RootAccessible.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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 "RootAccessible.h"

#include "mozilla/ArrayUtils.h"
#include "mozilla/PresShell.h"  // for nsAccUtils::GetDocAccessibleFor()
#include "nsXULPopupManager.h"

#define CreateEvent CreateEventA

#include "LocalAccessible-inl.h"
#include "DocAccessible-inl.h"
#include "mozilla/a11y/DocAccessibleParent.h"
#include "nsAccessibilityService.h"
#include "nsAccUtils.h"
#include "nsCoreUtils.h"
#include "nsEventShell.h"
#include "Relation.h"
#include "Role.h"
#include "States.h"
#include "XULTreeAccessible.h"

#include "mozilla/dom/BindingUtils.h"
#include "mozilla/dom/CustomEvent.h"
#include "mozilla/dom/Element.h"
#include "mozilla/dom/ScriptSettings.h"
#include "mozilla/dom/BrowserHost.h"

#include "nsIDocShellTreeOwner.h"
#include "mozilla/dom/Event.h"
#include "mozilla/dom/EventTarget.h"
#include "nsIDOMXULMultSelectCntrlEl.h"
#include "mozilla/dom/Document.h"
#include "nsIInterfaceRequestorUtils.h"
#include "nsIPropertyBag2.h"
#include "nsPIDOMWindow.h"
#include "nsIWebBrowserChrome.h"
#include "nsReadableUtils.h"
#include "nsFocusManager.h"
#include "nsGlobalWindow.h"

#include "nsIAppWindow.h"

using namespace mozilla;
using namespace mozilla::a11y;
using namespace mozilla::dom;

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

NS_IMPL_ISUPPORTS_INHERITED(RootAccessible, DocAccessible, nsIDOMEventListener)

////////////////////////////////////////////////////////////////////////////////
// Constructor/destructor

RootAccessible::RootAccessible(Document* aDocument, PresShell* aPresShell)
    : DocAccessibleWrap(aDocument, aPresShell) {
  mType = eRootType;
}

RootAccessible::~RootAccessible() {}

////////////////////////////////////////////////////////////////////////////////
// LocalAccessible

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

  if (ARIARoleMap()) {
    LocalAccessible::Name(aName);
    if (!aName.IsEmpty()) return eNameOK;
  }

  mDocumentNode->GetTitle(aName);
  return eNameOK;
}

// RootAccessible protected member
uint32_t RootAccessible::GetChromeFlags() const {
  // Return the flag set for the top level window as defined
  // by nsIWebBrowserChrome::CHROME_WINDOW_[FLAGNAME]
  // Not simple: nsIAppWindow is not just a QI from nsIDOMWindow
  nsCOMPtr<nsIDocShell> docShell = nsCoreUtils::GetDocShellFor(mDocumentNode);
  NS_ENSURE_TRUE(docShell, 0);
  nsCOMPtr<nsIDocShellTreeOwner> treeOwner;
  docShell->GetTreeOwner(getter_AddRefs(treeOwner));
  NS_ENSURE_TRUE(treeOwner, 0);
  nsCOMPtr<nsIAppWindow> appWin(do_GetInterface(treeOwner));
  if (!appWin) {
    return 0;
  }
  uint32_t chromeFlags;
  appWin->GetChromeFlags(&chromeFlags);
  return chromeFlags;
}

uint64_t RootAccessible::NativeState() const {
  uint64_t state = DocAccessibleWrap::NativeState();
  if (state & states::DEFUNCT) return state;

  uint32_t chromeFlags = GetChromeFlags();
  if (chromeFlags & nsIWebBrowserChrome::CHROME_WINDOW_RESIZE) {
    state |= states::SIZEABLE;
  }
  // If it has a titlebar it's movable
  // XXX unless it's minimized or maximized, but not sure
  //     how to detect that
  if (chromeFlags & nsIWebBrowserChrome::CHROME_TITLEBAR) {
    state |= states::MOVEABLE;
  }
  if (chromeFlags & nsIWebBrowserChrome::CHROME_MODAL) state |= states::MODAL;

  nsFocusManager* fm = nsFocusManager::GetFocusManager();
  if (fm && fm->GetActiveWindow() == mDocumentNode->GetWindow()) {
    state |= states::ACTIVE;
  }

  return state;
}

const char* const kEventTypes[] = {
#ifdef DEBUG_DRAGDROPSTART
    // Capture mouse over events and fire fake DRAGDROPSTART event to simplify
    // debugging a11y objects with event viewers.
    "mouseover",
#endif
    // Fired when list or tree selection changes.
    "select",
    // Fired when value changes immediately, wether or not focused changed.
    "ValueChange", "AlertActive", "TreeRowCountChanged", "TreeInvalidated",
    // add ourself as a OpenStateChange listener (custom event fired in
    // tree.xml)
    "OpenStateChange",
    // add ourself as a CheckboxStateChange listener (custom event fired in
    // HTMLInputElement.cpp)
    "CheckboxStateChange",
    // add ourself as a RadioStateChange Listener (custom event fired in in
    // HTMLInputElement.cpp & radio.js)
    "RadioStateChange", "popupshown", "popuphiding", "DOMMenuInactive",
    "DOMMenuItemActive", "DOMMenuItemInactive", "DOMMenuBarActive",
    "DOMMenuBarInactive", "scroll", "DOMTitleChanged"};

nsresult RootAccessible::AddEventListeners() {
  // EventTarget interface allows to register event listeners to
  // receive untrusted events (synthetic events generated by untrusted code).
  // For example, XBL bindings implementations for elements that are hosted in
  // non chrome document fire untrusted events.
  // We must use the window's parent target in order to receive events from
  // iframes and shadow DOM; e.g. ValueChange events from a <select> in an
  // iframe or shadow DOM. The root document itself doesn't receive these.
  nsPIDOMWindowOuter* window = mDocumentNode->GetWindow();
  nsCOMPtr<EventTarget> nstarget = window ? window->GetParentTarget() : nullptr;

  if (nstarget) {
    for (const char *const *e = kEventTypes, *const *e_end =
                                                 ArrayEnd(kEventTypes);
         e < e_end; ++e) {
      nsresult rv = nstarget->AddEventListener(NS_ConvertASCIItoUTF16(*e), this,
                                               true, true);
      NS_ENSURE_SUCCESS(rv, rv);
    }
  }

  return DocAccessible::AddEventListeners();
}

nsresult RootAccessible::RemoveEventListeners() {
  nsPIDOMWindowOuter* window = mDocumentNode->GetWindow();
  nsCOMPtr<EventTarget> target = window ? window->GetParentTarget() : nullptr;
  if (target) {
    for (const char *const *e = kEventTypes, *const *e_end =
                                                 ArrayEnd(kEventTypes);
         e < e_end; ++e) {
      target->RemoveEventListener(NS_ConvertASCIItoUTF16(*e), this, true);
    }
  }

  // Do this before removing clearing caret accessible, so that it can use
  // shutdown the caret accessible's selection listener
  DocAccessible::RemoveEventListeners();
  return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
// public

void RootAccessible::DocumentActivated(DocAccessible* aDocument) {}

////////////////////////////////////////////////////////////////////////////////
// nsIDOMEventListener

NS_IMETHODIMP
RootAccessible::HandleEvent(Event* aDOMEvent) {
  MOZ_ASSERT(aDOMEvent);
  if (IsDefunct()) {
    // Even though we've been shut down, RemoveEventListeners might not have
    // removed the event handlers on the window's parent target if GetWindow
    // returned null, so we might still get events here in this case. We should
    // just ignore these events.
    return NS_OK;
  }

  nsCOMPtr<nsINode> origTargetNode =
      do_QueryInterface(aDOMEvent->GetOriginalTarget());
  if (!origTargetNode) return NS_OK;

#ifdef A11Y_LOG
  if (logging::IsEnabled(logging::eDOMEvents)) {
    nsAutoString eventType;
    aDOMEvent->GetType(eventType);
    logging::DOMEvent("handled", origTargetNode, eventType);
  }
#endif

  DocAccessible* document =
      GetAccService()->GetDocAccessible(origTargetNode->OwnerDoc());

  if (document) {
    nsAutoString eventType;
    aDOMEvent->GetType(eventType);
    if (eventType.EqualsLiteral("scroll")) {
      // We don't put this in the notification queue for 2 reasons:
      // 1. We will flood the queue with repetitive events.
      // 2. Since this doesn't necessarily touch layout, we are not
      //    guaranteed to have a WillRefresh tick any time soon.
      document->HandleScroll(origTargetNode);
    } else {
      // Root accessible exists longer than any of its descendant documents so
      // that we are guaranteed notification is processed before root accessible
      // is destroyed.
      // For shadow DOM, GetOriginalTarget on the Event returns null if we
      // process the event async, so we must pass the target node as well.
      document->HandleNotification<RootAccessible, Event, nsINode>(
          this, &RootAccessible::ProcessDOMEvent, aDOMEvent, origTargetNode);
    }
  }

  return NS_OK;
}

// RootAccessible protected
void RootAccessible::ProcessDOMEvent(Event* aDOMEvent, nsINode* aTarget) {
  MOZ_ASSERT(aDOMEvent);
  MOZ_ASSERT(aTarget);

  nsAutoString eventType;
  aDOMEvent->GetType(eventType);

#ifdef A11Y_LOG
  if (logging::IsEnabled(logging::eDOMEvents)) {
    logging::DOMEvent("processed", aTarget, eventType);
  }
#endif

  if (eventType.EqualsLiteral("popuphiding")) {
    HandlePopupHidingEvent(aTarget);
    return;
  }

  DocAccessible* targetDocument =
      GetAccService()->GetDocAccessible(aTarget->OwnerDoc());
  if (!targetDocument) {
    // Document has ceased to exist.
    return;
  }

  if (eventType.EqualsLiteral("popupshown") &&
      aTarget->IsAnyOfXULElements(nsGkAtoms::tooltip, nsGkAtoms::panel)) {
    targetDocument->ContentInserted(aTarget->AsContent(),
                                    aTarget->GetNextSibling());
    return;
  }

  LocalAccessible* accessible =
      targetDocument->GetAccessibleOrContainer(aTarget);
  if (!accessible) return;

  if (accessible->IsDoc() && eventType.EqualsLiteral("DOMTitleChanged")) {
    targetDocument->FireDelayedEvent(nsIAccessibleEvent::EVENT_NAME_CHANGE,
                                     accessible);
    return;
  }

  XULTreeAccessible* treeAcc = accessible->AsXULTree();
  if (treeAcc) {
    if (eventType.EqualsLiteral("TreeRowCountChanged")) {
      HandleTreeRowCountChangedEvent(aDOMEvent, treeAcc);
      return;
    }

    if (eventType.EqualsLiteral("TreeInvalidated")) {
      HandleTreeInvalidatedEvent(aDOMEvent, treeAcc);
      return;
    }
  }

  if (eventType.EqualsLiteral("RadioStateChange")) {
    uint64_t state = accessible->State();
    bool isEnabled = (state & (states::CHECKED | states::SELECTED)) != 0;

    if (accessible->NeedsDOMUIEvent()) {
      RefPtr<AccEvent> accEvent =
          new AccStateChangeEvent(accessible, states::CHECKED, isEnabled);
      nsEventShell::FireEvent(accEvent);
    }

    if (isEnabled) {
      FocusMgr()->ActiveItemChanged(accessible);
#ifdef A11Y_LOG
      if (logging::IsEnabled(logging::eFocus)) {
        logging::ActiveItemChangeCausedBy("RadioStateChange", accessible);
      }
#endif
    }

    return;
  }

  if (eventType.EqualsLiteral("CheckboxStateChange")) {
    if (accessible->NeedsDOMUIEvent()) {
      uint64_t state = accessible->State();
      bool isEnabled = !!(state & states::CHECKED);

      RefPtr<AccEvent> accEvent =
          new AccStateChangeEvent(accessible, states::CHECKED, isEnabled);
      nsEventShell::FireEvent(accEvent);
    }
    return;
  }

  LocalAccessible* treeItemAcc = nullptr;
  // If it's a tree element, need the currently selected item.
  if (treeAcc) {
    treeItemAcc = accessible->CurrentItem();
    if (treeItemAcc) accessible = treeItemAcc;
  }

  if (treeItemAcc && eventType.EqualsLiteral("OpenStateChange")) {
    uint64_t state = accessible->State();
    bool isEnabled = (state & states::EXPANDED) != 0;

    RefPtr<AccEvent> accEvent =
        new AccStateChangeEvent(accessible, states::EXPANDED, isEnabled);
    nsEventShell::FireEvent(accEvent);
    return;
  }

  nsINode* targetNode = accessible->GetNode();
  if (treeItemAcc && eventType.EqualsLiteral("select")) {
    // XXX: We shouldn't be based on DOM select event which doesn't provide us
    // any context info. We should integrate into nsTreeSelection instead.
    // If multiselect tree, we should fire selectionadd or selection removed
    if (FocusMgr()->HasDOMFocus(targetNode)) {
      nsCOMPtr<nsIDOMXULMultiSelectControlElement> multiSel =
          targetNode->AsElement()->AsXULMultiSelectControl();
      if (!multiSel) {
        // This shouldn't be possible. All XUL trees should have
        // nsIDOMXULMultiSelectControlElement, and the tree is focused, so it
        // shouldn't be dying. Nevertheless, this sometimes happens in the wild
        // (bug 1597043).
        MOZ_ASSERT_UNREACHABLE(
            "XUL tree doesn't have nsIDOMXULMultiSelectControlElement");
        return;
      }
      nsAutoString selType;
      multiSel->GetSelType(selType);
      if (selType.IsEmpty() || !selType.EqualsLiteral("single")) {
        // XXX: We need to fire EVENT_SELECTION_ADD and EVENT_SELECTION_REMOVE
        // for each tree item. Perhaps each tree item will need to cache its
        // selection state and fire an event after a DOM "select" event when
        // that state changes. XULTreeAccessible::UpdateTreeSelection();
        nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_SELECTION_WITHIN,
                                accessible);
        return;
      }

      RefPtr<AccSelChangeEvent> selChangeEvent = new AccSelChangeEvent(
          treeAcc, treeItemAcc, AccSelChangeEvent::eSelectionAdd);
      nsEventShell::FireEvent(selChangeEvent);
      return;
    }
  } else if (eventType.EqualsLiteral("AlertActive")) {
    nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_ALERT, accessible);
  } else if (eventType.EqualsLiteral("popupshown")) {
    HandlePopupShownEvent(accessible);
  } else if (eventType.EqualsLiteral("DOMMenuInactive")) {
    if (accessible->Role() == roles::MENUPOPUP) {
      nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_MENUPOPUP_END,
                              accessible);
    }
    if (auto* focus = FocusMgr()->FocusedLocalAccessible()) {
      // Intentionally use the content tree, because Linux strips menupopups
      // from the a11y tree so accessible might be an arbitrary ancestor.
      if (focus->GetContent() &&
          focus->GetContent()->IsShadowIncludingInclusiveDescendantOf(
              aTarget)) {
        // Move the focus to the topmost menu active content if any. The
        // menu item in the parent menu will not fire a DOMMenuItemActive
        // event if it's already active.
        LocalAccessible* newActiveAccessible = nullptr;
        if (auto* pm = nsXULPopupManager::GetInstance()) {
          if (auto* content = pm->GetTopActiveMenuItemContent()) {
            newActiveAccessible =
                accessible->Document()->GetAccessible(content);
          }
        }
        FocusMgr()->ActiveItemChanged(newActiveAccessible);
#ifdef A11Y_LOG
        if (logging::IsEnabled(logging::eFocus)) {
          logging::ActiveItemChangeCausedBy("DOMMenuInactive",
                                            newActiveAccessible);
        }
#endif
      }
    }
  } else if (eventType.EqualsLiteral("DOMMenuItemActive")) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(accessible, states::ACTIVE, true);
    nsEventShell::FireEvent(event);
    FocusMgr()->ActiveItemChanged(accessible);
#ifdef A11Y_LOG
    if (logging::IsEnabled(logging::eFocus)) {
      logging::ActiveItemChangeCausedBy("DOMMenuItemActive", accessible);
    }
#endif
  } else if (eventType.EqualsLiteral("DOMMenuItemInactive")) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(accessible, states::ACTIVE, false);
    nsEventShell::FireEvent(event);

    // Process DOMMenuItemInactive event for autocomplete only because this is
    // unique widget that may acquire focus from autocomplete popup while popup
    // stays open and has no active item. In case of XUL tree autocomplete
    // popup this event is fired for tree accessible.
    LocalAccessible* widget =
        accessible->IsWidget() ? accessible : accessible->ContainerWidget();
    if (widget && widget->IsAutoCompletePopup()) {
      FocusMgr()->ActiveItemChanged(nullptr);
#ifdef A11Y_LOG
      if (logging::IsEnabled(logging::eFocus)) {
        logging::ActiveItemChangeCausedBy("DOMMenuItemInactive", accessible);
      }
#endif
    }
  } else if (eventType.EqualsLiteral(
                 "DOMMenuBarActive")) {  // Always from user input
    nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_MENU_START, accessible,
                            eFromUserInput);

    // Notify of active item change when menubar gets active and if it has
    // current item. This is a case of mouseover (set current menuitem) and
    // mouse click (activate the menubar). If menubar doesn't have current item
    // (can be a case of menubar activation from keyboard) then ignore this
    // notification because later we'll receive DOMMenuItemActive event after
    // current menuitem is set.
    LocalAccessible* activeItem = accessible->CurrentItem();
    if (activeItem) {
      FocusMgr()->ActiveItemChanged(activeItem);
#ifdef A11Y_LOG
      if (logging::IsEnabled(logging::eFocus)) {
        logging::ActiveItemChangeCausedBy("DOMMenuBarActive", accessible);
      }
#endif
    }
  } else if (eventType.EqualsLiteral(
                 "DOMMenuBarInactive")) {  // Always from user input
    nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_MENU_END, accessible,
                            eFromUserInput);

    FocusMgr()->ActiveItemChanged(nullptr);
#ifdef A11Y_LOG
    if (logging::IsEnabled(logging::eFocus)) {
      logging::ActiveItemChangeCausedBy("DOMMenuBarInactive", accessible);
    }
#endif
  } else if (accessible->NeedsDOMUIEvent() &&
             eventType.EqualsLiteral("ValueChange")) {
    uint32_t event = accessible->HasNumericValue()
                         ? nsIAccessibleEvent::EVENT_VALUE_CHANGE
                         : nsIAccessibleEvent::EVENT_TEXT_VALUE_CHANGE;
    targetDocument->FireDelayedEvent(event, accessible);
  }
#ifdef DEBUG_DRAGDROPSTART
  else if (eventType.EqualsLiteral("mouseover")) {
    nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_DRAGDROP_START,
                            accessible);
  }
#endif
}

////////////////////////////////////////////////////////////////////////////////
// LocalAccessible

void RootAccessible::Shutdown() {
  // Called manually or by LocalAccessible::LastRelease()
  if (HasShutdown()) {
    return;
  }
  DocAccessibleWrap::Shutdown();
}

Relation RootAccessible::RelationByType(RelationType aType) const {
  if (!mDocumentNode || aType != RelationType::EMBEDS) {
    return DocAccessibleWrap::RelationByType(aType);
  }

  if (RemoteAccessible* remoteDoc = GetPrimaryRemoteTopLevelContentDoc()) {
    return Relation(remoteDoc);
  }

  if (nsIDocShell* docShell = mDocumentNode->GetDocShell()) {
    nsCOMPtr<nsIDocShellTreeOwner> owner;
    docShell->GetTreeOwner(getter_AddRefs(owner));
    if (owner) {
      nsCOMPtr<nsIDocShellTreeItem> contentShell;
      owner->GetPrimaryContentShell(getter_AddRefs(contentShell));
      if (contentShell) {
        return Relation(nsAccUtils::GetDocAccessibleFor(contentShell));
      }
    }
  }

  return Relation();
}

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

void RootAccessible::HandlePopupShownEvent(LocalAccessible* aAccessible) {
  roles::Role role = aAccessible->Role();

  if (role == roles::MENUPOPUP) {
    // Don't fire menupopup events for combobox and autocomplete lists.
    nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_MENUPOPUP_START,
                            aAccessible);
    return;
  }

  if (role == roles::COMBOBOX_LIST) {
    // Fire expanded state change event for comboboxes and autocompeletes.
    LocalAccessible* combobox = aAccessible->LocalParent();
    if (!combobox) return;

    if (combobox->IsCombobox()) {
      RefPtr<AccEvent> event =
          new AccStateChangeEvent(combobox, states::EXPANDED, true);
      nsEventShell::FireEvent(event);
    }

    // If aria-activedescendant is present, redirect focus.
    // This is needed for parent process <select> dropdowns, which use a
    // menulist containing div elements instead of XUL menuitems. XUL menuitems
    // fire DOMMenuItemActive events from layout instead.
    MOZ_ASSERT(aAccessible->Elm());
    if (aAccessible->Elm()->HasAttr(nsGkAtoms::aria_activedescendant)) {
      LocalAccessible* activeDescendant = aAccessible->CurrentItem();
      if (activeDescendant) {
        FocusMgr()->ActiveItemChanged(activeDescendant, false);
#ifdef A11Y_LOG
        if (logging::IsEnabled(logging::eFocus)) {
          logging::ActiveItemChangeCausedBy("ARIA activedescendant on popup",
                                            activeDescendant);
        }
#endif
      }
    }
  }
}

void RootAccessible::HandlePopupHidingEvent(nsINode* aPopupNode) {
  DocAccessible* document = nsAccUtils::GetDocAccessibleFor(aPopupNode);
  if (!document) {
    return;
  }

  if (aPopupNode->IsAnyOfXULElements(nsGkAtoms::tooltip, nsGkAtoms::panel)) {
    document->ContentRemoved(aPopupNode->AsContent());
    return;
  }

  // Get popup accessible. There are cases when popup element isn't accessible
  // but an underlying widget is and behaves like popup, an example is
  // autocomplete popups.
  LocalAccessible* popup = document->GetAccessible(aPopupNode);
  if (!popup) {
    LocalAccessible* popupContainer =
        document->GetContainerAccessible(aPopupNode);
    if (!popupContainer) {
      return;
    }

    uint32_t childCount = popupContainer->ChildCount();
    for (uint32_t idx = 0; idx < childCount; idx++) {
      LocalAccessible* child = popupContainer->LocalChildAt(idx);
      if (child->IsAutoCompletePopup()) {
        popup = child;
        break;
      }
    }

    // No popup no events. Focus is managed by DOM. This is a case for
    // menupopups of menus on Linux since there are no accessible for popups.
    if (!popup) {
      return;
    }
  }

  // In case of autocompletes and comboboxes fire state change event for
  // expanded state. Note, HTML form autocomplete isn't a subject of state
  // change event because they aren't autocompletes strictly speaking.

  // HTML select is target of popuphidding event. Otherwise get container
  // widget. No container widget means this is either tooltip or menupopup.
  // No events in the former case.
  LocalAccessible* widget = nullptr;
  if (popup->IsCombobox()) {
    widget = popup;
  } else {
    widget = popup->ContainerWidget();
    if (!widget) {
      if (!popup->IsMenuPopup()) {
        return;
      }
      widget = popup;
    }
  }

  // Fire expanded state change event.
  if (widget->IsCombobox()) {
    RefPtr<AccEvent> event =
        new AccStateChangeEvent(widget, states::EXPANDED, false);
    document->FireDelayedEvent(event);
  }
}

static void GetPropertyBagFromEvent(Event* aEvent,
                                    nsIPropertyBag2** aPropertyBag) {
  *aPropertyBag = nullptr;

  CustomEvent* customEvent = aEvent->AsCustomEvent();
  if (!customEvent) return;

  AutoJSAPI jsapi;
  if (!jsapi.Init(customEvent->GetParentObject())) return;

  JSContext* cx = jsapi.cx();
  JS::Rooted<JS::Value> detail(cx);
  customEvent->GetDetail(cx, &detail);
  if (!detail.isObject()) return;

  JS::Rooted<JSObject*> detailObj(cx, &detail.toObject());

  nsresult rv;
  nsCOMPtr<nsIPropertyBag2> propBag;
  rv = UnwrapArg<nsIPropertyBag2>(cx, detailObj, getter_AddRefs(propBag));
  if (NS_FAILED(rv)) return;

  propBag.forget(aPropertyBag);
}

void RootAccessible::HandleTreeRowCountChangedEvent(
    Event* aEvent, XULTreeAccessible* aAccessible) {
  nsCOMPtr<nsIPropertyBag2> propBag;
  GetPropertyBagFromEvent(aEvent, getter_AddRefs(propBag));
  if (!propBag) return;

  nsresult rv;
  int32_t index, count;
  rv = propBag->GetPropertyAsInt32(u"index"_ns, &index);
  if (NS_FAILED(rv)) return;

  rv = propBag->GetPropertyAsInt32(u"count"_ns, &count);
  if (NS_FAILED(rv)) return;

  aAccessible->InvalidateCache(index, count);
}

void RootAccessible::HandleTreeInvalidatedEvent(
    Event* aEvent, XULTreeAccessible* aAccessible) {
  nsCOMPtr<nsIPropertyBag2> propBag;
  GetPropertyBagFromEvent(aEvent, getter_AddRefs(propBag));
  if (!propBag) return;

  int32_t startRow = 0, endRow = -1, startCol = 0, endCol = -1;
  propBag->GetPropertyAsInt32(u"startrow"_ns, &startRow);
  propBag->GetPropertyAsInt32(u"endrow"_ns, &endRow);
  propBag->GetPropertyAsInt32(u"startcolumn"_ns, &startCol);
  propBag->GetPropertyAsInt32(u"endcolumn"_ns, &endCol);

  aAccessible->TreeViewInvalidated(startRow, endRow, startCol, endCol);
}

RemoteAccessible* RootAccessible::GetPrimaryRemoteTopLevelContentDoc() const {
  nsCOMPtr<nsIDocShellTreeOwner> owner;
  mDocumentNode->GetDocShell()->GetTreeOwner(getter_AddRefs(owner));
  NS_ENSURE_TRUE(owner, nullptr);

  nsCOMPtr<nsIRemoteTab> remoteTab;
  owner->GetPrimaryRemoteTab(getter_AddRefs(remoteTab));
  if (!remoteTab) {
    return nullptr;
  }

  auto tab = static_cast<dom::BrowserHost*>(remoteTab.get());
  return tab->GetTopLevelDocAccessible();
}