Use srcset's resource pixel density to determine intrinsic size

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 29 matching lines @@
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
 HTMLImageElement::HTMLImageElement(const QualifiedName& tagName, Document& document, HTMLFormElement* form)
     : HTMLElement(tagName, document)
     , m_imageLoader(this)
     , m_form(form)
     , m_compositeOperator(CompositeSourceOver)
+    , m_intrinsicSizeFactor(1.0f)
 {
     ASSERT(hasTagName(imgTag));
     ScriptWrappable::init(this);
     if (form)
         form->registerImgElement(this);
 }
 
 PassRefPtr<HTMLImageElement> HTMLImageElement::create(Document& document)
 {
     return adoptRef(new HTMLImageElement(imgTag, document));
@@ skipping 54 matching lines @@
     return m_bestFitImageURL.isNull() ? fastGetAttribute(srcAttr) : m_bestFitImageURL;
 }
 
 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) {
         if (RuntimeEnabledFeatures::srcsetEnabled())
-            m_bestFitImageURL = bestFitSourceForImageAttributes(document().devicePixelRatio(), fastGetAttribute(srcAttr), fastGetAttribute(srcsetAttr));
+            m_bestFitImageURL = bestFitSourceForImageAttributes(document().devicePixelRatio(), fastGetAttribute(srcAttr), fastGetAttribute(srcsetAttr), m_intrinsicSizeFactor);
         m_imageLoader.updateFromElementIgnoringPreviousError();
     }
     else if (name == usemapAttr)
         setIsLink(!value.isNull());
     else if (name == onbeforeloadAttr)
         setAttributeEventListener(EventNames::beforeload, createAttributeEventListener(this, name, value));
     else if (name == compositeAttr) {
         // FIXME: images don't support blend modes in their compositing attribute.
         BlendMode blendOp = BlendModeNormal;
         if (!parseCompositeAndBlendOperator(value, m_compositeOperator, blendOp))
@@ skipping 14 matching lines @@
     return alt;
 }
 
 RenderObject* HTMLImageElement::createRenderer(RenderStyle* style)
 {
     if (style->hasContent())
         return RenderObject::createObject(this, style);
 
     RenderImage* image = new RenderImage(this);
     image->setImageResource(RenderImageResource::create());
+    image->setIntrinsicSizeFactor(m_intrinsicSizeFactor);

[pdr., 2013/10/11 05:17:33]

I'm not sure this will work for dynamic changes. For example:
<img srcset="mustard.png 2x">
<script>
document.body.onload = function() {
  var img = document.getElementsByTagName('img')[0];
  img.srcset = "ketchup.png 3x";
}
</script>

In this example, we wont create a new RenderImage but m_intrinsicSizeFactor will
change. One solution may be to set the value in parseAttribute if there's
already a renderer, similar to how the alt text is updated.

[Yoav Weiss, 2013/10/11 07:22:32]

Good catch! Will fix.

     return image;
 }
 
 bool HTMLImageElement::canStartSelection() const
 {
     if (shadow())
         return HTMLElement::canStartSelection();
 
     return false;
 }
@@ skipping 208 matching lines @@
 
 Image* HTMLImageElement::imageContents()
 {
     if (!m_imageLoader.imageComplete())
         return 0;
 
     return m_imageLoader.image()->image();
 }
 
 }