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Unified Diff: Source/core/html/parser/HTMLSrcsetParser.cpp

Issue 23861003: Enable srcset support in HTMLImageElement (Closed) Base URL: https://chromium.googlesource.com/chromium/blink.git@master
Patch Set: Fixed a flaky test Created 7 years, 3 months ago
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Index: Source/core/html/parser/HTMLSrcsetParser.cpp
diff --git a/Source/core/html/parser/HTMLSrcsetParser.cpp b/Source/core/html/parser/HTMLSrcsetParser.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..3be87fa29dc883b75bae039397c8ec8d7057be87
--- /dev/null
+++ b/Source/core/html/parser/HTMLSrcsetParser.cpp
@@ -0,0 +1,171 @@
+/*
+ * 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
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ * * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+#include "core/html/parser/HTMLSrcsetParser.h"
+
+#include "core/html/parser/HTMLParserIdioms.h"
+#include "core/platform/ParsingUtilities.h"
+
+namespace WebCore {
+
+static bool compareByScaleFactor(const ImageCandidate& first, const ImageCandidate& second)
+{
+ return first.scaleFactor() < second.scaleFactor();
+}
+
+// http://www.whatwg.org/specs/web-apps/current-work/multipage/embedded-content-1.html#processing-the-image-candidates
+template<typename CharType>
+static void parseImageCandidatesFromSrcsetAttribute(const String& attribute, const CharType* attributeStart, unsigned length, Vector<ImageCandidate>& imageCandidates)
+{
+ const CharType* position = attributeStart;
+ const CharType* attributeEnd = position + length;
+
+ while (position < attributeEnd) {
+ float imgScaleFactor = 1.0;
+ // 4. Splitting loop: Skip whitespace.
+ skipWhile<CharType, isHTMLSpace<CharType> >(position, attributeEnd);
+ if (position == attributeEnd)
+ break;
+ const CharType* imageURLStart = position;
+
+ // If The current candidate is either totally empty or only contains space, skipping.
+ if (*position == ',') {
+ ++position;
+ continue;
+ }
+ // 5. Collect a sequence of characters that are not space characters, and let that be url.
+ ++position;
+ skipUntil<CharType, isHTMLSpace<CharType> >(position, attributeEnd);
+ const CharType* imageURLEnd = position;
+
+ if (position != attributeEnd && *(position - 1) == ',') {
+ --imageURLEnd;
+ } else {
+ // 7. Collect a sequence of characters that are not "," (U+002C) characters, and let that be descriptors.
+ skipWhile<CharType, isHTMLSpace<CharType> >(position, attributeEnd);
+ const CharType* qualifierStart = position;
+ if (position != attributeEnd && *position != ',') {
+ // This part differs from the spec as the current implementation only supports pixel density descriptors for now.
+ skipUntil<CharType, isHTMLSpaceOrComma<CharType> >(position, attributeEnd);
+ const CharType* qualifierEnd = position;
+ ASSERT(qualifierEnd > qualifierStart);
+ // Make sure there are no other descriptors
+ skipWhile<CharType, isHTMLSpace<CharType> >(position, attributeEnd);
+ // If the first non-html-space character after the scale modifier is not a comma,
+ // the current candidate is an invalid input.
+ if (position != attributeEnd && *position != ',') {
+ skipUntil<CharType>(position, attributeEnd, ',');
+ ++position;
+ continue;
+ }
+ // If the current qualifier is not an 'x', the resource is ignored
+ if (*(qualifierEnd - 1) != 'x')
+ continue;
+
+ bool validScaleFactor = false;
+ unsigned scaleFactorLengthWithoutUnit = qualifierEnd - qualifierStart - 1;
+ imgScaleFactor = charactersToFloat(qualifierStart, scaleFactorLengthWithoutUnit, &validScaleFactor);
+
+ if (!validScaleFactor)
+ continue;
+ }
+ }
+
+ imageCandidates.append(ImageCandidate(attribute, imageURLStart - attributeStart, imageURLEnd - imageURLStart, imgScaleFactor));
+ // 11. Return to the step labeled splitting loop.
+ }
+}
+
+static void parseImageCandidatesFromSrcsetAttribute(const String& attribute, Vector<ImageCandidate>& imageCandidates)
+{
+ 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, Vector<ImageCandidate>& imageCandidates)
+{
+ if (imageCandidates.isEmpty())
+ return ImageCandidate();
+
+ std::stable_sort(imageCandidates.begin(), imageCandidates.end(), compareByScaleFactor);
+
+ unsigned i;
+ for (i = 0; i < imageCandidates.size() - 1; ++i) {
+ if (imageCandidates[i].scaleFactor() >= deviceScaleFactor)
+ break;
+ }
+ return imageCandidates[i];
+}
+
+ImageCandidate bestFitSourceForSrcsetAttribute(float deviceScaleFactor, const String& srcsetAttribute)
+{
+ Vector<ImageCandidate> imageCandidates;
+
+ parseImageCandidatesFromSrcsetAttribute(srcsetAttribute, imageCandidates);
+
+ return pickBestImageCandidate(deviceScaleFactor, imageCandidates);
+}
+
+String bestFitSourceForImageAttributes(float deviceScaleFactor, const String& srcAttribute, const String& srcsetAttribute)
+{
+ if (srcsetAttribute.isNull())
+ return srcAttribute;
+
+ Vector<ImageCandidate> imageCandidates;
+
+ parseImageCandidatesFromSrcsetAttribute(srcsetAttribute, imageCandidates);
+
+ if (!srcAttribute.isEmpty())
+ imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), 1.0));
+
+ return pickBestImageCandidate(deviceScaleFactor, imageCandidates).toString();
+}
+
+String bestFitSourceForImageAttributes(float deviceScaleFactor, const String& srcAttribute, ImageCandidate& srcsetImageCandidate)
+{
+ if (srcsetImageCandidate.isEmpty())
+ return srcAttribute;
+
+ Vector<ImageCandidate> imageCandidates;
+ imageCandidates.append(srcsetImageCandidate);
+
+ if (!srcAttribute.isEmpty())
+ imageCandidates.append(ImageCandidate(srcAttribute, 0, srcAttribute.length(), 1.0));
+
+ return pickBestImageCandidate(deviceScaleFactor, imageCandidates).toString();
+}
+
+}
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