/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * Base class for all element classes; this provides an implementation
 * of DOM Core's Element, implements nsIContent, provides
 * utility methods for subclasses, and so forth.
 */

#ifndef mozilla_dom_Element_h__
#define mozilla_dom_Element_h__

#include "AttrArray.h"
#include "nsAttrValue.h"
#include "nsAttrValueInlines.h"
#include "nsChangeHint.h"
#include "nsContentUtils.h"
#include "nsDOMAttributeMap.h"
#include "nsINodeList.h"
#include "nsIScrollableFrame.h"
#include "Units.h"
#include "mozilla/Attributes.h"
#include "mozilla/CORSMode.h"
#include "mozilla/EventForwards.h"
#include "mozilla/EventStates.h"
#include "mozilla/FlushType.h"
#include "mozilla/PseudoStyleType.h"
#include "mozilla/RustCell.h"
#include "mozilla/SMILAttr.h"
#include "mozilla/UniquePtr.h"
#include "mozilla/dom/Attr.h"
#include "mozilla/dom/BindingDeclarations.h"
#include "mozilla/dom/DirectionalityUtils.h"
#include "mozilla/dom/FragmentOrElement.h"
#include "mozilla/dom/DOMRect.h"
#include "mozilla/dom/DOMTokenListSupportedTokens.h"
#include "mozilla/dom/ElementBinding.h"
#include "mozilla/dom/Nullable.h"
#include "mozilla/dom/PointerEventHandler.h"
#include "mozilla/dom/WindowBinding.h"

class mozAutoDocUpdate;
class nsIFrame;
class nsIMozBrowserFrame;
class nsIURI;
class nsIScrollableFrame;
class nsAttrValueOrString;
class nsContentList;
class nsDOMTokenList;
struct nsRect;
class nsFocusManager;
class nsGlobalWindowInner;
class nsGlobalWindowOuter;
class nsDOMCSSAttributeDeclaration;
class nsDOMStringMap;
struct ServoNodeData;

class nsIDOMXULButtonElement;
class nsIDOMXULContainerElement;
class nsIDOMXULContainerItemElement;
class nsIDOMXULControlElement;
class nsIDOMXULMenuListElement;
class nsIDOMXULMultiSelectControlElement;
class nsIDOMXULRadioGroupElement;
class nsIDOMXULRelatedElement;
class nsIDOMXULSelectControlElement;
class nsIDOMXULSelectControlItemElement;
class nsIBrowser;
class nsIAutoCompletePopup;

namespace mozilla {
class DeclarationBlock;
struct MutationClosureData;
class TextEditor;
namespace css {
struct URLValue;
}  // namespace css
namespace dom {
struct GetAnimationsOptions;
struct ScrollIntoViewOptions;
struct ScrollToOptions;
class DOMIntersectionObserver;
class DOMMatrixReadOnly;
class Element;
class ElementOrCSSPseudoElement;
class UnrestrictedDoubleOrKeyframeAnimationOptions;
enum class CallerType : uint32_t;
typedef nsDataHashtable<nsRefPtrHashKey<DOMIntersectionObserver>, int32_t>
    IntersectionObserverList;
}  // namespace dom
}  // namespace mozilla

// Declared here because of include hell.
extern "C" bool Servo_Element_IsDisplayContents(const mozilla::dom::Element*);

already_AddRefed<nsContentList> NS_GetContentList(nsINode* aRootNode,
                                                  int32_t aMatchNameSpaceId,
                                                  const nsAString& aTagname);

#define ELEMENT_FLAG_BIT(n_) \
  NODE_FLAG_BIT(NODE_TYPE_SPECIFIC_BITS_OFFSET + (n_))

// Element-specific flags
enum {
  // Whether this node has dirty descendants for Servo's style system.
  ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO = ELEMENT_FLAG_BIT(0),
  // Whether this node has dirty descendants for animation-only restyle for
  // Servo's style system.
  ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO = ELEMENT_FLAG_BIT(1),

  // Whether the element has been snapshotted due to attribute or state changes
  // by the Servo restyle manager.
  ELEMENT_HAS_SNAPSHOT = ELEMENT_FLAG_BIT(2),

  // Whether the element has already handled its relevant snapshot.
  //
  // Used by the servo restyle process in order to accurately track whether the
  // style of an element is up-to-date, even during the same restyle process.
  ELEMENT_HANDLED_SNAPSHOT = ELEMENT_FLAG_BIT(3),

  // Remaining bits are for subclasses
  ELEMENT_TYPE_SPECIFIC_BITS_OFFSET = NODE_TYPE_SPECIFIC_BITS_OFFSET + 4
};

#undef ELEMENT_FLAG_BIT

// Make sure we have space for our bits
ASSERT_NODE_FLAGS_SPACE(ELEMENT_TYPE_SPECIFIC_BITS_OFFSET);

namespace mozilla {
enum class PseudoStyleType : uint8_t;
class EventChainPostVisitor;
class EventChainPreVisitor;
class EventChainVisitor;
class EventListenerManager;
class EventStateManager;

namespace dom {

struct CustomElementDefinition;
class Animation;
class CustomElementRegistry;
class Link;
class DOMRect;
class DOMRectList;
class Flex;
class Grid;

// IID for the dom::Element interface
#define NS_ELEMENT_IID                               \
  {                                                  \
    0xc67ed254, 0xfd3b, 0x4b10, {                    \
      0x96, 0xa2, 0xc5, 0x8b, 0x7b, 0x64, 0x97, 0xd1 \
    }                                                \
  }

#define REFLECT_NULLABLE_DOMSTRING_ATTR(method, attr)           \
  void Get##method(nsAString& aValue) const {                   \
    if (!GetAttr(nsGkAtoms::attr, aValue)) {                    \
      SetDOMStringToNull(aValue);                               \
    }                                                           \
  }                                                             \
  void Set##method(const nsAString& aValue, ErrorResult& aRv) { \
    SetAttr(nsGkAtoms::attr, aValue, aRv);                      \
  }

class Element : public FragmentOrElement {
 public:
#ifdef MOZILLA_INTERNAL_API
  explicit Element(already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo)
      : FragmentOrElement(std::move(aNodeInfo)),
        mState(NS_EVENT_STATE_MOZ_READONLY | NS_EVENT_STATE_DEFINED) {
    MOZ_ASSERT(mNodeInfo->NodeType() == ELEMENT_NODE,
               "Bad NodeType in aNodeInfo");
    SetIsElement();
  }

  ~Element() {
    NS_ASSERTION(!HasServoData(), "expected ServoData to be cleared earlier");
  }

#endif  // MOZILLA_INTERNAL_API

  NS_DECLARE_STATIC_IID_ACCESSOR(NS_ELEMENT_IID)

  NS_DECL_ADDSIZEOFEXCLUDINGTHIS

  NS_IMPL_FROMNODE_HELPER(Element, IsElement())

  NS_IMETHOD QueryInterface(REFNSIID aIID, void** aInstancePtr) override;

  /**
   * Method to get the full state of this element.  See mozilla/EventStates.h
   * for the possible bits that could be set here.
   */
  EventStates State() const {
    // mState is maintained by having whoever might have changed it
    // call UpdateState() or one of the other mState mutators.
    return mState;
  }

  /**
   * Ask this element to update its state.  If aNotify is false, then
   * state change notifications will not be dispatched; in that
   * situation it is the caller's responsibility to dispatch them.
   *
   * In general, aNotify should only be false if we're guaranteed that
   * the element can't have a frame no matter what its style is
   * (e.g. if we're in the middle of adding it to the document or
   * removing it from the document).
   */
  void UpdateState(bool aNotify);

  /**
   * Method to update mState with link state information.  This does not notify.
   */
  void UpdateLinkState(EventStates aState);

  virtual int32_t TabIndexDefault() { return -1; }

  /**
   * Get tabIndex of this element. If not found, return TabIndexDefault.
   */
  int32_t TabIndex();

  /**
   * Get the parsed value of tabindex attribute.
   */
  Maybe<int32_t> GetTabIndexAttrValue();

  /**
   * Set tabIndex value to this element.
   */
  void SetTabIndex(int32_t aTabIndex, mozilla::ErrorResult& aError);

  /**
   * Sets the ShadowRoot binding for this element. The contents of the
   * binding is rendered in place of this node's children.
   *
   * @param aShadowRoot The ShadowRoot to be bound to this element.
   */
  void SetShadowRoot(ShadowRoot* aShadowRoot);

  /**
   * Make focus on this element.
   */
  virtual void Focus(const FocusOptions& aOptions, const CallerType aCallerType,
                     ErrorResult& aError);

  /**
   * Show blur and clear focus.
   */
  virtual void Blur(mozilla::ErrorResult& aError);

  /**
   * The style state of this element. This is the real state of the element
   * with any style locks applied for pseudo-class inspecting.
   */
  EventStates StyleState() const {
    if (!HasLockedStyleStates()) {
      return mState;
    }
    return StyleStateFromLocks();
  }

  /**
   * StyleStateLocks is used to specify which event states should be locked,
   * and whether they should be locked to on or off.
   */
  struct StyleStateLocks {
    // mLocks tracks which event states should be locked.
    EventStates mLocks;
    // mValues tracks if the locked state should be on or off.
    EventStates mValues;
  };

  /**
   * The style state locks applied to this element.
   */
  StyleStateLocks LockedStyleStates() const;

  /**
   * Add a style state lock on this element.
   * aEnabled is the value to lock the given state bits to.
   */
  void LockStyleStates(EventStates aStates, bool aEnabled);

  /**
   * Remove a style state lock on this element.
   */
  void UnlockStyleStates(EventStates aStates);

  /**
   * Clear all style state locks on this element.
   */
  void ClearStyleStateLocks();

  /**
   * Accessors for the state of our dir attribute.
   */
  bool HasDirAuto() const {
    return State().HasState(NS_EVENT_STATE_DIR_ATTR_LIKE_AUTO);
  }

  /**
   * Elements with dir="rtl" or dir="ltr".
   */
  bool HasFixedDir() const {
    return State().HasAtLeastOneOfStates(NS_EVENT_STATE_DIR_ATTR_LTR |
                                         NS_EVENT_STATE_DIR_ATTR_RTL);
  }

  /**
   * Get the inline style declaration, if any, for this element.
   */
  DeclarationBlock* GetInlineStyleDeclaration() const;

  /**
   * Get the mapped attributes, if any, for this element.
   */
  const nsMappedAttributes* GetMappedAttributes() const;

  void ClearMappedServoStyle() { mAttrs.ClearMappedServoStyle(); }

  /**
   * InlineStyleDeclarationWillChange is called before SetInlineStyleDeclaration
   * so that the element implementation can access the old style attribute
   * value.
   */
  virtual void InlineStyleDeclarationWillChange(MutationClosureData& aData);

  /**
   * Set the inline style declaration for this element.
   */
  virtual nsresult SetInlineStyleDeclaration(DeclarationBlock& aDeclaration,
                                             MutationClosureData& aData);

  /**
   * Get the SMIL override style declaration for this element. If the
   * rule hasn't been created, this method simply returns null.
   */
  DeclarationBlock* GetSMILOverrideStyleDeclaration();

  /**
   * Set the SMIL override style declaration for this element. This method will
   * notify the document's pres context, so that the style changes will be
   * noticed.
   */
  void SetSMILOverrideStyleDeclaration(DeclarationBlock&);

  /**
   * Returns a new SMILAttr that allows the caller to animate the given
   * attribute on this element.
   */
  virtual UniquePtr<SMILAttr> GetAnimatedAttr(int32_t aNamespaceID,
                                              nsAtom* aName) {
    return nullptr;
  }

  /**
   * Get the SMIL override style for this element. This is a style declaration
   * that is applied *after* the inline style, and it can be used e.g. to store
   * animated style values.
   *
   * Note: This method is analogous to the 'GetStyle' method in
   * nsGenericHTMLElement and nsStyledElement.
   */
  nsDOMCSSAttributeDeclaration* SMILOverrideStyle();

  /**
   * Returns if the element is labelable as per HTML specification.
   */
  virtual bool IsLabelable() const;

  /**
   * Returns if the element is interactive content as per HTML specification.
   */
  virtual bool IsInteractiveHTMLContent(bool aIgnoreTabindex) const;

  /**
   * Returns |this| as an nsIMozBrowserFrame* if the element is a frame or
   * iframe element.
   *
   * We have this method, rather than using QI, so that we can use it during
   * the servo traversal, where we can't QI DOM nodes because of non-thread-safe
   * refcounts.
   */
  virtual nsIMozBrowserFrame* GetAsMozBrowserFrame() { return nullptr; }

  /**
   * Is the attribute named stored in the mapped attributes?
   *
   * // XXXbz we use this method in HasAttributeDependentStyle, so svg
   *    returns true here even though it stores nothing in the mapped
   *    attributes.
   */
  NS_IMETHOD_(bool) IsAttributeMapped(const nsAtom* aAttribute) const;

  /**
   * Get a hint that tells the style system what to do when
   * an attribute on this node changes, if something needs to happen
   * in response to the change *other* than the result of what is
   * mapped into style data via any type of style rule.
   */
  virtual nsChangeHint GetAttributeChangeHint(const nsAtom* aAttribute,
                                              int32_t aModType) const;

  inline Directionality GetDirectionality() const {
    if (HasFlag(NODE_HAS_DIRECTION_RTL)) {
      return eDir_RTL;
    }

    if (HasFlag(NODE_HAS_DIRECTION_LTR)) {
      return eDir_LTR;
    }

    return eDir_NotSet;
  }

  inline void SetDirectionality(Directionality aDir, bool aNotify) {
    UnsetFlags(NODE_ALL_DIRECTION_FLAGS);
    if (!aNotify) {
      RemoveStatesSilently(DIRECTION_STATES);
    }

    switch (aDir) {
      case (eDir_RTL):
        SetFlags(NODE_HAS_DIRECTION_RTL);
        if (!aNotify) {
          AddStatesSilently(NS_EVENT_STATE_RTL);
        }
        break;

      case (eDir_LTR):
        SetFlags(NODE_HAS_DIRECTION_LTR);
        if (!aNotify) {
          AddStatesSilently(NS_EVENT_STATE_LTR);
        }
        break;

      default:
        break;
    }

    /*
     * Only call UpdateState if we need to notify, because we call
     * SetDirectionality for every element, and UpdateState is very very slow
     * for some elements.
     */
    if (aNotify) {
      UpdateState(true);
    }
  }

  Directionality GetComputedDirectionality() const;

  static const uint32_t kAllServoDescendantBits =
      ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO |
      ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO |
      NODE_DESCENDANTS_NEED_FRAMES;

  /**
   * Notes that something in the given subtree of this element needs dirtying,
   * and that all the relevant dirty bits have already been propagated up to the
   * element.
   *
   * This is important because `NoteDirtyForServo` uses the dirty bits to reason
   * about the shape of the tree, so we can't just call into there.
   */
  void NoteDirtySubtreeForServo();

  void NoteDirtyForServo();
  void NoteAnimationOnlyDirtyForServo();
  void NoteDescendantsNeedFramesForServo();

  bool HasDirtyDescendantsForServo() const {
    return HasFlag(ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO);
  }

  void SetHasDirtyDescendantsForServo() {
    SetFlags(ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO);
  }

  void UnsetHasDirtyDescendantsForServo() {
    UnsetFlags(ELEMENT_HAS_DIRTY_DESCENDANTS_FOR_SERVO);
  }

  bool HasAnimationOnlyDirtyDescendantsForServo() const {
    return HasFlag(ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO);
  }

  void SetHasAnimationOnlyDirtyDescendantsForServo() {
    SetFlags(ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO);
  }

  void UnsetHasAnimationOnlyDirtyDescendantsForServo() {
    UnsetFlags(ELEMENT_HAS_ANIMATION_ONLY_DIRTY_DESCENDANTS_FOR_SERVO);
  }

  bool HasServoData() const { return !!mServoData.Get(); }

  void ClearServoData() { ClearServoData(GetComposedDoc()); }
  void ClearServoData(Document* aDocument);

  /**
   * Gets the custom element data used by web components custom element.
   * Custom element data is created at the first attempt to enqueue a callback.
   *
   * @return The custom element data or null if none.
   */
  inline CustomElementData* GetCustomElementData() const {
    if (!HasCustomElementData()) {
      return nullptr;
    }

    const nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
    return slots ? slots->mCustomElementData.get() : nullptr;
  }

  /**
   * Sets the custom element data, ownership of the
   * callback data is taken by this element.
   *
   * @param aData The custom element data.
   */
  void SetCustomElementData(CustomElementData* aData);

  /**
   * Gets the custom element definition used by web components custom element.
   *
   * @return The custom element definition or null if element is not a custom
   *         element or custom element is not defined yet.
   */
  CustomElementDefinition* GetCustomElementDefinition() const;

  /**
   * Sets the custom element definition, called when custom element is created
   * or upgraded.
   *
   * @param aDefinition The custom element definition.
   */
  void SetCustomElementDefinition(CustomElementDefinition* aDefinition);

  void SetDefined(bool aSet) {
    if (aSet) {
      AddStates(NS_EVENT_STATE_DEFINED);
    } else {
      RemoveStates(NS_EVENT_STATE_DEFINED);
    }
  }

  // AccessibilityRole
  REFLECT_NULLABLE_DOMSTRING_ATTR(Role, role)

  // AriaAttributes
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaAtomic, aria_atomic)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaAutoComplete, aria_autocomplete)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaBusy, aria_busy)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaChecked, aria_checked)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaColCount, aria_colcount)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaColIndex, aria_colindex)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaColIndexText, aria_colindextext)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaColSpan, aria_colspan)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaCurrent, aria_current)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaDescription, aria_description)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaDisabled, aria_disabled)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaExpanded, aria_expanded)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaHasPopup, aria_haspopup)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaHidden, aria_hidden)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaInvalid, aria_invalid)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaKeyShortcuts, aria_keyshortcuts)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaLabel, aria_label)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaLevel, aria_level)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaLive, aria_live)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaModal, aria_modal)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaMultiLine, aria_multiline)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaMultiSelectable, aria_multiselectable)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaOrientation, aria_orientation)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaPlaceholder, aria_placeholder)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaPosInSet, aria_posinset)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaPressed, aria_pressed)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaReadOnly, aria_readonly)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRelevant, aria_relevant)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRequired, aria_required)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRoleDescription, aria_roledescription)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRowCount, aria_rowcount)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRowIndex, aria_rowindex)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRowIndexText, aria_rowindextext)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaRowSpan, aria_rowspan)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaSelected, aria_selected)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaSetSize, aria_setsize)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaSort, aria_sort)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaValueMax, aria_valuemax)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaValueMin, aria_valuemin)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaValueNow, aria_valuenow)
  REFLECT_NULLABLE_DOMSTRING_ATTR(AriaValueText, aria_valuetext)

 protected:
  /**
   * Method to get the _intrinsic_ content state of this element.  This is the
   * state that is independent of the element's presentation.  To get the full
   * content state, use State().  See mozilla/EventStates.h for
   * the possible bits that could be set here.
   */
  virtual EventStates IntrinsicState() const;

  /**
   * Method to add state bits.  This should be called from subclass
   * constructors to set up our event state correctly at construction
   * time and other places where we don't want to notify a state
   * change.
   */
  void AddStatesSilently(EventStates aStates) { mState |= aStates; }

  /**
   * Method to remove state bits.  This should be called from subclass
   * constructors to set up our event state correctly at construction
   * time and other places where we don't want to notify a state
   * change.
   */
  void RemoveStatesSilently(EventStates aStates) { mState &= ~aStates; }

  already_AddRefed<ShadowRoot> AttachShadowInternal(ShadowRootMode,
                                                    ErrorResult& aError);

  MOZ_CAN_RUN_SCRIPT
  nsIScrollableFrame* GetScrollFrame(nsIFrame** aStyledFrame = nullptr,
                                     FlushType aFlushType = FlushType::Layout);

 private:
  // Need to allow the ESM, nsGlobalWindow, and the focus manager to
  // set our state
  friend class mozilla::EventStateManager;
  friend class ::nsGlobalWindowInner;
  friend class ::nsGlobalWindowOuter;
  friend class ::nsFocusManager;

  // Allow CusomtElementRegistry to call AddStates.
  friend class CustomElementRegistry;

  // Also need to allow Link to call UpdateLinkState.
  friend class Link;

  void NotifyStateChange(EventStates aStates);

  void NotifyStyleStateChange(EventStates aStates);

  // Style state computed from element's state and style locks.
  EventStates StyleStateFromLocks() const;

 protected:
  // Methods for the ESM, nsGlobalWindow and focus manager to manage state bits.
  // These will handle setting up script blockers when they notify, so no need
  // to do it in the callers unless desired.  States passed here must only be
  // those in EXTERNALLY_MANAGED_STATES.
  virtual void AddStates(EventStates aStates) {
    MOZ_ASSERT(!aStates.HasAtLeastOneOfStates(INTRINSIC_STATES),
               "Should only be adding externally-managed states here");
    AddStatesSilently(aStates);
    NotifyStateChange(aStates);
  }
  virtual void RemoveStates(EventStates aStates) {
    MOZ_ASSERT(!aStates.HasAtLeastOneOfStates(INTRINSIC_STATES),
               "Should only be removing externally-managed states here");
    RemoveStatesSilently(aStates);
    NotifyStateChange(aStates);
  }
  virtual void ToggleStates(EventStates aStates, bool aNotify) {
    MOZ_ASSERT(!aStates.HasAtLeastOneOfStates(INTRINSIC_STATES),
               "Should only be removing externally-managed states here");
    mState ^= aStates;
    if (aNotify) {
      NotifyStateChange(aStates);
    }
  }

 public:
  // Public methods to manage state bits in MANUALLY_MANAGED_STATES.
  void AddManuallyManagedStates(EventStates aStates) {
    MOZ_ASSERT(MANUALLY_MANAGED_STATES.HasAllStates(aStates),
               "Should only be adding manually-managed states here");
    AddStates(aStates);
  }
  void RemoveManuallyManagedStates(EventStates aStates) {
    MOZ_ASSERT(MANUALLY_MANAGED_STATES.HasAllStates(aStates),
               "Should only be removing manually-managed states here");
    RemoveStates(aStates);
  }

  void UpdateEditableState(bool aNotify) override;

  nsresult BindToTree(BindContext&, nsINode& aParent) override;

  void UnbindFromTree(bool aNullParent = true) override;

  /**
   * Normalizes an attribute name and returns it as a nodeinfo if an attribute
   * with that name exists. This method is intended for character case
   * conversion if the content object is case insensitive (e.g. HTML). Returns
   * the nodeinfo of the attribute with the specified name if one exists or
   * null otherwise.
   *
   * @param aStr the unparsed attribute string
   * @return the node info. May be nullptr.
   */
  already_AddRefed<mozilla::dom::NodeInfo> GetExistingAttrNameFromQName(
      const nsAString& aStr) const;

  /**
   * Helper for SetAttr/SetParsedAttr. This method will return true if aNotify
   * is true or there are mutation listeners that must be triggered, the
   * attribute is currently set, and the new value that is about to be set is
   * different to the current value. As a perf optimization the new and old
   * values will not actually be compared if we aren't notifying and we don't
   * have mutation listeners (in which case it's cheap to just return false
   * and let the caller go ahead and set the value).
   * @param aOldValue [out] Set to the old value of the attribute, but only if
   *   there are event listeners. If set, the type of aOldValue will be either
   *   nsAttrValue::eString or nsAttrValue::eAtom.
   * @param aModType [out] Set to MutationEvent_Binding::MODIFICATION or to
   *   MutationEvent_Binding::ADDITION, but only if this helper returns true
   * @param aHasListeners [out] Set to true if there are mutation event
   *   listeners listening for NS_EVENT_BITS_MUTATION_ATTRMODIFIED
   * @param aOldValueSet [out] Indicates whether an old attribute value has been
   *   stored in aOldValue. The bool will be set to true if a value was stored.
   */
  bool MaybeCheckSameAttrVal(int32_t aNamespaceID, const nsAtom* aName,
                             const nsAtom* aPrefix,
                             const nsAttrValueOrString& aValue, bool aNotify,
                             nsAttrValue& aOldValue, uint8_t* aModType,
                             bool* aHasListeners, bool* aOldValueSet);

  /**
   * Notifies mutation listeners if aNotify is true, there are mutation
   * listeners, and the attribute value is changing.
   *
   * @param aNamespaceID The namespace of the attribute
   * @param aName The local name of the attribute
   * @param aPrefix The prefix of the attribute
   * @param aValue The value that the attribute is being changed to
   * @param aNotify If true, mutation listeners will be notified if they exist
   *   and the attribute value is changing
   * @param aOldValue [out] Set to the old value of the attribute, but only if
   *   there are event listeners. If set, the type of aOldValue will be either
   *   nsAttrValue::eString or nsAttrValue::eAtom.
   * @param aModType [out] Set to MutationEvent_Binding::MODIFICATION or to
   *   MutationEvent_Binding::ADDITION, but only if this helper returns true
   * @param aHasListeners [out] Set to true if there are mutation event
   *   listeners listening for NS_EVENT_BITS_MUTATION_ATTRMODIFIED
   * @param aOldValueSet [out] Indicates whether an old attribute value has been
   *   stored in aOldValue. The bool will be set to true if a value was stored.
   */
  bool OnlyNotifySameValueSet(int32_t aNamespaceID, nsAtom* aName,
                              nsAtom* aPrefix,
                              const nsAttrValueOrString& aValue, bool aNotify,
                              nsAttrValue& aOldValue, uint8_t* aModType,
                              bool* aHasListeners, bool* aOldValueSet);

  /**
   * Sets the class attribute to a value that contains no whitespace.
   * Assumes that we are not notifying and that the attribute hasn't been
   * set previously.
   */
  nsresult SetSingleClassFromParser(nsAtom* aSingleClassName);

  // aParsedValue receives the old value of the attribute. That's useful if
  // either the input or output value of aParsedValue is StoresOwnData.
  nsresult SetParsedAttr(int32_t aNameSpaceID, nsAtom* aName, nsAtom* aPrefix,
                         nsAttrValue& aParsedValue, bool aNotify);
  /**
   * Get the current value of the attribute. This returns a form that is
   * suitable for passing back into SetAttr.
   *
   * @param aNameSpaceID the namespace of the attr (defaults to
                         kNameSpaceID_None in the overload that omits this arg)
   * @param aName the name of the attr
   * @param aResult the value (may legitimately be the empty string) [OUT]
   * @returns true if the attribute was set (even when set to empty string)
   *          false when not set.
   * GetAttr is not inlined on purpose, to keep down codesize from all the
   * inlined nsAttrValue bits for C++ callers.
   */
  bool GetAttr(int32_t aNameSpaceID, const nsAtom* aName,
               nsAString& aResult) const;

  bool GetAttr(const nsAtom* aName, nsAString& aResult) const {
    return GetAttr(kNameSpaceID_None, aName, aResult);
  }

  /**
   * Determine if an attribute has been set (empty string or otherwise).
   *
   * @param aNameSpaceId the namespace id of the attribute (defaults to
                         kNameSpaceID_None in the overload that omits this arg)
   * @param aAttr the attribute name
   * @return whether an attribute exists
   */
  inline bool HasAttr(int32_t aNameSpaceID, const nsAtom* aName) const;

  bool HasAttr(const nsAtom* aAttr) const {
    return HasAttr(kNameSpaceID_None, aAttr);
  }

  /**
   * Determine if an attribute has been set to a non-empty string value. If the
   * attribute is not set at all, this will return false.
   *
   * @param aNameSpaceId the namespace id of the attribute (defaults to
   *                     kNameSpaceID_None in the overload that omits this arg)
   * @param aAttr the attribute name
   */
  inline bool HasNonEmptyAttr(int32_t aNameSpaceID, const nsAtom* aName) const;

  bool HasNonEmptyAttr(const nsAtom* aAttr) const {
    return HasNonEmptyAttr(kNameSpaceID_None, aAttr);
  }

  /**
   * Test whether this Element's given attribute has the given value.  If the
   * attribute is not set at all, this will return false.
   *
   * @param aNameSpaceID The namespace ID of the attribute.  Must not
   *                     be kNameSpaceID_Unknown.
   * @param aName The name atom of the attribute.  Must not be null.
   * @param aValue The value to compare to.
   * @param aCaseSensitive Whether to do a case-sensitive compare on the value.
   */
  inline bool AttrValueIs(int32_t aNameSpaceID, const nsAtom* aName,
                          const nsAString& aValue,
                          nsCaseTreatment aCaseSensitive) const;

  /**
   * Test whether this Element's given attribute has the given value.  If the
   * attribute is not set at all, this will return false.
   *
   * @param aNameSpaceID The namespace ID of the attribute.  Must not
   *                     be kNameSpaceID_Unknown.
   * @param aName The name atom of the attribute.  Must not be null.
   * @param aValue The value to compare to.  Must not be null.
   * @param aCaseSensitive Whether to do a case-sensitive compare on the value.
   */
  bool AttrValueIs(int32_t aNameSpaceID, const nsAtom* aName,
                   const nsAtom* aValue, nsCaseTreatment aCaseSensitive) const;

  enum { ATTR_MISSING = -1, ATTR_VALUE_NO_MATCH = -2 };
  /**
   * Check whether this Element's given attribute has one of a given list of
   * values. If there is a match, we return the index in the list of the first
   * matching value. If there was no attribute at all, then we return
   * ATTR_MISSING. If there was an attribute but it didn't match, we return
   * ATTR_VALUE_NO_MATCH. A non-negative result always indicates a match.
   *
   * @param aNameSpaceID The namespace ID of the attribute.  Must not
   *                     be kNameSpaceID_Unknown.
   * @param aName The name atom of the attribute.  Must not be null.
   * @param aValues a nullptr-terminated array of pointers to atom values to
   * test against.
   * @param aCaseSensitive Whether to do a case-sensitive compare on the values.
   * @return ATTR_MISSING, ATTR_VALUE_NO_MATCH or the non-negative index
   * indicating the first value of aValues that matched
   */
  typedef nsStaticAtom* const AttrValuesArray;
  int32_t FindAttrValueIn(int32_t aNameSpaceID, const nsAtom* aName,
                          AttrValuesArray* aValues,
                          nsCaseTreatment aCaseSensitive) const;

  /**
   * Set attribute values. All attribute values are assumed to have a
   * canonical string representation that can be used for these
   * methods. The SetAttr method is assumed to perform a translation
   * of the canonical form into the underlying content specific
   * form.
   *
   * @param aNameSpaceID the namespace of the attribute
   * @param aName the name of the attribute
   * @param aValue the value to set
   * @param aNotify specifies how whether or not the document should be
   *        notified of the attribute change.
   */
  nsresult SetAttr(int32_t aNameSpaceID, nsAtom* aName, const nsAString& aValue,
                   bool aNotify) {
    return SetAttr(aNameSpaceID, aName, nullptr, aValue, aNotify);
  }
  nsresult SetAttr(int32_t aNameSpaceID, nsAtom* aName, nsAtom* aPrefix,
                   const nsAString& aValue, bool aNotify) {
    return SetAttr(aNameSpaceID, aName, aPrefix, aValue, nullptr, aNotify);
  }
  nsresult SetAttr(int32_t aNameSpaceID, nsAtom* aName, const nsAString& aValue,
                   nsIPrincipal* aTriggeringPrincipal, bool aNotify) {
    return SetAttr(aNameSpaceID, aName, nullptr, aValue, aTriggeringPrincipal,
                   aNotify);
  }

  /**
   * Set attribute values. All attribute values are assumed to have a
   * canonical String representation that can be used for these
   * methods. The SetAttr method is assumed to perform a translation
   * of the canonical form into the underlying content specific
   * form.
   *
   * @param aNameSpaceID the namespace of the attribute
   * @param aName the name of the attribute
   * @param aPrefix the prefix of the attribute
   * @param aValue the value to set
   * @param aMaybeScriptedPrincipal the principal of the scripted caller
   * responsible for setting the attribute, or null if no scripted caller can be
   *        determined. A null value here does not guarantee that there is no
   *        scripted caller, but a non-null value does guarantee that a scripted
   *        caller with the given principal is directly responsible for the
   *        attribute change.
   * @param aNotify specifies how whether or not the document should be
   *        notified of the attribute change.
   */
  nsresult SetAttr(int32_t aNameSpaceID, nsAtom* aName, nsAtom* aPrefix,
                   const nsAString& aValue,
                   nsIPrincipal* aMaybeScriptedPrincipal, bool aNotify);

  /**
   * Remove an attribute so that it is no longer explicitly specified.
   *
   * @param aNameSpaceID the namespace id of the attribute
   * @param aAttr the name of the attribute to unset
   * @param aNotify specifies whether or not the document should be
   * notified of the attribute change
   */
  nsresult UnsetAttr(int32_t aNameSpaceID, nsAtom* aAttribute, bool aNotify);

  /**
   * Get the namespace / name / prefix of a given attribute.
   *
   * @param   aIndex the index of the attribute name
   * @returns The name at the given index, or null if the index is
   *          out-of-bounds.
   * @note    The document returned by NodeInfo()->GetDocument() (if one is
   *          present) is *not* necessarily the owner document of the element.
   * @note    The pointer returned by this function is only valid until the
   *          next call of either GetAttrNameAt or SetAttr on the element.
   */
  const nsAttrName* GetAttrNameAt(uint32_t aIndex) const {
    return mAttrs.GetSafeAttrNameAt(aIndex);
  }

  /**
   * Same as above, but does not do out-of-bounds checks!
   */
  const nsAttrName* GetUnsafeAttrNameAt(uint32_t aIndex) const {
    return mAttrs.AttrNameAt(aIndex);
  }

  /**
   * Gets the attribute info (name and value) for this element at a given index.
   */
  BorrowedAttrInfo GetAttrInfoAt(uint32_t aIndex) const {
    if (aIndex >= mAttrs.AttrCount()) {
      return BorrowedAttrInfo(nullptr, nullptr);
    }

    return mAttrs.AttrInfoAt(aIndex);
  }

  /**
   * Get the number of all specified attributes.
   *
   * @return the number of attributes
   */
  uint32_t GetAttrCount() const { return mAttrs.AttrCount(); }

  virtual bool IsNodeOfType(uint32_t aFlags) const override;

  /**
   * Get the class list of this element (this corresponds to the value of the
   * class attribute).  This may be null if there are no classes, but that's not
   * guaranteed (e.g. we could have class="").
   */
  const nsAttrValue* GetClasses() const {
    if (!MayHaveClass()) {
      return nullptr;
    }

    if (IsSVGElement()) {
      if (const nsAttrValue* value = GetSVGAnimatedClass()) {
        return value;
      }
    }

    return GetParsedAttr(nsGkAtoms::_class);
  }

#ifdef DEBUG
  virtual void List(FILE* out = stdout, int32_t aIndent = 0) const override {
    List(out, aIndent, EmptyCString());
  }
  virtual void DumpContent(FILE* out, int32_t aIndent,
                           bool aDumpAll) const override;
  void List(FILE* out, int32_t aIndent, const nsCString& aPrefix) const;
  void ListAttributes(FILE* out) const;
#endif

  /**
   * Append to aOutDescription a short (preferably one line) string
   * describing the element.
   */
  void Describe(nsAString& aOutDescription) const;

  /*
   * Attribute Mapping Helpers
   */
  struct MappedAttributeEntry {
    const nsStaticAtom* const attribute;
  };

  /**
   * A common method where you can just pass in a list of maps to check
   * for attribute dependence. Most implementations of
   * IsAttributeMapped should use this function as a default
   * handler.
   */
  template <size_t N>
  static bool FindAttributeDependence(
      const nsAtom* aAttribute, const MappedAttributeEntry* const (&aMaps)[N]) {
    return FindAttributeDependence(aAttribute, aMaps, N);
  }

  static nsStaticAtom* const* HTMLSVGPropertiesToTraverseAndUnlink();

 private:
  void DescribeAttribute(uint32_t index, nsAString& aOutDescription) const;

  static bool FindAttributeDependence(const nsAtom* aAttribute,
                                      const MappedAttributeEntry* const aMaps[],
                                      uint32_t aMapCount);

 protected:
  inline bool GetAttr(int32_t aNameSpaceID, const nsAtom* aName,
                      DOMString& aResult) const {
    NS_ASSERTION(nullptr != aName, "must have attribute name");
    NS_ASSERTION(aNameSpaceID != kNameSpaceID_Unknown,
                 "must have a real namespace ID!");
    MOZ_ASSERT(aResult.IsEmpty(), "Should have empty string coming in");
    const nsAttrValue* val = mAttrs.GetAttr(aName, aNameSpaceID);
    if (val) {
      val->ToString(aResult);
      return true;
    }
    // else DOMString comes pre-emptied.
    return false;
  }

 public:
  bool HasAttrs() const { return mAttrs.HasAttrs(); }

  inline bool GetAttr(const nsAString& aName, DOMString& aResult) const {
    MOZ_ASSERT(aResult.IsEmpty(), "Should have empty string coming in");
    const nsAttrValue* val = mAttrs.GetAttr(aName);
    if (val) {
      val->ToString(aResult);
      return true;
    }
    // else DOMString comes pre-emptied.
    return false;
  }

  void GetTagName(nsAString& aTagName) const { aTagName = NodeName(); }
  void GetId(nsAString& aId) const {
    GetAttr(kNameSpaceID_None, nsGkAtoms::id, aId);
  }
  void GetId(DOMString& aId) const {
    GetAttr(kNameSpaceID_None, nsGkAtoms::id, aId);
  }
  void SetId(const nsAString& aId) {
    SetAttr(kNameSpaceID_None, nsGkAtoms::id, aId, true);
  }
  void GetClassName(nsAString& aClassName) {
    GetAttr(kNameSpaceID_None, nsGkAtoms::_class, aClassName);
  }
  void GetClassName(DOMString& aClassName) {
    GetAttr(kNameSpaceID_None, nsGkAtoms::_class, aClassName);
  }
  void SetClassName(const nsAString& aClassName) {
    SetAttr(kNameSpaceID_None, nsGkAtoms::_class, aClassName, true);
  }

  nsDOMTokenList* ClassList();
  nsDOMTokenList* Part();

  nsDOMAttributeMap* Attributes() {
    nsDOMSlots* slots = DOMSlots();
    if (!slots->mAttributeMap) {
      slots->mAttributeMap = new nsDOMAttributeMap(this);
    }

    return slots->mAttributeMap;
  }

  void GetAttributeNames(nsTArray<nsString>& aResult);

  void GetAttribute(const nsAString& aName, nsAString& aReturn) {
    DOMString str;
    GetAttribute(aName, str);
    str.ToString(aReturn);
  }

  void GetAttribute(const nsAString& aName, DOMString& aReturn);
  void GetAttributeNS(const nsAString& aNamespaceURI,
                      const nsAString& aLocalName, nsAString& aReturn);
  bool ToggleAttribute(const nsAString& aName, const Optional<bool>& aForce,
                       nsIPrincipal* aTriggeringPrincipal, ErrorResult& aError);
  void SetAttribute(const nsAString& aName, const nsAString& aValue,
                    nsIPrincipal* aTriggeringPrincipal, ErrorResult& aError);
  void SetAttributeNS(const nsAString& aNamespaceURI,
                      const nsAString& aLocalName, const nsAString& aValue,
                      nsIPrincipal* aTriggeringPrincipal, ErrorResult& aError);
  void SetAttribute(const nsAString& aName, const nsAString& aValue,
                    ErrorResult& aError) {
    SetAttribute(aName, aValue, nullptr, aError);
  }
  void SetAttributeDevtools(const nsAString& aName, const nsAString& aValue,
                            ErrorResult& aError);
  void SetAttributeDevtoolsNS(const nsAString& aNamespaceURI,
                              const nsAString& aLocalName,
                              const nsAString& aValue, ErrorResult& aError);

  void RemoveAttribute(const nsAString& aName, ErrorResult& aError);
  void RemoveAttributeNS(const nsAString& aNamespaceURI,
                         const nsAString& aLocalName, ErrorResult& aError);
  bool HasAttribute(const nsAString& aName) const {
    return InternalGetAttrNameFromQName(aName) != nullptr;
  }
  bool HasAttributeNS(const nsAString& aNamespaceURI,
                      const nsAString& aLocalName) const;
  bool HasAttributes() const { return HasAttrs(); }
  Element* Closest(const nsAString& aSelector, ErrorResult& aResult);
  bool Matches(const nsAString& aSelector, ErrorResult& aError);
  already_AddRefed<nsIHTMLCollection> GetElementsByTagName(
      const nsAString& aQualifiedName);
  already_AddRefed<nsIHTMLCollection> GetElementsByTagNameNS(
      const nsAString& aNamespaceURI, const nsAString& aLocalName,
      ErrorResult& aError);
  already_AddRefed<nsIHTMLCollection> GetElementsByClassName(
      const nsAString& aClassNames);

  PseudoStyleType GetPseudoElementType() const {
    nsresult rv = NS_OK;
    auto raw = GetProperty(nsGkAtoms::pseudoProperty, &rv);
    if (rv == NS_PROPTABLE_PROP_NOT_THERE) {
      return PseudoStyleType::NotPseudo;
    }
    return PseudoStyleType(reinterpret_cast<uintptr_t>(raw));
  }

  void SetPseudoElementType(PseudoStyleType aPseudo) {
    static_assert(sizeof(PseudoStyleType) <= sizeof(uintptr_t),
                  "Need to be able to store this in a void*");
    MOZ_ASSERT(PseudoStyle::IsPseudoElement(aPseudo));
    SetProperty(nsGkAtoms::pseudoProperty, reinterpret_cast<void*>(aPseudo));
  }

  /**
   * Return an array of all elements in the subtree rooted at this
   * element that have grid container frames. This does not include
   * pseudo-elements.
   */
  void GetElementsWithGrid(nsTArray<RefPtr<Element>>& aElements);

 private:
  /**
   * Implement the algorithm specified at
   * https://dom.spec.whatwg.org/#insert-adjacent for both
   * |insertAdjacentElement()| and |insertAdjacentText()| APIs.
   */
  nsINode* InsertAdjacent(const nsAString& aWhere, nsINode* aNode,
                          ErrorResult& aError);

 public:
  Element* InsertAdjacentElement(const nsAString& aWhere, Element& aElement,
                                 ErrorResult& aError);

  void InsertAdjacentText(const nsAString& aWhere, const nsAString& aData,
                          ErrorResult& aError);

  void SetPointerCapture(int32_t aPointerId, ErrorResult& aError) {
    bool activeState = false;
    if (nsContentUtils::ShouldResistFingerprinting(GetComposedDoc()) &&
        aPointerId != PointerEventHandler::GetSpoofedPointerIdForRFP()) {
      aError.Throw(NS_ERROR_DOM_INVALID_POINTER_ERR);
      return;
    }
    if (!PointerEventHandler::GetPointerInfo(aPointerId, activeState)) {
      aError.Throw(NS_ERROR_DOM_INVALID_POINTER_ERR);
      return;
    }
    if (!IsInComposedDoc()) {
      aError.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
      return;
    }
    if (OwnerDoc()->GetPointerLockElement()) {
      // Throw an exception 'InvalidStateError' while the page has a locked
      // element.
      aError.Throw(NS_ERROR_DOM_INVALID_STATE_ERR);
      return;
    }
    if (!activeState) {
      return;
    }
    PointerEventHandler::SetPointerCaptureById(aPointerId, this);
  }
  void ReleasePointerCapture(int32_t aPointerId, ErrorResult& aError) {
    bool activeState = false;
    if (nsContentUtils::ShouldResistFingerprinting(GetComposedDoc()) &&
        aPointerId != PointerEventHandler::GetSpoofedPointerIdForRFP()) {
      aError.Throw(NS_ERROR_DOM_INVALID_POINTER_ERR);
      return;
    }
    if (!PointerEventHandler::GetPointerInfo(aPointerId, activeState)) {
      aError.Throw(NS_ERROR_DOM_INVALID_POINTER_ERR);
      return;
    }
    if (HasPointerCapture(aPointerId)) {
      PointerEventHandler::ReleasePointerCaptureById(aPointerId);
    }
  }
  bool HasPointerCapture(long aPointerId) {
    PointerCaptureInfo* pointerCaptureInfo =
        PointerEventHandler::GetPointerCaptureInfo(aPointerId);
    if (pointerCaptureInfo && pointerCaptureInfo->mPendingContent == this) {
      return true;
    }
    return false;
  }
  void SetCapture(bool aRetargetToElement);

  void SetCaptureAlways(bool aRetargetToElement);

  void ReleaseCapture();

  already_AddRefed<Promise> RequestFullscreen(CallerType, ErrorResult&);
  void RequestPointerLock(CallerType aCallerType);
  Attr* GetAttributeNode(const nsAString& aName);
  already_AddRefed<Attr> SetAttributeNode(Attr& aNewAttr, ErrorResult& aError);
  already_AddRefed<Attr> RemoveAttributeNode(Attr& aOldAttr,
                                             ErrorResult& aError);
  Attr* GetAttributeNodeNS(const nsAString& aNamespaceURI,
                           const nsAString& aLocalName);
  already_AddRefed<Attr> SetAttributeNodeNS(Attr& aNewAttr,
                                            ErrorResult& aError);

  MOZ_CAN_RUN_SCRIPT already_AddRefed<DOMRectList> GetClientRects();
  MOZ_CAN_RUN_SCRIPT already_AddRefed<DOMRect> GetBoundingClientRect();

  // Shadow DOM v1
  already_AddRefed<ShadowRoot> AttachShadow(const ShadowRootInit& aInit,
                                            ErrorResult& aError);
  bool CanAttachShadowDOM() const;

  already_AddRefed<ShadowRoot> AttachShadowWithoutNameChecks(
      ShadowRootMode aMode);

  // Attach UA Shadow Root if it is not attached.
  void AttachAndSetUAShadowRoot();

  // Dispatch an event to UAWidgetsChild, triggering construction
  // or onchange callback on the existing widget.
  void NotifyUAWidgetSetupOrChange();

  enum class UnattachShadowRoot {
    No,
    Yes,
  };

  // Dispatch an event to UAWidgetsChild, triggering UA Widget destruction.
  // and optionally remove the shadow root.
  void NotifyUAWidgetTeardown(UnattachShadowRoot = UnattachShadowRoot::Yes);

  void UnattachShadow();

  ShadowRoot* GetShadowRootByMode() const;
  void SetSlot(const nsAString& aName, ErrorResult& aError);
  void GetSlot(nsAString& aName);

  ShadowRoot* GetShadowRoot() const {
    const nsExtendedDOMSlots* slots = GetExistingExtendedDOMSlots();
    return slots ? slots->mShadowRoot.get() : nullptr;
  }

 private:
  MOZ_CAN_RUN_SCRIPT void ScrollIntoView(const ScrollIntoViewOptions& aOptions);

 public:
  MOZ_CAN_RUN_SCRIPT
  void ScrollIntoView(const BooleanOrScrollIntoViewOptions& aObject);
  MOZ_CAN_RUN_SCRIPT void Scroll(double aXScroll, double aYScroll);
  MOZ_CAN_RUN_SCRIPT void Scroll(const ScrollToOptions& aOptions);
  MOZ_CAN_RUN_SCRIPT void ScrollTo(double aXScroll, double aYScroll);
  MOZ_CAN_RUN_SCRIPT void ScrollTo(const ScrollToOptions& aOptions);
  MOZ_CAN_RUN_SCRIPT void ScrollBy(double aXScrollDif, double aYScrollDif);
  MOZ_CAN_RUN_SCRIPT void ScrollBy(const ScrollToOptions& aOptions);
  MOZ_CAN_RUN_SCRIPT int32_t ScrollTop();
  MOZ_CAN_RUN_SCRIPT void SetScrollTop(int32_t aScrollTop);
  MOZ_CAN_RUN_SCRIPT int32_t ScrollLeft();
  MOZ_CAN_RUN_SCRIPT void SetScrollLeft(int32_t aScrollLeft);
  MOZ_CAN_RUN_SCRIPT int32_t ScrollWidth();
  MOZ_CAN_RUN_SCRIPT int32_t ScrollHeight();
  MOZ_CAN_RUN_SCRIPT void MozScrollSnap();
  MOZ_CAN_RUN_SCRIPT int32_t ClientTop() {
    return CSSPixel::FromAppUnits(GetClientAreaRect().y).Rounded();
  }
  MOZ_CAN_RUN_SCRIPT int32_t ClientLeft() {
    return CSSPixel::FromAppUnits(GetClientAreaRect().x).Rounded();
  }
  MOZ_CAN_RUN_SCRIPT int32_t ClientWidth() {
    return CSSPixel::FromAppUnits(GetClientAreaRect().Width()).Rounded();
  }
  MOZ_CAN_RUN_SCRIPT int32_t ClientHeight() {
    return CSSPixel::FromAppUnits(GetClientAreaRect().Height()).Rounded();
  }
  MOZ_CAN_RUN_SCRIPT int32_t ScrollTopMin() {
    nsIScrollableFrame* sf = GetScrollFrame();
    if (!sf) {
      return 0;
    }
    return CSSPixel::FromAppUnits(sf->GetScrollRange().y).Rounded();
  }
  MOZ_CAN_RUN_SCRIPT int32_t ScrollTopMax() {
    nsIScrollableFrame* sf = GetScrollFrame();
    if (!sf) {
      return 0;
    }
    return CSSPixel::FromAppUnits(sf->GetScrollRange().YMost()).Rounded();
  }
  MOZ_CAN_RUN_SCRIPT int32_t ScrollLeftMin() {
    nsIScrollableFrame* sf = GetScrollFrame();
    if (!sf) {
      return 0;
    }
    return CSSPixel::FromAppUnits(sf->GetScrollRange().x).Rounded();
  }
  MOZ_CAN_RUN_SCRIPT int32_t ScrollLeftMax() {
    nsIScrollableFrame* sf = GetScrollFrame();
    if (!sf) {
      return 0;
    }
    return CSSPixel::FromAppUnits(sf->GetScrollRange().XMost()).Rounded();
  }

  MOZ_CAN_RUN_SCRIPT double ClientHeightDouble() {
    return CSSPixel::FromAppUnits(GetClientAreaRect().Height());
  }

  MOZ_CAN_RUN_SCRIPT double ClientWidthDouble() {
    return CSSPixel::FromAppUnits(GetClientAreaRect().Width());
  }

  // This function will return the block size of first line box, no matter if
  // the box is 'block' or 'inline'. The return unit is pixel. If the element
  // can't get a primary frame, we will return be zero.
  double FirstLineBoxBSize() const;

  already_AddRefed<Flex> GetAsFlexContainer();
  void GetGridFragments(nsTArray<RefPtr<Grid>>& aResult);

  bool HasGridFragments();

  already_AddRefed<DOMMatrixReadOnly> GetTransformToAncestor(
      Element& aAncestor);
  already_AddRefed<DOMMatrixReadOnly> GetTransformToParent();
  already_AddRefed<DOMMatrixReadOnly> GetTransformToViewport();

  already_AddRefed<Animation> Animate(
      JSContext* aContext, JS::Handle<JSObject*> aKeyframes,
      const UnrestrictedDoubleOrKeyframeAnimationOptions& aOptions,
      ErrorResult& aError);

  MOZ_CAN_RUN_SCRIPT
  void GetAnimations(const GetAnimationsOptions& aOptions,
                     nsTArray<RefPtr<Animation>>& aAnimations);

  void GetAnimationsWithoutFlush(const GetAnimationsOptions& aOptions,
                                 nsTArray<RefPtr<Animation>>& aAnimations);

  static void GetAnimationsUnsorted(Element* aElement,
                                    PseudoStyleType aPseudoType,
                                    nsTArray<RefPtr<Animation>>& aAnimations);

  virtual void GetInnerHTML(nsAString& aInnerHTML, OOMReporter& aError);
  virtual void SetInnerHTML(const nsAString& aInnerHTML,
                            nsIPrincipal* aSubjectPrincipal,
                            ErrorResult& aError);
  void GetOuterHTML(nsAString& aOuterHTML);
  void SetOuterHTML(const nsAString& aOuterHTML, ErrorResult& aError);
  void InsertAdjacentHTML(const nsAString& aPosition, const nsAString& aText,
                          ErrorResult& aError);

  //----------------------------------------

  /**
   * Add a script event listener with the given event handler name
   * (like onclick) and with the value as JS
   * @param aEventName the event listener name
   * @param aValue the JS to attach
   * @param aDefer indicates if deferred execution is allowed
   */
  void SetEventHandler(nsAtom* aEventName, const nsAString& aValue,
                       bool aDefer = true);

  /**
   * Do whatever needs to be done when the mouse leaves a link
   */
  nsresult LeaveLink(nsPresContext* aPresContext);

  static bool ShouldBlur(nsIContent* aContent);

  /**
   * Method to create and dispatch a left-click event loosely based on
   * aSourceEvent. If aFullDispatch is true, the event will be dispatched
   * through the full dispatching of the presshell of the aPresContext; if it's
   * false the event will be dispatched only as a DOM event.
   * If aPresContext is nullptr, this does nothing.
   *
   * @param aFlags      Extra flags for the dispatching event.  The true flags
   *                    will be respected.
   */
  MOZ_CAN_RUN_SCRIPT
  static nsresult DispatchClickEvent(nsPresContext* aPresContext,
                                     WidgetInputEvent* aSourceEvent,
                                     nsIContent* aTarget, bool aFullDispatch,
                                     const EventFlags* aFlags,
                                     nsEventStatus* aStatus);

  /**
   * Method to dispatch aEvent to aTarget. If aFullDispatch is true, the event
   * will be dispatched through the full dispatching of the presshell of the
   * aPresContext; if it's false the event will be dispatched only as a DOM
   * event.
   * If aPresContext is nullptr, this does nothing.
   */
  using nsIContent::DispatchEvent;
  MOZ_CAN_RUN_SCRIPT
  static nsresult DispatchEvent(nsPresContext* aPresContext,
                                WidgetEvent* aEvent, nsIContent* aTarget,
                                bool aFullDispatch, nsEventStatus* aStatus);

  bool IsDisplayContents() const {
    return HasServoData() && Servo_Element_IsDisplayContents(this);
  }

  /*
   * https://html.spec.whatwg.org/#being-rendered
   *
   * With a gotcha for display contents:
   *   https://github.com/whatwg/html/issues/1837
   */
  bool IsRendered() const { return GetPrimaryFrame() || IsDisplayContents(); }

  const nsAttrValue* GetParsedAttr(const nsAtom* aAttr) const {
    return mAttrs.GetAttr(aAttr);
  }

  const nsAttrValue* GetParsedAttr(const nsAtom* aAttr,
                                   int32_t aNameSpaceID) const {
    return mAttrs.GetAttr(aAttr, aNameSpaceID);
  }

  /**
   * Returns the attribute map, if there is one.
   *
   * @return existing attribute map or nullptr.
   */
  nsDOMAttributeMap* GetAttributeMap() {
    nsDOMSlots* slots = GetExistingDOMSlots();

    return slots ? slots->mAttributeMap.get() : nullptr;
  }

  virtual void RecompileScriptEventListeners() {}

  /**
   * Get the attr info for the given namespace ID and attribute name.  The
   * namespace ID must not be kNameSpaceID_Unknown and the name must not be
   * null.  Note that this can only return info on attributes that actually
   * live on this element (and is only virtual to handle XUL prototypes).  That
   * is, this should only be called from methods that only care about attrs
   * that effectively live in mAttrs.
   */
  BorrowedAttrInfo GetAttrInfo(int32_t aNamespaceID,
                               const nsAtom* aName) const {
    NS_ASSERTION(aName, "must have attribute name");
    NS_ASSERTION(aNamespaceID != kNameSpaceID_Unknown,
                 "must have a real namespace ID!");

    int32_t index = mAttrs.IndexOfAttr(aName, aNamespaceID);
    if (index < 0) {
      return BorrowedAttrInfo(nullptr, nullptr);
    }

    return mAttrs.AttrInfoAt(index);
  }

  /**
   * Parse a string into an nsAttrValue for a CORS attribute.  This
   * never fails.  The resulting value is an enumerated value whose
   * GetEnumValue() returns one of the above constants.
   */
  static void ParseCORSValue(const nsAString& aValue, nsAttrValue& aResult);

  /**
   * Return the CORS mode for a given string
   */
  static CORSMode StringToCORSMode(const nsAString& aValue);

  /**
   * Return the CORS mode for a given nsAttrValue (which may be null,
   * but if not should have been parsed via ParseCORSValue).
   */
  static CORSMode AttrValueToCORSMode(const nsAttrValue* aValue);

  nsINode* GetScopeChainParent() const override;

  /**
   * Locate a TextEditor rooted at this content node, if there is one.
   */
  MOZ_CAN_RUN_SCRIPT_BOUNDARY mozilla::TextEditor* GetTextEditorInternal();

  /**
   * Gets value of boolean attribute. Only works for attributes in null
   * namespace.
   *
   * @param aAttr    name of attribute.
   * @param aValue   Boolean value of attribute.
   */
  bool GetBoolAttr(nsAtom* aAttr) const {
    return HasAttr(kNameSpaceID_None, aAttr);
  }

  /**
   * Sets value of boolean attribute by removing attribute or setting it to
   * the empty string. Only works for attributes in null namespace.
   *
   * @param aAttr    name of attribute.
   * @param aValue   Boolean value of attribute.
   */
  nsresult SetBoolAttr(nsAtom* aAttr, bool aValue);

  /**
   * Gets the enum value string of an attribute and using a default value if
   * the attribute is missing or the string is an invalid enum value.
   *
   * @param aType     the name of the attribute.
   * @param aDefault  the default value if the attribute is missing or invalid.
   * @param aResult   string corresponding to the value [out].
   */
  void GetEnumAttr(nsAtom* aAttr, const char* aDefault,
                   nsAString& aResult) const;

  /**
   * Gets the enum value string of an attribute and using the default missing
   * value if the attribute is missing or the default invalid value if the
   * string is an invalid enum value.
   *
   * @param aType            the name of the attribute.
   * @param aDefaultMissing  the default value if the attribute is missing.  If
                             null and the attribute is missing, aResult will be
                             set to the null DOMString; this only matters for
                             cases in which we're reflecting a nullable string.
   * @param aDefaultInvalid  the default value if the attribute is invalid.
   * @param aResult          string corresponding to the value [out].
   */
  void GetEnumAttr(nsAtom* aAttr, const char* aDefaultMissing,
                   const char* aDefaultInvalid, nsAString& aResult) const;

  /**
   * Unset an attribute.
   */
  void UnsetAttr(nsAtom* aAttr, ErrorResult& aError) {
    aError = UnsetAttr(kNameSpaceID_None, aAttr, true);
  }

  /**
   * Set an attribute in the simplest way possible.
   */
  void SetAttr(nsAtom* aAttr, const nsAString& aValue, ErrorResult& aError) {
    aError = SetAttr(kNameSpaceID_None, aAttr, aValue, true);
  }

  void SetAttr(nsAtom* aAttr, const nsAString& aValue,
               nsIPrincipal* aTriggeringPrincipal, ErrorResult& aError) {
    aError =
        SetAttr(kNameSpaceID_None, aAttr, aValue, aTriggeringPrincipal, true);
  }

  /**
   * Set a content attribute via a reflecting nullable string IDL
   * attribute (e.g. a CORS attribute).  If DOMStringIsNull(aValue),
   * this will actually remove the content attribute.
   */
  void SetOrRemoveNullableStringAttr(nsAtom* aName, const nsAString& aValue,
                                     ErrorResult& aError);

  /**
   * Retrieve the ratio of font-size-inflated text font size to computed font
   * size for this element. This will query the element for its primary frame,
   * and then use this to get font size inflation information about the frame.
   *
   * @returns The font size inflation ratio (inflated font size to uninflated
   *          font size) for the primary frame of this element. Returns 1.0
   *          by default if font size inflation is not enabled. Returns -1
   *          if the element does not have a primary frame.
   *
   * @note The font size inflation ratio that is returned is actually the
   *       font size inflation data for the element's _primary frame_, not the
   *       element itself, but for most purposes, this should be sufficient.
   */
  float FontSizeInflation();

  void GetImplementedPseudoElement(nsAString&) const;

  ReferrerPolicy GetReferrerPolicyAsEnum();
  ReferrerPolicy ReferrerPolicyFromAttr(const nsAttrValue* aValue);

  /*
   * Helpers for .dataset.  This is implemented on Element, though only some
   * sorts of elements expose it to JS as a .dataset property
   */
  // Getter, to be called from bindings.
  already_AddRefed<nsDOMStringMap> Dataset();
  // Callback for destructor of dataset to ensure to null out our weak pointer
  // to it.
  void ClearDataset();

  void RegisterIntersectionObserver(DOMIntersectionObserver* aObserver);
  void UnregisterIntersectionObserver(DOMIntersectionObserver* aObserver);
  void UnlinkIntersectionObservers();
  bool UpdateIntersectionObservation(DOMIntersectionObserver* aObserver,
                                     int32_t threshold);

  // A number of methods to cast to various XUL interfaces. They return a
  // pointer only if the element implements that interface.
  already_AddRefed<nsIDOMXULButtonElement> AsXULButton();
  already_AddRefed<nsIDOMXULContainerElement> AsXULContainer();
  already_AddRefed<nsIDOMXULContainerItemElement> AsXULContainerItem();
  already_AddRefed<nsIDOMXULControlElement> AsXULControl();
  already_AddRefed<nsIDOMXULMenuListElement> AsXULMenuList();
  already_AddRefed<nsIDOMXULMultiSelectControlElement>
  AsXULMultiSelectControl();
  already_AddRefed<nsIDOMXULRadioGroupElement> AsXULRadioGroup();
  already_AddRefed<nsIDOMXULRelatedElement> AsXULRelated();
  already_AddRefed<nsIDOMXULSelectControlElement> AsXULSelectControl();
  already_AddRefed<nsIDOMXULSelectControlItemElement> AsXULSelectControlItem();
  already_AddRefed<nsIBrowser> AsBrowser();
  already_AddRefed<nsIAutoCompletePopup> AsAutoCompletePopup();

 protected:
  /*
   * Named-bools for use with SetAttrAndNotify to make call sites easier to
   * read.
   */
  static const bool kFireMutationEvent = true;
  static const bool kDontFireMutationEvent = false;
  static const bool kNotifyDocumentObservers = true;
  static const bool kDontNotifyDocumentObservers = false;
  static const bool kCallAfterSetAttr = true;
  static const bool kDontCallAfterSetAttr = false;

  /**
   * Set attribute and (if needed) notify documentobservers and fire off
   * mutation events.  This will send the AttributeChanged notification.
   * Callers of this method are responsible for calling AttributeWillChange,
   * since that needs to happen before the new attr value has been set, and
   * in particular before it has been parsed.
   *
   * For the boolean parameters, consider using the named bools above to aid
   * code readability.
   *
   * @param aNamespaceID  namespace of attribute
   * @param aAttribute    local-name of attribute
   * @param aPrefix       aPrefix of attribute
   * @param aOldValue     The old value of the attribute to use as a fallback
   *                      in the cases where the actual old value (i.e.
   *                      its current value) is !StoresOwnData() --- in which
   *                      case the current value is probably already useless.
   *                      If the current value is StoresOwnData() (or absent),
   *                      aOldValue will not be used. aOldValue will only be set
   *                      in certain circumstances (there are mutation
   *                      listeners, element is a custom element, attribute was
   *                      not previously unset). Otherwise it will be null.
   * @param aParsedValue  parsed new value of attribute. Replaced by the
   *                      old value of the attribute. This old value is only
   *                      useful if either it or the new value is StoresOwnData.
   * @param aMaybeScriptedPrincipal
   *                      the principal of the scripted caller responsible for
   *                      setting the attribute, or null if no scripted caller
   *                      can be determined. A null value here does not
   *                      guarantee that there is no scripted caller, but a
   *                      non-null value does guarantee that a scripted caller
   *                      with the given principal is directly responsible for
   *                      the attribute change.
   * @param aModType      MutationEvent_Binding::MODIFICATION or ADDITION.  Only
   *                      needed if aFireMutation or aNotify is true.
   * @param aFireMutation should mutation-events be fired?
   * @param aNotify       should we notify document-observers?
   * @param aCallAfterSetAttr should we call AfterSetAttr?
   * @param aComposedDocument The current composed document of the element.
   */
  nsresult SetAttrAndNotify(int32_t aNamespaceID, nsAtom* aName,
                            nsAtom* aPrefix, const nsAttrValue* aOldValue,
                            nsAttrValue& aParsedValue,
                            nsIPrincipal* aMaybeScriptedPrincipal,
                            uint8_t aModType, bool aFireMutation, bool aNotify,
                            bool aCallAfterSetAttr, Document* aComposedDocument,
                            const mozAutoDocUpdate& aGuard);

  /**
   * Scroll to a new position using behavior evaluated from CSS and
   * a CSSOM-View DOM method ScrollOptions dictionary.  The scrolling may
   * be performed asynchronously or synchronously depending on the resolved
   * scroll-behavior.
   *
   * @param aScroll       Destination of scroll, in CSS pixels
   * @param aOptions      Dictionary of options to be evaluated
   */
  MOZ_CAN_RUN_SCRIPT
  void Scroll(const CSSIntPoint& aScroll, const ScrollOptions& aOptions);

  /**
   * Convert an attribute string value to attribute type based on the type of
   * attribute.  Called by SetAttr().  Note that at the moment we only do this
   * for attributes in the null namespace (kNameSpaceID_None).
   *
   * @param aNamespaceID the namespace of the attribute to convert
   * @param aAttribute the attribute to convert
   * @param aValue the string value to convert
   * @param aMaybeScriptedPrincipal the principal of the script setting the
   *        attribute, if one can be determined, or null otherwise. As in
   *        AfterSetAttr, a null value does not guarantee that the attribute was
   *        not set by a scripted caller, but a non-null value guarantees that
   *        the attribute was set by a scripted caller with the given principal.
   * @param aResult the nsAttrValue [OUT]
   * @return true if the parsing was successful, false otherwise
   */
  virtual bool ParseAttribute(int32_t aNamespaceID, nsAtom* aAttribute,
                              const nsAString& aValue,
                              nsIPrincipal* aMaybeScriptedPrincipal,
                              nsAttrValue& aResult);

  /**
   * Try to set the attribute as a mapped attribute, if applicable.  This will
   * only be called for attributes that are in the null namespace and only on
   * attributes that returned true when passed to IsAttributeMapped.  The
   * caller will not try to set the attr in any other way if this method
   * returns true (the value of aRetval does not matter for that purpose).
   *
   * @param aName the name of the attribute
   * @param aValue the nsAttrValue to set. Will be swapped with the existing
   *               value of the attribute if the attribute already exists.
   * @param [out] aValueWasSet If the attribute was not set previously,
   *                           aValue will be swapped with an empty attribute
   *                           and aValueWasSet will be set to false. Otherwise,
   *                           aValueWasSet will be set to true and aValue will
   *                           contain the previous value set.
   * @param [out] aRetval the nsresult status of the operation, if any.
   * @return true if the setting was attempted, false otherwise.
   */
  virtual bool SetAndSwapMappedAttribute(nsAtom* aName, nsAttrValue& aValue,
                                         bool* aValueWasSet, nsresult* aRetval);

  /**
   * Hook that is called by Element::SetAttr to allow subclasses to
   * deal with attribute sets.  This will only be called after we verify that
   * we're actually doing an attr set and will be called before
   * AttributeWillChange and before ParseAttribute and hence before we've set
   * the new value.
   *
   * @param aNamespaceID the namespace of the attr being set
   * @param aName the localname of the attribute being set
   * @param aValue the value it's being set to represented as either a string or
   *        a parsed nsAttrValue. Alternatively, if the attr is being removed it
   *        will be null.
   * @param aNotify Whether we plan to notify document observers.
   */
  virtual nsresult BeforeSetAttr(int32_t aNamespaceID, nsAtom* aName,
                                 const nsAttrValueOrString* aValue,
                                 bool aNotify);

  /**
   * Hook that is called by Element::SetAttr to allow subclasses to
   * deal with attribute sets.  This will only be called after we have called
   * SetAndSwapAttr (that is, after we have actually set the attr).  It will
   * always be called under a scriptblocker.
   *
   * @param aNamespaceID the namespace of the attr being set
   * @param aName the localname of the attribute being set
   * @param aValue the value it's being set to.  If null, the attr is being
   *        removed.
   * @param aOldValue the value that the attribute had previously. If null,
   *        the attr was not previously set. This argument may not have the
   *        correct value for SVG elements, or other cases in which the
   *        attribute value doesn't store its own data
   * @param aMaybeScriptedPrincipal the principal of the scripted caller
   *        responsible for setting the attribute, or null if no scripted caller
   *        can be determined, or the attribute is being unset. A null value
   *        here does not guarantee that there is no scripted caller, but a
   *        non-null value does guarantee that a scripted caller with the given
   *        principal is directly responsible for the attribute change.
   * @param aNotify Whether we plan to notify document observers.
   */
  virtual nsresult AfterSetAttr(int32_t aNamespaceID, nsAtom* aName,
                                const nsAttrValue* aValue,
                                const nsAttrValue* aOldValue,
                                nsIPrincipal* aMaybeScriptedPrincipal,
                                bool aNotify);

  /**
   * This function shall be called just before the id attribute changes. It will
   * be called after BeforeSetAttr. If the attribute being changed is not the id
   * attribute, this function does nothing. Otherwise, it will remove the old id
   * from the document's id cache.
   *
   * This must happen after BeforeSetAttr (rather than during) because the
   * the subclasses' calls to BeforeSetAttr may notify on state changes. If they
   * incorrectly determine whether the element had an id, the element may not be
   * restyled properly.
   *
   * @param aNamespaceID the namespace of the attr being set
   * @param aName the localname of the attribute being set
   * @param aValue the new id value. Will be null if the id is being unset.
   */
  void PreIdMaybeChange(int32_t aNamespaceID, nsAtom* aName,
                        const nsAttrValueOrString* aValue);

  /**
   * This function shall be called just after the id attribute changes. It will
   * be called before AfterSetAttr. If the attribute being changed is not the id
   * attribute, this function does nothing. Otherwise, it will add the new id to
   * the document's id cache and properly set the ElementHasID flag.
   *
   * This must happen before AfterSetAttr (rather than during) because the
   * the subclasses' calls to AfterSetAttr may notify on state changes. If they
   * incorrectly determine whether the element now has an id, the element may
   * not be restyled properly.
   *
   * @param aNamespaceID the namespace of the attr being set
   * @param aName the localname of the attribute being set
   * @param aValue the new id value. Will be null if the id is being unset.
   */
  void PostIdMaybeChange(int32_t aNamespaceID, nsAtom* aName,
                         const nsAttrValue* aValue);

  /**
   * Usually, setting an attribute to the value that it already has results in
   * no action. However, in some cases, setting an attribute to its current
   * value should have the effect of, for example, forcing a reload of
   * network data. To address that, this function will be called in this
   * situation to allow the handling of such a case.
   *
   * @param aNamespaceID the namespace of the attr being set
   * @param aName the localname of the attribute being set
   * @param aValue the value it's being set to represented as either a string or
   *        a parsed nsAttrValue.
   * @param aNotify Whether we plan to notify document observers.
   */
  // Note that this is inlined so that when subclasses call it it gets
  // inlined.  Those calls don't go through a vtable.
  virtual nsresult OnAttrSetButNotChanged(int32_t aNamespaceID, nsAtom* aName,
                                          const nsAttrValueOrString& aValue,
                                          bool aNotify);

  /**
   * Hook to allow subclasses to produce a different EventListenerManager if
   * needed for attachment of attribute-defined handlers
   */
  virtual EventListenerManager* GetEventListenerManagerForAttr(
      nsAtom* aAttrName, bool* aDefer);

  /**
   * Internal hook for converting an attribute name-string to nsAttrName in
   * case there is such existing attribute. aNameToUse can be passed to get
   * name which was used for looking for the attribute (lowercase in HTML).
   */
  const nsAttrName* InternalGetAttrNameFromQName(
      const nsAString& aStr, nsAutoString* aNameToUse = nullptr) const;

  virtual Element* GetNameSpaceElement() override { return this; }

  Attr* GetAttributeNodeNSInternal(const nsAString& aNamespaceURI,
                                   const nsAString& aLocalName);

  inline void RegisterActivityObserver();
  inline void UnregisterActivityObserver();

  /**
   * Add/remove this element to the documents id cache
   */
  void AddToIdTable(nsAtom* aId);
  void RemoveFromIdTable();

  /**
   * Functions to carry out event default actions for links of all types
   * (HTML links, XLinks, SVG "XLinks", etc.)
   */

  /**
   * Check that we meet the conditions to handle a link event
   * and that we are actually on a link.
   *
   * @param aVisitor event visitor
   * @param aURI the uri of the link, set only if the return value is true [OUT]
   * @return true if we can handle the link event, false otherwise
   */
  bool CheckHandleEventForLinksPrecondition(EventChainVisitor& aVisitor,
                                            nsIURI** aURI) const;

  /**
   * Handle status bar updates before they can be cancelled.
   */
  void GetEventTargetParentForLinks(EventChainPreVisitor& aVisitor);

  /**
   * Handle default actions for link event if the event isn't consumed yet.
   */
  MOZ_CAN_RUN_SCRIPT
  nsresult PostHandleEventForLinks(EventChainPostVisitor& aVisitor);

  /**
   * Get the target of this link element. Consumers should established that
   * this element is a link (probably using IsLink) before calling this
   * function (or else why call it?)
   *
   * Note: for HTML this gets the value of the 'target' attribute; for XLink
   * this gets the value of the xlink:_moz_target attribute, or failing that,
   * the value of xlink:show, converted to a suitably equivalent named target
   * (e.g. _blank).
   */
  virtual void GetLinkTarget(nsAString& aTarget);

  enum class ReparseAttributes { No, Yes };
  /**
   * Copy attributes and state to another element
   * @param aDest the object to copy to
   */
  nsresult CopyInnerTo(Element* aDest,
                       ReparseAttributes = ReparseAttributes::Yes);

  /**
   * Some event handler content attributes have a different name (e.g. different
   * case) from the actual event name.  This function takes an event handler
   * content attribute name and returns the corresponding event name, to be used
   * for adding the actual event listener.
   */
  static nsAtom* GetEventNameForAttr(nsAtom* aAttr);

 private:
#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
  void AssertInvariantsOnNodeInfoChange();
#endif

  /**
   * Slow path for GetClasses, this should only be called for SVG elements.
   */
  const nsAttrValue* GetSVGAnimatedClass() const;

  /**
   * Get this element's client area rect in app units.
   * @return the frame's client area
   */
  MOZ_CAN_RUN_SCRIPT nsRect GetClientAreaRect();

  /**
   * GetCustomInterface is somewhat like a GetInterface, but it is expected
   * that the implementation is provided by a custom element or via the
   * the XBL implements keyword. To use this, create a public method that
   * wraps a call to GetCustomInterface.
   */
  template <class T>
  void GetCustomInterface(nsGetterAddRefs<T> aResult);

  // Prevent people from doing pointless checks/casts on Element instances.
  void IsElement() = delete;
  void AsElement() = delete;

  // Data members
  EventStates mState;
  // Per-node data managed by Servo.
  //
  // There should not be data on nodes that are not in the flattened tree, or
  // descendants of display: none elements.
  mozilla::RustCell<ServoNodeData*> mServoData;

 protected:
  // Array containing all attributes for this element
  AttrArray mAttrs;
};

NS_DEFINE_STATIC_IID_ACCESSOR(Element, NS_ELEMENT_IID)

inline bool Element::HasAttr(int32_t aNameSpaceID, const nsAtom* aName) const {
  NS_ASSERTION(nullptr != aName, "must have attribute name");
  NS_ASSERTION(aNameSpaceID != kNameSpaceID_Unknown,
               "must have a real namespace ID!");

  return mAttrs.IndexOfAttr(aName, aNameSpaceID) >= 0;
}

inline bool Element::HasNonEmptyAttr(int32_t aNameSpaceID,
                                     const nsAtom* aName) const {
  MOZ_ASSERT(aNameSpaceID > kNameSpaceID_Unknown, "Must have namespace");
  MOZ_ASSERT(aName, "Must have attribute name");

  const nsAttrValue* val = mAttrs.GetAttr(aName, aNameSpaceID);
  return val && !val->IsEmptyString();
}

inline bool Element::AttrValueIs(int32_t aNameSpaceID, const nsAtom* aName,
                                 const nsAString& aValue,
                                 nsCaseTreatment aCaseSensitive) const {
  NS_ASSERTION(aName, "Must have attr name");
  NS_ASSERTION(aNameSpaceID != kNameSpaceID_Unknown, "Must have namespace");

  const nsAttrValue* val = mAttrs.GetAttr(aName, aNameSpaceID);
  return val && val->Equals(aValue, aCaseSensitive);
}

inline bool Element::AttrValueIs(int32_t aNameSpaceID, const nsAtom* aName,
                                 const nsAtom* aValue,
                                 nsCaseTreatment aCaseSensitive) const {
  NS_ASSERTION(aName, "Must have attr name");
  NS_ASSERTION(aNameSpaceID != kNameSpaceID_Unknown, "Must have namespace");
  NS_ASSERTION(aValue, "Null value atom");

  const nsAttrValue* val = mAttrs.GetAttr(aName, aNameSpaceID);
  return val && val->Equals(aValue, aCaseSensitive);
}

}  // namespace dom
}  // namespace mozilla

inline mozilla::dom::Element* nsINode::AsElement() {
  MOZ_ASSERT(IsElement());
  return static_cast<mozilla::dom::Element*>(this);
}

inline const mozilla::dom::Element* nsINode::AsElement() const {
  MOZ_ASSERT(IsElement());
  return static_cast<const mozilla::dom::Element*>(this);
}

inline mozilla::dom::Element* nsINode::GetParentElement() const {
  return mozilla::dom::Element::FromNodeOrNull(mParent);
}

inline mozilla::dom::Element* nsINode::GetPreviousElementSibling() const {
  nsIContent* previousSibling = GetPreviousSibling();
  while (previousSibling) {
    if (previousSibling->IsElement()) {
      return previousSibling->AsElement();
    }
    previousSibling = previousSibling->GetPreviousSibling();
  }

  return nullptr;
}

inline mozilla::dom::Element* nsINode::GetAsElementOrParentElement() const {
  return IsElement() ? const_cast<mozilla::dom::Element*>(AsElement())
                     : GetParentElement();
}

inline mozilla::dom::Element* nsINode::GetNextElementSibling() const {
  nsIContent* nextSibling = GetNextSibling();
  while (nextSibling) {
    if (nextSibling->IsElement()) {
      return nextSibling->AsElement();
    }
    nextSibling = nextSibling->GetNextSibling();
  }

  return nullptr;
}

/**
 * Macros to implement Clone(). _elementName is the class for which to implement
 * Clone.
 */
#define NS_IMPL_ELEMENT_CLONE(_elementName)                         \
  nsresult _elementName::Clone(mozilla::dom::NodeInfo* aNodeInfo,   \
                               nsINode** aResult) const {           \
    *aResult = nullptr;                                             \
    RefPtr<mozilla::dom::NodeInfo> ni(aNodeInfo);                   \
    auto* nim = ni->NodeInfoManager();                              \
    RefPtr<_elementName> it = new (nim) _elementName(ni.forget());  \
    nsresult rv = const_cast<_elementName*>(this)->CopyInnerTo(it); \
    if (NS_SUCCEEDED(rv)) {                                         \
      it.forget(aResult);                                           \
    }                                                               \
                                                                    \
    return rv;                                                      \
  }

#define EXPAND(...) __VA_ARGS__
#define NS_IMPL_ELEMENT_CLONE_WITH_INIT_HELPER(_elementName, extra_args_) \
  nsresult _elementName::Clone(mozilla::dom::NodeInfo* aNodeInfo,         \
                               nsINode** aResult) const {                 \
    *aResult = nullptr;                                                   \
    RefPtr<mozilla::dom::NodeInfo> ni(aNodeInfo);                         \
    auto* nim = ni->NodeInfoManager();                                    \
    RefPtr<_elementName> it =                                             \
        new (nim) _elementName(ni.forget() EXPAND extra_args_);           \
    nsresult rv = it->Init();                                             \
    nsresult rv2 = const_cast<_elementName*>(this)->CopyInnerTo(it);      \
    if (NS_FAILED(rv2)) {                                                 \
      rv = rv2;                                                           \
    }                                                                     \
    if (NS_SUCCEEDED(rv)) {                                               \
      it.forget(aResult);                                                 \
    }                                                                     \
                                                                          \
    return rv;                                                            \
  }

#define NS_IMPL_ELEMENT_CLONE_WITH_INIT(_elementName) \
  NS_IMPL_ELEMENT_CLONE_WITH_INIT_HELPER(_elementName, ())
#define NS_IMPL_ELEMENT_CLONE_WITH_INIT_AND_PARSER(_elementName) \
  NS_IMPL_ELEMENT_CLONE_WITH_INIT_HELPER(_elementName, (, NOT_FROM_PARSER))

#endif  // mozilla_dom_Element_h__