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

Source/core/html/HTMLCanvasElement.h

 /*
  * Copyright (C) 2004, 2006, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alp Toker <alp@atoker.com>
  * Copyright (C) 2010 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 13 matching lines @@
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef HTMLCanvasElement_h
 #define HTMLCanvasElement_h
 
 #include "core/html/HTMLElement.h"
 #include "platform/geometry/FloatRect.h"
 #include "platform/geometry/IntSize.h"
+#include "platform/graphics/Canvas2DLayerBridge.h"
 #include "wtf/Forward.h"
 
 #define DefaultInterpolationQuality InterpolationMedium
 
 namespace WebCore {
 
 class AffineTransform;
 class CanvasContextAttributes;
 class CanvasRenderingContext;
 class GraphicsContext;
 class GraphicsContextStateSaver;
 class HTMLCanvasElement;
 class Image;
 class ImageData;
 class ImageBuffer;
 class ImageBufferSurface;
 class IntSize;
 
 class CanvasObserver {
 public:
     virtual ~CanvasObserver() { }
 
     virtual void canvasChanged(HTMLCanvasElement*, const FloatRect& changedRect) = 0;
     virtual void canvasResized(HTMLCanvasElement*) = 0;
     virtual void canvasDestroyed(HTMLCanvasElement*) = 0;
 };
 
-class HTMLCanvasElement FINAL : public HTMLElement {
+class HTMLCanvasElement FINAL : public HTMLElement, public DocumentVisibilityObserver {
 public:
     static PassRefPtr<HTMLCanvasElement> create(Document&);
     virtual ~HTMLCanvasElement();
 
     void addObserver(CanvasObserver*);
     void removeObserver(CanvasObserver*);
 
     // Attributes and functions exposed to script
     int width() const { return size().width(); }
     int height() const { return size().height(); }
@@ skipping 48 matching lines @@
     AffineTransform baseTransform() const;
 
     bool is3D() const;
 
     bool hasImageBuffer() const { return m_imageBuffer.get(); }
 
     bool shouldAccelerate(const IntSize&) const;
 
     virtual InsertionNotificationRequest insertedInto(ContainerNode*) OVERRIDE;
 
+    // DocumentVisibilityObserver implementation
+    virtual void didChangeVisibilityState(PageVisibilityState) OVERRIDE;
+
+protected:
+    virtual void didMoveToNewDocument(Document& oldDocument) OVERRIDE;
+
 private:
     explicit HTMLCanvasElement(Document&);
 
     virtual void parseAttribute(const QualifiedName&, const AtomicString&) OVERRIDE;
     virtual RenderObject* createRenderer(RenderStyle*) OVERRIDE;
     virtual bool areAuthorShadowsAllowed() const OVERRIDE { return false; }
 
     void reset();
 
     PassOwnPtr<ImageBufferSurface> createImageBufferSurface(const IntSize& deviceSize, int* msaaSampleCount);
@@ skipping 31 matching lines @@
 
     mutable RefPtr<Image> m_presentedImage;
     mutable RefPtr<Image> m_copiedImage; // FIXME: This is temporary for platforms that have to copy the image buffer to render (and for CSSCanvasValue).
 };
 
 DEFINE_NODE_TYPE_CASTS(HTMLCanvasElement, hasTagName(HTMLNames::canvasTag));
 
 } //namespace
 
 #endif