ax_tree_id.h

// Copyright 2018 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_ID_H_
#define UI_ACCESSIBILITY_AX_TREE_ID_H_

#include <string>

#include "base/unguessable_token.h"
#include "ui/accessibility/ax_enums.mojom-shared.h"
#include "ui/accessibility/ax_export.h"

namespace mojo {
template <typename DataViewType, typename T>
struct UnionTraits;
}

namespace ax {
namespace mojom {
class AXTreeIDDataView;
}
}  // namespace ax

namespace ui {

// A unique ID representing an accessibility tree.
class AX_EXPORT AXTreeID {
 public:
  // Create an Unknown AXTreeID.
  AXTreeID();

  // Copy constructor.
  AXTreeID(const AXTreeID& other);

  // Create a new unique AXTreeID.
  static AXTreeID CreateNewAXTreeID();

  // Unserialize an AXTreeID from a string. This is used so that tree IDs
  // can be stored compactly as a string attribute in an AXNodeData, and
  // so that AXTreeIDs can be passed to JavaScript bindings in the
  // automation API.
  static AXTreeID FromString(const std::string& string);

  std::string ToString() const;

  ax::mojom::AXTreeIDType type() const { return type_; }
  const base::Optional<base::UnguessableToken>& token() const { return token_; }

  bool operator==(const AXTreeID& rhs) const;
  bool operator!=(const AXTreeID& rhs) const;
  bool operator<(const AXTreeID& rhs) const;
  bool operator<=(const AXTreeID& rhs) const;
  bool operator>(const AXTreeID& rhs) const;
  bool operator>=(const AXTreeID& rhs) const;

 private:
  explicit AXTreeID(ax::mojom::AXTreeIDType type);
  explicit AXTreeID(const std::string& string);

  friend struct mojo::UnionTraits<ax::mojom::AXTreeIDDataView, ui::AXTreeID>;
  friend class base::NoDestructor<AXTreeID>;

  ax::mojom::AXTreeIDType type_ = ax::mojom::AXTreeIDType::kUnknown;
  base::Optional<base::UnguessableToken> token_;
};

// For use in std::unordered_map.
struct AXTreeIDHash {
  size_t operator()(const ui::AXTreeID& tree_id) const {
    DCHECK(tree_id.type() == ax::mojom::AXTreeIDType::kToken);
    return base::UnguessableTokenHash()(tree_id.token().value());
  }
};

AX_EXPORT std::ostream& operator<<(std::ostream& stream, const AXTreeID& value);

// The value to use when an AXTreeID is unknown.
AX_EXPORT extern const AXTreeID& AXTreeIDUnknown();

}  // namespace ui

#endif  // UI_ACCESSIBILITY_AX_TREE_ID_H_