Have srcset respond to viewport changes

Source/core/html/HTMLImageElement.cpp

Index: Source/core/html/HTMLImageElement.cpp
diff --git a/Source/core/html/HTMLImageElement.cpp b/Source/core/html/HTMLImageElement.cpp
index ceeb1ede0923b0b2912ddc8e3cd7f60df49ccb64..1174afb4508b1230037f0702dd178084a700b4a2 100644
--- a/Source/core/html/HTMLImageElement.cpp
+++ b/Source/core/html/HTMLImageElement.cpp
@@ -54,6 +54,9 @@ HTMLImageElement::HTMLImageElement(Document& document, HTMLFormElement* form, bo
     , 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()) {
@@ -80,6 +83,7 @@ PassRefPtrWillBeRawPtr<HTMLImageElement> HTMLImageElement::create(Document& docu
 
 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);
@@ -181,6 +185,8 @@ void HTMLImageElement::setBestFitURLAndDPRFromImageCandidate(const ImageCandidat
     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);
 }
@@ -246,7 +252,7 @@ ImageCandidate HTMLImageElement::findBestFitImageFromPictureParent()
         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;
@@ -569,10 +575,12 @@ void HTMLImageElement::selectSourceURL(ImageLoader::UpdateFromElementBehavior be
     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);
 }