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diff --git a/dom/svg/DOMSVGPointList.h b/dom/svg/DOMSVGPointList.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 MOZILLA_DOMSVGPOINTLIST_H__
+#define MOZILLA_DOMSVGPOINTLIST_H__
+
+#include "nsCOMPtr.h"
+#include "nsCycleCollectionParticipant.h"
+#include "nsDebug.h"
+#include "nsSVGElement.h"
+#include "nsTArray.h"
+#include "SVGPointList.h" // IWYU pragma: keep
+#include "mozilla/Attributes.h"
+#include "mozilla/ErrorResult.h"
+
+namespace mozilla {
+
+class DOMSVGPoint;
+class nsISVGPoint;
+class SVGAnimatedPointList;
+
+/**
+ * Class DOMSVGPointList
+ *
+ * This class is used to create the DOM tearoff objects that wrap internal
+ * SVGPointList objects.
+ *
+ * See the architecture comment in DOMSVGAnimatedLengthList.h first (that's
+ * LENGTH list), then continue reading the remainder of this comment.
+ *
+ * The architecture of this class is very similar to that of DOMSVGLengthList
+ * except that, since there is no nsIDOMSVGAnimatedPointList interface
+ * in SVG, we have no parent DOMSVGAnimatedPointList (unlike DOMSVGLengthList
+ * which has a parent DOMSVGAnimatedLengthList class). (There is an
+ * SVGAnimatedPoints interface, but that is quite different to
+ * DOMSVGAnimatedLengthList, since it is inherited by elements rather than
+ * elements having members of that type.) As a consequence, much of the logic
+ * that would otherwise be in DOMSVGAnimatedPointList (and is in
+ * DOMSVGAnimatedLengthList) is contained in this class.
+ *
+ * This class is strongly intertwined with DOMSVGPoint. Our DOMSVGPoint
+ * items are friends of us and responsible for nulling out our pointers to
+ * them when they die.
+ *
+ * Our DOM items are created lazily on demand as and when script requests them.
+ */
+class DOMSVGPointList final : public nsISupports,
+                              public nsWrapperCache
+{
+  friend class AutoChangePointListNotifier;
+  friend class nsISVGPoint;
+  friend class mozilla::DOMSVGPoint;
+
+public:
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(DOMSVGPointList)
+
+  virtual JSObject* WrapObject(JSContext *cx, JS::Handle<JSObject*> aGivenProto) override;
+
+  nsISupports* GetParentObject()
+  {
+    return static_cast<nsIContent*>(mElement);
+  }
+
+  /**
+   * Factory method to create and return a DOMSVGPointList wrapper
+   * for a given internal SVGPointList object. The factory takes care
+   * of caching the object that it returns so that the same object can be
+   * returned for the given SVGPointList each time it is requested.
+   * The cached object is only removed from the cache when it is destroyed due
+   * to there being no more references to it or to any of its descendant
+   * objects. If that happens, any subsequent call requesting the DOM wrapper
+   * for the SVGPointList will naturally result in a new
+   * DOMSVGPointList being returned.
+   *
+   * It's unfortunate that aList is a void* instead of a typed argument. This
+   * is because the mBaseVal and mAnimVal members of SVGAnimatedPointList are
+   * of different types - a plain SVGPointList, and a SVGPointList*. We
+   * use the addresses of these members as the key for the hash table, and
+   * clearly SVGPointList* and a SVGPointList** are not the same type.
+   */
+  static already_AddRefed<DOMSVGPointList>
+  GetDOMWrapper(void *aList,
+                nsSVGElement *aElement,
+                bool aIsAnimValList);
+
+  /**
+   * This method returns the DOMSVGPointList wrapper for an internal
+   * SVGPointList object if it currently has a wrapper. If it does
+   * not, then nullptr is returned.
+   */
+  static DOMSVGPointList*
+  GetDOMWrapperIfExists(void *aList);
+
+  /**
+   * 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();
+  }
+
+  /**
+   * WATCH OUT! If you add code to call this on a baseVal wrapper, then you
+   * must also call it on the animVal wrapper too if necessary!! See other
+   * callers!
+   *
+   * Called by internal code to notify us when we need to sync the length of
+   * this DOM list with its internal list. This is called immediately prior to
+   * the length of the internal list being changed so that any DOM list items
+   * that need to be removed from the DOM list can first copy their values from
+   * their internal counterpart.
+   *
+   * The only time this method could fail is on OOM when trying to increase the
+   * length of the DOM list. If that happens then this method simply clears the
+   * list and returns. Callers just proceed as normal, and we simply accept
+   * that the DOM list will be empty (until successfully set to a new value).
+   */
+  void InternalListWillChangeTo(const SVGPointList& aNewValue);
+
+  /**
+   * Returns true if our attribute is animating (in which case our animVal is
+   * not simply a mirror of our baseVal).
+   */
+  bool AttrIsAnimating() const;
+  /**
+   * Returns true if there is an animated list mirroring the base list.
+   */
+  bool AnimListMirrorsBaseList() const;
+
+  uint32_t NumberOfItems() const
+  {
+    if (IsAnimValList()) {
+      Element()->FlushAnimations();
+    }
+    return LengthNoFlush();
+  }
+  void Clear(ErrorResult& aError);
+  already_AddRefed<nsISVGPoint> Initialize(nsISVGPoint& aNewItem,
+                                           ErrorResult& aError);
+  already_AddRefed<nsISVGPoint> GetItem(uint32_t index,
+                                        ErrorResult& error);
+  already_AddRefed<nsISVGPoint> IndexedGetter(uint32_t index, bool& found,
+                                              ErrorResult& error);
+  already_AddRefed<nsISVGPoint> InsertItemBefore(nsISVGPoint& aNewItem,
+                                                 uint32_t aIndex,
+                                                 ErrorResult& aError);
+  already_AddRefed<nsISVGPoint> ReplaceItem(nsISVGPoint& aNewItem,
+                                            uint32_t aIndex,
+                                            ErrorResult& aError);
+  already_AddRefed<nsISVGPoint> RemoveItem(uint32_t aIndex,
+                                           ErrorResult& aError);
+  already_AddRefed<nsISVGPoint> AppendItem(nsISVGPoint& aNewItem,
+                                           ErrorResult& aError)
+  {
+    return InsertItemBefore(aNewItem, LengthNoFlush(), aError);
+  }
+  uint32_t Length() const
+  {
+    return NumberOfItems();
+  }
+
+private:
+
+  /**
+   * Only our static GetDOMWrapper() factory method may create objects of our
+   * type.
+   */
+  DOMSVGPointList(nsSVGElement *aElement, bool aIsAnimValList)
+    : mElement(aElement)
+    , mIsAnimValList(aIsAnimValList)
+  {
+    InternalListWillChangeTo(InternalList()); // Sync mItems
+  }
+
+  ~DOMSVGPointList();
+
+  nsSVGElement* Element() const {
+    return mElement.get();
+  }
+
+  /// Used to determine if this list is the baseVal or animVal list.
+  bool IsAnimValList() const {
+    return mIsAnimValList;
+  }
+
+  /**
+   * Get a reference to this object's corresponding internal SVGPointList.
+   *
+   * To simplify the code we just have this one method for obtaining both
+   * base val and anim val internal lists. This means that anim val lists don't
+   * get const protection, but our setter methods guard against changing
+   * anim val lists.
+   */
+  SVGPointList& InternalList() const;
+
+  SVGAnimatedPointList& InternalAList() const;
+
+  /// Returns the nsISVGPoint at aIndex, creating it if necessary.
+  already_AddRefed<nsISVGPoint> GetItemAt(uint32_t aIndex);
+
+  void MaybeInsertNullInAnimValListAt(uint32_t aIndex);
+  void MaybeRemoveItemFromAnimValListAt(uint32_t aIndex);
+
+  // Weak refs to our nsISVGPoint items. The items are friends and take care
+  // of clearing our pointer to them when they die.
+  FallibleTArray<nsISVGPoint*> mItems;
+
+  // Strong ref to our element to keep it alive. We hold this not only for
+  // ourself, but also for our nsISVGPoint items too.
+  RefPtr<nsSVGElement> mElement;
+
+  bool mIsAnimValList;
+};
+
+} // namespace mozilla
+
+#endif // MOZILLA_DOMSVGPOINTLIST_H__