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// 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/layers/layer_list_iterator.h"
#include "cc/layers/layer_impl.h"
namespace cc {
LayerListIterator::LayerListIterator(LayerImpl* root_layer)
: current_layer_(root_layer) {
DCHECK(!root_layer || !root_layer->parent());
list_indices_.push_back(0);
}
LayerListIterator::LayerListIterator(const LayerListIterator& other) = default;
LayerListIterator::~LayerListIterator() {}
LayerListIterator& LayerListIterator::operator++() {
// case 0: done
if (!current_layer_)
return *this;
// case 1: descend.
const LayerImplList& current_list = current_layer_->children();
if (!current_list.empty()) {
current_layer_ = current_list[0];
list_indices_.push_back(0);
return *this;
}
for (LayerImpl* parent = current_layer_->parent(); parent;
parent = parent->parent()) {
// We now try and advance in some list of siblings.
const LayerImplList& sibling_list = parent->children();
// case 2: Advance to a sibling.
if (list_indices_.back() + 1 < sibling_list.size()) {
++list_indices_.back();
current_layer_ = sibling_list[list_indices_.back()];
return *this;
}
// We need to ascend. We will pop an index off the stack.
list_indices_.pop_back();
}
current_layer_ = nullptr;
return *this;
}
LayerListReverseIterator::LayerListReverseIterator(LayerImpl* root_layer)
: LayerListIterator(root_layer) {
DescendToRightmostInSubtree();
}
LayerListReverseIterator::~LayerListReverseIterator() {}
// We will only support prefix increment.
LayerListIterator& LayerListReverseIterator::operator++() {
// case 0: done
if (!current_layer_)
return *this;
// case 1: we're the leftmost sibling.
if (!list_indices_.back()) {
list_indices_.pop_back();
current_layer_ = current_layer_->parent();
return *this;
}
// case 2: we're not the leftmost sibling. In this case, we want to move one
// sibling over, and then descend to the rightmost descendant in that subtree.
CHECK(current_layer_->parent());
--list_indices_.back();
const LayerImplList& parent_list = current_layer_->parent()->children();
current_layer_ = parent_list[list_indices_.back()];
DescendToRightmostInSubtree();
return *this;
}
void LayerListReverseIterator::DescendToRightmostInSubtree() {
if (!current_layer_)
return;
const LayerImplList& current_list = current_layer_->children();
if (current_list.empty())
return;
size_t last_index = current_list.size() - 1;
current_layer_ = current_list[last_index];
list_indices_.push_back(last_index);
DescendToRightmostInSubtree();
}
} // namespace cc
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