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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_REVERSE_SPIRAL_ITERATOR_H_
#define CC_BASE_REVERSE_SPIRAL_ITERATOR_H_
#include "cc/base/base_export.h"
#include "cc/base/index_rect.h"
namespace cc {
// The spiral iterator which iterates in reverse direction based on directions
// around the center rect in the given region. If the center rect is at index
// (2, 2), reverse spiral iterator gives following sequence on iterating.
//
// x 0 1 2 3 4
// y ┌───┬───┬───┬───┬───┐
// 0 │ 9│ 10│ 11│ 12│ 13│
// ├───┼───┼───┼───┼───┤
// 1 │ 8│ 21│ 22│ 23│ 14│
// ├───┼───┼───┼───┼───┤
// 2 │ 7│ 20│ *│ 24│ 15│
// ├───┼───┼───┼───┼───┤
// 3 │ 6│ 19│ 18│ 17│ 16│
// ├───┼───┼───┼───┼───┤
// 4 │ 5│ 4│ 3│ 2│ 1│
// └───┴───┴───┴───┴───┘
class CC_BASE_EXPORT ReverseSpiralIterator {
public:
ReverseSpiralIterator();
ReverseSpiralIterator(const IndexRect& around_index_rect,
const IndexRect& consider_index_rect,
const IndexRect& ignore_index_rect);
~ReverseSpiralIterator() = default;
ReverseSpiralIterator& operator=(ReverseSpiralIterator&& other) = default;
operator bool() const;
ReverseSpiralIterator& 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 { LEFT, UP, RIGHT, DOWN };
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_REVERSE_SPIRAL_ITERATOR_H_