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

/*
 * Copyright (C) 2014, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "modules/accessibility/AXObjectCacheImpl.h"

#include "base/memory/scoped_refptr.h"
#include "core/dom/AccessibleNode.h"
#include "core/dom/Document.h"
#include "core/editing/EditingUtilities.h"
#include "core/frame/LocalFrame.h"
#include "core/frame/LocalFrameView.h"
#include "core/frame/Settings.h"
#include "core/frame/WebLocalFrameImpl.h"
#include "core/html/HTMLAreaElement.h"
#include "core/html/HTMLCanvasElement.h"
#include "core/html/HTMLFrameOwnerElement.h"
#include "core/html/HTMLImageElement.h"
#include "core/html/forms/HTMLInputElement.h"
#include "core/html/forms/HTMLLabelElement.h"
#include "core/html/forms/HTMLOptionElement.h"
#include "core/html/forms/HTMLSelectElement.h"
#include "core/html_names.h"
#include "core/input_type_names.h"
#include "core/layout/LayoutListBox.h"
#include "core/layout/LayoutMenuList.h"
#include "core/layout/LayoutProgress.h"
#include "core/layout/LayoutSlider.h"
#include "core/layout/LayoutTable.h"
#include "core/layout/LayoutTableCell.h"
#include "core/layout/LayoutTableRow.h"
#include "core/layout/LayoutView.h"
#include "core/layout/api/LineLayoutAPIShim.h"
#include "core/layout/line/AbstractInlineTextBox.h"
#include "core/page/ChromeClient.h"
#include "core/page/FocusController.h"
#include "core/page/Page.h"
#include "modules/accessibility/AXARIAGrid.h"
#include "modules/accessibility/AXARIAGridCell.h"
#include "modules/accessibility/AXARIAGridRow.h"
#include "modules/accessibility/AXImageMapLink.h"
#include "modules/accessibility/AXInlineTextBox.h"
#include "modules/accessibility/AXLayoutObject.h"
#include "modules/accessibility/AXList.h"
#include "modules/accessibility/AXListBox.h"
#include "modules/accessibility/AXListBoxOption.h"
#include "modules/accessibility/AXMediaControls.h"
#include "modules/accessibility/AXMenuList.h"
#include "modules/accessibility/AXMenuListOption.h"
#include "modules/accessibility/AXMenuListPopup.h"
#include "modules/accessibility/AXProgressIndicator.h"
#include "modules/accessibility/AXRadioInput.h"
#include "modules/accessibility/AXRelationCache.h"
#include "modules/accessibility/AXSVGRoot.h"
#include "modules/accessibility/AXSlider.h"
#include "modules/accessibility/AXSpinButton.h"
#include "modules/accessibility/AXTable.h"
#include "modules/accessibility/AXTableCell.h"
#include "modules/accessibility/AXTableColumn.h"
#include "modules/accessibility/AXTableHeaderContainer.h"
#include "modules/accessibility/AXTableRow.h"
#include "modules/accessibility/AXVirtualObject.h"
#include "modules/permissions/PermissionUtils.h"
#include "public/platform/TaskType.h"
#include "public/platform/modules/permissions/permission.mojom-blink.h"
#include "public/platform/modules/permissions/permission_status.mojom-blink.h"
#include "public/web/WebFrameClient.h"

namespace blink {

using namespace HTMLNames;

// static
AXObjectCache* AXObjectCacheImpl::Create(Document& document) {
  return new AXObjectCacheImpl(document);
}

AXObjectCacheImpl::AXObjectCacheImpl(Document& document)
    : AXObjectCacheBase(document),
      document_(document),
      modification_count_(0),
      relation_cache_(new AXRelationCache(this)),
      notification_post_timer_(document.GetTaskRunner(TaskType::kUnspecedTimer),
                               this,
                               &AXObjectCacheImpl::NotificationPostTimerFired),
      accessibility_event_permission_(mojom::PermissionStatus::ASK),
      permission_observer_binding_(this) {
  if (document_->LoadEventFinished())
    AddPermissionStatusListener();
}

AXObjectCacheImpl::~AXObjectCacheImpl() {
#if DCHECK_IS_ON()
  DCHECK(has_been_disposed_);
#endif
}

void AXObjectCacheImpl::Dispose() {
  notification_post_timer_.Stop();

  for (auto& entry : objects_) {
    AXObject* obj = entry.value;
    obj->Detach();
    RemoveAXID(obj);
  }

#if DCHECK_IS_ON()
  has_been_disposed_ = true;
#endif
}

AXObject* AXObjectCacheImpl::Root() {
  return GetOrCreate(document_);
}

AXObject* AXObjectCacheImpl::FocusedImageMapUIElement(
    HTMLAreaElement* area_element) {
  // Find the corresponding accessibility object for the HTMLAreaElement. This
  // should be in the list of children for its corresponding image.
  if (!area_element)
    return nullptr;

  HTMLImageElement* image_element = area_element->ImageElement();
  if (!image_element)
    return nullptr;

  AXObject* ax_layout_image = GetOrCreate(image_element);
  if (!ax_layout_image)
    return nullptr;

  const AXObject::AXObjectVector& image_children = ax_layout_image->Children();
  unsigned count = image_children.size();
  for (unsigned k = 0; k < count; ++k) {
    AXObject* child = image_children[k];
    if (!child->IsImageMapLink())
      continue;

    if (ToAXImageMapLink(child)->AreaElement() == area_element)
      return child;
  }

  return nullptr;
}

AXObject* AXObjectCacheImpl::FocusedObject() {
  if (!AccessibilityEnabled())
    return nullptr;

  Node* focused_node = document_->FocusedElement();
  if (!focused_node)
    focused_node = document_;

  // If it's an image map, get the focused link within the image map.
  if (auto* area = ToHTMLAreaElementOrNull(focused_node))
    return FocusedImageMapUIElement(area);

  // See if there's a page popup, for example a calendar picker.
  Element* adjusted_focused_element = document_->AdjustedFocusedElement();
  if (auto* input = ToHTMLInputElementOrNull(adjusted_focused_element)) {
    if (AXObject* ax_popup = input->PopupRootAXObject()) {
      if (Element* focused_element_in_popup =
              ax_popup->GetDocument()->FocusedElement())
        focused_node = focused_element_in_popup;
    }
  }

  AXObject* obj = GetOrCreate(focused_node);
  if (!obj)
    return nullptr;

  // the HTML element, for example, is focusable but has an AX object that is
  // ignored
  if (obj->AccessibilityIsIgnored())
    obj = obj->ParentObjectUnignored();

  return obj;
}

AXObject* AXObjectCacheImpl::Get(LayoutObject* layout_object) {
  if (!layout_object)
    return nullptr;

  AXID ax_id = layout_object_mapping_.at(layout_object);
  DCHECK(!HashTraits<AXID>::IsDeletedValue(ax_id));
  if (!ax_id)
    return nullptr;

  return objects_.at(ax_id);
}

// Returns true if |node| is an <option> element and its parent <select>
// is a menu list (not a list box).
static bool IsMenuListOption(const Node* node) {
  if (!IsHTMLOptionElement(node))
    return false;
  const HTMLSelectElement* select =
      ToHTMLOptionElement(node)->OwnerSelectElement();
  if (!select)
    return false;
  const LayoutObject* layout_object = select->GetLayoutObject();
  return layout_object && layout_object->IsMenuList();
}

AXObject* AXObjectCacheImpl::Get(const Node* node) {
  if (!node)
    return nullptr;

  // Menu list option and HTML area elements are indexed by DOM node, never by
  // layout object.
  LayoutObject* layout_object = node->GetLayoutObject();
  if (IsMenuListOption(node) || IsHTMLAreaElement(node))
    layout_object = nullptr;

  AXID layout_id = layout_object ? layout_object_mapping_.at(layout_object) : 0;
  DCHECK(!HashTraits<AXID>::IsDeletedValue(layout_id));

  AXID node_id = node_object_mapping_.at(node);
  DCHECK(!HashTraits<AXID>::IsDeletedValue(node_id));

  if (layout_object && node_id && !layout_id) {
    // This can happen if an AXNodeObject is created for a node that's not
    // laid out, but later something changes and it gets a layoutObject (like if
    // it's reparented).
    Remove(node_id);
    return nullptr;
  }

  if (layout_id)
    return objects_.at(layout_id);

  if (!node_id)
    return nullptr;

  return objects_.at(node_id);
}

AXObject* AXObjectCacheImpl::Get(AbstractInlineTextBox* inline_text_box) {
  if (!inline_text_box)
    return nullptr;

  AXID ax_id = inline_text_box_object_mapping_.at(inline_text_box);
  DCHECK(!HashTraits<AXID>::IsDeletedValue(ax_id));
  if (!ax_id)
    return nullptr;

  return objects_.at(ax_id);
}

AXObject* AXObjectCacheImpl::Get(AccessibleNode* accessible_node) {
  if (!accessible_node)
    return nullptr;

  AXID ax_id = accessible_node_mapping_.at(accessible_node);
  DCHECK(!HashTraits<AXID>::IsDeletedValue(ax_id));
  if (!ax_id)
    return nullptr;

  return objects_.at(ax_id);
}

// FIXME: This probably belongs on Node.
// FIXME: This should take a const char*, but one caller passes g_null_atom.
static bool NodeHasRole(Node* node, const String& role) {
  if (!node || !node->IsElementNode())
    return false;

  return EqualIgnoringASCIICase(ToElement(node)->getAttribute(roleAttr), role);
}

static bool NodeHasGridRole(Node* node) {
  return NodeHasRole(node, "grid") || NodeHasRole(node, "treegrid");
}

AXObject* AXObjectCacheImpl::CreateFromRenderer(LayoutObject* layout_object) {
  // FIXME: How could layoutObject->node() ever not be an Element?
  Node* node = layout_object->GetNode();

  // 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 (NodeHasRole(node, "list") || NodeHasRole(node, "directory") ||
      (NodeHasRole(node, g_null_atom) &&
       (IsHTMLUListElement(node) || IsHTMLOListElement(node) ||
        IsHTMLDListElement(node))))
    return AXList::Create(layout_object, *this);

  // aria tables
  if (NodeHasGridRole(node))
    return AXARIAGrid::Create(layout_object, *this);
  if (NodeHasRole(node, "row"))
    return AXARIAGridRow::Create(layout_object, *this);
  if (NodeHasRole(node, "gridcell") || NodeHasRole(node, "columnheader") ||
      NodeHasRole(node, "rowheader"))
    return AXARIAGridCell::Create(layout_object, *this);

  // media controls
  if (node && node->IsMediaControlElement())
    return AccessibilityMediaControl::Create(layout_object, *this);

  if (IsHTMLOptionElement(node))
    return AXListBoxOption::Create(layout_object, *this);

  if (IsHTMLInputElement(node) &&
      ToHTMLInputElement(node)->type() == InputTypeNames::radio)
    return AXRadioInput::Create(layout_object, *this);

  if (layout_object->IsSVGRoot())
    return AXSVGRoot::Create(layout_object, *this);

  if (layout_object->IsBoxModelObject()) {
    LayoutBoxModelObject* css_box = ToLayoutBoxModelObject(layout_object);
    if (css_box->IsListBox())
      return AXListBox::Create(ToLayoutListBox(css_box), *this);
    if (css_box->IsMenuList())
      return AXMenuList::Create(ToLayoutMenuList(css_box), *this);

    // standard tables
    if (css_box->IsTable())
      return AXTable::Create(ToLayoutTable(css_box), *this);
    if (css_box->IsTableRow()) {
      // In an ARIA [tree]grid, use an ARIA row, otherwise a table row.
      LayoutTableRow* table_row = ToLayoutTableRow(css_box);
      LayoutTable* containing_table = table_row->Table();
      DCHECK(containing_table);
      if (NodeHasGridRole(containing_table->GetNode()))
        return AXARIAGridRow::Create(layout_object, *this);
      return AXTableRow::Create(ToLayoutTableRow(css_box), *this);
    }
    if (css_box->IsTableCell()) {
      // In an ARIA [tree]grid, use an ARIA gridcell, otherwise a table cell.
      LayoutTableCell* table_cell = ToLayoutTableCell(css_box);
      LayoutTable* containing_table = table_cell->Table();
      DCHECK(containing_table);
      if (NodeHasGridRole(containing_table->GetNode()))
        return AXARIAGridCell::Create(layout_object, *this);
      return AXTableCell::Create(ToLayoutTableCell(css_box), *this);
    }

    // progress bar
    if (css_box->IsProgress())
      return AXProgressIndicator::Create(ToLayoutProgress(css_box), *this);

    // input type=range
    if (css_box->IsSlider())
      return AXSlider::Create(ToLayoutSlider(css_box), *this);
  }

  return AXLayoutObject::Create(layout_object, *this);
}

AXObject* AXObjectCacheImpl::CreateFromNode(Node* node) {
  if (IsMenuListOption(node))
    return AXMenuListOption::Create(ToHTMLOptionElement(node), *this);

  if (auto* area = ToHTMLAreaElementOrNull(node))
    return AXImageMapLink::Create(area, *this);

  return AXNodeObject::Create(node, *this);
}

AXObject* AXObjectCacheImpl::CreateFromInlineTextBox(
    AbstractInlineTextBox* inline_text_box) {
  return AXInlineTextBox::Create(inline_text_box, *this);
}

AXObject* AXObjectCacheImpl::GetOrCreate(AccessibleNode* accessible_node) {
  if (AXObject* obj = Get(accessible_node))
    return obj;

  AXObject* new_obj = new AXVirtualObject(*this, accessible_node);
  const AXID ax_id = GetOrCreateAXID(new_obj);
  accessible_node_mapping_.Set(accessible_node, ax_id);

  new_obj->Init();
  return new_obj;
}

AXObject* AXObjectCacheImpl::GetOrCreate(Node* node) {
  if (!node)
    return nullptr;

  if (!node->IsElementNode() && !node->IsTextNode() && !node->IsDocumentNode())
    return nullptr;  // Only documents, elements and text nodes get a11y objects

  if (AXObject* obj = Get(node))
    return obj;

  // If the node has a layout object, prefer using that as the primary key for
  // the AXObject, with the exception of an HTMLAreaElement, which is
  // created based on its node.
  if (node->GetLayoutObject() && !IsHTMLAreaElement(node))
    return GetOrCreate(node->GetLayoutObject());

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

  if (IsHTMLHeadElement(node))
    return nullptr;

  AXObject* new_obj = CreateFromNode(node);

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

  const AXID ax_id = GetOrCreateAXID(new_obj);

  node_object_mapping_.Set(node, ax_id);
  new_obj->Init();
  new_obj->SetLastKnownIsIgnoredValue(new_obj->AccessibilityIsIgnored());

  relation_cache_->UpdateRelatedTree(node);

  return new_obj;
}

AXObject* AXObjectCacheImpl::GetOrCreate(LayoutObject* layout_object) {
  if (!layout_object)
    return nullptr;

  if (AXObject* obj = Get(layout_object))
    return obj;

  AXObject* new_obj = CreateFromRenderer(layout_object);

  // Will crash later if we have two objects for the same layoutObject.
  DCHECK(!Get(layout_object));

  const AXID axid = GetOrCreateAXID(new_obj);

  layout_object_mapping_.Set(layout_object, axid);
  new_obj->Init();
  new_obj->SetLastKnownIsIgnoredValue(new_obj->AccessibilityIsIgnored());

  return new_obj;
}

AXObject* AXObjectCacheImpl::GetOrCreate(
    AbstractInlineTextBox* inline_text_box) {
  if (!inline_text_box)
    return nullptr;

  if (AXObject* obj = Get(inline_text_box))
    return obj;

  AXObject* new_obj = CreateFromInlineTextBox(inline_text_box);

  // Will crash later if we have two objects for the same inlineTextBox.
  DCHECK(!Get(inline_text_box));

  const AXID axid = GetOrCreateAXID(new_obj);

  inline_text_box_object_mapping_.Set(inline_text_box, axid);
  new_obj->Init();
  new_obj->SetLastKnownIsIgnoredValue(new_obj->AccessibilityIsIgnored());

  return new_obj;
}

AXObject* AXObjectCacheImpl::GetOrCreate(AccessibilityRole role) {
  AXObject* obj = nullptr;

  // will be filled in...
  switch (role) {
    case kColumnRole:
      obj = AXTableColumn::Create(*this);
      break;
    case kTableHeaderContainerRole:
      obj = AXTableHeaderContainer::Create(*this);
      break;
    case kSliderThumbRole:
      obj = AXSliderThumb::Create(*this);
      break;
    case kMenuListPopupRole:
      obj = AXMenuListPopup::Create(*this);
      break;
    case kSpinButtonRole:
      obj = AXSpinButton::Create(*this);
      break;
    case kSpinButtonPartRole:
      obj = AXSpinButtonPart::Create(*this);
      break;
    default:
      obj = nullptr;
  }

  if (!obj)
    return nullptr;

  GetOrCreateAXID(obj);

  obj->Init();
  return obj;
}

void AXObjectCacheImpl::InvalidateTableSubtree(AXObject* subtree) {
  if (!subtree)
    return;

  LayoutObject* layout_object = subtree->GetLayoutObject();
  if (layout_object) {
    LayoutObject* layout_child = layout_object->SlowFirstChild();
    while (layout_child) {
      InvalidateTableSubtree(Get(layout_child));
      layout_child = layout_child->NextSibling();
    }
  }

  AXID ax_id = subtree->AXObjectID();
  Remove(ax_id);
}

void AXObjectCacheImpl::Remove(AXID ax_id) {
  if (!ax_id)
    return;

  // first fetch object to operate some cleanup functions on it
  AXObject* obj = objects_.at(ax_id);
  if (!obj)
    return;

  obj->Detach();
  RemoveAXID(obj);

  // finally remove the object
  if (!objects_.Take(ax_id))
    return;

  DCHECK_GE(objects_.size(), ids_in_use_.size());
}

void AXObjectCacheImpl::Remove(AccessibleNode* accessible_node) {
  if (!accessible_node)
    return;

  AXID ax_id = accessible_node_mapping_.at(accessible_node);
  Remove(ax_id);
  accessible_node_mapping_.erase(accessible_node);
}

void AXObjectCacheImpl::Remove(LayoutObject* layout_object) {
  if (!layout_object)
    return;

  AXID ax_id = layout_object_mapping_.at(layout_object);
  Remove(ax_id);
  layout_object_mapping_.erase(layout_object);
}

void AXObjectCacheImpl::Remove(Node* node) {
  if (!node)
    return;

  // This is all safe even if we didn't have a mapping.
  AXID ax_id = node_object_mapping_.at(node);
  Remove(ax_id);
  node_object_mapping_.erase(node);

  if (node->GetLayoutObject()) {
    Remove(node->GetLayoutObject());
    return;
  }
}

void AXObjectCacheImpl::Remove(AbstractInlineTextBox* inline_text_box) {
  if (!inline_text_box)
    return;

  AXID ax_id = inline_text_box_object_mapping_.at(inline_text_box);
  Remove(ax_id);
  inline_text_box_object_mapping_.erase(inline_text_box);
}

AXID AXObjectCacheImpl::GenerateAXID() const {
  static AXID last_used_id = 0;

  // Generate a new ID.
  AXID obj_id = last_used_id;
  do {
    ++obj_id;
  } while (!obj_id || HashTraits<AXID>::IsDeletedValue(obj_id) ||
           ids_in_use_.Contains(obj_id));

  last_used_id = obj_id;

  return obj_id;
}

AXID AXObjectCacheImpl::GetOrCreateAXID(AXObject* obj) {
  // check for already-assigned ID
  const AXID existing_axid = obj->AXObjectID();
  if (existing_axid) {
    DCHECK(ids_in_use_.Contains(existing_axid));
    return existing_axid;
  }

  const AXID new_axid = GenerateAXID();

  ids_in_use_.insert(new_axid);
  obj->SetAXObjectID(new_axid);
  objects_.Set(new_axid, obj);

  return new_axid;
}

void AXObjectCacheImpl::RemoveAXID(AXObject* object) {
  if (!object)
    return;

  AXID obj_id = object->AXObjectID();
  if (!obj_id)
    return;
  DCHECK(!HashTraits<AXID>::IsDeletedValue(obj_id));
  DCHECK(ids_in_use_.Contains(obj_id));
  object->SetAXObjectID(0);
  ids_in_use_.erase(obj_id);

  relation_cache_->RemoveAXID(obj_id);
}

AXObject* AXObjectCacheImpl::NearestExistingAncestor(Node* node) {
  // Find the nearest ancestor that already has an accessibility object, since
  // we might be in the middle of a layout.
  while (node) {
    if (AXObject* obj = Get(node))
      return obj;
    node = node->parentNode();
  }
  return nullptr;
}

void AXObjectCacheImpl::SelectionChanged(Node* node) {
  AXObject* nearestAncestor = NearestExistingAncestor(node);
  if (nearestAncestor)
    nearestAncestor->SelectionChanged();
}

void AXObjectCacheImpl::UpdateReverseRelations(
    const AXObject* relation_source,
    const Vector<String>& target_ids) {
  relation_cache_->UpdateReverseRelations(relation_source, target_ids);
}

void AXObjectCacheImpl::TextChanged(Node* node) {
  TextChanged(Get(node), node);
}

void AXObjectCacheImpl::TextChanged(LayoutObject* layout_object) {
  if (layout_object)
    TextChanged(Get(layout_object), layout_object->GetNode());
}

void AXObjectCacheImpl::TextChanged(AXObject* obj,
                                    Node* node_for_relation_update) {
  if (obj)
    obj->TextChanged();

  if (node_for_relation_update)
    relation_cache_->UpdateRelatedTree(node_for_relation_update);

  PostNotification(obj, AXObjectCacheImpl::kAXTextChanged);
}

void AXObjectCacheImpl::UpdateCacheAfterNodeIsAttached(Node* node) {
  // Calling get() will update the AX object if we had an AXNodeObject but now
  // we need an AXLayoutObject, because it was reparented to a location outside
  // of a canvas.
  Get(node);
  relation_cache_->UpdateRelatedTree(node);
}

void AXObjectCacheImpl::ChildrenChanged(Node* node) {
  ChildrenChanged(Get(node), node);
}

void AXObjectCacheImpl::ChildrenChanged(LayoutObject* layout_object) {
  if (layout_object) {
    AXObject* object = Get(layout_object);
    ChildrenChanged(object, layout_object->GetNode());
  }
}

void AXObjectCacheImpl::ChildrenChanged(AccessibleNode* accessible_node) {
  AXObject* object = Get(accessible_node);
  if (object)
    ChildrenChanged(object, object->GetNode());
}

void AXObjectCacheImpl::ChildrenChanged(AXObject* obj,
                                        Node* node_for_relation_update) {
  if (obj)
    obj->ChildrenChanged();

  if (node_for_relation_update)
    relation_cache_->UpdateRelatedTree(node_for_relation_update);
}

void AXObjectCacheImpl::NotificationPostTimerFired(TimerBase*) {
  notification_post_timer_.Stop();

  unsigned i = 0, count = notifications_to_post_.size();
  for (i = 0; i < count; ++i) {
    AXObject* obj = notifications_to_post_[i].first;

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

    if (obj->IsDetached())
      continue;

#if DCHECK_IS_ON()
    // Make sure none of the layout views are in the process of being layed out.
    // Notifications should only be sent after the layoutObject has finished
    if (obj->IsAXLayoutObject()) {
      AXLayoutObject* layout_obj = ToAXLayoutObject(obj);
      LayoutObject* layout_object = layout_obj->GetLayoutObject();
      if (layout_object && layout_object->View())
        DCHECK(!layout_object->View()->GetLayoutState());
    }
#endif

    AXNotification notification = notifications_to_post_[i].second;
    PostPlatformNotification(obj, notification);

    if (notification == kAXChildrenChanged && obj->ParentObjectIfExists() &&
        obj->LastKnownIsIgnoredValue() != obj->AccessibilityIsIgnored())
      ChildrenChanged(obj->ParentObject());
  }

  notifications_to_post_.clear();
}

void AXObjectCacheImpl::PostNotification(LayoutObject* layout_object,
                                         AXNotification notification) {
  if (!layout_object)
    return;
  PostNotification(Get(layout_object), notification);
}

void AXObjectCacheImpl::PostNotification(Node* node,
                                         AXNotification notification) {
  if (!node)
    return;
  PostNotification(Get(node), notification);
}

void AXObjectCacheImpl::PostNotification(AXObject* object,
                                         AXNotification notification) {
  if (!object)
    return;

  modification_count_++;
  notifications_to_post_.push_back(std::make_pair(object, notification));
  if (!notification_post_timer_.IsActive())
    notification_post_timer_.StartOneShot(TimeDelta(), FROM_HERE);
}

bool AXObjectCacheImpl::IsAriaOwned(const AXObject* object) const {
  return relation_cache_->IsAriaOwned(object);
}

AXObject* AXObjectCacheImpl::GetAriaOwnedParent(const AXObject* object) const {
  return relation_cache_->GetAriaOwnedParent(object);
}

void AXObjectCacheImpl::UpdateAriaOwns(
    const AXObject* owner,
    const Vector<String>& id_vector,
    HeapVector<Member<AXObject>>& owned_children) {
  relation_cache_->UpdateAriaOwns(owner, id_vector, owned_children);
}

void AXObjectCacheImpl::CheckedStateChanged(Node* node) {
  PostNotification(node, AXObjectCacheImpl::kAXCheckedStateChanged);
}

void AXObjectCacheImpl::ListboxOptionStateChanged(HTMLOptionElement* option) {
  PostNotification(option, kAXCheckedStateChanged);
}

void AXObjectCacheImpl::ListboxSelectedChildrenChanged(
    HTMLSelectElement* select) {
  PostNotification(select, kAXSelectedChildrenChanged);
}

void AXObjectCacheImpl::ListboxActiveIndexChanged(HTMLSelectElement* select) {
  AXObject* obj = Get(select);
  if (!obj || !obj->IsAXListBox())
    return;

  ToAXListBox(obj)->ActiveIndexChanged();
}

void AXObjectCacheImpl::RadiobuttonRemovedFromGroup(
    HTMLInputElement* group_member) {
  AXObject* obj = Get(group_member);
  if (!obj || !obj->IsAXRadioInput())
    return;

  // The 'posInSet' and 'setSize' attributes should be updated from the first
  // node, as the removed node is already detached from tree.
  HTMLInputElement* first_radio =
      ToAXRadioInput(obj)->FindFirstRadioButtonInGroup(group_member);
  AXObject* first_obj = Get(first_radio);
  if (!first_obj || !first_obj->IsAXRadioInput())
    return;

  ToAXRadioInput(first_obj)->UpdatePosAndSetSize(1);
  PostNotification(first_obj, kAXAriaAttributeChanged);
  ToAXRadioInput(first_obj)->RequestUpdateToNextNode(true);
}

void AXObjectCacheImpl::HandleLayoutComplete(LayoutObject* layout_object) {
  if (!layout_object)
    return;

  modification_count_++;

  // Create the AXObject if it didn't yet exist - that's always safe at the
  // end of a layout, and it allows an AX notification to be sent when a page
  // has its first layout, rather than when the document first loads.
  if (AXObject* obj = GetOrCreate(layout_object))
    PostNotification(obj, kAXLayoutComplete);
}

void AXObjectCacheImpl::HandleClicked(Node* node) {
  if (AXObject* obj = GetOrCreate(node))
    PostNotification(obj, kAXClicked);
}

void AXObjectCacheImpl::HandleAriaExpandedChange(Node* node) {
  if (AXObject* obj = GetOrCreate(node))
    obj->HandleAriaExpandedChanged();
}

void AXObjectCacheImpl::HandleAriaSelectedChanged(Node* node) {
  AXObject* obj = Get(node);
  if (!obj)
    return;

  PostNotification(obj, kAXCheckedStateChanged);

  AXObject* listbox = obj->ParentObjectUnignored();
  if (listbox && listbox->RoleValue() == kListBoxRole)
    PostNotification(listbox, kAXSelectedChildrenChanged);
}

void AXObjectCacheImpl::HandleActiveDescendantChanged(Node* node) {
  // Changing the active descendant should trigger recomputing all
  // cached values even if it doesn't result in a notification, because
  // it can affect what's focusable or not.
  modification_count_++;

  if (AXObject* obj = GetOrCreate(node))
    obj->HandleActiveDescendantChanged();
}

// Be as safe as possible about changes that could alter the accessibility role,
// as this may require a different subclass of AXObject.
// Role changes are disallowed by the spec but we must handle it gracefully, see
// https://www.w3.org/TR/wai-aria-1.1/#h-roles for more information.
void AXObjectCacheImpl::HandlePossibleRoleChange(Node* node) {
  if (!node)
    return;  // Virtual AOM node.

  // Invalidate the current object and make the parent reconsider its children.
  if (AXObject* obj = Get(node)) {
    // Save parent for later use.
    AXObject* parent = obj->ParentObject();

    // If role changes on a table, invalidate the entire table subtree as many
    // objects may suddenly need to change, because presentation is inherited
    // from the table to rows and cells.
    // TODO(aleventhal) A size change on a select means the children may need to
    // switch between AXMenuListOption and AXListBoxOption.
    // For some reason we don't get attribute changes for @size, though.
    LayoutObject* layout_object = node->GetLayoutObject();
    if (layout_object && layout_object->IsTable())
      InvalidateTableSubtree(obj);
    else
      Remove(node);

    // Parent object changed children, as the previous AXObject for this node
    // was destroyed and a different one was created in its place.
    if (parent)
      ChildrenChanged(parent, parent->GetNode());
    modification_count_++;
  }
}

void AXObjectCacheImpl::HandleAttributeChanged(const QualifiedName& attr_name,
                                               Element* element) {
  if (attr_name == roleAttr || attr_name == typeAttr || attr_name == sizeAttr)
    HandlePossibleRoleChange(element);
  else if (attr_name == altAttr || attr_name == titleAttr)
    TextChanged(element);
  else if (attr_name == forAttr && IsHTMLLabelElement(*element))
    LabelChanged(element);
  else if (attr_name == idAttr)
    relation_cache_->UpdateRelatedTree(element);

  if (!attr_name.LocalName().StartsWith("aria-"))
    return;

  // Perform updates specific to each attribute.
  if (attr_name == aria_activedescendantAttr)
    HandleActiveDescendantChanged(element);
  else if (attr_name == aria_valuenowAttr || attr_name == aria_valuetextAttr)
    PostNotification(element, AXObjectCacheImpl::kAXValueChanged);
  else if (attr_name == aria_labelAttr || attr_name == aria_labeledbyAttr ||
           attr_name == aria_labelledbyAttr)
    TextChanged(element);
  else if (attr_name == aria_describedbyAttr)
    TextChanged(element);  // TODO do we need a DescriptionChanged() ?
  else if (attr_name == aria_checkedAttr || attr_name == aria_pressedAttr)
    CheckedStateChanged(element);
  else if (attr_name == aria_selectedAttr)
    HandleAriaSelectedChanged(element);
  else if (attr_name == aria_expandedAttr)
    HandleAriaExpandedChange(element);
  else if (attr_name == aria_hiddenAttr)
    ChildrenChanged(element->parentNode());
  else if (attr_name == aria_invalidAttr)
    PostNotification(element, AXObjectCacheImpl::kAXInvalidStatusChanged);
  else if (attr_name == aria_ownsAttr)
    ChildrenChanged(element);
  else
    PostNotification(element, AXObjectCacheImpl::kAXAriaAttributeChanged);
}

void AXObjectCacheImpl::LabelChanged(Element* element) {
  TextChanged(ToHTMLLabelElement(element)->control());
}

void AXObjectCacheImpl::InlineTextBoxesUpdated(
    LineLayoutItem line_layout_item) {
  if (!InlineTextBoxAccessibilityEnabled())
    return;

  LayoutObject* layout_object =
      LineLayoutAPIShim::LayoutObjectFrom(line_layout_item);

  // Only update if the accessibility object already exists and it's
  // not already marked as dirty.
  if (AXObject* obj = Get(layout_object)) {
    if (!obj->NeedsToUpdateChildren()) {
      obj->SetNeedsToUpdateChildren();
      PostNotification(layout_object, kAXChildrenChanged);
    }
  }
}

Settings* AXObjectCacheImpl::GetSettings() {
  return document_->GetSettings();
}

bool AXObjectCacheImpl::AccessibilityEnabled() {
  Settings* settings = this->GetSettings();
  if (!settings)
    return false;
  return settings->GetAccessibilityEnabled();
}

bool AXObjectCacheImpl::InlineTextBoxAccessibilityEnabled() {
  Settings* settings = this->GetSettings();
  if (!settings)
    return false;
  return settings->GetInlineTextBoxAccessibilityEnabled();
}

const Element* AXObjectCacheImpl::RootAXEditableElement(const Node* node) {
  const Element* result = RootEditableElement(*node);
  const Element* element =
      node->IsElementNode() ? ToElement(node) : node->parentElement();

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

  return result;
}

AXObject* AXObjectCacheImpl::FirstAccessibleObjectFromNode(const Node* node) {
  if (!node)
    return nullptr;

  AXObject* accessible_object = GetOrCreate(node->GetLayoutObject());
  while (accessible_object && accessible_object->AccessibilityIsIgnored()) {
    node = NodeTraversal::Next(*node);

    while (node && !node->GetLayoutObject())
      node = NodeTraversal::NextSkippingChildren(*node);

    if (!node)
      return nullptr;

    accessible_object = GetOrCreate(node->GetLayoutObject());
  }

  return accessible_object;
}

bool AXObjectCacheImpl::NodeIsTextControl(const Node* node) {
  if (!node)
    return false;

  const AXObject* ax_object = GetOrCreate(const_cast<Node*>(node));
  return ax_object && ax_object->IsTextControl();
}

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

  if (!node->IsElementNode())
    return false;

  bool is_null = true;
  bool hidden = AccessibleNode::GetPropertyOrARIAAttribute(
      ToElement(node), AOMBooleanProperty::kHidden, is_null);
  return !is_null && !hidden;
}

void AXObjectCacheImpl::PostPlatformNotification(AXObject* obj,
                                                 AXNotification notification) {
  if (!obj || !obj->GetDocument() || !obj->DocumentFrameView() ||
      !obj->DocumentFrameView()->GetFrame().GetPage())
    return;
  // Send via WebFrameClient
  WebLocalFrameImpl* webframe = WebLocalFrameImpl::FromFrame(
      obj->GetDocument()->AXObjectCacheOwner().GetFrame());
  if (webframe && webframe->Client()) {
    webframe->Client()->PostAccessibilityEvent(
        WebAXObject(obj), static_cast<WebAXEvent>(notification));
  }
}

void AXObjectCacheImpl::HandleFocusedUIElementChanged(Node* old_focused_node,
                                                      Node* new_focused_node) {
  if (!new_focused_node)
    return;

  Page* page = new_focused_node->GetDocument().GetPage();
  if (!page)
    return;

  AXObject* focused_object = this->FocusedObject();
  if (!focused_object)
    return;

  AXObject* old_focused_object = Get(old_focused_node);

  PostPlatformNotification(old_focused_object, kAXBlur);
  PostPlatformNotification(focused_object, kAXFocusedUIElementChanged);
}

void AXObjectCacheImpl::HandleInitialFocus() {
  PostNotification(document_, kAXFocusedUIElementChanged);
}

void AXObjectCacheImpl::HandleEditableTextContentChanged(Node* node) {
  if (!node)
    return;

  AXObject* obj = nullptr;
  // We shouldn't create a new AX object here because we might be in the middle
  // of a layout.
  do {
    obj = Get(node);
  } while (!obj && (node = node->parentNode()));
  if (!obj)
    return;

  while (obj && !obj->IsNativeTextControl() && !obj->IsNonNativeTextControl())
    obj = obj->ParentObject();
  PostNotification(obj, kAXValueChanged);
}

void AXObjectCacheImpl::HandleTextFormControlChanged(Node* node) {
  HandleEditableTextContentChanged(node);
}

void AXObjectCacheImpl::HandleTextMarkerDataAdded(Node* start, Node* end) {
  if (!start || !end)
    return;

  // Notify the client of new text marker data.
  ChildrenChanged(start);
  if (start != end) {
    ChildrenChanged(end);
  }
}

void AXObjectCacheImpl::HandleValueChanged(Node* node) {
  PostNotification(node, kAXValueChanged);
}

void AXObjectCacheImpl::HandleUpdateActiveMenuOption(LayoutMenuList* menu_list,
                                                     int option_index) {
  AXObject* obj = GetOrCreate(menu_list);
  if (!obj || !obj->IsMenuList())
    return;

  ToAXMenuList(obj)->DidUpdateActiveOption(option_index);
}

void AXObjectCacheImpl::DidShowMenuListPopup(LayoutMenuList* menu_list) {
  AXObject* obj = Get(menu_list);
  if (!obj || !obj->IsMenuList())
    return;

  ToAXMenuList(obj)->DidShowPopup();
}

void AXObjectCacheImpl::DidHideMenuListPopup(LayoutMenuList* menu_list) {
  AXObject* obj = Get(menu_list);
  if (!obj || !obj->IsMenuList())
    return;

  ToAXMenuList(obj)->DidHidePopup();
}

void AXObjectCacheImpl::HandleLoadComplete(Document* document) {
  PostNotification(GetOrCreate(document), kAXLoadComplete);
  AddPermissionStatusListener();
}

void AXObjectCacheImpl::HandleLayoutComplete(Document* document) {
  PostNotification(GetOrCreate(document), kAXLayoutComplete);
}

void AXObjectCacheImpl::HandleScrolledToAnchor(const Node* anchor_node) {
  if (!anchor_node)
    return;
  AXObject* obj = GetOrCreate(anchor_node->GetLayoutObject());
  if (!obj)
    return;
  if (obj->AccessibilityIsIgnored())
    obj = obj->ParentObjectUnignored();
  PostPlatformNotification(obj, kAXScrolledToAnchor);
}

void AXObjectCacheImpl::HandleScrollPositionChanged(
    LocalFrameView* frame_view) {
  AXObject* target_ax_object =
      GetOrCreate(frame_view->GetFrame().GetDocument());
  PostPlatformNotification(target_ax_object, kAXScrollPositionChanged);
}

void AXObjectCacheImpl::HandleScrollPositionChanged(
    LayoutObject* layout_object) {
  PostPlatformNotification(GetOrCreate(layout_object),
                           kAXScrollPositionChanged);
}

const AtomicString& AXObjectCacheImpl::ComputedRoleForNode(Node* node) {
  AXObject* obj = GetOrCreate(node);
  if (!obj)
    return AXObject::RoleName(kUnknownRole);
  return AXObject::RoleName(obj->RoleValue());
}

String AXObjectCacheImpl::ComputedNameForNode(Node* node) {
  AXObject* obj = GetOrCreate(node);
  if (!obj)
    return "";

  return obj->ComputedName();
}

void AXObjectCacheImpl::OnTouchAccessibilityHover(const IntPoint& location) {
  AXObject* hit = Root()->AccessibilityHitTest(location);
  if (hit) {
    // Ignore events on a frame or plug-in, because the touch events
    // will be re-targeted there and we don't want to fire duplicate
    // accessibility events.
    if (hit->GetLayoutObject() &&
        hit->GetLayoutObject()->IsLayoutEmbeddedContent())
      return;

    PostPlatformNotification(hit, kAXHover);
  }
}

void AXObjectCacheImpl::SetCanvasObjectBounds(HTMLCanvasElement* canvas,
                                              Element* element,
                                              const LayoutRect& rect) {
  AXObject* obj = GetOrCreate(element);
  if (!obj)
    return;

  AXObject* ax_canvas = GetOrCreate(canvas);
  if (!ax_canvas)
    return;

  obj->SetElementRect(rect, ax_canvas);
}

void AXObjectCacheImpl::AddPermissionStatusListener() {
  if (!document_->GetExecutionContext())
    return;

  // Passing an Origin to Mojo crashes if the host is empty because
  // blink::SecurityOrigin sets unique to false, but url::Origin sets
  // unique to true. This only happens for some obscure corner cases
  // like on Android where the system registers unusual protocol handlers,
  // and we don't need any special permissions in those cases.
  //
  // http://crbug.com/759528 and http://crbug.com/762716
  if (document_->Url().Protocol() != "file" &&
      document_->Url().Host().IsEmpty()) {
    return;
  }

  ConnectToPermissionService(document_->GetExecutionContext(),
                             mojo::MakeRequest(&permission_service_));

  if (permission_observer_binding_.is_bound())
    permission_observer_binding_.Close();

  mojom::blink::PermissionObserverPtr observer;
  permission_observer_binding_.Bind(mojo::MakeRequest(&observer));
  permission_service_->AddPermissionObserver(
      CreatePermissionDescriptor(
          mojom::blink::PermissionName::ACCESSIBILITY_EVENTS),
      accessibility_event_permission_, std::move(observer));
}

void AXObjectCacheImpl::OnPermissionStatusChange(
    mojom::PermissionStatus status) {
  accessibility_event_permission_ = status;
}

bool AXObjectCacheImpl::CanCallAOMEventListeners() const {
  return accessibility_event_permission_ == mojom::PermissionStatus::GRANTED;
}

void AXObjectCacheImpl::RequestAOMEventListenerPermission() {
  if (accessibility_event_permission_ != mojom::PermissionStatus::ASK)
    return;

  if (!permission_service_)
    return;

  permission_service_->RequestPermission(
      CreatePermissionDescriptor(
          mojom::blink::PermissionName::ACCESSIBILITY_EVENTS),
      Frame::HasTransientUserActivation(document_->GetFrame()),
      WTF::Bind(&AXObjectCacheImpl::OnPermissionStatusChange,
                WrapPersistent(this)));
}

void AXObjectCacheImpl::ContextDestroyed(ExecutionContext*) {
  permission_service_.reset();
  permission_observer_binding_.Close();
}

void AXObjectCacheImpl::Trace(blink::Visitor* visitor) {
  visitor->Trace(document_);
  visitor->Trace(accessible_node_mapping_);
  visitor->Trace(node_object_mapping_);

  visitor->Trace(objects_);
  visitor->Trace(notifications_to_post_);

  AXObjectCache::Trace(visitor);
}

STATIC_ASSERT_ENUM(kWebAXEventActiveDescendantChanged,
                   AXObjectCacheImpl::kAXActiveDescendantChanged);
STATIC_ASSERT_ENUM(kWebAXEventAriaAttributeChanged,
                   AXObjectCacheImpl::kAXAriaAttributeChanged);
STATIC_ASSERT_ENUM(kWebAXEventAutocorrectionOccured,
                   AXObjectCacheImpl::kAXAutocorrectionOccured);
STATIC_ASSERT_ENUM(kWebAXEventBlur, AXObjectCacheImpl::kAXBlur);
STATIC_ASSERT_ENUM(kWebAXEventCheckedStateChanged,
                   AXObjectCacheImpl::kAXCheckedStateChanged);
STATIC_ASSERT_ENUM(kWebAXEventChildrenChanged,
                   AXObjectCacheImpl::kAXChildrenChanged);
STATIC_ASSERT_ENUM(kWebAXEventClicked, AXObjectCacheImpl::kAXClicked);
STATIC_ASSERT_ENUM(kWebAXEventDocumentSelectionChanged,
                   AXObjectCacheImpl::kAXDocumentSelectionChanged);
STATIC_ASSERT_ENUM(kWebAXEventExpandedChanged,
                   AXObjectCacheImpl::kAXExpandedChanged);
STATIC_ASSERT_ENUM(kWebAXEventFocus,
                   AXObjectCacheImpl::kAXFocusedUIElementChanged);
STATIC_ASSERT_ENUM(kWebAXEventHide, AXObjectCacheImpl::kAXHide);
STATIC_ASSERT_ENUM(kWebAXEventHover, AXObjectCacheImpl::kAXHover);
STATIC_ASSERT_ENUM(kWebAXEventInvalidStatusChanged,
                   AXObjectCacheImpl::kAXInvalidStatusChanged);
STATIC_ASSERT_ENUM(kWebAXEventLayoutComplete,
                   AXObjectCacheImpl::kAXLayoutComplete);
STATIC_ASSERT_ENUM(kWebAXEventLiveRegionChanged,
                   AXObjectCacheImpl::kAXLiveRegionChanged);
STATIC_ASSERT_ENUM(kWebAXEventLoadComplete, AXObjectCacheImpl::kAXLoadComplete);
STATIC_ASSERT_ENUM(kWebAXEventLocationChanged,
                   AXObjectCacheImpl::kAXLocationChanged);
STATIC_ASSERT_ENUM(kWebAXEventMenuListItemSelected,
                   AXObjectCacheImpl::kAXMenuListItemSelected);
STATIC_ASSERT_ENUM(kWebAXEventMenuListItemUnselected,
                   AXObjectCacheImpl::kAXMenuListItemUnselected);
STATIC_ASSERT_ENUM(kWebAXEventMenuListValueChanged,
                   AXObjectCacheImpl::kAXMenuListValueChanged);
STATIC_ASSERT_ENUM(kWebAXEventRowCollapsed, AXObjectCacheImpl::kAXRowCollapsed);
STATIC_ASSERT_ENUM(kWebAXEventRowCountChanged,
                   AXObjectCacheImpl::kAXRowCountChanged);
STATIC_ASSERT_ENUM(kWebAXEventRowExpanded, AXObjectCacheImpl::kAXRowExpanded);
STATIC_ASSERT_ENUM(kWebAXEventScrollPositionChanged,
                   AXObjectCacheImpl::kAXScrollPositionChanged);
STATIC_ASSERT_ENUM(kWebAXEventScrolledToAnchor,
                   AXObjectCacheImpl::kAXScrolledToAnchor);
STATIC_ASSERT_ENUM(kWebAXEventSelectedChildrenChanged,
                   AXObjectCacheImpl::kAXSelectedChildrenChanged);
STATIC_ASSERT_ENUM(kWebAXEventSelectedTextChanged,
                   AXObjectCacheImpl::kAXSelectedTextChanged);
STATIC_ASSERT_ENUM(kWebAXEventShow, AXObjectCacheImpl::kAXShow);
STATIC_ASSERT_ENUM(kWebAXEventTextChanged, AXObjectCacheImpl::kAXTextChanged);
STATIC_ASSERT_ENUM(kWebAXEventValueChanged, AXObjectCacheImpl::kAXValueChanged);

}  // namespace blink