| // 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 "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 { |
| 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_ |