content/browser/accessibility/browser_accessibility_manager.cc

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/accessibility/browser_accessibility_manager.h"

#include <stddef.h>

#include "base/logging.h"
#include "build/build_config.h"
#include "content/browser/accessibility/browser_accessibility.h"
#include "content/common/accessibility_messages.h"
#include "ui/accessibility/ax_tree_serializer.h"

namespace content {

namespace {

// Search the tree recursively from |node| and return any node that has
// a child tree ID of |ax_tree_id|.
BrowserAccessibility* FindNodeWithChildTreeId(BrowserAccessibility* node,
                                              int ax_tree_id) {
  if (!node)
    return nullptr;

  if (node->GetIntAttribute(ui::AX_ATTR_CHILD_TREE_ID) == ax_tree_id)
    return node;

  for (unsigned int i = 0; i < node->InternalChildCount(); ++i) {
    BrowserAccessibility* child = node->InternalGetChild(i);
    BrowserAccessibility* result = FindNodeWithChildTreeId(child, ax_tree_id);
    if (result)
      return result;
  }

  return nullptr;
}

}  // namespace

// Map from AXTreeID to BrowserAccessibilityManager
using AXTreeIDMap =
    base::hash_map<AXTreeIDRegistry::AXTreeID, BrowserAccessibilityManager*>;
base::LazyInstance<AXTreeIDMap> g_ax_tree_id_map = LAZY_INSTANCE_INITIALIZER;

// A function to call when focus changes, for testing only.
base::LazyInstance<base::Closure> g_focus_change_callback_for_testing =
    LAZY_INSTANCE_INITIALIZER;

ui::AXTreeUpdate MakeAXTreeUpdate(
    const ui::AXNodeData& node1,
    const ui::AXNodeData& node2 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node3 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node4 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node5 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node6 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node7 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node8 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node9 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node10 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node11 /* = ui::AXNodeData() */,
    const ui::AXNodeData& node12 /* = ui::AXNodeData() */) {
  CR_DEFINE_STATIC_LOCAL(ui::AXNodeData, empty_data, ());
  int32_t no_id = empty_data.id;

  ui::AXTreeUpdate update;
  update.root_id = node1.id;
  update.nodes.push_back(node1);
  if (node2.id != no_id)
    update.nodes.push_back(node2);
  if (node3.id != no_id)
    update.nodes.push_back(node3);
  if (node4.id != no_id)
    update.nodes.push_back(node4);
  if (node5.id != no_id)
    update.nodes.push_back(node5);
  if (node6.id != no_id)
    update.nodes.push_back(node6);
  if (node7.id != no_id)
    update.nodes.push_back(node7);
  if (node8.id != no_id)
    update.nodes.push_back(node8);
  if (node9.id != no_id)
    update.nodes.push_back(node9);
  if (node10.id != no_id)
    update.nodes.push_back(node10);
  if (node11.id != no_id)
    update.nodes.push_back(node11);
  if (node12.id != no_id)
    update.nodes.push_back(node12);
  return update;
}

BrowserAccessibility* BrowserAccessibilityFactory::Create() {
  return BrowserAccessibility::Create();
}

BrowserAccessibilityFindInPageInfo::BrowserAccessibilityFindInPageInfo()
    : request_id(-1),
      match_index(-1),
      start_id(-1),
      start_offset(0),
      end_id(-1),
      end_offset(-1),
      active_request_id(-1) {}

#if !defined(PLATFORM_HAS_NATIVE_ACCESSIBILITY_IMPL)
// static
BrowserAccessibilityManager* BrowserAccessibilityManager::Create(
    const ui::AXTreeUpdate& initial_tree,
    BrowserAccessibilityDelegate* delegate,
    BrowserAccessibilityFactory* factory) {
  return new BrowserAccessibilityManager(initial_tree, delegate, factory);
}
#endif

// static
BrowserAccessibilityManager* BrowserAccessibilityManager::FromID(
    AXTreeIDRegistry::AXTreeID ax_tree_id) {
  AXTreeIDMap* ax_tree_id_map = g_ax_tree_id_map.Pointer();
  auto iter = ax_tree_id_map->find(ax_tree_id);
  return iter == ax_tree_id_map->end() ? nullptr : iter->second;
}

BrowserAccessibilityManager::BrowserAccessibilityManager(
    BrowserAccessibilityDelegate* delegate,
    BrowserAccessibilityFactory* factory)
    : delegate_(delegate),
      factory_(factory),
      tree_(new ui::AXSerializableTree()),
      user_is_navigating_away_(false),
      osk_state_(OSK_ALLOWED),
      last_focused_node_(nullptr),
      last_focused_manager_(nullptr),
      connected_to_parent_tree_node_(false),
      ax_tree_id_(AXTreeIDRegistry::kNoAXTreeID),
      parent_node_id_from_parent_tree_(0) {
  tree_->SetDelegate(this);
}

BrowserAccessibilityManager::BrowserAccessibilityManager(
    const ui::AXTreeUpdate& initial_tree,
    BrowserAccessibilityDelegate* delegate,
    BrowserAccessibilityFactory* factory)
    : delegate_(delegate),
      factory_(factory),
      tree_(new ui::AXSerializableTree()),
      user_is_navigating_away_(false),
      osk_state_(OSK_ALLOWED),
      last_focused_node_(nullptr),
      last_focused_manager_(nullptr),
      ax_tree_id_(AXTreeIDRegistry::kNoAXTreeID),
      parent_node_id_from_parent_tree_(0) {
  tree_->SetDelegate(this);
  Initialize(initial_tree);
}

BrowserAccessibilityManager::~BrowserAccessibilityManager() {
  tree_.reset(NULL);
  g_ax_tree_id_map.Get().erase(ax_tree_id_);
}

void BrowserAccessibilityManager::Initialize(
    const ui::AXTreeUpdate& initial_tree) {
  if (!tree_->Unserialize(initial_tree)) {
    if (delegate_) {
      LOG(ERROR) << tree_->error();
      delegate_->AccessibilityFatalError();
    } else {
      LOG(FATAL) << tree_->error();
    }
  }
}

// static
ui::AXTreeUpdate
BrowserAccessibilityManager::GetEmptyDocument() {
  ui::AXNodeData empty_document;
  empty_document.id = 0;
  empty_document.role = ui::AX_ROLE_ROOT_WEB_AREA;
  ui::AXTreeUpdate update;
  update.nodes.push_back(empty_document);
  return update;
}

void BrowserAccessibilityManager::NotifyAccessibilityEvent(
    BrowserAccessibilityEvent::Source source,
    ui::AXEvent event_type,
    BrowserAccessibility* node) {
  BrowserAccessibilityEvent::Create(source, event_type, node)->Fire();
}

void BrowserAccessibilityManager::FireFocusEventsIfNeeded(
    BrowserAccessibilityEvent::Source source) {
  BrowserAccessibility* focus = GetFocus();

  // Don't fire focus events if the window itself doesn't have focus.
  // Bypass this check if a global focus listener was set up for testing
  // so that the test passes whether the window is active or not.
  if (g_focus_change_callback_for_testing.Get().is_null()) {
    if (delegate_ && !delegate_->AccessibilityViewHasFocus())
      focus = nullptr;

    if (!CanFireEvents())
      focus = nullptr;
  }

  // Don't allow the document to be focused if it has no children and
  // hasn't finished loading yet. Wait for at least a tiny bit of content,
  // or for the document to actually finish loading.
  if (focus &&
      focus == focus->manager()->GetRoot() &&
      focus->PlatformChildCount() == 0 &&
      !focus->HasState(ui::AX_STATE_BUSY) &&
      !focus->manager()->GetTreeData().loaded) {
    focus = nullptr;
  }

  if (focus && focus != last_focused_node_)
    FireFocusEvent(source, focus);

  last_focused_node_ = focus;
  last_focused_manager_ = focus ? focus->manager() : nullptr;
}

bool BrowserAccessibilityManager::CanFireEvents() {
  return true;
}

void BrowserAccessibilityManager::FireFocusEvent(
    BrowserAccessibilityEvent::Source source,
    BrowserAccessibility* node) {
  NotifyAccessibilityEvent(source, ui::AX_EVENT_FOCUS, node);

  if (!g_focus_change_callback_for_testing.Get().is_null())
    g_focus_change_callback_for_testing.Get().Run();
}

BrowserAccessibility* BrowserAccessibilityManager::GetRoot() {
  // tree_ can be null during destruction.
  if (!tree_)
    return nullptr;

  // tree_->root() can be null during AXTreeDelegate callbacks.
  ui::AXNode* root = tree_->root();
  return root ? GetFromAXNode(root) : nullptr;
}

BrowserAccessibility* BrowserAccessibilityManager::GetFromAXNode(
    const ui::AXNode* node) const {
  if (!node)
    return nullptr;
  return GetFromID(node->id());
}

BrowserAccessibility* BrowserAccessibilityManager::GetFromID(int32_t id) const {
  const auto iter = id_wrapper_map_.find(id);
  if (iter != id_wrapper_map_.end())
    return iter->second;

  return nullptr;
}

BrowserAccessibility*
BrowserAccessibilityManager::GetParentNodeFromParentTree() {
  if (!GetRoot())
    return nullptr;

  int parent_tree_id = GetTreeData().parent_tree_id;
  BrowserAccessibilityManager* parent_manager =
      BrowserAccessibilityManager::FromID(parent_tree_id);
  if (!parent_manager)
    return nullptr;

  // Try to use the cached parent node from the most recent time this
  // was called.
  if (parent_node_id_from_parent_tree_) {
    BrowserAccessibility* parent_node = parent_manager->GetFromID(
        parent_node_id_from_parent_tree_);
    if (parent_node) {
      int parent_child_tree_id =
          parent_node->GetIntAttribute(ui::AX_ATTR_CHILD_TREE_ID);
      if (parent_child_tree_id == ax_tree_id_)
        return parent_node;
    }
  }

  // If that fails, search for it and cache it for next time.
  BrowserAccessibility* parent_node = FindNodeWithChildTreeId(
      parent_manager->GetRoot(), ax_tree_id_);
  if (parent_node) {
    parent_node_id_from_parent_tree_ = parent_node->GetId();
    return parent_node;
  }

  return nullptr;
}

const ui::AXTreeData& BrowserAccessibilityManager::GetTreeData() {
  return tree_->data();
}

void BrowserAccessibilityManager::OnWindowFocused() {
  if (this == GetRootManager())
    FireFocusEventsIfNeeded(BrowserAccessibilityEvent::FromWindowFocusChange);
}

void BrowserAccessibilityManager::OnWindowBlurred() {
  if (this == GetRootManager()) {
    last_focused_node_ = nullptr;
    last_focused_manager_ = nullptr;
  }
}

void BrowserAccessibilityManager::UserIsNavigatingAway() {
  user_is_navigating_away_ = true;
}

void BrowserAccessibilityManager::UserIsReloading() {
  user_is_navigating_away_ = true;
}

void BrowserAccessibilityManager::NavigationSucceeded() {
  user_is_navigating_away_ = false;
}

void BrowserAccessibilityManager::NavigationFailed() {
  user_is_navigating_away_ = false;
}

bool BrowserAccessibilityManager::UseRootScrollOffsetsWhenComputingBounds() {
  return true;
}

void BrowserAccessibilityManager::OnAccessibilityEvents(
    const std::vector<AXEventNotificationDetails>& details) {
  // Process all changes to the accessibility tree first.
  for (uint32_t index = 0; index < details.size(); ++index) {
    const AXEventNotificationDetails& detail = details[index];
    if (!tree_->Unserialize(detail.update)) {
      if (delegate_) {
        LOG(ERROR) << tree_->error();
        delegate_->AccessibilityFatalError();
      } else {
        CHECK(false) << tree_->error();
      }
      return;
    }
  }

  // If the root's parent is in another accessibility tree but it wasn't
  // previously connected, post the proper notifications on the parent.
  BrowserAccessibility* parent = GetParentNodeFromParentTree();
  if (parent) {
    if (!connected_to_parent_tree_node_) {
      parent->OnDataChanged();
      parent->UpdatePlatformAttributes();
      NotifyAccessibilityEvent(
          BrowserAccessibilityEvent::FromChildFrameLoading,
          ui::AX_EVENT_CHILDREN_CHANGED,
          parent);
      connected_to_parent_tree_node_ = true;
    }
  } else {
    connected_to_parent_tree_node_ = false;
  }

  // Based on the changes to the tree, first fire focus events if needed.
  // Screen readers might not do the right thing if they're not aware of what
  // has focus, so always try that first. Nothing will be fired if the window
  // itself isn't focused or if focus hasn't changed.
  GetRootManager()->FireFocusEventsIfNeeded(
      BrowserAccessibilityEvent::FromBlink);

  // Now iterate over the events again and fire the events other than focus
  // events.
  for (uint32_t index = 0; index < details.size(); index++) {
    const AXEventNotificationDetails& detail = details[index];

    // Find the node corresponding to the id that's the target of the
    // event (which may not be the root of the update tree).
    ui::AXNode* node = tree_->GetFromId(detail.id);
    if (!node)
      continue;

    ui::AXEvent event_type = detail.event_type;
    if (event_type == ui::AX_EVENT_FOCUS ||
        event_type == ui::AX_EVENT_BLUR) {
      if (osk_state_ != OSK_DISALLOWED_BECAUSE_TAB_HIDDEN &&
          osk_state_ != OSK_DISALLOWED_BECAUSE_TAB_JUST_APPEARED) {
        osk_state_ = OSK_ALLOWED;
      }

      // We already handled all focus events above.
      continue;
    }

    // Fire the native event.
    BrowserAccessibility* event_target = GetFromAXNode(node);
    if (event_target) {
      NotifyAccessibilityEvent(
          BrowserAccessibilityEvent::FromBlink,
          event_type,
          event_target);
    }
  }
}

void BrowserAccessibilityManager::OnLocationChanges(
    const std::vector<AccessibilityHostMsg_LocationChangeParams>& params) {
  for (size_t i = 0; i < params.size(); ++i) {
    BrowserAccessibility* obj = GetFromID(params[i].id);
    if (!obj)
      continue;
    ui::AXNode* node = obj->node();
    node->SetLocation(params[i].new_location);
  }
  SendLocationChangeEvents(params);
}

void BrowserAccessibilityManager::SendLocationChangeEvents(
    const std::vector<AccessibilityHostMsg_LocationChangeParams>& params) {
  for (size_t i = 0; i < params.size(); ++i) {
    BrowserAccessibility* obj = GetFromID(params[i].id);
    if (obj)
      obj->OnLocationChanged();
  }
}

void BrowserAccessibilityManager::OnFindInPageResult(
    int request_id, int match_index, int start_id, int start_offset,
    int end_id, int end_offset) {
  find_in_page_info_.request_id = request_id;
  find_in_page_info_.match_index = match_index;
  find_in_page_info_.start_id = start_id;
  find_in_page_info_.start_offset = start_offset;
  find_in_page_info_.end_id = end_id;
  find_in_page_info_.end_offset = end_offset;

  if (find_in_page_info_.active_request_id == request_id)
    ActivateFindInPageResult(request_id);
}

void BrowserAccessibilityManager::OnChildFrameHitTestResult(
    const gfx::Point& point,
    int hit_obj_id) {
  BrowserAccessibility* obj = GetFromID(hit_obj_id);
  if (!obj || !obj->HasIntAttribute(ui::AX_ATTR_CHILD_TREE_ID))
    return;

  BrowserAccessibilityManager* child_manager =
      BrowserAccessibilityManager::FromID(
          obj->GetIntAttribute(ui::AX_ATTR_CHILD_TREE_ID));
  if (!child_manager || !child_manager->delegate())
    return;

  return child_manager->delegate()->AccessibilityHitTest(point);
}

void BrowserAccessibilityManager::ActivateFindInPageResult(
    int request_id) {
  find_in_page_info_.active_request_id = request_id;
  if (find_in_page_info_.request_id != request_id)
    return;

  BrowserAccessibility* node = GetFromID(find_in_page_info_.start_id);
  if (!node)
    return;

  // If an ancestor of this node is a leaf node, fire the notification on that.
  BrowserAccessibility* ancestor = node->GetParent();
  while (ancestor && ancestor != GetRoot()) {
    if (ancestor->PlatformIsLeaf())
      node = ancestor;
    ancestor = ancestor->GetParent();
  }

  // The "scrolled to anchor" notification is a great way to get a
  // screen reader to jump directly to a specific location in a document.
  NotifyAccessibilityEvent(
      BrowserAccessibilityEvent::FromFindInPageResult,
      ui::AX_EVENT_SCROLLED_TO_ANCHOR,
      node);
}

BrowserAccessibility* BrowserAccessibilityManager::GetActiveDescendant(
    BrowserAccessibility* focus) {
  if (!focus)
    return nullptr;

  int32_t active_descendant_id;
  BrowserAccessibility* active_descendant = nullptr;
  if (focus->GetIntAttribute(ui::AX_ATTR_ACTIVEDESCENDANT_ID,
                             &active_descendant_id)) {
    active_descendant = focus->manager()->GetFromID(active_descendant_id);
  }

  if (focus->GetRole() == ui::AX_ROLE_POP_UP_BUTTON) {
    BrowserAccessibility* child = focus->InternalGetChild(0);
    if (child && child->GetRole() == ui::AX_ROLE_MENU_LIST_POPUP) {
      // The active descendant is found on the menu list popup, i.e. on the
      // actual list and not on the button that opens it.
      // If there is no active descendant, focus should stay on the button so
      // that Windows screen readers would enable their virtual cursor.
      if (child->GetIntAttribute(ui::AX_ATTR_ACTIVEDESCENDANT_ID,
                                 &active_descendant_id)) {
        active_descendant = child->manager()->GetFromID(active_descendant_id);
      }
    }
  }

  if (active_descendant)
    return active_descendant;

  return focus;
}

bool BrowserAccessibilityManager::NativeViewHasFocus() {
  BrowserAccessibilityDelegate* delegate = GetDelegateFromRootManager();
  if (delegate)
    return delegate->AccessibilityViewHasFocus();
  return false;
}

BrowserAccessibility* BrowserAccessibilityManager::GetFocus() {
  BrowserAccessibilityManager* root_manager = GetRootManager();
  if (!root_manager)
    root_manager = this;
  int32_t focused_tree_id = root_manager->GetTreeData().focused_tree_id;

  BrowserAccessibilityManager* focused_manager = nullptr;
  if (focused_tree_id)
    focused_manager =BrowserAccessibilityManager::FromID(focused_tree_id);

  // BrowserAccessibilityManager::FromID(focused_tree_id) may return nullptr
  // if the tree is not created or has been destroyed.
  if (!focused_manager)
    focused_manager = root_manager;

  return focused_manager->GetFocusFromThisOrDescendantFrame();
}

BrowserAccessibility*
BrowserAccessibilityManager::GetFocusFromThisOrDescendantFrame() {
  int32_t focus_id = GetTreeData().focus_id;
  BrowserAccessibility* obj = GetFromID(focus_id);
  if (!obj)
    return GetRoot();

  if (obj->HasIntAttribute(ui::AX_ATTR_CHILD_TREE_ID)) {
    BrowserAccessibilityManager* child_manager =
        BrowserAccessibilityManager::FromID(
            obj->GetIntAttribute(ui::AX_ATTR_CHILD_TREE_ID));
    if (child_manager)
      return child_manager->GetFocusFromThisOrDescendantFrame();
  }

  return obj;
}

void BrowserAccessibilityManager::SetFocus(const BrowserAccessibility& node) {
  if (delegate_)
    delegate_->AccessibilitySetFocus(node.GetId());
}

void BrowserAccessibilityManager::SetFocusLocallyForTesting(
    BrowserAccessibility* node) {
  ui::AXTreeData data = GetTreeData();
  data.focus_id = node->GetId();
  tree_->UpdateData(data);
}

// static
void BrowserAccessibilityManager::SetFocusChangeCallbackForTesting(
    const base::Closure& callback) {
  g_focus_change_callback_for_testing.Get() = callback;
}

void BrowserAccessibilityManager::DoDefaultAction(
    const BrowserAccessibility& node) {
  if (delegate_)
    delegate_->AccessibilityDoDefaultAction(node.GetId());
}

void BrowserAccessibilityManager::ScrollToMakeVisible(
    const BrowserAccessibility& node, gfx::Rect subfocus) {
  if (delegate_) {
    delegate_->AccessibilityScrollToMakeVisible(node.GetId(), subfocus);
  }
}

void BrowserAccessibilityManager::ScrollToPoint(
    const BrowserAccessibility& node, gfx::Point point) {
  if (delegate_) {
    delegate_->AccessibilityScrollToPoint(node.GetId(), point);
  }
}

void BrowserAccessibilityManager::SetScrollOffset(
    const BrowserAccessibility& node, gfx::Point offset) {
  if (delegate_) {
    delegate_->AccessibilitySetScrollOffset(node.GetId(), offset);
  }
}

void BrowserAccessibilityManager::SetValue(
    const BrowserAccessibility& node,
    const base::string16& value) {
  if (delegate_)
    delegate_->AccessibilitySetValue(node.GetId(), value);
}

void BrowserAccessibilityManager::SetTextSelection(
    const BrowserAccessibility& node,
    int start_offset,
    int end_offset) {
  if (delegate_) {
    delegate_->AccessibilitySetSelection(node.GetId(), start_offset,
                                         node.GetId(), end_offset);
  }
}

gfx::Rect BrowserAccessibilityManager::GetViewBounds() {
  BrowserAccessibilityDelegate* delegate = GetDelegateFromRootManager();
  if (delegate)
    return delegate->AccessibilityGetViewBounds();
  return gfx::Rect();
}

// static
BrowserAccessibility* BrowserAccessibilityManager::NextInTreeOrder(
    const BrowserAccessibility* object) {
  if (!object)
    return nullptr;

  if (object->PlatformChildCount())
    return object->PlatformGetChild(0);

  while (object) {
    BrowserAccessibility* sibling = object->GetNextSibling();
    if (sibling)
      return sibling;

    object = object->GetParent();
  }

  return nullptr;
}

// static
BrowserAccessibility* BrowserAccessibilityManager::PreviousInTreeOrder(
    const BrowserAccessibility* object) {
  if (!object)
    return nullptr;

  BrowserAccessibility* sibling = object->GetPreviousSibling();
  if (!sibling)
    return object->GetParent();

  if (sibling->PlatformChildCount())
    return sibling->PlatformDeepestLastChild();

  return sibling;
}

// static
BrowserAccessibility* BrowserAccessibilityManager::PreviousTextOnlyObject(
    const BrowserAccessibility* object) {
  BrowserAccessibility* previous_object = PreviousInTreeOrder(object);
  while (previous_object && !previous_object->IsTextOnlyObject())
    previous_object = PreviousInTreeOrder(previous_object);

  return previous_object;
}

// static
BrowserAccessibility* BrowserAccessibilityManager::NextTextOnlyObject(
    const BrowserAccessibility* object) {
  BrowserAccessibility* next_object = NextInTreeOrder(object);
  while (next_object && !next_object->IsTextOnlyObject())
    next_object = NextInTreeOrder(next_object);

  return next_object;
}

// static
bool BrowserAccessibilityManager::FindIndicesInCommonParent(
    const BrowserAccessibility& object1,
    const BrowserAccessibility& object2,
    BrowserAccessibility** common_parent,
    int* child_index1,
    int* child_index2) {
  DCHECK(common_parent && child_index1 && child_index2);
  auto ancestor1 = const_cast<BrowserAccessibility*>(&object1);
  auto ancestor2 = const_cast<BrowserAccessibility*>(&object2);
  do {
    *child_index1 = ancestor1->GetIndexInParent();
    ancestor1 = ancestor1->GetParent();
  } while (
      ancestor1 &&
      // |BrowserAccessibility::IsAncestorOf| returns true if objects are equal.
      (ancestor1 == ancestor2 || !ancestor2->IsDescendantOf(ancestor1)));

  if (!ancestor1) {
    *common_parent = nullptr;
    *child_index1 = -1;
    *child_index2 = -1;
    return false;
  }

  do {
    *child_index2 = ancestor2->GetIndexInParent();
    ancestor2 = ancestor2->GetParent();
  } while (ancestor1 != ancestor2);

  *common_parent = ancestor1;
  return true;
}

// static
base::string16 BrowserAccessibilityManager::GetTextForRange(
    const BrowserAccessibility& start_object,
    int start_offset,
    const BrowserAccessibility& end_object,
    int end_offset) {
  DCHECK_GE(start_offset, 0);
  DCHECK_GE(end_offset, 0);

  if (&start_object == &end_object && start_object.IsSimpleTextControl()) {
    if (start_offset > end_offset)
      std::swap(start_offset, end_offset);

    if (start_offset >= static_cast<int>(start_object.GetValue().length()) ||
        end_offset > static_cast<int>(start_object.GetValue().length())) {
      return base::string16();
    }

    return start_object.GetValue().substr(start_offset,
                                          end_offset - start_offset);
  }

  int child_index1 = -1;
  int child_index2 = -1;
  if (&start_object != &end_object) {
    BrowserAccessibility* common_parent;
    if (!FindIndicesInCommonParent(start_object, end_object, &common_parent,
                                   &child_index1, &child_index2)) {
      return base::string16();
    }

    DCHECK(common_parent);
    DCHECK_GE(child_index1, 0);
    DCHECK_GE(child_index2, 0);
    // If the child indices are equal, one object is a descendant of the other.
    DCHECK(child_index1 != child_index2 ||
           start_object.IsDescendantOf(&end_object) ||
           end_object.IsDescendantOf(&start_object));
  }

  const BrowserAccessibility* start_text_object = nullptr;
  const BrowserAccessibility* end_text_object = nullptr;
  if (child_index1 <= child_index2 ||
      end_object.IsDescendantOf(&start_object)) {
    start_text_object = &start_object;
    end_text_object = &end_object;
  } else if (child_index1 > child_index2 ||
             start_object.IsDescendantOf(&end_object)) {
    start_text_object = &end_object;
    end_text_object = &start_object;
  }

  if (!start_text_object->PlatformIsLeaf())
    start_text_object = start_text_object->PlatformDeepestFirstChild();
  if (!end_text_object->PlatformIsLeaf())
    end_text_object = end_text_object->PlatformDeepestLastChild();

  if (!start_text_object->IsTextOnlyObject())
    start_text_object = NextTextOnlyObject(start_text_object);
  if (!end_text_object->IsTextOnlyObject())
    end_text_object = PreviousTextOnlyObject(end_text_object);

  if (!start_text_object || !end_text_object)
    return base::string16();

  // Be a little permissive with the start and end offsets.
  if (start_text_object == end_text_object) {
    if (start_offset > end_offset)
      std::swap(start_offset, end_offset);

    if (start_offset <
            static_cast<int>(start_text_object->GetText().length()) &&
        end_offset <= static_cast<int>(end_text_object->GetText().length())) {
      return start_text_object->GetText().substr(start_offset,
                                                 end_offset - start_offset);
    }
    return start_text_object->GetText();
  }

  base::string16 text;
  if (start_offset < static_cast<int>(start_text_object->GetText().length()))
    text += start_text_object->GetText().substr(start_offset);
  else
    text += start_text_object->GetText();
  start_text_object = NextTextOnlyObject(start_text_object);
  while (start_text_object && start_text_object != end_text_object) {
    text += start_text_object->GetText();
    start_text_object = NextTextOnlyObject(start_text_object);
  }
  if (end_offset <= static_cast<int>(end_text_object->GetText().length()))
    text += end_text_object->GetText().substr(0, end_offset);
  else
    text += end_text_object->GetText();

  return text;
}

void BrowserAccessibilityManager::OnNodeDataWillChange(
    ui::AXTree* tree,
    const ui::AXNodeData& old_node_data,
    const ui::AXNodeData& new_node_data) {}

void BrowserAccessibilityManager::OnTreeDataChanged(ui::AXTree* tree) {
}

void BrowserAccessibilityManager::OnNodeWillBeDeleted(ui::AXTree* tree,
                                                      ui::AXNode* node) {
  DCHECK(node);
  if (id_wrapper_map_.find(node->id()) == id_wrapper_map_.end())
    return;
  GetFromAXNode(node)->Destroy();
  id_wrapper_map_.erase(node->id());
}

void BrowserAccessibilityManager::OnSubtreeWillBeDeleted(ui::AXTree* tree,
                                                         ui::AXNode* node) {
  DCHECK(node);
  BrowserAccessibility* obj = GetFromAXNode(node);
  if (obj)
    obj->OnSubtreeWillBeDeleted();
}

void BrowserAccessibilityManager::OnNodeCreated(ui::AXTree* tree,
                                                ui::AXNode* node) {
  BrowserAccessibility* wrapper = factory_->Create();
  wrapper->Init(this, node);
  id_wrapper_map_[node->id()] = wrapper;
  wrapper->OnDataChanged();
}

void BrowserAccessibilityManager::OnNodeChanged(ui::AXTree* tree,
                                                ui::AXNode* node) {
  DCHECK(node);
  GetFromAXNode(node)->OnDataChanged();
}

void BrowserAccessibilityManager::OnAtomicUpdateFinished(
    ui::AXTree* tree,
    bool root_changed,
    const std::vector<ui::AXTreeDelegate::Change>& changes) {
  bool ax_tree_id_changed = false;
  if (GetTreeData().tree_id != -1 && GetTreeData().tree_id != ax_tree_id_) {
    g_ax_tree_id_map.Get().erase(ax_tree_id_);
    ax_tree_id_ = GetTreeData().tree_id;
    g_ax_tree_id_map.Get().insert(std::make_pair(ax_tree_id_, this));
    ax_tree_id_changed = true;
  }

  // Whenever the tree ID or the root of this tree changes we may need to
  // fire an event on our parent node in the parent tree to ensure that
  // we're properly connected.
  if (ax_tree_id_changed || root_changed)
    connected_to_parent_tree_node_ = false;

  // When the root changes and this is the root manager, we may need to
  // fire a new focus event.
  if (root_changed && last_focused_manager_ == this) {
    last_focused_node_ = nullptr;
    last_focused_manager_ = nullptr;
  }
}

BrowserAccessibilityManager* BrowserAccessibilityManager::GetRootManager() {
  BrowserAccessibility* parent = GetParentNodeFromParentTree();
  if (!parent)
    return this;

  return parent->manager()->GetRootManager();
}

BrowserAccessibilityDelegate*
    BrowserAccessibilityManager::GetDelegateFromRootManager() {
  BrowserAccessibilityManager* root_manager = GetRootManager();
  if (root_manager)
    return root_manager->delegate();
  return nullptr;
}

ui::AXTreeUpdate
BrowserAccessibilityManager::SnapshotAXTreeForTesting() {
  std::unique_ptr<
      ui::AXTreeSource<const ui::AXNode*, ui::AXNodeData, ui::AXTreeData>>
      tree_source(tree_->CreateTreeSource());
  ui::AXTreeSerializer<const ui::AXNode*,
                       ui::AXNodeData,
                       ui::AXTreeData> serializer(tree_source.get());
  ui::AXTreeUpdate update;
  serializer.SerializeChanges(tree_->root(), &update);
  return update;
}

}  // namespace content