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

Source/core/dom/Document.cpp

 /*
  * 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, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 376 matching lines @@
     virtual void performTask(ExecutionContext* context) OVERRIDE
     {
         Document* document = toDocument(context);
         if (RefPtr<Element> element = document->autofocusElement()) {
             document->setAutofocusElement(0);
             element->focus();
         }
     }
 };
 
+DocumentVisibilityObserver::DocumentVisibilityObserver(Document& document)
+    : m_document(0)
+{
+    registerObserver(document);
+}
+
+DocumentVisibilityObserver::~DocumentVisibilityObserver()
+{
+    unregisterObserver();
+}
+
+void DocumentVisibilityObserver::unregisterObserver()
+{
+    if (m_document) {
+        m_document->unregisterVisibilityObserver(this);
+        m_document = 0;
+    }
+}
+
+void DocumentVisibilityObserver::registerObserver(Document& document)
+{
+    ASSERT(!m_document);
+    m_document = &document;
+    if (m_document)
+        m_document->registerVisibilityObserver(this);
+}
+
+void DocumentVisibilityObserver::setObservedDocument(Document& document)
+{
+    unregisterObserver();
+    registerObserver(document);
+}
+
 Document::Document(const DocumentInit& initializer, DocumentClassFlags documentClasses)
     : ContainerNode(0, CreateDocument)
     , TreeScope(*this)
     , m_hasNodesWithPlaceholderStyle(false)
     , m_needsNotifyRemoveAllPendingStylesheet(false)
     , m_evaluateMediaQueriesOnStyleRecalc(false)
     , m_pendingSheetLayout(NoLayoutWithPendingSheets)
     , m_frame(initializer.frame())
     , m_domWindow(m_frame ? m_frame->domWindow() : 0)
     , m_import(initializer.import())
@@ skipping 102 matching lines @@
     // m_fetcher.
     m_styleEngine = StyleEngine::create(*this);
 }
 
 Document::~Document()
 {
     ASSERT(!renderView());
     ASSERT(m_ranges.isEmpty());
     ASSERT(!parentTreeScope());
     ASSERT(!hasGuardRefCount());
+    ASSERT(m_visibilityObservers.isEmpty());
 
     if (m_templateDocument)
         m_templateDocument->setTemplateDocumentHost(0); // balanced in templateDocument().
 
     if (Document* ownerDocument = this->ownerDocument())
         ownerDocument->didRemoveEventTargetNode(this);
 
     m_scriptRunner.clear();
 
     removeAllEventListeners();
@@ skipping 869 matching lines @@
 String Document::visibilityState() const
 {
     return pageVisibilityStateString(pageVisibilityState());
 }
 
 bool Document::hidden() const
 {
     return pageVisibilityState() != PageVisibilityStateVisible;
 }
 
-void Document::dispatchVisibilityStateChangeEvent()
+void Document::didChangeVisibilityState()
 {
     dispatchEvent(Event::create(EventTypeNames::visibilitychange));
     // Also send out the deprecated version until it can be removed.
     dispatchEvent(Event::create(EventTypeNames::webkitvisibilitychange));
+
+    PageVisibilityState state = pageVisibilityState();
+    HashSet<DocumentVisibilityObserver*>::const_iterator observerEnd = m_visibilityObservers.end();
+    for (HashSet<DocumentVisibilityObserver*>::const_iterator it = m_visibilityObservers.begin(); it != observerEnd; ++it)
+        (*it)->didChangeVisibilityState(state);
+}
+
+void Document::registerVisibilityObserver(DocumentVisibilityObserver* observer)
+{
+    ASSERT(!m_visibilityObservers.contains(observer));
+    m_visibilityObservers.add(observer);
+}
+
+void Document::unregisterVisibilityObserver(DocumentVisibilityObserver* observer)
+{
+    ASSERT(m_visibilityObservers.contains(observer));
+    m_visibilityObservers.remove(observer);
 }
 
 String Document::nodeName() const
 {
     return "#document";
 }
 
 Node::NodeType Document::nodeType() const
 {
     return DOCUMENT_NODE;
@@ skipping 3896 matching lines @@
     if (!page->focusController().isActive() || !page->focusController().isFocused())
         return false;
     if (Frame* focusedFrame = page->focusController().focusedFrame()) {
         if (focusedFrame->tree().isDescendantOf(frame()))
             return true;
     }
     return false;
 }
 
 } // namespace WebCore