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| 1 // Copyright 2016 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef CC_BASE_SPIRAL_ITERATOR_H_ |
| 6 #define CC_BASE_SPIRAL_ITERATOR_H_ |
| 7 |
| 8 #include "base/logging.h" |
| 9 #include "cc/base/cc_export.h" |
| 10 #include "cc/base/index_rect.h" |
| 11 |
| 12 namespace cc { |
| 13 |
| 14 // The spiral iterator which iterates based on directions around the center |
| 15 // rect in the given region. If the center rect is at index (2, 2), spiral |
| 16 // iterator gives following sequence on iterating. |
| 17 // |
| 18 // x 0 1 2 3 4 |
| 19 // y ┌───┬───┬───┬───┬───┐ |
| 20 // 0 │ 16│ 15│ 14│ 13│ 12│ |
| 21 // ├───┼───┼───┼───┼───┤ |
| 22 // 1 │ 17│ 4│ 3│ 2│ 11│ |
| 23 // ├───┼───┼───┼───┼───┤ |
| 24 // 2 │ 18│ 5│ *│ 1│ 10│ |
| 25 // ├───┼───┼───┼───┼───┤ |
| 26 // 3 │ 19│ 6│ 7│ 8│ 9│ |
| 27 // ├───┼───┼───┼───┼───┤ |
| 28 // 4 │ 20│ 21│ 22│ 23│ 24│ |
| 29 // └───┴───┴───┴───┴───┘ |
| 30 class CC_EXPORT SpiralIterator { |
| 31 public: |
| 32 SpiralIterator(); |
| 33 SpiralIterator(const IndexRect& around_index_rect, |
| 34 const IndexRect& consider_index_rect, |
| 35 const IndexRect& ignore_index_rect); |
| 36 |
| 37 ~SpiralIterator() = default; |
| 38 |
| 39 operator bool() const; |
| 40 SpiralIterator& operator++(); |
| 41 int index_x() const { return index_x_; } |
| 42 int index_y() const { return index_y_; } |
| 43 |
| 44 private: |
| 45 int current_step_count() const { |
| 46 return (direction_ == UP || direction_ == DOWN) ? vertical_step_count_ |
| 47 : horizontal_step_count_; |
| 48 } |
| 49 |
| 50 bool needs_direction_switch() const; |
| 51 void switch_direction(); |
| 52 |
| 53 enum Direction { UP, LEFT, DOWN, RIGHT }; |
| 54 |
| 55 IndexRect around_index_rect_; |
| 56 IndexRect consider_index_rect_; |
| 57 IndexRect ignore_index_rect_; |
| 58 int index_x_; |
| 59 int index_y_; |
| 60 |
| 61 Direction direction_; |
| 62 int delta_x_; |
| 63 int delta_y_; |
| 64 int current_step_; |
| 65 int horizontal_step_count_; |
| 66 int vertical_step_count_; |
| 67 }; |
| 68 |
| 69 } // namespace cc |
| 70 |
| 71 #endif // CC_BASE_SPIRAL_ITERATOR_H_ |
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