dom/svg/DOMSVGAnimatedTransformList.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef DOM_SVG_DOMSVGANIMATEDTRANSFORMLIST_H_
   8 #define DOM_SVG_DOMSVGANIMATEDTRANSFORMLIST_H_
   9
  10 #include "nsCycleCollectionParticipant.h"
  11 #include "SVGElement.h"
  12 #include "nsWrapperCache.h"
  13 #include "mozilla/Attributes.h"
  14 #include "mozilla/RefPtr.h"
  15
  16 namespace mozilla {
  17
  18 class SVGAnimatedTransformList;
  19
  20 namespace dom {
  21
  22 class DOMSVGTransformList;
  23
  24 /**
  25  * Class DOMSVGAnimatedTransformList
  26  *
  27  * This class is used to create the DOM tearoff objects that wrap internal
  28  * SVGAnimatedTransformList objects.
  29  *
  30  * See the architecture comment in DOMSVGAnimatedLengthList.h (that's
  31  * LENGTH list). The comment for that class largly applies to this one too
  32  * and will go a long way to helping you understand the architecture here.
  33  *
  34  * This class is strongly intertwined with DOMSVGTransformList and
  35  * DOMSVGTransform.
  36  * Our DOMSVGTransformList base and anim vals are friends and take care of
  37  * nulling out our pointers to them when they die (making our pointers to them
  38  * true weak refs).
  39  */
  40 class DOMSVGAnimatedTransformList final : public nsWrapperCache {
  41   friend class DOMSVGTransformList;
  42
  43  public:
  44   NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(
  45       DOMSVGAnimatedTransformList)
  46   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_NATIVE_CLASS(
  47       DOMSVGAnimatedTransformList)
  48
  49   /**
  50    * Factory method to create and return a DOMSVGAnimatedTransformList wrapper
  51    * for a given internal SVGAnimatedTransformList object. The factory takes
  52    * care of caching the object that it returns so that the same object can be
  53    * returned for the given SVGAnimatedTransformList each time it is
  54    * requested. The cached object is only removed from the cache when it is
  55    * destroyed due to there being no more references to it or to any of its
  56    * descendant objects. If that happens, any subsequent call requesting the DOM
  57    * wrapper for the SVGAnimatedTransformList will naturally result in a new
  58    * DOMSVGAnimatedTransformList being returned.
  59    */
  60   static already_AddRefed<DOMSVGAnimatedTransformList> GetDOMWrapper(
  61       SVGAnimatedTransformList* aList, SVGElement* aElement);
  62
  63   /**
  64    * This method returns the DOMSVGAnimatedTransformList wrapper for an internal
  65    * SVGAnimatedTransformList object if it currently has a wrapper. If it does
  66    * not, then nullptr is returned.
  67    */
  68   static DOMSVGAnimatedTransformList* GetDOMWrapperIfExists(
  69       SVGAnimatedTransformList* aList);
  70
  71   /**
  72    * Called by internal code to notify us when we need to sync the length of
  73    * our baseVal DOM list with its internal list. This is called just prior to
  74    * the length of the internal baseVal list being changed so that any DOM list
  75    * items that need to be removed from the DOM list can first get their values
  76    * from their internal counterpart.
  77    *
  78    * The only time this method could fail is on OOM when trying to increase the
  79    * length of the DOM list. If that happens then this method simply clears the
  80    * list and returns. Callers just proceed as normal, and we simply accept
  81    * that the DOM list will be empty (until successfully set to a new value).
  82    */
  83   void InternalBaseValListWillChangeLengthTo(uint32_t aNewLength);
  84   void InternalAnimValListWillChangeLengthTo(uint32_t aNewLength);
  85
  86   /**
  87    * Returns true if our attribute is animating (in which case our animVal is
  88    * not simply a mirror of our baseVal).
  89    */
  90   bool IsAnimating() const;
  91
  92   // WebIDL
  93   SVGElement* GetParentObject() const { return mElement; }
  94   JSObject* WrapObject(JSContext* aCx,
  95                        JS::Handle<JSObject*> aGivenProto) override;
  96   // These aren't weak refs because mBaseVal and mAnimVal are weak
  97   already_AddRefed<DOMSVGTransformList> BaseVal();
  98   already_AddRefed<DOMSVGTransformList> AnimVal();
  99
 100  private:
 101   /**
 102    * Only our static GetDOMWrapper() factory method may create objects of our
 103    * type.
 104    */
 105   explicit DOMSVGAnimatedTransformList(SVGElement* aElement)
 106       : mBaseVal(nullptr), mAnimVal(nullptr), mElement(aElement) {}
 107
 108   ~DOMSVGAnimatedTransformList();
 109
 110   /// Get a reference to this DOM wrapper object's internal counterpart.
 111   SVGAnimatedTransformList& InternalAList();
 112   const SVGAnimatedTransformList& InternalAList() const;
 113
 114   // Weak refs to our DOMSVGTransformList baseVal/animVal objects. These objects
 115   // are friends and take care of clearing these pointers when they die, making
 116   // these true weak references.
 117   DOMSVGTransformList* mBaseVal;
 118   DOMSVGTransformList* mAnimVal;
 119
 120   // Strong ref to our element to keep it alive. We hold this not only for
 121   // ourself, but also for our base/animVal and all of their items.
 122   RefPtr<SVGElement> mElement;
 123 };
 124
 125 }  // namespace dom
 126 }  // namespace mozilla
 127
 128 #endif  // DOM_SVG_DOMSVGANIMATEDTRANSFORMLIST_H_