| // 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_ |