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 * in the documentation and/or other materials provided with the
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
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#ifndef SKY_ENGINE_CORE_RENDERING_RENDERLAYERSTACKINGNODEITERATOR_H_
#define SKY_ENGINE_CORE_RENDERING_RENDERLAYERSTACKINGNODEITERATOR_H_

#include "sky/engine/wtf/Noncopyable.h"

namespace blink {

enum ChildrenIteration {
    NormalFlowChildren = 1,
    PositiveZOrderChildren = 1 << 1,
    AllChildren = NormalFlowChildren | PositiveZOrderChildren
};

class RenderLayerStackingNode;

// This iterator walks the RenderLayerStackingNode lists in the following order:
// NormalFlowChildren -> PositiveZOrderChildren.
class RenderLayerStackingNodeIterator {
    WTF_MAKE_NONCOPYABLE(RenderLayerStackingNodeIterator);
public:
    RenderLayerStackingNodeIterator(const RenderLayerStackingNode& root, unsigned whichChildren)
        : m_root(root)
        , m_remainingChildren(whichChildren)
        , m_index(0)
    {
    }

    RenderLayerStackingNode* next();

private:
    const RenderLayerStackingNode& m_root;
    unsigned m_remainingChildren;
    unsigned m_index;
};

// This iterator is similar to RenderLayerStackingNodeIterator but it walks the lists in reverse order
// (from the last item to the first one).
class RenderLayerStackingNodeReverseIterator {
    WTF_MAKE_NONCOPYABLE(RenderLayerStackingNodeReverseIterator);
public:
    RenderLayerStackingNodeReverseIterator(const RenderLayerStackingNode& root, unsigned whichChildren)
        : m_root(root)
        , m_remainingChildren(whichChildren)
    {
        setIndexToLastItem();
    }

    RenderLayerStackingNode* next();

private:
    void setIndexToLastItem();

    const RenderLayerStackingNode& m_root;
    unsigned m_remainingChildren;
    int m_index;
};

} // namespace blink

#endif  // SKY_ENGINE_CORE_RENDERING_RENDERLAYERSTACKINGNODEITERATOR_H_