chromium/cc/base/spiral_iterator.h

// Copyright 2016 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_BASE_SPIRAL_ITERATOR_H_
#define CC_BASE_SPIRAL_ITERATOR_H_

#include "cc/base/base_export.h"
#include "cc/base/index_rect.h"

namespace cc {

// The spiral iterator which iterates based on directions around the center
// rect in the given region. If the center rect is at index (2, 2), spiral
// iterator gives following sequence on iterating.
//
//    x 0   1   2   3   4
//  y ┌───┬───┬───┬───┬───┐
//  0 │ 16│ 15│ 14│ 13│ 12│
//    ├───┼───┼───┼───┼───┤
//  1 │ 17│  4│  3│  2│ 11│
//    ├───┼───┼───┼───┼───┤
//  2 │ 18│  5│  *│  1│ 10│
//    ├───┼───┼───┼───┼───┤
//  3 │ 19│  6│  7│  8│  9│
//    ├───┼───┼───┼───┼───┤
//  4 │ 20│ 21│ 22│ 23│ 24│
//    └───┴───┴───┴───┴───┘
class CC_BASE_EXPORT SpiralIterator { … };

}  // namespace cc

#endif  // CC_BASE_SPIRAL_ITERATOR_H_