| // 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. |
| |
| #include "cc/base/spiral_iterator.h" |
| |
| #include "base/check_op.h" |
| |
| #include <algorithm> |
| |
| namespace cc { |
| |
| SpiralIterator::SpiralIterator() |
| : around_index_rect_(-1, -1, -1, -1), |
| consider_index_rect_(-1, -1, -1, -1), |
| ignore_index_rect_(-1, -1, -1, -1), |
| index_x_(-1), |
| index_y_(-1) {} |
| |
| SpiralIterator::SpiralIterator(const IndexRect& around_index_rect, |
| const IndexRect& consider_index_rect, |
| const IndexRect& ignore_index_rect) |
| : around_index_rect_(around_index_rect), |
| consider_index_rect_(consider_index_rect), |
| ignore_index_rect_(ignore_index_rect), |
| index_x_(-1), |
| index_y_(-1), |
| direction_(RIGHT), |
| delta_x_(1), |
| delta_y_(0), |
| current_step_(0), |
| horizontal_step_count_(0), |
| vertical_step_count_(0) { |
| vertical_step_count_ = around_index_rect_.num_indices_y(); |
| horizontal_step_count_ = around_index_rect_.num_indices_x(); |
| current_step_ = horizontal_step_count_ - 1; |
| |
| index_x_ = around_index_rect_.right(); |
| index_y_ = around_index_rect_.bottom(); |
| |
| // The current index is the bottom right of the around rect, which is also |
| // ignored. So we have to advance. |
| ++(*this); |
| } |
| |
| SpiralIterator::operator bool() const { |
| return index_x_ != -1 && index_y_ != -1; |
| } |
| |
| SpiralIterator& SpiralIterator::operator++() { |
| int cannot_hit_consider_count = 0; |
| while (cannot_hit_consider_count < 4) { |
| if (needs_direction_switch()) |
| switch_direction(); |
| |
| index_x_ += delta_x_; |
| index_y_ += delta_y_; |
| ++current_step_; |
| |
| if (consider_index_rect_.Contains(index_x_, index_y_)) { |
| cannot_hit_consider_count = 0; |
| |
| if (!ignore_index_rect_.Contains(index_x_, index_y_)) |
| break; |
| |
| // Steps needed to reach the very edge of the ignore rect, while remaining |
| // inside (so that the continue would take us outside). |
| int steps_to_edge = 0; |
| switch (direction_) { |
| case UP: |
| steps_to_edge = index_y_ - ignore_index_rect_.top(); |
| break; |
| case LEFT: |
| steps_to_edge = index_x_ - ignore_index_rect_.left(); |
| break; |
| case DOWN: |
| steps_to_edge = ignore_index_rect_.bottom() - index_y_; |
| break; |
| case RIGHT: |
| steps_to_edge = ignore_index_rect_.right() - index_x_; |
| break; |
| } |
| |
| // We need to switch directions in |max_steps|. |
| int max_steps = current_step_count() - current_step_; |
| |
| int steps_to_take = std::min(steps_to_edge, max_steps); |
| DCHECK_GE(steps_to_take, 0); |
| |
| index_x_ += steps_to_take * delta_x_; |
| index_y_ += steps_to_take * delta_y_; |
| current_step_ += steps_to_take; |
| } else { |
| int max_steps = current_step_count() - current_step_; |
| int steps_to_take = max_steps; |
| bool can_hit_consider_rect = false; |
| switch (direction_) { |
| case UP: |
| if (consider_index_rect_.valid_column(index_x_) && |
| consider_index_rect_.bottom() < index_y_) |
| steps_to_take = index_y_ - consider_index_rect_.bottom() - 1; |
| can_hit_consider_rect |= consider_index_rect_.right() >= index_x_; |
| break; |
| case LEFT: |
| if (consider_index_rect_.valid_row(index_y_) && |
| consider_index_rect_.right() < index_x_) |
| steps_to_take = index_x_ - consider_index_rect_.right() - 1; |
| can_hit_consider_rect |= consider_index_rect_.top() <= index_y_; |
| break; |
| case DOWN: |
| if (consider_index_rect_.valid_column(index_x_) && |
| consider_index_rect_.top() > index_y_) |
| steps_to_take = consider_index_rect_.top() - index_y_ - 1; |
| can_hit_consider_rect |= consider_index_rect_.left() <= index_x_; |
| break; |
| case RIGHT: |
| if (consider_index_rect_.valid_row(index_y_) && |
| consider_index_rect_.left() > index_x_) |
| steps_to_take = consider_index_rect_.left() - index_x_ - 1; |
| can_hit_consider_rect |= consider_index_rect_.bottom() >= index_y_; |
| break; |
| } |
| steps_to_take = std::min(steps_to_take, max_steps); |
| DCHECK_GE(steps_to_take, 0); |
| |
| index_x_ += steps_to_take * delta_x_; |
| index_y_ += steps_to_take * delta_y_; |
| current_step_ += steps_to_take; |
| |
| if (can_hit_consider_rect) |
| cannot_hit_consider_count = 0; |
| else |
| ++cannot_hit_consider_count; |
| } |
| } |
| |
| if (cannot_hit_consider_count >= 4) { |
| index_x_ = -1; |
| index_y_ = -1; |
| } |
| |
| return *this; |
| } |
| |
| bool SpiralIterator::needs_direction_switch() const { |
| return current_step_ >= current_step_count(); |
| } |
| |
| void SpiralIterator::switch_direction() { |
| // Note that delta_x_ and delta_y_ always remain between -1 and 1. |
| int new_delta_x = delta_y_; |
| delta_y_ = -delta_x_; |
| delta_x_ = new_delta_x; |
| |
| current_step_ = 0; |
| direction_ = static_cast<Direction>((direction_ + 1) % 4); |
| |
| if (direction_ == RIGHT || direction_ == LEFT) { |
| ++vertical_step_count_; |
| ++horizontal_step_count_; |
| } |
| } |
| |
| } // namespace cc |