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// Copyright 2016 The Chromium Authors
// 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_(Direction::kRight),
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 Direction::kUp:
steps_to_edge = index_y_ - ignore_index_rect_.top();
break;
case Direction::kLeft:
steps_to_edge = index_x_ - ignore_index_rect_.left();
break;
case Direction::kDown:
steps_to_edge = ignore_index_rect_.bottom() - index_y_;
break;
case Direction::kRight:
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 Direction::kUp:
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 Direction::kLeft:
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 Direction::kDown:
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 Direction::kRight:
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>((static_cast<int>(direction_) + 1) % 4);
if (direction_ == Direction::kRight || direction_ == Direction::kLeft) {
++vertical_step_count_;
++horizontal_step_count_;
}
}
} // namespace cc
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