DOM-based SVG resource tracking

third_party/WebKit/Source/core/svg/SVGTreeScopeResources.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SVGTreeScopeResources_h
 #define SVGTreeScopeResources_h
 
+#include "core/dom/IdTargetObserver.h"
 #include "platform/heap/Handle.h"
 #include "platform/wtf/Forward.h"
 #include "platform/wtf/HashMap.h"
 #include "platform/wtf/HashSet.h"
 #include "platform/wtf/text/AtomicStringHash.h"
 
 namespace blink {
 
 class Element;
+class LayoutSVGResourceContainer;
+class SVGElement;
 class TreeScope;
-class LayoutSVGResourceContainer;
 
 // This class keeps track of SVG resources and pending references to such for a
 // TreeScope. It's per-TreeScope because that matches the lookup scope of an
 // element's id (which is used to identify a resource.)
 class SVGTreeScopeResources
     : public GarbageCollectedFinalized<SVGTreeScopeResources> {
   WTF_MAKE_NONCOPYABLE(SVGTreeScopeResources);
 
  public:
   explicit SVGTreeScopeResources(TreeScope*);
   ~SVGTreeScopeResources();
 
-  void UpdateResource(const AtomicString& id, LayoutSVGResourceContainer*);
-  void UpdateResource(const AtomicString& old_id,
-                      const AtomicString& new_id,
-                      LayoutSVGResourceContainer*);
-  void RemoveResource(const AtomicString& id, LayoutSVGResourceContainer*);
-  LayoutSVGResourceContainer* ResourceById(const AtomicString& id) const;
+  class Resource : public IdTargetObserver {
+   public:
+    Resource(TreeScope&, const AtomicString& id);
+    ~Resource() override;
 
-  // Pending resources are such which are referenced by any object in the SVG
-  // document, but do NOT exist yet. For instance, dynamically built gradients
-  // / patterns / clippers...
-  void AddPendingResource(const AtomicString& id, Element&);
-  bool IsElementPendingResource(Element&, const AtomicString& id) const;
-  void NotifyResourceAvailable(const AtomicString& id);
-  void RemoveElementFromPendingResources(Element&);
+    Element* Target() const { return target_; }
+    LayoutSVGResourceContainer* ResourceContainer() const;
+
+    void AddWatch(SVGElement&);
+    void RemoveWatch(SVGElement&);
+
+    bool IsEmpty() const;
+
+    DECLARE_TRACE();
+
+    void NotifyResourceClients();
+
+   private:
+    void IdTargetChanged() override;
+
+    Member<TreeScope> tree_scope_;
+    Member<Element> target_;
+    HeapHashSet<Member<SVGElement>> pending_clients_;
+  };
+  Resource* ResourceForId(const AtomicString& id);
+  Resource* ExistingResourceForId(const AtomicString& id) const;
+
+  void RemoveUnreferencedResources();
+  void RemoveWatchesForElement(SVGElement&);
 
   DECLARE_TRACE();
 
  private:
-  void ClearHasPendingResourcesIfPossible(Element&);
-
-  using SVGPendingElements = HeapHashSet<Member<Element>>;
-  using ResourceMap = HashMap<AtomicString, LayoutSVGResourceContainer*>;
-
-  void RegisterResource(const AtomicString& id, LayoutSVGResourceContainer*);
-  void UnregisterResource(ResourceMap::iterator);
-  void NotifyPendingClients(const AtomicString& id);
-
-  ResourceMap resources_;
-  // Resources that are pending.
-  HeapHashMap<AtomicString, Member<SVGPendingElements>> pending_resources_;
+  HeapHashMap<AtomicString, Member<Resource>> resources_;
   Member<TreeScope> tree_scope_;
 };
 
 }  // namespace blink
 
 #endif  // SVGTreeScopeResources_h