third_party/blink/renderer/core/paint/paint_layer_stacking_node_iterator.h

/*
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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_PAINT_PAINT_LAYER_STACKING_NODE_ITERATOR_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_PAINT_PAINT_LAYER_STACKING_NODE_ITERATOR_H_

#include "base/macros.h"
#include "third_party/blink/renderer/platform/wtf/allocator.h"

namespace blink {

enum ChildrenIteration {
  kNegativeZOrderChildren = 1,
  // Normal flow children are not mandated by CSS 2.1 but are an artifact of
  // our implementation: we allocate PaintLayers for elements that
  // are not treated as stacking contexts and thus we need to walk them
  // during painting and hit-testing.
  kNormalFlowChildren = 1 << 1,
  kPositiveZOrderChildren = 1 << 2,
  kAllChildren =
      kNegativeZOrderChildren | kNormalFlowChildren | kPositiveZOrderChildren
};

class PaintLayerStackingNode;
class PaintLayer;

// This iterator walks the PaintLayerStackingNode lists in the following order:
// NegativeZOrderChildren -> NormalFlowChildren -> PositiveZOrderChildren.
class PaintLayerStackingNodeIterator {
  STACK_ALLOCATED();

 public:
  PaintLayerStackingNodeIterator(const PaintLayerStackingNode& root,
                                 unsigned which_children);

  PaintLayer* Next();

 private:
  const PaintLayerStackingNode& root_;
  unsigned remaining_children_;
  unsigned index_;
  PaintLayer* current_normal_flow_child_;
  DISALLOW_COPY_AND_ASSIGN(PaintLayerStackingNodeIterator);
};

// This iterator is similar to PaintLayerStackingNodeIterator but it walks the
// lists in reverse order (from the last item to the first one).
class PaintLayerStackingNodeReverseIterator {
  STACK_ALLOCATED();

 public:
  PaintLayerStackingNodeReverseIterator(const PaintLayerStackingNode& root,
                                        unsigned which_children)
      : root_(root), remaining_children_(which_children) {
    SetIndexToLastItem();
  }

  PaintLayer* Next();

 private:
  void SetIndexToLastItem();

  const PaintLayerStackingNode& root_;
  unsigned remaining_children_;
  int index_;
  PaintLayer* current_normal_flow_child_;
  DISALLOW_COPY_AND_ASSIGN(PaintLayerStackingNodeReverseIterator);
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_PAINT_PAINT_LAYER_STACKING_NODE_ITERATOR_H_