Enable srcset support in HTMLImageElement

Source/core/html/parser/HTMLParserIdioms.cpp

 /*
  * Copyright (C) 2010 Apple 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:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 11 matching lines @@
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 
 #include <limits>
 #include "core/dom/QualifiedName.h"
 #include "core/html/parser/HTMLIdentifier.h"
 #include "core/platform/Decimal.h"
+#include "weborigin/KURL.h"
 #include "wtf/MathExtras.h"
 #include "wtf/text/AtomicString.h"
 #include "wtf/text/StringBuilder.h"
 
 namespace WebCore {
 
 template <typename CharType>
 static String stripLeadingAndTrailingHTMLSpaces(String string, CharType characters, unsigned length)
 {
     unsigned numLeadingSpaces = 0;
@@ skipping 247 matching lines @@
 bool threadSafeMatch(const QualifiedName& a, const QualifiedName& b)
 {
     return threadSafeEqual(a.localName().impl(), b.localName().impl());
 }
 
 bool threadSafeMatch(const HTMLIdentifier& localName, const QualifiedName& qName)
 {
     return threadSafeEqual(localName.asStringImpl(), qName.localName().impl());
 }
 
+struct ImageWithScale {
+    String imageURL;
+    float scaleFactor;
+    bool operator==(const ImageWithScale& image) const
+    {
+        return scaleFactor == image.scaleFactor && imageURL == image.imageURL;
+    }
+};
+typedef Vector<ImageWithScale> ImageCandidates;
+
+static inline bool compareByScaleFactor(const ImageWithScale& first, const ImageWithScale& second)
+{
+    return first.scaleFactor < second.scaleFactor;
 }
+
+String bestFitSourceForImageAttributes(float deviceScaleFactor, const String& srcAttribute, const String& srcSetAttribute)
+{
+    ImageCandidates imageCandidates;
+
+    const String srcSetAttributeValue = srcSetAttribute.simplifyWhiteSpace(isHTMLSpace);
+    Vector<String> srcSetTokens;
+
+    srcSetAttributeValue.split(',', srcSetTokens);
+    for (size_t i = 0; i < srcSetTokens.size(); ++i) {
+        Vector<String> data;
+        float imgScaleFactor = 1.0;
+        bool validScaleFactor = false;
+
+        srcSetTokens[i].stripWhiteSpace().split(' ', data);
+        // There must be at least one candidate descriptor, and the last one must
+        // be a scale factor. Since we don't support descriptors other than scale,
+        // it's better to discard any rule with such descriptors rather than accept
+        // only the scale data.
+        if (data.size() != 2)
+            continue;
+        if (!data.last().endsWith('x'))
+            continue;
+
+        imgScaleFactor = data.last().substring(0, data.last().length() - 1).toFloat(&validScaleFactor);
+        if (!validScaleFactor)
+            continue;
+
+        ImageWithScale image;
+        image.imageURL = decodeURLEscapeSequences(data[0]);

[cbiesinger, 2013/09/06 22:45:36]

why decode them?

+        image.scaleFactor = imgScaleFactor;
+
+        imageCandidates.append(image);
+    }
+
+    const String src =  srcAttribute.simplifyWhiteSpace(isHTMLSpace);
+    if (!src.isEmpty()) {
+        ImageWithScale image;
+        image.imageURL = decodeURLEscapeSequences(src);

[cbiesinger, 2013/09/06 22:45:36]

same

+        image.scaleFactor = 1.0;
+
+        imageCandidates.append(image);
+    }
+
+    if (imageCandidates.isEmpty())
+        return String();
+
+    std::stable_sort(imageCandidates.begin(), imageCandidates.end(), compareByScaleFactor);
+
+    for (size_t i = 0; i < imageCandidates.size() - 1; ++i) {
+        if (imageCandidates[i].scaleFactor >= deviceScaleFactor)
+            return imageCandidates[i].imageURL;
+    }
+    return imageCandidates.last().imageURL;
+}
+
+}