third_party/blink/renderer/core/editing/position_iterator.h

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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_POSITION_ITERATOR_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_POSITION_ITERATOR_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/core/dom/node.h"
#include "third_party/blink/renderer/core/editing/editing_strategy.h"
#include "third_party/blink/renderer/core/editing/forward.h"

namespace blink {

// A Position iterator with nearly constant-time
// increment, decrement, and several predicates on the Position it is at.
// Conversion from Position is O(n) in the depth.
// Conversion to Position is O(1).
// PositionIteratorAlgorithm must be used without DOM tree change.
template <typename Strategy>
class SlowPositionIteratorAlgorithm {
  STACK_ALLOCATED();

 public:
  explicit SlowPositionIteratorAlgorithm(const PositionTemplate<Strategy>&);

  // Since |deprecatedComputePosition()| is slow, new code should use
  // |computePosition()| instead.
  PositionTemplate<Strategy> DeprecatedComputePosition() const;
  PositionTemplate<Strategy> ComputePosition() const;

  // increment() takes O(1) other than incrementing to a element that has
  // new parent.
  // In the later case, it takes time of O(<number of childlen>) but the case
  // happens at most depth-of-the-tree times over whole tree traversal.
  void Increment();
  // decrement() takes O(1) other than decrement into new node that has
  // childlen.
  // In the later case, it takes time of O(<number of childlen>).
  void Decrement();

  Node* GetNode() const { return anchor_node_; }

  int OffsetInTextNode() const {
    DCHECK(anchor_node_->IsTextNode());
    return offset_in_anchor_;
  }

  bool AtStart() const;
  bool AtEnd() const;
  bool AtStartOfNode() const;
  bool AtEndOfNode() const;

 private:
  bool IsValid() const {
    return !anchor_node_ ||
           dom_tree_version_ == anchor_node_->GetDocument().DomTreeVersion();
  }

  Node* anchor_node_ = nullptr;
  // If this is non-null, Strategy::Parent(*node_after_position_in_anchor_) ==
  // anchor_node_;
  Node* node_after_position_in_anchor_ = nullptr;
  // In `Decrement()` `offset_in_anchor_` may not be valid.
  int offset_in_anchor_ = 0;
  wtf_size_t depth_to_anchor_node_ = 0;
  // If |node_after_position_in_anchor_| is not null,
  // offsets_in_anchor_node_[depth_to_anchor_node_] ==
  //    Strategy::Index(node_after_position_in_anchor_).
  Vector<int> offsets_in_anchor_node_;
  uint64_t dom_tree_version_ = 0;
};

extern template class CORE_EXTERN_TEMPLATE_EXPORT
    SlowPositionIteratorAlgorithm<EditingStrategy>;
extern template class CORE_EXTERN_TEMPLATE_EXPORT
    SlowPositionIteratorAlgorithm<EditingInFlatTreeStrategy>;

using SlowPositionIterator = SlowPositionIteratorAlgorithm<EditingStrategy>;
using SlowPositionIteratorInFlatTree =
    SlowPositionIteratorAlgorithm<EditingInFlatTreeStrategy>;

// ----

// A Position iterator with nearly constant-time
// increment, decrement, and several predicates on the Position it is at.
// Conversion from Position is O(n) in the depth.
// Conversion to Position is O(1).
// PositionIteratorAlgorithm must be used without DOM tree change.
template <typename Strategy>
class FastPositionIteratorAlgorithm {
  STACK_ALLOCATED();

 public:
  using PositionType = PositionTemplate<Strategy>;

  // When `position` is `kOffsetInAnchor`. It takes O(n) where n is an offset
  // in container node.
  explicit FastPositionIteratorAlgorithm(const PositionType& position);
  FastPositionIteratorAlgorithm();

  // Since `DeprecatedComputePosition()` is slow, new code should use
  // `ComputePosition()` instead.
  PositionType DeprecatedComputePosition() const;
  PositionType ComputePosition() const;

  // `Decrement()` takes O(1).
  void Decrement();
  // `Increment()` takes O(1).
  void Increment();

  Node* GetNode() const { return container_node_; }
  int OffsetInTextNode() const;

  bool AtStart() const;
  bool AtEnd() const;
  bool AtStartOfNode() const;
  bool AtEndOfNode() const;

 private:
  enum ContainerType {
    kNullNode,

    kNoChildren,
    kCharacterData,
    kContainerNode,
    kTextNode,
    kUserSelectContainNode,
  };

  static constexpr unsigned kInvalidOffset = static_cast<unsigned>(-1);

  static ContainerType ContainerToContainerType(const Node* node);

  void Initialize(const PositionType& position);

  void AssertOffsetInContainerIsValid() const;
  void AssertOffsetStackIsValid() const;
  bool IsValid() const;

  Node* ChildAfterPosition() const;
  bool HasChildren() const;
  bool IgnoresChildren() const;
  bool IsUserSelectContain() const;

  void IncrementInternal();
  void DecrementInternal();

  void MoveToNextContainer();
  void MoveToNextSkippingChildren();
  void MoveToPreviousContainer();
  void MoveToPreviousSkippingChildren();

  // Set `child_before_position_` to `Strategy::PreviousChildren(node)`
  // and set `offset_` to zero if `child_before_position_` becomes
  // `nullptr`.
  void SetChildBeforePositionToPreviosuSigblingOf(const Node& node);

  // Set `container_node_` to `node` and `container_type` from `node.
  void SetContainer(Node* node);

  // Returns `PositionType::AfterNode(*container_node_)` if
  // `offset_in_container_` is non-zero, otherwise `BeforeNode()`.
  PositionType BeforeOrAfterPosition() const;
  bool IsBeforePosition() const;

  void EnsureOffsetInContainer() const;
  void MoveOffsetInContainerBy(int delta);
  void PopOffsetStack();
  void PushThenSetOffset(unsigned offset_in_container);

  // We representation a position as same as`RangeBoundaryPoint`.
  Node* container_node_ = nullptr;
  Node* child_before_position_ = nullptr;
  uint64_t dom_tree_version_ = 0;
  // Note: When `child_before_position_` is `nullptr`, `offset_is_container`
  // should be zero.
  mutable unsigned offset_in_container_ = kInvalidOffset;

  Vector<unsigned> offset_stack_;
  ContainerType container_type_ = kNullNode;
};

extern template class CORE_EXTERN_TEMPLATE_EXPORT
    FastPositionIteratorAlgorithm<EditingStrategy>;
extern template class CORE_EXTERN_TEMPLATE_EXPORT
    FastPositionIteratorAlgorithm<EditingInFlatTreeStrategy>;

using FastPositionIterator = FastPositionIteratorAlgorithm<EditingStrategy>;
using FastPositionIteratorInFlatTree =
    FastPositionIteratorAlgorithm<EditingInFlatTreeStrategy>;

// --

// The switcher of `FastPositionIterator` and `SlowPositionIterator` based on
// `RuntimeEnabledFeatures::FastPositionItertorEnabled()`.
template <typename Strategy>
class PositionIteratorAlgorithm {
  STACK_ALLOCATED();

 public:
  explicit PositionIteratorAlgorithm(
      const PositionTemplate<Strategy>& position);

  PositionIteratorAlgorithm(const PositionIteratorAlgorithm<Strategy>& other);

  PositionIteratorAlgorithm& operator=(
      const PositionIteratorAlgorithm<Strategy>& other);

  PositionTemplate<Strategy> DeprecatedComputePosition() const;
  PositionTemplate<Strategy> ComputePosition() const;

  void Increment();
  void Decrement();

  Node* GetNode() const;
  int OffsetInTextNode() const;

  bool AtStart() const;
  bool AtEnd() const;
  bool AtStartOfNode() const;
  bool AtEndOfNode() const;

 private:
  FastPositionIteratorAlgorithm<Strategy> fast_;
  SlowPositionIteratorAlgorithm<Strategy> slow_;
};

extern template class CORE_EXTERN_TEMPLATE_EXPORT
    PositionIteratorAlgorithm<EditingStrategy>;
extern template class CORE_EXTERN_TEMPLATE_EXPORT
    PositionIteratorAlgorithm<EditingInFlatTreeStrategy>;

using PositionIterator = PositionIteratorAlgorithm<EditingStrategy>;
using PositionIteratorInFlatTree =
    PositionIteratorAlgorithm<EditingInFlatTreeStrategy>;

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_EDITING_POSITION_ITERATOR_H_