gecko-dev/dom/svg/DOMSVGLengthList.h

/* -*- 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 MOZILLA_DOMSVGLENGTHLIST_H__
#define MOZILLA_DOMSVGLENGTHLIST_H__

#include "DOMSVGAnimatedLengthList.h"
#include "nsCycleCollectionParticipant.h"
#include "nsDebug.h"
#include "nsTArray.h"
#include "SVGLengthList.h"
#include "mozilla/Attributes.h"
#include "mozilla/ErrorResult.h"
#include "mozilla/Unused.h"

namespace mozilla {

namespace dom {
class DOMSVGLength;
class SVGElement;

/**
 * Class DOMSVGLengthList
 *
 * This class is used to create the DOM tearoff objects that wrap internal
 * SVGLengthList objects.
 *
 * See the architecture comment in DOMSVGAnimatedLengthList.h.
 *
 * This class is strongly intertwined with DOMSVGAnimatedLengthList and
 * DOMSVGLength. We are a friend of DOMSVGAnimatedLengthList, and are
 * responsible for nulling out our DOMSVGAnimatedLengthList's pointer to us
 * when we die, essentially making its pointer to us a weak pointer. Similarly,
 * our DOMSVGLength items are friends of us and responsible for nulling out our
 * pointers to them.
 *
 * Our DOM items are created lazily on demand as and when script requests them.
 */
class DOMSVGLengthList final : public nsISupports, public nsWrapperCache {
  friend class AutoChangeLengthListNotifier;
  friend class DOMSVGLength;

  ~DOMSVGLengthList() {
    // Our mAList's weak ref to us must be nulled out when we die. If GC has
    // unlinked us using the cycle collector code, then that has already
    // happened, and mAList is null.
    if (mAList) {
      (IsAnimValList() ? mAList->mAnimVal : mAList->mBaseVal) = nullptr;
    }
  }

 public:
  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(DOMSVGLengthList)

  DOMSVGLengthList(DOMSVGAnimatedLengthList* aAList,
                   const SVGLengthList& aInternalList)
      : mAList(aAList) {
    // aInternalList must be passed in explicitly because we can't use
    // InternalList() here. (Because it depends on IsAnimValList, which depends
    // on this object having been assigned to aAList's mBaseVal or mAnimVal,
    // which hasn't happened yet.)

    InternalListLengthWillChange(aInternalList.Length());  // Sync mItems
  }

  virtual JSObject* WrapObject(JSContext* cx,
                               JS::Handle<JSObject*> aGivenProto) override;

  nsISupports* GetParentObject() { return static_cast<nsIContent*>(Element()); }

  /**
   * This will normally be the same as InternalList().Length(), except if we've
   * hit OOM in which case our length will be zero.
   */
  uint32_t LengthNoFlush() const {
    MOZ_ASSERT(
        mItems.Length() == 0 || mItems.Length() == InternalList().Length(),
        "DOM wrapper's list length is out of sync");
    return mItems.Length();
  }

  /// Called to notify us to synchronize our length and detach excess items.
  void InternalListLengthWillChange(uint32_t aNewLength);

  /**
   * Returns true if our attribute is animating (in which case our animVal is
   * not simply a mirror of our baseVal).
   */
  bool IsAnimating() const { return mAList->IsAnimating(); }
  /**
   * Returns true if there is an animated list mirroring the base list.
   */
  bool AnimListMirrorsBaseList() const {
    return mAList->mAnimVal && !mAList->IsAnimating();
  }

  uint32_t NumberOfItems() const {
    if (IsAnimValList()) {
      Element()->FlushAnimations();
    }
    return LengthNoFlush();
  }
  void Clear(ErrorResult& aError);
  already_AddRefed<DOMSVGLength> Initialize(DOMSVGLength& newItem,
                                            ErrorResult& error);
  already_AddRefed<DOMSVGLength> GetItem(uint32_t index, ErrorResult& error);
  already_AddRefed<DOMSVGLength> IndexedGetter(uint32_t index, bool& found,
                                               ErrorResult& error);
  already_AddRefed<DOMSVGLength> InsertItemBefore(DOMSVGLength& newItem,
                                                  uint32_t index,
                                                  ErrorResult& error);
  already_AddRefed<DOMSVGLength> ReplaceItem(DOMSVGLength& newItem,
                                             uint32_t index,
                                             ErrorResult& error);
  already_AddRefed<DOMSVGLength> RemoveItem(uint32_t index, ErrorResult& error);
  already_AddRefed<DOMSVGLength> AppendItem(DOMSVGLength& newItem,
                                            ErrorResult& error) {
    return InsertItemBefore(newItem, LengthNoFlush(), error);
  }
  void IndexedSetter(uint32_t index, DOMSVGLength& newValue,
                     ErrorResult& error) {
    // Need to take a ref to the return value so it does not leak.
    RefPtr<DOMSVGLength> ignored = ReplaceItem(newValue, index, error);
    Unused << ignored;
  }
  uint32_t Length() const { return NumberOfItems(); }

 private:
  dom::SVGElement* Element() const { return mAList->mElement; }

  uint8_t AttrEnum() const { return mAList->mAttrEnum; }

  uint8_t Axis() const { return mAList->mAxis; }

  /// Used to determine if this list is the baseVal or animVal list.
  bool IsAnimValList() const {
    MOZ_ASSERT(this == mAList->mBaseVal || this == mAList->mAnimVal,
               "Calling IsAnimValList() too early?!");
    return this == mAList->mAnimVal;
  }

  /**
   * Get a reference to this object's corresponding internal SVGLengthList.
   *
   * To simplify the code we just have this one method for obtaining both
   * baseVal and animVal internal lists. This means that animVal lists don't
   * get const protection, but our setter methods guard against changing
   * animVal lists.
   */
  SVGLengthList& InternalList() const;

  /// Returns the DOMSVGLength at aIndex, creating it if necessary.
  already_AddRefed<DOMSVGLength> GetItemAt(uint32_t aIndex);

  void MaybeInsertNullInAnimValListAt(uint32_t aIndex);
  void MaybeRemoveItemFromAnimValListAt(uint32_t aIndex);

  // Weak refs to our DOMSVGLength items. The items are friends and take care
  // of clearing our pointer to them when they die.
  FallibleTArray<DOMSVGLength*> mItems;

  RefPtr<DOMSVGAnimatedLengthList> mAList;
};

}  // namespace dom
}  // namespace mozilla

#endif  // MOZILLA_DOMSVGLENGTHLIST_H__