AXNodeObject::textDirection();

    if (style->isHorizontalWritingMode()) {
        switch (style->direction()) {
        case LTR:
            return AccessibilityTextDirectionLTR;
        case RTL:
            return AccessibilityTextDirectionRTL;
        }
    } else {
        switch (style->direction()) {
        case LTR:
            return AccessibilityTextDirectionTTB;
        case RTL:
            return AccessibilityTextDirectionBTT;
        }
    }

    return AXNodeObject::textDirection();
}

int AXLayoutObject::textLength() const
{
    if (!isTextControl())
        return -1;

    return text().length();
}

TextStyle AXLayoutObject::getTextStyle() const
{
    if (!getLayoutObject())
        return AXNodeObject::getTextStyle();

    const ComputedStyle* style = getLayoutObject()->style();
    if (!style)
        return AXNodeObject::getTextStyle();

    unsigned textStyle = TextStyleNone;
    if (style->fontWeight() == FontWeightBold)
        textStyle |= TextStyleBold;
    if (style->getFontDescription().style() == FontStyleItalic)
        textStyle |= TextStyleItalic;
    if (style->getTextDecoration() == TextDecorationUnderline)
        textStyle |= TextStyleUnderline;
    if (style->getTextDecoration() == TextDecorationLineThrough)
        textStyle |= TextStyleLineThrough;

    return static_cast<TextStyle>(textStyle);
}

KURL AXLayoutObject::url() const
{
    if (isAnchor() && isHTMLAnchorElement(m_layoutObject->node())) {
        if (HTMLAnchorElement* anchor = toHTMLAnchorElement(anchorElement()))
            return anchor->href();
    }

    if (isWebArea())
        return m_layoutObject->document().url();

    if (isImage() && isHTMLImageElement(m_layoutObject->node()))
        return toHTMLImageElement(*m_layoutObject->node()).src();

    if (isInputImage())
        return toHTMLInputElement(m_layoutObject->node())->src();

    return KURL();
}

//
// Inline text boxes.
//

void AXLayoutObject::loadInlineTextBoxes()
{
    if (!getLayoutObject() || !getLayoutObject()->isText())
        return;

    clearChildren();
    addInlineTextBoxChildren(true);
}

AXObject* AXLayoutObject::nextOnLine() const
{
    if (!getLayoutObject())
        return nullptr;

    InlineBox* inlineBox = nullptr;
    if (getLayoutObject()->isLayoutInline())
        inlineBox = toLayoutInline(getLayoutObject())->lastLineBox();
    else if (getLayoutObject()->isText())
        inlineBox = toLayoutText(getLayoutObject())->lastTextBox();

    if (!inlineBox)
        return nullptr;

    AXObject* result = nullptr;
    for (InlineBox* next = inlineBox->nextOnLine(); next; next = next->nextOnLine()) {
        LayoutObject* layoutObject = LineLayoutAPIShim::layoutObjectFrom(next->getLineLayoutItem());
        result = axObjectCache().getOrCreate(layoutObject);
        if (result)
            break;
    }

    // A static text node might span multiple lines. Try to return the first inline
    // text box within that static text if possible.
    if (result && result->roleValue() == StaticTextRole && result->children().size())
        result = result->children()[0].get();

    return result;
}

AXObject* AXLayoutObject::previousOnLine() const
{
    if (!getLayoutObject())
        return nullptr;

    InlineBox* inlineBox = nullptr;
    if (getLayoutObject()->isLayoutInline())
        inlineBox = toLayoutInline(getLayoutObject())->firstLineBox();
    else if (getLayoutObject()->isText())
        inlineBox = toLayoutText(getLayoutObject())->firstTextBox();

    if (!inlineBox)
        return nullptr;

    AXObject* result = nullptr;
    for (InlineBox* prev = inlineBox->prevOnLine(); prev; prev = prev->prevOnLine()) {
        LayoutObject* layoutObject = LineLayoutAPIShim::layoutObjectFrom(prev->getLineLayoutItem());
        result = axObjectCache().getOrCreate(layoutObject);
        if (result)
            break;
    }

    // A static text node might span multiple lines. Try to return the last inline
    // text box within that static text if possible.
    if (result && result->roleValue() == StaticTextRole && result->children().size())
        result = result->children()[result->children().size() - 1].get();

    return result;
}

//
// Properties of interactive elements.
//

String AXLayoutObject::stringValue() const
{
    if (!m_layoutObject)
        return String();

    LayoutBoxModelObject* cssBox = getLayoutBoxModelObject();

    if (cssBox && cssBox->isMenuList()) {
        // LayoutMenuList will go straight to the text() of its selected item.
        // This has to be overridden in the case where the selected item has an ARIA label.
        HTMLSelectElement* selectElement = toHTMLSelectElement(m_layoutObject->node());
        int selectedIndex = selectElement->selectedIndex();
        const HeapVector<Member<HTMLElement>>& listItems = selectElement->listItems();
        if (selectedIndex >= 0 && static_cast<size_t>(selectedIndex) < listItems.size()) {
            const AtomicString& overriddenDescription = listItems[selectedIndex]->fastGetAttribute(aria_labelAttr);
            if (!overriddenDescription.isNull())
                return overriddenDescription;
        }
        return toLayoutMenuList(m_layoutObject)->text();
    }

    if (isWebArea()) {
        // FIXME: Why would a layoutObject exist when the Document isn't attached to a frame?
        if (m_layoutObject->frame())
            return String();

        ASSERT_NOT_REACHED();
    }

    if (isTextControl())
        return text();

    if (m_layoutObject->isFileUploadControl())
        return toLayoutFileUploadControl(m_layoutObject)->fileTextValue();

    // Handle other HTML input elements that aren't text controls, like date and time
    // controls, by returning the string value, with the exception of checkboxes
    // and radio buttons (which would return "on").
    if (getNode() && isHTMLInputElement(getNode())) {
        HTMLInputElement* input = toHTMLInputElement(getNode());
        if (input->type() != InputTypeNames::checkbox && input->type() != InputTypeNames::radio)
            return input->value();
    }

    // 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 String();
}

String AXLayoutObject::textAlternative(bool recursive, bool inAriaLabelledByTraversal, AXObjectSet& visited, AXNameFrom& nameFrom, AXRelatedObjectVector* relatedObjects, NameSources* nameSources) const
{
    if (m_layoutObject) {
        String textAlternative;
        bool foundTextAlternative = false;

        if (m_layoutObject->isBR()) {
            textAlternative = String("\n");
            foundTextAlternative = true;
        } else if (m_layoutObject->isText() && (!recursive || !m_layoutObject->isCounter())) {
            LayoutText* layoutText = toLayoutText(m_layoutObject);
            String result = layoutText->plainText();
            if (!result.isEmpty() || layoutText->isAllCollapsibleWhitespace())
                textAlternative = result;
            else
                textAlternative = layoutText->text();
            foundTextAlternative = true;
        } else if (m_layoutObject->isListMarker() && !recursive) {
            textAlternative = toLayoutListMarker(m_layoutObject)->text();
            foundTextAlternative = true;
        }

        if (foundTextAlternative) {
            nameFrom = AXNameFromContents;
            if (nameSources) {
                nameSources->append(NameSource(false));
                nameSources->last().type = nameFrom;
                nameSources->last().text = textAlternative;
            }
            return textAlternative;
        }
    }

    return AXNodeObject::textAlternative(recursive, inAriaLabelledByTraversal, visited, nameFrom, relatedObjects, nameSources);
}

//
// ARIA attributes.
//

void AXLayoutObject::ariaFlowToElements(AXObjectVector& flowTo) const
{
    accessibilityChildrenFromAttribute(aria_flowtoAttr, flowTo);
}

void AXLayoutObject::ariaControlsElements(AXObjectVector& controls) const
{
    accessibilityChildrenFromAttribute(aria_controlsAttr, controls);
}

void AXLayoutObject::ariaOwnsElements(AXObjectVector& owns) const
{
    accessibilityChildrenFromAttribute(aria_ownsAttr, owns);
}

void AXLayoutObject::ariaDescribedbyElements(AXObjectVector& describedby) const
{
    accessibilityChildrenFromAttribute(aria_describedbyAttr, describedby);
}

void AXLayoutObject::ariaLabelledbyElements(AXObjectVector& labelledby) const
{
    accessibilityChildrenFromAttribute(aria_labelledbyAttr, labelledby);
}

bool AXLayoutObject::ariaHasPopup() const
{
    return elementAttributeValue(aria_haspopupAttr);
}

bool AXLayoutObject::ariaRoleHasPresentationalChildren() const
{
    switch (m_ariaRole) {
    case ButtonRole:
    case SliderRole:
    case ImageRole:
    case ProgressIndicatorRole:
    case SpinButtonRole:
    // case SeparatorRole:
        return true;
    default:
        return false;
    }
}

AXObject* AXLayoutObject::ancestorForWhichThisIsAPresentationalChild() const
{
    // Walk the parent chain looking for a parent that has presentational children
    AXObject* parent = parentObjectIfExists();
    while (parent) {
        if (parent->ariaRoleHasPresentationalChildren())
            break;

        // The descendants of a AXMenuList that are AXLayoutObjects are all
        // presentational. (The real descendants are an AXMenuListPopup and
        // AXMenuListOptions, which are not AXLayoutObjects.)
        if (parent->isMenuList())
            break;

        parent = parent->parentObjectIfExists();
    }

    return parent;
}

bool AXLayoutObject::supportsARIADragging() const
{
    const AtomicString& grabbed = getAttribute(aria_grabbedAttr);
    return equalIgnoringCase(grabbed, "true") || equalIgnoringCase(grabbed, "false");
}

bool AXLayoutObject::supportsARIADropping() const
{
    const AtomicString& dropEffect = getAttribute(aria_dropeffectAttr);
    return !dropEffect.isEmpty();
}

bool AXLayoutObject::supportsARIAFlowTo() const
{
    return !getAttribute(aria_flowtoAttr).isEmpty();
}

bool AXLayoutObject::supportsARIAOwns() const
{
    if (!m_layoutObject)
        return false;
    const AtomicString& ariaOwns = getAttribute(aria_ownsAttr);

    return !ariaOwns.isEmpty();
}

//
// ARIA live-region features.
//

const AtomicString& AXLayoutObject::liveRegionStatus() const
{
    DEFINE_STATIC_LOCAL(const AtomicString, liveRegionStatusAssertive, ("assertive"));
    DEFINE_STATIC_LOCAL(const AtomicString, liveRegionStatusPolite, ("polite"));
    DEFINE_STATIC_LOCAL(const AtomicString, liveRegionStatusOff, ("off"));

    const AtomicString& liveRegionStatus = getAttribute(aria_liveAttr);
    // These roles have implicit live region status.
    if (liveRegionStatus.isEmpty()) {
        switch (roleValue()) {
        case AlertDialogRole:
        case AlertRole:
            return liveRegionStatusAssertive;
        case LogRole:
        case StatusRole:
            return liveRegionStatusPolite;
        case TimerRole:
        case MarqueeRole:
            return liveRegionStatusOff;
        default:
            break;
        }
    }

    return liveRegionStatus;
}

const AtomicString& AXLayoutObject::liveRegionRelevant() const
{
    DEFINE_STATIC_LOCAL(const AtomicString, defaultLiveRegionRelevant, ("additions text"));
    const AtomicString& relevant = getAttribute(aria_relevantAttr);

    // Default aria-relevant = "additions text".
    if (relevant.isEmpty())
        return defaultLiveRegionRelevant;

    return relevant;
}

bool AXLayoutObject::liveRegionAtomic() const
{
    // ARIA roles "alert" and "status" should have an implicit aria-atomic value of true.
    if (getAttribute(aria_atomicAttr).isEmpty()
        && (roleValue() == AlertRole || roleValue() == StatusRole)) {
        return true;
    }
    return elementAttributeValue(aria_atomicAttr);
}

bool AXLayoutObject::liveRegionBusy() const
{
    return elementAttributeValue(aria_busyAttr);
}

//
// Position and size.
//

void AXLayoutObject::checkCachedElementRect() const
{
    if (m_cachedElementRectDirty)
        return;

    if (!m_layoutObject)
        return;

    if (!m_layoutObject->isBox())
        return;

    bool dirty = false;
    LayoutBox* box = toLayoutBox(m_layoutObject);
    if (box->frameRect() != m_cachedFrameRect)
        dirty = true;

    if (box->canBeScrolledAndHasScrollableArea()) {
        ScrollableArea* scrollableArea = box->getScrollableArea();
        if (scrollableArea && scrollableArea->scrollPosition() != m_cachedScrollPosition)
            dirty = true;
    }

    if (dirty)
        markCachedElementRectDirty();
}

void AXLayoutObject::updateCachedElementRect() const
{
    if (!m_cachedElementRectDirty)
        return;

    if (!m_layoutObject)
        return;

    if (!m_layoutObject->isBox())
        return;

    LayoutBox* box = toLayoutBox(m_layoutObject);
    m_cachedFrameRect = box->frameRect();

    if (box->canBeScrolledAndHasScrollableArea()) {
        ScrollableArea* scrollableArea = box->getScrollableArea();
        if (scrollableArea)
            m_cachedScrollPosition = scrollableArea->scrollPosition();
    }

    m_cachedElementRect = computeElementRect();
    m_cachedElementRectDirty = false;
}

void AXLayoutObject::markCachedElementRectDirty() const
{
    if (m_cachedElementRectDirty)
        return;

    // Marks children recursively, if this element changed.
    m_cachedElementRectDirty = true;
    for (AXObject* child = rawFirstChild(); child; child = child->rawNextSibling())
        child->markCachedElementRectDirty();
}

IntPoint AXLayoutObject::clickPoint()
{
    // Headings are usually much wider than their textual content. If the mid point is used, often it can be wrong.
    if (isHeading() && children().size() == 1)
        return children()[0]->clickPoint();

    // use the default position unless this is an editable web area, in which case we use the selection bounds.
    if (!isWebArea() || isReadOnly())
        return AXObject::clickPoint();

    IntRect bounds = pixelSnappedIntRect(elementRect());
    return IntPoint(bounds.x() + (bounds.width() / 2), bounds.y() - (bounds.height() / 2));
}

//
// Hit testing.
//

AXObject* AXLayoutObject::accessibilityHitTest(const IntPoint& point) const
{
    if (!m_layoutObject || !m_layoutObject->hasLayer())
        return nullptr;

    PaintLayer* layer = toLayoutBox(m_layoutObject)->layer();

    HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active);
    HitTestResult hitTestResult = HitTestResult(request, point);
    layer->hitTest(hitTestResult);

    Node* node = hitTestResult.innerNode();
    if (!node)
        return nullptr;

    if (isHTMLAreaElement(node))
        return accessibilityImageMapHitTest(toHTMLAreaElement(node), point);

    if (isHTMLOptionElement(node)) {
        node = toHTMLOptionElement(*node).ownerSelectElement();
        if (!node)
            return nullptr;
    }

    LayoutObject* obj = node->layoutObject();
    if (!obj)
        return nullptr;

    AXObject* result = axObjectCache().getOrCreate(obj);
    result->updateChildrenIfNecessary();

    // Allow the element to perform any hit-testing it might need to do to reach non-layout children.
    result = result->elementAccessibilityHitTest(point);
    if (result && result->accessibilityIsIgnored()) {
        // If this element is the label of a control, a hit test should return the control.
        if (result->isAXLayoutObject()) {
            AXObject* controlObject = toAXLayoutObject(result)->correspondingControlForLabelElement();
            if (controlObject && controlObject->nameFromLabelElement())
                return controlObject;
        }

        result = result->parentObjectUnignored();
    }

    return result;
}

AXObject* AXLayoutObject::elementAccessibilityHitTest(const IntPoint& point) const
{
    if (isSVGImage())
        return remoteSVGElementHitTest(point);

    return AXObject::elementAccessibilityHitTest(point);
}

//
// High-level accessibility tree access.
//

AXObject* AXLayoutObject::computeParent() const
{
    ASSERT(!isDetached());
    if (!m_layoutObject)
        return 0;

    if (ariaRoleAttribute() == MenuBarRole)
        return axObjectCache().getOrCreate(m_layoutObject->parent());

    // menuButton and its corresponding menu are DOM siblings, but Accessibility needs them to be parent/child
    if (ariaRoleAttribute() == MenuRole) {
        AXObject* parent = menuButtonForMenu();
        if (parent)
            return parent;
    }

    LayoutObject* parentObj = layoutParentObject();
    if (parentObj)
        return axObjectCache().getOrCreate(parentObj);

    // A WebArea's parent should be the page popup owner, if any, otherwise null.
    if (isWebArea()) {
        LocalFrame* frame = m_layoutObject->frame();
        return axObjectCache().getOrCreate(frame->pagePopupOwner());
    }

    return 0;
}

AXObject* AXLayoutObject::computeParentIfExists() const
{
    if (!m_layoutObject)
        return 0;

    if (ariaRoleAttribute() == MenuBarRole)
        return axObjectCache().get(m_layoutObject->parent());

    // menuButton and its corresponding menu are DOM siblings, but Accessibility needs them to be parent/child
    if (ariaRoleAttribute() == MenuRole) {
        AXObject* parent = menuButtonForMenu();
        if (parent)
            return parent;
    }

    LayoutObject* parentObj = layoutParentObject();
    if (parentObj)
        return axObjectCache().get(parentObj);

    // A WebArea's parent should be the page popup owner, if any, otherwise null.
    if (isWebArea()) {
        LocalFrame* frame = m_layoutObject->frame();
        return axObjectCache().get(frame->pagePopupOwner());
    }

    return 0;
}

//
// Low-level accessibility tree exploration, only for use within the accessibility module.
//

AXObject* AXLayoutObject::rawFirstChild() const
{
    if (!m_layoutObject)
        return 0;

    LayoutObject* firstChild = firstChildConsideringContinuation(m_layoutObject);

    if (!firstChild)
        return 0;

    return axObjectCache().getOrCreate(firstChild);
}

AXObject* AXLayoutObject::rawNextSibling() const
{
    if (!m_layoutObject)
        return 0;

    LayoutObject* nextSibling = 0;

    LayoutInline* inlineContinuation = m_layoutObject->isLayoutBlockFlow() ? toLayoutBlockFlow(m_layoutObject)->inlineElementContinuation() : nullptr;
    if (inlineContinuation) {
        // Case 1: node is a block and has an inline continuation. Next sibling is the inline continuation's first child.
        nextSibling = firstChildConsideringContinuation(inlineContinuation);
    } else if (m_layoutObject->isAnonymousBlock() && lastChildHasContinuation(m_layoutObject)) {
        // Case 2: Anonymous block parent of the start of a continuation - skip all the way to
        // after the parent of the end, since everything in between will be linked up via the continuation.
        LayoutObject* lastParent = endOfContinuations(toLayoutBlock(m_layoutObject)->lastChild())->parent();
        while (lastChildHasContinuation(lastParent))
            lastParent = endOfContinuations(lastParent->slowLastChild())->parent();
        nextSibling = lastParent->nextSibling();
    } else if (LayoutObject* ns = m_layoutObject->nextSibling()) {
        // Case 3: node has an actual next sibling
        nextSibling = ns;
    } else if (isInlineWithContinuation(m_layoutObject)) {
        // Case 4: node is an inline with a continuation. Next sibling is the next sibling of the end
        // of the continuation chain.
        nextSibling = endOfContinuations(m_layoutObject)->nextSibling();
    } else if (m_layoutObject->parent() && isInlineWithContinuation(m_layoutObject->parent())) {
        // Case 5: node has no next sibling, and its parent is an inline with a continuation.
        LayoutObject* continuation = toLayoutInline(m_layoutObject->parent())->continuation();

        if (continuation->isLayoutBlock()) {
            // Case 5a: continuation is a block - in this case the block itself is the next sibling.
            nextSibling = continuation;
        } else {
            // Case 5b: continuation is an inline - in this case the inline's first child is the next sibling.
            nextSibling = firstChildConsideringContinuation(continuation);
        }
    }

    if (!nextSibling)
        return 0;

    return axObjectCache().getOrCreate(nextSibling);
}

void AXLayoutObject::addChildren()
{
    ASSERT(!isDetached());
    // 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_haveChildren);

    m_haveChildren = true;

    if (!canHaveChildren())
        return;

    HeapVector<Member<AXObject>> ownedChildren;
    computeAriaOwnsChildren(ownedChildren);

    for (AXObject* obj = rawFirstChild(); obj; obj = obj->rawNextSibling()) {
        if (!axObjectCache().isAriaOwned(obj)) {
            obj->setParent(this);
            addChild(obj);
        }
    }

    addHiddenChildren();
    addPopupChildren();
    addImageMapChildren();
    addTextFieldChildren();
    addCanvasChildren();
    addRemoteSVGChildren();
    addInlineTextBoxChildren(false);

    for (const auto& child : m_children) {
        if (!child->cachedParentObject())
            child->setParent(this);
    }

    for (const auto& ownedChild : ownedChildren)
        addChild(ownedChild);
}

bool AXLayoutObject::canHaveChildren() const
{
    if (!m_layoutObject)
        return false;

    return AXNodeObject::canHaveChildren();
}

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

    AXObject::updateChildrenIfNecessary();
}

void AXLayoutObject::clearChildren()
{
    AXObject::clearChildren();
    m_childrenDirty = false;
}

//
// Properties of the object's owning document or page.
//

double AXLayoutObject::estimatedLoadingProgress() const
{
    if (!m_layoutObject)
        return 0;

    if (isLoaded())
        return 1.0;

    if (LocalFrame* frame = m_layoutObject->document().frame())
        return frame->loader().progress().estimatedProgress();
    return 0;
}

//
// DOM and layout tree access.
//

Node* AXLayoutObject::getNode() const
{
    return getLayoutObject() ? getLayoutObject()->node() : nullptr;
}

Document* AXLayoutObject::getDocument() const
{
    if (!getLayoutObject())
        return nullptr;
    return &getLayoutObject()->document();
}

FrameView* AXLayoutObject::documentFrameView() const
{
    if (!getLayoutObject())
        return nullptr;

    // this is the LayoutObject's Document's LocalFrame's FrameView
    return getLayoutObject()->document().view();
}

Element* AXLayoutObject::anchorElement() const
{
    if (!m_layoutObject)
        return 0;

    AXObjectCacheImpl& cache = axObjectCache();
    LayoutObject* currLayoutObject;

    // Search up the layout tree for a LayoutObject with a DOM node. Defer to an earlier continuation, though.
    for (currLayoutObject = m_layoutObject; currLayoutObject && !currLayoutObject->node(); currLayoutObject = currLayoutObject->parent()) {
        if (currLayoutObject->isAnonymousBlock() && currLayoutObject->isLayoutBlockFlow()) {
            LayoutObject* continuation = toLayoutBlockFlow(currLayoutObject)->continuation();
            if (continuation)
                return cache.getOrCreate(continuation)->anchorElement();
        }
    }

    // bail if none found
    if (!currLayoutObject)
        return 0;

    // search up the DOM tree for an anchor element
    // NOTE: this assumes that any non-image with an anchor is an HTMLAnchorElement
    Node* node = currLayoutObject->node();
    if (!node)
        return nullptr;
    for (Node& runner : NodeTraversal::inclusiveAncestorsOf(*node)) {
        if (isHTMLAnchorElement(runner) || (runner.layoutObject() && cache.getOrCreate(runner.layoutObject())->isAnchor()))
            return toElement(&runner);
    }

    return 0;
}

//
// Functions that retrieve the current selection.
//

AXObject::AXRange AXLayoutObject::selection() const
{
    AXRange textSelection = textControlSelection();
    if (textSelection.isValid())
        return textSelection;

    if (!getLayoutObject() || !getLayoutObject()->frame())
        return AXRange();

    VisibleSelection selection = getLayoutObject()->frame()->selection().selection();
    if (selection.isNone())
        return AXRange();

    VisiblePosition visibleStart = selection.visibleStart();
    Position start = visibleStart.toParentAnchoredPosition();
    TextAffinity startAffinity = visibleStart.affinity();
    VisiblePosition visibleEnd = selection.visibleEnd();
    Position end = visibleEnd.toParentAnchoredPosition();
    TextAffinity endAffinity = visibleEnd.affinity();

    Node* anchorNode = start.anchorNode();
    ASSERT(anchorNode);

    AXLayoutObject* anchorObject = nullptr;
    // Find the closest node that has a corresponding AXObject.
    // This is because some nodes may be aria hidden or might not even have
    // a layout object if they are part of the shadow DOM.
    while (anchorNode) {
        anchorObject = getUnignoredObjectFromNode(*anchorNode);
        if (anchorObject)
            break;

        if (anchorNode->nextSibling())
            anchorNode = anchorNode->nextSibling();
        else
            anchorNode = anchorNode->parentNode();
    }

    Node* focusNode = end.anchorNode();
    ASSERT(focusNode);

    AXLayoutObject* focusObject = nullptr;
    while (focusNode) {
        focusObject = getUnignoredObjectFromNode(*focusNode);
        if (focusObject)
            break;

        if (focusNode->previousSibling())
            focusNode = focusNode->previousSibling();
        else
            focusNode = focusNode->parentNode();
    }

    if (!anchorObject || !focusObject)
        return AXRange();

    int anchorOffset = anchorObject->indexForVisiblePosition(visibleStart);
    ASSERT(anchorOffset >= 0);
    int focusOffset = focusObject->indexForVisiblePosition(visibleEnd);
    ASSERT(focusOffset >= 0);
    return AXRange(anchorObject, anchorOffset, startAffinity,
        focusObject, focusOffset, endAffinity);
}

// Gets only the start and end offsets of the selection computed using the
// current object as the starting point. Returns a null selection if there is
// no selection in the subtree rooted at this object.
AXObject::AXRange AXLayoutObject::selectionUnderObject() const
{
    AXRange textSelection = textControlSelection();
    if (textSelection.isValid())
        return textSelection;

    if (!getNode() || !getLayoutObject()->frame())
        return AXRange();

    VisibleSelection selection = getLayoutObject()->frame()->selection().selection();
    Range* selectionRange = firstRangeOf(selection);
    ContainerNode* parentNode = getNode()->parentNode();
    int nodeIndex = getNode()->nodeIndex();
    if (!selectionRange
        // Selection is contained in node.
        || !(parentNode
        && selectionRange->comparePoint(parentNode, nodeIndex, IGNORE_EXCEPTION) < 0
        && selectionRange->comparePoint(parentNode, nodeIndex + 1, IGNORE_EXCEPTION) > 0)) {
        return AXRange();
    }

    int start = indexForVisiblePosition(selection.visibleStart());
    ASSERT(start >= 0);
    int end = indexForVisiblePosition(selection.visibleEnd());
    ASSERT(end >= 0);

    return AXRange(start, end);
}

AXObject::AXRange AXLayoutObject::textControlSelection() const
{
    if (!getLayoutObject())
        return AXRange();

    LayoutObject* layout = nullptr;
    if (getLayoutObject()->isTextControl()) {
        layout = getLayoutObject();
    } else {
        Element* focusedElement = getDocument()->focusedElement();
        if (focusedElement && focusedElement->layoutObject()
            && focusedElement->layoutObject()->isTextControl())
            layout = focusedElement->layoutObject();
    }

    if (!layout)
        return AXRange();

    AXObject* axObject = axObjectCache().getOrCreate(layout);
    if (!axObject || !axObject->isAXLayoutObject())
        return AXRange();

    VisibleSelection selection = layout->frame()->selection().selection();
    HTMLTextFormControlElement* textControl = toLayoutTextControl(
        layout)->textFormControlElement();
    ASSERT(textControl);
    int start = textControl->selectionStart();
    int end = textControl->selectionEnd();

    return AXRange(axObject, start, selection.visibleStart().affinity(),
        axObject, end, selection.visibleEnd().affinity());
}

int AXLayoutObject::indexForVisiblePosition(const VisiblePosition& position) const
{
    if (getLayoutObject() && getLayoutObject()->isTextControl()) {
        HTMLTextFormControlElement* textControl = toLayoutTextControl(
            getLayoutObject())->textFormControlElement();
        return textControl->indexForVisiblePosition(position);
    }

    if (!getNode())
        return 0;

    Position indexPosition = position.deepEquivalent();
    if (indexPosition.isNull())
        return 0;

    Range* range = Range::create(*getDocument());
    range->setStart(getNode(), 0, IGNORE_EXCEPTION);
    range->setEnd(indexPosition, IGNORE_EXCEPTION);

    return TextIterator::rangeLength(range->startPosition(), range->endPosition());
}

AXLayoutObject* AXLayoutObject::getUnignoredObjectFromNode(Node& node) const
{
    if (isDetached())
        return nullptr;

    AXObject* axObject = axObjectCache().getOrCreate(&node);
    if (!axObject)
        return nullptr;

    if (axObject->isAXLayoutObject() && !axObject->accessibilityIsIgnored())
        return toAXLayoutObject(axObject);

    return nullptr;
}


//
// Modify or take an action on an object.
//

// Convert from an accessible object and offset to a VisiblePosition.
static VisiblePosition toVisiblePosition(AXObject* obj, int offset)
{
    // First walk up until we find an accessible object with an associated node.
    AXObject* runner = obj;
    Node* node = nullptr;
    while (runner && !node) {
        node = runner->getNode();
        runner = runner->parentObject();
    }

    if (!node)
        return VisiblePosition();

    // If it's not a text node, no conversion is necessary, just create a VisiblePosition
    // with this node and offset.
    if (!node->isTextNode())
        return createVisiblePosition(Position(node, offset));

    // If it is a text node, we need to call some utility functions that use a TextIterator
    // to walk the characters of the node and figure out the position corresponding to the
    // visible character at position |offset|.
    ContainerNode* parent = node->parentNode();
    if (!parent)
        return VisiblePosition();

    VisiblePosition nodePosition = blink::visiblePositionBeforeNode(*node);
    int nodeIndex = blink::indexForVisiblePosition(nodePosition, parent);
    return blink::visiblePositionForIndex(nodeIndex + offset, parent);
}

void AXLayoutObject::setSelection(const AXRange& selection)
{
    if (!getLayoutObject() || !selection.isValid())
        return;

    AXObject* anchorObject = selection.anchorObject ?
        selection.anchorObject.get() : this;
    AXObject* focusObject = selection.focusObject ?
        selection.focusObject.get() : this;

    if (!isValidSelectionBound(anchorObject)
        || !isValidSelectionBound(focusObject)) {
        return;
    }

    if (anchorObject == focusObject
        && anchorObject->getLayoutObject()->isTextControl()) {
        HTMLTextFormControlElement* textControl = toLayoutTextControl(
            anchorObject->getLayoutObject())->textFormControlElement();
        if (selection.anchorOffset <= selection.focusOffset) {
            textControl->setSelectionRange(
                selection.anchorOffset, selection.focusOffset,
                SelectionHasForwardDirection, NotDispatchSelectEvent);
        } else {
            textControl->setSelectionRange(
                selection.focusOffset, selection.anchorOffset,
                SelectionHasBackwardDirection, NotDispatchSelectEvent);
        }
        return;
    }

    LocalFrame* frame = getLayoutObject()->frame();
    if (!frame)
        return;

    // TODO(dglazkov): The use of updateStyleAndLayoutIgnorePendingStylesheets needs to be audited.
    // see http://crbug.com/590369 for more details.
    // This callsite should probably move up the stack.
    frame->document()->updateStyleAndLayoutIgnorePendingStylesheets();

    // Set the selection based on visible positions, because the offsets in accessibility nodes
    // are based on visible indexes, which often skips redundant whitespace, for example.
    VisiblePosition anchorVisiblePosition = toVisiblePosition(anchorObject, selection.anchorOffset);
    VisiblePosition focusVisiblePosition = toVisiblePosition(focusObject, selection.focusOffset);
    if (anchorVisiblePosition.isNull() || focusVisiblePosition.isNull())
        return;

    frame->selection().setSelection(VisibleSelection(anchorVisiblePosition, focusVisiblePosition));
}

bool AXLayoutObject::isValidSelectionBound(const AXObject* boundObject) const
{
    return getLayoutObject() && boundObject && !boundObject->isDetached()
        && boundObject->isAXLayoutObject() && boundObject->getLayoutObject()
        && boundObject->getLayoutObject()->frame() == getLayoutObject()->frame()
        && &boundObject->axObjectCache() == &axObjectCache();
}

void AXLayoutObject::setValue(const String& string)
{
    if (!getNode() || !getNode()->isElementNode())
        return;
    if (!m_layoutObject || !m_layoutObject->isBoxModelObject())
        return;

    LayoutBoxModelObject* layoutObject = toLayoutBoxModelObject(m_layoutObject);
    if (layoutObject->isTextField() && isHTMLInputElement(*getNode()))
        toHTMLInputElement(*getNode()).setValue(string, DispatchInputAndChangeEvent);
    else if (layoutObject->isTextArea() && isHTMLTextAreaElement(*getNode()))
        toHTMLTextAreaElement(*getNode()).setValue(string, DispatchInputAndChangeEvent);
}

//
// Notifications that this object may have changed.
//

void AXLayoutObject::handleActiveDescendantChanged()
{
    if (!getLayoutObject())
        return;

    AXObject* focusedObject = axObjectCache().focusedObject();
    if (focusedObject == this && supportsActiveDescendant()) {
        axObjectCache().postNotification(
            getLayoutObject(), AXObjectCacheImpl::AXActiveDescendantChanged);
    }
}

void AXLayoutObject::handleAriaExpandedChanged()
{
    // Find if a parent of this object should handle aria-expanded changes.
    AXObject* containerParent = this->parentObject();
    while (containerParent) {
        bool foundParent = false;

        switch (containerParent->roleValue()) {
        case TreeRole:
        case TreeGridRole:
        case GridRole:
        case TableRole:
            foundParent = true;
            break;
        default:
            break;
        }

        if (foundParent)
            break;

        containerParent = containerParent->parentObject();
    }

    // Post that the row count changed.
    if (containerParent)
        axObjectCache().postNotification(containerParent, AXObjectCacheImpl::AXRowCountChanged);

    // Post that the specific row either collapsed or expanded.
    AccessibilityExpanded expanded = isExpanded();
    if (!expanded)
        return;

    if (roleValue() == RowRole || roleValue() == TreeItemRole) {
        AXObjectCacheImpl::AXNotification notification = AXObjectCacheImpl::AXRowExpanded;
        if (expanded == ExpandedCollapsed)
            notification = AXObjectCacheImpl::AXRowCollapsed;

        axObjectCache().postNotification(this, notification);
    } else {
        axObjectCache().postNotification(this, AXObjectCacheImpl::AXExpandedChanged);
    }
}

void AXLayoutObject::textChanged()
{
    if (!m_layoutObject)
        return;

    Settings* settings = getDocument()->settings();
    if (settings && settings->inlineTextBoxAccessibilityEnabled() && roleValue() == StaticTextRole)
        childrenChanged();

    // Do this last - AXNodeObject::textChanged posts live region announcements,
    // and we should update the inline text boxes first.
    AXNodeObject::textChanged();
}

//
// Text metrics. Most of these should be deprecated, needs major cleanup.
//

// NOTE: Consider providing this utility method as AX API
int AXLayoutObject::index(const VisiblePosition& position) const
{
    if (position.isNull() || !isTextControl())
        return -1;

    if (layoutObjectContainsPosition(m_layoutObject, position.deepEquivalent()))
        return indexForVisiblePosition(position);

    return -1;
}

VisiblePosition AXLayoutObject::visiblePositionForIndex(int index) const
{
    if (!m_layoutObject)
        return VisiblePosition();

    if (m_layoutObject->isTextControl())
        return toLayoutTextControl(m_layoutObject)->textFormControlElement()->visiblePositionForIndex(index);

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

    if (index <= 0)
        return createVisiblePosition(firstPositionInOrBeforeNode(node));

    Position start, end;
    bool selected = Range::selectNodeContents(node, start, end);
    if (!selected)
        return VisiblePosition();

    CharacterIterator it(start, end);
    it.advance(index - 1);
    return createVisiblePosition(Position(it.currentContainer(), it.endOffset()), TextAffinity::Upstream);
}

void AXLayoutObject::addInlineTextBoxChildren(bool force)
{
    Settings* settings = getDocument()->settings();
    if (!force && (!settings || !settings->inlineTextBoxAccessibilityEnabled()))
        return;

    if (!getLayoutObject() || !getLayoutObject()->isText())
        return;

    if (getLayoutObject()->needsLayout()) {
        // If a LayoutText needs layout, its inline text boxes are either
        // nonexistent or invalid, so defer until the layout happens and
        // the layoutObject calls AXObjectCacheImpl::inlineTextBoxesUpdated.
        return;
    }

    LayoutText* layoutText = toLayoutText(getLayoutObject());
    for (RefPtr<AbstractInlineTextBox> box = layoutText->firstAbstractInlineTextBox(); box.get(); box = box->nextInlineTextBox()) {
        AXObject* axObject = axObjectCache().getOrCreate(box.get());
        if (!axObject->accessibilityIsIgnored())
            m_children.append(axObject);
    }
}

void AXLayoutObject::lineBreaks(Vector<int>& lineBreaks) const
{
    if (!isTextControl())
        return;

    VisiblePosition visiblePos = visiblePositionForIndex(0);
    VisiblePosition prevVisiblePos = visiblePos;
    visiblePos = nextLinePosition(visiblePos, LayoutUnit(), HasEditableAXRole);
    // nextLinePosition moves to the end of the current line when there are
    // no more lines.
    while (visiblePos.isNotNull() && !inSameLine(prevVisiblePos, visiblePos)) {
        lineBreaks.append(indexForVisiblePosition(visiblePos));
        prevVisiblePos = visiblePos;
        visiblePos = nextLinePosition(visiblePos, LayoutUnit(), HasEditableAXRole);

        // Make sure we always make forward progress.
        if (visiblePos.deepEquivalent().compareTo(prevVisiblePos.deepEquivalent()) < 0)
            break;
    }
}

//
// Private.
//

AXObject* AXLayoutObject::treeAncestorDisallowingChild() const
{
    // Determine if this is in a tree. If so, we apply special behavior to make it work like an AXOutline.
    AXObject* axObj = parentObject();
    AXObject* treeAncestor = 0;
    while (axObj) {
        if (axObj->isTree()) {
            treeAncestor = axObj;
            break;
        }
        axObj = axObj->parentObject();
    }

    // If the object is in a tree, only tree items should be exposed (and the children of tree items).
    if (treeAncestor) {
        AccessibilityRole role = roleValue();
        if (role != TreeItemRole && role != StaticTextRole)
            return treeAncestor;
    }
    return 0;
}

bool AXLayoutObject::isTabItemSelected() const
{
    if (!isTabItem() || !getLayoutObject())
        return false;

    Node* node = getNode();
    if (!node || !node->isElementNode())
        return false;

    // The ARIA spec says a tab item can also be selected if it is aria-labeled by a tabpanel
    // that has keyboard focus inside of it, or if a tabpanel in its aria-controls list has KB
    // focus inside of it.
    AXObject* focusedElement = axObjectCache().focusedObject();
    if (!focusedElement)
        return false;

    HeapVector<Member<Element>> elements;
    elementsFromAttribute(elements, aria_controlsAttr);

    for (const auto& element : elements) {
        AXObject* tabPanel = axObjectCache().getOrCreate(element);

        // A tab item should only control tab panels.
        if (!tabPanel || tabPanel->roleValue() != TabPanelRole)
            continue;

        AXObject* checkFocusElement = focusedElement;
        // Check if the focused element is a descendant of the element controlled by the tab item.
        while (checkFocusElement) {
            if (tabPanel == checkFocusElement)
                return true;
            checkFocusElement = checkFocusElement->parentObject();
        }
    }

    return false;
}

AXObject* AXLayoutObject::accessibilityImageMapHitTest(HTMLAreaElement* area, const IntPoint& point) const
{
    if (!area)
        return 0;

    AXObject* parent = axObjectCache().getOrCreate(area->imageElement());
    if (!parent)
        return 0;

    for (const auto& child : parent->children()) {
        if (child->elementRect().contains(point))
            return child.get();
    }

    return 0;
}

LayoutObject* AXLayoutObject::layoutParentObject() const
{
    if (!m_layoutObject)
        return 0;

    LayoutObject* startOfConts = m_layoutObject->isLayoutBlockFlow() ? startOfContinuations(m_layoutObject) : nullptr;
    if (startOfConts) {
        // Case 1: node is a block and is an inline's continuation. Parent
        // is the start of the continuation chain.
        return startOfConts;
    }

    LayoutObject* parent = m_layoutObject->parent();
    startOfConts = parent && parent->isLayoutInline() ? startOfContinuations(parent) : 0;
    if (startOfConts) {
        // Case 2: node's parent is an inline which is some node's continuation; parent is
        // the earliest node in the continuation chain.
        return startOfConts;
    }

    LayoutObject* firstChild = parent ? parent->slowFirstChild() : 0;
    if (firstChild && firstChild->node()) {
        // Case 3: The first sibling is the beginning of a continuation chain. Find the origin of that continuation.
        // Get the node's layoutObject and follow that continuation chain until the first child is found.
        for (LayoutObject* nodeLayoutFirstChild = firstChild->node()->layoutObject(); nodeLayoutFirstChild != firstChild; nodeLayoutFirstChild = firstChild->node()->layoutObject()) {
            for (LayoutObject* contsTest = nodeLayoutFirstChild; contsTest; contsTest = nextContinuation(contsTest)) {
                if (contsTest == firstChild) {
                    parent = nodeLayoutFirstChild->parent();
                    break;
                }
            }
            LayoutObject* newFirstChild = parent->slowFirstChild();
            if (firstChild == newFirstChild)
                break;
            firstChild = newFirstChild;
            if (!firstChild->node())
                break;
        }
    }

    return parent;
}

bool AXLayoutObject::isSVGImage() const
{
    return remoteSVGRootElement();
}

void AXLayoutObject::detachRemoteSVGRoot()
{
    if (AXSVGRoot* root = remoteSVGRootElement())
        root->setParent(0);
}

AXSVGRoot* AXLayoutObject::remoteSVGRootElement() const
{
    // FIXME(dmazzoni): none of this code properly handled multiple references to the same
    // remote SVG document. I'm disabling this support until it can be fixed properly.
    return 0;
}

AXObject* AXLayoutObject::remoteSVGElementHitTest(const IntPoint& point) const
{
    AXObject* remote = remoteSVGRootElement();
    if (!remote)
        return 0;

    IntSize offset = point - roundedIntPoint(elementRect().location());
    return remote->accessibilityHitTest(IntPoint(offset));
}

// The boundingBox for elements within the remote SVG element needs to be offset by its position
// within the parent page, otherwise they are in relative coordinates only.
void AXLayoutObject::offsetBoundingBoxForRemoteSVGElement(LayoutRect& rect) const
{
    for (AXObject* parent = parentObject(); parent; parent = parent->parentObject()) {
        if (parent->isAXSVGRoot()) {
            rect.moveBy(parent->parentObject()->elementRect().location());
            break;
        }
    }
}

// Hidden children are those that are not laid out or visible, but are specifically marked as aria-hidden=false,
// meaning that they should be exposed to the AX hierarchy.
void AXLayoutObject::addHiddenChildren()
{
    Node* node = this->getNode();
    if (!node)
        return;

    // First do a quick run through to determine if we have any hidden nodes (most often we will not).
    // If we do have hidden nodes, we need to determine where to insert them so they match DOM order as close as possible.
    bool shouldInsertHiddenNodes = false;
    for (Node& child : NodeTraversal::childrenOf(*node)) {
        if (!child.layoutObject() && isNodeAriaVisible(&child)) {
            shouldInsertHiddenNodes = true;
            break;
        }
    }

    if (!shouldInsertHiddenNodes)
        return;

    // Iterate through all of the children, including those that may have already been added, and
    // try to insert hidden nodes in the correct place in the DOM order.
    unsigned insertionIndex = 0;
    for (Node& child : NodeTraversal::childrenOf(*node)) {
        if (child.layoutObject()) {
            // Find out where the last layout sibling is located within m_children.
            if (AXObject* childObject = axObjectCache().get(child.layoutObject())) {
                if (childObject->accessibilityIsIgnored()) {
                    const auto& children = childObject->children();
                    childObject = children.size() ? children.last().get() : 0;
                }
                if (childObject)
                    insertionIndex = m_children.find(childObject) + 1;
                continue;
            }
        }

        if (!isNodeAriaVisible(&child))
            continue;

        unsigned previousSize = m_children.size();
        if (insertionIndex > previousSize)
            insertionIndex = previousSize;

        insertChild(axObjectCache().getOrCreate(&child), insertionIndex);
        insertionIndex += (m_children.size() - previousSize);
    }
}

void AXLayoutObject::addTextFieldChildren()
{
    Node* node = this->getNode();
    if (!isHTMLInputElement(node))
        return;

    HTMLInputElement& input = toHTMLInputElement(*node);
    Element* spinButtonElement = input.userAgentShadowRoot()->getElementById(ShadowElementNames::spinButton());
    if (!spinButtonElement || !spinButtonElement->isSpinButtonElement())
        return;

    AXSpinButton* axSpinButton = toAXSpinButton(axObjectCache().getOrCreate(SpinButtonRole));
    axSpinButton->setSpinButtonElement(toSpinButtonElement(spinButtonElement));
    axSpinButton->setParent(this);
    m_children.append(axSpinButton);
}

void AXLayoutObject::addImageMapChildren()
{
    LayoutBoxModelObject* cssBox = getLayoutBoxModelObject();
    if (!cssBox || !cssBox->isLayoutImage())
        return;

    HTMLMapElement* map = toLayoutImage(cssBox)->imageMap();
    if (!map)
        return;

    for (HTMLAreaElement& area : Traversal<HTMLAreaElement>::descendantsOf(*map)) {
        // add an <area> element for this child if it has a link
        AXObject* obj = axObjectCache().getOrCreate(&area);
        if (obj) {
            AXImageMapLink* areaObject = toAXImageMapLink(obj);
            areaObject->setParent(this);
            ASSERT(areaObject->axObjectID() != 0);
            if (!areaObject->accessibilityIsIgnored())
                m_children.append(areaObject);
            else
                axObjectCache().remove(areaObject->axObjectID());
        }
    }
}

void AXLayoutObject::addCanvasChildren()
{
    if (!isHTMLCanvasElement(getNode()))
        return;

    // If it's a canvas, it won't have laid out children, but it might have accessible fallback content.
    // Clear m_haveChildren because AXNodeObject::addChildren will expect it to be false.
    ASSERT(!m_children.size());
    m_haveChildren = false;
    AXNodeObject::addChildren();
}

void AXLayoutObject::addPopupChildren()
{
    if (!isHTMLInputElement(getNode()))
        return;
    if (AXObject* axPopup = toHTMLInputElement(getNode())->popupRootAXObject())
        m_children.append(axPopup);
}

void AXLayoutObject::addRemoteSVGChildren()
{
    AXSVGRoot* root = remoteSVGRootElement();
    if (!root)
        return;

    root->setParent(this);

    if (root->accessibilityIsIgnored()) {
        for (const auto& child : root->children())
            m_children.append(child);
    } else {
        m_children.append(root);
    }
}

bool AXLayoutObject::elementAttributeValue(const QualifiedName& attributeName) const
{
    if (!m_layoutObject)
        return false;

    return equalIgnoringCase(getAttribute(attributeName), "true");
}

LayoutRect AXLayoutObject::computeElementRect() const
{
    LayoutObject* obj = m_layoutObject;

    if (!obj)
        return LayoutRect();

    if (obj->node()) // If we are a continuation, we want to make sure to use the primary layoutObject.
        obj = obj->node()->layoutObject();

    // absoluteFocusRingBoundingBox will query the hierarchy below this element, which for large webpages can be very slow.
    // For a web area, which will have the most elements of any element, absoluteQuads should be used.
    // We should also use absoluteQuads for SVG elements, otherwise transforms won't be applied.

    LayoutRect result;
    if (obj->isText()) {
        Vector<FloatQuad> quads;
        toLayoutText(obj)->quads(quads, LayoutText::ClipToEllipsis, LayoutText::AbsoluteQuads);
        result = LayoutRect(boundingBoxForQuads(obj, quads));
    } else if (isWebArea() || obj->isSVGRoot()) {
        result = LayoutRect(obj->absoluteBoundingBoxRect());
    } else {
        result = LayoutRect(obj->absoluteElementBoundingBoxRect());
    }

    Document* document = this->getDocument();
    if (document && document->isSVGDocument())
        offsetBoundingBoxForRemoteSVGElement(result);
    if (document && document->frame() && document->frame()->pagePopupOwner()) {
        IntPoint popupOrigin = document->view()->contentsToScreen(IntRect()).location();
        IntPoint mainOrigin = axObjectCache().rootObject()->documentFrameView()->contentsToScreen(IntRect()).location();
        result.moveBy(IntPoint(popupOrigin - mainOrigin));
    }

    // The size of the web area should be the content size, not the clipped size.
    if (isWebArea() && obj->frame()->view())
        result.setSize(LayoutSize(obj->frame()->view()->contentsSize()));

    // Checkboxes and radio buttons include their labels as part of their rect.
    if (isCheckboxOrRadio() && isLabelableElement(obj->node())) {
        LabelsNodeList* labels = toLabelableElement(obj->node())->labels();
        if (labels) {
            for (unsigned labelIndex = 0; labelIndex < labels->length(); ++labelIndex) {
                AXObject* labelAXObject = axObjectCache().getOrCreate(labels->item(labelIndex));
                if (labelAXObject) {
                    LayoutRect labelRect = labelAXObject->elementRect();
                    result.unite(labelRect);
                }
            }
        }
    }

    return result;
}

} // namespace blink