accessible/generic/DocAccessible.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "Accessible-inl.h"
#include "AccIterator.h"
#include "DocAccessible-inl.h"
#include "DocAccessibleChild.h"
#include "HTMLImageMapAccessible.h"
#include "nsAccCache.h"
#include "nsAccessiblePivot.h"
#include "nsAccUtils.h"
#include "nsEventShell.h"
#include "nsTextEquivUtils.h"
#include "Role.h"
#include "RootAccessible.h"
#include "TreeWalker.h"
#include "xpcAccessibleDocument.h"

#include "nsIMutableArray.h"
#include "nsICommandManager.h"
#include "nsIDocShell.h"
#include "nsIDocument.h"
#include "nsIDOMCharacterData.h"
#include "nsIDOMDocument.h"
#include "nsPIDOMWindow.h"
#include "nsIEditingSession.h"
#include "nsIFrame.h"
#include "nsIInterfaceRequestorUtils.h"
#include "nsImageFrame.h"
#include "nsIPersistentProperties2.h"
#include "nsIPresShell.h"
#include "nsIServiceManager.h"
#include "nsViewManager.h"
#include "nsIScrollableFrame.h"
#include "nsUnicharUtils.h"
#include "nsIURI.h"
#include "nsIWebNavigation.h"
#include "nsFocusManager.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/Assertions.h"
#include "mozilla/EventStates.h"
#include "mozilla/HTMLEditor.h"
#include "mozilla/TextEditor.h"
#include "mozilla/dom/TabChild.h"
#include "mozilla/dom/DocumentType.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/MutationEventBinding.h"

using namespace mozilla;
using namespace mozilla::a11y;

////////////////////////////////////////////////////////////////////////////////
// Static member initialization

static nsStaticAtom** kRelationAttrs[] = {&nsGkAtoms::aria_labelledby,
                                          &nsGkAtoms::aria_describedby,
                                          &nsGkAtoms::aria_details,
                                          &nsGkAtoms::aria_owns,
                                          &nsGkAtoms::aria_controls,
                                          &nsGkAtoms::aria_flowto,
                                          &nsGkAtoms::aria_errormessage,
                                          &nsGkAtoms::_for,
                                          &nsGkAtoms::control};

static const uint32_t kRelationAttrsLen = ArrayLength(kRelationAttrs);

////////////////////////////////////////////////////////////////////////////////
// Constructor/desctructor

DocAccessible::DocAccessible(nsIDocument* aDocument, nsIPresShell* aPresShell)
    :  // XXX don't pass a document to the Accessible constructor so that we
       // don't set mDoc until our vtable is fully setup.  If we set mDoc before
       // setting up the vtable we will call Accessible::AddRef() but not the
       // overrides of it for subclasses.  It is important to call those
       // overrides to avoid confusing leak checking machinary.
      HyperTextAccessibleWrap(nullptr, nullptr),
      // XXX aaronl should we use an algorithm for the initial cache size?
      mAccessibleCache(kDefaultCacheLength),
      mNodeToAccessibleMap(kDefaultCacheLength),
      mDocumentNode(aDocument),
      mScrollPositionChangedTicks(0),
      mLoadState(eTreeConstructionPending),
      mDocFlags(0),
      mLoadEventType(0),
      mARIAAttrOldValue{nullptr},
      mVirtualCursor(nullptr),
      mPresShell(aPresShell),
      mIPCDoc(nullptr) {
  mGenericTypes |= eDocument;
  mStateFlags |= eNotNodeMapEntry;
  mDoc = this;

  MOZ_ASSERT(mPresShell, "should have been given a pres shell");
  mPresShell->SetDocAccessible(this);

  // If this is a XUL Document, it should not implement nsHyperText
  if (mDocumentNode && mDocumentNode->IsXULDocument())
    mGenericTypes &= ~eHyperText;
}

DocAccessible::~DocAccessible() {
  NS_ASSERTION(!mPresShell, "LastRelease was never called!?!");
}

////////////////////////////////////////////////////////////////////////////////
// nsISupports

NS_IMPL_CYCLE_COLLECTION_CLASS(DocAccessible)

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(DocAccessible, Accessible)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mNotificationController)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mVirtualCursor)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mChildDocuments)
  for (auto iter = tmp->mDependentIDsHash.Iter(); !iter.Done(); iter.Next()) {
    AttrRelProviderArray* providers = iter.UserData();

    for (int32_t jdx = providers->Length() - 1; jdx >= 0; jdx--) {
      NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(
          cb, "content of dependent ids hash entry of document accessible");

      AttrRelProvider* provider = (*providers)[jdx];
      cb.NoteXPCOMChild(provider->mContent);

      NS_ASSERTION(provider->mContent->IsInUncomposedDoc(),
                   "Referred content is not in document!");
    }
  }
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAccessibleCache)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAnchorJumpElm)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mInvalidationList)
  for (auto it = tmp->mARIAOwnsHash.ConstIter(); !it.Done(); it.Next()) {
    nsTArray<RefPtr<Accessible> >* ar = it.UserData();
    for (uint32_t i = 0; i < ar->Length(); i++) {
      NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mARIAOwnsHash entry item");
      cb.NoteXPCOMChild(ar->ElementAt(i));
    }
  }
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(DocAccessible, Accessible)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mNotificationController)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mVirtualCursor)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mChildDocuments)
  tmp->mDependentIDsHash.Clear();
  tmp->mNodeToAccessibleMap.Clear();
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mAccessibleCache)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mAnchorJumpElm)
  NS_IMPL_CYCLE_COLLECTION_UNLINK(mInvalidationList)
  tmp->mARIAOwnsHash.Clear();
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(DocAccessible)
  NS_INTERFACE_MAP_ENTRY(nsIDocumentObserver)
  NS_INTERFACE_MAP_ENTRY(nsIMutationObserver)
  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
  NS_INTERFACE_MAP_ENTRY(nsIObserver)
  NS_INTERFACE_MAP_ENTRY(nsIAccessiblePivotObserver)
NS_INTERFACE_MAP_END_INHERITING(HyperTextAccessible)

NS_IMPL_ADDREF_INHERITED(DocAccessible, HyperTextAccessible)
NS_IMPL_RELEASE_INHERITED(DocAccessible, HyperTextAccessible)

////////////////////////////////////////////////////////////////////////////////
// nsIAccessible

ENameValueFlag DocAccessible::Name(nsString& aName) {
  aName.Truncate();

  if (mParent) {
    mParent->Name(aName);  // Allow owning iframe to override the name
  }
  if (aName.IsEmpty()) {
    // Allow name via aria-labelledby or title attribute
    Accessible::Name(aName);
  }
  if (aName.IsEmpty()) {
    Title(aName);  // Try title element
  }
  if (aName.IsEmpty()) {  // Last resort: use URL
    URL(aName);
  }

  return eNameOK;
}

// Accessible public method
role DocAccessible::NativeRole() {
  nsCOMPtr<nsIDocShell> docShell = nsCoreUtils::GetDocShellFor(mDocumentNode);
  if (docShell) {
    nsCOMPtr<nsIDocShellTreeItem> sameTypeRoot;
    docShell->GetSameTypeRootTreeItem(getter_AddRefs(sameTypeRoot));
    int32_t itemType = docShell->ItemType();
    if (sameTypeRoot == docShell) {
      // Root of content or chrome tree
      if (itemType == nsIDocShellTreeItem::typeChrome)
        return roles::CHROME_WINDOW;

      if (itemType == nsIDocShellTreeItem::typeContent) {
#ifdef MOZ_XUL
        if (mDocumentNode && mDocumentNode->IsXULDocument())
          return roles::APPLICATION;
#endif
        return roles::DOCUMENT;
      }
    } else if (itemType == nsIDocShellTreeItem::typeContent) {
      return roles::DOCUMENT;
    }
  }

  return roles::PANE;  // Fall back;
}

void DocAccessible::Description(nsString& aDescription) {
  if (mParent) mParent->Description(aDescription);

  if (HasOwnContent() && aDescription.IsEmpty()) {
    nsTextEquivUtils::GetTextEquivFromIDRefs(this, nsGkAtoms::aria_describedby,
                                             aDescription);
  }
}

// Accessible public method
uint64_t DocAccessible::NativeState() {
  // Document is always focusable.
  uint64_t state =
      states::FOCUSABLE;  // keep in sync with NativeInteractiveState() impl
  if (FocusMgr()->IsFocused(this)) state |= states::FOCUSED;

  // Expose stale state until the document is ready (DOM is loaded and tree is
  // constructed).
  if (!HasLoadState(eReady)) state |= states::STALE;

  // Expose state busy until the document and all its subdocuments is completely
  // loaded.
  if (!HasLoadState(eCompletelyLoaded)) state |= states::BUSY;

  nsIFrame* frame = GetFrame();
  if (!frame || !frame->IsVisibleConsideringAncestors(
                    nsIFrame::VISIBILITY_CROSS_CHROME_CONTENT_BOUNDARY)) {
    state |= states::INVISIBLE | states::OFFSCREEN;
  }

  RefPtr<TextEditor> textEditor = GetEditor();
  state |= textEditor ? states::EDITABLE : states::READONLY;

  return state;
}

uint64_t DocAccessible::NativeInteractiveState() const {
  // Document is always focusable.
  return states::FOCUSABLE;
}

bool DocAccessible::NativelyUnavailable() const { return false; }

// Accessible public method
void DocAccessible::ApplyARIAState(uint64_t* aState) const {
  // Grab states from content element.
  if (mContent) Accessible::ApplyARIAState(aState);

  // Allow iframe/frame etc. to have final state override via ARIA.
  if (mParent) mParent->ApplyARIAState(aState);
}

already_AddRefed<nsIPersistentProperties> DocAccessible::Attributes() {
  nsCOMPtr<nsIPersistentProperties> attributes =
      HyperTextAccessibleWrap::Attributes();

  // No attributes if document is not attached to the tree or if it's a root
  // document.
  if (!mParent || IsRoot()) return attributes.forget();

  // Override ARIA object attributes from outerdoc.
  aria::AttrIterator attribIter(mParent->GetContent());
  nsAutoString name, value, unused;
  while (attribIter.Next(name, value))
    attributes->SetStringProperty(NS_ConvertUTF16toUTF8(name), value, unused);

  return attributes.forget();
}

Accessible* DocAccessible::FocusedChild() {
  // Return an accessible for the current global focus, which does not have to
  // be contained within the current document.
  return FocusMgr()->FocusedAccessible();
}

void DocAccessible::TakeFocus() {
  // Focus the document.
  nsFocusManager* fm = nsFocusManager::GetFocusManager();
  nsCOMPtr<nsIDOMElement> newFocus;
  fm->MoveFocus(mDocumentNode->GetWindow(), nullptr,
                nsFocusManager::MOVEFOCUS_ROOT, 0, getter_AddRefs(newFocus));
}

// HyperTextAccessible method
already_AddRefed<TextEditor> DocAccessible::GetEditor() const {
  // Check if document is editable (designMode="on" case). Otherwise check if
  // the html:body (for HTML document case) or document element is editable.
  if (!mDocumentNode->HasFlag(NODE_IS_EDITABLE) &&
      (!mContent || !mContent->HasFlag(NODE_IS_EDITABLE)))
    return nullptr;

  nsCOMPtr<nsIDocShell> docShell = mDocumentNode->GetDocShell();
  if (!docShell) {
    return nullptr;
  }

  nsCOMPtr<nsIEditingSession> editingSession;
  docShell->GetEditingSession(getter_AddRefs(editingSession));
  if (!editingSession) return nullptr;  // No editing session interface

  RefPtr<HTMLEditor> htmlEditor =
      editingSession->GetHTMLEditorForWindow(mDocumentNode->GetWindow());
  if (!htmlEditor) {
    return nullptr;
  }

  bool isEditable = false;
  htmlEditor->GetIsDocumentEditable(&isEditable);
  if (isEditable) {
    return htmlEditor.forget();
  }

  return nullptr;
}

// DocAccessible public method

void DocAccessible::URL(nsAString& aURL) const {
  nsCOMPtr<nsISupports> container = mDocumentNode->GetContainer();
  nsCOMPtr<nsIWebNavigation> webNav(do_GetInterface(container));
  nsAutoCString theURL;
  if (webNav) {
    nsCOMPtr<nsIURI> pURI;
    webNav->GetCurrentURI(getter_AddRefs(pURI));
    if (pURI) pURI->GetSpec(theURL);
  }
  CopyUTF8toUTF16(theURL, aURL);
}

void DocAccessible::DocType(nsAString& aType) const {
#ifdef MOZ_XUL
  if (mDocumentNode->IsXULDocument()) {
    aType.AssignLiteral("window");  // doctype not implemented for XUL at time
                                    // of writing - causes assertion
    return;
  }
#endif
  dom::DocumentType* docType = mDocumentNode->GetDoctype();
  if (docType) docType->GetPublicId(aType);
}

////////////////////////////////////////////////////////////////////////////////
// Accessible

void DocAccessible::Init() {
#ifdef A11Y_LOG
  if (logging::IsEnabled(logging::eDocCreate))
    logging::DocCreate("document initialize", mDocumentNode, this);
#endif

  // Initialize notification controller.
  mNotificationController = new NotificationController(this, mPresShell);

  // Mark the document accessible as loaded if its DOM document was loaded at
  // this point (this can happen because a11y is started late or DOM document
  // having no container was loaded.
  if (mDocumentNode->GetReadyStateEnum() == nsIDocument::READYSTATE_COMPLETE)
    mLoadState |= eDOMLoaded;

  AddEventListeners();
}

void DocAccessible::Shutdown() {
  if (!mPresShell)  // already shutdown
    return;

#ifdef A11Y_LOG
  if (logging::IsEnabled(logging::eDocDestroy))
    logging::DocDestroy("document shutdown", mDocumentNode, this);
#endif

  // Mark the document as shutdown before AT is notified about the document
  // removal from its container (valid for root documents on ATK and due to
  // some reason for MSAA, refer to bug 757392 for details).
  mStateFlags |= eIsDefunct;

  if (mNotificationController) {
    mNotificationController->Shutdown();
    mNotificationController = nullptr;
  }

  RemoveEventListeners();

  if (mParent) {
    DocAccessible* parentDocument = mParent->Document();
    if (parentDocument) parentDocument->RemoveChildDocument(this);

    mParent->RemoveChild(this);
  }

  // Walk the array backwards because child documents remove themselves from the
  // array as they are shutdown.
  int32_t childDocCount = mChildDocuments.Length();
  for (int32_t idx = childDocCount - 1; idx >= 0; idx--)
    mChildDocuments[idx]->Shutdown();

  mChildDocuments.Clear();

  // XXX thinking about ordering?
  if (mIPCDoc) {
    MOZ_ASSERT(IPCAccessibilityActive());
    mIPCDoc->Shutdown();
    MOZ_ASSERT(!mIPCDoc);
  }

  if (mVirtualCursor) {
    mVirtualCursor->RemoveObserver(this);
    mVirtualCursor = nullptr;
  }

  mPresShell->SetDocAccessible(nullptr);
  mPresShell = nullptr;  // Avoid reentrancy

  mDependentIDsHash.Clear();
  mNodeToAccessibleMap.Clear();

  for (auto iter = mAccessibleCache.Iter(); !iter.Done(); iter.Next()) {
    Accessible* accessible = iter.Data();
    MOZ_ASSERT(accessible);
    if (accessible && !accessible->IsDefunct()) {
      // Unlink parent to avoid its cleaning overhead in shutdown.
      accessible->mParent = nullptr;
      accessible->Shutdown();
    }
    iter.Remove();
  }

  HyperTextAccessibleWrap::Shutdown();

  GetAccService()->NotifyOfDocumentShutdown(this, mDocumentNode);
  mDocumentNode = nullptr;
}

nsIFrame* DocAccessible::GetFrame() const {
  nsIFrame* root = nullptr;
  if (mPresShell) root = mPresShell->GetRootFrame();

  return root;
}

// DocAccessible protected member
nsRect DocAccessible::RelativeBounds(nsIFrame** aRelativeFrame) const {
  *aRelativeFrame = GetFrame();

  nsIDocument* document = mDocumentNode;
  nsIDocument* parentDoc = nullptr;

  nsRect bounds;
  while (document) {
    nsIPresShell* presShell = document->GetShell();
    if (!presShell) return nsRect();

    nsRect scrollPort;
    nsIScrollableFrame* sf = presShell->GetRootScrollFrameAsScrollable();
    if (sf) {
      scrollPort = sf->GetScrollPortRect();
    } else {
      nsIFrame* rootFrame = presShell->GetRootFrame();
      if (!rootFrame) return nsRect();

      scrollPort = rootFrame->GetRect();
    }

    if (parentDoc) {  // After first time thru loop
      // XXXroc bogus code! scrollPort is relative to the viewport of
      // this document, but we're intersecting rectangles derived from
      // multiple documents and assuming they're all in the same coordinate
      // system. See bug 514117.
      bounds.IntersectRect(scrollPort, bounds);
    } else {  // First time through loop
      bounds = scrollPort;
    }

    document = parentDoc = document->GetParentDocument();
  }

  return bounds;
}

// DocAccessible protected member
nsresult DocAccessible::AddEventListeners() {
  nsCOMPtr<nsIDocShell> docShell(mDocumentNode->GetDocShell());

  // We want to add a command observer only if the document is content and has
  // an editor.
  if (docShell->ItemType() == nsIDocShellTreeItem::typeContent) {
    nsCOMPtr<nsICommandManager> commandManager = docShell->GetCommandManager();
    if (commandManager)
      commandManager->AddCommandObserver(this, "obs_documentCreated");
  }

  SelectionMgr()->AddDocSelectionListener(mPresShell);

  // Add document observer.
  mDocumentNode->AddObserver(this);
  return NS_OK;
}

// DocAccessible protected member
nsresult DocAccessible::RemoveEventListeners() {
  // Remove listeners associated with content documents
  // Remove scroll position listener
  RemoveScrollListener();

  NS_ASSERTION(mDocumentNode, "No document during removal of listeners.");

  if (mDocumentNode) {
    mDocumentNode->RemoveObserver(this);

    nsCOMPtr<nsIDocShell> docShell(mDocumentNode->GetDocShell());
    NS_ASSERTION(docShell, "doc should support nsIDocShellTreeItem.");

    if (docShell) {
      if (docShell->ItemType() == nsIDocShellTreeItem::typeContent) {
        nsCOMPtr<nsICommandManager> commandManager =
            docShell->GetCommandManager();
        if (commandManager) {
          commandManager->RemoveCommandObserver(this, "obs_documentCreated");
        }
      }
    }
  }

  if (mScrollWatchTimer) {
    mScrollWatchTimer->Cancel();
    mScrollWatchTimer = nullptr;
    NS_RELEASE_THIS();  // Kung fu death grip
  }

  SelectionMgr()->RemoveDocSelectionListener(mPresShell);
  return NS_OK;
}

void DocAccessible::ScrollTimerCallback(nsITimer* aTimer, void* aClosure) {
  DocAccessible* docAcc = reinterpret_cast<DocAccessible*>(aClosure);

  if (docAcc && docAcc->mScrollPositionChangedTicks &&
      ++docAcc->mScrollPositionChangedTicks > 2) {
    // Whenever scroll position changes, mScrollPositionChangeTicks gets reset
    // to 1 We only want to fire accessibilty scroll event when scrolling stops
    // or pauses Therefore, we wait for no scroll events to occur between 2
    // ticks of this timer That indicates a pause in scrolling, so we fire the
    // accessibilty scroll event
    nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_SCROLLING_END, docAcc);

    docAcc->mScrollPositionChangedTicks = 0;
    if (docAcc->mScrollWatchTimer) {
      docAcc->mScrollWatchTimer->Cancel();
      docAcc->mScrollWatchTimer = nullptr;
      NS_RELEASE(docAcc);  // Release kung fu death grip
    }
  }
}

////////////////////////////////////////////////////////////////////////////////
// nsIScrollPositionListener

void DocAccessible::ScrollPositionDidChange(nscoord aX, nscoord aY) {
  // Start new timer, if the timer cycles at least 1 full cycle without more
  // scroll position changes, then the ::Notify() method will fire the
  // accessibility event for scroll position changes
  const uint32_t kScrollPosCheckWait = 50;
  if (mScrollWatchTimer) {
    mScrollWatchTimer->SetDelay(
        kScrollPosCheckWait);  // Create new timer, to avoid leaks
  } else {
    NS_NewTimerWithFuncCallback(getter_AddRefs(mScrollWatchTimer),
                                ScrollTimerCallback, this, kScrollPosCheckWait,
                                nsITimer::TYPE_REPEATING_SLACK,
                                "a11y::DocAccessible::ScrollPositionDidChange");
    if (mScrollWatchTimer) {
      NS_ADDREF_THIS();  // Kung fu death grip
    }
  }
  mScrollPositionChangedTicks = 1;
}

////////////////////////////////////////////////////////////////////////////////
// nsIObserver

NS_IMETHODIMP
DocAccessible::Observe(nsISupports* aSubject, const char* aTopic,
                       const char16_t* aData) {
  if (!nsCRT::strcmp(aTopic, "obs_documentCreated")) {
    // State editable will now be set, readonly is now clear
    // Normally we only fire delayed events created from the node, not an
    // accessible object. See the AccStateChangeEvent constructor for details
    // about this exceptional case.
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(this, states::EDITABLE, true);
    FireDelayedEvent(event);
  }

  return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
// nsIAccessiblePivotObserver

NS_IMETHODIMP
DocAccessible::OnPivotChanged(nsIAccessiblePivot* aPivot,
                              nsIAccessible* aOldAccessible, int32_t aOldStart,
                              int32_t aOldEnd, PivotMoveReason aReason,
                              bool aIsFromUserInput) {
  RefPtr<AccEvent> event = new AccVCChangeEvent(
      this, (aOldAccessible ? aOldAccessible->ToInternalAccessible() : nullptr),
      aOldStart, aOldEnd, aReason,
      aIsFromUserInput ? eFromUserInput : eNoUserInput);
  nsEventShell::FireEvent(event);

  return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
// nsIDocumentObserver

NS_IMPL_NSIDOCUMENTOBSERVER_CORE_STUB(DocAccessible)
NS_IMPL_NSIDOCUMENTOBSERVER_LOAD_STUB(DocAccessible)
NS_IMPL_NSIDOCUMENTOBSERVER_STYLE_STUB(DocAccessible)

void DocAccessible::AttributeWillChange(dom::Element* aElement,
                                        int32_t aNameSpaceID,
                                        nsAtom* aAttribute, int32_t aModType,
                                        const nsAttrValue* aNewValue) {
  Accessible* accessible = GetAccessible(aElement);
  if (!accessible) {
    if (aElement != mContent) return;

    accessible = this;
  }

  // Update dependent IDs cache. Take care of elements that are accessible
  // because dependent IDs cache doesn't contain IDs from non accessible
  // elements.
  if (aModType != dom::MutationEventBinding::ADDITION)
    RemoveDependentIDsFor(accessible, aAttribute);

  if (aAttribute == nsGkAtoms::id) {
    RelocateARIAOwnedIfNeeded(aElement);
  }

  // Store the ARIA attribute old value so that it can be used after
  // attribute change. Note, we assume there's no nested ARIA attribute
  // changes. If this happens then we should end up with keeping a stack of
  // old values.

  // XXX TODO: bugs 472142, 472143.
  // Here we will want to cache whatever attribute values we are interested
  // in, such as the existence of aria-pressed for button (so we know if we
  // need to newly expose it as a toggle button) etc.
  if (aAttribute == nsGkAtoms::aria_checked ||
      aAttribute == nsGkAtoms::aria_pressed) {
    mARIAAttrOldValue = (aModType != dom::MutationEventBinding::ADDITION)
                            ? nsAccUtils::GetARIAToken(aElement, aAttribute)
                            : nullptr;
    return;
  }

  if (aAttribute == nsGkAtoms::aria_disabled ||
      aAttribute == nsGkAtoms::disabled)
    mStateBitWasOn = accessible->Unavailable();
}

void DocAccessible::NativeAnonymousChildListChange(nsIContent* aContent,
                                                   bool aIsRemove) {}

void DocAccessible::AttributeChanged(dom::Element* aElement,
                                     int32_t aNameSpaceID, nsAtom* aAttribute,
                                     int32_t aModType,
                                     const nsAttrValue* aOldValue) {
  NS_ASSERTION(!IsDefunct(),
               "Attribute changed called on defunct document accessible!");

  // Proceed even if the element is not accessible because element may become
  // accessible if it gets certain attribute.
  if (UpdateAccessibleOnAttrChange(aElement, aAttribute)) return;

  // Ignore attribute change if the element doesn't have an accessible (at all
  // or still) iff the element is not a root content of this document accessible
  // (which is treated as attribute change on this document accessible).
  // Note: we don't bail if all the content hasn't finished loading because
  // these attributes are changing for a loaded part of the content.
  Accessible* accessible = GetAccessible(aElement);
  if (!accessible) {
    if (mContent != aElement) return;

    accessible = this;
  }

  MOZ_ASSERT(accessible->IsBoundToParent() || accessible->IsDoc(),
             "DOM attribute change on an accessible detached from the tree");

  // Fire accessible events iff there's an accessible, otherwise we consider
  // the accessible state wasn't changed, i.e. its state is initial state.
  AttributeChangedImpl(accessible, aNameSpaceID, aAttribute);

  // Update dependent IDs cache. Take care of accessible elements because no
  // accessible element means either the element is not accessible at all or
  // its accessible will be created later. It doesn't make sense to keep
  // dependent IDs for non accessible elements. For the second case we'll update
  // dependent IDs cache when its accessible is created.
  if (aModType == dom::MutationEventBinding::MODIFICATION ||
      aModType == dom::MutationEventBinding::ADDITION) {
    AddDependentIDsFor(accessible, aAttribute);
  }
}

// DocAccessible protected member
void DocAccessible::AttributeChangedImpl(Accessible* aAccessible,
                                         int32_t aNameSpaceID,
                                         nsAtom* aAttribute) {
  // Fire accessible event after short timer, because we need to wait for
  // DOM attribute & resulting layout to actually change. Otherwise,
  // assistive technology will retrieve the wrong state/value/selection info.

  // XXX todo
  // We still need to handle special HTML cases here
  // For example, if an <img>'s usemap attribute is modified
  // Otherwise it may just be a state change, for example an object changing
  // its visibility
  //
  // XXX todo: report aria state changes for "undefined" literal value changes
  // filed as bug 472142
  //
  // XXX todo:  invalidate accessible when aria state changes affect exposed
  // role filed as bug 472143

  // Universal boolean properties that don't require a role. Fire the state
  // change when disabled or aria-disabled attribute is set.
  // Note. Checking the XUL or HTML namespace would not seem to gain us
  // anything, because disabled attribute really is going to mean the same
  // thing in any namespace.
  // Note. We use the attribute instead of the disabled state bit because
  // ARIA's aria-disabled does not affect the disabled state bit.
  if (aAttribute == nsGkAtoms::disabled ||
      aAttribute == nsGkAtoms::aria_disabled) {
    // Do nothing if state wasn't changed (like @aria-disabled was removed but
    // @disabled is still presented).
    if (aAccessible->Unavailable() == mStateBitWasOn) return;

    RefPtr<AccEvent> enabledChangeEvent =
        new AccStateChangeEvent(aAccessible, states::ENABLED, mStateBitWasOn);
    FireDelayedEvent(enabledChangeEvent);

    RefPtr<AccEvent> sensitiveChangeEvent =
        new AccStateChangeEvent(aAccessible, states::SENSITIVE, mStateBitWasOn);
    FireDelayedEvent(sensitiveChangeEvent);
    return;
  }

  // Check for namespaced ARIA attribute
  if (aNameSpaceID == kNameSpaceID_None) {
    // Check for hyphenated aria-foo property?
    if (StringBeginsWith(nsDependentAtomString(aAttribute),
                         NS_LITERAL_STRING("aria-"))) {
      ARIAAttributeChanged(aAccessible, aAttribute);
    }
  }

  // Fire name change and description change events. XXX: it's not complete and
  // dupes the code logic of accessible name and description calculation, we do
  // that for performance reasons.
  if (aAttribute == nsGkAtoms::aria_label) {
    FireDelayedEvent(nsIAccessibleEvent::EVENT_NAME_CHANGE, aAccessible);
    return;
  }

  if (aAttribute == nsGkAtoms::aria_describedby) {
    FireDelayedEvent(nsIAccessibleEvent::EVENT_DESCRIPTION_CHANGE, aAccessible);
    return;
  }

  dom::Element* elm = aAccessible->GetContent()->AsElement();
  if (aAttribute == nsGkAtoms::aria_labelledby &&
      !elm->HasAttr(kNameSpaceID_None, nsGkAtoms::aria_label)) {
    FireDelayedEvent(nsIAccessibleEvent::EVENT_NAME_CHANGE, aAccessible);
    return;
  }

  if (aAttribute == nsGkAtoms::alt &&
      !elm->HasAttr(kNameSpaceID_None, nsGkAtoms::aria_label) &&
      !elm->HasAttr(kNameSpaceID_None, nsGkAtoms::aria_labelledby)) {
    FireDelayedEvent(nsIAccessibleEvent::EVENT_NAME_CHANGE, aAccessible);
    return;
  }

  if (aAttribute == nsGkAtoms::title) {
    if (!elm->HasAttr(kNameSpaceID_None, nsGkAtoms::aria_label) &&
        !elm->HasAttr(kNameSpaceID_None, nsGkAtoms::aria_labelledby) &&
        !elm->HasAttr(kNameSpaceID_None, nsGkAtoms::alt)) {
      FireDelayedEvent(nsIAccessibleEvent::EVENT_NAME_CHANGE, aAccessible);
      return;
    }

    if (!elm->HasAttr(kNameSpaceID_None, nsGkAtoms::aria_describedby))
      FireDelayedEvent(nsIAccessibleEvent::EVENT_DESCRIPTION_CHANGE,
                       aAccessible);

    return;
  }

  if (aAttribute == nsGkAtoms::aria_busy) {
    bool isOn = elm->AttrValueIs(aNameSpaceID, aAttribute, nsGkAtoms::_true,
                                 eCaseMatters);
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(aAccessible, states::BUSY, isOn);
    FireDelayedEvent(event);
    return;
  }

  if (aAttribute == nsGkAtoms::id) {
    RelocateARIAOwnedIfNeeded(elm);
  }

  // ARIA or XUL selection
  if ((aAccessible->GetContent()->IsXULElement() &&
       aAttribute == nsGkAtoms::selected) ||
      aAttribute == nsGkAtoms::aria_selected) {
    Accessible* widget =
        nsAccUtils::GetSelectableContainer(aAccessible, aAccessible->State());
    if (widget) {
      AccSelChangeEvent::SelChangeType selChangeType =
          elm->AttrValueIs(aNameSpaceID, aAttribute, nsGkAtoms::_true,
                           eCaseMatters)
              ? AccSelChangeEvent::eSelectionAdd
              : AccSelChangeEvent::eSelectionRemove;

      RefPtr<AccEvent> event =
          new AccSelChangeEvent(widget, aAccessible, selChangeType);
      FireDelayedEvent(event);
    }

    return;
  }

  if (aAttribute == nsGkAtoms::contenteditable) {
    RefPtr<AccEvent> editableChangeEvent =
        new AccStateChangeEvent(aAccessible, states::EDITABLE);
    FireDelayedEvent(editableChangeEvent);
    return;
  }

  if (aAttribute == nsGkAtoms::value) {
    if (aAccessible->IsProgress())
      FireDelayedEvent(nsIAccessibleEvent::EVENT_VALUE_CHANGE, aAccessible);
  }
}

// DocAccessible protected member
void DocAccessible::ARIAAttributeChanged(Accessible* aAccessible,
                                         nsAtom* aAttribute) {
  // Note: For universal/global ARIA states and properties we don't care if
  // there is an ARIA role present or not.

  if (aAttribute == nsGkAtoms::aria_required) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(aAccessible, states::REQUIRED);
    FireDelayedEvent(event);
    return;
  }

  if (aAttribute == nsGkAtoms::aria_invalid) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(aAccessible, states::INVALID);
    FireDelayedEvent(event);
    return;
  }

  // The activedescendant universal property redirects accessible focus events
  // to the element with the id that activedescendant points to. Make sure
  // the tree up to date before processing.
  if (aAttribute == nsGkAtoms::aria_activedescendant) {
    mNotificationController->HandleNotification<DocAccessible, Accessible>(
        this, &DocAccessible::ARIAActiveDescendantChanged, aAccessible);

    return;
  }

  // We treat aria-expanded as a global ARIA state for historical reasons
  if (aAttribute == nsGkAtoms::aria_expanded) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(aAccessible, states::EXPANDED);
    FireDelayedEvent(event);
    return;
  }

  // For aria attributes like drag and drop changes we fire a generic attribute
  // change event; at least until native API comes up with a more meaningful
  // event.
  uint8_t attrFlags = aria::AttrCharacteristicsFor(aAttribute);
  if (!(attrFlags & ATTR_BYPASSOBJ)) {
    RefPtr<AccEvent> event =
        new AccObjectAttrChangedEvent(aAccessible, aAttribute);
    FireDelayedEvent(event);
  }

  dom::Element* elm = aAccessible->GetContent()->AsElement();

  // Update aria-hidden flag for the whole subtree iff aria-hidden is changed
  // on the root, i.e. ignore any affiliated aria-hidden changes in the subtree
  // of top aria-hidden.
  if (aAttribute == nsGkAtoms::aria_hidden) {
    bool isDefined = aria::HasDefinedARIAHidden(elm);
    if (isDefined != aAccessible->IsARIAHidden() &&
        (!aAccessible->Parent() || !aAccessible->Parent()->IsARIAHidden())) {
      aAccessible->SetARIAHidden(isDefined);

      RefPtr<AccEvent> event =
          new AccObjectAttrChangedEvent(aAccessible, aAttribute);
      FireDelayedEvent(event);
    }
    return;
  }

  if (aAttribute == nsGkAtoms::aria_checked ||
      (aAccessible->IsButton() && aAttribute == nsGkAtoms::aria_pressed)) {
    const uint64_t kState = (aAttribute == nsGkAtoms::aria_checked)
                                ? states::CHECKED
                                : states::PRESSED;
    RefPtr<AccEvent> event = new AccStateChangeEvent(aAccessible, kState);
    FireDelayedEvent(event);

    bool wasMixed = (mARIAAttrOldValue == nsGkAtoms::mixed);
    bool isMixed = elm->AttrValueIs(kNameSpaceID_None, aAttribute,
                                    nsGkAtoms::mixed, eCaseMatters);
    if (isMixed != wasMixed) {
      RefPtr<AccEvent> event =
          new AccStateChangeEvent(aAccessible, states::MIXED, isMixed);
      FireDelayedEvent(event);
    }
    return;
  }

  if (aAttribute == nsGkAtoms::aria_readonly) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(aAccessible, states::READONLY);
    FireDelayedEvent(event);
    return;
  }

  // Fire text value change event whenever aria-valuetext is changed.
  if (aAttribute == nsGkAtoms::aria_valuetext) {
    FireDelayedEvent(nsIAccessibleEvent::EVENT_TEXT_VALUE_CHANGE, aAccessible);
    return;
  }

  // Fire numeric value change event when aria-valuenow is changed and
  // aria-valuetext is empty
  if (aAttribute == nsGkAtoms::aria_valuenow &&
      (!elm->HasAttr(kNameSpaceID_None, nsGkAtoms::aria_valuetext) ||
       elm->AttrValueIs(kNameSpaceID_None, nsGkAtoms::aria_valuetext,
                        nsGkAtoms::_empty, eCaseMatters))) {
    FireDelayedEvent(nsIAccessibleEvent::EVENT_VALUE_CHANGE, aAccessible);
    return;
  }

  if (aAttribute == nsGkAtoms::aria_current) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(aAccessible, states::CURRENT);
    FireDelayedEvent(event);
    return;
  }

  if (aAttribute == nsGkAtoms::aria_owns) {
    mNotificationController->ScheduleRelocation(aAccessible);
  }
}

void DocAccessible::ARIAActiveDescendantChanged(Accessible* aAccessible) {
  nsIContent* elm = aAccessible->GetContent();
  if (elm && elm->IsElement() && aAccessible->IsActiveWidget()) {
    nsAutoString id;
    if (elm->AsElement()->GetAttr(kNameSpaceID_None,
                                  nsGkAtoms::aria_activedescendant, id)) {
      dom::Element* activeDescendantElm = elm->OwnerDoc()->GetElementById(id);
      if (activeDescendantElm) {
        Accessible* activeDescendant = GetAccessible(activeDescendantElm);
        if (activeDescendant) {
          FocusMgr()->ActiveItemChanged(activeDescendant, false);
#ifdef A11Y_LOG
          if (logging::IsEnabled(logging::eFocus))
            logging::ActiveItemChangeCausedBy("ARIA activedescedant changed",
                                              activeDescendant);
#endif
        }
      }
    }
  }
}

void DocAccessible::ContentAppended(nsIContent* aFirstNewContent) {}

void DocAccessible::ContentStateChanged(nsIDocument* aDocument,
                                        nsIContent* aContent,
                                        EventStates aStateMask) {
  Accessible* accessible = GetAccessible(aContent);
  if (!accessible) return;

  if (aStateMask.HasState(NS_EVENT_STATE_CHECKED)) {
    Accessible* widget = accessible->ContainerWidget();
    if (widget && widget->IsSelect()) {
      AccSelChangeEvent::SelChangeType selChangeType =
          aContent->AsElement()->State().HasState(NS_EVENT_STATE_CHECKED)
              ? AccSelChangeEvent::eSelectionAdd
              : AccSelChangeEvent::eSelectionRemove;
      RefPtr<AccEvent> event =
          new AccSelChangeEvent(widget, accessible, selChangeType);
      FireDelayedEvent(event);
      return;
    }

    RefPtr<AccEvent> event = new AccStateChangeEvent(
        accessible, states::CHECKED,
        aContent->AsElement()->State().HasState(NS_EVENT_STATE_CHECKED));
    FireDelayedEvent(event);
  }

  if (aStateMask.HasState(NS_EVENT_STATE_INVALID)) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(accessible, states::INVALID, true);
    FireDelayedEvent(event);
  }

  if (aStateMask.HasState(NS_EVENT_STATE_VISITED)) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(accessible, states::TRAVERSED, true);
    FireDelayedEvent(event);
  }
}

void DocAccessible::DocumentStatesChanged(nsIDocument* aDocument,
                                          EventStates aStateMask) {}

void DocAccessible::CharacterDataWillChange(nsIContent* aContent,
                                            const CharacterDataChangeInfo&) {}

void DocAccessible::CharacterDataChanged(nsIContent* aContent,
                                         const CharacterDataChangeInfo&) {}

void DocAccessible::ContentInserted(nsIContent* aChild) {}

void DocAccessible::ContentRemoved(nsIContent* aChildNode,
                                   nsIContent* aPreviousSiblingNode) {
#ifdef A11Y_LOG
  if (logging::IsEnabled(logging::eTree)) {
    logging::MsgBegin("TREE", "DOM content removed; doc: %p", this);
    logging::Node("container node", aChildNode->GetParent());
    logging::Node("content node", aChildNode);
    logging::MsgEnd();
  }
#endif
  // This one and content removal notification from layout may result in
  // double processing of same subtrees. If it pops up in profiling, then
  // consider reusing a document node cache to reject these notifications early.
  ContentRemoved(aChildNode);
}

void DocAccessible::ParentChainChanged(nsIContent* aContent) {}

  ////////////////////////////////////////////////////////////////////////////////
  // Accessible

#ifdef A11Y_LOG
nsresult DocAccessible::HandleAccEvent(AccEvent* aEvent) {
  if (logging::IsEnabled(logging::eDocLoad))
    logging::DocLoadEventHandled(aEvent);

  return HyperTextAccessible::HandleAccEvent(aEvent);
}
#endif

////////////////////////////////////////////////////////////////////////////////
// Public members

void* DocAccessible::GetNativeWindow() const {
  if (!mPresShell) return nullptr;

  nsViewManager* vm = mPresShell->GetViewManager();
  if (!vm) return nullptr;

  nsCOMPtr<nsIWidget> widget;
  vm->GetRootWidget(getter_AddRefs(widget));
  if (widget) return widget->GetNativeData(NS_NATIVE_WINDOW);

  return nullptr;
}

Accessible* DocAccessible::GetAccessibleByUniqueIDInSubtree(void* aUniqueID) {
  Accessible* child = GetAccessibleByUniqueID(aUniqueID);
  if (child) return child;

  uint32_t childDocCount = mChildDocuments.Length();
  for (uint32_t childDocIdx = 0; childDocIdx < childDocCount; childDocIdx++) {
    DocAccessible* childDocument = mChildDocuments.ElementAt(childDocIdx);
    child = childDocument->GetAccessibleByUniqueIDInSubtree(aUniqueID);
    if (child) return child;
  }

  return nullptr;
}

Accessible* DocAccessible::GetAccessibleOrContainer(nsINode* aNode) const {
  if (!aNode || !aNode->GetComposedDoc()) return nullptr;

  for (nsINode* currNode = aNode; currNode;
       currNode = currNode->GetFlattenedTreeParentNode()) {
    if (Accessible* accessible = GetAccessible(currNode)) {
      return accessible;
    }
  }

  return nullptr;
}

Accessible* DocAccessible::GetAccessibleOrDescendant(nsINode* aNode) const {
  Accessible* acc = GetAccessible(aNode);
  if (acc) return acc;

  acc = GetContainerAccessible(aNode);
  if (acc) {
    uint32_t childCnt = acc->ChildCount();
    for (uint32_t idx = 0; idx < childCnt; idx++) {
      Accessible* child = acc->GetChildAt(idx);
      for (nsIContent* elm = child->GetContent();
           elm && elm != acc->GetContent();
           elm = elm->GetFlattenedTreeParent()) {
        if (elm == aNode) return child;
      }
    }
  }

  return nullptr;
}

void DocAccessible::BindToDocument(Accessible* aAccessible,
                                   const nsRoleMapEntry* aRoleMapEntry) {
  // Put into DOM node cache.
  if (aAccessible->IsNodeMapEntry())
    mNodeToAccessibleMap.Put(aAccessible->GetNode(), aAccessible);

  // Put into unique ID cache.
  mAccessibleCache.Put(aAccessible->UniqueID(), aAccessible);

  aAccessible->SetRoleMapEntry(aRoleMapEntry);

  if (aAccessible->HasOwnContent()) {
    AddDependentIDsFor(aAccessible);

    nsIContent* content = aAccessible->GetContent();
    if (content->IsElement() && content->AsElement()->HasAttr(
                                    kNameSpaceID_None, nsGkAtoms::aria_owns)) {
      mNotificationController->ScheduleRelocation(aAccessible);
    }
  }
}

void DocAccessible::UnbindFromDocument(Accessible* aAccessible) {
  NS_ASSERTION(mAccessibleCache.GetWeak(aAccessible->UniqueID()),
               "Unbinding the unbound accessible!");

  // Fire focus event on accessible having DOM focus if active item was removed
  // from the tree.
  if (FocusMgr()->IsActiveItem(aAccessible)) {
    FocusMgr()->ActiveItemChanged(nullptr);
#ifdef A11Y_LOG
    if (logging::IsEnabled(logging::eFocus))
      logging::ActiveItemChangeCausedBy("tree shutdown", aAccessible);
#endif
  }

  // Remove an accessible from node-to-accessible map if it exists there.
  if (aAccessible->IsNodeMapEntry() &&
      mNodeToAccessibleMap.Get(aAccessible->GetNode()) == aAccessible)
    mNodeToAccessibleMap.Remove(aAccessible->GetNode());

  aAccessible->mStateFlags |= eIsNotInDocument;

  // Update XPCOM part.
  xpcAccessibleDocument* xpcDoc = GetAccService()->GetCachedXPCDocument(this);
  if (xpcDoc) xpcDoc->NotifyOfShutdown(aAccessible);

  void* uniqueID = aAccessible->UniqueID();

  NS_ASSERTION(!aAccessible->IsDefunct(), "Shutdown the shutdown accessible!");
  aAccessible->Shutdown();

  mAccessibleCache.Remove(uniqueID);
}

void DocAccessible::ContentInserted(nsIContent* aContainerNode,
                                    nsIContent* aStartChildNode,
                                    nsIContent* aEndChildNode) {
  // Ignore content insertions until we constructed accessible tree. Otherwise
  // schedule tree update on content insertion after layout.
  if (mNotificationController && HasLoadState(eTreeConstructed)) {
    // Update the whole tree of this document accessible when the container is
    // null (document element is inserted or removed).
    Accessible* container =
        aContainerNode ? AccessibleOrTrueContainer(aContainerNode) : this;
    if (container) {
      // Ignore notification if the container node is no longer in the DOM tree.
      mNotificationController->ScheduleContentInsertion(
          container, aStartChildNode, aEndChildNode);
    }
  }
}

void DocAccessible::RecreateAccessible(nsIContent* aContent) {
#ifdef A11Y_LOG
  if (logging::IsEnabled(logging::eTree)) {
    logging::MsgBegin("TREE", "accessible recreated");
    logging::Node("content", aContent);
    logging::MsgEnd();
  }
#endif

  // XXX: we shouldn't recreate whole accessible subtree, instead we should
  // subclass hide and show events to handle them separately and implement their
  // coalescence with normal hide and show events. Note, in this case they
  // should be coalesced with normal show/hide events.

  nsIContent* parent = aContent->GetFlattenedTreeParent();
  ContentRemoved(aContent);
  ContentInserted(parent, aContent, aContent->GetNextSibling());
}

void DocAccessible::ProcessInvalidationList() {
  // Invalidate children of container accessible for each element in
  // invalidation list. Allow invalidation list insertions while container
  // children are recached.
  for (uint32_t idx = 0; idx < mInvalidationList.Length(); idx++) {
    nsIContent* content = mInvalidationList[idx];
    if (!HasAccessible(content) && content->HasID()) {
      Accessible* container = GetContainerAccessible(content);
      if (container) {
        // Check if the node is a target of aria-owns, and if so, don't process
        // it here and let DoARIAOwnsRelocation process it.
        AttrRelProviderArray* list =
            mDependentIDsHash.Get(nsDependentAtomString(content->GetID()));
        bool shouldProcess = !!list;
        if (shouldProcess) {
          for (uint32_t idx = 0; idx < list->Length(); idx++) {
            if (list->ElementAt(idx)->mRelAttr == nsGkAtoms::aria_owns) {
              shouldProcess = false;
              break;
            }
          }

          if (shouldProcess) {
            ProcessContentInserted(container, content);
          }
        }
      }
    }
  }

  mInvalidationList.Clear();
}

Accessible* DocAccessible::GetAccessibleEvenIfNotInMap(nsINode* aNode) const {
  if (!aNode->IsContent() ||
      !aNode->AsContent()->IsHTMLElement(nsGkAtoms::area))
    return GetAccessible(aNode);

  // XXX Bug 135040, incorrect when multiple images use the same map.
  nsIFrame* frame = aNode->AsContent()->GetPrimaryFrame();
  nsImageFrame* imageFrame = do_QueryFrame(frame);
  if (imageFrame) {
    Accessible* parent = GetAccessible(imageFrame->GetContent());
    if (parent) {
      Accessible* area = parent->AsImageMap()->GetChildAccessibleFor(aNode);
      if (area) return area;

      return nullptr;
    }
  }

  return GetAccessible(aNode);
}

////////////////////////////////////////////////////////////////////////////////
// Protected members

void DocAccessible::NotifyOfLoading(bool aIsReloading) {
  // Mark the document accessible as loading, if it stays alive then we'll mark
  // it as loaded when we receive proper notification.
  mLoadState &= ~eDOMLoaded;

  if (!IsLoadEventTarget()) return;

  if (aIsReloading && !mLoadEventType) {
    // Fire reload and state busy events on existing document accessible while
    // event from user input flag can be calculated properly and accessible
    // is alive. When new document gets loaded then this one is destroyed.
    RefPtr<AccEvent> reloadEvent =
        new AccEvent(nsIAccessibleEvent::EVENT_DOCUMENT_RELOAD, this);
    nsEventShell::FireEvent(reloadEvent);
  }

  // Fire state busy change event. Use delayed event since we don't care
  // actually if event isn't delivered when the document goes away like a shot.
  RefPtr<AccEvent> stateEvent =
      new AccStateChangeEvent(this, states::BUSY, true);
  FireDelayedEvent(stateEvent);
}

void DocAccessible::DoInitialUpdate() {
  if (nsCoreUtils::IsTabDocument(mDocumentNode)) {
    mDocFlags |= eTabDocument;
    if (IPCAccessibilityActive()) {
      nsIDocShell* docShell = mDocumentNode->GetDocShell();
      if (RefPtr<dom::TabChild> tabChild = dom::TabChild::GetFrom(docShell)) {
        DocAccessibleChild* ipcDoc = new DocAccessibleChild(this, tabChild);
        SetIPCDoc(ipcDoc);
        if (IsRoot()) {
          tabChild->SetTopLevelDocAccessibleChild(ipcDoc);
        }

#if defined(XP_WIN)
        IAccessibleHolder holder(CreateHolderFromAccessible(WrapNotNull(this)));
        MOZ_DIAGNOSTIC_ASSERT(!holder.IsNull());
        int32_t childID = AccessibleWrap::GetChildIDFor(this);
#else
        int32_t holder = 0, childID = 0;
#endif
        tabChild->SendPDocAccessibleConstructor(ipcDoc, nullptr, 0, childID,
                                                holder);
      }
    }
  }

  mLoadState |= eTreeConstructed;

  // Set up a root element and ARIA role mapping.
  UpdateRootElIfNeeded();

  // Build initial tree.
  CacheChildrenInSubtree(this);
#ifdef A11Y_LOG
  if (logging::IsEnabled(logging::eVerbose)) {
    logging::Tree("TREE", "Initial subtree", this);
  }
#endif

  // Fire reorder event after the document tree is constructed. Note, since
  // this reorder event is processed by parent document then events targeted to
  // this document may be fired prior to this reorder event. If this is
  // a problem then consider to keep event processing per tab document.
  if (!IsRoot()) {
    RefPtr<AccReorderEvent> reorderEvent = new AccReorderEvent(Parent());
    ParentDocument()->FireDelayedEvent(reorderEvent);
  }

  if (IPCAccessibilityActive()) {
    DocAccessibleChild* ipcDoc = IPCDoc();
    MOZ_ASSERT(ipcDoc);
    if (ipcDoc) {
      for (auto idx = 0U; idx < mChildren.Length(); idx++) {
        ipcDoc->InsertIntoIpcTree(this, mChildren.ElementAt(idx), idx);
      }
    }
  }
}

void DocAccessible::ProcessLoad() {
  mLoadState |= eCompletelyLoaded;

#ifdef A11Y_LOG
  if (logging::IsEnabled(logging::eDocLoad))
    logging::DocCompleteLoad(this, IsLoadEventTarget());
#endif

  // Do not fire document complete/stop events for root chrome document
  // accessibles and for frame/iframe documents because
  // a) screen readers start working on focus event in the case of root chrome
  // documents
  // b) document load event on sub documents causes screen readers to act is if
  // entire page is reloaded.
  if (!IsLoadEventTarget()) return;

  // Fire complete/load stopped if the load event type is given.
  if (mLoadEventType) {
    RefPtr<AccEvent> loadEvent = new AccEvent(mLoadEventType, this);
    FireDelayedEvent(loadEvent);

    mLoadEventType = 0;
  }

  // Fire busy state change event.
  RefPtr<AccEvent> stateEvent =
      new AccStateChangeEvent(this, states::BUSY, false);
  FireDelayedEvent(stateEvent);
}

void DocAccessible::AddDependentIDsFor(Accessible* aRelProvider,
                                       nsAtom* aRelAttr) {
  dom::Element* relProviderEl = aRelProvider->Elm();
  if (!relProviderEl) return;

  for (uint32_t idx = 0; idx < kRelationAttrsLen; idx++) {
    nsAtom* relAttr = *kRelationAttrs[idx];
    if (aRelAttr && aRelAttr != relAttr) continue;

    if (relAttr == nsGkAtoms::_for) {
      if (!relProviderEl->IsAnyOfHTMLElements(nsGkAtoms::label,
                                              nsGkAtoms::output))
        continue;

    } else if (relAttr == nsGkAtoms::control) {
      if (!relProviderEl->IsAnyOfXULElements(nsGkAtoms::label,
                                             nsGkAtoms::description))
        continue;
    }

    IDRefsIterator iter(this, relProviderEl, relAttr);
    while (true) {
      const nsDependentSubstring id = iter.NextID();
      if (id.IsEmpty()) break;

      nsIContent* dependentContent = iter.GetElem(id);
      if (relAttr == nsGkAtoms::aria_owns && dependentContent &&
          !aRelProvider->IsAcceptableChild(dependentContent))
        continue;

      AttrRelProviderArray* providers = mDependentIDsHash.Get(id);
      if (!providers) {
        providers = new AttrRelProviderArray();
        if (providers) {
          mDependentIDsHash.Put(id, providers);
        }
      }

      if (providers) {
        AttrRelProvider* provider = new AttrRelProvider(relAttr, relProviderEl);
        if (provider) {
          providers->AppendElement(provider);

          // We've got here during the children caching. If the referenced
          // content is not accessible then store it to pend its container
          // children invalidation (this happens immediately after the caching
          // is finished).
          if (dependentContent) {
            if (!HasAccessible(dependentContent)) {
              mInvalidationList.AppendElement(dependentContent);
            }
          }
        }
      }
    }

    // If the relation attribute is given then we don't have anything else to
    // check.
    if (aRelAttr) break;
  }

  // Make sure to schedule the tree update if needed.
  mNotificationController->ScheduleProcessing();
}

void DocAccessible::RemoveDependentIDsFor(Accessible* aRelProvider,
                                          nsAtom* aRelAttr) {
  dom::Element* relProviderElm = aRelProvider->Elm();
  if (!relProviderElm) return;

  for (uint32_t idx = 0; idx < kRelationAttrsLen; idx++) {
    nsAtom* relAttr = *kRelationAttrs[idx];
    if (aRelAttr && aRelAttr != *kRelationAttrs[idx]) continue;

    IDRefsIterator iter(this, relProviderElm, relAttr);
    while (true) {
      const nsDependentSubstring id = iter.NextID();
      if (id.IsEmpty()) break;

      AttrRelProviderArray* providers = mDependentIDsHash.Get(id);
      if (providers) {
        for (uint32_t jdx = 0; jdx < providers->Length();) {
          AttrRelProvider* provider = (*providers)[jdx];
          if (provider->mRelAttr == relAttr &&
              provider->mContent == relProviderElm)
            providers->RemoveElement(provider);
          else
            jdx++;
        }
        if (providers->Length() == 0) mDependentIDsHash.Remove(id);
      }
    }

    // If the relation attribute is given then we don't have anything else to
    // check.
    if (aRelAttr) break;
  }
}

bool DocAccessible::UpdateAccessibleOnAttrChange(dom::Element* aElement,
                                                 nsAtom* aAttribute) {
  if (aAttribute == nsGkAtoms::role) {
    // It is common for js libraries to set the role on the body element after
    // the document has loaded. In this case we just update the role map entry.
    if (mContent == aElement) {
      SetRoleMapEntry(aria::GetRoleMap(aElement));
      if (mIPCDoc) {
        mIPCDoc->SendRoleChangedEvent(Role());
      }

      return true;
    }

    // Recreate the accessible when role is changed because we might require a
    // different accessible class for the new role or the accessible may expose
    // a different sets of interfaces (COM restriction).
    RecreateAccessible(aElement);

    return true;
  }

  if (aAttribute == nsGkAtoms::href) {
    // Not worth the expense to ensure which namespace these are in. It doesn't
    // kill use to recreate the accessible even if the attribute was used in
    // the wrong namespace or an element that doesn't support it.

    // Make sure the accessible is recreated asynchronously to allow the content
    // to handle the attribute change.
    RecreateAccessible(aElement);
    return true;
  }

  if (aAttribute == nsGkAtoms::aria_multiselectable &&
      aElement->HasAttr(kNameSpaceID_None, nsGkAtoms::role)) {
    // This affects whether the accessible supports SelectAccessible.
    // COM says we cannot change what interfaces are supported on-the-fly,
    // so invalidate this object. A new one will be created on demand.
    RecreateAccessible(aElement);

    return true;
  }

  return false;
}

void DocAccessible::UpdateRootElIfNeeded() {
  dom::Element* rootEl = mDocumentNode->GetBodyElement();
  if (!rootEl) {
    rootEl = mDocumentNode->GetRootElement();
  }
  if (rootEl != mContent) {
    mContent = rootEl;
    SetRoleMapEntry(aria::GetRoleMap(rootEl));
    if (mIPCDoc) {
      mIPCDoc->SendRoleChangedEvent(Role());
    }
  }
}

/**
 * Content insertion helper.
 */
class InsertIterator final {
 public:
  InsertIterator(Accessible* aContext,
                 const nsTArray<nsCOMPtr<nsIContent> >* aNodes)
      : mChild(nullptr),
        mChildBefore(nullptr),
        mWalker(aContext),
        mNodes(aNodes),
        mNodesIdx(0) {
    MOZ_ASSERT(aContext, "No context");
    MOZ_ASSERT(aNodes, "No nodes to search for accessible elements");
    MOZ_COUNT_CTOR(InsertIterator);
  }
  ~InsertIterator() { MOZ_COUNT_DTOR(InsertIterator); }

  Accessible* Context() const { return mWalker.Context(); }
  Accessible* Child() const { return mChild; }
  Accessible* ChildBefore() const { return mChildBefore; }
  DocAccessible* Document() const { return mWalker.Document(); }

  /**
   * Iterates to a next accessible within the inserted content.
   */
  bool Next();

  void Rejected() {
    mChild = nullptr;
    mChildBefore = nullptr;
  }

 private:
  Accessible* mChild;
  Accessible* mChildBefore;
  TreeWalker mWalker;

  const nsTArray<nsCOMPtr<nsIContent> >* mNodes;
  uint32_t mNodesIdx;
};

bool InsertIterator::Next() {
  if (mNodesIdx > 0) {
    Accessible* nextChild = mWalker.Next();
    if (nextChild) {
      mChildBefore = mChild;
      mChild = nextChild;
      return true;
    }
  }

  while (mNodesIdx < mNodes->Length()) {
    // Ignore nodes that are not contained by the container anymore.

    // The container might be changed, for example, because of the subsequent
    // overlapping content insertion (i.e. other content was inserted between
    // this inserted content and its container or the content was reinserted
    // into different container of unrelated part of tree). To avoid a double
    // processing of the content insertion ignore this insertion notification.
    // Note, the inserted content might be not in tree at all at this point
    // what means there's no container. Ignore the insertion too.
    nsIContent* prevNode = mNodes->SafeElementAt(mNodesIdx - 1);
    nsIContent* node = mNodes->ElementAt(mNodesIdx++);
    Accessible* container = Document()->AccessibleOrTrueContainer(node);
    if (container != Context()) {
      continue;
    }

    // HTML comboboxes have no-content list accessible as an intermediate
    // containing all options.
    if (container->IsHTMLCombobox()) {
      container = container->FirstChild();
    }

    if (!container->IsAcceptableChild(node)) {
      continue;
    }

#ifdef A11Y_LOG
    logging::TreeInfo("traversing an inserted node", logging::eVerbose,
                      "container", container, "node", node);
#endif

    // If inserted nodes are siblings then just move the walker next.
    if (mChild && prevNode && prevNode->GetNextSibling() == node) {
      Accessible* nextChild = mWalker.Scope(node);
      if (nextChild) {
        mChildBefore = mChild;
        mChild = nextChild;
        return true;
      }
    } else {
      TreeWalker finder(container);
      if (finder.Seek(node)) {
        mChild = mWalker.Scope(node);
        if (mChild) {
          MOZ_ASSERT(!mChild->IsRelocated(), "child cannot be aria owned");
          mChildBefore = finder.Prev();
          return true;
        }
      }
    }
  }

  return false;
}

void DocAccessible::ProcessContentInserted(
    Accessible* aContainer, const nsTArray<nsCOMPtr<nsIContent> >* aNodes) {
  // Process insertions if the container accessible is still in tree.
  if (!aContainer->IsInDocument()) {
    return;
  }

  // If new root content has been inserted then update it.
  if (aContainer == this) {
    UpdateRootElIfNeeded();
  }

  InsertIterator iter(aContainer, aNodes);
  if (!iter.Next()) {
    return;
  }

#ifdef A11Y_LOG
  logging::TreeInfo("children before insertion", logging::eVerbose, aContainer);
#endif

  TreeMutation mt(aContainer);
  do {
    Accessible* parent = iter.Child()->Parent();
    if (parent) {
      if (parent != aContainer) {
#ifdef A11Y_LOG
        logging::TreeInfo("stealing accessible", 0, "old parent", parent,
                          "new parent", aContainer, "child", iter.Child(),
                          nullptr);
#endif
        MOZ_ASSERT_UNREACHABLE("stealing accessible");
        continue;
      }

#ifdef A11Y_LOG
      logging::TreeInfo("binding to same parent", logging::eVerbose, "parent",
                        aContainer, "child", iter.Child(), nullptr);
#endif
      continue;
    }

    if (aContainer->InsertAfter(iter.Child(), iter.ChildBefore())) {
#ifdef A11Y_LOG
      logging::TreeInfo("accessible was inserted", 0, "container", aContainer,
                        "child", iter.Child(), nullptr);
#endif

      CreateSubtree(iter.Child());
      mt.AfterInsertion(iter.Child());
      continue;
    }

    MOZ_ASSERT_UNREACHABLE("accessible was rejected");
    iter.Rejected();
  } while (iter.Next());

  mt.Done();

#ifdef A11Y_LOG
  logging::TreeInfo("children after insertion", logging::eVerbose, aContainer);
#endif

  FireEventsOnInsertion(aContainer);
}

void DocAccessible::ProcessContentInserted(Accessible* aContainer,
                                           nsIContent* aNode) {
  if (!aContainer->IsInDocument()) {
    return;
  }

#ifdef A11Y_LOG
  logging::TreeInfo("children before insertion", logging::eVerbose, aContainer);
#endif

#ifdef A11Y_LOG
  logging::TreeInfo("traversing an inserted node", logging::eVerbose,
                    "container", aContainer, "node", aNode);
#endif

  TreeWalker walker(aContainer);
  if (aContainer->IsAcceptableChild(aNode) && walker.Seek(aNode)) {
    Accessible* child = GetAccessible(aNode);
    if (!child) {
      child = GetAccService()->CreateAccessible(aNode, aContainer);
    }

    if (child) {
      TreeMutation mt(aContainer);
      if (!aContainer->InsertAfter(child, walker.Prev())) {
        return;
      }
      CreateSubtree(child);
      mt.AfterInsertion(child);
      mt.Done();

      FireEventsOnInsertion(aContainer);
    }
  }

#ifdef A11Y_LOG
  logging::TreeInfo("children after insertion", logging::eVerbose, aContainer);
#endif
}

void DocAccessible::FireEventsOnInsertion(Accessible* aContainer) {
  // Check to see if change occurred inside an alert, and fire an EVENT_ALERT
  // if it did.
  if (aContainer->IsAlert() || aContainer->IsInsideAlert()) {
    Accessible* ancestor = aContainer;
    do {
      if (ancestor->IsAlert()) {
        FireDelayedEvent(nsIAccessibleEvent::EVENT_ALERT, ancestor);
        break;
      }
    } while ((ancestor = ancestor->Parent()));
  }
}

void DocAccessible::ContentRemoved(Accessible* aChild) {
  Accessible* parent = aChild->Parent();
  MOZ_DIAGNOSTIC_ASSERT(parent, "Unattached accessible from tree");

#ifdef A11Y_LOG
  logging::TreeInfo("process content removal", 0, "container", parent, "child",
                    aChild, nullptr);
#endif

  // XXX: event coalescence may kill us
  RefPtr<Accessible> kungFuDeathGripChild(aChild);

  TreeMutation mt(parent);
  mt.BeforeRemoval(aChild);

  if (aChild->IsDefunct()) {
    MOZ_ASSERT_UNREACHABLE("Event coalescence killed the accessible");
    mt.Done();
    return;
  }

  MOZ_DIAGNOSTIC_ASSERT(aChild->Parent(), "Alive but unparented #1");

  if (aChild->IsRelocated()) {
    nsTArray<RefPtr<Accessible> >* owned = mARIAOwnsHash.Get(parent);
    MOZ_ASSERT(owned, "IsRelocated flag is out of sync with mARIAOwnsHash");
    owned->RemoveElement(aChild);
    if (owned->Length() == 0) {
      mARIAOwnsHash.Remove(parent);
    }
  }
  MOZ_DIAGNOSTIC_ASSERT(aChild->Parent(), "Unparented #2");
  parent->RemoveChild(aChild);
  UncacheChildrenInSubtree(aChild);

  mt.Done();
}

void DocAccessible::ContentRemoved(nsIContent* aContentNode) {
  // If child node is not accessible then look for its accessible children.
  Accessible* acc = GetAccessible(aContentNode);
  if (acc) {
    ContentRemoved(acc);
  }

  dom::AllChildrenIterator iter =
      dom::AllChildrenIterator(aContentNode, nsIContent::eAllChildren, true);
  while (nsIContent* childNode = iter.GetNextChild()) {
    ContentRemoved(childNode);
  }
}

bool DocAccessible::RelocateARIAOwnedIfNeeded(nsIContent* aElement) {
  if (!aElement->HasID()) return false;

  AttrRelProviderArray* list =
      mDependentIDsHash.Get(nsDependentAtomString(aElement->GetID()));
  if (list) {
    for (uint32_t idx = 0; idx < list->Length(); idx++) {
      if (list->ElementAt(idx)->mRelAttr == nsGkAtoms::aria_owns) {
        Accessible* owner = GetAccessible(list->ElementAt(idx)->mContent);
        if (owner) {
          mNotificationController->ScheduleRelocation(owner);
          return true;
        }
      }
    }
  }

  return false;
}

void DocAccessible::DoARIAOwnsRelocation(Accessible* aOwner) {
  MOZ_ASSERT(aOwner, "aOwner must be a valid pointer");
  MOZ_ASSERT(aOwner->Elm(), "aOwner->Elm() must be a valid pointer");

#ifdef A11Y_LOG
  logging::TreeInfo("aria owns relocation", logging::eVerbose, aOwner);
#endif

  nsTArray<RefPtr<Accessible> >* owned = mARIAOwnsHash.LookupOrAdd(aOwner);

  IDRefsIterator iter(this, aOwner->Elm(), nsGkAtoms::aria_owns);
  uint32_t idx = 0;
  while (nsIContent* childEl = iter.NextElem()) {
    Accessible* child = GetAccessible(childEl);
    auto insertIdx = aOwner->ChildCount() - owned->Length() + idx;

    // Make an attempt to create an accessible if it wasn't created yet.
    if (!child) {
      if (aOwner->IsAcceptableChild(childEl)) {
        child = GetAccService()->CreateAccessible(childEl, aOwner);
        if (child) {
          TreeMutation imut(aOwner);
          aOwner->InsertChildAt(insertIdx, child);
          imut.AfterInsertion(child);
          imut.Done();

          child->SetRelocated(true);
          owned->InsertElementAt(idx, child);
          idx++;

          // Create subtree before adjusting the insertion index, since subtree
          // creation may alter children in the container.
          CreateSubtree(child);
          FireEventsOnInsertion(aOwner);
        }
      }
      continue;
    }

#ifdef A11Y_LOG
    logging::TreeInfo("aria owns traversal", logging::eVerbose, "candidate",
                      child, nullptr);
#endif

    if (owned->IndexOf(child) < idx) {
      continue;  // ignore second entry of same ID
    }

    // Same child on same position, no change.
    if (child->Parent() == aOwner) {
      int32_t indexInParent = child->IndexInParent();

      // The child is being placed in its current index,
      // eg. aria-owns='id1 id2 id3' is changed to aria-owns='id3 id2 id1'.
      if (indexInParent == static_cast<int32_t>(insertIdx)) {
        MOZ_ASSERT(child->IsRelocated(),
                   "A child, having an index in parent from aria ownded "
                   "indices range, has to be aria owned");
        MOZ_ASSERT(owned->ElementAt(idx) == child,
                   "Unexpected child in ARIA owned array");
        idx++;
        continue;
      }

      // The child is being inserted directly after its current index,
      // resulting in a no-move case. This will happen when a parent aria-owns
      // its last ordinal child:
      // <ul aria-owns='id2'><li id='id1'></li><li id='id2'></li></ul>
      if (indexInParent == static_cast<int32_t>(insertIdx) - 1) {
        MOZ_ASSERT(!child->IsRelocated(),
                   "Child should be in its ordinal position");
        child->SetRelocated(true);
        owned->InsertElementAt(idx, child);
        idx++;
        continue;
      }
    }

    MOZ_ASSERT(owned->SafeElementAt(idx) != child, "Already in place!");

    // A new child is found, check for loops.
    if (child->Parent() != aOwner) {
      // Child is aria-owned by another container, skip.
      if (child->IsRelocated()) {
        continue;
      }

      Accessible* parent = aOwner;
      while (parent && parent != child && !parent->IsDoc()) {
        parent = parent->Parent();
      }
      // A referred child cannot be a parent of the owner.
      if (parent == child) {
        continue;
      }
    }

    if (MoveChild(child, aOwner, insertIdx)) {
      child->SetRelocated(true);
      MOZ_ASSERT(owned == mARIAOwnsHash.Get(aOwner));
      owned = mARIAOwnsHash.LookupOrAdd(aOwner);
      owned->InsertElementAt(idx, child);
      idx++;
    }
  }

  // Put back children that are not seized anymore.
  PutChildrenBack(owned, idx);
  if (owned->Length() == 0) {
    mARIAOwnsHash.Remove(aOwner);
  }
}

void DocAccessible::PutChildrenBack(nsTArray<RefPtr<Accessible> >* aChildren,
                                    uint32_t aStartIdx) {
  MOZ_ASSERT(aStartIdx <= aChildren->Length(), "Wrong removal index");

  for (auto idx = aStartIdx; idx < aChildren->Length(); idx++) {
    Accessible* child = aChildren->ElementAt(idx);
    if (!child->IsInDocument()) {
      continue;
    }

    // Remove the child from the owner
    Accessible* owner = child->Parent();
    if (!owner) {
      NS_ERROR("Cannot put the child back. No parent, a broken tree.");
      continue;
    }

#ifdef A11Y_LOG
    logging::TreeInfo("aria owns put child back", 0, "old parent", owner,
                      "child", child, nullptr);
#endif

    // Unset relocated flag to find an insertion point for the child.
    child->SetRelocated(false);

    nsIContent* content = child->GetContent();
    int32_t idxInParent = -1;
    Accessible* origContainer =
        AccessibleOrTrueContainer(content->GetFlattenedTreeParentNode());
    if (origContainer) {
      TreeWalker walker(origContainer);
      if (walker.Seek(content)) {
        Accessible* prevChild = walker.Prev();
        if (prevChild) {
          idxInParent = prevChild->IndexInParent() + 1;
          MOZ_DIAGNOSTIC_ASSERT(origContainer == prevChild->Parent(),
                                "Broken tree");
          origContainer = prevChild->Parent();
        } else {
          idxInParent = 0;
        }
      }
    }

    // The child may have already be in its ordinal place for 2 reasons:
    // 1. It was the last ordinal child, and the first aria-owned child.
    //    given:      <ul id="list" aria-owns="b"><li id="a"></li><li
    //    id="b"></li></ul> after load: $("list").setAttribute("aria-owns", "");
    // 2. The preceding adopted children were just reclaimed, eg:
    //    given:      <ul id="list"><li id="b"></li></ul>
    //    after load: $("list").setAttribute("aria-owns", "a b");
    //    later:      $("list").setAttribute("aria-owns", "");
    if (origContainer != owner || child->IndexInParent() != idxInParent) {
      DebugOnly<bool> moved = MoveChild(child, origContainer, idxInParent);
      MOZ_ASSERT(moved, "Failed to put child back.");
    } else {
      MOZ_ASSERT(!child->PrevSibling() || !child->PrevSibling()->IsRelocated(),
                 "No relocated child should appear before this one");
      MOZ_ASSERT(!child->NextSibling() || child->NextSibling()->IsRelocated(),
                 "No ordinal child should appear after this one");
    }
  }

  aChildren->RemoveElementsAt(aStartIdx, aChildren->Length() - aStartIdx);
}

bool DocAccessible::MoveChild(Accessible* aChild, Accessible* aNewParent,
                              int32_t aIdxInParent) {
  MOZ_ASSERT(aChild, "No child");
  MOZ_ASSERT(aChild->Parent(), "No parent");
  MOZ_ASSERT(aIdxInParent <= static_cast<int32_t>(aNewParent->ChildCount()),
             "Wrong insertion point for a moving child");

  Accessible* curParent = aChild->Parent();

  if (!aNewParent->IsAcceptableChild(aChild->GetContent())) {
    return false;
  }

#ifdef A11Y_LOG
  logging::TreeInfo("move child", 0, "old parent", curParent, "new parent",
                    aNewParent, "child", aChild, nullptr);
#endif

  // Forget aria-owns info in case of ARIA owned element. The caller is expected
  // to update it if needed.
  if (aChild->IsRelocated()) {
    aChild->SetRelocated(false);
    nsTArray<RefPtr<Accessible> >* owned = mARIAOwnsHash.Get(curParent);
    MOZ_ASSERT(owned, "IsRelocated flag is out of sync with mARIAOwnsHash");
    owned->RemoveElement(aChild);
    if (owned->Length() == 0) {
      mARIAOwnsHash.Remove(curParent);
    }
  }

  NotificationController::MoveGuard mguard(mNotificationController);

  if (curParent == aNewParent) {
    MOZ_ASSERT(aChild->IndexInParent() != aIdxInParent, "No move case");
    curParent->MoveChild(aIdxInParent, aChild);

#ifdef A11Y_LOG
    logging::TreeInfo("move child: parent tree after", logging::eVerbose,
                      curParent);
#endif
    return true;
  }

  MOZ_ASSERT(aIdxInParent <= static_cast<int32_t>(aNewParent->ChildCount()),
             "Wrong insertion point for a moving child");

  // If the child cannot be re-inserted into the tree, then make sure to remove
  // it from its present parent and then shutdown it.
  bool hasInsertionPoint =
      (aIdxInParent != -1) ||
      (aIdxInParent <= static_cast<int32_t>(aNewParent->ChildCount()));

  TreeMutation rmut(curParent);
  rmut.BeforeRemoval(aChild, hasInsertionPoint && TreeMutation::kNoShutdown);
  curParent->RemoveChild(aChild);
  rmut.Done();

  // No insertion point for the child.
  if (!hasInsertionPoint) {
    return true;
  }

  TreeMutation imut(aNewParent);
  aNewParent->InsertChildAt(aIdxInParent, aChild);
  imut.AfterInsertion(aChild);
  imut.Done();

#ifdef A11Y_LOG
  logging::TreeInfo("move child: old parent tree after", logging::eVerbose,
                    curParent);
  logging::TreeInfo("move child: new parent tree after", logging::eVerbose,
                    aNewParent);
#endif

  return true;
}

void DocAccessible::CacheChildrenInSubtree(Accessible* aRoot,
                                           Accessible** aFocusedAcc) {
  // If the accessible is focused then report a focus event after all related
  // mutation events.
  if (aFocusedAcc && !*aFocusedAcc &&
      FocusMgr()->HasDOMFocus(aRoot->GetContent()))
    *aFocusedAcc = aRoot;

  Accessible* root = aRoot->IsHTMLCombobox() ? aRoot->FirstChild() : aRoot;
  if (root->KidsFromDOM()) {
    TreeMutation mt(root, TreeMutation::kNoEvents);
    TreeWalker walker(root);
    while (Accessible* child = walker.Next()) {
      if (child->IsBoundToParent()) {
        MoveChild(child, root, root->ChildCount());
        continue;
      }

      root->AppendChild(child);
      mt.AfterInsertion(child);

      CacheChildrenInSubtree(child, aFocusedAcc);
    }
    mt.Done();
  }

  // Fire events for ARIA elements.
  if (!aRoot->HasARIARole()) {
    return;
  }

  // XXX: we should delay document load complete event if the ARIA document
  // has aria-busy.
  roles::Role role = aRoot->ARIARole();
  if (!aRoot->IsDoc() &&
      (role == roles::DIALOG || role == roles::NON_NATIVE_DOCUMENT)) {
    FireDelayedEvent(nsIAccessibleEvent::EVENT_DOCUMENT_LOAD_COMPLETE, aRoot);
  }
}

void DocAccessible::UncacheChildrenInSubtree(Accessible* aRoot) {
  aRoot->mStateFlags |= eIsNotInDocument;
  RemoveDependentIDsFor(aRoot);

  nsTArray<RefPtr<Accessible> >* owned = mARIAOwnsHash.Get(aRoot);
  uint32_t count = aRoot->ContentChildCount();
  for (uint32_t idx = 0; idx < count; idx++) {
    Accessible* child = aRoot->ContentChildAt(idx);

    if (child->IsRelocated()) {
      MOZ_ASSERT(owned, "IsRelocated flag is out of sync with mARIAOwnsHash");
      owned->RemoveElement(child);
      if (owned->Length() == 0) {
        mARIAOwnsHash.Remove(aRoot);
        owned = nullptr;
      }
    }

    // Removing this accessible from the document doesn't mean anything about
    // accessibles for subdocuments, so skip removing those from the tree.
    if (!child->IsDoc()) {
      UncacheChildrenInSubtree(child);
    }
  }

  if (aRoot->IsNodeMapEntry() &&
      mNodeToAccessibleMap.Get(aRoot->GetNode()) == aRoot)
    mNodeToAccessibleMap.Remove(aRoot->GetNode());
}

void DocAccessible::ShutdownChildrenInSubtree(Accessible* aAccessible) {
  // Traverse through children and shutdown them before this accessible. When
  // child gets shutdown then it removes itself from children array of its
  // parent. Use jdx index to process the cases if child is not attached to the
  // parent and as result doesn't remove itself from its children.
  uint32_t count = aAccessible->ContentChildCount();
  for (uint32_t idx = 0, jdx = 0; idx < count; idx++) {
    Accessible* child = aAccessible->ContentChildAt(jdx);
    if (!child->IsBoundToParent()) {
      NS_ERROR("Parent refers to a child, child doesn't refer to parent!");
      jdx++;
    }

    // Don't cross document boundaries. The outerdoc shutdown takes care about
    // its subdocument.
    if (!child->IsDoc()) ShutdownChildrenInSubtree(child);
  }

  UnbindFromDocument(aAccessible);
}

bool DocAccessible::IsLoadEventTarget() const {
  nsCOMPtr<nsIDocShellTreeItem> treeItem = mDocumentNode->GetDocShell();
  NS_ASSERTION(treeItem, "No document shell for document!");

  nsCOMPtr<nsIDocShellTreeItem> parentTreeItem;
  treeItem->GetParent(getter_AddRefs(parentTreeItem));

  // Not a root document.
  if (parentTreeItem) {
    // Return true if it's either:
    // a) tab document;
    nsCOMPtr<nsIDocShellTreeItem> rootTreeItem;
    treeItem->GetRootTreeItem(getter_AddRefs(rootTreeItem));
    if (parentTreeItem == rootTreeItem) return true;

    // b) frame/iframe document and its parent document is not in loading state
    // Note: we can get notifications while document is loading (and thus
    // while there's no parent document yet).
    DocAccessible* parentDoc = ParentDocument();
    return parentDoc && parentDoc->HasLoadState(eCompletelyLoaded);
  }

  // It's content (not chrome) root document.
  return (treeItem->ItemType() == nsIDocShellTreeItem::typeContent);
}