Have srcset respond to viewport changes

Source/core/html/HTMLImageElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 36 matching lines @@
 
 using namespace HTMLNames;
 
 HTMLImageElement::HTMLImageElement(Document& document, HTMLFormElement* form, bool createdByParser)
     : HTMLElement(imgTag, document)
     , m_imageLoader(HTMLImageLoader::create(this))
     , m_compositeOperator(CompositeSourceOver)
     , m_imageDevicePixelRatio(1.0f)
     , m_formWasSetByParser(false)
     , m_elementCreatedByParser(createdByParser)
+    , m_intrinsicSizingViewportDependant(false)
+    , m_effectiveSizeViewportDependant(false)
+    , m_viewportListener(ImageViewportChangeListener::create(this))
 {
     ScriptWrappable::init(this);
     if (form && form->inDocument()) {
 #if ENABLE(OILPAN)
         m_form = form;
 #else
         m_form = form->createWeakPtr();
 #endif
         m_formWasSetByParser = true;
         m_form->associate(*this);
         m_form->didAssociateByParser();
     }
 }
 
 PassRefPtrWillBeRawPtr<HTMLImageElement> HTMLImageElement::create(Document& document)
 {
     return adoptRefWillBeNoop(new HTMLImageElement(document));
 }
 
 PassRefPtrWillBeRawPtr<HTMLImageElement> HTMLImageElement::create(Document& document, HTMLFormElement* form, bool createdByParser)
 {
     return adoptRefWillBeNoop(new HTMLImageElement(document, form, createdByParser));
 }
 
 HTMLImageElement::~HTMLImageElement()
 {
+    document().viewportChangeNotifier().removeListener(m_viewportListener);

[haraken, 2014/07/11 06:10:21]

In oilpan, destructors cannot touch other on-heap objects.

I think you can make ViewportChangeNotifier::m_listeners a hash set of weak
members, and ask oilpan's GC to automatically clear entries of dead elements.

 #if !ENABLE(OILPAN)
     if (m_form)
         m_form->disassociate(*this);
 #endif
 }
 
 void HTMLImageElement::trace(Visitor* visitor)
 {
     visitor->trace(m_imageLoader);
     visitor->trace(m_form);
@@ skipping 81 matching lines @@
 #endif
     }
 }
 
 void HTMLImageElement::setBestFitURLAndDPRFromImageCandidate(const ImageCandidate& candidate)
 {
     m_bestFitImageURL = candidate.url();
     float candidateDensity = candidate.density();
     if (candidateDensity >= 0)
         m_imageDevicePixelRatio = 1.0 / candidateDensity;
+    if (candidate.resourceWidth() > 0)
+        m_intrinsicSizingViewportDependant = true;
     if (renderer() && renderer()->isImage())
         toRenderImage(renderer())->setImageDevicePixelRatio(m_imageDevicePixelRatio);
 }
 
 void HTMLImageElement::parseAttribute(const QualifiedName& name, const AtomicString& value)
 {
     if (name == altAttr) {
         if (renderer() && renderer()->isImage())
             toRenderImage(renderer())->updateAltText();
     } else if (name == srcAttr || name == srcsetAttr || name == sizesAttr) {
@@ skipping 45 matching lines @@
         String srcset = source->fastGetAttribute(srcsetAttr);
         if (srcset.isEmpty())
             continue;
         String type = source->fastGetAttribute(typeAttr);
         if (!type.isEmpty() && !supportedImageType(type))
             continue;
 
         if (!source->mediaQueryMatches())
             continue;
 
-        unsigned effectiveSize = SizesAttributeParser::findEffectiveSize(source->fastGetAttribute(sizesAttr), MediaValuesDynamic::create(document()));
+        unsigned effectiveSize = SizesAttributeParser::findEffectiveSize(source->fastGetAttribute(sizesAttr), MediaValuesDynamic::create(document()), m_effectiveSizeViewportDependant);
         ImageCandidate candidate = bestFitSourceForSrcsetAttribute(document().devicePixelRatio(), effectiveSize, source->fastGetAttribute(srcsetAttr));
         if (candidate.isEmpty())
             continue;
         return candidate;
     }
     return ImageCandidate();
 }
 
 RenderObject* HTMLImageElement::createRenderer(RenderStyle* style)
 {
@@ skipping 302 matching lines @@
         ImageCandidate candidate = findBestFitImageFromPictureParent();
         if (!candidate.isEmpty()) {
             setBestFitURLAndDPRFromImageCandidate(candidate);
             foundURL = true;
         }
     }
 
     if (!foundURL) {
         unsigned effectiveSize = 0;
         if (RuntimeEnabledFeatures::pictureSizesEnabled())
-            effectiveSize = SizesAttributeParser::findEffectiveSize(fastGetAttribute(sizesAttr), MediaValuesDynamic::create(document()));
+            effectiveSize = SizesAttributeParser::findEffectiveSize(fastGetAttribute(sizesAttr), MediaValuesDynamic::create(document()), m_effectiveSizeViewportDependant);
         ImageCandidate candidate = bestFitSourceForImageAttributes(document().devicePixelRatio(), effectiveSize, fastGetAttribute(srcAttr), fastGetAttribute(srcsetAttr));
         setBestFitURLAndDPRFromImageCandidate(candidate);
     }
+    if (m_intrinsicSizingViewportDependant && m_effectiveSizeViewportDependant)
+        document().viewportChangeNotifier().addListener(m_viewportListener);
     imageLoader().updateFromElement(behavior);
 }
 
 const KURL& HTMLImageElement::sourceURL() const
 {
     return cachedImage()->response().url();
 }
 
 }