AccessibilityObject.cpp   [plain text]

/*
 * Copyright (C) 2008, 2009, 2011 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 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
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#include "config.h"
#include "AccessibilityObject.h"

#include "AXObjectCache.h"
#include "AccessibilityRenderObject.h"
#include "AccessibilityScrollView.h"
#include "AccessibilityTable.h"
#include "DOMTokenList.h"
#include "Editor.h"
#include "EventHandler.h"
#include "FloatRect.h"
#include "FocusController.h"
#include "Frame.h"
#include "FrameLoader.h"
#include "FrameSelection.h"
#include "HTMLNames.h"
#include "HTMLParserIdioms.h"
#include "HitTestResult.h"
#include "LocalizedStrings.h"
#include "MainFrame.h"
#include "MathMLNames.h"
#include "NodeList.h"
#include "NodeTraversal.h"
#include "Page.h"
#include "RenderImage.h"
#include "RenderLayer.h"
#include "RenderListItem.h"
#include "RenderListMarker.h"
#include "RenderMenuList.h"
#include "RenderText.h"
#include "RenderTextControl.h"
#include "RenderTheme.h"
#include "RenderView.h"
#include "RenderWidget.h"
#include "RenderedPosition.h"
#include "Settings.h"
#include "TextCheckerClient.h"
#include "TextCheckingHelper.h"
#include "TextIterator.h"
#include "UserGestureIndicator.h"
#include "VisibleUnits.h"
#include "htmlediting.h"
#include <wtf/NeverDestroyed.h>
#include <wtf/StdLibExtras.h>
#include <wtf/text/StringBuilder.h>
#include <wtf/text/WTFString.h>
#include <wtf/unicode/CharacterNames.h>

namespace WebCore {

using namespace HTMLNames;

AccessibilityObject::AccessibilityObject()
    : m_id(0)
    , m_haveChildren(false)
    , m_role(UnknownRole)
    , m_lastKnownIsIgnoredValue(DefaultBehavior)
#if PLATFORM(GTK) || (PLATFORM(EFL) && HAVE(ACCESSIBILITY))
    , m_wrapper(0)
#endif
{
}

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

void AccessibilityObject::detach(AccessibilityDetachmentType detachmentType, AXObjectCache* cache)
{
    // Menu close events need to notify the platform. No element is used in the notification because it's a destruction event.
    if (detachmentType == ElementDestroyed && roleValue() == MenuRole && cache)
        cache->postNotification(nullptr, &cache->document(), AXObjectCache::AXMenuClosed);
    
    // Clear any children and call detachFromParent on them so that
    // no children are left with dangling pointers to their parent.
    clearChildren();

#if HAVE(ACCESSIBILITY)
    setWrapper(0);
#endif
}

bool AccessibilityObject::isDetached() const
{
#if HAVE(ACCESSIBILITY)
    return !wrapper();
#else
    return true;
#endif
}

bool AccessibilityObject::isAccessibilityObjectSearchMatchAtIndex(AccessibilityObject* axObject, AccessibilitySearchCriteria* criteria, size_t index)
{
    switch (criteria->searchKeys[index]) {
    // The AnyTypeSearchKey matches any non-null AccessibilityObject.
    case AnyTypeSearchKey:
        return true;
        
    case BlockquoteSameLevelSearchKey:
        return criteria->startObject
            && axObject->isBlockquote()
            && axObject->blockquoteLevel() == criteria->startObject->blockquoteLevel();
        
    case BlockquoteSearchKey:
        return axObject->isBlockquote();
        
    case BoldFontSearchKey:
        return axObject->hasBoldFont();
        
    case ButtonSearchKey:
        return axObject->isButton();
        
    case CheckBoxSearchKey:
        return axObject->isCheckbox();
        
    case ControlSearchKey:
        return axObject->isControl();
        
    case DifferentTypeSearchKey:
        return criteria->startObject
            && axObject->roleValue() != criteria->startObject->roleValue();
        
    case FontChangeSearchKey:
        return criteria->startObject
            && !axObject->hasSameFont(criteria->startObject->renderer());
        
    case FontColorChangeSearchKey:
        return criteria->startObject
            && !axObject->hasSameFontColor(criteria->startObject->renderer());
        
    case FrameSearchKey:
        return axObject->isWebArea();
        
    case GraphicSearchKey:
        return axObject->isImage();
        
    case HeadingLevel1SearchKey:
        return axObject->headingLevel() == 1;
        
    case HeadingLevel2SearchKey:
        return axObject->headingLevel() == 2;
        
    case HeadingLevel3SearchKey:
        return axObject->headingLevel() == 3;
        
    case HeadingLevel4SearchKey:
        return axObject->headingLevel() == 4;
        
    case HeadingLevel5SearchKey:
        return axObject->headingLevel() == 5;
        
    case HeadingLevel6SearchKey:
        return axObject->headingLevel() == 6;
        
    case HeadingSameLevelSearchKey:
        return criteria->startObject
            && axObject->isHeading()
            && axObject->headingLevel() == criteria->startObject->headingLevel();
        
    case HeadingSearchKey:
        return axObject->isHeading();
    
    case HighlightedSearchKey:
        return axObject->hasHighlighting();
            
    case ItalicFontSearchKey:
        return axObject->hasItalicFont();
        
    case LandmarkSearchKey:
        return axObject->isLandmark();
        
    case LinkSearchKey:
        return axObject->isLink();
        
    case ListSearchKey:
        return axObject->isList();
        
    case LiveRegionSearchKey:
        return axObject->supportsARIALiveRegion();
        
    case MisspelledWordSearchKey:
        return axObject->hasMisspelling();
        
    case OutlineSearchKey:
        return axObject->isTree();
        
    case PlainTextSearchKey:
        return axObject->hasPlainText();
        
    case RadioGroupSearchKey:
        return axObject->isRadioGroup();
        
    case SameTypeSearchKey:
        return criteria->startObject
            && axObject->roleValue() == criteria->startObject->roleValue();
        
    case StaticTextSearchKey:
        return axObject->isStaticText();
        
    case StyleChangeSearchKey:
        return criteria->startObject
            && !axObject->hasSameStyle(criteria->startObject->renderer());
        
    case TableSameLevelSearchKey:
        return criteria->startObject
            && axObject->isAccessibilityTable()
            && axObject->tableLevel() == criteria->startObject->tableLevel();
        
    case TableSearchKey:
        return axObject->isAccessibilityTable();
        
    case TextFieldSearchKey:
        return axObject->isTextControl();
        
    case UnderlineSearchKey:
        return axObject->hasUnderline();
        
    case UnvisitedLinkSearchKey:
        return axObject->isUnvisited();
        
    case VisitedLinkSearchKey:
        return axObject->isVisited();
        
    default:
        return false;
    }
}

bool AccessibilityObject::isAccessibilityObjectSearchMatch(AccessibilityObject* axObject, AccessibilitySearchCriteria* criteria)
{
    if (!axObject || !criteria)
        return false;
    
    size_t length = criteria->searchKeys.size();
    for (size_t i = 0; i < length; ++i) {
        if (isAccessibilityObjectSearchMatchAtIndex(axObject, criteria, i)) {
            if (criteria->visibleOnly && !axObject->isOnscreen())
                return false;
            return true;
        }
    }
    return false;
}

bool AccessibilityObject::isAccessibilityTextSearchMatch(AccessibilityObject* axObject, AccessibilitySearchCriteria* criteria)
{
    if (!axObject || !criteria)
        return false;
    
    return axObject->accessibilityObjectContainsText(&criteria->searchText);
}

bool AccessibilityObject::accessibilityObjectContainsText(String* text) const
{
    // If text is null or empty we return true.
    return !text
        || text->isEmpty()
        || title().contains(*text, false)
        || accessibilityDescription().contains(*text, false)
        || stringValue().contains(*text, false);
}

bool AccessibilityObject::isBlockquote() const
{
    return node() && node()->hasTagName(blockquoteTag);
}

bool AccessibilityObject::isTextControl() const
{
    switch (roleValue()) {
    case TextAreaRole:
    case TextFieldRole:
    case ComboBoxRole:
        return true;
    default:
        return false;
    }
}
    
bool AccessibilityObject::isARIATextControl() const
{
    return ariaRoleAttribute() == TextAreaRole || ariaRoleAttribute() == TextFieldRole;
}

bool AccessibilityObject::isLandmark() const
{
    AccessibilityRole role = roleValue();
    
    return role == LandmarkApplicationRole
        || role == LandmarkBannerRole
        || role == LandmarkComplementaryRole
        || role == LandmarkContentInfoRole
        || role == LandmarkMainRole
        || role == LandmarkNavigationRole
        || role == LandmarkSearchRole;
}

bool AccessibilityObject::hasMisspelling() const
{
    if (!node())
        return false;
    
    Frame* frame = node()->document().frame();
    if (!frame)
        return false;
    
    Editor& editor = frame->editor();
    
    TextCheckerClient* textChecker = editor.textChecker();
    if (!textChecker)
        return false;
    
    bool isMisspelled = false;

    if (unifiedTextCheckerEnabled(frame)) {
        Vector<TextCheckingResult> results;
        checkTextOfParagraph(*textChecker, stringValue(), TextCheckingTypeSpelling, results);
        if (!results.isEmpty())
            isMisspelled = true;
        return isMisspelled;
    }

    int misspellingLength = 0;
    int misspellingLocation = -1;
    textChecker->checkSpellingOfString(stringValue(), &misspellingLocation, &misspellingLength);
    if (misspellingLength || misspellingLocation != -1)
        isMisspelled = true;
    
    return isMisspelled;
}

int AccessibilityObject::blockquoteLevel() const
{
    int level = 0;
    for (Node* elementNode = node(); elementNode; elementNode = elementNode->parentNode()) {
        if (elementNode->hasTagName(blockquoteTag))
            ++level;
    }
    
    return level;
}

AccessibilityObject* AccessibilityObject::parentObjectUnignored() const
{
    AccessibilityObject* parent;
    for (parent = parentObject(); parent && parent->accessibilityIsIgnored(); parent = parent->parentObject()) {
    }
    
    return parent;
}

AccessibilityObject* AccessibilityObject::firstAccessibleObjectFromNode(const Node* node)
{
    if (!node)
        return 0;

    AXObjectCache* cache = node->document().axObjectCache();
    if (!cache)
        return nullptr;
    
    AccessibilityObject* accessibleObject = cache->getOrCreate(node->renderer());
    while (accessibleObject && accessibleObject->accessibilityIsIgnored()) {
        node = NodeTraversal::next(node);

        while (node && !node->renderer())
            node = NodeTraversal::nextSkippingChildren(node);

        if (!node)
            return 0;

        accessibleObject = cache->getOrCreate(node->renderer());
    }

    return accessibleObject;
}

static void appendAccessibilityObject(AccessibilityObject* object, AccessibilityObject::AccessibilityChildrenVector& results)
{
    // Find the next descendant of this attachment object so search can continue through frames.
    if (object->isAttachment()) {
        Widget* widget = object->widgetForAttachmentView();
        if (!widget || !widget->isFrameView())
            return;
        
        Document* doc = toFrameView(widget)->frame().document();
        if (!doc || !doc->hasLivingRenderTree())
            return;
        
        object = object->axObjectCache()->getOrCreate(doc);
    }

    if (object)
        results.append(object);
}
    
static void appendChildrenToArray(AccessibilityObject* object, bool isForward, AccessibilityObject* startObject, AccessibilityObject::AccessibilityChildrenVector& results)
{
    // A table's children includes elements whose own children are also the table's children (due to the way the Mac exposes tables).
    // The rows from the table should be queried, since those are direct descendants of the table, and they contain content.
    const auto& searchChildren = object->isAccessibilityTable() ? toAccessibilityTable(object)->rows() : object->children();

    size_t childrenSize = searchChildren.size();

    size_t startIndex = isForward ? childrenSize : 0;
    size_t endIndex = isForward ? 0 : childrenSize;

    size_t searchPosition = startObject ? searchChildren.find(startObject) : WTF::notFound;
    if (searchPosition != WTF::notFound) {
        if (isForward)
            endIndex = searchPosition + 1;
        else
            endIndex = searchPosition;
    }

    // This is broken into two statements so that it's easier read.
    if (isForward) {
        for (size_t i = startIndex; i > endIndex; i--)
            appendAccessibilityObject(searchChildren.at(i - 1).get(), results);
    } else {
        for (size_t i = startIndex; i < endIndex; i++)
            appendAccessibilityObject(searchChildren.at(i).get(), results);
    }
}

// Returns true if the number of results is now >= the number of results desired.
bool AccessibilityObject::objectMatchesSearchCriteriaWithResultLimit(AccessibilityObject* object, AccessibilitySearchCriteria* criteria, AccessibilityChildrenVector& results)
{
    if (isAccessibilityObjectSearchMatch(object, criteria) && isAccessibilityTextSearchMatch(object, criteria)) {
        results.append(object);
        
        // Enough results were found to stop searching.
        if (results.size() >= criteria->resultsLimit)
            return true;
    }
    
    return false;
}

void AccessibilityObject::findMatchingObjects(AccessibilitySearchCriteria* criteria, AccessibilityChildrenVector& results)
{
    ASSERT(criteria);
    
    if (!criteria)
        return;

    if (AXObjectCache* cache = axObjectCache())
        cache->startCachingComputedObjectAttributesUntilTreeMutates();

    // This search mechanism only searches the elements before/after the starting object.
    // It does this by stepping up the parent chain and at each level doing a DFS.
    
    // If there's no start object, it means we want to search everything.
    AccessibilityObject* startObject = criteria->startObject;
    if (!startObject)
        startObject = this;
    
    bool isForward = criteria->searchDirection == SearchDirectionNext;
    
    // The first iteration of the outer loop will examine the children of the start object for matches. However, when
    // iterating backwards, the start object children should not be considered, so the loop is skipped ahead. We make an
    // exception when no start object was specified because we want to search everything regardless of search direction.
    AccessibilityObject* previousObject = 0;
    if (!isForward && startObject != this) {
        previousObject = startObject;
        startObject = startObject->parentObjectUnignored();
    }
    
    // The outer loop steps up the parent chain each time (unignored is important here because otherwise elements would be searched twice)
    for (AccessibilityObject* stopSearchElement = parentObjectUnignored(); startObject != stopSearchElement; startObject = startObject->parentObjectUnignored()) {

        // Only append the children after/before the previous element, so that the search does not check elements that are 
        // already behind/ahead of start element.
        AccessibilityChildrenVector searchStack;
        if (!criteria->immediateDescendantsOnly || startObject == this)
            appendChildrenToArray(startObject, isForward, previousObject, searchStack);

        // This now does a DFS at the current level of the parent.
        while (!searchStack.isEmpty()) {
            AccessibilityObject* searchObject = searchStack.last().get();
            searchStack.removeLast();
            
            if (objectMatchesSearchCriteriaWithResultLimit(searchObject, criteria, results))
                break;
            
            if (!criteria->immediateDescendantsOnly)
                appendChildrenToArray(searchObject, isForward, 0, searchStack);
        }
        
        if (results.size() >= criteria->resultsLimit)
            break;

        // When moving backwards, the parent object needs to be checked, because technically it's "before" the starting element.
        if (!isForward && startObject != this && objectMatchesSearchCriteriaWithResultLimit(startObject, criteria, results))
            break;

        previousObject = startObject;
    }
}

// Returns the range that is fewer positions away from the reference range.
// NOTE: The after range is expected to ACTUALLY be after the reference range and the before
// range is expected to ACTUALLY be before. These are not checked for performance reasons.
static PassRefPtr<Range> rangeClosestToRange(Range* referenceRange, PassRefPtr<Range> afterRange, PassRefPtr<Range> beforeRange)
{
    ASSERT(referenceRange);
    ASSERT(!afterRange || afterRange->startPosition() > referenceRange->startPosition());
    ASSERT(!beforeRange || beforeRange->endPosition() < referenceRange->endPosition());
    
    if (!referenceRange || (!afterRange && !beforeRange))
        return nullptr;
    if (afterRange && !beforeRange)
        return afterRange;
    if (!afterRange && beforeRange)
        return beforeRange;
    
    unsigned positionsToAfterRange = Position::positionCountBetweenPositions(afterRange->startPosition(), referenceRange->startPosition());
    unsigned positionsToBeforeRange = Position::positionCountBetweenPositions(afterRange->endPosition(), referenceRange->endPosition());
    
    return positionsToAfterRange < positionsToBeforeRange ? afterRange : beforeRange;
}

PassRefPtr<Range> AccessibilityObject::rangeOfStringClosestToRangeInDirection(Range* referenceRange, AccessibilitySearchDirection searchDirection, Vector<String>& searchStrings) const
{
    Frame* frame = this->frame();
    if (!frame)
        return nullptr;
    
    if (!referenceRange)
        return nullptr;
    
    bool isBackwardSearch = searchDirection == SearchDirectionPrevious;
    FindOptions findOptions = AtWordStarts | CaseInsensitive | StartInSelection;
    if (isBackwardSearch)
        findOptions |= Backwards;
    
    RefPtr<Range> closestStringRange = nullptr;
    for (const auto& searchString : searchStrings) {
        if (RefPtr<Range> searchStringRange = frame->editor().rangeOfString(searchString, referenceRange, findOptions)) {
            if (!closestStringRange)
                closestStringRange = searchStringRange;
            else {
                // If searching backward, use the trailing range edges to correctly determine which
                // range is closest. Similarly, if searching forward, use the leading range edges.
                Position closestStringPosition = isBackwardSearch ? closestStringRange->endPosition() : closestStringRange->startPosition();
                Position searchStringPosition = isBackwardSearch ? searchStringRange->endPosition() : searchStringRange->startPosition();
                
                int closestPositionOffset = closestStringPosition.computeOffsetInContainerNode();
                int searchPositionOffset = searchStringPosition.computeOffsetInContainerNode();
                Node* closestContainerNode = closestStringPosition.containerNode();
                Node* searchContainerNode = searchStringPosition.containerNode();
                
                short result = Range::compareBoundaryPoints(closestContainerNode, closestPositionOffset, searchContainerNode, searchPositionOffset, ASSERT_NO_EXCEPTION);
                if ((!isBackwardSearch && result > 0) || (isBackwardSearch && result < 0))
                    closestStringRange = searchStringRange;
            }
        }
    }
    return closestStringRange;
}

// Returns the range of the entire document if there is no selection.
PassRefPtr<Range> AccessibilityObject::selectionRange() const
{
    Frame* frame = this->frame();
    if (!frame)
        return nullptr;
    
    const VisibleSelection& selection = frame->selection().selection();
    if (!selection.isNone())
        return selection.firstRange();
    
    return Range::create(*frame->document());
}

String AccessibilityObject::selectText(AccessibilitySelectTextCriteria* criteria)
{
    ASSERT(criteria);
    
    if (!criteria)
        return String();
    
    Frame* frame = this->frame();
    if (!frame)
        return String();
    
    AccessibilitySelectTextActivity& activity = criteria->activity;
    AccessibilitySelectTextAmbiguityResolution& ambiguityResolution = criteria->ambiguityResolution;
    String& replacementString = criteria->replacementString;
    Vector<String>& searchStrings = criteria->searchStrings;
    
    RefPtr<Range> selectedStringRange = selectionRange();
    
    RefPtr<Range> closestAfterStringRange = nullptr;
    RefPtr<Range> closestBeforeStringRange = nullptr;
    // Search forward if necessary.
    if (ambiguityResolution == ClosestAfterSelectionAmbiguityResolution || ambiguityResolution == ClosestToSelectionAmbiguityResolution)
        closestAfterStringRange = rangeOfStringClosestToRangeInDirection(selectedStringRange.get(), SearchDirectionNext, searchStrings);
    // Search backward if necessary.
    if (ambiguityResolution == ClosestBeforeSelectionAmbiguityResolution || ambiguityResolution == ClosestToSelectionAmbiguityResolution)
        closestBeforeStringRange = rangeOfStringClosestToRangeInDirection(selectedStringRange.get(), SearchDirectionPrevious, searchStrings);
    
    // Determine which candidate is closest to the selection and perform the activity.
    if (RefPtr<Range> closestStringRange = rangeClosestToRange(selectedStringRange.get(), closestAfterStringRange, closestBeforeStringRange)) {
        String closestString = closestStringRange->text();
        bool replaceSelection = false;
        if (frame->selection().setSelectedRange(closestStringRange.get(), DOWNSTREAM, true)) {
            switch (activity) {
            case FindAndCapitalize: {
                replacementString = closestString;
                makeCapitalized(&replacementString, 0);
                replaceSelection = true;
                break;
            }
            case FindAndUppercase:
                replacementString = closestString.upper();
                replaceSelection = true;
                break;
            case FindAndLowercase:
                replacementString = closestString.lower();
                replaceSelection = true;
                break;
            case FindAndReplaceActivity:
                replaceSelection = true;
                break;
            case FindAndSelectActivity:
                break;
            }
            
            if (replaceSelection)
                frame->editor().replaceSelectionWithText(replacementString, true, true);
            return closestString;
        }
    }
    
    return String();
}

bool AccessibilityObject::hasAttributesRequiredForInclusion() const
{
    // These checks are simplified in the interest of execution speed.
    if (!getAttribute(aria_helpAttr).isEmpty()
        || !getAttribute(aria_describedbyAttr).isEmpty()
        || !getAttribute(altAttr).isEmpty()
        || !getAttribute(titleAttr).isEmpty())
        return true;

#if ENABLE(MATHML)
    if (!getAttribute(MathMLNames::alttextAttr).isEmpty())
        return true;
#endif

    return false;
}

bool AccessibilityObject::isARIAInput(AccessibilityRole ariaRole)
{
    return ariaRole == RadioButtonRole || ariaRole == CheckBoxRole || ariaRole == TextFieldRole;
}    
    
bool AccessibilityObject::isARIAControl(AccessibilityRole ariaRole)
{
    return isARIAInput(ariaRole) || ariaRole == TextAreaRole || ariaRole == ButtonRole 
    || ariaRole == ComboBoxRole || ariaRole == SliderRole; 
}
    
bool AccessibilityObject::isRangeControl() const
{
    switch (roleValue()) {
    case ProgressIndicatorRole:
    case SliderRole:
    case ScrollBarRole:
    case SpinButtonRole:
        return true;
    default:
        return false;
    }
}

bool AccessibilityObject::isMeter() const
{
#if ENABLE(METER_ELEMENT)
    RenderObject* renderer = this->renderer();
    return renderer && renderer->isMeter();
#else
    return false;
#endif
}

IntPoint AccessibilityObject::clickPoint()
{
    LayoutRect rect = elementRect();
    return roundedIntPoint(LayoutPoint(rect.x() + rect.width() / 2, rect.y() + rect.height() / 2));
}

IntRect AccessibilityObject::boundingBoxForQuads(RenderObject* obj, const Vector<FloatQuad>& quads)
{
    ASSERT(obj);
    if (!obj)
        return IntRect();
    
    FloatRect result;
    for (const auto& quad : quads) {
        FloatRect r = quad.enclosingBoundingBox();
        if (!r.isEmpty()) {
            if (obj->style().hasAppearance())
                obj->theme().adjustRepaintRect(*obj, r);
            result.unite(r);
        }
    }
    return pixelSnappedIntRect(LayoutRect(result));
}
    
bool AccessibilityObject::press()
{
    // The presence of the actionElement will confirm whether we should even attempt a press.
    Element* actionElem = actionElement();
    if (!actionElem)
        return false;
    if (Frame* f = actionElem->document().frame())
        f->loader().resetMultipleFormSubmissionProtection();
    
    // Hit test at this location to determine if there is a sub-node element that should act
    // as the target of the action.
    Element* hitTestElement = nullptr;
    if (Document* document = this->document()) {
        RenderView* renderView = document->renderView();
        RenderLayer* layer = renderView->layer();
        
        HitTestRequest request(HitTestRequest::ReadOnly | HitTestRequest::Active | HitTestRequest::AccessibilityHitTest);
        HitTestResult hitTestResult = HitTestResult(clickPoint());
        layer->hitTest(request, hitTestResult);
        if (hitTestResult.innerNode()) {
            Node* innerNode = hitTestResult.innerNode()->deprecatedShadowAncestorNode();
            if (innerNode->isElementNode())
                hitTestElement = toElement(innerNode);
        }
    }
    
    
    // Prefer the actionElement instead of this node, if the actionElement is inside this node.
    Element* pressElement = this->element();
    if (!pressElement || actionElem->isDescendantOf(pressElement))
        pressElement = actionElem;
    
    // Prefer the hit test element, if it is inside the target element.
    if (hitTestElement && hitTestElement->isDescendantOf(pressElement))
        pressElement = hitTestElement;
    
    UserGestureIndicator gestureIndicator(DefinitelyProcessingUserGesture);
    
    bool dispatchedTouchEvent = dispatchTouchEvent();
    if (!dispatchedTouchEvent)
        pressElement->accessKeyAction(true);
    
    return true;
}
    
bool AccessibilityObject::dispatchTouchEvent()
{
    bool handled = false;
#if ENABLE(IOS_TOUCH_EVENTS)
    MainFrame* frame = mainFrame();
    if (!frame)
        return false;

    frame->eventHandler().dispatchSimulatedTouchEvent(clickPoint());
#endif
    return handled;
}

Frame* AccessibilityObject::frame() const
{
    Node* node = this->node();
    if (!node)
        return nullptr;
    
    return node->document().frame();
}

MainFrame* AccessibilityObject::mainFrame() const
{
    Document* document = topDocument();
    if (!document)
        return nullptr;
    
    Frame* frame = document->frame();
    if (!frame)
        return nullptr;
    
    return &frame->mainFrame();
}

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

String AccessibilityObject::language() const
{
    const AtomicString& lang = getAttribute(langAttr);
    if (!lang.isEmpty())
        return lang;

    AccessibilityObject* parent = parentObject();
    
    // as a last resort, fall back to the content language specified in the meta tag
    if (!parent) {
        Document* doc = document();
        if (doc)
            return doc->contentLanguage();
        return nullAtom;
    }
    
    return parent->language();
}
    
VisiblePositionRange AccessibilityObject::visiblePositionRangeForUnorderedPositions(const VisiblePosition& visiblePos1, const VisiblePosition& visiblePos2) const
{
    if (visiblePos1.isNull() || visiblePos2.isNull())
        return VisiblePositionRange();

    // If there's no common tree scope between positions, return early.
    if (!commonTreeScope(visiblePos1.deepEquivalent().deprecatedNode(), visiblePos2.deepEquivalent().deprecatedNode()))
        return VisiblePositionRange();
    
    VisiblePosition startPos;
    VisiblePosition endPos;
    bool alreadyInOrder;

    // upstream is ordered before downstream for the same position
    if (visiblePos1 == visiblePos2 && visiblePos2.affinity() == UPSTREAM)
        alreadyInOrder = false;

    // use selection order to see if the positions are in order
    else
        alreadyInOrder = VisibleSelection(visiblePos1, visiblePos2).isBaseFirst();

    if (alreadyInOrder) {
        startPos = visiblePos1;
        endPos = visiblePos2;
    } else {
        startPos = visiblePos2;
        endPos = visiblePos1;
    }

    return VisiblePositionRange(startPos, endPos);
}

VisiblePositionRange AccessibilityObject::positionOfLeftWord(const VisiblePosition& visiblePos) const
{
    VisiblePosition startPosition = startOfWord(visiblePos, LeftWordIfOnBoundary);
    VisiblePosition endPosition = endOfWord(startPosition);
    return VisiblePositionRange(startPosition, endPosition);
}

VisiblePositionRange AccessibilityObject::positionOfRightWord(const VisiblePosition& visiblePos) const
{
    VisiblePosition startPosition = startOfWord(visiblePos, RightWordIfOnBoundary);
    VisiblePosition endPosition = endOfWord(startPosition);
    return VisiblePositionRange(startPosition, endPosition);
}

static VisiblePosition updateAXLineStartForVisiblePosition(const VisiblePosition& visiblePosition)
{
    // A line in the accessibility sense should include floating objects, such as aligned image, as part of a line.
    // So let's update the position to include that.
    VisiblePosition tempPosition;
    VisiblePosition startPosition = visiblePosition;
    while (true) {
        tempPosition = startPosition.previous();
        if (tempPosition.isNull())
            break;
        Position p = tempPosition.deepEquivalent();
        RenderObject* renderer = p.deprecatedNode()->renderer();
        if (!renderer || (renderer->isRenderBlock() && !p.deprecatedEditingOffset()))
            break;
        if (!RenderedPosition(tempPosition).isNull())
            break;
        startPosition = tempPosition;
    }

    return startPosition;
}

VisiblePositionRange AccessibilityObject::leftLineVisiblePositionRange(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePositionRange();

    // make a caret selection for the position before marker position (to make sure
    // we move off of a line start)
    VisiblePosition prevVisiblePos = visiblePos.previous();
    if (prevVisiblePos.isNull())
        return VisiblePositionRange();

    VisiblePosition startPosition = startOfLine(prevVisiblePos);

    // keep searching for a valid line start position.  Unless the VisiblePosition is at the very beginning, there should
    // always be a valid line range.  However, startOfLine will return null for position next to a floating object,
    // since floating object doesn't really belong to any line.
    // This check will reposition the marker before the floating object, to ensure we get a line start.
    if (startPosition.isNull()) {
        while (startPosition.isNull() && prevVisiblePos.isNotNull()) {
            prevVisiblePos = prevVisiblePos.previous();
            startPosition = startOfLine(prevVisiblePos);
        }
    } else
        startPosition = updateAXLineStartForVisiblePosition(startPosition);

    VisiblePosition endPosition = endOfLine(prevVisiblePos);
    return VisiblePositionRange(startPosition, endPosition);
}

VisiblePositionRange AccessibilityObject::rightLineVisiblePositionRange(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePositionRange();

    // make sure we move off of a line end
    VisiblePosition nextVisiblePos = visiblePos.next();
    if (nextVisiblePos.isNull())
        return VisiblePositionRange();

    VisiblePosition startPosition = startOfLine(nextVisiblePos);

    // fetch for a valid line start position
    if (startPosition.isNull()) {
        startPosition = visiblePos;
        nextVisiblePos = nextVisiblePos.next();
    } else
        startPosition = updateAXLineStartForVisiblePosition(startPosition);

    VisiblePosition endPosition = endOfLine(nextVisiblePos);

    // as long as the position hasn't reached the end of the doc,  keep searching for a valid line end position
    // Unless the VisiblePosition is at the very end, there should always be a valid line range.  However, endOfLine will
    // return null for position by a floating object, since floating object doesn't really belong to any line.
    // This check will reposition the marker after the floating object, to ensure we get a line end.
    while (endPosition.isNull() && nextVisiblePos.isNotNull()) {
        nextVisiblePos = nextVisiblePos.next();
        endPosition = endOfLine(nextVisiblePos);
    }

    return VisiblePositionRange(startPosition, endPosition);
}

VisiblePositionRange AccessibilityObject::sentenceForPosition(const VisiblePosition& visiblePos) const
{
    // FIXME: FO 2 IMPLEMENT (currently returns incorrect answer)
    // Related? <rdar://problem/3927736> Text selection broken in 8A336
    VisiblePosition startPosition = startOfSentence(visiblePos);
    VisiblePosition endPosition = endOfSentence(startPosition);
    return VisiblePositionRange(startPosition, endPosition);
}

VisiblePositionRange AccessibilityObject::paragraphForPosition(const VisiblePosition& visiblePos) const
{
    VisiblePosition startPosition = startOfParagraph(visiblePos);
    VisiblePosition endPosition = endOfParagraph(startPosition);
    return VisiblePositionRange(startPosition, endPosition);
}

static VisiblePosition startOfStyleRange(const VisiblePosition& visiblePos)
{
    RenderObject* renderer = visiblePos.deepEquivalent().deprecatedNode()->renderer();
    RenderObject* startRenderer = renderer;
    RenderStyle* style = &renderer->style();

    // traverse backward by renderer to look for style change
    for (RenderObject* r = renderer->previousInPreOrder(); r; r = r->previousInPreOrder()) {
        // skip non-leaf nodes
        if (r->firstChildSlow())
            continue;

        // stop at style change
        if (&r->style() != style)
            break;

        // remember match
        startRenderer = r;
    }

    return firstPositionInOrBeforeNode(startRenderer->node());
}

static VisiblePosition endOfStyleRange(const VisiblePosition& visiblePos)
{
    RenderObject* renderer = visiblePos.deepEquivalent().deprecatedNode()->renderer();
    RenderObject* endRenderer = renderer;
    const RenderStyle& style = renderer->style();

    // traverse forward by renderer to look for style change
    for (RenderObject* r = renderer->nextInPreOrder(); r; r = r->nextInPreOrder()) {
        // skip non-leaf nodes
        if (r->firstChildSlow())
            continue;

        // stop at style change
        if (&r->style() != &style)
            break;

        // remember match
        endRenderer = r;
    }

    return lastPositionInOrAfterNode(endRenderer->node());
}

VisiblePositionRange AccessibilityObject::styleRangeForPosition(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePositionRange();

    return VisiblePositionRange(startOfStyleRange(visiblePos), endOfStyleRange(visiblePos));
}

// NOTE: Consider providing this utility method as AX API
VisiblePositionRange AccessibilityObject::visiblePositionRangeForRange(const PlainTextRange& range) const
{
    unsigned textLength = getLengthForTextRange();
    if (range.start + range.length > textLength)
        return VisiblePositionRange();

    VisiblePosition startPosition = visiblePositionForIndex(range.start);
    startPosition.setAffinity(DOWNSTREAM);
    VisiblePosition endPosition = visiblePositionForIndex(range.start + range.length);
    return VisiblePositionRange(startPosition, endPosition);
}

VisiblePositionRange AccessibilityObject::lineRangeForPosition(const VisiblePosition& visiblePosition) const
{
    VisiblePosition startPosition = startOfLine(visiblePosition);
    VisiblePosition endPosition = endOfLine(visiblePosition);
    return VisiblePositionRange(startPosition, endPosition);
}

static bool replacedNodeNeedsCharacter(Node* replacedNode)
{
    // we should always be given a rendered node and a replaced node, but be safe
    // replaced nodes are either attachments (widgets) or images
    if (!replacedNode || !isRendererReplacedElement(replacedNode->renderer()) || replacedNode->isTextNode())
        return false;

    // create an AX object, but skip it if it is not supposed to be seen
    AccessibilityObject* object = replacedNode->renderer()->document().axObjectCache()->getOrCreate(replacedNode);
    if (object->accessibilityIsIgnored())
        return false;

    return true;
}

// Finds a RenderListItem parent give a node.
static RenderListItem* renderListItemContainerForNode(Node* node)
{
    for (; node; node = node->parentNode()) {
        RenderBoxModelObject* renderer = node->renderBoxModelObject();
        if (renderer && renderer->isListItem())
            return toRenderListItem(renderer);
    }
    return 0;
}
    
// Returns the text associated with a list marker if this node is contained within a list item.
String AccessibilityObject::listMarkerTextForNodeAndPosition(Node* node, const VisiblePosition& visiblePositionStart) const
{
    // If the range does not contain the start of the line, the list marker text should not be included.
    if (!isStartOfLine(visiblePositionStart))
        return String();

    RenderListItem* listItem = renderListItemContainerForNode(node);
    if (!listItem)
        return String();
        
    // If this is in a list item, we need to manually add the text for the list marker 
    // because a RenderListMarker does not have a Node equivalent and thus does not appear
    // when iterating text.
    return listItem->markerTextWithSuffix();
}

String AccessibilityObject::stringForVisiblePositionRange(const VisiblePositionRange& visiblePositionRange) const
{
    if (visiblePositionRange.isNull())
        return String();

    StringBuilder builder;
    RefPtr<Range> range = makeRange(visiblePositionRange.start, visiblePositionRange.end);
    for (TextIterator it(range.get()); !it.atEnd(); it.advance()) {
        // non-zero length means textual node, zero length means replaced node (AKA "attachments" in AX)
        if (it.text().length()) {
            // Add a textual representation for list marker text.
            builder.append(listMarkerTextForNodeAndPosition(it.node(), visiblePositionRange.start));
            it.appendTextToStringBuilder(builder);
        } else {
            // locate the node and starting offset for this replaced range
            Node* node = it.range()->startContainer();
            ASSERT(node == it.range()->endContainer());
            int offset = it.range()->startOffset();
            if (replacedNodeNeedsCharacter(node->childNode(offset)))
                builder.append(objectReplacementCharacter);
        }
    }

    return builder.toString();
}

int AccessibilityObject::lengthForVisiblePositionRange(const VisiblePositionRange& visiblePositionRange) const
{
    // FIXME: Multi-byte support
    if (visiblePositionRange.isNull())
        return -1;
    
    int length = 0;
    RefPtr<Range> range = makeRange(visiblePositionRange.start, visiblePositionRange.end);
    for (TextIterator it(range.get()); !it.atEnd(); it.advance()) {
        // non-zero length means textual node, zero length means replaced node (AKA "attachments" in AX)
        if (it.text().length())
            length += it.text().length();
        else {
            // locate the node and starting offset for this replaced range
            int exception = 0;
            Node* node = it.range()->startContainer(exception);
            ASSERT(node == it.range()->endContainer(exception));
            int offset = it.range()->startOffset(exception);

            if (replacedNodeNeedsCharacter(node->childNode(offset)))
                length++;
        }
    }
    
    return length;
}

VisiblePosition AccessibilityObject::visiblePositionForBounds(const IntRect& rect, AccessibilityVisiblePositionForBounds visiblePositionForBounds) const
{
    if (rect.isEmpty())
        return VisiblePosition();
    
    MainFrame* mainFrame = this->mainFrame();
    if (!mainFrame)
        return VisiblePosition();
    
    // FIXME: Add support for right-to-left languages.
    IntPoint corner = (visiblePositionForBounds == FirstVisiblePositionForBounds) ? rect.minXMinYCorner() : rect.maxXMaxYCorner();
    VisiblePosition position = mainFrame->visiblePositionForPoint(corner);
    
    if (rect.contains(position.absoluteCaretBounds().center()))
        return position;
    
    // If the initial position is located outside the bounds adjust it incrementally as needed.
    VisiblePosition nextPosition = position.next();
    VisiblePosition previousPosition = position.previous();
    while (nextPosition.isNotNull() || previousPosition.isNotNull()) {
        if (rect.contains(nextPosition.absoluteCaretBounds().center()))
            return nextPosition;
        if (rect.contains(previousPosition.absoluteCaretBounds().center()))
            return previousPosition;
        
        nextPosition = nextPosition.next();
        previousPosition = previousPosition.previous();
    }
    
    return VisiblePosition();
}

VisiblePosition AccessibilityObject::nextWordEnd(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePosition();

    // make sure we move off of a word end
    VisiblePosition nextVisiblePos = visiblePos.next();
    if (nextVisiblePos.isNull())
        return VisiblePosition();

    return endOfWord(nextVisiblePos, LeftWordIfOnBoundary);
}

VisiblePosition AccessibilityObject::previousWordStart(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePosition();

    // make sure we move off of a word start
    VisiblePosition prevVisiblePos = visiblePos.previous();
    if (prevVisiblePos.isNull())
        return VisiblePosition();

    return startOfWord(prevVisiblePos, RightWordIfOnBoundary);
}

VisiblePosition AccessibilityObject::nextLineEndPosition(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePosition();

    // to make sure we move off of a line end
    VisiblePosition nextVisiblePos = visiblePos.next();
    if (nextVisiblePos.isNull())
        return VisiblePosition();

    VisiblePosition endPosition = endOfLine(nextVisiblePos);

    // as long as the position hasn't reached the end of the doc,  keep searching for a valid line end position
    // There are cases like when the position is next to a floating object that'll return null for end of line. This code will avoid returning null.
    while (endPosition.isNull() && nextVisiblePos.isNotNull()) {
        nextVisiblePos = nextVisiblePos.next();
        endPosition = endOfLine(nextVisiblePos);
    }

    return endPosition;
}

VisiblePosition AccessibilityObject::previousLineStartPosition(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePosition();

    // make sure we move off of a line start
    VisiblePosition prevVisiblePos = visiblePos.previous();
    if (prevVisiblePos.isNull())
        return VisiblePosition();

    VisiblePosition startPosition = startOfLine(prevVisiblePos);

    // as long as the position hasn't reached the beginning of the doc,  keep searching for a valid line start position
    // There are cases like when the position is next to a floating object that'll return null for start of line. This code will avoid returning null.
    if (startPosition.isNull()) {
        while (startPosition.isNull() && prevVisiblePos.isNotNull()) {
            prevVisiblePos = prevVisiblePos.previous();
            startPosition = startOfLine(prevVisiblePos);
        }
    } else
        startPosition = updateAXLineStartForVisiblePosition(startPosition);

    return startPosition;
}

VisiblePosition AccessibilityObject::nextSentenceEndPosition(const VisiblePosition& visiblePos) const
{
    // FIXME: FO 2 IMPLEMENT (currently returns incorrect answer)
    // Related? <rdar://problem/3927736> Text selection broken in 8A336
    if (visiblePos.isNull())
        return VisiblePosition();

    // make sure we move off of a sentence end
    VisiblePosition nextVisiblePos = visiblePos.next();
    if (nextVisiblePos.isNull())
        return VisiblePosition();

    // an empty line is considered a sentence. If it's skipped, then the sentence parser will not
    // see this empty line.  Instead, return the end position of the empty line.
    VisiblePosition endPosition;
    
    String lineString = plainText(makeRange(startOfLine(nextVisiblePos), endOfLine(nextVisiblePos)).get());
    if (lineString.isEmpty())
        endPosition = nextVisiblePos;
    else
        endPosition = endOfSentence(nextVisiblePos);

    return endPosition;
}

VisiblePosition AccessibilityObject::previousSentenceStartPosition(const VisiblePosition& visiblePos) const
{
    // FIXME: FO 2 IMPLEMENT (currently returns incorrect answer)
    // Related? <rdar://problem/3927736> Text selection broken in 8A336
    if (visiblePos.isNull())
        return VisiblePosition();

    // make sure we move off of a sentence start
    VisiblePosition previousVisiblePos = visiblePos.previous();
    if (previousVisiblePos.isNull())
        return VisiblePosition();

    // treat empty line as a separate sentence.
    VisiblePosition startPosition;
    
    String lineString = plainText(makeRange(startOfLine(previousVisiblePos), endOfLine(previousVisiblePos)).get());
    if (lineString.isEmpty())
        startPosition = previousVisiblePos;
    else
        startPosition = startOfSentence(previousVisiblePos);

    return startPosition;
}

VisiblePosition AccessibilityObject::nextParagraphEndPosition(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePosition();

    // make sure we move off of a paragraph end
    VisiblePosition nextPos = visiblePos.next();
    if (nextPos.isNull())
        return VisiblePosition();

    return endOfParagraph(nextPos);
}

VisiblePosition AccessibilityObject::previousParagraphStartPosition(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return VisiblePosition();

    // make sure we move off of a paragraph start
    VisiblePosition previousPos = visiblePos.previous();
    if (previousPos.isNull())
        return VisiblePosition();

    return startOfParagraph(previousPos);
}

AccessibilityObject* AccessibilityObject::accessibilityObjectForPosition(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull())
        return 0;

    RenderObject* obj = visiblePos.deepEquivalent().deprecatedNode()->renderer();
    if (!obj)
        return 0;

    return obj->document().axObjectCache()->getOrCreate(obj);
}
    
// If you call node->hasEditableStyle() since that will return true if an ancestor is editable.
// This only returns true if this is the element that actually has the contentEditable attribute set.
bool AccessibilityObject::hasContentEditableAttributeSet() const
{
    return contentEditableAttributeIsEnabled(element());
}

bool AccessibilityObject::contentEditableAttributeIsEnabled(Element* element)
{
    if (!element)
        return false;
    
    if (!element->hasAttribute(contenteditableAttr))
        return false;
    
    const AtomicString& contentEditableValue = element->fastGetAttribute(contenteditableAttr);
    // Both "true" (case-insensitive) and the empty string count as true.
    return contentEditableValue.isEmpty() || equalIgnoringCase(contentEditableValue, "true");
}
    
#if HAVE(ACCESSIBILITY)
int AccessibilityObject::lineForPosition(const VisiblePosition& visiblePos) const
{
    if (visiblePos.isNull() || !node())
        return -1;

    // If the position is not in the same editable region as this AX object, return -1.
    Node* containerNode = visiblePos.deepEquivalent().containerNode();
    if (!containerNode->containsIncludingShadowDOM(node()) && !node()->containsIncludingShadowDOM(containerNode))
        return -1;

    int lineCount = -1;
    VisiblePosition currentVisiblePos = visiblePos;
    VisiblePosition savedVisiblePos;

    // move up until we get to the top
    // FIXME: This only takes us to the top of the rootEditableElement, not the top of the
    // top document.
    do {
        savedVisiblePos = currentVisiblePos;
        VisiblePosition prevVisiblePos = previousLinePosition(currentVisiblePos, 0, HasEditableAXRole);
        currentVisiblePos = prevVisiblePos;
        ++lineCount;
    }  while (currentVisiblePos.isNotNull() && !(inSameLine(currentVisiblePos, savedVisiblePos)));

    return lineCount;
}
#endif

// NOTE: Consider providing this utility method as AX API
PlainTextRange AccessibilityObject::plainTextRangeForVisiblePositionRange(const VisiblePositionRange& positionRange) const
{
    int index1 = index(positionRange.start);
    int index2 = index(positionRange.end);
    if (index1 < 0 || index2 < 0 || index1 > index2)
        return PlainTextRange();

    return PlainTextRange(index1, index2 - index1);
}

// The composed character range in the text associated with this accessibility object that
// is specified by the given screen coordinates. This parameterized attribute returns the
// complete range of characters (including surrogate pairs of multi-byte glyphs) at the given
// screen coordinates.
// NOTE: This varies from AppKit when the point is below the last line. AppKit returns an
// an error in that case. We return textControl->text().length(), 1. Does this matter?
PlainTextRange AccessibilityObject::doAXRangeForPosition(const IntPoint& point) const
{
    int i = index(visiblePositionForPoint(point));
    if (i < 0)
        return PlainTextRange();

    return PlainTextRange(i, 1);
}

// Given a character index, the range of text associated with this accessibility object
// over which the style in effect at that character index applies.
PlainTextRange AccessibilityObject::doAXStyleRangeForIndex(unsigned index) const
{
    VisiblePositionRange range = styleRangeForPosition(visiblePositionForIndex(index, false));
    return plainTextRangeForVisiblePositionRange(range);
}

// Given an indexed character, the line number of the text associated with this accessibility
// object that contains the character.
unsigned AccessibilityObject::doAXLineForIndex(unsigned index)
{
    return lineForPosition(visiblePositionForIndex(index, false));
}

#if HAVE(ACCESSIBILITY)
void AccessibilityObject::updateBackingStore()
{
    // Updating the layout may delete this object.
    RefPtr<AccessibilityObject> protector(this);

    if (Document* document = this->document()) {
        if (!document->view()->isInLayout())
            document->updateLayoutIgnorePendingStylesheets();
    }
    
    updateChildrenIfNecessary();
}
#endif
    
ScrollView* AccessibilityObject::scrollViewAncestor() const
{
    for (const AccessibilityObject* scrollParent = this; scrollParent; scrollParent = scrollParent->parentObject()) {
        if (scrollParent->isAccessibilityScrollView())
            return toAccessibilityScrollView(scrollParent)->scrollView();
    }
    
    return nullptr;
}
    
Document* AccessibilityObject::document() const
{
    FrameView* frameView = documentFrameView();
    if (!frameView)
        return 0;
    
    return frameView->frame().document();
}
    
Page* AccessibilityObject::page() const
{
    Document* document = this->document();
    if (!document)
        return 0;
    return document->page();
}

FrameView* AccessibilityObject::documentFrameView() const 
{ 
    const AccessibilityObject* object = this;
    while (object && !object->isAccessibilityRenderObject()) 
        object = object->parentObject();
        
    if (!object)
        return 0;

    return object->documentFrameView();
}

#if HAVE(ACCESSIBILITY)
const AccessibilityObject::AccessibilityChildrenVector& AccessibilityObject::children(bool updateChildrenIfNeeded)
{
    if (updateChildrenIfNeeded)
        updateChildrenIfNecessary();

    return m_children;
}
#endif

void AccessibilityObject::updateChildrenIfNecessary()
{
    if (!hasChildren()) {
        // Enable the cache in case we end up adding a lot of children, we don't want to recompute axIsIgnored each time.
        AXAttributeCacheEnabler enableCache(axObjectCache());
        addChildren();
    }
}
    
void AccessibilityObject::clearChildren()
{
    // Some objects have weak pointers to their parents and those associations need to be detached.
    for (const auto& child : m_children)
        child->detachFromParent();
    
    m_children.clear();
    m_haveChildren = false;
}

AccessibilityObject* AccessibilityObject::anchorElementForNode(Node* node)
{
    RenderObject* obj = node->renderer();
    if (!obj)
        return 0;
    
    RefPtr<AccessibilityObject> axObj = obj->document().axObjectCache()->getOrCreate(obj);
    Element* anchor = axObj->anchorElement();
    if (!anchor)
        return 0;
    
    RenderObject* anchorRenderer = anchor->renderer();
    if (!anchorRenderer)
        return 0;
    
    return anchorRenderer->document().axObjectCache()->getOrCreate(anchorRenderer);
}

AccessibilityObject* AccessibilityObject::headingElementForNode(Node* node)
{
    if (!node)
        return 0;
    
    RenderObject* renderObject = node->renderer();
    if (!renderObject)
        return 0;
    
    AccessibilityObject* axObject = renderObject->document().axObjectCache()->getOrCreate(renderObject);
    for (; axObject && axObject->roleValue() != HeadingRole; axObject = axObject->parentObject()) { }
    
    return axObject;
}

void AccessibilityObject::ariaTreeRows(AccessibilityChildrenVector& result)
{
    for (const auto& child : children()) {
        // Add tree items as the rows.
        if (child->roleValue() == TreeItemRole)
            result.append(child);

        // Now see if this item also has rows hiding inside of it.
        child->ariaTreeRows(result);
    }
}
    
void AccessibilityObject::ariaTreeItemContent(AccessibilityChildrenVector& result)
{
    // The ARIA tree item content are the item that are not other tree items or their containing groups.
    for (const auto& child : children()) {
        AccessibilityRole role = child->roleValue();
        if (role == TreeItemRole || role == GroupRole)
            continue;
        
        result.append(child);
    }
}

void AccessibilityObject::ariaTreeItemDisclosedRows(AccessibilityChildrenVector& result)
{
    for (const auto& obj : children()) {
        // Add tree items as the rows.
        if (obj->roleValue() == TreeItemRole)
            result.append(obj);
        // If it's not a tree item, then descend into the group to find more tree items.
        else 
            obj->ariaTreeRows(result);
    }    
}
    
const String AccessibilityObject::defaultLiveRegionStatusForRole(AccessibilityRole role)
{
    switch (role) {
    case ApplicationAlertDialogRole:
    case ApplicationAlertRole:
        return ASCIILiteral("assertive");
    case ApplicationLogRole:
    case ApplicationStatusRole:
        return ASCIILiteral("polite");
    case ApplicationTimerRole:
    case ApplicationMarqueeRole:
        return ASCIILiteral("off");
    default:
        return nullAtom;
    }
}
    
#if HAVE(ACCESSIBILITY)
const String& AccessibilityObject::actionVerb() const
{
#if !PLATFORM(IOS)
    // FIXME: Need to add verbs for select elements.
    static NeverDestroyed<const String> buttonAction(AXButtonActionVerb());
    static NeverDestroyed<const String> textFieldAction(AXTextFieldActionVerb());
    static NeverDestroyed<const String> radioButtonAction(AXRadioButtonActionVerb());
    static NeverDestroyed<const String> checkedCheckBoxAction(AXCheckedCheckBoxActionVerb());
    static NeverDestroyed<const String> uncheckedCheckBoxAction(AXUncheckedCheckBoxActionVerb());
    static NeverDestroyed<const String> linkAction(AXLinkActionVerb());
    static NeverDestroyed<const String> menuListAction(AXMenuListActionVerb());
    static NeverDestroyed<const String> menuListPopupAction(AXMenuListPopupActionVerb());
    static NeverDestroyed<const String> listItemAction(AXListItemActionVerb());

    switch (roleValue()) {
    case ButtonRole:
    case ToggleButtonRole:
        return buttonAction;
    case TextFieldRole:
    case TextAreaRole:
        return textFieldAction;
    case RadioButtonRole:
        return radioButtonAction;
    case CheckBoxRole:
        return isChecked() ? checkedCheckBoxAction : uncheckedCheckBoxAction;
    case LinkRole:
    case WebCoreLinkRole:
        return linkAction;
    case PopUpButtonRole:
        return menuListAction;
    case MenuListPopupRole:
        return menuListPopupAction;
    case ListItemRole:
        return listItemAction;
    default:
        return nullAtom;
    }
#else
    return nullAtom;
#endif
}
#endif

bool AccessibilityObject::ariaIsMultiline() const
{
    return equalIgnoringCase(getAttribute(aria_multilineAttr), "true");
}

String AccessibilityObject::invalidStatus() const
{
    String grammarValue = ASCIILiteral("grammar");
    String falseValue = ASCIILiteral("false");
    String spellingValue = ASCIILiteral("spelling");
    String trueValue = ASCIILiteral("true");
    String undefinedValue = ASCIILiteral("undefined");

    // aria-invalid can return false (default), grammar, spelling, or true.
    String ariaInvalid = stripLeadingAndTrailingHTMLSpaces(getAttribute(aria_invalidAttr));
    
    // If "false", "undefined" [sic, string value], empty, or missing, return "false".
    if (ariaInvalid.isEmpty() || ariaInvalid == falseValue || ariaInvalid == undefinedValue)
        return falseValue;
    // Besides true/false/undefined, the only tokens defined by WAI-ARIA 1.0...
    // ...for @aria-invalid are "grammar" and "spelling".
    if (ariaInvalid == grammarValue)
        return grammarValue;
    if (ariaInvalid == spellingValue)
        return spellingValue;
    // Any other non empty string should be treated as "true".
    return trueValue;
}
 
bool AccessibilityObject::hasTagName(const QualifiedName& tagName) const
{
    Node* node = this->node();
    return node && node->isElementNode() && toElement(*node).hasTagName(tagName);
}
    
bool AccessibilityObject::hasAttribute(const QualifiedName& attribute) const
{
    Node* elementNode = node();
    if (!elementNode)
        return false;
    
    if (!elementNode->isElementNode())
        return false;
    
    Element* element = toElement(elementNode);
    return element->fastHasAttribute(attribute);
}
    
const AtomicString& AccessibilityObject::getAttribute(const QualifiedName& attribute) const
{
    if (Element* element = this->element())
        return element->fastGetAttribute(attribute);
    return nullAtom;
}
    
// Lacking concrete evidence of orientation, horizontal means width > height. vertical is height > width;
AccessibilityOrientation AccessibilityObject::orientation() const
{
    LayoutRect bounds = elementRect();
    if (bounds.size().width() > bounds.size().height())
        return AccessibilityOrientationHorizontal;
    if (bounds.size().height() > bounds.size().width())
        return AccessibilityOrientationVertical;

    // A tie goes to horizontal.
    return AccessibilityOrientationHorizontal;
}    

bool AccessibilityObject::isDescendantOfObject(const AccessibilityObject* axObject) const
{
    if (!axObject || !axObject->hasChildren())
        return false;

    for (const AccessibilityObject* parent = parentObject(); parent; parent = parent->parentObject()) {
        if (parent == axObject)
            return true;
    }
    return false;
}

bool AccessibilityObject::isAncestorOfObject(const AccessibilityObject* axObject) const
{
    if (!axObject)
        return false;

    return this == axObject || axObject->isDescendantOfObject(this);
}

AccessibilityObject* AccessibilityObject::firstAnonymousBlockChild() const
{
    for (AccessibilityObject* child = firstChild(); child; child = child->nextSibling()) {
        if (child->renderer() && child->renderer()->isAnonymousBlock())
            return child;
    }
    return 0;
}

typedef HashMap<String, AccessibilityRole, CaseFoldingHash> ARIARoleMap;
typedef HashMap<AccessibilityRole, String, DefaultHash<int>::Hash, WTF::UnsignedWithZeroKeyHashTraits<int>> ARIAReverseRoleMap;

static ARIARoleMap* gAriaRoleMap = nullptr;
static ARIAReverseRoleMap* gAriaReverseRoleMap = nullptr;

struct RoleEntry {
    String ariaRole;
    AccessibilityRole webcoreRole;
};

static void initializeRoleMap()
{
    if (gAriaRoleMap)
        return;
    ASSERT(!gAriaReverseRoleMap);

    const RoleEntry roles[] = {
        { "alert", ApplicationAlertRole },
        { "alertdialog", ApplicationAlertDialogRole },
        { "application", LandmarkApplicationRole },
        { "article", DocumentArticleRole },
        { "banner", LandmarkBannerRole },
        { "button", ButtonRole },
        { "checkbox", CheckBoxRole },
        { "complementary", LandmarkComplementaryRole },
        { "contentinfo", LandmarkContentInfoRole },
        { "dialog", ApplicationDialogRole },
        { "directory", DirectoryRole },
        { "grid", TableRole },
        { "gridcell", CellRole },
        { "columnheader", ColumnHeaderRole },
        { "combobox", ComboBoxRole },
        { "definition", DefinitionRole },
        { "document", DocumentRole },
        { "rowheader", RowHeaderRole },
        { "group", GroupRole },
        { "heading", HeadingRole },
        { "img", ImageRole },
        { "link", WebCoreLinkRole },
        { "list", ListRole },        
        { "listitem", ListItemRole },        
        { "listbox", ListBoxRole },
        { "log", ApplicationLogRole },
        // "option" isn't here because it may map to different roles depending on the parent element's role
        { "main", LandmarkMainRole },
        { "marquee", ApplicationMarqueeRole },
        { "math", DocumentMathRole },
        { "menu", MenuRole },
        { "menubar", MenuBarRole },
        { "menuitem", MenuItemRole },
        { "menuitemcheckbox", MenuItemCheckboxRole },
        { "menuitemradio", MenuItemRadioRole },
        { "none", PresentationalRole },
        { "note", DocumentNoteRole },
        { "navigation", LandmarkNavigationRole },
        { "option", ListBoxOptionRole },
        { "presentation", PresentationalRole },
        { "progressbar", ProgressIndicatorRole },
        { "radio", RadioButtonRole },
        { "radiogroup", RadioGroupRole },
        { "region", DocumentRegionRole },
        { "row", RowRole },
        { "scrollbar", ScrollBarRole },
        { "search", LandmarkSearchRole },
        { "separator", SplitterRole },
        { "slider", SliderRole },
        { "spinbutton", SpinButtonRole },
        { "status", ApplicationStatusRole },
        { "tab", TabRole },
        { "tablist", TabListRole },
        { "tabpanel", TabPanelRole },
        { "text", StaticTextRole },
        { "textbox", TextAreaRole },
        { "timer", ApplicationTimerRole },
        { "toolbar", ToolbarRole },
        { "tooltip", UserInterfaceTooltipRole },
        { "tree", TreeRole },
        { "treegrid", TreeGridRole },
        { "treeitem", TreeItemRole }
    };

    gAriaRoleMap = new ARIARoleMap;
    gAriaReverseRoleMap = new ARIAReverseRoleMap;
    size_t roleLength = WTF_ARRAY_LENGTH(roles);
    for (size_t i = 0; i < roleLength; ++i) {
        gAriaRoleMap->set(roles[i].ariaRole, roles[i].webcoreRole);
        gAriaReverseRoleMap->set(roles[i].webcoreRole, roles[i].ariaRole);
    }
}

static ARIARoleMap& ariaRoleMap()
{
    initializeRoleMap();
    return *gAriaRoleMap;
}

static ARIAReverseRoleMap& reverseAriaRoleMap()
{
    initializeRoleMap();
    return *gAriaReverseRoleMap;
}

AccessibilityRole AccessibilityObject::ariaRoleToWebCoreRole(const String& value)
{
    ASSERT(!value.isEmpty());
    
    Vector<String> roleVector;
    value.split(' ', roleVector);
    AccessibilityRole role = UnknownRole;
    for (const auto& roleName : roleVector) {
        role = ariaRoleMap().get(roleName);
        if (role)
            return role;
    }
    
    return role;
}

String AccessibilityObject::computedRoleString() const
{
    // FIXME: Need a few special cases that aren't in the RoleMap: option, etc. http://webkit.org/b/128296
    AccessibilityRole role = roleValue();
    if (role == HorizontalRuleRole)
        role = SplitterRole;
    
    return reverseAriaRoleMap().get(role);
}

bool AccessibilityObject::hasHighlighting() const
{
    for (Node* node = this->node(); node; node = node->parentNode()) {
        if (node->hasTagName(markTag))
            return true;
    }
    
    return false;
}

Element* AccessibilityObject::element() const
{
    Node* node = this->node();
    if (node && node->isElementNode())
        return toElement(node);
    return 0;
}

const AtomicString& AccessibilityObject::placeholderValue() const
{
    const AtomicString& placeholder = getAttribute(placeholderAttr);
    if (!placeholder.isEmpty())
        return placeholder;
    
    return nullAtom;
}
    
bool AccessibilityObject::isInsideARIALiveRegion() const
{
    if (supportsARIALiveRegion())
        return true;
    
    for (AccessibilityObject* axParent = parentObject(); axParent; axParent = axParent->parentObject()) {
        if (axParent->supportsARIALiveRegion())
            return true;
    }
    
    return false;
}

bool AccessibilityObject::supportsARIAAttributes() const
{
    // This returns whether the element supports any global ARIA attributes.
    return supportsARIALiveRegion()
        || supportsARIADragging()
        || supportsARIADropping()
        || supportsARIAFlowTo()
        || supportsARIAOwns()
        || hasAttribute(aria_atomicAttr)
        || hasAttribute(aria_busyAttr)
        || hasAttribute(aria_controlsAttr)
        || hasAttribute(aria_describedbyAttr)
        || hasAttribute(aria_disabledAttr)
        || hasAttribute(aria_haspopupAttr)
        || hasAttribute(aria_invalidAttr)
        || hasAttribute(aria_labelAttr)
        || hasAttribute(aria_labelledbyAttr)
        || hasAttribute(aria_relevantAttr);
}
    
bool AccessibilityObject::liveRegionStatusIsEnabled(const AtomicString& liveRegionStatus)
{
    return equalIgnoringCase(liveRegionStatus, "polite") || equalIgnoringCase(liveRegionStatus, "assertive");
}
    
bool AccessibilityObject::supportsARIALiveRegion() const
{
    return liveRegionStatusIsEnabled(ariaLiveRegionStatus());
}

AccessibilityObject* AccessibilityObject::elementAccessibilityHitTest(const IntPoint& point) const
{ 
    // Send the hit test back into the sub-frame if necessary.
    if (isAttachment()) {
        Widget* widget = widgetForAttachmentView();
        // Normalize the point for the widget's bounds.
        if (widget && widget->isFrameView()) {
            if (AXObjectCache* cache = axObjectCache())
                return cache->getOrCreate(widget)->accessibilityHitTest(IntPoint(point - widget->frameRect().location()));
        }
    }
    
    // Check if there are any mock elements that need to be handled.
    for (const auto& child : m_children) {
        if (child->isMockObject() && child->elementRect().contains(point))
            return child->elementAccessibilityHitTest(point);
    }

    return const_cast<AccessibilityObject*>(this); 
}
    
AXObjectCache* AccessibilityObject::axObjectCache() const
{
    Document* doc = document();
    if (doc)
        return doc->axObjectCache();
    return nullptr;
}
    
AccessibilityObject* AccessibilityObject::focusedUIElement() const
{
    Document* doc = document();
    if (!doc)
        return 0;
    
    Page* page = doc->page();
    if (!page)
        return 0;
    
    return AXObjectCache::focusedUIElementForPage(page);
}
    
AccessibilitySortDirection AccessibilityObject::sortDirection() const
{
    const AtomicString& sortAttribute = getAttribute(aria_sortAttr);
    if (equalIgnoringCase(sortAttribute, "ascending"))
        return SortDirectionAscending;
    if (equalIgnoringCase(sortAttribute, "descending"))
        return SortDirectionDescending;
    if (equalIgnoringCase(sortAttribute, "other"))
        return SortDirectionOther;
    
    return SortDirectionNone;
}

bool AccessibilityObject::supportsRangeValue() const
{
    return isProgressIndicator()
        || isSlider()
        || isScrollbar()
        || isSpinButton();
}
    
bool AccessibilityObject::supportsARIASetSize() const
{
    return hasAttribute(aria_setsizeAttr);
}

bool AccessibilityObject::supportsARIAPosInSet() const
{
    return hasAttribute(aria_posinsetAttr);
}
    
int AccessibilityObject::ariaSetSize() const
{
    return getAttribute(aria_setsizeAttr).toInt();
}

int AccessibilityObject::ariaPosInSet() const
{
    return getAttribute(aria_posinsetAttr).toInt();
}
    
String AccessibilityObject::identifierAttribute() const
{
    return getAttribute(idAttr);
}
    
void AccessibilityObject::classList(Vector<String>& classList) const
{
    Node* node = this->node();
    if (!node || !node->isElementNode())
        return;
    
    Element* element = toElement(node);
    DOMTokenList* list = element->classList();
    if (!list)
        return;
    unsigned length = list->length();
    for (unsigned k = 0; k < length; k++)
        classList.append(list->item(k).string());
}

    
bool AccessibilityObject::supportsARIAExpanded() const
{
    // Undefined values should not result in this attribute being exposed to ATs according to ARIA.
    const AtomicString& expanded = getAttribute(aria_expandedAttr);
    if (equalIgnoringCase(expanded, "true") || equalIgnoringCase(expanded, "false"))
        return true;
    switch (roleValue()) {
    case ComboBoxRole:
    case DisclosureTriangleRole:
        return true;
    default:
        return false;
    }
}
    
bool AccessibilityObject::isExpanded() const
{
    if (equalIgnoringCase(getAttribute(aria_expandedAttr), "true"))
        return true;
    
    return false;  
}

bool AccessibilityObject::supportsChecked() const
{
    switch (roleValue()) {
    case CheckBoxRole:
    case MenuItemCheckboxRole:
    case MenuItemRadioRole:
    case RadioButtonRole:
        return true;
    default:
        return false;
    }
}

AccessibilityButtonState AccessibilityObject::checkboxOrRadioValue() const
{
    // If this is a real checkbox or radio button, AccessibilityRenderObject will handle.
    // If it's an ARIA checkbox or radio, the aria-checked attribute should be used.

    const AtomicString& result = getAttribute(aria_checkedAttr);
    if (equalIgnoringCase(result, "true"))
        return ButtonStateOn;
    if (equalIgnoringCase(result, "mixed")) {
        // ARIA says that radio and menuitemradio elements must NOT expose button state mixed.
        AccessibilityRole ariaRole = ariaRoleAttribute();
        if (ariaRole == RadioButtonRole || ariaRole == MenuItemRadioRole)
            return ButtonStateOff;
        return ButtonStateMixed;
    }
    
    if (equalIgnoringCase(getAttribute(indeterminateAttr), "true"))
        return ButtonStateMixed;
    
    return ButtonStateOff;
}

// This is a 1-dimensional scroll offset helper function that's applied
// separately in the horizontal and vertical directions, because the
// logic is the same. The goal is to compute the best scroll offset
// in order to make an object visible within a viewport.
//
// In case the whole object cannot fit, you can specify a
// subfocus - a smaller region within the object that should
// be prioritized. If the whole object can fit, the subfocus is
// ignored.
//
// Example: the viewport is scrolled to the right just enough
// that the object is in view.
//   Before:
//   +----------Viewport---------+
//                         +---Object---+
//                         +--SubFocus--+
//
//   After:
//          +----------Viewport---------+
//                         +---Object---+
//                         +--SubFocus--+
//
// When constraints cannot be fully satisfied, the min
// (left/top) position takes precedence over the max (right/bottom).
//
// Note that the return value represents the ideal new scroll offset.
// This may be out of range - the calling function should clip this
// to the available range.
static int computeBestScrollOffset(int currentScrollOffset,
                                   int subfocusMin, int subfocusMax,
                                   int objectMin, int objectMax,
                                   int viewportMin, int viewportMax) {
    int viewportSize = viewportMax - viewportMin;

    // If the focus size is larger than the viewport size, shrink it in the
    // direction of subfocus.
    if (objectMax - objectMin > viewportSize) {
        // Subfocus must be within focus:
        subfocusMin = std::max(subfocusMin, objectMin);
        subfocusMax = std::min(subfocusMax, objectMax);

        // Subfocus must be no larger than the viewport size; favor top/left.
        if (subfocusMax - subfocusMin > viewportSize)
            subfocusMax = subfocusMin + viewportSize;

        if (subfocusMin + viewportSize > objectMax)
            objectMin = objectMax - viewportSize;
        else {
            objectMin = subfocusMin;
            objectMax = subfocusMin + viewportSize;
        }
    }

    // Exit now if the focus is already within the viewport.
    if (objectMin - currentScrollOffset >= viewportMin
        && objectMax - currentScrollOffset <= viewportMax)
        return currentScrollOffset;

    // Scroll left if we're too far to the right.
    if (objectMax - currentScrollOffset > viewportMax)
        return objectMax - viewportMax;

    // Scroll right if we're too far to the left.
    if (objectMin - currentScrollOffset < viewportMin)
        return objectMin - viewportMin;

    ASSERT_NOT_REACHED();

    // This shouldn't happen.
    return currentScrollOffset;
}

bool AccessibilityObject::isOnscreen() const
{   
    bool isOnscreen = true;

    // To figure out if the element is onscreen, we start by building of a stack starting with the
    // element, and then include every scrollable parent in the hierarchy.
    Vector<const AccessibilityObject*> objects;
    
    objects.append(this);
    for (AccessibilityObject* parentObject = this->parentObject(); parentObject; parentObject = parentObject->parentObject()) {
        if (parentObject->getScrollableAreaIfScrollable())
            objects.append(parentObject);
    }

    // Now, go back through that chain and make sure each inner object is within the
    // visible bounds of the outer object.
    size_t levels = objects.size() - 1;
    
    for (size_t i = levels; i >= 1; i--) {
        const AccessibilityObject* outer = objects[i];
        const AccessibilityObject* inner = objects[i - 1];
        // FIXME: unclear if we need LegacyIOSDocumentVisibleRect.
        const IntRect outerRect = i < levels ? pixelSnappedIntRect(outer->boundingBoxRect()) : outer->getScrollableAreaIfScrollable()->visibleContentRect(ScrollableArea::LegacyIOSDocumentVisibleRect);
        const IntRect innerRect = pixelSnappedIntRect(inner->isAccessibilityScrollView() ? inner->parentObject()->boundingBoxRect() : inner->boundingBoxRect());
        
        if (!outerRect.intersects(innerRect)) {
            isOnscreen = false;
            break;
        }
    }
    
    return isOnscreen;
}

void AccessibilityObject::scrollToMakeVisible() const
{
    IntRect objectRect = pixelSnappedIntRect(boundingBoxRect());
    objectRect.setLocation(IntPoint());
    scrollToMakeVisibleWithSubFocus(objectRect);
}

void AccessibilityObject::scrollToMakeVisibleWithSubFocus(const IntRect& subfocus) const
{
    // Search up the parent chain until we find the first one that's scrollable.
    AccessibilityObject* scrollParent = parentObject();
    ScrollableArea* scrollableArea;
    for (scrollableArea = 0;
         scrollParent && !(scrollableArea = scrollParent->getScrollableAreaIfScrollable());
         scrollParent = scrollParent->parentObject()) { }
    if (!scrollableArea)
        return;

    LayoutRect objectRect = boundingBoxRect();
    IntPoint scrollPosition = scrollableArea->scrollPosition();
    // FIXME: unclear if we need LegacyIOSDocumentVisibleRect.
    IntRect scrollVisibleRect = scrollableArea->visibleContentRect(ScrollableArea::LegacyIOSDocumentVisibleRect);

    int desiredX = computeBestScrollOffset(
        scrollPosition.x(),
        objectRect.x() + subfocus.x(), objectRect.x() + subfocus.maxX(),
        objectRect.x(), objectRect.maxX(),
        0, scrollVisibleRect.width());
    int desiredY = computeBestScrollOffset(
        scrollPosition.y(),
        objectRect.y() + subfocus.y(), objectRect.y() + subfocus.maxY(),
        objectRect.y(), objectRect.maxY(),
        0, scrollVisibleRect.height());

    scrollParent->scrollTo(IntPoint(desiredX, desiredY));

    // Recursively make sure the scroll parent itself is visible.
    if (scrollParent->parentObject())
        scrollParent->scrollToMakeVisible();
}

void AccessibilityObject::scrollToGlobalPoint(const IntPoint& globalPoint) const
{
    // Search up the parent chain and create a vector of all scrollable parent objects
    // and ending with this object itself.
    Vector<const AccessibilityObject*> objects;

    objects.append(this);
    for (AccessibilityObject* parentObject = this->parentObject(); parentObject; parentObject = parentObject->parentObject()) {
        if (parentObject->getScrollableAreaIfScrollable())
            objects.append(parentObject);
    }

    objects.reverse();

    // Start with the outermost scrollable (the main window) and try to scroll the
    // next innermost object to the given point.
    int offsetX = 0, offsetY = 0;
    IntPoint point = globalPoint;
    size_t levels = objects.size() - 1;
    for (size_t i = 0; i < levels; i++) {
        const AccessibilityObject* outer = objects[i];
        const AccessibilityObject* inner = objects[i + 1];

        ScrollableArea* scrollableArea = outer->getScrollableAreaIfScrollable();

        LayoutRect innerRect = inner->isAccessibilityScrollView() ? inner->parentObject()->boundingBoxRect() : inner->boundingBoxRect();
        LayoutRect objectRect = innerRect;
        IntPoint scrollPosition = scrollableArea->scrollPosition();

        // Convert the object rect into local coordinates.
        objectRect.move(offsetX, offsetY);
        if (!outer->isAccessibilityScrollView())
            objectRect.move(scrollPosition.x(), scrollPosition.y());

        int desiredX = computeBestScrollOffset(
            0,
            objectRect.x(), objectRect.maxX(),
            objectRect.x(), objectRect.maxX(),
            point.x(), point.x());
        int desiredY = computeBestScrollOffset(
            0,
            objectRect.y(), objectRect.maxY(),
            objectRect.y(), objectRect.maxY(),
            point.y(), point.y());
        outer->scrollTo(IntPoint(desiredX, desiredY));

        if (outer->isAccessibilityScrollView() && !inner->isAccessibilityScrollView()) {
            // If outer object we just scrolled is a scroll view (main window or iframe) but the
            // inner object is not, keep track of the coordinate transformation to apply to
            // future nested calculations.
            scrollPosition = scrollableArea->scrollPosition();
            offsetX -= (scrollPosition.x() + point.x());
            offsetY -= (scrollPosition.y() + point.y());
            point.move(scrollPosition.x() - innerRect.x(),
                       scrollPosition.y() - innerRect.y());
        } else if (inner->isAccessibilityScrollView()) {
            // Otherwise, if the inner object is a scroll view, reset the coordinate transformation.
            offsetX = 0;
            offsetY = 0;
        }
    }
}

bool AccessibilityObject::lastKnownIsIgnoredValue()
{
    if (m_lastKnownIsIgnoredValue == DefaultBehavior)
        m_lastKnownIsIgnoredValue = accessibilityIsIgnored() ? IgnoreObject : IncludeObject;

    return m_lastKnownIsIgnoredValue == IgnoreObject;
}

void AccessibilityObject::setLastKnownIsIgnoredValue(bool isIgnored)
{
    m_lastKnownIsIgnoredValue = isIgnored ? IgnoreObject : IncludeObject;
}

void AccessibilityObject::notifyIfIgnoredValueChanged()
{
    bool isIgnored = accessibilityIsIgnored();
    if (lastKnownIsIgnoredValue() != isIgnored) {
        if (AXObjectCache* cache = axObjectCache())
            cache->childrenChanged(parentObject());
        setLastKnownIsIgnoredValue(isIgnored);
    }
}

bool AccessibilityObject::ariaPressedIsPresent() const
{
    return !getAttribute(aria_pressedAttr).isEmpty();
}

TextIteratorBehavior AccessibilityObject::textIteratorBehaviorForTextRange() const
{
    TextIteratorBehavior behavior = TextIteratorIgnoresStyleVisibility;
    
#if PLATFORM(GTK) || PLATFORM(EFL)
    // We need to emit replaced elements for GTK, and present
    // them with the 'object replacement character' (0xFFFC).
    behavior = static_cast<TextIteratorBehavior>(behavior | TextIteratorEmitsObjectReplacementCharacters);
#endif
    
    return behavior;
}
    
AccessibilityRole AccessibilityObject::buttonRoleType() const
{
    // If aria-pressed is present, then it should be exposed as a toggle button.
    // http://www.w3.org/TR/wai-aria/states_and_properties#aria-pressed
    if (ariaPressedIsPresent())
        return ToggleButtonRole;
    if (ariaHasPopup())
        return PopUpButtonRole;
    // We don't contemplate RadioButtonRole, as it depends on the input
    // type.

    return ButtonRole;
}

bool AccessibilityObject::isButton() const
{
    AccessibilityRole role = roleValue();

    return role == ButtonRole || role == PopUpButtonRole || role == ToggleButtonRole;
}

bool AccessibilityObject::accessibilityIsIgnoredByDefault() const
{
    return defaultObjectInclusion() == IgnoreObject;
}

// ARIA component of hidden definition.
// http://www.w3.org/TR/wai-aria/terms#def_hidden
bool AccessibilityObject::isARIAHidden() const
{
    for (const AccessibilityObject* object = this; object; object = object->parentObject()) {
        if (equalIgnoringCase(object->getAttribute(aria_hiddenAttr), "true"))
            return true;
    }
    return false;
}

// DOM component of hidden definition.
// http://www.w3.org/TR/wai-aria/terms#def_hidden
bool AccessibilityObject::isDOMHidden() const
{
    RenderObject* renderer = this->renderer();
    if (!renderer)
        return true;
    
    const RenderStyle& style = renderer->style();
    return style.display() == NONE || style.visibility() != VISIBLE;
}

AccessibilityObjectInclusion AccessibilityObject::defaultObjectInclusion() const
{
    if (isARIAHidden())
        return IgnoreObject;
    
    if (isPresentationalChildOfAriaRole())
        return IgnoreObject;
    
    return accessibilityPlatformIncludesObject();
}
    
bool AccessibilityObject::accessibilityIsIgnored() const
{
    AXComputedObjectAttributeCache* attributeCache = nullptr;
    AXObjectCache* cache = axObjectCache();
    if (cache)
        attributeCache = cache->computedObjectAttributeCache();
    
    if (attributeCache) {
        AccessibilityObjectInclusion ignored = attributeCache->getIgnored(axObjectID());
        switch (ignored) {
        case IgnoreObject:
            return true;
        case IncludeObject:
            return false;
        case DefaultBehavior:
            break;
        }
    }

    bool result = computeAccessibilityIsIgnored();

    // In case computing axIsIgnored disables attribute caching, we should refetch the object to see if it exists.
    if (cache && (attributeCache = cache->computedObjectAttributeCache()))
        attributeCache->setIgnored(axObjectID(), result ? IgnoreObject : IncludeObject);

    return result;
}

void AccessibilityObject::elementsFromAttribute(Vector<Element*>& elements, const QualifiedName& attribute) const
{
    Node* node = this->node();
    if (!node || !node->isElementNode())
        return;

    TreeScope& treeScope = node->treeScope();

    String idList = getAttribute(attribute).string();
    if (idList.isEmpty())
        return;

    idList.replace('\n', ' ');
    Vector<String> idVector;
    idList.split(' ', idVector);

    for (const auto& idName : idVector) {
        if (Element* idElement = treeScope.getElementById(idName))
            elements.append(idElement);
    }
}

} // namespace WebCore