It is time.

ui/accessibility/ax_tree.h

-// Copyright 2013 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.
-
-#ifndef UI_ACCESSIBILITY_AX_TREE_H_
-#define UI_ACCESSIBILITY_AX_TREE_H_
-
-#include <set>
-
-#include "base/containers/hash_tables.h"
-#include "ui/accessibility/ax_export.h"
-#include "ui/accessibility/ax_tree_update.h"
-
-namespace ui {
-
-class AXNode;
-struct AXTreeUpdateState;
-
-// Used when you want to be notified when changes happen to the tree.
-//
-// Some of the notifications are called in the middle of an update operation.
-// Be careful, as the tree may be in an inconsistent state at this time;
-// don't walk the parents and children at this time:
-//   OnNodeWillBeDeleted
-//   OnNodeCreated
-//   OnNodeChanged
-//
-// Other notifications are called at the end of an atomic update operation.
-// From these, it's safe to walk the tree and do any initialization that
-// assumes the tree is in a consistent state.
-//   OnNodeCreationFinished
-//   OnNodeChangeFinished
-//   OnRootChanged
-class AX_EXPORT AXTreeDelegate {
- public:
-  AXTreeDelegate();
-  virtual ~AXTreeDelegate();
-
-  // Called just before a node is deleted. Its id and data will be valid,
-  // but its links to parents and children are invalid. This is called
-  // in the middle of an update, the tree may be in an invalid state!
-  virtual void OnNodeWillBeDeleted(AXNode* node) = 0;
-
-  // Called immediately after a new node is created. The tree may be in
-  // the middle of an update, don't walk the parents and children now.
-  virtual void OnNodeCreated(AXNode* node) = 0;
-
-  // Called when a node changes its data or children. The tree may be in
-  // the middle of an update, don't walk the parents and children now.
-  virtual void OnNodeChanged(AXNode* node) = 0;
-
-  // Called for each new node at the end of an update operation,
-  // when the tree is in a consistent state.
-  virtual void OnNodeCreationFinished(AXNode* node) = 0;
-
-  // Called for each existing node that changed at the end of an update
-  // operation, when the tree is in a consistent state.
-  virtual void OnNodeChangeFinished(AXNode* node) = 0;
-
-  // Called at the end of an update operation when the root node changes.
-  virtual void OnRootChanged(AXNode* new_root) = 0;
-};
-
-// AXTree is a live, managed tree of AXNode objects that can receive
-// updates from another AXTreeSource via AXTreeUpdates, and it can be
-// used as a source for sending updates to another client tree.
-// It's designed to be subclassed to implement support for native
-// accessibility APIs on a specific platform.
-class AX_EXPORT AXTree {
- public:
-  AXTree();
-  explicit AXTree(const AXTreeUpdate& initial_state);
-  virtual ~AXTree();
-
-  virtual void SetDelegate(AXTreeDelegate* delegate);
-
-  virtual AXNode* GetRoot() const;
-  virtual AXNode* GetFromId(int32 id) const;
-
-  // Returns true on success. If it returns false, it's a fatal error
-  // and this tree should be destroyed, and the source of the tree update
-  // should not be trusted any longer.
-  virtual bool Unserialize(const AXTreeUpdate& update);
-
-  // Return a multi-line indented string representation, for logging.
-  std::string ToString() const;
-
-  // A string describing the error from an unsuccessful Unserialize,
-  // for testing and debugging.
-  const std::string& error() { return error_; }
-
- private:
-  AXNode* CreateNode(AXNode* parent, int32 id, int32 index_in_parent);
-
-  // This is called from within Unserialize(), it returns true on success.
-  bool UpdateNode(const AXNodeData& src, AXTreeUpdateState* update_state);
-
-  void OnRootChanged();
-
-  // Call Destroy() on |node|, and delete it from the id map, and then
-  // call recursively on all nodes in its subtree.
-  void DestroyNodeAndSubtree(AXNode* node);
-
-  // Iterate over the children of |node| and for each child, destroy the
-  // child and its subtree if its id is not in |new_child_ids|. Returns
-  // true on success, false on fatal error.
-  bool DeleteOldChildren(AXNode* node,
-                         const std::vector<int32> new_child_ids);
-
-  // Iterate over |new_child_ids| and populate |new_children| with
-  // pointers to child nodes, reusing existing nodes already in the tree
-  // if they exist, and creating otherwise. Reparenting is disallowed, so
-  // if the id already exists as the child of another node, that's an
-  // error. Returns true on success, false on fatal error.
-  bool CreateNewChildVector(AXNode* node,
-                            const std::vector<int32> new_child_ids,
-                            std::vector<AXNode*>* new_children,
-                            AXTreeUpdateState* update_state);
-
-  AXTreeDelegate* delegate_;
-  AXNode* root_;
-  base::hash_map<int32, AXNode*> id_map_;
-  std::string error_;
-};
-
-}  // namespace ui
-
-#endif  // UI_ACCESSIBILITY_AX_TREE_H_