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// Copyright 2016 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 CC_BASE_SPIRAL_ITERATOR_H_
#define CC_BASE_SPIRAL_ITERATOR_H_
#include "base/logging.h"
#include "cc/base/cc_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_EXPORT SpiralIterator {
public:
SpiralIterator();
SpiralIterator(const IndexRect& around_index_rect,
const IndexRect& consider_index_rect,
const IndexRect& ignore_index_rect);
~SpiralIterator() = default;
operator bool() const;
SpiralIterator& operator++();
int index_x() const { return index_x_; }
int index_y() const { return index_y_; }
private:
int current_step_count() const {
return (direction_ == UP || direction_ == DOWN) ? vertical_step_count_
: horizontal_step_count_;
}
bool needs_direction_switch() const;
void switch_direction();
enum Direction { UP, LEFT, DOWN, RIGHT };
IndexRect around_index_rect_;
IndexRect consider_index_rect_;
IndexRect ignore_index_rect_;
int index_x_;
int index_y_;
Direction direction_;
int delta_x_;
int delta_y_;
int current_step_;
int horizontal_step_count_;
int vertical_step_count_;
};
} // namespace cc
#endif // CC_BASE_SPIRAL_ITERATOR_H_
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