services/ui/ws/cursor_location_manager.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 SERVICES_UI_WS_CURSOR_LOCATION_MANAGER_H_
#define SERVICES_UI_WS_CURSOR_LOCATION_MANAGER_H_

#include "base/atomicops.h"
#include "base/macros.h"
#include "mojo/public/cpp/system/buffer.h"

namespace gfx {
class Point;
}

namespace ui {
namespace ws {

// Manages a shared memory buffer that stores the cursor location.
class CursorLocationManager {
 public:
  CursorLocationManager();
  ~CursorLocationManager();

  // Sets the current cursor location to |point|. Atomically writes the location
  // to shared memory.
  void OnMouseCursorLocationChanged(const gfx::Point& point);

  // Returns a read-only handle to the shared memory which contains the global
  // mouse cursor position. Each call returns a new handle.
  mojo::ScopedSharedBufferHandle GetCursorLocationMemory();

 private:
  base::subtle::Atomic32* cursor_location_memory() {
    return reinterpret_cast<base::subtle::Atomic32*>(
        cursor_location_mapping_.get());
  }

  // The current location of the cursor. This is always kept up to date so we
  // can atomically write this to |cursor_location_memory()| once it is created.
  base::subtle::Atomic32 current_cursor_location_ = 0;

  // A handle to a shared memory buffer that is one 32 bit integer long. We
  // share this with any client as the same user. This buffer is lazily
  // created on the first access.
  mojo::ScopedSharedBufferHandle cursor_location_handle_;

  // The one int32 in |cursor_location_handle_|. When we write to this
  // location, we must always write to it atomically. (On the other side of the
  // mojo connection, this data must be read atomically.)
  mojo::ScopedSharedBufferMapping cursor_location_mapping_;

  DISALLOW_COPY_AND_ASSIGN(CursorLocationManager);
};

}  // namespace ws
}  // namespace ui

#endif  // SERVICES_UI_WS_CURSOR_LOCATION_MANAGER_H_