path: root/chromium/third_party/blink/renderer/core/dom/element_data.h

/*
 * Copyright (C) 2013 Google Inc. All rights reserved.
 * Copyright (C) 2014 Apple Inc. All rights reserved.
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 * modification, are permitted provided that the following conditions are
 * met:
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 * in the documentation and/or other materials provided with the
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 * this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_DOM_ELEMENT_DATA_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_DOM_ELEMENT_DATA_H_

#include "build/build_config.h"
#include "third_party/blink/renderer/core/dom/attribute.h"
#include "third_party/blink/renderer/core/dom/attribute_collection.h"
#include "third_party/blink/renderer/core/dom/space_split_string.h"
#include "third_party/blink/renderer/platform/heap/handle.h"
#include "third_party/blink/renderer/platform/wtf/casting.h"
#include "third_party/blink/renderer/platform/wtf/text/atomic_string.h"

namespace blink {

class ShareableElementData;
class CSSPropertyValueSet;
class UniqueElementData;

// ElementData represents very common, but not necessarily unique to an element,
// data such as attributes, inline style, and parsed class names and ids.
class ElementData : public GarbageCollected<ElementData> {
 public:
  // Override GarbageCollected's finalizeGarbageCollectedObject to
  // dispatch to the correct subclass destructor.
  void FinalizeGarbageCollectedObject();

  void ClearClass() const { class_names_.Clear(); }
  void SetClass(const AtomicString& class_name, bool should_fold_case) const {
    class_names_.Set(should_fold_case ? class_name.LowerASCII() : class_name);
  }
  const SpaceSplitString& ClassNames() const { return class_names_; }

  const AtomicString& IdForStyleResolution() const {
    return id_for_style_resolution_;
  }
  void SetIdForStyleResolution(const AtomicString& new_id) const {
    id_for_style_resolution_ = new_id;
  }

  const CSSPropertyValueSet* InlineStyle() const { return inline_style_.Get(); }

  const CSSPropertyValueSet* PresentationAttributeStyle() const;

  AttributeCollection Attributes() const;

  bool HasID() const { return !id_for_style_resolution_.IsNull(); }
  bool HasClass() const { return !class_names_.IsNull(); }

  bool IsEquivalent(const ElementData* other) const;

  bool IsUnique() const { return is_unique_; }

  void TraceAfterDispatch(blink::Visitor*);
  void Trace(Visitor*);

 protected:
  ElementData();
  explicit ElementData(unsigned array_size);
  ElementData(const ElementData&, bool is_unique);

  // Keep the type in a bitfield instead of using virtual destructors to avoid
  // adding a vtable.
  unsigned is_unique_ : 1;
  unsigned array_size_ : 28;
  mutable unsigned presentation_attribute_style_is_dirty_ : 1;
  mutable unsigned style_attribute_is_dirty_ : 1;
  mutable unsigned animated_svg_attributes_are_dirty_ : 1;

  mutable Member<CSSPropertyValueSet> inline_style_;
  mutable SpaceSplitString class_names_;
  mutable AtomicString id_for_style_resolution_;

 private:
  friend class Element;
  friend class ShareableElementData;
  friend class UniqueElementData;
  friend class SVGElement;

  UniqueElementData* MakeUniqueCopy() const;
};

#if defined(COMPILER_MSVC)
#pragma warning(push)
// Disable "zero-sized array in struct/union" warning
#pragma warning(disable : 4200)
#endif

// SharableElementData is managed by ElementDataCache and is produced by
// the parser during page load for elements that have identical attributes. This
// is a memory optimization since it's very common for many elements to have
// duplicate sets of attributes (ex. the same classes).
class ShareableElementData final : public ElementData {
 public:
  static ShareableElementData* CreateWithAttributes(const Vector<Attribute>&);

  explicit ShareableElementData(const Vector<Attribute>&);
  explicit ShareableElementData(const UniqueElementData&);
  ~ShareableElementData();

  void TraceAfterDispatch(blink::Visitor* visitor) {
    ElementData::TraceAfterDispatch(visitor);
  }

  AttributeCollection Attributes() const;

  Attribute attribute_array_[0];
};

template <>
struct DowncastTraits<ShareableElementData> {
  static bool AllowFrom(const ElementData& data) { return !data.IsUnique(); }
};

#if defined(COMPILER_MSVC)
#pragma warning(pop)
#endif

// UniqueElementData is created when an element needs to mutate its attributes
// or gains presentation attribute style (ex. width="10"). It does not need to
// be created to fill in values in the ElementData that are derived from
// attributes. For example populating the inline_style_ from the style attribute
// doesn't require a UniqueElementData as all elements with the same style
// attribute will have the same inline style.
class UniqueElementData final : public ElementData {
 public:
  ShareableElementData* MakeShareableCopy() const;

  MutableAttributeCollection Attributes();
  AttributeCollection Attributes() const;

  UniqueElementData();
  explicit UniqueElementData(const ShareableElementData&);
  explicit UniqueElementData(const UniqueElementData&);

  void TraceAfterDispatch(blink::Visitor*);

  // FIXME: We might want to support sharing element data for elements with
  // presentation attribute style. Lots of table cells likely have the same
  // attributes. Most modern pages don't use presentation attributes though
  // so this might not make sense.
  mutable Member<CSSPropertyValueSet> presentation_attribute_style_;
  AttributeVector attribute_vector_;
};

template <>
struct DowncastTraits<UniqueElementData> {
  static bool AllowFrom(const ElementData& data) { return data.IsUnique(); }
};

inline const CSSPropertyValueSet* ElementData::PresentationAttributeStyle()
    const {
  if (!is_unique_)
    return nullptr;
  return To<UniqueElementData>(this)->presentation_attribute_style_.Get();
}

inline AttributeCollection ElementData::Attributes() const {
  if (auto* unique_element_data = DynamicTo<UniqueElementData>(this))
    return unique_element_data->Attributes();
  return To<ShareableElementData>(this)->Attributes();
}

inline AttributeCollection ShareableElementData::Attributes() const {
  return AttributeCollection(attribute_array_, array_size_);
}

inline AttributeCollection UniqueElementData::Attributes() const {
  return AttributeCollection(attribute_vector_.data(),
                             attribute_vector_.size());
}

inline MutableAttributeCollection UniqueElementData::Attributes() {
  return MutableAttributeCollection(attribute_vector_);
}

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_DOM_ELEMENT_DATA_H_