gecko/accessible/src/base/NotificationController.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 "NotificationController.h"

#include "Accessible-inl.h"
#include "nsAccessibilityService.h"
#include "nsAccUtils.h"
#include "nsCoreUtils.h"
#include "DocAccessible-inl.h"
#include "nsEventShell.h"
#include "FocusManager.h"
#include "Role.h"
#include "TextLeafAccessible.h"
#include "TextUpdater.h"

#ifdef A11Y_LOG
#include "Logging.h"
#endif

#include "mozilla/dom/Element.h"
#include "mozilla/Telemetry.h"

using namespace mozilla;
using namespace mozilla::a11y;

// Defines the number of selection add/remove events in the queue when they
// aren't packed into single selection within event.
const unsigned int kSelChangeCountToPack = 5;

////////////////////////////////////////////////////////////////////////////////
// NotificationCollector
////////////////////////////////////////////////////////////////////////////////

NotificationController::NotificationController(DocAccessible* aDocument,
                                               nsIPresShell* aPresShell) :
  mObservingState(eNotObservingRefresh), mDocument(aDocument),
  mPresShell(aPresShell)
{
  mTextHash.Init();

  // Schedule initial accessible tree construction.
  ScheduleProcessing();
}

NotificationController::~NotificationController()
{
  NS_ASSERTION(!mDocument, "Controller wasn't shutdown properly!");
  if (mDocument)
    Shutdown();
}

////////////////////////////////////////////////////////////////////////////////
// NotificationCollector: AddRef/Release and cycle collection

NS_IMPL_CYCLE_COLLECTING_NATIVE_ADDREF(NotificationController)
NS_IMPL_CYCLE_COLLECTING_NATIVE_RELEASE(NotificationController)

NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(NotificationController)
  if (tmp->mDocument)
    tmp->Shutdown();
NS_IMPL_CYCLE_COLLECTION_UNLINK_END

NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(NotificationController)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mDocument)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mHangingChildDocuments)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mContentInsertions)
  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mEvents)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(NotificationController, AddRef)
NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(NotificationController, Release)

////////////////////////////////////////////////////////////////////////////////
// NotificationCollector: public

void
NotificationController::Shutdown()
{
  if (mObservingState != eNotObservingRefresh &&
      mPresShell->RemoveRefreshObserver(this, Flush_Display)) {
    mObservingState = eNotObservingRefresh;
  }

  // Shutdown handling child documents.
  int32_t childDocCount = mHangingChildDocuments.Length();
  for (int32_t idx = childDocCount - 1; idx >= 0; idx--) {
    if (!mHangingChildDocuments[idx]->IsDefunct())
      mHangingChildDocuments[idx]->Shutdown();
  }

  mHangingChildDocuments.Clear();

  mDocument = nullptr;
  mPresShell = nullptr;

  mTextHash.Clear();
  mContentInsertions.Clear();
  mNotifications.Clear();
  mEvents.Clear();
}

void
NotificationController::QueueEvent(AccEvent* aEvent)
{
  NS_ASSERTION((aEvent->mAccessible && aEvent->mAccessible->IsApplication()) ||
               aEvent->GetDocAccessible() == mDocument,
               "Queued event belongs to another document!");

  if (!mEvents.AppendElement(aEvent))
    return;

  // Filter events.
  CoalesceEvents();

  // Associate text change with hide event if it wasn't stolen from hiding
  // siblings during coalescence.
  AccMutationEvent* showOrHideEvent = downcast_accEvent(aEvent);
  if (showOrHideEvent && !showOrHideEvent->mTextChangeEvent)
    CreateTextChangeEventFor(showOrHideEvent);

  ScheduleProcessing();
}

void
NotificationController::ScheduleChildDocBinding(DocAccessible* aDocument)
{
  // Schedule child document binding to the tree.
  mHangingChildDocuments.AppendElement(aDocument);
  ScheduleProcessing();
}

void
NotificationController::ScheduleContentInsertion(Accessible* aContainer,
                                                 nsIContent* aStartChildNode,
                                                 nsIContent* aEndChildNode)
{
  nsRefPtr<ContentInsertion> insertion = new ContentInsertion(mDocument,
                                                              aContainer);
  if (insertion && insertion->InitChildList(aStartChildNode, aEndChildNode) &&
      mContentInsertions.AppendElement(insertion)) {
    ScheduleProcessing();
  }
}

////////////////////////////////////////////////////////////////////////////////
// NotificationCollector: protected

void
NotificationController::ScheduleProcessing()
{
  // If notification flush isn't planed yet start notification flush
  // asynchronously (after style and layout).
  if (mObservingState == eNotObservingRefresh) {
    if (mPresShell->AddRefreshObserver(this, Flush_Display))
      mObservingState = eRefreshObserving;
  }
}

bool
NotificationController::IsUpdatePending()
{
  return mPresShell->IsLayoutFlushObserver() ||
    mObservingState == eRefreshProcessingForUpdate ||
    mContentInsertions.Length() != 0 || mNotifications.Length() != 0 ||
    mTextHash.Count() != 0 ||
    !mDocument->HasLoadState(DocAccessible::eTreeConstructed);
}

////////////////////////////////////////////////////////////////////////////////
// NotificationCollector: private

void
NotificationController::WillRefresh(mozilla::TimeStamp aTime)
{
  Telemetry::AutoTimer<Telemetry::A11Y_UPDATE_TIME> updateTimer;

  // If the document accessible that notification collector was created for is
  // now shut down, don't process notifications anymore.
  NS_ASSERTION(mDocument,
               "The document was shut down while refresh observer is attached!");
  if (!mDocument)
    return;

  // Any generic notifications should be queued if we're processing content
  // insertions or generic notifications.
  mObservingState = eRefreshProcessingForUpdate;

  // Initial accessible tree construction.
  if (!mDocument->HasLoadState(DocAccessible::eTreeConstructed)) {
    // If document is not bound to parent at this point then the document is not
    // ready yet (process notifications later).
    if (!mDocument->IsBoundToParent()) {
      mObservingState = eRefreshObserving;
      return;
    }

#ifdef A11Y_LOG
    if (logging::IsEnabled(logging::eTree)) {
      logging::MsgBegin("TREE", "initial tree created");
      logging::Address("document", mDocument);
      logging::MsgEnd();
    }
#endif

    mDocument->DoInitialUpdate();

    NS_ASSERTION(mContentInsertions.Length() == 0,
                 "Pending content insertions while initial accessible tree isn't created!");
  }

  // Initialize scroll support if needed.
  if (!(mDocument->mDocFlags & DocAccessible::eScrollInitialized))
    mDocument->AddScrollListener();

  // Process content inserted notifications to update the tree. Process other
  // notifications like DOM events and then flush event queue. If any new
  // notifications are queued during this processing then they will be processed
  // on next refresh. If notification processing queues up new events then they
  // are processed in this refresh. If events processing queues up new events
  // then new events are processed on next refresh.
  // Note: notification processing or event handling may shut down the owning
  // document accessible.

  // Process only currently queued content inserted notifications.
  nsTArray<nsRefPtr<ContentInsertion> > contentInsertions;
  contentInsertions.SwapElements(mContentInsertions);

  uint32_t insertionCount = contentInsertions.Length();
  for (uint32_t idx = 0; idx < insertionCount; idx++) {
    contentInsertions[idx]->Process();
    if (!mDocument)
      return;
  }

  // Process rendered text change notifications.
  mTextHash.EnumerateEntries(TextEnumerator, mDocument);
  mTextHash.Clear();

  // Bind hanging child documents.
  uint32_t hangingDocCnt = mHangingChildDocuments.Length();
  for (uint32_t idx = 0; idx < hangingDocCnt; idx++) {
    DocAccessible* childDoc = mHangingChildDocuments[idx];
    if (childDoc->IsDefunct())
      continue;

    nsIContent* ownerContent = mDocument->DocumentNode()->
      FindContentForSubDocument(childDoc->DocumentNode());
    if (ownerContent) {
      Accessible* outerDocAcc = mDocument->GetAccessible(ownerContent);
      if (outerDocAcc && outerDocAcc->AppendChild(childDoc)) {
        if (mDocument->AppendChildDocument(childDoc))
          continue;

        outerDocAcc->RemoveChild(childDoc);
      }

      // Failed to bind the child document, destroy it.
      childDoc->Shutdown();
    }
  }
  mHangingChildDocuments.Clear();

  // If the document is ready and all its subdocuments are completely loaded
  // then process the document load.
  if (mDocument->HasLoadState(DocAccessible::eReady) &&
      !mDocument->HasLoadState(DocAccessible::eCompletelyLoaded) &&
      hangingDocCnt == 0) {
    uint32_t childDocCnt = mDocument->ChildDocumentCount(), childDocIdx = 0;
    for (; childDocIdx < childDocCnt; childDocIdx++) {
      DocAccessible* childDoc = mDocument->GetChildDocumentAt(childDocIdx);
      if (!childDoc->HasLoadState(DocAccessible::eCompletelyLoaded))
        break;
    }

    if (childDocIdx == childDocCnt) {
      mDocument->ProcessLoad();
      if (!mDocument)
        return;
    }
  }

  // Process only currently queued generic notifications.
  nsTArray < nsRefPtr<Notification> > notifications;
  notifications.SwapElements(mNotifications);

  uint32_t notificationCount = notifications.Length();
  for (uint32_t idx = 0; idx < notificationCount; idx++) {
    notifications[idx]->Process();
    if (!mDocument)
      return;
  }

  // Process invalidation list of the document after all accessible tree
  // modification are done.
  mDocument->ProcessInvalidationList();

  // If a generic notification occurs after this point then we may be allowed to
  // process it synchronously.
  mObservingState = eRefreshObserving;

  ProcessEventQueue();
  if (!mDocument)
    return;

  // Stop further processing if there are no new notifications of any kind or
  // events and document load is processed.
  if (mContentInsertions.Length() == 0 && mNotifications.Length() == 0 &&
      mEvents.Length() == 0 && mTextHash.Count() == 0 &&
      mHangingChildDocuments.Length() == 0 &&
      mDocument->HasLoadState(DocAccessible::eCompletelyLoaded) &&
      mPresShell->RemoveRefreshObserver(this, Flush_Display)) {
    mObservingState = eNotObservingRefresh;
  }
}

void
NotificationController::CoalesceEvents()
{
  NS_ASSERTION(mEvents.Length(), "There should be at least one pending event!");
  uint32_t tail = mEvents.Length() - 1;
  AccEvent* tailEvent = mEvents[tail];

  switch(tailEvent->mEventRule) {
    case AccEvent::eCoalesceReorder:
      CoalesceReorderEvents(tailEvent);
      break; // case eCoalesceReorder

    case AccEvent::eCoalesceMutationTextChange:
    {
      for (uint32_t index = tail - 1; index < tail; index--) {
        AccEvent* thisEvent = mEvents[index];
        if (thisEvent->mEventRule != tailEvent->mEventRule)
          continue;

        // We don't currently coalesce text change events from show/hide events.
        if (thisEvent->mEventType != tailEvent->mEventType)
          continue;

        // Show events may be duped because of reinsertion (removal is ignored
        // because initial insertion is not processed). Ignore initial
        // insertion.
        if (thisEvent->mAccessible == tailEvent->mAccessible)
          thisEvent->mEventRule = AccEvent::eDoNotEmit;

        AccMutationEvent* tailMutationEvent = downcast_accEvent(tailEvent);
        AccMutationEvent* thisMutationEvent = downcast_accEvent(thisEvent);
        if (tailMutationEvent->mParent != thisMutationEvent->mParent)
          continue;

        // Coalesce text change events for hide and show events.
        if (thisMutationEvent->IsHide()) {
          AccHideEvent* tailHideEvent = downcast_accEvent(tailEvent);
          AccHideEvent* thisHideEvent = downcast_accEvent(thisEvent);
          CoalesceTextChangeEventsFor(tailHideEvent, thisHideEvent);
          break;
        }

        AccShowEvent* tailShowEvent = downcast_accEvent(tailEvent);
        AccShowEvent* thisShowEvent = downcast_accEvent(thisEvent);
        CoalesceTextChangeEventsFor(tailShowEvent, thisShowEvent);
        break;
      }
    } break; // case eCoalesceMutationTextChange

    case AccEvent::eCoalesceOfSameType:
    {
      // Coalesce old events by newer event.
      for (uint32_t index = tail - 1; index < tail; index--) {
        AccEvent* accEvent = mEvents[index];
        if (accEvent->mEventType == tailEvent->mEventType &&
          accEvent->mEventRule == tailEvent->mEventRule) {
          accEvent->mEventRule = AccEvent::eDoNotEmit;
          return;
        }
      }
    } break; // case eCoalesceOfSameType

    case AccEvent::eCoalesceSelectionChange:
    {
      AccSelChangeEvent* tailSelChangeEvent = downcast_accEvent(tailEvent);
      for (uint32_t index = tail - 1; index < tail; index--) {
        AccEvent* thisEvent = mEvents[index];
        if (thisEvent->mEventRule == tailEvent->mEventRule) {
          AccSelChangeEvent* thisSelChangeEvent =
            downcast_accEvent(thisEvent);

          // Coalesce selection change events within same control.
          if (tailSelChangeEvent->mWidget == thisSelChangeEvent->mWidget) {
            CoalesceSelChangeEvents(tailSelChangeEvent, thisSelChangeEvent, index);
            return;
          }
        }
      }

    } break; // eCoalesceSelectionChange

    case AccEvent::eCoalesceStateChange:
    {
      // If state change event is duped then ignore previous event. If state
      // change event is opposite to previous event then no event is emitted
      // (accessible state wasn't changed).
      for (uint32_t index = tail - 1; index < tail; index--) {
        AccEvent* thisEvent = mEvents[index];
        if (thisEvent->mEventRule != AccEvent::eDoNotEmit &&
            thisEvent->mEventType == tailEvent->mEventType &&
            thisEvent->mAccessible == tailEvent->mAccessible) {
          AccStateChangeEvent* thisSCEvent = downcast_accEvent(thisEvent);
          AccStateChangeEvent* tailSCEvent = downcast_accEvent(tailEvent);
          if (thisSCEvent->mState == tailSCEvent->mState) {
            thisEvent->mEventRule = AccEvent::eDoNotEmit;
            if (thisSCEvent->mIsEnabled != tailSCEvent->mIsEnabled)
              tailEvent->mEventRule = AccEvent::eDoNotEmit;
          }
        }
      }
      break; // eCoalesceStateChange
    }

    case AccEvent::eRemoveDupes:
    {
      // Check for repeat events, coalesce newly appended event by more older
      // event.
      for (uint32_t index = tail - 1; index < tail; index--) {
        AccEvent* accEvent = mEvents[index];
        if (accEvent->mEventType == tailEvent->mEventType &&
          accEvent->mEventRule == tailEvent->mEventRule &&
          accEvent->mAccessible == tailEvent->mAccessible) {
          tailEvent->mEventRule = AccEvent::eDoNotEmit;
          return;
        }
      }
    } break; // case eRemoveDupes

    default:
      break; // case eAllowDupes, eDoNotEmit
  } // switch
}

void
NotificationController::CoalesceReorderEvents(AccEvent* aTailEvent)
{
  uint32_t count = mEvents.Length();
  for (uint32_t index = count - 2; index < count; index--) {
    AccEvent* thisEvent = mEvents[index];

    // Skip events of different types and targeted to application accessible.
    if (thisEvent->mEventType != aTailEvent->mEventType ||
        thisEvent->mAccessible->IsApplication())
      continue;

    // If thisEvent target is not in document longer, i.e. if it was
    // removed from the tree then do not emit the event.
    if (!thisEvent->mAccessible->IsDoc() &&
        !thisEvent->mAccessible->IsInDocument()) {
      thisEvent->mEventRule = AccEvent::eDoNotEmit;
      continue;
    }

    // Coalesce earlier event of the same target.
    if (thisEvent->mAccessible == aTailEvent->mAccessible) {
      if (thisEvent->mEventRule == AccEvent::eDoNotEmit) {
        AccReorderEvent* tailReorder = downcast_accEvent(aTailEvent);
        tailReorder->DoNotEmitAll();
      } else {
        thisEvent->mEventRule = AccEvent::eDoNotEmit;
      }

      return;
    }

    // If tailEvent contains thisEvent
    // then
    //   if show of tailEvent contains a grand parent of thisEvent
    //   then assert
    //   else if hide of tailEvent contains a grand parent of thisEvent
    //   then ignore thisEvent and its show and hide events
    //   otherwise ignore thisEvent but not its show and hide events
    Accessible* thisParent = thisEvent->mAccessible;
    while (thisParent && thisParent != mDocument) {
      if (thisParent->Parent() == aTailEvent->mAccessible) {
        AccReorderEvent* tailReorder = downcast_accEvent(aTailEvent);
        uint32_t eventType = tailReorder->IsShowHideEventTarget(thisParent);

        if (eventType == nsIAccessibleEvent::EVENT_SHOW) {
           NS_ERROR("Accessible tree was created after it was modified! Huh?");
        } else if (eventType == nsIAccessibleEvent::EVENT_HIDE) {
          AccReorderEvent* thisReorder = downcast_accEvent(thisEvent);
          thisReorder->DoNotEmitAll();
        } else {
          thisEvent->mEventRule = AccEvent::eDoNotEmit;
        }

        return;
      }

      thisParent = thisParent->Parent();
    }

    // If tailEvent is contained by thisEvent
    // then
    //   if show of thisEvent contains the tailEvent
    //   then ignore tailEvent
    //   if hide of thisEvent contains the tailEvent
    //   then assert
    //   otherwise ignore tailEvent but not its show and hide events
    Accessible* tailParent = aTailEvent->mAccessible;
    while (tailParent && tailParent != mDocument) {
      if (tailParent->Parent() == thisEvent->mAccessible) {
        AccReorderEvent* thisReorder = downcast_accEvent(thisEvent);
        AccReorderEvent* tailReorder = downcast_accEvent(aTailEvent);
        uint32_t eventType = thisReorder->IsShowHideEventTarget(tailParent);
        if (eventType == nsIAccessibleEvent::EVENT_SHOW)
          tailReorder->DoNotEmitAll();
        else if (eventType == nsIAccessibleEvent::EVENT_HIDE)
          NS_ERROR("Accessible tree was modified after it was removed! Huh?");
        else
          aTailEvent->mEventRule = AccEvent::eDoNotEmit;

        return;
      }

      tailParent = tailParent->Parent();
    }

  } // for (index)
}

void
NotificationController::CoalesceSelChangeEvents(AccSelChangeEvent* aTailEvent,
                                                AccSelChangeEvent* aThisEvent,
                                                uint32_t aThisIndex)
{
  aTailEvent->mPreceedingCount = aThisEvent->mPreceedingCount + 1;

  // Pack all preceding events into single selection within event
  // when we receive too much selection add/remove events.
  if (aTailEvent->mPreceedingCount >= kSelChangeCountToPack) {
    aTailEvent->mEventType = nsIAccessibleEvent::EVENT_SELECTION_WITHIN;
    aTailEvent->mAccessible = aTailEvent->mWidget;
    aThisEvent->mEventRule = AccEvent::eDoNotEmit;

    // Do not emit any preceding selection events for same widget if they
    // weren't coalesced yet.
    if (aThisEvent->mEventType != nsIAccessibleEvent::EVENT_SELECTION_WITHIN) {
      for (uint32_t jdx = aThisIndex - 1; jdx < aThisIndex; jdx--) {
        AccEvent* prevEvent = mEvents[jdx];
        if (prevEvent->mEventRule == aTailEvent->mEventRule) {
          AccSelChangeEvent* prevSelChangeEvent =
            downcast_accEvent(prevEvent);
          if (prevSelChangeEvent->mWidget == aTailEvent->mWidget)
            prevSelChangeEvent->mEventRule = AccEvent::eDoNotEmit;
        }
      }
    }
    return;
  }

  // Pack sequential selection remove and selection add events into
  // single selection change event.
  if (aTailEvent->mPreceedingCount == 1 &&
      aTailEvent->mItem != aThisEvent->mItem) {
    if (aTailEvent->mSelChangeType == AccSelChangeEvent::eSelectionAdd &&
        aThisEvent->mSelChangeType == AccSelChangeEvent::eSelectionRemove) {
      aThisEvent->mEventRule = AccEvent::eDoNotEmit;
      aTailEvent->mEventType = nsIAccessibleEvent::EVENT_SELECTION;
      aTailEvent->mPackedEvent = aThisEvent;
      return;
    }

    if (aThisEvent->mSelChangeType == AccSelChangeEvent::eSelectionAdd &&
        aTailEvent->mSelChangeType == AccSelChangeEvent::eSelectionRemove) {
      aTailEvent->mEventRule = AccEvent::eDoNotEmit;
      aThisEvent->mEventType = nsIAccessibleEvent::EVENT_SELECTION;
      aThisEvent->mPackedEvent = aThisEvent;
      return;
    }
  }

  // Unpack the packed selection change event because we've got one
  // more selection add/remove.
  if (aThisEvent->mEventType == nsIAccessibleEvent::EVENT_SELECTION) {
    if (aThisEvent->mPackedEvent) {
      aThisEvent->mPackedEvent->mEventType =
        aThisEvent->mPackedEvent->mSelChangeType == AccSelChangeEvent::eSelectionAdd ?
          nsIAccessibleEvent::EVENT_SELECTION_ADD :
          nsIAccessibleEvent::EVENT_SELECTION_REMOVE;

      aThisEvent->mPackedEvent->mEventRule =
        AccEvent::eCoalesceSelectionChange;

      aThisEvent->mPackedEvent = nullptr;
    }

    aThisEvent->mEventType =
      aThisEvent->mSelChangeType == AccSelChangeEvent::eSelectionAdd ?
        nsIAccessibleEvent::EVENT_SELECTION_ADD :
        nsIAccessibleEvent::EVENT_SELECTION_REMOVE;

    return;
  }

  // Convert into selection add since control has single selection but other
  // selection events for this control are queued.
  if (aTailEvent->mEventType == nsIAccessibleEvent::EVENT_SELECTION)
    aTailEvent->mEventType = nsIAccessibleEvent::EVENT_SELECTION_ADD;
}

void
NotificationController::CoalesceTextChangeEventsFor(AccHideEvent* aTailEvent,
                                                    AccHideEvent* aThisEvent)
{
  // XXX: we need a way to ignore SplitNode and JoinNode() when they do not
  // affect the text within the hypertext.

  AccTextChangeEvent* textEvent = aThisEvent->mTextChangeEvent;
  if (!textEvent)
    return;

  if (aThisEvent->mNextSibling == aTailEvent->mAccessible) {
    aTailEvent->mAccessible->AppendTextTo(textEvent->mModifiedText);

  } else if (aThisEvent->mPrevSibling == aTailEvent->mAccessible) {
    uint32_t oldLen = textEvent->GetLength();
    aTailEvent->mAccessible->AppendTextTo(textEvent->mModifiedText);
    textEvent->mStart -= textEvent->GetLength() - oldLen;
  }

  aTailEvent->mTextChangeEvent.swap(aThisEvent->mTextChangeEvent);
}

void
NotificationController::CoalesceTextChangeEventsFor(AccShowEvent* aTailEvent,
                                                    AccShowEvent* aThisEvent)
{
  AccTextChangeEvent* textEvent = aThisEvent->mTextChangeEvent;
  if (!textEvent)
    return;

  if (aTailEvent->mAccessible->IndexInParent() ==
      aThisEvent->mAccessible->IndexInParent() + 1) {
    // If tail target was inserted after this target, i.e. tail target is next
    // sibling of this target.
    aTailEvent->mAccessible->AppendTextTo(textEvent->mModifiedText);

  } else if (aTailEvent->mAccessible->IndexInParent() ==
             aThisEvent->mAccessible->IndexInParent() -1) {
    // If tail target was inserted before this target, i.e. tail target is
    // previous sibling of this target.
    nsAutoString startText;
    aTailEvent->mAccessible->AppendTextTo(startText);
    textEvent->mModifiedText = startText + textEvent->mModifiedText;
    textEvent->mStart -= startText.Length();
  }

  aTailEvent->mTextChangeEvent.swap(aThisEvent->mTextChangeEvent);
}

void
NotificationController::CreateTextChangeEventFor(AccMutationEvent* aEvent)
{
  Accessible* container = aEvent->mAccessible->Parent();
  if (!container)
    return;

  HyperTextAccessible* textAccessible = container->AsHyperText();
  if (!textAccessible)
    return;

  // Don't fire event for the first html:br in an editor.
  if (aEvent->mAccessible->Role() == roles::WHITESPACE) {
    nsCOMPtr<nsIEditor> editor = textAccessible->GetEditor();
    if (editor) {
      bool isEmpty = false;
      editor->GetDocumentIsEmpty(&isEmpty);
      if (isEmpty)
        return;
    }
  }

  int32_t offset = textAccessible->GetChildOffset(aEvent->mAccessible);

  nsAutoString text;
  aEvent->mAccessible->AppendTextTo(text);
  if (text.IsEmpty())
    return;

  aEvent->mTextChangeEvent =
    new AccTextChangeEvent(textAccessible, offset, text, aEvent->IsShow(),
                           aEvent->mIsFromUserInput ? eFromUserInput : eNoUserInput);
}

////////////////////////////////////////////////////////////////////////////////
// NotificationController: event queue

void
NotificationController::ProcessEventQueue()
{
  // Process only currently queued events.
  nsTArray<nsRefPtr<AccEvent> > events;
  events.SwapElements(mEvents);

  uint32_t eventCount = events.Length();
#ifdef A11Y_LOG
  if (eventCount > 0 && logging::IsEnabled(logging::eEvents)) {
    logging::MsgBegin("EVENTS", "events processing");
    logging::Address("document", mDocument);
    logging::MsgEnd();
  }
#endif

  for (uint32_t idx = 0; idx < eventCount; idx++) {
    AccEvent* event = events[idx];
    if (event->mEventRule != AccEvent::eDoNotEmit) {
      Accessible* target = event->GetAccessible();
      if (!target || target->IsDefunct())
        continue;

      // Dispatch the focus event if target is still focused.
      if (event->mEventType == nsIAccessibleEvent::EVENT_FOCUS) {
        FocusMgr()->ProcessFocusEvent(event);
        continue;
      }

      // Dispatch caret moved and text selection change events.
      if (event->mEventType == nsIAccessibleEvent::EVENT_TEXT_CARET_MOVED) {
        AccCaretMoveEvent* caretMoveEvent = downcast_accEvent(event);
        HyperTextAccessible* hyperText = target->AsHyperText();
        if (hyperText &&
            NS_SUCCEEDED(hyperText->GetCaretOffset(&caretMoveEvent->mCaretOffset))) {

          nsEventShell::FireEvent(caretMoveEvent);

          // There's a selection so fire selection change as well.
          int32_t selectionCount;
          hyperText->GetSelectionCount(&selectionCount);
          if (selectionCount)
            nsEventShell::FireEvent(nsIAccessibleEvent::EVENT_TEXT_SELECTION_CHANGED,
                                    hyperText);
        }
        continue;
      }

      nsEventShell::FireEvent(event);

      // Fire text change events.
      AccMutationEvent* mutationEvent = downcast_accEvent(event);
      if (mutationEvent) {
        if (mutationEvent->mTextChangeEvent)
          nsEventShell::FireEvent(mutationEvent->mTextChangeEvent);
      }
    }

    if (event->mEventType == nsIAccessibleEvent::EVENT_HIDE)
      mDocument->ShutdownChildrenInSubtree(event->mAccessible);

    if (!mDocument)
      return;
  }
}

////////////////////////////////////////////////////////////////////////////////
// Notification controller: text leaf accessible text update

PLDHashOperator
NotificationController::TextEnumerator(nsCOMPtrHashKey<nsIContent>* aEntry,
                                       void* aUserArg)
{
  DocAccessible* document = static_cast<DocAccessible*>(aUserArg);
  nsIContent* textNode = aEntry->GetKey();
  Accessible* textAcc = document->GetAccessible(textNode);

  // If the text node is not in tree or doesn't have frame then this case should
  // have been handled already by content removal notifications.
  nsINode* containerNode = textNode->GetParentNode();
  if (!containerNode) {
    NS_ASSERTION(!textAcc,
                 "Text node was removed but accessible is kept alive!");
    return PL_DHASH_NEXT;
  }

  nsIFrame* textFrame = textNode->GetPrimaryFrame();
  if (!textFrame) {
    NS_ASSERTION(!textAcc,
                 "Text node isn't rendered but accessible is kept alive!");
    return PL_DHASH_NEXT;
  }

  nsIContent* containerElm = containerNode->IsElement() ?
    containerNode->AsElement() : nullptr;

  nsAutoString text;
  textFrame->GetRenderedText(&text);

  // Remove text accessible if rendered text is empty.
  if (textAcc) {
    if (text.IsEmpty()) {
#ifdef A11Y_LOG
      if (logging::IsEnabled(logging::eTree | logging::eText)) {
        logging::MsgBegin("TREE", "text node lost its content");
        logging::Node("container", containerElm);
        logging::Node("content", textNode);
        logging::MsgEnd();
      }
#endif

      document->ContentRemoved(containerElm, textNode);
      return PL_DHASH_NEXT;
    }

    // Update text of the accessible and fire text change events.
#ifdef A11Y_LOG
    if (logging::IsEnabled(logging::eText)) {
      logging::MsgBegin("TEXT", "text may be changed");
      logging::Node("container", containerElm);
      logging::Node("content", textNode);
      logging::MsgEntry("old text '%s'",
                        NS_ConvertUTF16toUTF8(textAcc->AsTextLeaf()->Text()).get());
      logging::MsgEntry("new text: '%s'",
                        NS_ConvertUTF16toUTF8(text).get());
      logging::MsgEnd();
    }
#endif

    TextUpdater::Run(document, textAcc->AsTextLeaf(), text);
    return PL_DHASH_NEXT;
  }

  // Append an accessible if rendered text is not empty.
  if (!text.IsEmpty()) {
#ifdef A11Y_LOG
    if (logging::IsEnabled(logging::eTree | logging::eText)) {
      logging::MsgBegin("TREE", "text node gains new content");
      logging::Node("container", containerElm);
      logging::Node("content", textNode);
      logging::MsgEnd();
    }
#endif

    // Make sure the text node is in accessible document still.
    Accessible* container = document->GetAccessibleOrContainer(containerNode);
    NS_ASSERTION(container,
                 "Text node having rendered text hasn't accessible document!");
    if (container) {
      nsTArray<nsCOMPtr<nsIContent> > insertedContents;
      insertedContents.AppendElement(textNode);
      document->ProcessContentInserted(container, &insertedContents);
    }
  }

  return PL_DHASH_NEXT;
}


////////////////////////////////////////////////////////////////////////////////
// NotificationController: content inserted notification

NotificationController::ContentInsertion::
  ContentInsertion(DocAccessible* aDocument, Accessible* aContainer) :
  mDocument(aDocument), mContainer(aContainer)
{
}

bool
NotificationController::ContentInsertion::
  InitChildList(nsIContent* aStartChildNode, nsIContent* aEndChildNode)
{
  bool haveToUpdate = false;

  nsIContent* node = aStartChildNode;
  while (node != aEndChildNode) {
    // Notification triggers for content insertion even if no content was
    // actually inserted, check if the given content has a frame to discard
    // this case early.
    if (node->GetPrimaryFrame()) {
      if (mInsertedContent.AppendElement(node))
        haveToUpdate = true;
    }

    node = node->GetNextSibling();
  }

  return haveToUpdate;
}

NS_IMPL_CYCLE_COLLECTION_1(NotificationController::ContentInsertion,
                           mContainer)

NS_IMPL_CYCLE_COLLECTION_ROOT_NATIVE(NotificationController::ContentInsertion,
                                     AddRef)
NS_IMPL_CYCLE_COLLECTION_UNROOT_NATIVE(NotificationController::ContentInsertion,
                                       Release)

void
NotificationController::ContentInsertion::Process()
{
  mDocument->ProcessContentInserted(mContainer, &mInsertedContent);

  mDocument = nullptr;
  mContainer = nullptr;
  mInsertedContent.Clear();
}