a11y: Move CreateTextMarker[Range] to TextMarkerHelperMac.

ui/accessibility/ax_abstract_position.h

+// Copyright 2017 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_ABSTRACT_POSITION_H_
+#define UI_ACCESSIBILITY_AX_ABSTRACT_POSITION_H_
+
+#include <memory>
+#include <utility>
+
+#include "base/macros.h"
+#include "ui/accessibility/ax_enums.h"
+#include "ui/accessibility/ax_export.h"
+
+namespace ui {
+
+class AXAbstractPosition;
+
+// Defines the type of position in the accessibility tree.
+// A tree position is used when referring to a specific child of a node in the
+// accessibility tree.
+// A text position is used when referring to a specific character of text inside
+// a particular node.
+// A null position is used to signify that the provided data is invalid or that
+// a boundary has been reached.
+enum class AXPositionKind { NULL_POSITION, TREE_POSITION, TEXT_POSITION };
+
+// Plain old data to serialize and deserialize a position. See AXPosition.
+struct AX_EXPORT AXPositionData {
+  AXPositionKind kind;
+  int tree_id;
+  int32_t anchor_id;
+  int child_index;
+  int text_offset;
+  AXTextAffinity affinity;
+};
+
+// An immutable move-only type that wraps a polymorphic AXAbstractPosition.
+class AX_EXPORT AXPositionPointer {
+ public:
+  // Allow moving. Declaring this implicitly deletes other constructors.
+  AXPositionPointer(AXPositionPointer&& other);
+
+  // Allow implicit upcasting when using std::move on a std::unique_ptr.
+  template <class Concrete>
+  AXPositionPointer(std::unique_ptr<Concrete> other) : ptr_(other.release()) {}
+
+  // Allow implicit conversion from nullptr.
+  AXPositionPointer(std::nullptr_t);
+
+  ~AXPositionPointer();
+
+  explicit operator bool() const { return ptr_.get() != nullptr; }
+  const AXAbstractPosition* operator->() const { return ptr_.get(); }
+
+  // Downcasting must be explicit.
+  template <class Concrete>
+  const Concrete* DownCastTo() const {
+    return static_cast<Concrete*>(ptr_.get());
+  }
+
+ private:
+  std::unique_ptr<AXAbstractPosition> ptr_;
+
+  DISALLOW_COPY_AND_ASSIGN(AXPositionPointer);
+};
+
+using AXRangePointer = std::pair<AXPositionPointer, AXPositionPointer>;
+
+// Represents a tree or text position. An AXAbstractPosition exposes the methods
+// required to manipulate the position, without having to know details of how to
+// represent it.
+class AX_EXPORT AXAbstractPosition {
+ public:
+  static constexpr int INVALID_TREE_ID = -1;
+  static constexpr int32_t INVALID_ANCHOR_ID = -1;
+  static constexpr int BEFORE_TEXT = -1;
+  static constexpr int INVALID_INDEX = -2;
+  static constexpr int INVALID_OFFSET = -1;
+
+  // TODO(tapted): Make this constexpr. It can't be currently because it tickles
+  // a bogus warning due to an MSVC compiler bug -- https://goo.gl/TGW4Ji . The
+  // warning can be suppressed, but this is usually passed by reference anyway.
+  static const AXPositionData kNullData;
+
+  virtual ~AXAbstractPosition() {}
+
+  virtual void ToData(AXPositionData* data) const = 0;
+  virtual bool IsNull() const = 0;
+
+  // Compare according to the "Compare" C++ standard concept (this < other).
+  virtual bool Compare(const AXPositionPointer& other) const = 0;
+
+  virtual AXPositionPointer PositionAtEndOfAnchor() const = 0;
+  virtual AXPositionPointer PositionAtStartOfAnchor() const = 0;
+
+  virtual AXPositionPointer NextCharacterPosition() const = 0;
+  virtual AXPositionPointer PreviousCharacterPosition() const = 0;
+
+  virtual AXPositionPointer NextWordStartPosition() const = 0;
+  virtual AXPositionPointer PreviousWordStartPosition() const = 0;
+  virtual AXPositionPointer NextWordEndPosition() const = 0;
+  virtual AXPositionPointer PreviousWordEndPosition() const = 0;
+
+  virtual AXPositionPointer NextLineStartPosition() const = 0;
+  virtual AXPositionPointer PreviousLineStartPosition() const = 0;
+  virtual AXPositionPointer NextLineEndPosition() const = 0;
+  virtual AXPositionPointer PreviousLineEndPosition() const = 0;
+
+ protected:
+  AXAbstractPosition() {}
+};
+
+}  // namespace ui
+
+#endif  // UI_ACCESSIBILITY_AX_ABSTRACT_POSITION_H_