Use SizesAttributeParser to get the right srcset resource

Source/core/html/parser/HTMLSrcsetParser.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 124 matching lines @@
 {
     if (attribute.isNull())
         return;
 
     if (attribute.is8Bit())
         parseImageCandidatesFromSrcsetAttribute<LChar>(attribute, attribute.characters8(), attribute.length(), imageCandidates);
     else
         parseImageCandidatesFromSrcsetAttribute<UChar>(attribute, attribute.characters16(), attribute.length(), imageCandidates);
 }
 
-static ImageCandidate pickBestImageCandidate(float deviceScaleFactor, int effectiveSize, Vector<ImageCandidate>& imageCandidates)
+static ImageCandidate pickBestImageCandidate(float deviceScaleFactor, unsigned sourceSize, Vector<ImageCandidate>& imageCandidates)
 {
     bool ignoreSrc = false;
     if (imageCandidates.isEmpty())
         return ImageCandidate();
 
     // http://picture.responsiveimages.org/#normalize-source-densities
     for (Vector<ImageCandidate>::iterator it = imageCandidates.begin(); it != imageCandidates.end(); ++it) {
         if (it->resourceWidth() > 0) {
-            it->setScaleFactor((float)it->resourceWidth() / (float)effectiveSize);
+            it->setScaleFactor((float)it->resourceWidth() / (float)sourceSize);
             ignoreSrc = true;
         }
     }
 
     std::stable_sort(imageCandidates.begin(), imageCandidates.end(), compareByScaleFactor);
 
     unsigned i;
     for (i = 0; i < imageCandidates.size() - 1; ++i) {
         if ((imageCandidates[i].scaleFactor() >= deviceScaleFactor) && (!ignoreSrc || !imageCandidates[i].srcOrigin()))
             break;
     }
 
     float winningScaleFactor = imageCandidates[i].scaleFactor();
     unsigned winner = i;
     // 16. If an entry b in candidates has the same associated ... pixel density as an earlier entry a in candidates,
     // then remove entry b
     while ((i > 0) && (imageCandidates[--i].scaleFactor() == winningScaleFactor))
         winner = i;
 
     return imageCandidates[winner];
 }
 
-ImageCandidate bestFitSourceForSrcsetAttribute(float deviceScaleFactor, int effectiveSize, const String& srcsetAttribute)
+ImageCandidate bestFitSourceForSrcsetAttribute(float deviceScaleFactor, unsigned sourceSize, const String& srcsetAttribute)
 {
     Vector<ImageCandidate> imageCandidates;
 
     parseImageCandidatesFromSrcsetAttribute(srcsetAttribute, imageCandidates);
 
-    return pickBestImageCandidate(deviceScaleFactor, effectiveSize, imageCandidates);
+    return pickBestImageCandidate(deviceScaleFactor, sourceSize, imageCandidates);
 }
 
-ImageCandidate bestFitSourceForImageAttributes(float deviceScaleFactor, int effectiveSize, const String& srcAttribute, const String& srcsetAttribute)
+ImageCandidate bestFitSourceForImageAttributes(float deviceScaleFactor, unsigned sourceSize, const String& srcAttribute, const String& srcsetAttribute)
 {
     DescriptorParsingResult defaultResult;
     defaultResult.scaleFactor = 1.0;
 
     if (srcsetAttribute.isNull()) {
         if (srcAttribute.isNull())
             return ImageCandidate();
         return ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult, ImageCandidate::SrcOrigin);
     }
 
     Vector<ImageCandidate> imageCandidates;
 
     parseImageCandidatesFromSrcsetAttribute(srcsetAttribute, imageCandidates);
 
-    if (!srcAttribute.isEmpty())
+    if (!srcAttribute.isNull() && !srcAttribute.isEmpty())

[eseidel, 2014/04/20 21:27:43]

!isEmpty should be the same...

         imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult, ImageCandidate::SrcOrigin));
 
-    return pickBestImageCandidate(deviceScaleFactor, effectiveSize, imageCandidates);
+    return pickBestImageCandidate(deviceScaleFactor, sourceSize, imageCandidates);
 }
 
-String bestFitSourceForImageAttributes(float deviceScaleFactor, int effectiveSize, const String& srcAttribute, ImageCandidate& srcsetImageCandidate)
+String bestFitSourceForImageAttributes(float deviceScaleFactor, unsigned sourceSize, const String& srcAttribute, ImageCandidate& srcsetImageCandidate)
 {
     DescriptorParsingResult defaultResult;
     defaultResult.scaleFactor = 1.0;
 
     if (srcsetImageCandidate.isEmpty())
         return srcAttribute;
 
     Vector<ImageCandidate> imageCandidates;
     imageCandidates.append(srcsetImageCandidate);
 
-    if (!srcAttribute.isEmpty())
+    if (!srcAttribute.isNull() && !srcAttribute.isEmpty())
         imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), defaultResult, ImageCandidate::SrcOrigin));

[eseidel, 2014/04/20 21:27:43]

Same thing, I think you have some confusiong with null vs. empty.

null means the impl is set to 0.  Often used to mean something has never been
set at all.

isEmpty means that either it's null, or that its == "".

The String::emptyString() aka String("") isEmpty(), but is not null.

[Yoav Weiss, 2014/04/20 21:48:03]

For some reason I thought isEmpty is not safe to call when String is NULL. Got
it now.

 
-    return pickBestImageCandidate(deviceScaleFactor, effectiveSize, imageCandidates).toString();
+    return pickBestImageCandidate(deviceScaleFactor, sourceSize, imageCandidates).toString();
 }
 
 }