DOMIntersectionObserver.h

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/* -*- 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/. */

#ifndef DOMIntersectionObserver_h

#define DOMIntersectionObserver_h

#include "mozilla/Attributes.h"

#include "mozilla/dom/IntersectionObserverBinding.h"

#include "mozilla/ServoStyleConsts.h"

#include "mozilla/Variant.h"

#include "nsDOMNavigationTiming.h"

#include "nsTArray.h"

#include "nsTHashSet.h"

namespace mozilla::dom {

class DOMIntersectionObserver;

class DOMIntersectionObserverEntry final : public nsISupports,

                                           public nsWrapperCache {

  ~DOMIntersectionObserverEntry() = default;

 public:

  DOMIntersectionObserverEntry(nsISupports* aOwner, DOMHighResTimeStamp aTime,

                               RefPtr<DOMRect> aRootBounds,

                               RefPtr<DOMRect> aBoundingClientRect,

                               RefPtr<DOMRect> aIntersectionRect,

                               bool aIsIntersecting, Element* aTarget,

                               double aIntersectionRatio)

      : mOwner(aOwner),

        mTime(aTime),

        mRootBounds(std::move(aRootBounds)),

        mBoundingClientRect(std::move(aBoundingClientRect)),

        mIntersectionRect(std::move(aIntersectionRect)),

        mIsIntersecting(aIsIntersecting),

        mTarget(aTarget),

        mIntersectionRatio(aIntersectionRatio) {}

  NS_DECL_CYCLE_COLLECTING_ISUPPORTS

  NS_DECL_CYCLE_COLLECTION_WRAPPERCACHE_CLASS(DOMIntersectionObserverEntry)

  nsISupports* GetParentObject() const { return mOwner; }

  JSObject* WrapObject(JSContext* aCx,

                       JS::Handle<JSObject*> aGivenProto) override {

    return IntersectionObserverEntry_Binding::Wrap(aCx, this, aGivenProto);

  DOMHighResTimeStamp Time() const { return mTime; }

  DOMRect* GetRootBounds() { return mRootBounds; }

  DOMRect* BoundingClientRect() { return mBoundingClientRect; }

  DOMRect* IntersectionRect() { return mIntersectionRect; }

  bool IsIntersecting() const { return mIsIntersecting; }

  double IntersectionRatio() const { return mIntersectionRatio; }

  Element* Target() { return mTarget; }

 protected:

  nsCOMPtr<nsISupports> mOwner;

  DOMHighResTimeStamp mTime;

  RefPtr<DOMRect> mRootBounds;

  RefPtr<DOMRect> mBoundingClientRect;

  RefPtr<DOMRect> mIntersectionRect;

  bool mIsIntersecting;

  RefPtr<Element> mTarget;

  double mIntersectionRatio;

};

#define NS_DOM_INTERSECTION_OBSERVER_IID             \

  {                                                  \

    0x8570a575, 0xe303, 0x4d18, {                    \

      0xb6, 0xb1, 0x4d, 0x2b, 0x49, 0xd8, 0xef, 0x94 \

    }                                                \

// An input suitable to compute intersections with multiple targets.

struct IntersectionInput {

  // Whether the root is implicit (null, originally).

  const bool mIsImplicitRoot = false;

  // The computed root node. For the implicit root, this will be the in-process

  // root document we can compute coordinates against (along with the remote

  // document visible rect if appropriate).

  const nsINode* mRootNode = nullptr;

  nsIFrame* mRootFrame = nullptr;

  // The rect of mRootFrame in client coordinates.

  nsRect mRootRect;

  // The root margin computed against the root rect.

  nsMargin mRootMargin;

  // If this is in an OOP iframe, the visible rect of the OOP frame.

  Maybe<nsRect> mRemoteDocumentVisibleRect;

};

struct IntersectionOutput {

  const bool mIsSimilarOrigin;

  const nsRect mRootBounds;

  const nsRect mTargetRect;

  const Maybe<nsRect> mIntersectionRect;

  bool Intersects() const { return mIntersectionRect.isSome(); }

};

class DOMIntersectionObserver final : public nsISupports,

                                      public nsWrapperCache {

  virtual ~DOMIntersectionObserver() { Disconnect(); }

  using NativeCallback = void (*)(

      const Sequence<OwningNonNull<DOMIntersectionObserverEntry>>& aEntries);

  DOMIntersectionObserver(Document&, NativeCallback);

 public:

  DOMIntersectionObserver(already_AddRefed<nsPIDOMWindowInner>&& aOwner,

                          dom::IntersectionCallback& aCb);

  NS_DECL_CYCLE_COLLECTING_ISUPPORTS

  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(DOMIntersectionObserver)

  NS_DECLARE_STATIC_IID_ACCESSOR(NS_DOM_INTERSECTION_OBSERVER_IID)

  static already_AddRefed<DOMIntersectionObserver> Constructor(

      const GlobalObject&, dom::IntersectionCallback&, ErrorResult&);

  static already_AddRefed<DOMIntersectionObserver> Constructor(

      const GlobalObject&, dom::IntersectionCallback&,

      const IntersectionObserverInit&, ErrorResult&);

  JSObject* WrapObject(JSContext* aCx,

                       JS::Handle<JSObject*> aGivenProto) override {

    return IntersectionObserver_Binding::Wrap(aCx, this, aGivenProto);

  nsISupports* GetParentObject() const;

  nsINode* GetRoot() const { return mRoot; }

  void GetRootMargin(nsACString&);

  bool SetRootMargin(const nsACString&);

  void GetThresholds(nsTArray<double>& aRetVal);

  void Observe(Element& aTarget);

  void Unobserve(Element& aTarget);

  void UnlinkTarget(Element& aTarget);

  void Disconnect();

  void TakeRecords(nsTArray<RefPtr<DOMIntersectionObserverEntry>>& aRetVal);

  static StyleRect<LengthPercentage> LazyLoadingRootMargin();

  static IntersectionInput ComputeInput(

      const Document& aDocument, const nsINode* aRoot,

      const StyleRect<LengthPercentage>* aRootMargin);

  enum class IsForProximityToViewport : bool { No, Yes };

  enum class BoxToUse : uint8_t {

    Content,

    Border,

    OverflowClip,

};

  static IntersectionOutput Intersect(

      const IntersectionInput&, const Element&, BoxToUse = BoxToUse::Border,

      IsForProximityToViewport = IsForProximityToViewport::No);

  // Intersects with a given rect, already relative to the root frame.

  static IntersectionOutput Intersect(const IntersectionInput&, const nsRect&);

  void Update(Document& aDocument, DOMHighResTimeStamp time);

  MOZ_CAN_RUN_SCRIPT void Notify();

  static already_AddRefed<DOMIntersectionObserver> CreateLazyLoadObserver(

      Document&);

  static Maybe<nsRect> EdgeInclusiveIntersection(const nsRect& aRect,

                                                 const nsRect& aOtherRect);

 protected:

  void Connect();

  void QueueIntersectionObserverEntry(Element* aTarget,

                                      DOMHighResTimeStamp time,

                                      const Maybe<nsRect>& aRootRect,

                                      const nsRect& aTargetRect,

                                      const Maybe<nsRect>& aIntersectionRect,

                                      bool aIsIntersecting,

                                      double aIntersectionRatio);

  nsCOMPtr<nsPIDOMWindowInner> mOwner;

  RefPtr<Document> mDocument;

  Variant<RefPtr<dom::IntersectionCallback>, NativeCallback> mCallback;

  RefPtr<nsINode> mRoot;

  StyleRect<LengthPercentage> mRootMargin;

  AutoTArray<double, 1> mThresholds;

  // These hold raw pointers which are explicitly cleared by UnlinkTarget().

//

  // We keep a set and an array because we need ordered access, but also

  // constant time lookup.

  nsTArray<Element*> mObservationTargets;

  // Value can be:

  //   -2:   Makes sure next calculated threshold always differs, leading to a

  //         notification task being scheduled.

  //   -1:   Non-intersecting.

  //   >= 0: Intersecting, valid index of aObserver->mThresholds.

  enum ObservationState : int32_t { Uninitialized = -2, NotIntersecting = -1 };

  nsTHashMap<Element*, int32_t> mObservationTargetMap;

  nsTArray<RefPtr<DOMIntersectionObserverEntry>> mQueuedEntries;

  bool mConnected = false;

};

NS_DEFINE_STATIC_IID_ACCESSOR(DOMIntersectionObserver,

                              NS_DOM_INTERSECTION_OBSERVER_IID)

}  // namespace mozilla::dom

#endif