Free temporary GPU and memory resources held by inactive or hidden 2D canvases

Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
@@ skipping 193 matching lines @@
     XHTMLDocumentClass = 1 << 1,
     ImageDocumentClass = 1 << 2,
     PluginDocumentClass = 1 << 3,
     MediaDocumentClass = 1 << 4,
     SVGDocumentClass = 1 << 5,
     XMLDocumentClass = 1 << 6,
 };
 
 typedef unsigned char DocumentClassFlags;
 
+class Document;
+
+class DocumentVisibilityObserver {
+public:
+    DocumentVisibilityObserver(Document&);
+    virtual ~DocumentVisibilityObserver();
+
+    virtual void didChangeVisibilityState(PageVisibilityState) = 0;
+
+    // Classes that inherit Node and DocumentVisibilityObserver must have a
+    // virtual override of Node::didMoveToNewDocument that calls
+    // DocumentVisibilityObserver::setDocument
+    void setObservedDocument(Document&);
+
+private:
+    void registerObserver(Document&);
+    void unregisterObserver();
+    Document* m_document;
+};
+
 class Document : public ContainerNode, public TreeScope, public SecurityContext, public ExecutionContext, public ExecutionContextClient
     , public DocumentSupplementable, public LifecycleContext<Document> {
 public:
     static PassRefPtr<Document> create(const DocumentInit& initializer = DocumentInit())
     {
         return adoptRef(new Document(initializer));
     }
     virtual ~Document();
 
     MediaQueryMatcher& mediaQueryMatcher();
@@ skipping 130 matching lines @@
 
     void setXMLEncoding(const String& encoding) { m_xmlEncoding = encoding; } // read-only property, only to be set from XMLDocumentParser
     void setXMLVersion(const String&, ExceptionState&);
     void setXMLStandalone(bool, ExceptionState&);
     void setHasXMLDeclaration(bool hasXMLDeclaration) { m_hasXMLDeclaration = hasXMLDeclaration ? 1 : 0; }
 
     virtual KURL baseURI() const OVERRIDE FINAL;
 
     String visibilityState() const;
     bool hidden() const;
-    void dispatchVisibilityStateChangeEvent();
+    void didChangeVisibilityState();
 
     PassRefPtr<Node> adoptNode(PassRefPtr<Node> source, ExceptionState&);
 
     PassRefPtr<HTMLCollection> images();
     PassRefPtr<HTMLCollection> embeds();
     PassRefPtr<HTMLCollection> applets();
     PassRefPtr<HTMLCollection> links();
     PassRefPtr<HTMLCollection> forms();
     PassRefPtr<HTMLCollection> anchors();
     PassRefPtr<HTMLCollection> scripts();
@@ skipping 637 matching lines @@
     };
     void maybeHandleHttpRefresh(const String&, HttpRefreshType);
 
     void updateSecurityOrigin(PassRefPtr<SecurityOrigin>);
     PassOwnPtr<LifecycleNotifier<Document> > createLifecycleNotifier();
 
     void setHasViewportUnits() { m_hasViewportUnits = true; }
     bool hasViewportUnits() const { return m_hasViewportUnits; }
     void notifyResizeForViewportUnits();
 
+    void registerVisibilityObserver(DocumentVisibilityObserver*);
+    void unregisterVisibilityObserver(DocumentVisibilityObserver*);
+
 protected:
     Document(const DocumentInit&, DocumentClassFlags = DefaultDocumentClass);
 
     virtual void didUpdateSecurityOrigin() OVERRIDE FINAL;
 
     void clearXMLVersion() { m_xmlVersion = String(); }
 
     virtual void dispose() OVERRIDE;
 
     virtual PassRefPtr<Document> cloneDocumentWithoutChildren();
@@ skipping 274 matching lines @@
 
     RefPtr<Document> m_templateDocument;
     Document* m_templateDocumentHost; // Manually managed weakref (backpointer from m_templateDocument).
 
     Timer<Document> m_didAssociateFormControlsTimer;
     HashSet<RefPtr<Element> > m_associatedFormControls;
 
     HashSet<SVGUseElement*> m_useElementsNeedingUpdate;
 
     bool m_hasViewportUnits;
+
+    HashSet<DocumentVisibilityObserver*> m_visibilityObservers;
 };
 
 inline void Document::notifyRemovePendingSheetIfNeeded()
 {
     if (m_needsNotifyRemoveAllPendingStylesheet)
         didRemoveAllPendingStylesheet();
 }
 
 inline const Document* Document::templateDocument() const
 {
@@ skipping 31 matching lines @@
 inline bool Node::isDocumentNode() const
 {
     return this == document();
 }
 
 Node* eventTargetNodeForDocument(Document*);
 
 } // namespace WebCore
 
 #endif // Document_h