Source/WebCore/accessibility/AXObjectCache.cpp - WebKit - Git at Google

 /*
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  *
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  * modification, are permitted provided that the following conditions
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  *
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  *     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.
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  *     its contributors may be used to endorse or promote products derived
  *     from this software without specific prior written permission.
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 #include "config.h"

 #if ENABLE(ACCESSIBILITY)

 #include "AXObjectCache.h"

 #include "AXIsolatedObject.h"
 #include "AXIsolatedTree.h"
 #include "AccessibilityARIAGrid.h"
 #include "AccessibilityARIAGridCell.h"
 #include "AccessibilityARIAGridRow.h"
 #include "AccessibilityAttachment.h"
 #include "AccessibilityImageMapLink.h"
 #include "AccessibilityLabel.h"
 #include "AccessibilityList.h"
 #include "AccessibilityListBox.h"
 #include "AccessibilityListBoxOption.h"
 #include "AccessibilityMathMLElement.h"
 #include "AccessibilityMediaControls.h"
 #include "AccessibilityMediaObject.h"
 #include "AccessibilityMenuList.h"
 #include "AccessibilityMenuListOption.h"
 #include "AccessibilityMenuListPopup.h"
 #include "AccessibilityProgressIndicator.h"
 #include "AccessibilityRenderObject.h"
 #include "AccessibilitySVGElement.h"
 #include "AccessibilitySVGRoot.h"
 #include "AccessibilityScrollView.h"
 #include "AccessibilityScrollbar.h"
 #include "AccessibilitySlider.h"
 #include "AccessibilitySpinButton.h"
 #include "AccessibilityTable.h"
 #include "AccessibilityTableCell.h"
 #include "AccessibilityTableColumn.h"
 #include "AccessibilityTableHeaderContainer.h"
 #include "AccessibilityTableRow.h"
 #include "AccessibilityTree.h"
 #include "AccessibilityTreeItem.h"
 #include "Document.h"
 #include "Editing.h"
 #include "Editor.h"
 #include "ElementIterator.h"
 #include "FocusController.h"
 #include "Frame.h"
 #include "HTMLAreaElement.h"
 #include "HTMLCanvasElement.h"
 #include "HTMLImageElement.h"
 #include "HTMLInputElement.h"
 #include "HTMLLabelElement.h"
 #include "HTMLMeterElement.h"
 #include "HTMLNames.h"
 #include "HTMLParserIdioms.h"
 #include "HTMLTextFormControlElement.h"
 #include "InlineElementBox.h"
 #include "MathMLElement.h"
 #include "Page.h"
 #include "RenderAttachment.h"
 #include "RenderLineBreak.h"
 #include "RenderListBox.h"
 #include "RenderMathMLOperator.h"
 #include "RenderMenuList.h"
 #include "RenderMeter.h"
 #include "RenderProgress.h"
 #include "RenderSVGRoot.h"
 #include "RenderSlider.h"
 #include "RenderTable.h"
 #include "RenderTableCell.h"
 #include "RenderTableRow.h"
 #include "RenderView.h"
 #include "RuntimeEnabledFeatures.h"
 #include "SVGElement.h"
 #include "ScriptDisallowedScope.h"
 #include "ScrollView.h"
 #include "TextBoundaries.h"
 #include "TextControlInnerElements.h"
 #include "TextIterator.h"

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE) && PLATFORM(MAC)
 #include <pal/spi/cocoa/AccessibilitySupportSPI.h>
 #include <pal/spi/cocoa/AccessibilitySupportSoftLink.h>
 #include <pal/spi/mac/HIServicesSPI.h>
 #endif

 #include <wtf/DataLog.h>
 #include <wtf/SetForScope.h>

 #if ENABLE(VIDEO)
 #include "MediaControlElements.h"
 #endif

 #if COMPILER(MSVC)
 // See https://msdn.microsoft.com/en-us/library/1wea5zwe.aspx
 #pragma warning(disable: 4701)
 #endif

 namespace WebCore {

 using namespace HTMLNames;

 const AXID InvalidAXID = 0;

 // Post value change notifications for password fields or elements contained in password fields at a 40hz interval to thwart analysis of typing cadence
 static const Seconds accessibilityPasswordValueChangeNotificationInterval { 25_ms };
 static const Seconds accessibilityLiveRegionChangedNotificationInterval { 20_ms };
 static const Seconds accessibilityFocusModalNodeNotificationInterval { 50_ms };

 static bool rendererNeedsDeferredUpdate(const RenderObject& renderer)
 {
     ASSERT(!renderer.beingDestroyed());
     auto& document = renderer.document();
     return renderer.needsLayout() || document.needsStyleRecalc() || document.inRenderTreeUpdate() || (document.view() && document.view()->layoutContext().isInRenderTreeLayout());
 }

 static bool nodeAndRendererAreValid(Node* node)
 {
     if (!node)
         return false;

     auto* renderer = node->renderer();
     return renderer && !renderer->beingDestroyed();
 }

 AccessibilityObjectInclusion AXComputedObjectAttributeCache::getIgnored(AXID id) const
 {
     auto it = m_idMapping.find(id);
     return it != m_idMapping.end() ? it->value.ignored : AccessibilityObjectInclusion::DefaultBehavior;
 }

 void AXComputedObjectAttributeCache::setIgnored(AXID id, AccessibilityObjectInclusion inclusion)
 {
     HashMap<AXID, CachedAXObjectAttributes>::iterator it = m_idMapping.find(id);
     if (it != m_idMapping.end())
         it->value.ignored = inclusion;
     else {
         CachedAXObjectAttributes attributes;
         attributes.ignored = inclusion;
         m_idMapping.set(id, attributes);
     }
 }

 AccessibilityReplacedText::AccessibilityReplacedText(const VisibleSelection& selection)
 {
     if (AXObjectCache::accessibilityEnabled()) {
         m_replacedRange.startIndex.value = indexForVisiblePosition(selection.start(), m_replacedRange.startIndex.scope);
         if (selection.isRange()) {
             m_replacedText = AccessibilityObject::stringForVisiblePositionRange(selection);
             m_replacedRange.endIndex.value = indexForVisiblePosition(selection.end(), m_replacedRange.endIndex.scope);
         } else
             m_replacedRange.endIndex = m_replacedRange.startIndex;
     }
 }

 void AccessibilityReplacedText::postTextStateChangeNotification(AXObjectCache* cache, AXTextEditType type, const String& text, const VisibleSelection& selection)
 {
     if (!cache)
         return;
     if (!AXObjectCache::accessibilityEnabled())
         return;

     VisiblePosition position = selection.start();
     auto* node = highestEditableRoot(position.deepEquivalent(), HasEditableAXRole);
     if (m_replacedText.length())
         cache->postTextReplacementNotification(node, AXTextEditTypeDelete, m_replacedText, type, text, position);
     else
         cache->postTextStateChangeNotification(node, type, text, position);
 }

 bool AXObjectCache::gAccessibilityEnabled = false;
 bool AXObjectCache::gAccessibilityEnhancedUserInterfaceEnabled = false;

 void AXObjectCache::enableAccessibility()
 {
     gAccessibilityEnabled = true;
 }

 void AXObjectCache::disableAccessibility()
 {
     gAccessibilityEnabled = false;
 }

 void AXObjectCache::setEnhancedUserInterfaceAccessibility(bool flag)
 {
     gAccessibilityEnhancedUserInterfaceEnabled = flag;
 #if PLATFORM(MAC)
     if (flag)
         enableAccessibility();
 #endif
 }

 AXObjectCache::AXObjectCache(Document& document)
     : m_document(document)
     , m_pageID(document.pageID())
     , m_notificationPostTimer(*this, &AXObjectCache::notificationPostTimerFired)
     , m_passwordNotificationPostTimer(*this, &AXObjectCache::passwordNotificationPostTimerFired)
     , m_liveRegionChangedPostTimer(*this, &AXObjectCache::liveRegionChangedNotificationPostTimerFired)
     , m_focusModalNodeTimer(*this, &AXObjectCache::focusModalNodeTimerFired)
     , m_currentModalNode(nullptr)
     , m_performCacheUpdateTimer(*this, &AXObjectCache::performCacheUpdateTimerFired)
 {
     findModalNodes();
 }

 AXObjectCache::~AXObjectCache()
 {
     m_notificationPostTimer.stop();
     m_liveRegionChangedPostTimer.stop();
     m_focusModalNodeTimer.stop();
     m_performCacheUpdateTimer.stop();

     for (const auto& object : m_objects.values())
         object->detach(AccessibilityDetachmentType::CacheDestroyed);

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
     if (m_pageID)
         AXIsolatedTree::removeTreeForPageID(*m_pageID);
 #endif
 }

 void AXObjectCache::findModalNodes()
 {
     // Traverse the DOM tree to look for the aria-modal=true nodes.
     for (Element* element = ElementTraversal::firstWithin(document().rootNode()); element; element = ElementTraversal::nextIncludingPseudo(*element)) {

         // Must have dialog or alertdialog role
         if (!nodeHasRole(element, "dialog") && !nodeHasRole(element, "alertdialog"))
             continue;
         if (!equalLettersIgnoringASCIICase(element->attributeWithoutSynchronization(aria_modalAttr), "true"))
             continue;

         m_modalNodesSet.add(element);
     }

     // Set the current valid aria-modal node if possible.
     updateCurrentModalNode();
 }

 void AXObjectCache::updateCurrentModalNode()
 {
     // There might be multiple nodes with aria-modal=true set.
     // We use this function to pick the one we want.
     m_currentModalNode = nullptr;
     if (m_modalNodesSet.isEmpty())
         return;

     // We only care about the nodes which are visible.
     ListHashSet<RefPtr<Node>> visibleNodes;
     for (auto& object : m_modalNodesSet) {
         if (isNodeVisible(object))
             visibleNodes.add(object);
     }

     if (visibleNodes.isEmpty())
         return;

     // If any of the node are keyboard focused, we want to pick that.
     Node* focusedNode = document().focusedElement();
     for (auto& object : visibleNodes) {
         if (focusedNode != nullptr && focusedNode->isDescendantOf(object.get())) {
             m_currentModalNode = object.get();
             break;
         }
     }

     // If none of the nodes are focused, we want to pick the last dialog in the DOM.
     if (!m_currentModalNode)
         m_currentModalNode = visibleNodes.last().get();
 }

 bool AXObjectCache::isNodeVisible(Node* node) const
 {
     if (!is<Element>(node))
         return false;

     RenderObject* renderer = node->renderer();
     if (!renderer)
         return false;
     const RenderStyle& style = renderer->style();
     if (style.display() == DisplayType::None || style.visibility() != Visibility::Visible)
         return false;

     // We also need to consider aria hidden status.
     if (!isNodeAriaVisible(node))
         return false;

     return true;
 }

 Node* AXObjectCache::modalNode()
 {
     // This function returns the valid aria modal node.
     if (m_modalNodesSet.isEmpty())
         return nullptr;

     // Check the current valid aria modal node first.
     // Usually when one dialog sets aria-modal=true, that dialog is the one we want.
     if (isNodeVisible(m_currentModalNode))
         return m_currentModalNode;

     // Recompute the valid aria modal node when m_currentModalNode is null or hidden.
     updateCurrentModalNode();
     return isNodeVisible(m_currentModalNode) ? m_currentModalNode : nullptr;
 }

 AccessibilityObject* AXObjectCache::focusedImageMapUIElement(HTMLAreaElement* areaElement)
 {
     // Find the corresponding accessibility object for the HTMLAreaElement. This should be
     // in the list of children for its corresponding image.
     if (!areaElement)
         return nullptr;

     HTMLImageElement* imageElement = areaElement->imageElement();
     if (!imageElement)
         return nullptr;

     AccessibilityObject* axRenderImage = areaElement->document().axObjectCache()->getOrCreate(imageElement);
     if (!axRenderImage)
         return nullptr;

     for (const auto& child : axRenderImage->children()) {
         if (!is<AccessibilityImageMapLink>(*child))
             continue;

         if (downcast<AccessibilityImageMapLink>(*child).areaElement() == areaElement)
             return downcast<AccessibilityImageMapLink>(child.get());
     }

     return nullptr;
 }

 AXCoreObject* AXObjectCache::focusedObject(Document& document)
 {
     Element* focusedElement = document.focusedElement();
     if (is<HTMLAreaElement>(focusedElement))
         return focusedImageMapUIElement(downcast<HTMLAreaElement>(focusedElement));

     auto* axObjectCache = document.axObjectCache();
     if (!axObjectCache)
         return nullptr;

     AXCoreObject* focus = axObjectCache->getOrCreate(focusedElement ? focusedElement : static_cast<Node*>(&document));
     if (!focus)
         return nullptr;

     if (focus->shouldFocusActiveDescendant()) {
         if (auto* descendant = focus->activeDescendant())
             focus = descendant;
     }

     // the HTML element, for example, is focusable but has an AX object that is ignored
     if (focus->accessibilityIsIgnored())
         focus = focus->parentObjectUnignored();

     return focus;
 }

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
 AXCoreObject* AXObjectCache::isolatedTreeFocusedObject()
 {
     if (auto tree = getOrCreateIsolatedTree())
         return tree->focusedUIElement().get();

     // Should not get here, couldn't create the IsolatedTree.
     ASSERT_NOT_REACHED();
     return nullptr;
 }

 void AXObjectCache::setIsolatedTreeFocusedObject(Node* focusedNode)
 {
     ASSERT(isMainThread());
     if (!m_pageID)
         return;

     auto* focus = getOrCreate(focusedNode);

     if (auto tree = AXIsolatedTree::treeForPageID(*m_pageID))
         tree->setFocusedNodeID(focus ? focus->objectID() : InvalidAXID);
 }
 #endif

 AXCoreObject* AXObjectCache::focusedUIElementForPage(const Page* page)
 {
     ASSERT(isMainThread());
     if (!gAccessibilityEnabled)
         return nullptr;

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
     if (isIsolatedTreeEnabled())
         return isolatedTreeFocusedObject();
 #endif

     // get the focused node in the page
     Document* focusedDocument = page->focusController().focusedOrMainFrame().document();
     if (!focusedDocument)
         return nullptr;

     focusedDocument->updateStyleIfNeeded();

     return focusedObject(*focusedDocument);
 }

 AccessibilityObject* AXObjectCache::get(Widget* widget)
 {
     if (!widget)
         return nullptr;

     AXID axID = m_widgetObjectMapping.get(widget);
     ASSERT(!HashTraits<AXID>::isDeletedValue(axID));
     if (!axID)
         return nullptr;

     return m_objects.get(axID);
 }

 AccessibilityObject* AXObjectCache::get(RenderObject* renderer)
 {
     if (!renderer)
         return nullptr;

     AXID axID = m_renderObjectMapping.get(renderer);
     ASSERT(!HashTraits<AXID>::isDeletedValue(axID));
     if (!axID)
         return nullptr;

     return m_objects.get(axID);
 }

 AccessibilityObject* AXObjectCache::get(Node* node)
 {
     if (!node)
         return nullptr;

     AXID renderID = node->renderer() ? m_renderObjectMapping.get(node->renderer()) : 0;
     ASSERT(!HashTraits<AXID>::isDeletedValue(renderID));

     AXID nodeID = m_nodeObjectMapping.get(node);
     ASSERT(!HashTraits<AXID>::isDeletedValue(nodeID));

     if (node->renderer() && nodeID && !renderID) {
         // This can happen if an AccessibilityNodeObject is created for a node that's not
         // rendered, but later something changes and it gets a renderer (like if it's
         // reparented).
         remove(nodeID);
         return nullptr;
     }

     if (renderID)
         return m_objects.get(renderID);

     if (!nodeID)
         return nullptr;

     return m_objects.get(nodeID);
 }

 // FIXME: This probably belongs on Node.
 // FIXME: This should take a const char*, but one caller passes nullAtom().
 bool nodeHasRole(Node* node, const String& role)
 {
     if (!node || !is<Element>(node))
         return false;

     auto& roleValue = downcast<Element>(*node).attributeWithoutSynchronization(roleAttr);
     if (role.isNull())
         return roleValue.isEmpty();
     if (roleValue.isEmpty())
         return false;

     return SpaceSplitString(roleValue, true).contains(role);
 }

 static Ref<AccessibilityObject> createFromRenderer(RenderObject* renderer)
 {
     // FIXME: How could renderer->node() ever not be an Element?
     Node* node = renderer->node();

     // If the node is aria role="list" or the aria role is empty and its a
     // ul/ol/dl type (it shouldn't be a list if aria says otherwise).
     if (node && ((nodeHasRole(node, "list") || nodeHasRole(node, "directory"))
                       || (nodeHasRole(node, nullAtom()) && (node->hasTagName(ulTag) || node->hasTagName(olTag) || node->hasTagName(dlTag)))))
         return AccessibilityList::create(renderer);

     // aria tables
     if (nodeHasRole(node, "grid") || nodeHasRole(node, "treegrid") || nodeHasRole(node, "table"))
         return AccessibilityARIAGrid::create(renderer);
     if (nodeHasRole(node, "row"))
         return AccessibilityARIAGridRow::create(renderer);
     if (nodeHasRole(node, "gridcell") || nodeHasRole(node, "cell") || nodeHasRole(node, "columnheader") || nodeHasRole(node, "rowheader"))
         return AccessibilityARIAGridCell::create(renderer);

     // aria tree
     if (nodeHasRole(node, "tree"))
         return AccessibilityTree::create(renderer);
     if (nodeHasRole(node, "treeitem"))
         return AccessibilityTreeItem::create(renderer);

     if (node && is<HTMLLabelElement>(node) && nodeHasRole(node, nullAtom()))
         return AccessibilityLabel::create(renderer);

 #if PLATFORM(IOS_FAMILY)
     if (is<HTMLMediaElement>(node) && nodeHasRole(node, nullAtom()))
         return AccessibilityMediaObject::create(renderer);
 #endif

 #if ENABLE(VIDEO)
     // media controls
     if (node && node->isMediaControlElement())
         return AccessibilityMediaControl::create(renderer);
 #endif

     if (is<RenderSVGRoot>(*renderer))
         return AccessibilitySVGRoot::create(renderer);

     if (is<SVGElement>(node))
         return AccessibilitySVGElement::create(renderer);

 #if ENABLE(MATHML)
     // The mfenced element creates anonymous RenderMathMLOperators which should be treated
     // as MathML elements and assigned the MathElementRole so that platform logic regarding
     // inclusion and role mapping is not bypassed.
     bool isAnonymousOperator = renderer->isAnonymous() && is<RenderMathMLOperator>(*renderer);
     if (isAnonymousOperator || is<MathMLElement>(node))
         return AccessibilityMathMLElement::create(renderer, isAnonymousOperator);
 #endif

     if (is<RenderBoxModelObject>(*renderer)) {
         RenderBoxModelObject& cssBox = downcast<RenderBoxModelObject>(*renderer);
         if (is<RenderListBox>(cssBox))
             return AccessibilityListBox::create(&downcast<RenderListBox>(cssBox));
         if (is<RenderMenuList>(cssBox))
             return AccessibilityMenuList::create(&downcast<RenderMenuList>(cssBox));

         // standard tables
         if (is<RenderTable>(cssBox))
             return AccessibilityTable::create(&downcast<RenderTable>(cssBox));
         if (is<RenderTableRow>(cssBox))
             return AccessibilityTableRow::create(&downcast<RenderTableRow>(cssBox));
         if (is<RenderTableCell>(cssBox))
             return AccessibilityTableCell::create(&downcast<RenderTableCell>(cssBox));

         // progress bar
         if (is<RenderProgress>(cssBox))
             return AccessibilityProgressIndicator::create(&downcast<RenderProgress>(cssBox));

 #if ENABLE(ATTACHMENT_ELEMENT)
         if (is<RenderAttachment>(cssBox))
             return AccessibilityAttachment::create(&downcast<RenderAttachment>(cssBox));
 #endif
 #if ENABLE(METER_ELEMENT)
         if (is<RenderMeter>(cssBox))
             return AccessibilityProgressIndicator::create(&downcast<RenderMeter>(cssBox));
 #endif

         // input type=range
         if (is<RenderSlider>(cssBox))
             return AccessibilitySlider::create(&downcast<RenderSlider>(cssBox));
     }

     return AccessibilityRenderObject::create(renderer);
 }

 static Ref<AccessibilityObject> createFromNode(Node* node)
 {
     return AccessibilityNodeObject::create(node);
 }

 void AXObjectCache::cacheAndInitializeWrapper(AccessibilityObject* newObject, DOMObjectVariant domObject)
 {
     ASSERT(newObject);
     AXID axID = getAXID(newObject);
     WTF::switchOn(domObject,
         [&axID, this] (RenderObject* typedValue) { m_renderObjectMapping.set(typedValue, axID); },
         [&axID, this] (Node* typedValue) { m_nodeObjectMapping.set(typedValue, axID); },
         [&axID, this] (Widget* typedValue) { m_widgetObjectMapping.set(typedValue, axID); },
         [] (auto&) { }
     );
     m_objects.set(axID, newObject);
     newObject->init();
     attachWrapper(newObject);
 }

 AccessibilityObject* AXObjectCache::getOrCreate(Widget* widget)
 {
     if (!widget)
         return nullptr;

     if (AccessibilityObject* obj = get(widget))
         return obj;

     RefPtr<AccessibilityObject> newObj;
     if (is<ScrollView>(*widget))
         newObj = AccessibilityScrollView::create(downcast<ScrollView>(widget));
     else if (is<Scrollbar>(*widget))
         newObj = AccessibilityScrollbar::create(downcast<Scrollbar>(widget));

     // Will crash later if we have two objects for the same widget.
     ASSERT(!get(widget));

     // Catch the case if an (unsupported) widget type is used. Only FrameView and ScrollBar are supported now.
     ASSERT(newObj);
     if (!newObj)
         return nullptr;

     cacheAndInitializeWrapper(newObj.get(), widget);
     return newObj.get();
 }

 AccessibilityObject* AXObjectCache::getOrCreate(Node* node)
 {
     if (!node)
         return nullptr;

     if (AccessibilityObject* obj = get(node))
         return obj;

     if (node->renderer())
         return getOrCreate(node->renderer());

     if (!node->parentElement())
         return nullptr;

     // It's only allowed to create an AccessibilityObject from a Node if it's in a canvas subtree.
     // Or if it's a hidden element, but we still want to expose it because of other ARIA attributes.
     bool inCanvasSubtree = lineageOfType<HTMLCanvasElement>(*node->parentElement()).first();
     bool isHidden = isNodeAriaVisible(node);

     bool insideMeterElement = false;
 #if ENABLE(METER_ELEMENT)
     insideMeterElement = is<HTMLMeterElement>(*node->parentElement());
 #endif

     if (!inCanvasSubtree && !isHidden && !insideMeterElement)
         return nullptr;

     auto protectedNode = makeRef(*node);

     // Fallback content is only focusable as long as the canvas is displayed and visible.
     // Update the style before Element::isFocusable() gets called.
     if (inCanvasSubtree)
         node->document().updateStyleIfNeeded();

     RefPtr<AccessibilityObject> newObj = createFromNode(node);

     // Will crash later if we have two objects for the same node.
     ASSERT(!get(node));

     cacheAndInitializeWrapper(newObj.get(), node);
     newObj->setLastKnownIsIgnoredValue(newObj->accessibilityIsIgnored());
     // Sometimes asking accessibilityIsIgnored() will cause the newObject to be deallocated, and then
     // it will disappear when this function is finished, leading to a use-after-free.
     if (newObj->isDetached())
         return nullptr;

     return newObj.get();
 }

 AccessibilityObject* AXObjectCache::getOrCreate(RenderObject* renderer)
 {
     if (!renderer)
         return nullptr;

     if (AccessibilityObject* obj = get(renderer))
         return obj;

     RefPtr<AccessibilityObject> newObj = createFromRenderer(renderer);

     // Will crash later if we have two objects for the same renderer.
     ASSERT(!get(renderer));

     cacheAndInitializeWrapper(newObj.get(), renderer);
     newObj->setLastKnownIsIgnoredValue(newObj->accessibilityIsIgnored());
     // Sometimes asking accessibilityIsIgnored() will cause the newObject to be deallocated, and then
     // it will disappear when this function is finished, leading to a use-after-free.
     if (newObj->isDetached())
         return nullptr;

     return newObj.get();
 }

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
 bool AXObjectCache::clientSupportsIsolatedTree()
 {
     if (!RuntimeEnabledFeatures::sharedFeatures().isAccessibilityIsolatedTreeEnabled())
         return false;

     return _AXGetClientForCurrentRequestUntrusted() == kAXClientTypeVoiceOver;
 }

 bool AXObjectCache::isIsolatedTreeEnabled()
 {
     return _AXSIsolatedTreeModeFunctionIsAvailable() && _AXSIsolatedTreeMode_Soft() != AXSIsolatedTreeModeOff && clientSupportsIsolatedTree();
 }

 #endif

 AXCoreObject* AXObjectCache::rootObject()
 {
     if (!gAccessibilityEnabled)
         return nullptr;

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
     if (clientSupportsIsolatedTree())
         return isolatedTreeRootObject();
 #endif

     return getOrCreate(m_document.view());
 }

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)

 void AXObjectCache::initializeSecondaryAXThread()
 {
     // Now that we have created our tree, initialize the secondary thread,
     // so future requests come in on the other thread.
     if (_AXSIsolatedTreeModeFunctionIsAvailable() && _AXSIsolatedTreeMode_Soft() == AXSIsolatedTreeModeSecondaryThread)
         _AXUIElementUseSecondaryAXThread(true);
 }

 RefPtr<AXIsolatedTree> AXObjectCache::getOrCreateIsolatedTree() const
 {
     if (!m_pageID)
         return nullptr;

     auto tree = AXIsolatedTree::treeForPageID(*m_pageID);
     if (!tree) {
         tree = Accessibility::retrieveValueFromMainThread<RefPtr<AXIsolatedTree>>([this] () -> RefPtr<AXIsolatedTree> {
             return generateIsolatedTree(*m_pageID, m_document);
         });
         AXObjectCache::initializeSecondaryAXThread();
     }

     return tree;
 }

 AXCoreObject* AXObjectCache::isolatedTreeRootObject()
 {
     if (auto tree = getOrCreateIsolatedTree())
         return tree->rootNode().get();

     // Should not get here, couldn't create the IsolatedTree.
     ASSERT_NOT_REACHED();
     return nullptr;
 }
 #endif

 bool AXObjectCache::canUseSecondaryAXThread()
 {
 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE) && PLATFORM(MAC)
     if (_AXUIElementRequestServicedBySecondaryAXThread())
         return true;

     // _AXUIElementRequestServicedBySecondaryAXThread returns false for
     // LayoutTests, but we still want to run LayoutTests using isolated tree on
     // a secondary thread to simulate the actual execution.
     return _AXSIsolatedTreeModeFunctionIsAvailable() && _AXSIsolatedTreeMode_Soft() == AXSIsolatedTreeModeSecondaryThread && clientSupportsIsolatedTree();
 #else
     return false;
 #endif
 }

 AccessibilityObject* AXObjectCache::rootObjectForFrame(Frame* frame)
 {
     if (!gAccessibilityEnabled)
         return nullptr;

     if (!frame)
         return nullptr;
     return getOrCreate(frame->view());
 }

 AccessibilityObject* AXObjectCache::getOrCreate(AccessibilityRole role)
 {
     RefPtr<AccessibilityObject> obj;

     // will be filled in...
     switch (role) {
     case AccessibilityRole::ListBoxOption:
         obj = AccessibilityListBoxOption::create();
         break;
     case AccessibilityRole::ImageMapLink:
         obj = AccessibilityImageMapLink::create();
         break;
     case AccessibilityRole::Column:
         obj = AccessibilityTableColumn::create();
         break;
     case AccessibilityRole::TableHeaderContainer:
         obj = AccessibilityTableHeaderContainer::create();
         break;
     case AccessibilityRole::SliderThumb:
         obj = AccessibilitySliderThumb::create();
         break;
     case AccessibilityRole::MenuListPopup:
         obj = AccessibilityMenuListPopup::create();
         break;
     case AccessibilityRole::MenuListOption:
         obj = AccessibilityMenuListOption::create();
         break;
     case AccessibilityRole::SpinButton:
         obj = AccessibilitySpinButton::create();
         break;
     case AccessibilityRole::SpinButtonPart:
         obj = AccessibilitySpinButtonPart::create();
         break;
     default:
         obj = nullptr;
     }

     if (!obj)
         return nullptr;

     cacheAndInitializeWrapper(obj.get());
     return obj.get();
 }

 void AXObjectCache::remove(AXID axID)
 {
     if (!axID)
         return;

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
     if (m_pageID) {
         if (auto tree = AXIsolatedTree::treeForPageID(*m_pageID))
             tree->removeNode(axID);
     }
 #endif

     auto object = m_objects.take(axID);
     if (!object)
         return;

     object->detach(AccessibilityDetachmentType::ElementDestroyed);

     m_idsInUse.remove(axID);
     ASSERT(m_objects.size() >= m_idsInUse.size());
 }

 void AXObjectCache::remove(RenderObject* renderer)
 {
     if (!renderer)
         return;
     remove(m_renderObjectMapping.take(renderer));
 }

 void AXObjectCache::remove(Node& node)
 {
     if (is<Element>(node)) {
         m_deferredRecomputeIsIgnoredList.remove(downcast<Element>(&node));
         m_deferredSelectedChildredChangedList.remove(downcast<Element>(&node));
         m_deferredTextFormControlValue.remove(downcast<Element>(&node));
         m_deferredAttributeChange.remove(downcast<Element>(&node));
     }
     m_deferredChildrenChangedNodeList.remove(&node);
     m_deferredTextChangedList.remove(&node);
     // Remove the entry if the new focused node is being removed.
     m_deferredFocusedNodeChange.removeAllMatching([&node](auto& entry) -> bool {
         return entry.second == &node;
     });
     // Set nullptr to the old focused node if it is being removed.
     std::for_each(m_deferredFocusedNodeChange.begin(), m_deferredFocusedNodeChange.end(), [&node](auto& entry) {
         if (entry.first == &node)
             entry.first = nullptr;
     });

     removeNodeForUse(node);

     remove(m_nodeObjectMapping.take(&node));

     if (m_currentModalNode == &node)
         m_currentModalNode = nullptr;
     m_modalNodesSet.remove(&node);

     remove(node.renderer());
 }

 void AXObjectCache::remove(Widget* view)
 {
     if (!view)
         return;
     remove(m_widgetObjectMapping.take(view));
 }


 #if !PLATFORM(WIN)
 AXID AXObjectCache::platformGenerateAXID() const
 {
     static AXID lastUsedID = 0;

     // Generate a new ID.
     AXID objID = lastUsedID;
     do {
         ++objID;
     } while (!objID || HashTraits<AXID>::isDeletedValue(objID) || m_idsInUse.contains(objID));

     lastUsedID = objID;

     return objID;
 }
 #endif

 AXID AXObjectCache::getAXID(AccessibilityObject* obj)
 {
     // check for already-assigned ID
     AXID objID = obj->objectID();
     if (objID) {
         ASSERT(m_idsInUse.contains(objID));
         return objID;
     }

     objID = platformGenerateAXID();

     m_idsInUse.add(objID);
     obj->setObjectID(objID);

     return objID;
 }

 void AXObjectCache::textChanged(Node* node)
 {
     textChanged(getOrCreate(node));
 }

 void AXObjectCache::textChanged(AccessibilityObject* obj)
 {
     if (!obj)
         return;

     bool parentAlreadyExists = obj->parentObjectIfExists();
     obj->textChanged();
     postNotification(obj, obj->document(), AXObjectCache::AXTextChanged);
     if (parentAlreadyExists)
         obj->notifyIfIgnoredValueChanged();
 }

 void AXObjectCache::updateCacheAfterNodeIsAttached(Node* node)
 {
     // Calling get() will update the AX object if we had an AccessibilityNodeObject but now we need
     // an AccessibilityRenderObject, because it was reparented to a location outside of a canvas.
     get(node);
 }

 void AXObjectCache::handleMenuOpened(Node* node)
 {
     if (!node || !node->renderer() || !nodeHasRole(node, "menu"))
         return;

     postNotification(getOrCreate(node), &document(), AXMenuOpened);
 }

 void AXObjectCache::handleLiveRegionCreated(Node* node)
 {
     if (!is<Element>(node) || !node->renderer())
         return;

     Element* element = downcast<Element>(node);
     String liveRegionStatus = element->attributeWithoutSynchronization(aria_liveAttr);
     if (liveRegionStatus.isEmpty()) {
         const AtomString& ariaRole = element->attributeWithoutSynchronization(roleAttr);
         if (!ariaRole.isEmpty())
             liveRegionStatus = AccessibilityObject::defaultLiveRegionStatusForRole(AccessibilityObject::ariaRoleToWebCoreRole(ariaRole));
     }

     if (AccessibilityObject::liveRegionStatusIsEnabled(liveRegionStatus))
         postNotification(getOrCreate(node), &document(), AXLiveRegionCreated);
 }

 void AXObjectCache::childrenChanged(Node* node, Node* newChild)
 {
     if (newChild)
         m_deferredChildrenChangedNodeList.add(newChild);

     childrenChanged(get(node));
 }

 void AXObjectCache::childrenChanged(RenderObject* renderer, RenderObject* newChild)
 {
     if (!renderer)
         return;

     if (newChild && newChild->node())
         m_deferredChildrenChangedNodeList.add(newChild->node());

     childrenChanged(get(renderer));
 }

 void AXObjectCache::childrenChanged(AXCoreObject* obj)
 {
     if (!obj)
         return;

     m_deferredChildrenChangedList.add(obj);
 }

 void AXObjectCache::notificationPostTimerFired()
 {
     Ref<Document> protectorForCacheOwner(m_document);
     m_notificationPostTimer.stop();

     // In tests, posting notifications has a tendency to immediately queue up other notifications, which can lead to unexpected behavior
     // when the notification list is cleared at the end. Instead copy this list at the start.
     auto notifications = WTFMove(m_notificationsToPost);

     for (const auto& note : notifications) {
         AXCoreObject* obj = note.first.get();
         if (!obj->objectID())
             continue;

         if (!obj->axObjectCache())
             continue;

 #ifndef NDEBUG
         // Make sure none of the render views are in the process of being layed out.
         // Notifications should only be sent after the renderer has finished
         if (is<AccessibilityRenderObject>(*obj)) {
             if (auto* renderer = downcast<AccessibilityRenderObject>(*obj).renderer())
                 ASSERT(!renderer->view().frameView().layoutContext().layoutState());
         }
 #endif

         AXNotification notification = note.second;

         // Ensure that this menu really is a menu. We do this check here so that we don't have to create
         // the axChildren when the menu is marked as opening.
         if (notification == AXMenuOpened) {
             obj->updateChildrenIfNecessary();
             if (obj->roleValue() != AccessibilityRole::Menu)
                 continue;
         }

         if (notification == AXChildrenChanged && obj->parentObjectIfExists() && obj->lastKnownIsIgnoredValue() != obj->accessibilityIsIgnored())
             childrenChanged(obj->parentObject());

         postPlatformNotification(obj, notification);
     }

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
     updateIsolatedTree(notifications);
 #endif
 }

 void AXObjectCache::passwordNotificationPostTimerFired()
 {
 #if PLATFORM(COCOA)
     m_passwordNotificationPostTimer.stop();

     // In tests, posting notifications has a tendency to immediately queue up other notifications, which can lead to unexpected behavior
     // when the notification list is cleared at the end. Instead copy this list at the start.
     auto notifications = WTFMove(m_passwordNotificationsToPost);

     for (auto& notification : notifications)
         postTextStateChangePlatformNotification(notification.get(), AXTextEditTypeInsert, " ", VisiblePosition());
 #endif
 }

 void AXObjectCache::postNotification(RenderObject* renderer, AXNotification notification, PostTarget postTarget, PostType postType)
 {
     if (!renderer)
         return;

     stopCachingComputedObjectAttributes();

     // Get an accessibility object that already exists. One should not be created here
     // because a render update may be in progress and creating an AX object can re-trigger a layout
     RefPtr<AccessibilityObject> object = get(renderer);
     while (!object && renderer) {
         renderer = renderer->parent();
         object = get(renderer);
     }

     if (!renderer)
         return;

     postNotification(object.get(), &renderer->document(), notification, postTarget, postType);
 }

 void AXObjectCache::postNotification(Node* node, AXNotification notification, PostTarget postTarget, PostType postType)
 {
     if (!node)
         return;

     stopCachingComputedObjectAttributes();

     // Get an accessibility object that already exists. One should not be created here
     // because a render update may be in progress and creating an AX object can re-trigger a layout
     RefPtr<AccessibilityObject> object = get(node);
     while (!object && node) {
         node = node->parentNode();
         object = get(node);
     }

     if (!node)
         return;

     postNotification(object.get(), &node->document(), notification, postTarget, postType);
 }

 void AXObjectCache::postNotification(AXCoreObject* object, Document* document, AXNotification notification, PostTarget postTarget, PostType postType)
 {
     stopCachingComputedObjectAttributes();

     if (object && postTarget == TargetObservableParent)
         object = object->observableObject();

     if (!object && document)
         object = get(document->renderView());

     if (!object)
         return;

     if (postType == PostAsynchronously) {
         m_notificationsToPost.append(std::make_pair(object, notification));
         if (!m_notificationPostTimer.isActive())
             m_notificationPostTimer.startOneShot(0_s);
     } else {
 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
         updateIsolatedTree(*object, notification);
 #endif

         postPlatformNotification(object, notification);
     }
 }

 void AXObjectCache::checkedStateChanged(Node* node)
 {
     postNotification(node, AXObjectCache::AXCheckedStateChanged);
 }

 void AXObjectCache::handleMenuItemSelected(Node* node)
 {
     if (!node)
         return;

     if (!nodeHasRole(node, "menuitem") && !nodeHasRole(node, "menuitemradio") && !nodeHasRole(node, "menuitemcheckbox"))
         return;

     if (!downcast<Element>(*node).focused() && !equalLettersIgnoringASCIICase(downcast<Element>(*node).attributeWithoutSynchronization(aria_selectedAttr), "true"))
         return;

     postNotification(getOrCreate(node), &document(), AXMenuListItemSelected);
 }

 void AXObjectCache::deferFocusedUIElementChangeIfNeeded(Node* oldNode, Node* newNode)
 {
     if (nodeAndRendererAreValid(newNode) && rendererNeedsDeferredUpdate(*newNode->renderer())) {
         m_deferredFocusedNodeChange.append({ oldNode, newNode });
         if (!newNode->renderer()->needsLayout() && !m_performCacheUpdateTimer.isActive())
             m_performCacheUpdateTimer.startOneShot(0_s);
     } else
         handleFocusedUIElementChanged(oldNode, newNode);
 }

 void AXObjectCache::handleFocusedUIElementChanged(Node* oldNode, Node* newNode)
 {
 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
     setIsolatedTreeFocusedObject(newNode);
 #endif

     handleMenuItemSelected(newNode);
     platformHandleFocusedUIElementChanged(oldNode, newNode);
 }

 void AXObjectCache::selectedChildrenChanged(Node* node)
 {
     handleMenuItemSelected(node);

     // postTarget is TargetObservableParent so that you can pass in any child of an element and it will go up the parent tree
     // to find the container which should send out the notification.
     postNotification(node, AXSelectedChildrenChanged, TargetObservableParent);
 }

 void AXObjectCache::selectedChildrenChanged(RenderObject* renderer)
 {
     if (renderer)
         handleMenuItemSelected(renderer->node());

     // postTarget is TargetObservableParent so that you can pass in any child of an element and it will go up the parent tree
     // to find the container which should send out the notification.
     postNotification(renderer, AXSelectedChildrenChanged, TargetObservableParent);
 }

 #ifndef NDEBUG
 void AXObjectCache::showIntent(const AXTextStateChangeIntent &intent)
 {
     switch (intent.type) {
     case AXTextStateChangeTypeUnknown:
         dataLog("Unknown");
         break;
     case AXTextStateChangeTypeEdit:
         dataLog("Edit::");
         break;
     case AXTextStateChangeTypeSelectionMove:
         dataLog("Move::");
         break;
     case AXTextStateChangeTypeSelectionExtend:
         dataLog("Extend::");
         break;
     case AXTextStateChangeTypeSelectionBoundary:
         dataLog("Boundary::");
         break;
     }
     switch (intent.type) {
     case AXTextStateChangeTypeUnknown:
         break;
     case AXTextStateChangeTypeEdit:
         switch (intent.change) {
         case AXTextEditTypeUnknown:
             dataLog("Unknown");
             break;
         case AXTextEditTypeDelete:
             dataLog("Delete");
             break;
         case AXTextEditTypeInsert:
             dataLog("Insert");
             break;
         case AXTextEditTypeDictation:
             dataLog("DictationInsert");
             break;
         case AXTextEditTypeTyping:
             dataLog("TypingInsert");
             break;
         case AXTextEditTypeCut:
             dataLog("Cut");
             break;
         case AXTextEditTypePaste:
             dataLog("Paste");
             break;
         case AXTextEditTypeAttributesChange:
             dataLog("AttributesChange");
             break;
         }
         break;
     case AXTextStateChangeTypeSelectionMove:
     case AXTextStateChangeTypeSelectionExtend:
     case AXTextStateChangeTypeSelectionBoundary:
         switch (intent.selection.direction) {
         case AXTextSelectionDirectionUnknown:
             dataLog("Unknown::");
             break;
         case AXTextSelectionDirectionBeginning:
             dataLog("Beginning::");
             break;
         case AXTextSelectionDirectionEnd:
             dataLog("End::");
             break;
         case AXTextSelectionDirectionPrevious:
             dataLog("Previous::");
             break;
         case AXTextSelectionDirectionNext:
             dataLog("Next::");
             break;
         case AXTextSelectionDirectionDiscontiguous:
             dataLog("Discontiguous::");
             break;
         }
         switch (intent.selection.direction) {
         case AXTextSelectionDirectionUnknown:
         case AXTextSelectionDirectionBeginning:
         case AXTextSelectionDirectionEnd:
         case AXTextSelectionDirectionPrevious:
         case AXTextSelectionDirectionNext:
             switch (intent.selection.granularity) {
             case AXTextSelectionGranularityUnknown:
                 dataLog("Unknown");
                 break;
             case AXTextSelectionGranularityCharacter:
                 dataLog("Character");
                 break;
             case AXTextSelectionGranularityWord:
                 dataLog("Word");
                 break;
             case AXTextSelectionGranularityLine:
                 dataLog("Line");
                 break;
             case AXTextSelectionGranularitySentence:
                 dataLog("Sentence");
                 break;
             case AXTextSelectionGranularityParagraph:
                 dataLog("Paragraph");
                 break;
             case AXTextSelectionGranularityPage:
                 dataLog("Page");
                 break;
             case AXTextSelectionGranularityDocument:
                 dataLog("Document");
                 break;
             case AXTextSelectionGranularityAll:
                 dataLog("All");
                 break;
             }
             break;
         case AXTextSelectionDirectionDiscontiguous:
             break;
         }
         break;
     }
     dataLog("\n");
 }
 #endif

 void AXObjectCache::setTextSelectionIntent(const AXTextStateChangeIntent& intent)
 {
     m_textSelectionIntent = intent;
 }

 void AXObjectCache::setIsSynchronizingSelection(bool isSynchronizing)
 {
     m_isSynchronizingSelection = isSynchronizing;
 }

 static bool isPasswordFieldOrContainedByPasswordField(AccessibilityObject* object)
 {
     return object && (object->isPasswordField() || object->isContainedByPasswordField());
 }

 void AXObjectCache::postTextStateChangeNotification(Node* node, const AXTextStateChangeIntent& intent, const VisibleSelection& selection)
 {
     if (!node)
         return;

 #if PLATFORM(COCOA)
     stopCachingComputedObjectAttributes();

     postTextStateChangeNotification(getOrCreate(node), intent, selection);
 #else
     postNotification(node->renderer(), AXObjectCache::AXSelectedTextChanged, TargetObservableParent);
     UNUSED_PARAM(intent);
     UNUSED_PARAM(selection);
 #endif
 }

 void AXObjectCache::postTextStateChangeNotification(const Position& position, const AXTextStateChangeIntent& intent, const VisibleSelection& selection)
 {
     Node* node = position.deprecatedNode();
     if (!node)
         return;

     stopCachingComputedObjectAttributes();

 #if PLATFORM(COCOA)
     AccessibilityObject* object = getOrCreate(node);
     if (object && object->accessibilityIsIgnored()) {
         if (position.atLastEditingPositionForNode()) {
             if (AccessibilityObject* nextSibling = object->nextSiblingUnignored(1))
                 object = nextSibling;
         } else if (position.atFirstEditingPositionForNode()) {
             if (AccessibilityObject* previousSibling = object->previousSiblingUnignored(1))
                 object = previousSibling;
         }
     }

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
     updateIsolatedTree(*object, AXSelectedTextChanged);
 #endif

     postTextStateChangeNotification(object, intent, selection);
 #else
     postTextStateChangeNotification(node, intent, selection);
 #endif
 }

 void AXObjectCache::postTextStateChangeNotification(AccessibilityObject* object, const AXTextStateChangeIntent& intent, const VisibleSelection& selection)
 {
     stopCachingComputedObjectAttributes();

 #if PLATFORM(COCOA)
     if (object) {
         if (isPasswordFieldOrContainedByPasswordField(object))
             return;

         if (auto observableObject = object->observableObject())
             object = observableObject;
     }

     const AXTextStateChangeIntent& newIntent = (intent.type == AXTextStateChangeTypeUnknown || (m_isSynchronizingSelection && m_textSelectionIntent.type != AXTextStateChangeTypeUnknown)) ? m_textSelectionIntent : intent;
     postTextStateChangePlatformNotification(object, newIntent, selection);
 #else
     UNUSED_PARAM(object);
     UNUSED_PARAM(intent);
     UNUSED_PARAM(selection);
 #endif

     setTextSelectionIntent(AXTextStateChangeIntent());
     setIsSynchronizingSelection(false);
 }

 void AXObjectCache::postTextStateChangeNotification(Node* node, AXTextEditType type, const String& text, const VisiblePosition& position)
 {
     if (!node || type == AXTextEditTypeUnknown)
         return;

     stopCachingComputedObjectAttributes();

     AccessibilityObject* object = getOrCreate(node);
 #if PLATFORM(COCOA)
     if (object) {
         if (enqueuePasswordValueChangeNotification(object))
             return;
         object = object->observableObject();
     }

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
     updateIsolatedTree(*object, AXValueChanged);
 #endif

     postTextStateChangePlatformNotification(object, type, text, position);
 #else
     nodeTextChangePlatformNotification(object, textChangeForEditType(type), position.deepEquivalent().deprecatedEditingOffset(), text);
 #endif
 }

 void AXObjectCache::postTextReplacementNotification(Node* node, AXTextEditType deletionType, const String& deletedText, AXTextEditType insertionType, const String& insertedText, const VisiblePosition& position)
 {
     if (!node)
         return;
     if (deletionType != AXTextEditTypeDelete)
         return;
     if (!(insertionType == AXTextEditTypeInsert || insertionType == AXTextEditTypeTyping || insertionType == AXTextEditTypeDictation || insertionType == AXTextEditTypePaste))
         return;

     stopCachingComputedObjectAttributes();

     AccessibilityObject* object = getOrCreate(node);
 #if PLATFORM(COCOA)
     if (object) {
         if (enqueuePasswordValueChangeNotification(object))
             return;
         object = object->observableObject();
     }

     postTextReplacementPlatformNotification(object, deletionType, deletedText, insertionType, insertedText, position);
 #else
     nodeTextChangePlatformNotification(object, textChangeForEditType(deletionType), position.deepEquivalent().deprecatedEditingOffset(), deletedText);
     nodeTextChangePlatformNotification(object, textChangeForEditType(insertionType), position.deepEquivalent().deprecatedEditingOffset(), insertedText);
 #endif
 }

 void AXObjectCache::postTextReplacementNotificationForTextControl(HTMLTextFormControlElement& textControl, const String& deletedText, const String& insertedText)
 {
     stopCachingComputedObjectAttributes();

     AccessibilityObject* object = getOrCreate(&textControl);
 #if PLATFORM(COCOA)
     if (object) {
         if (enqueuePasswordValueChangeNotification(object))
             return;
         object = object->observableObject();
     }

     postTextReplacementPlatformNotificationForTextControl(object, deletedText, insertedText, textControl);
 #else
     nodeTextChangePlatformNotification(object, textChangeForEditType(AXTextEditTypeDelete), 0, deletedText);
     nodeTextChangePlatformNotification(object, textChangeForEditType(AXTextEditTypeInsert), 0, insertedText);
 #endif
 }

 bool AXObjectCache::enqueuePasswordValueChangeNotification(AccessibilityObject* object)
 {
     if (!isPasswordFieldOrContainedByPasswordField(object))
         return false;

     AccessibilityObject* observableObject = object->observableObject();
     if (!observableObject) {
         ASSERT_NOT_REACHED();
         // return true even though the enqueue didn't happen because this is a password field and caller shouldn't post a notification
         return true;
     }

     m_passwordNotificationsToPost.add(observableObject);
     if (!m_passwordNotificationPostTimer.isActive())
         m_passwordNotificationPostTimer.startOneShot(accessibilityPasswordValueChangeNotificationInterval);

     return true;
 }

 void AXObjectCache::frameLoadingEventNotification(Frame* frame, AXLoadingEvent loadingEvent)
 {
     if (!frame)
         return;

     // Delegate on the right platform
     RenderView* contentRenderer = frame->contentRenderer();
     if (!contentRenderer)
         return;

     AccessibilityObject* obj = getOrCreate(contentRenderer);
     frameLoadingEventPlatformNotification(obj, loadingEvent);
 }

 void AXObjectCache::postLiveRegionChangeNotification(AccessibilityObject* object)
 {
     if (m_liveRegionChangedPostTimer.isActive())
         m_liveRegionChangedPostTimer.stop();

     if (!m_liveRegionObjectsSet.contains(object))
         m_liveRegionObjectsSet.add(object);

     m_liveRegionChangedPostTimer.startOneShot(accessibilityLiveRegionChangedNotificationInterval);
 }

 void AXObjectCache::liveRegionChangedNotificationPostTimerFired()
 {
     m_liveRegionChangedPostTimer.stop();

     if (m_liveRegionObjectsSet.isEmpty())
         return;

     for (auto& object : m_liveRegionObjectsSet)
         postNotification(object.get(), object->document(), AXObjectCache::AXLiveRegionChanged);
     m_liveRegionObjectsSet.clear();
 }

 static AccessibilityObject* firstFocusableChild(AccessibilityObject* obj)
 {
     if (!obj)
         return nullptr;

     for (auto* child = obj->firstChild(); child; child = child->nextSibling()) {
         if (child->canSetFocusAttribute())
             return child;
         if (AccessibilityObject* focusable = firstFocusableChild(child))
             return focusable;
     }
     return nullptr;
 }

 void AXObjectCache::focusModalNode()
 {
     if (m_focusModalNodeTimer.isActive())
         m_focusModalNodeTimer.stop();

     m_focusModalNodeTimer.startOneShot(accessibilityFocusModalNodeNotificationInterval);
 }

 void AXObjectCache::focusModalNodeTimerFired()
 {
     if (!m_currentModalNode)
         return;

     // Don't set focus if we are already focusing onto some element within
     // the dialog.
     if (m_currentModalNode->contains(document().focusedElement()))
         return;

     if (AccessibilityObject* currentModalNodeObject = getOrCreate(m_currentModalNode)) {
         if (AccessibilityObject* focusable = firstFocusableChild(currentModalNodeObject))
             focusable->setFocused(true);
     }
 }

 void AXObjectCache::handleScrollbarUpdate(ScrollView* view)
 {
     if (!view)
         return;

     // We don't want to create a scroll view from this method, only update an existing one.
     if (AccessibilityObject* scrollViewObject = get(view)) {
         stopCachingComputedObjectAttributes();
         scrollViewObject->updateChildrenIfNecessary();
     }
 }

 void AXObjectCache::handleAriaExpandedChange(Node* node)
 {
     if (AccessibilityObject* obj = get(node))
         obj->handleAriaExpandedChanged();
 }

 void AXObjectCache::handleActiveDescendantChanged(Node* node)
 {
     if (AccessibilityObject* obj = getOrCreate(node))
         obj->handleActiveDescendantChanged();
 }

 void AXObjectCache::handleAriaRoleChanged(Node* node)
 {
     stopCachingComputedObjectAttributes();

     // Don't make an AX object unless it's needed
     if (AccessibilityObject* obj = get(node)) {
         obj->updateAccessibilityRole();
         obj->notifyIfIgnoredValueChanged();
     }
 }

 void AXObjectCache::deferAttributeChangeIfNeeded(const QualifiedName& attrName, Element* element)
 {
     if (nodeAndRendererAreValid(element) && rendererNeedsDeferredUpdate(*element->renderer()))
         m_deferredAttributeChange.add(element, attrName);
     else
         handleAttributeChange(attrName, element);
 }

 bool AXObjectCache::shouldProcessAttributeChange(const QualifiedName& attrName, Element* element)
 {
     if (!element)
         return false;

     // aria-modal ends up affecting sub-trees that are being shown/hidden so it's likely that
     // an AT would not have accessed this node yet.
     if (attrName == aria_modalAttr)
         return true;

     // If an AXObject has yet to be created, then there's no need to process attribute changes.
     // Some of these notifications are processed on the parent, so allow that to proceed as well
     if (get(element) || get(element->parentNode()))
         return true;

     return false;
 }

 void AXObjectCache::handleAttributeChange(const QualifiedName& attrName, Element* element)
 {
     if (!shouldProcessAttributeChange(attrName, element))
         return;

     if (attrName == roleAttr)
         handleAriaRoleChanged(element);
     else if (attrName == altAttr || attrName == titleAttr)
         textChanged(element);
     else if (attrName == forAttr && is<HTMLLabelElement>(*element))
         labelChanged(element);
     else if (attrName == tabindexAttr)
         childrenChanged(element->parentNode(), element);

     if (!attrName.localName().string().startsWith("aria-"))
         return;

     if (attrName == aria_activedescendantAttr)
         handleActiveDescendantChanged(element);
     else if (attrName == aria_busyAttr)
         postNotification(element, AXObjectCache::AXElementBusyChanged);
     else if (attrName == aria_valuenowAttr || attrName == aria_valuetextAttr)
         postNotification(element, AXObjectCache::AXValueChanged);
     else if (attrName == aria_labelAttr || attrName == aria_labeledbyAttr || attrName == aria_labelledbyAttr)
         textChanged(element);
     else if (attrName == aria_checkedAttr)
         checkedStateChanged(element);
     else if (attrName == aria_selectedAttr)
         selectedChildrenChanged(element);
     else if (attrName == aria_expandedAttr)
         handleAriaExpandedChange(element);
     else if (attrName == aria_hiddenAttr)
         childrenChanged(element->parentNode(), element);
     else if (attrName == aria_invalidAttr)
         postNotification(element, AXObjectCache::AXInvalidStatusChanged);
     else if (attrName == aria_modalAttr)
         handleModalChange(element);
     else if (attrName == aria_currentAttr)
         postNotification(element, AXObjectCache::AXCurrentChanged);
     else if (attrName == aria_disabledAttr)
         postNotification(element, AXObjectCache::AXDisabledStateChanged);
     else if (attrName == aria_pressedAttr)
         postNotification(element, AXObjectCache::AXPressedStateChanged);
     else if (attrName == aria_readonlyAttr)
         postNotification(element, AXObjectCache::AXReadOnlyStatusChanged);
     else if (attrName == aria_requiredAttr)
         postNotification(element, AXObjectCache::AXRequiredStatusChanged);
     else
         postNotification(element, AXObjectCache::AXAriaAttributeChanged);
 }

 void AXObjectCache::handleModalChange(Node* node)
 {
     if (!is<Element>(node))
         return;

     if (!nodeHasRole(node, "dialog") && !nodeHasRole(node, "alertdialog"))
         return;

     stopCachingComputedObjectAttributes();
     if (equalLettersIgnoringASCIICase(downcast<Element>(*node).attributeWithoutSynchronization(aria_modalAttr), "true")) {
         // Add the newly modified node to the modal nodes set, and set it to be the current valid aria modal node.
         // We will recompute the current valid aria modal node in modalNode() when this node is not visible.
         m_modalNodesSet.add(node);
         m_currentModalNode = node;
     } else {
         // Remove the node from the modal nodes set. There might be other visible modal nodes, so we recompute here.
         m_modalNodesSet.remove(node);
         updateCurrentModalNode();
     }
     if (m_currentModalNode)
         focusModalNode();

     startCachingComputedObjectAttributesUntilTreeMutates();
 }

 void AXObjectCache::labelChanged(Element* element)
 {
     ASSERT(is<HTMLLabelElement>(*element));
     auto correspondingControl = downcast<HTMLLabelElement>(*element).control();
     deferTextChangedIfNeeded(correspondingControl.get());
 }

 void AXObjectCache::recomputeIsIgnored(RenderObject* renderer)
 {
     if (AccessibilityObject* obj = get(renderer))
         obj->notifyIfIgnoredValueChanged();
 }

 void AXObjectCache::startCachingComputedObjectAttributesUntilTreeMutates()
 {
     if (!m_computedObjectAttributeCache)
         m_computedObjectAttributeCache = makeUnique<AXComputedObjectAttributeCache>();
 }

 void AXObjectCache::stopCachingComputedObjectAttributes()
 {
     m_computedObjectAttributeCache = nullptr;
 }

 VisiblePosition AXObjectCache::visiblePositionForTextMarkerData(TextMarkerData& textMarkerData)
 {
     if (!isNodeInUse(textMarkerData.node))
         return VisiblePosition();

     // FIXME: Accessability should make it clear these are DOM-compliant offsets or store Position objects.
     VisiblePosition visiblePos = VisiblePosition(createLegacyEditingPosition(textMarkerData.node, textMarkerData.offset), textMarkerData.affinity);
     Position deepPos = visiblePos.deepEquivalent();
     if (deepPos.isNull())
         return VisiblePosition();

     RenderObject* renderer = deepPos.deprecatedNode()->renderer();
     if (!renderer)
         return VisiblePosition();

     AXObjectCache* cache = renderer->document().axObjectCache();
     if (cache && !cache->m_idsInUse.contains(textMarkerData.axID))
         return VisiblePosition();

     return visiblePos;
 }

 CharacterOffset AXObjectCache::characterOffsetForTextMarkerData(TextMarkerData& textMarkerData)
 {
     if (!isNodeInUse(textMarkerData.node))
         return CharacterOffset();

     if (textMarkerData.ignored)
         return CharacterOffset();

     CharacterOffset result = CharacterOffset(textMarkerData.node, textMarkerData.characterStartIndex, textMarkerData.characterOffset);
     // When we are at a line wrap and the VisiblePosition is upstream, it means the text marker is at the end of the previous line.
     // We use the previous CharacterOffset so that it will match the Range.
     if (textMarkerData.affinity == UPSTREAM)
         return previousCharacterOffset(result, false);
     return result;
 }

 CharacterOffset AXObjectCache::traverseToOffsetInRange(RefPtr<Range>range, int offset, TraverseOption option, bool stayWithinRange)
 {
     if (!range)
         return CharacterOffset();

     bool toNodeEnd = option & TraverseOptionToNodeEnd;
     bool validateOffset = option & TraverseOptionValidateOffset;
     bool doNotEnterTextControls = option & TraverseOptionDoNotEnterTextControls;

     int offsetInCharacter = 0;
     int cumulativeOffset = 0;
     int remaining = 0;
     int lastLength = 0;
     Node* currentNode = nullptr;
     bool finished = false;
     int lastStartOffset = 0;

     TextIterator iterator(*range, doNotEnterTextControls ? TextIteratorDefaultBehavior : TextIteratorEntersTextControls);

     // When the range has zero length, there might be replaced node or brTag that we need to increment the characterOffset.
     if (iterator.atEnd()) {
         currentNode = &range->startContainer();
         lastStartOffset = range->startOffset();
         if (offset > 0 || toNodeEnd) {
             if (AccessibilityObject::replacedNodeNeedsCharacter(currentNode) || (currentNode->renderer() && currentNode->renderer()->isBR()))
                 cumulativeOffset++;
             lastLength = cumulativeOffset;

             // When going backwards, stayWithinRange is false.
             // Here when we don't have any character to move and we are going backwards, we traverse to the previous node.
             if (!lastLength && toNodeEnd && !stayWithinRange) {
                 if (Node* preNode = previousNode(currentNode))
                     return traverseToOffsetInRange(rangeForNodeContents(preNode), offset, option);
                 return CharacterOffset();
             }
         }
     }

     // Sometimes text contents in a node are split into several iterations, so that iterator.range().startOffset()
     // might not be the total character count. Here we use a previousNode object to keep track of that.
     Node* previousNode = nullptr;
     for (; !iterator.atEnd(); iterator.advance()) {
         int currentLength = iterator.text().length();
         bool hasReplacedNodeOrBR = false;

         Node& node = iterator.range().start.container;
         currentNode = &node;

         // When currentLength == 0, we check if there's any replaced node.
         // If not, we skip the node with no length.
         if (!currentLength) {
             Node* childNode = iterator.node();
             if (AccessibilityObject::replacedNodeNeedsCharacter(childNode)) {
                 cumulativeOffset++;
                 currentLength++;
                 currentNode = childNode;
                 hasReplacedNodeOrBR = true;
             } else
                 continue;
         } else {
             // Ignore space, new line, tag node.
             if (currentLength == 1) {
                 if (isHTMLSpace(iterator.text()[0])) {
                     // If the node has BR tag, we want to set the currentNode to it.
                     Node* childNode = iterator.node();
                     if (childNode && childNode->renderer() && childNode->renderer()->isBR()) {
                         currentNode = childNode;
                         hasReplacedNodeOrBR = true;
                     } else if (auto* shadowHost = currentNode->shadowHost()) {
                         // Since we are entering text controls, we should set the currentNode
                         // to be the shadow host when there's no content.
                         if (nodeIsTextControl(shadowHost) && currentNode->isShadowRoot()) {
                             currentNode = shadowHost;
                             continue;
                         }
                     } else if (previousNode && previousNode->isTextNode() && previousNode->isDescendantOf(currentNode) && currentNode->hasTagName(pTag)) {
                         // TextIterator is emitting an extra newline after the <p> element. We should
                         // ignore that since the extra text node is not in the DOM tree.
                         currentNode = previousNode;
                         continue;
                     } else if (currentNode != previousNode) {
                         // We should set the start offset and length for the current node in case this is the last iteration.
                         lastStartOffset = 1;
                         lastLength = 0;
                         continue;
                     }
                 }
             }
             cumulativeOffset += currentLength;
         }

         if (currentNode == previousNode) {
             lastLength += currentLength;
             lastStartOffset = iterator.range().end.offset - lastLength;
         } else {
             lastLength = currentLength;
             lastStartOffset = hasReplacedNodeOrBR ? 0 : iterator.range().start.offset;
         }

         // Break early if we have advanced enough characters.
         bool offsetLimitReached = validateOffset ? cumulativeOffset + lastStartOffset >= offset : cumulativeOffset >= offset;
         if (!toNodeEnd && offsetLimitReached) {
             offsetInCharacter = validateOffset ? std::max(offset - lastStartOffset, 0) : offset - (cumulativeOffset - lastLength);
             finished = true;
             break;
         }
         previousNode = currentNode;
     }

     if (!finished) {
         offsetInCharacter = lastLength;
         if (!toNodeEnd)
             remaining = offset - cumulativeOffset;
     }

     // Sometimes when we are getting the end CharacterOffset of a line range, the TextIterator will emit an extra space at the end
     // and make the character count greater than the Range's end offset.
     if (toNodeEnd && currentNode->isTextNode() && currentNode == &range->endContainer() && static_cast<int>(range->endOffset()) < lastStartOffset + offsetInCharacter)
         offsetInCharacter = range->endOffset() - lastStartOffset;

     return CharacterOffset(currentNode, lastStartOffset, offsetInCharacter, remaining);
 }

 int AXObjectCache::lengthForRange(Range* range)
 {
     if (!range)
         return -1;
     int length = 0;
     for (TextIterator it(*range); !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
             if (AccessibilityObject::replacedNodeNeedsCharacter(it.node()))
                 ++length;
         }
     }
     return length;
 }

 RefPtr<Range> AXObjectCache::rangeForNodeContents(Node* node)
 {
     if (!node)
         return nullptr;
     Document* document = &node->document();
     if (!document)
         return nullptr;
     auto range = Range::create(*document);
     if (AccessibilityObject::replacedNodeNeedsCharacter(node)) {
         // For replaced nodes without children, the node itself is included in the range.
         if (range->selectNode(*node).hasException())
             return nullptr;
     } else {
         if (range->selectNodeContents(*node).hasException())
             return nullptr;
     }
     return range;
 }

 Optional<SimpleRange> AXObjectCache::rangeMatchesTextNearRange(const SimpleRange& originalRange, const String& matchText)
 {
     // Create a large enough range for searching the text within.
     unsigned textLength = matchText.length();
     auto startPosition = visiblePositionForPositionWithOffset(createLegacyEditingPosition(originalRange.start), -textLength);
     auto endPosition = visiblePositionForPositionWithOffset(createLegacyEditingPosition(originalRange.start), 2 * textLength);
     if (startPosition.isNull())
         startPosition = firstPositionInOrBeforeNode(originalRange.start.container.ptr());
     if (endPosition.isNull())
         endPosition = lastPositionInOrAfterNode(originalRange.end.container.ptr());

     auto searchRange = SimpleRange { *makeBoundaryPoint(startPosition), *makeBoundaryPoint(endPosition) };
     if (searchRange.collapsed())
         return WTF::nullopt;

     auto targetOffset = characterCount({ searchRange.start, originalRange.start }, TextIteratorEmitsCharactersBetweenAllVisiblePositions);
     return findClosestPlainText(searchRange, matchText, { }, targetOffset);
 }

 static bool isReplacedNodeOrBR(Node* node)
 {
     return node && (AccessibilityObject::replacedNodeNeedsCharacter(node) || node->hasTagName(brTag));
 }

 static bool characterOffsetsInOrder(const CharacterOffset& characterOffset1, const CharacterOffset& characterOffset2)
 {
     if (characterOffset1.isNull() || characterOffset2.isNull())
         return false;

     if (characterOffset1.node == characterOffset2.node)
         return characterOffset1.offset <= characterOffset2.offset;

     Node* node1 = characterOffset1.node;
     Node* node2 = characterOffset2.node;
     if (!node1->isCharacterDataNode() && !isReplacedNodeOrBR(node1) && node1->hasChildNodes())
         node1 = node1->traverseToChildAt(characterOffset1.offset);
     if (!node2->isCharacterDataNode() && !isReplacedNodeOrBR(node2) && node2->hasChildNodes())
         node2 = node2->traverseToChildAt(characterOffset2.offset);

     if (!node1 || !node2)
         return false;

     RefPtr<Range> range1 = AXObjectCache::rangeForNodeContents(node1);
     RefPtr<Range> range2 = AXObjectCache::rangeForNodeContents(node2);

     if (!range2)
         return true;
     if (!range1)
         return false;
     auto result = range1->compareBoundaryPoints(Range::START_TO_START, *range2);
     if (result.hasException())
         return true;
     return result.releaseReturnValue() <= 0;
 }

 static Node* resetNodeAndOffsetForReplacedNode(Node* replacedNode, int& offset, int characterCount)
 {
     // Use this function to include the replaced node itself in the range we are creating.
     auto nodeRange = AXObjectCache::rangeForNodeContents(replacedNode);
     if (!nodeRange)
         return nullptr;
     bool isInNode = static_cast<unsigned>(characterCount) <= WebCore::characterCount(*nodeRange);
     offset = replacedNode->computeNodeIndex() + (isInNode ? 0 : 1);
     return replacedNode->parentNode();
 }

 static bool setRangeStartOrEndWithCharacterOffset(Range& range, const CharacterOffset& characterOffset, bool isStart)
 {
     if (characterOffset.isNull())
         return false;

     int offset = characterOffset.startIndex + characterOffset.offset;
     Node* node = characterOffset.node;
     ASSERT(node);

     bool replacedNodeOrBR = isReplacedNodeOrBR(node);
     // For the non text node that has no children, we should create the range with its parent, otherwise the range would be collapsed.
     // Example: <div contenteditable="true"></div>, we want the range to include the div element.
     bool noChildren = !replacedNodeOrBR && !node->isTextNode() && !node->hasChildNodes();
     int characterCount = noChildren ? (isStart ? 0 : 1) : characterOffset.offset;

     if (replacedNodeOrBR || noChildren)
         node = resetNodeAndOffsetForReplacedNode(node, offset, characterCount);

     if (!node)
         return false;

     if (isStart) {
         if (range.setStart(*node, offset).hasException())
             return false;
     } else {
         if (range.setEnd(*node, offset).hasException())
             return false;
     }

     return true;
 }

 RefPtr<Range> AXObjectCache::rangeForUnorderedCharacterOffsets(const CharacterOffset& characterOffset1, const CharacterOffset& characterOffset2)
 {
     if (characterOffset1.isNull() || characterOffset2.isNull())
         return nullptr;

     bool alreadyInOrder = characterOffsetsInOrder(characterOffset1, characterOffset2);
     CharacterOffset startCharacterOffset = alreadyInOrder ? characterOffset1 : characterOffset2;
     CharacterOffset endCharacterOffset = alreadyInOrder ? characterOffset2 : characterOffset1;

     auto result = Range::create(m_document);
     if (!setRangeStartOrEndWithCharacterOffset(result, startCharacterOffset, true))
         return nullptr;
     if (!setRangeStartOrEndWithCharacterOffset(result, endCharacterOffset, false))
         return nullptr;
     return result;
 }

 void AXObjectCache::setTextMarkerDataWithCharacterOffset(TextMarkerData& textMarkerData, const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull())
         return;

     Node* domNode = characterOffset.node;
     if (is<HTMLInputElement>(*domNode) && downcast<HTMLInputElement>(*domNode).isPasswordField()) {
         textMarkerData.ignored = true;
         return;
     }

     RefPtr<AccessibilityObject> obj = this->getOrCreate(domNode);
     if (!obj)
         return;

     // Convert to visible position.
     VisiblePosition visiblePosition = visiblePositionFromCharacterOffset(characterOffset);
     int vpOffset = 0;
     if (!visiblePosition.isNull()) {
         Position deepPos = visiblePosition.deepEquivalent();
         vpOffset = deepPos.deprecatedEditingOffset();
     }

     textMarkerData.axID = obj.get()->objectID();
     textMarkerData.node = domNode;
     textMarkerData.characterOffset = characterOffset.offset;
     textMarkerData.characterStartIndex = characterOffset.startIndex;
     textMarkerData.offset = vpOffset;
     textMarkerData.affinity = visiblePosition.affinity();

     this->setNodeInUse(domNode);
 }

 CharacterOffset AXObjectCache::startOrEndCharacterOffsetForRange(RefPtr<Range> range, bool isStart, bool enterTextControls)
 {
     if (!range)
         return CharacterOffset();

     // When getting the end CharacterOffset at node boundary, we don't want to collapse to the previous node.
     if (!isStart && !range->endOffset())
         return characterOffsetForNodeAndOffset(range->endContainer(), 0, TraverseOptionIncludeStart);

     // If it's end text marker, we want to go to the end of the range, and stay within the range.
     bool stayWithinRange = !isStart;

     Node& endNode = range->endContainer();
     if (endNode.isCharacterDataNode() && !isStart)
         return traverseToOffsetInRange(rangeForNodeContents(&endNode), range->endOffset(), TraverseOptionValidateOffset);

     Ref<Range> copyRange = *range;
     // Change the start of the range, so the character offset starts from node beginning.
     int offset = 0;
     Node& node = copyRange->startContainer();
     if (node.isCharacterDataNode()) {
         CharacterOffset nodeStartOffset = traverseToOffsetInRange(rangeForNodeContents(&node), range->startOffset(), TraverseOptionValidateOffset);
         if (isStart)
             return nodeStartOffset;
         copyRange = Range::create(range->ownerDocument(), &range->startContainer(), 0, &range->endContainer(), range->endOffset());
         offset += nodeStartOffset.offset;
     }

     TraverseOption options = isStart ? TraverseOptionDefault : TraverseOptionToNodeEnd;
     if (!enterTextControls)
         options = static_cast<TraverseOption>(options | TraverseOptionDoNotEnterTextControls);
     return traverseToOffsetInRange(WTFMove(copyRange), offset, options, stayWithinRange);
 }

 void AXObjectCache::startOrEndTextMarkerDataForRange(TextMarkerData& textMarkerData, RefPtr<Range> range, bool isStart)
 {
     // This memory must be zero'd so instances of TextMarkerData can be tested for byte-equivalence.
     // Warning: This is risky and bad because TextMarkerData is a nontrivial type.
     memset(static_cast<void*>(&textMarkerData), 0, sizeof(TextMarkerData));

     CharacterOffset characterOffset = startOrEndCharacterOffsetForRange(range, isStart);
     if (characterOffset.isNull())
         return;

     setTextMarkerDataWithCharacterOffset(textMarkerData, characterOffset);
 }

 CharacterOffset AXObjectCache::characterOffsetForNodeAndOffset(Node& node, int offset, TraverseOption option)
 {
     Node* domNode = &node;
     if (!domNode)
         return CharacterOffset();

     bool toNodeEnd = option & TraverseOptionToNodeEnd;
     bool includeStart = option & TraverseOptionIncludeStart;

     // ignoreStart is used to determine if we should go to previous node or
     // stay in current node when offset is 0.
     if (!toNodeEnd && (offset < 0 || (!offset && !includeStart))) {
         // Set the offset to the amount of characters we need to go backwards.
         offset = - offset;
         CharacterOffset charOffset = CharacterOffset();
         while (offset >= 0 && charOffset.offset <= offset) {
             offset -= charOffset.offset;
             domNode = previousNode(domNode);
             if (domNode) {
                 charOffset = characterOffsetForNodeAndOffset(*domNode, 0, TraverseOptionToNodeEnd);
             } else
                 return CharacterOffset();
             if (charOffset.offset == offset)
                 break;
         }
         if (offset > 0)
             charOffset = characterOffsetForNodeAndOffset(*charOffset.node, charOffset.offset - offset, TraverseOptionIncludeStart);
         return charOffset;
     }

     RefPtr<Range> range = rangeForNodeContents(domNode);

     // Traverse the offset amount of characters forward and see if there's remaining offsets.
     // Keep traversing to the next node when there's remaining offsets.
     CharacterOffset characterOffset = traverseToOffsetInRange(range, offset, option);
     while (!characterOffset.isNull() && characterOffset.remaining() && !toNodeEnd) {
         domNode = nextNode(domNode);
         if (!domNode)
             return CharacterOffset();
         range = rangeForNodeContents(domNode);
         characterOffset = traverseToOffsetInRange(range, characterOffset.remaining(), option);
     }

     return characterOffset;
 }

 void AXObjectCache::textMarkerDataForCharacterOffset(TextMarkerData& textMarkerData, const CharacterOffset& characterOffset)
 {
     // This memory must be zero'd so instances of TextMarkerData can be tested for byte-equivalence.
     // Warning: This is risky and bad because TextMarkerData is a nontrivial type.
     memset(static_cast<void*>(&textMarkerData), 0, sizeof(TextMarkerData));

     setTextMarkerDataWithCharacterOffset(textMarkerData, characterOffset);
 }

 bool AXObjectCache::shouldSkipBoundary(const CharacterOffset& previous, const CharacterOffset& next)
 {
     // Match the behavior of VisiblePosition, we should skip the node boundary when there's no visual space or new line character.
     if (previous.isNull() || next.isNull())
         return false;

     if (previous.node == next.node)
         return false;

     if (next.startIndex > 0 || next.offset > 0)
         return false;

     CharacterOffset newLine = startCharacterOffsetOfLine(next);
     if (next.isEqual(newLine))
         return false;

     return true;
 }

 void AXObjectCache::textMarkerDataForNextCharacterOffset(TextMarkerData& textMarkerData, const CharacterOffset& characterOffset)
 {
     CharacterOffset next = characterOffset;
     CharacterOffset previous = characterOffset;
     bool shouldContinue;
     do {
         shouldContinue = false;
         next = nextCharacterOffset(next, false);
         if (shouldSkipBoundary(previous, next))
             next = nextCharacterOffset(next, false);
         textMarkerDataForCharacterOffset(textMarkerData, next);

         // We should skip next CharactetOffset if it's visually the same.
         if (!lengthForRange(rangeForUnorderedCharacterOffsets(previous, next).get()))
             shouldContinue = true;
         previous = next;
     } while (textMarkerData.ignored || shouldContinue);
 }

 void AXObjectCache::textMarkerDataForPreviousCharacterOffset(TextMarkerData& textMarkerData, const CharacterOffset& characterOffset)
 {
     CharacterOffset previous = characterOffset;
     CharacterOffset next = characterOffset;
     bool shouldContinue;
     do {
         shouldContinue = false;
         previous = previousCharacterOffset(previous, false);
         textMarkerDataForCharacterOffset(textMarkerData, previous);

         // We should skip previous CharactetOffset if it's visually the same.
         if (!lengthForRange(rangeForUnorderedCharacterOffsets(previous, next).get()))
             shouldContinue = true;
         next = previous;
     } while (textMarkerData.ignored || shouldContinue);
 }

 Node* AXObjectCache::nextNode(Node* node) const
 {
     if (!node)
         return nullptr;

     return NodeTraversal::nextSkippingChildren(*node);
 }

 Node* AXObjectCache::previousNode(Node* node) const
 {
     if (!node)
         return nullptr;

     // First child of body shouldn't have previous node.
     if (node->parentNode() && node->parentNode()->renderer() && node->parentNode()->renderer()->isBody() && !node->previousSibling())
         return nullptr;

     return NodeTraversal::previousSkippingChildren(*node);
 }

 VisiblePosition AXObjectCache::visiblePositionFromCharacterOffset(const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull())
         return VisiblePosition();

     // Create a collapsed range and use that to form a VisiblePosition, so that the case with
     // composed characters will be covered.
     auto range = rangeForUnorderedCharacterOffsets(characterOffset, characterOffset);
     return range ? VisiblePosition(range->startPosition()) : VisiblePosition();
 }

 CharacterOffset AXObjectCache::characterOffsetFromVisiblePosition(const VisiblePosition& visiblePos)
 {
     if (visiblePos.isNull())
         return CharacterOffset();

     Position deepPos = visiblePos.deepEquivalent();
     Node* domNode = deepPos.deprecatedNode();
     ASSERT(domNode);

     if (domNode->isCharacterDataNode())
         return traverseToOffsetInRange(rangeForNodeContents(domNode), deepPos.deprecatedEditingOffset(), TraverseOptionValidateOffset);

     RefPtr<AccessibilityObject> obj = this->getOrCreate(domNode);
     if (!obj)
         return CharacterOffset();

     // Use nextVisiblePosition to calculate how many characters we need to traverse to the current position.
     VisiblePositionRange visiblePositionRange = obj->visiblePositionRange();
     VisiblePosition visiblePosition = visiblePositionRange.start;
     int characterOffset = 0;
     Position currentPosition = visiblePosition.deepEquivalent();

     VisiblePosition previousVisiblePos;
     while (!currentPosition.isNull() && !deepPos.equals(currentPosition)) {
         previousVisiblePos = visiblePosition;
         visiblePosition = obj->nextVisiblePosition(visiblePosition);
         currentPosition = visiblePosition.deepEquivalent();
         Position previousPosition = previousVisiblePos.deepEquivalent();
         // Sometimes nextVisiblePosition will give the same VisiblePostion,
         // we break here to avoid infinite loop.
         if (currentPosition.equals(previousPosition))
             break;
         characterOffset++;

         // When VisiblePostion moves to next node, it will count the leading line break as
         // 1 offset, which we shouldn't include in CharacterOffset.
         if (currentPosition.deprecatedNode() != previousPosition.deprecatedNode()) {
             if (visiblePosition.characterBefore() == '\n')
                 characterOffset--;
         } else {
             // Sometimes VisiblePosition will move multiple characters, like emoji.
             if (currentPosition.deprecatedNode()->isCharacterDataNode())
                 characterOffset += currentPosition.offsetInContainerNode() - previousPosition.offsetInContainerNode() - 1;
         }
     }

     // Sometimes when the node is a replaced node and is ignored in accessibility, we get a wrong CharacterOffset from it.
     CharacterOffset result = traverseToOffsetInRange(rangeForNodeContents(obj->node()), characterOffset);
     if (result.remainingOffset > 0 && !result.isNull() && isRendererReplacedElement(result.node->renderer()))
         result.offset += result.remainingOffset;
     return result;
 }

 AccessibilityObject* AXObjectCache::accessibilityObjectForTextMarkerData(TextMarkerData& textMarkerData)
 {
     if (!isNodeInUse(textMarkerData.node))
         return nullptr;

     Node* domNode = textMarkerData.node;
     return this->getOrCreate(domNode);
 }

 Optional<TextMarkerData> AXObjectCache::textMarkerDataForVisiblePosition(const VisiblePosition& visiblePos)
 {
     if (visiblePos.isNull())
         return WTF::nullopt;

     Position deepPos = visiblePos.deepEquivalent();
     Node* domNode = deepPos.deprecatedNode();
     ASSERT(domNode);
     if (!domNode)
         return WTF::nullopt;

     if (is<HTMLInputElement>(*domNode) && downcast<HTMLInputElement>(*domNode).isPasswordField())
         return WTF::nullopt;

     // If the visible position has an anchor type referring to a node other than the anchored node, we should
     // set the text marker data with CharacterOffset so that the offset will correspond to the node.
     CharacterOffset characterOffset = characterOffsetFromVisiblePosition(visiblePos);
     if (deepPos.anchorType() == Position::PositionIsAfterAnchor || deepPos.anchorType() == Position::PositionIsAfterChildren) {
         TextMarkerData textMarkerData;
         textMarkerDataForCharacterOffset(textMarkerData, characterOffset);
         return textMarkerData;
     }

     // find or create an accessibility object for this node
     AXObjectCache* cache = domNode->document().axObjectCache();
     if (!cache)
         return WTF::nullopt;
     RefPtr<AccessibilityObject> obj = cache->getOrCreate(domNode);

     // This memory must be zero'd so instances of TextMarkerData can be tested for byte-equivalence.
     // Warning: This is risky and bad because TextMarkerData is a nontrivial type.
     TextMarkerData textMarkerData;
     memset(static_cast<void*>(&textMarkerData), 0, sizeof(TextMarkerData));

     textMarkerData.axID = obj.get()->objectID();
     textMarkerData.node = domNode;
     textMarkerData.offset = deepPos.deprecatedEditingOffset();
     textMarkerData.affinity = visiblePos.affinity();

     textMarkerData.characterOffset = characterOffset.offset;
     textMarkerData.characterStartIndex = characterOffset.startIndex;

     cache->setNodeInUse(domNode);

     return textMarkerData;
 }

 // This function exits as a performance optimization to avoid a synchronous layout.
 Optional<TextMarkerData> AXObjectCache::textMarkerDataForFirstPositionInTextControl(HTMLTextFormControlElement& textControl)
 {
     if (is<HTMLInputElement>(textControl) && downcast<HTMLInputElement>(textControl).isPasswordField())
         return WTF::nullopt;

     AXObjectCache* cache = textControl.document().axObjectCache();
     if (!cache)
         return WTF::nullopt;

     RefPtr<AccessibilityObject> obj = cache->getOrCreate(&textControl);
     if (!obj)
         return WTF::nullopt;

     // This memory must be zero'd so instances of TextMarkerData can be tested for byte-equivalence.
     // Warning: This is risky and bad because TextMarkerData is a nontrivial type.
     TextMarkerData textMarkerData;
     memset(static_cast<void*>(&textMarkerData), 0, sizeof(TextMarkerData));

     textMarkerData.axID = obj.get()->objectID();
     textMarkerData.node = &textControl;

     cache->setNodeInUse(&textControl);

     return textMarkerData;
 }

 CharacterOffset AXObjectCache::nextCharacterOffset(const CharacterOffset& characterOffset, bool ignoreNextNodeStart)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     // We don't always move one 'character' at a time since there might be composed characters.
     unsigned nextOffset = Position::uncheckedNextOffset(characterOffset.node, characterOffset.offset);
     CharacterOffset next = characterOffsetForNodeAndOffset(*characterOffset.node, nextOffset);

     // To be consistent with VisiblePosition, we should consider the case that current node end to next node start counts 1 offset.
     if (!ignoreNextNodeStart && !next.isNull() && !isReplacedNodeOrBR(next.node) && next.node != characterOffset.node) {
         if (auto range = rangeForUnorderedCharacterOffsets(characterOffset, next)) {
             auto length = characterCount(*range);
             if (length > nextOffset - characterOffset.offset)
                 next = characterOffsetForNodeAndOffset(*next.node, 0, TraverseOptionIncludeStart);
         }
     }

     return next;
 }

 CharacterOffset AXObjectCache::previousCharacterOffset(const CharacterOffset& characterOffset, bool ignorePreviousNodeEnd)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     // To be consistent with VisiblePosition, we should consider the case that current node start to previous node end counts 1 offset.
     if (!ignorePreviousNodeEnd && !characterOffset.offset)
         return characterOffsetForNodeAndOffset(*characterOffset.node, 0);

     // We don't always move one 'character' a time since there might be composed characters.
     int previousOffset = Position::uncheckedPreviousOffset(characterOffset.node, characterOffset.offset);
     return characterOffsetForNodeAndOffset(*characterOffset.node, previousOffset, TraverseOptionIncludeStart);
 }

 CharacterOffset AXObjectCache::startCharacterOffsetOfWord(const CharacterOffset& characterOffset, EWordSide side)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     CharacterOffset c = characterOffset;
     if (side == RightWordIfOnBoundary) {
         CharacterOffset endOfParagraph = endCharacterOffsetOfParagraph(c);
         if (c.isEqual(endOfParagraph))
             return c;

         // We should consider the node boundary that splits words. Otherwise VoiceOver won't see it as space.
         c = nextCharacterOffset(characterOffset, false);
         if (shouldSkipBoundary(characterOffset, c))
             c = nextCharacterOffset(c, false);
         if (c.isNull())
             return characterOffset;
     }

     return previousBoundary(c, startWordBoundary);
 }

 CharacterOffset AXObjectCache::endCharacterOffsetOfWord(const CharacterOffset& characterOffset, EWordSide side)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     CharacterOffset c = characterOffset;
     if (side == LeftWordIfOnBoundary) {
         CharacterOffset startOfParagraph = startCharacterOffsetOfParagraph(c);
         if (c.isEqual(startOfParagraph))
             return c;

         c = previousCharacterOffset(characterOffset);
         if (c.isNull())
             return characterOffset;
     } else {
         CharacterOffset endOfParagraph = endCharacterOffsetOfParagraph(characterOffset);
         if (characterOffset.isEqual(endOfParagraph))
             return characterOffset;
     }

     return nextBoundary(c, endWordBoundary);
 }

 CharacterOffset AXObjectCache::previousWordStartCharacterOffset(const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     CharacterOffset previousOffset = previousCharacterOffset(characterOffset);
     if (previousOffset.isNull())
         return CharacterOffset();

     return startCharacterOffsetOfWord(previousOffset, RightWordIfOnBoundary);
 }

 CharacterOffset AXObjectCache::nextWordEndCharacterOffset(const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     CharacterOffset nextOffset = nextCharacterOffset(characterOffset);
     if (nextOffset.isNull())
         return CharacterOffset();

     return endCharacterOffsetOfWord(nextOffset, LeftWordIfOnBoundary);
 }

 RefPtr<Range> AXObjectCache::leftWordRange(const CharacterOffset& characterOffset)
 {
     CharacterOffset start = startCharacterOffsetOfWord(characterOffset, LeftWordIfOnBoundary);
     CharacterOffset end = endCharacterOffsetOfWord(start);
     return rangeForUnorderedCharacterOffsets(start, end);
 }

 RefPtr<Range> AXObjectCache::rightWordRange(const CharacterOffset& characterOffset)
 {
     CharacterOffset start = startCharacterOffsetOfWord(characterOffset, RightWordIfOnBoundary);
     CharacterOffset end = endCharacterOffsetOfWord(start);
     return rangeForUnorderedCharacterOffsets(start, end);
 }

 static UChar32 characterForCharacterOffset(const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull() || !characterOffset.node->isTextNode())
         return 0;

     UChar32 ch = 0;
     unsigned offset = characterOffset.startIndex + characterOffset.offset;
     if (offset < characterOffset.node->textContent().length()) {
 // FIXME: Remove IGNORE_CLANG_WARNINGS macros once one of <rdar://problem/58615489&58615391> is fixed.
 IGNORE_CLANG_WARNINGS_BEGIN("conditional-uninitialized")
         U16_NEXT(characterOffset.node->textContent(), offset, characterOffset.node->textContent().length(), ch);
 IGNORE_CLANG_WARNINGS_END
     }
     return ch;
 }

 UChar32 AXObjectCache::characterAfter(const CharacterOffset& characterOffset)
 {
     return characterForCharacterOffset(nextCharacterOffset(characterOffset));
 }

 UChar32 AXObjectCache::characterBefore(const CharacterOffset& characterOffset)
 {
     return characterForCharacterOffset(characterOffset);
 }

 static bool characterOffsetNodeIsBR(const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull())
         return false;

     return characterOffset.node->hasTagName(brTag);
 }

 static Node* parentEditingBoundary(Node* node)
 {
     if (!node)
         return nullptr;

     Node* documentElement = node->document().documentElement();
     if (!documentElement)
         return nullptr;

     Node* boundary = node;
     while (boundary != documentElement && boundary->nonShadowBoundaryParentNode() && node->hasEditableStyle() == boundary->parentNode()->hasEditableStyle())
         boundary = boundary->nonShadowBoundaryParentNode();

     return boundary;
 }

 CharacterOffset AXObjectCache::nextBoundary(const CharacterOffset& characterOffset, BoundarySearchFunction searchFunction)
 {
     if (characterOffset.isNull())
         return { };

     Node* boundary = parentEditingBoundary(characterOffset.node);
     if (!boundary)
         return { };

     RefPtr<Range> searchRange = rangeForNodeContents(boundary);
     if (!searchRange)
         return { };

     Vector<UChar, 1024> string;
     unsigned prefixLength = 0;

     if (requiresContextForWordBoundary(characterAfter(characterOffset))) {
         auto backwardsScanRange = boundary->document().createRange();
         if (!setRangeStartOrEndWithCharacterOffset(backwardsScanRange, characterOffset, false))
             return { };
         prefixLength = prefixLengthForRange(backwardsScanRange, string);
     }

     if (!setRangeStartOrEndWithCharacterOffset(*searchRange, characterOffset, true))
         return { };
     CharacterOffset end = startOrEndCharacterOffsetForRange(searchRange, false);

     TextIterator it(*searchRange, TextIteratorEmitsObjectReplacementCharacters);
     unsigned next = forwardSearchForBoundaryWithTextIterator(it, string, prefixLength, searchFunction);

     if (it.atEnd() && next == string.size())
         return end;

     // We should consider the node boundary that splits words.
     if (searchFunction == endWordBoundary && next - prefixLength == 1)
         return nextCharacterOffset(characterOffset, false);

     // The endSentenceBoundary function will include a line break at the end of the sentence.
     if (searchFunction == endSentenceBoundary && string[next - 1] == '\n')
         next--;

     if (next > prefixLength)
         return characterOffsetForNodeAndOffset(*characterOffset.node, characterOffset.offset + next - prefixLength);

     return characterOffset;
 }

 // FIXME: Share code with the one in VisibleUnits.cpp.
 CharacterOffset AXObjectCache::previousBoundary(const CharacterOffset& characterOffset, BoundarySearchFunction searchFunction, NeedsContextAtParagraphStart needsContextAtParagraphStart)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     Node* boundary = parentEditingBoundary(characterOffset.node);
     if (!boundary)
         return CharacterOffset();

     RefPtr<Range> searchRange = rangeForNodeContents(boundary);
     Vector<UChar, 1024> string;
     unsigned suffixLength = 0;

     if (needsContextAtParagraphStart == NeedsContextAtParagraphStart::Yes && startCharacterOffsetOfParagraph(characterOffset).isEqual(characterOffset)) {
         auto forwardsScanRange = boundary->document().createRange();
         auto endOfCurrentParagraph = endCharacterOffsetOfParagraph(characterOffset);
         if (!setRangeStartOrEndWithCharacterOffset(forwardsScanRange, characterOffset, true))
             return { };
         if (!setRangeStartOrEndWithCharacterOffset(forwardsScanRange, endOfCurrentParagraph, false))
             return { };
         for (TextIterator forwardsIterator(forwardsScanRange); !forwardsIterator.atEnd(); forwardsIterator.advance())
             append(string, forwardsIterator.text());
         suffixLength = string.size();
     } else if (requiresContextForWordBoundary(characterBefore(characterOffset))) {
         auto forwardsScanRange = boundary->document().createRange();
         if (forwardsScanRange->setEndAfter(*boundary).hasException())
             return { };
         if (!setRangeStartOrEndWithCharacterOffset(forwardsScanRange, characterOffset, true))
             return { };
         suffixLength = suffixLengthForRange(forwardsScanRange, string);
     }

     if (!setRangeStartOrEndWithCharacterOffset(*searchRange, characterOffset, false))
         return { };
     CharacterOffset start = startOrEndCharacterOffsetForRange(searchRange, true);

     SimplifiedBackwardsTextIterator it(*searchRange);
     unsigned next = backwardSearchForBoundaryWithTextIterator(it, string, suffixLength, searchFunction);

     if (!next)
         return it.atEnd() ? start : characterOffset;

     auto& node = it.atEnd() ? searchRange->startContainer() : it.range().start.container.get();

     // SimplifiedBackwardsTextIterator ignores replaced elements.
     if (AccessibilityObject::replacedNodeNeedsCharacter(characterOffset.node))
         return characterOffsetForNodeAndOffset(*characterOffset.node, 0);
     Node* nextSibling = node.nextSibling();
     if (&node != characterOffset.node && AccessibilityObject::replacedNodeNeedsCharacter(nextSibling))
         return startOrEndCharacterOffsetForRange(rangeForNodeContents(nextSibling), false);

     if ((!suffixLength && node.isTextNode() && static_cast<int>(next) <= node.maxCharacterOffset()) || (node.renderer() && node.renderer()->isBR() && !next)) {
         // The next variable contains a usable index into a text node
         if (node.isTextNode())
             return traverseToOffsetInRange(rangeForNodeContents(&node), next, TraverseOptionValidateOffset);
         return characterOffsetForNodeAndOffset(node, next, TraverseOptionIncludeStart);
     }

     int characterCount = characterOffset.offset;
     if (next < string.size() - suffixLength)
         characterCount -= string.size() - suffixLength - next;
     // We don't want to go to the previous node if the node is at the start of a new line.
     if (characterCount < 0 && (characterOffsetNodeIsBR(characterOffset) || string[string.size() - suffixLength - 1] == '\n'))
         characterCount = 0;
     return characterOffsetForNodeAndOffset(*characterOffset.node, characterCount, TraverseOptionIncludeStart);
 }

 CharacterOffset AXObjectCache::startCharacterOffsetOfParagraph(const CharacterOffset& characterOffset, EditingBoundaryCrossingRule boundaryCrossingRule)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     auto* startNode = characterOffset.node;

     if (isRenderedAsNonInlineTableImageOrHR(startNode))
         return startOrEndCharacterOffsetForRange(rangeForNodeContents(startNode), true);

     auto* startBlock = enclosingBlock(startNode);
     int offset = characterOffset.startIndex + characterOffset.offset;
     auto* highestRoot = highestEditableRoot(firstPositionInOrBeforeNode(startNode));
     Position::AnchorType type = Position::PositionIsOffsetInAnchor;

     auto* node = findStartOfParagraph(startNode, highestRoot, startBlock, offset, type, boundaryCrossingRule);

     if (type == Position::PositionIsOffsetInAnchor)
         return characterOffsetForNodeAndOffset(*node, offset, TraverseOptionIncludeStart);

     return startOrEndCharacterOffsetForRange(rangeForNodeContents(node), true);
 }

 CharacterOffset AXObjectCache::endCharacterOffsetOfParagraph(const CharacterOffset& characterOffset, EditingBoundaryCrossingRule boundaryCrossingRule)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     Node* startNode = characterOffset.node;
     if (isRenderedAsNonInlineTableImageOrHR(startNode))
         return startOrEndCharacterOffsetForRange(rangeForNodeContents(startNode), false);

     Node* stayInsideBlock = enclosingBlock(startNode);
     int offset = characterOffset.startIndex + characterOffset.offset;
     Node* highestRoot = highestEditableRoot(firstPositionInOrBeforeNode(startNode));
     Position::AnchorType type = Position::PositionIsOffsetInAnchor;

     Node* node = findEndOfParagraph(startNode, highestRoot, stayInsideBlock, offset, type, boundaryCrossingRule);
     if (type == Position::PositionIsOffsetInAnchor) {
         if (node->isTextNode()) {
             CharacterOffset startOffset = startOrEndCharacterOffsetForRange(rangeForNodeContents(node), true);
             offset -= startOffset.startIndex;
         }
         return characterOffsetForNodeAndOffset(*node, offset, TraverseOptionIncludeStart);
     }

     return startOrEndCharacterOffsetForRange(rangeForNodeContents(node), false);
 }

 RefPtr<Range> AXObjectCache::paragraphForCharacterOffset(const CharacterOffset& characterOffset)
 {
     CharacterOffset start = startCharacterOffsetOfParagraph(characterOffset);
     CharacterOffset end = endCharacterOffsetOfParagraph(start);

     return rangeForUnorderedCharacterOffsets(start, end);
 }

 CharacterOffset AXObjectCache::nextParagraphEndCharacterOffset(const CharacterOffset& characterOffset)
 {
     // make sure we move off of a paragraph end
     CharacterOffset next = nextCharacterOffset(characterOffset);

     // We should skip the following BR node.
     if (characterOffsetNodeIsBR(next) && !characterOffsetNodeIsBR(characterOffset))
         next = nextCharacterOffset(next);

     return endCharacterOffsetOfParagraph(next);
 }

 CharacterOffset AXObjectCache::previousParagraphStartCharacterOffset(const CharacterOffset& characterOffset)
 {
     // make sure we move off of a paragraph start
     CharacterOffset previous = previousCharacterOffset(characterOffset);

     // We should skip the preceding BR node.
     if (characterOffsetNodeIsBR(previous) && !characterOffsetNodeIsBR(characterOffset))
         previous = previousCharacterOffset(previous);

     return startCharacterOffsetOfParagraph(previous);
 }

 CharacterOffset AXObjectCache::startCharacterOffsetOfSentence(const CharacterOffset& characterOffset)
 {
     return previousBoundary(characterOffset, startSentenceBoundary, NeedsContextAtParagraphStart::Yes);
 }

 CharacterOffset AXObjectCache::endCharacterOffsetOfSentence(const CharacterOffset& characterOffset)
 {
     return nextBoundary(characterOffset, endSentenceBoundary);
 }

 RefPtr<Range> AXObjectCache::sentenceForCharacterOffset(const CharacterOffset& characterOffset)
 {
     CharacterOffset start = startCharacterOffsetOfSentence(characterOffset);
     CharacterOffset end = endCharacterOffsetOfSentence(start);
     return rangeForUnorderedCharacterOffsets(start, end);
 }

 CharacterOffset AXObjectCache::nextSentenceEndCharacterOffset(const CharacterOffset& characterOffset)
 {
     // Make sure we move off of a sentence end.
     return endCharacterOffsetOfSentence(nextCharacterOffset(characterOffset));
 }

 CharacterOffset AXObjectCache::previousSentenceStartCharacterOffset(const CharacterOffset& characterOffset)
 {
     // Make sure we move off of a sentence start.
     CharacterOffset previous = previousCharacterOffset(characterOffset);

     // We should skip the preceding BR node.
     if (characterOffsetNodeIsBR(previous) && !characterOffsetNodeIsBR(characterOffset))
         previous = previousCharacterOffset(previous);

     return startCharacterOffsetOfSentence(previous);
 }

 LayoutRect AXObjectCache::localCaretRectForCharacterOffset(RenderObject*& renderer, const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull()) {
         renderer = nullptr;
         return IntRect();
     }

     Node* node = characterOffset.node;

     renderer = node->renderer();
     if (!renderer)
         return LayoutRect();

     InlineBox* inlineBox = nullptr;
     int caretOffset;
     // Use a collapsed range to get the position.
     RefPtr<Range> range = rangeForUnorderedCharacterOffsets(characterOffset, characterOffset);
     if (!range)
         return IntRect();

     Position startPosition = range->startPosition();
     startPosition.getInlineBoxAndOffset(DOWNSTREAM, inlineBox, caretOffset);

     if (inlineBox)
         renderer = &inlineBox->renderer();

     if (is<RenderLineBreak>(renderer) && downcast<RenderLineBreak>(renderer)->inlineBoxWrapper() != inlineBox)
         return IntRect();

     return renderer->localCaretRect(inlineBox, caretOffset);
 }

 IntRect AXObjectCache::absoluteCaretBoundsForCharacterOffset(const CharacterOffset& characterOffset)
 {
     RenderBlock* caretPainter = nullptr;

     // First compute a rect local to the renderer at the selection start.
     RenderObject* renderer = nullptr;
     LayoutRect localRect = localCaretRectForCharacterOffset(renderer, characterOffset);

     localRect = localCaretRectInRendererForRect(localRect, characterOffset.node, renderer, caretPainter);
     return absoluteBoundsForLocalCaretRect(caretPainter, localRect);
 }

 CharacterOffset AXObjectCache::characterOffsetForPoint(const IntPoint &point, AXCoreObject* obj)
 {
     if (!obj)
         return CharacterOffset();

     VisiblePosition vp = obj->visiblePositionForPoint(point);
     RefPtr<Range> range = makeRange(vp, vp);
     return startOrEndCharacterOffsetForRange(range, true);
 }

 CharacterOffset AXObjectCache::characterOffsetForPoint(const IntPoint &point)
 {
     RefPtr<Range> caretRange = m_document.caretRangeFromPoint(LayoutPoint(point));
     return startOrEndCharacterOffsetForRange(caretRange, true);
 }

 CharacterOffset AXObjectCache::characterOffsetForBounds(const IntRect& rect, bool first)
 {
     if (rect.isEmpty())
         return CharacterOffset();

     IntPoint corner = first ? rect.minXMinYCorner() : rect.maxXMaxYCorner();
     CharacterOffset characterOffset = characterOffsetForPoint(corner);

     if (rect.contains(absoluteCaretBoundsForCharacterOffset(characterOffset).center()))
         return characterOffset;

     // If the initial position is located outside the bounds adjust it incrementally as needed.
     CharacterOffset nextCharOffset = nextCharacterOffset(characterOffset, false);
     CharacterOffset previousCharOffset = previousCharacterOffset(characterOffset, false);
     while (!nextCharOffset.isNull() || !previousCharOffset.isNull()) {
         if (rect.contains(absoluteCaretBoundsForCharacterOffset(nextCharOffset).center()))
             return nextCharOffset;
         if (rect.contains(absoluteCaretBoundsForCharacterOffset(previousCharOffset).center()))
             return previousCharOffset;

         nextCharOffset = nextCharacterOffset(nextCharOffset, false);
         previousCharOffset = previousCharacterOffset(previousCharOffset, false);
     }

     return CharacterOffset();
 }

 // FIXME: Remove VisiblePosition code after implementing this using CharacterOffset.
 CharacterOffset AXObjectCache::endCharacterOffsetOfLine(const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     VisiblePosition vp = visiblePositionFromCharacterOffset(characterOffset);
     VisiblePosition endLine = endOfLine(vp);

     return characterOffsetFromVisiblePosition(endLine);
 }

 CharacterOffset AXObjectCache::startCharacterOffsetOfLine(const CharacterOffset& characterOffset)
 {
     if (characterOffset.isNull())
         return CharacterOffset();

     VisiblePosition vp = visiblePositionFromCharacterOffset(characterOffset);
     VisiblePosition startLine = startOfLine(vp);

     return characterOffsetFromVisiblePosition(startLine);
 }

 CharacterOffset AXObjectCache::characterOffsetForIndex(int index, const AXCoreObject* obj)
 {
     if (!obj)
         return CharacterOffset();

     VisiblePosition vp = obj->visiblePositionForIndex(index);
     CharacterOffset validate = characterOffsetFromVisiblePosition(vp);
     // In text control, VisiblePosition always gives the before position of a
     // BR node, while CharacterOffset will do the opposite.
     if (obj->isTextControl() && characterOffsetNodeIsBR(validate))
         validate.offset = 1;

     RefPtr<Range> range = obj->elementRange();
     CharacterOffset start = startOrEndCharacterOffsetForRange(range, true, true);
     CharacterOffset end = startOrEndCharacterOffsetForRange(range, false, true);
     CharacterOffset result = start;
     for (int i = 0; i < index; i++) {
         if (result.isEqual(validate)) {
             // Do not include the new line character, always move the offset to the start of next node.
             if ((validate.node->isTextNode() || characterOffsetNodeIsBR(validate))) {
                 CharacterOffset next = nextCharacterOffset(validate, false);
                 if (!next.isNull() && !next.offset && rootAXEditableElement(next.node) == rootAXEditableElement(validate.node))
                     result = next;
             }
             break;
         }

         result = nextCharacterOffset(result, false);
         if (result.isEqual(end))
             break;
     }
     return result;
 }

 int AXObjectCache::indexForCharacterOffset(const CharacterOffset& characterOffset, AccessibilityObject* obj)
 {
     // Create a collapsed range so that we can get the VisiblePosition from it.
     RefPtr<Range> range = rangeForUnorderedCharacterOffsets(characterOffset, characterOffset);
     if (!range)
         return 0;
     VisiblePosition vp = range->startPosition();
     return obj->indexForVisiblePosition(vp);
 }

 const Element* AXObjectCache::rootAXEditableElement(const Node* node)
 {
     const Element* result = node->rootEditableElement();
     const Element* element = is<Element>(*node) ? downcast<Element>(node) : node->parentElement();

     for (; element; element = element->parentElement()) {
         if (nodeIsTextControl(element))
             result = element;
     }

     return result;
 }

 static void conditionallyAddNodeToFilterList(Node* node, const Document& document, HashSet<Node*>& nodesToRemove)
 {
     if (node && (!node->isConnected() || &node->document() == &document))
         nodesToRemove.add(node);
 }

 template<typename T>
 static void filterVectorPairForRemoval(const Vector<std::pair<T, T>>& list, const Document& document, HashSet<Node*>& nodesToRemove)
 {
     for (auto& entry : list) {
         conditionallyAddNodeToFilterList(entry.first, document, nodesToRemove);
         conditionallyAddNodeToFilterList(entry.second, document, nodesToRemove);
     }
 }

 template<typename T, typename U>
 static void filterMapForRemoval(const HashMap<T, U>& list, const Document& document, HashSet<Node*>& nodesToRemove)
 {
     for (auto& entry : list)
         conditionallyAddNodeToFilterList(entry.key, document, nodesToRemove);
 }

 template<typename T>
 static void filterListForRemoval(const ListHashSet<T>& list, const Document& document, HashSet<Node*>& nodesToRemove)
 {
     for (auto* node : list)
         conditionallyAddNodeToFilterList(node, document, nodesToRemove);
 }

 void AXObjectCache::prepareForDocumentDestruction(const Document& document)
 {
     HashSet<Node*> nodesToRemove;
     filterListForRemoval(m_textMarkerNodes, document, nodesToRemove);
     filterListForRemoval(m_modalNodesSet, document, nodesToRemove);
     filterListForRemoval(m_deferredRecomputeIsIgnoredList, document, nodesToRemove);
     filterListForRemoval(m_deferredTextChangedList, document, nodesToRemove);
     filterListForRemoval(m_deferredSelectedChildredChangedList, document, nodesToRemove);
     filterListForRemoval(m_deferredChildrenChangedNodeList, document, nodesToRemove);
     filterMapForRemoval(m_deferredTextFormControlValue, document, nodesToRemove);
     filterMapForRemoval(m_deferredAttributeChange, document, nodesToRemove);
     filterVectorPairForRemoval(m_deferredFocusedNodeChange, document, nodesToRemove);

     for (auto* node : nodesToRemove)
         remove(*node);
 }

 bool AXObjectCache::nodeIsTextControl(const Node* node)
 {
     if (!node)
         return false;

     const AccessibilityObject* axObject = getOrCreate(const_cast<Node*>(node));
     return axObject && axObject->isTextControl();
 }

 void AXObjectCache::performCacheUpdateTimerFired()
 {
     // If there's a pending layout, let the layout trigger the AX update.
     if (!document().view() || document().view()->needsLayout())
         return;

     performDeferredCacheUpdate();
 }

 void AXObjectCache::performDeferredCacheUpdate()
 {
     if (m_performingDeferredCacheUpdate)
         return;

     SetForScope<bool> performingDeferredCacheUpdate(m_performingDeferredCacheUpdate, true);

     for (auto* nodeChild : m_deferredChildrenChangedNodeList) {
         handleMenuOpened(nodeChild);
         handleLiveRegionCreated(nodeChild);
     }
     m_deferredChildrenChangedNodeList.clear();

     for (auto& child : m_deferredChildrenChangedList)
         child->childrenChanged();
     m_deferredChildrenChangedList.clear();

     for (auto* node : m_deferredTextChangedList)
         textChanged(node);
     m_deferredTextChangedList.clear();

     for (auto* element : m_deferredRecomputeIsIgnoredList) {
         if (auto* renderer = element->renderer())
             recomputeIsIgnored(renderer);
     }
     m_deferredRecomputeIsIgnoredList.clear();

     for (auto* selectElement : m_deferredSelectedChildredChangedList)
         selectedChildrenChanged(selectElement);
     m_deferredSelectedChildredChangedList.clear();

     for (auto& deferredFormControlContext : m_deferredTextFormControlValue) {
         auto& textFormControlElement = downcast<HTMLTextFormControlElement>(*deferredFormControlContext.key);
         postTextReplacementNotificationForTextControl(textFormControlElement, deferredFormControlContext.value, textFormControlElement.innerTextValue());
     }
     m_deferredTextFormControlValue.clear();

     for (auto& deferredAttributeChangeContext : m_deferredAttributeChange)
         handleAttributeChange(deferredAttributeChangeContext.value, deferredAttributeChangeContext.key);
     m_deferredAttributeChange.clear();

     for (auto& deferredFocusedChangeContext : m_deferredFocusedNodeChange)
         handleFocusedUIElementChanged(deferredFocusedChangeContext.first, deferredFocusedChangeContext.second);
     m_deferredFocusedNodeChange.clear();

     platformPerformDeferredCacheUpdate();
 }

 #if ENABLE(ACCESSIBILITY_ISOLATED_TREE)
 Ref<AXIsolatedTree> AXObjectCache::generateIsolatedTree(PageIdentifier pageID, Document& document)
 {
     RELEASE_ASSERT(isMainThread());

     RefPtr<AXIsolatedTree> tree(AXIsolatedTree::createTreeForPageID(pageID));

     // Set the root and focused objects in the isolated tree. For that, we need
     // the root and the focused object in the AXObject tree.
     auto* axObjectCache = document.axObjectCache();
     if (!axObjectCache)
         return makeRef(*tree);
     tree->setAXObjectCache(axObjectCache);

     auto* axRoot = axObjectCache->getOrCreate(document.view());
     if (axRoot)
         tree->generateSubtree(*axRoot, InvalidAXID, true);

     auto* axFocus = axObjectCache->focusedObject(document);
     if (axFocus)
         tree->setFocusedNode(axFocus->objectID());

     return makeRef(*tree);
 }

 void AXObjectCache::updateIsolatedTree(AXCoreObject& object, AXNotification notification)
 {
     if (!m_pageID)
         return;

     auto tree = AXIsolatedTree::treeForPageID(*m_pageID);
     if (!tree)
         return;

     switch (notification) {
     case AXCheckedStateChanged:
     case AXSelectedTextChanged:
     case AXValueChanged: {
         if (object.objectID() != InvalidAXID)
             tree->updateNode(object);
         break;
     }
     default:
         break;
     }
 }

 // FIXME: should be added to WTF::Vector.
 template<typename T, typename F>
 static bool appendIfNotContainsMatching(Vector<T>& vector, const T& value, F matches)
 {
     if (vector.findMatching(matches) != notFound)
         return false;
     vector.append(value);
     return true;
 }

 void AXObjectCache::updateIsolatedTree(const Vector<std::pair<RefPtr<AXCoreObject>, AXNotification>>& notifications)
 {
     if (!m_pageID)
         return;

     auto tree = AXIsolatedTree::treeForPageID(*m_pageID);
     if (!tree)
         return;

     // Filter out multiple notifications for the same object. This avoids
     // updating the isolated tree multiple times unnecessarily.
     Vector<std::pair<RefPtr<AXCoreObject>, AXNotification>> filteredNotifications;
     for (const auto& notification : notifications) {
         if (!notification.first || notification.first->objectID() == InvalidAXID)
             continue;

         switch (notification.second) {
         case AXCheckedStateChanged:
         case AXSelectedTextChanged:
         case AXValueChanged: {
             bool needsUpdate = appendIfNotContainsMatching(filteredNotifications, notification, [&notification] (const std::pair<RefPtr<AXCoreObject>, AXNotification>& note) {
                 return note.second == notification.second && note.first.get() == notification.first.get();
             });

             if (needsUpdate)
                 tree->updateNode(*notification.first);
             break;
         }
         case AXChildrenChanged: {
             bool needsUpdate = appendIfNotContainsMatching(filteredNotifications, notification, [&notification] (const std::pair<RefPtr<AXCoreObject>, AXNotification>& note) {
                 return note.second == notification.second && note.first.get() == notification.first.get();
             });

             if (needsUpdate)
                 tree->updateChildren(*notification.first);
             break;
         }
         default:
             break;
         }
     }
 }
 #endif

 void AXObjectCache::deferRecomputeIsIgnoredIfNeeded(Element* element)
 {
     if (!nodeAndRendererAreValid(element))
         return;

     if (rendererNeedsDeferredUpdate(*element->renderer())) {
         m_deferredRecomputeIsIgnoredList.add(element);
         return;
     }
     recomputeIsIgnored(element->renderer());
 }

 void AXObjectCache::deferRecomputeIsIgnored(Element* element)
 {
     if (!nodeAndRendererAreValid(element))
         return;

     m_deferredRecomputeIsIgnoredList.add(element);
 }

 void AXObjectCache::deferTextChangedIfNeeded(Node* node)
 {
     if (!nodeAndRendererAreValid(node))
         return;

     if (rendererNeedsDeferredUpdate(*node->renderer())) {
         m_deferredTextChangedList.add(node);
         return;
     }
     textChanged(node);
 }

 void AXObjectCache::deferSelectedChildrenChangedIfNeeded(Element& selectElement)
 {
     if (!nodeAndRendererAreValid(&selectElement))
         return;

     if (rendererNeedsDeferredUpdate(*selectElement.renderer())) {
         m_deferredSelectedChildredChangedList.add(&selectElement);
         return;
     }
     selectedChildrenChanged(&selectElement);
 }

 void AXObjectCache::deferTextReplacementNotificationForTextControl(HTMLTextFormControlElement& formControlElement, const String& previousValue)
 {
     auto* renderer = formControlElement.renderer();
     if (!renderer)
         return;
     m_deferredTextFormControlValue.add(&formControlElement, previousValue);
 }

 bool isNodeAriaVisible(Node* node)
 {
     if (!node)
         return false;

     // ARIA Node visibility is controlled by aria-hidden
     //  1) if aria-hidden=true, the whole subtree is hidden
     //  2) if aria-hidden=false, and the object is rendered, there's no effect
     //  3) if aria-hidden=false, and the object is NOT rendered, then it must have
     //     aria-hidden=false on each parent until it gets to a rendered object
     //  3b) a text node inherits a parents aria-hidden value
     bool requiresAriaHiddenFalse = !node->renderer();
     bool ariaHiddenFalsePresent = false;
     for (Node* testNode = node; testNode; testNode = testNode->parentNode()) {
         if (is<Element>(*testNode)) {
             const AtomString& ariaHiddenValue = downcast<Element>(*testNode).attributeWithoutSynchronization(aria_hiddenAttr);
             if (equalLettersIgnoringASCIICase(ariaHiddenValue, "true"))
                 return false;

             bool ariaHiddenFalse = equalLettersIgnoringASCIICase(ariaHiddenValue, "false");
             if (!testNode->renderer() && !ariaHiddenFalse)
                 return false;
             if (!ariaHiddenFalsePresent && ariaHiddenFalse)
                 ariaHiddenFalsePresent = true;
             // We should break early when it gets to a rendered object.
             if (testNode->renderer())
                 break;
         }
     }

     return !requiresAriaHiddenFalse || ariaHiddenFalsePresent;
 }

 AXCoreObject* AXObjectCache::rootWebArea()
 {
     AXCoreObject* rootObject = this->rootObject();
     if (!rootObject || !rootObject->isScrollView())
         return nullptr;
     return rootObject->webAreaObject();
 }

 AXAttributeCacheEnabler::AXAttributeCacheEnabler(AXObjectCache* cache)
     : m_cache(cache)
 {
     if (m_cache)
         m_cache->startCachingComputedObjectAttributesUntilTreeMutates();
 }

 AXAttributeCacheEnabler::~AXAttributeCacheEnabler()
 {
     if (m_cache)
         m_cache->stopCachingComputedObjectAttributes();
 }

 #if !PLATFORM(COCOA)
 AXTextChange AXObjectCache::textChangeForEditType(AXTextEditType type)
 {
     switch (type) {
     case AXTextEditTypeCut:
     case AXTextEditTypeDelete:
         return AXTextDeleted;
     case AXTextEditTypeInsert:
     case AXTextEditTypeDictation:
     case AXTextEditTypeTyping:
     case AXTextEditTypePaste:
         return AXTextInserted;
     case AXTextEditTypeAttributesChange:
         return AXTextAttributesChanged;
     case AXTextEditTypeUnknown:
         break;
     }
     ASSERT_NOT_REACHED();
     return AXTextInserted;
 }
 #endif

 } // namespace WebCore

 #endif // ENABLE(ACCESSIBILITY)