Add feature extraction for distillability to Blink

third_party/WebKit/Source/core/dom/DocumentStatisticsCollector.cpp

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "DocumentStatisticsCollector.h"
+
+#include "core/HTMLNames.h"
+#include "core/InputTypeNames.h"
+#include "core/css/CSSComputedStyleDeclaration.h"

[esprehn, 2015/11/03 07:45:10]

don't need this.

[wychen, 2015/11/03 08:59:49]

Done.

+#include "core/dom/ElementTraversal.h"
+#include "core/dom/NodeComputedStyle.h"
+#include "core/editing/iterators/TextIterator.h"

[esprehn, 2015/11/03 07:45:10]

don't need this.

[wychen, 2015/11/03 08:59:49]

Done.

+#include "core/frame/FrameHost.h"
+#include "core/html/HTMLHeadElement.h"
+#include "core/html/HTMLInputElement.h"
+#include "core/html/HTMLMetaElement.h"
+#include "public/platform/Platform.h"
+#include "public/platform/WebDistillability.h"
+#include "wtf/text/StringBuilder.h"
+#include "wtf/text/StringImpl.h"

[esprehn, 2015/11/03 07:45:10]

you don't need StringImpl, StringBuilder

[wychen, 2015/11/03 08:59:48]

Done.

Just curious, did you use IDE to check unnecessary headers, or you just know it?

+
+namespace blink {
+
+using namespace HTMLNames;
+
+namespace {
+
+// Saturate the length of a paragraph to save time.
+const int kTextContentLengthSaturation = 1000;
+
+unsigned textContentLengthSaturated(Element& root)
+{
+    unsigned length = 0;
+    // This skips shadow dom intentionally, to match the JavaScript implementation.

[esprehn, 2015/11/03 07:45:10]

Why?

[wychen, 2015/11/03 08:59:48]

Done.

+    for (Node& node : NodeTraversal::inclusiveDescendantsOf(root)) {
+        if (!node.isTextNode()) {
+            continue;
+        }
+        length += toText(node).length();
+        if (length > kTextContentLengthSaturation) {
+            return kTextContentLengthSaturation;
+        }
+    }
+    return length;
+}
+
+bool isVisible(Element& element)
+{
+    const ComputedStyle* style = element.computedStyle();
+    if (!style)
+        return false;
+    ASSERT(style->display() != NONE);

[esprehn, 2015/11/03 07:45:10]

this assert is wrong, you can have a style and be display() == NONE, you want to
check it too.

[wychen, 2015/11/03 08:59:49]

Done.

+    return (
+        style->visibility() != HIDDEN
+        && style->opacity() != 0
+    );
+}
+
+bool matchAttributes(Element& element, const Vector<String>& words)
+{
+    const String& classes = element.getClassAttribute();
+    const String& id = element.getIdAttribute();
+    for (const String& word : words) {
+        if (classes.findIgnoringCase(word) != WTF::kNotFound
+            || id.findIgnoringCase(word) != WTF::kNotFound) {
+            return true;
+        }
+    }
+    return false;
+}
+
+// underListItem denotes that at least one of the ancesters is <li> element.
+void collectFeatures(Element& root, WebDistillabilityFeatures& features, bool underListItem = false)
+{
+    DEFINE_STATIC_LOCAL(Vector<String>, unlikelyCandidates, ());
+    if (unlikelyCandidates.isEmpty()) {
+        auto words = {
+            "banner",
+            "combx",
+            "comment",
+            "community",
+            "disqus",
+            "extra",
+            "foot",
+            "header",
+            "menu",
+            "related",
+            "remark",
+            "rss",
+            "share",
+            "shoutbox",
+            "sidebar",
+            "skyscraper",
+            "sponsor",
+            "ad-break",
+            "agegate",
+            "pagination",
+            "pager",
+            "popup"
+        };
+        for (auto word : words) {
+            unlikelyCandidates.append(word);
+        }
+    }
+    DEFINE_STATIC_LOCAL(Vector<String>, highlyLikelyCandidates, ());
+    if (highlyLikelyCandidates.isEmpty()) {
+        for (auto word : {"and", "article", "body", "column", "main", "shadow"}) {

[esprehn, 2015/11/03 07:45:10]

I'd wrap this one too.

[wychen, 2015/11/03 08:59:48]

Done.

+            highlyLikelyCandidates.append(word);
+        }
+    }
+    // Filter out short P elements. The threshold is set to around 2 English sentences.
+    const unsigned kParagraphLengthThreshold = 140;
+
+    // Saturate the scores to save time. The max is the score of 6 long paragraphs.
+    const double kMozScoreSaturation = 6 * sqrt(kTextContentLengthSaturation - kParagraphLengthThreshold);
+    const double kMozScoreAllSqrtSaturation = 6 * sqrt(kTextContentLengthSaturation);
+    const double kMozScoreAllLinearSaturation = 6 * kTextContentLengthSaturation;
+
+    for (Node& node : NodeTraversal::childrenOf(root)) {
+        if (node.isTextNode()) {
+            features.textContentLength += toText(node).length();

[esprehn, 2015/11/03 07:45:10]

this is going to add the length of every inline <script> or <style> too which
seems bad, I don't think you want to do that.

[wychen, 2015/11/03 08:59:48]

It is possible that innerTextLength/textContentLength ratio is useful because it
catches exactly this case, and can learn from this feature that doesn't make
visual differences.

Without innerTextLength, having textContentLength itself is not really useful,
so I've removed this as well.

+            continue;
+        }
+        if (!node.isElementNode()) {
+            continue;
+        }
+
+        features.elementCount++;
+        Element& element = toElement(node);
+        if (element.hasTagName(aTag)) {
+            features.anchorCount++;
+        } else if (element.hasTagName(formTag)) {
+            features.formCount++;
+        } else if (element.hasTagName(inputTag)) {
+            const HTMLInputElement& input = toHTMLInputElement(element);
+            if (equalIgnoringCase(input.type(), InputTypeNames::text)) {

[esprehn, 2015/11/03 07:45:10]

ditto == InputTypeNames::text

[wychen, 2015/11/03 08:59:48]

Good catch! I guess AtomicString == is faster.

+                features.textInputCount++;
+            } else if (equalIgnoringCase(input.type(), InputTypeNames::password)) {

[esprehn, 2015/11/03 07:45:10]

this is always lowercase, you can just do == ::password

[wychen, 2015/11/03 08:59:48]

Done.

+                features.passwordInputCount++;
+            }
+        } else if (element.hasTagName(pTag) || element.hasTagName(preTag)) {
+            if (element.hasTagName(pTag)) {
+                features.pCount++;
+            } else {
+                features.preCount++;
+            }
+            if (!underListItem
+                && (features.mozScore < kMozScoreSaturation
+                    || features.mozScoreAllSqrt < kMozScoreAllSqrtSaturation
+                    || features.mozScoreAllLinear < kMozScoreAllLinearSaturation)
+                && isVisible(element)

[esprehn, 2015/11/03 07:45:10]

this is a crazy set of conditions, in blink we try not to do this. Instead we
write a helper function with lots of early returns that ends in return true.

bool isFoo(a, b, c) {
  if (!underListItem)
    return false;
  ...
  return true;
}

that avoids this crazy nesting of && and ||.

[wychen, 2015/11/03 08:59:48]

Done.

+                && (!matchAttributes(element, unlikelyCandidates) || matchAttributes(element, highlyLikelyCandidates))
+                ) {
+                unsigned length = textContentLengthSaturated(element);
+                if (length >= kParagraphLengthThreshold) {
+                    features.mozScore += sqrt(length - kParagraphLengthThreshold);
+                    features.mozScore = std::min(features.mozScore, kMozScoreSaturation);
+                }
+                features.mozScoreAllSqrt += sqrt(length);
+                features.mozScoreAllSqrt = std::min(features.mozScoreAllSqrt, kMozScoreAllSqrtSaturation);
+
+                features.mozScoreAllLinear += length;
+                features.mozScoreAllLinear = std::min(features.mozScoreAllLinear, kMozScoreAllLinearSaturation);
+            }
+        } else if (element.hasTagName(liTag)) {
+            underListItem = true;
+        }
+        collectFeatures(element, features, underListItem);
+    }
+}
+
+bool hasOpenGraphArticle(const Element& head)
+{
+    DEFINE_STATIC_LOCAL(AtomicString, ogType, ("og:type"));
+    DEFINE_STATIC_LOCAL(AtomicString, propertyAttr, ("property"));
+    for (const Element* child = ElementTraversal::firstChild(head); child; child = ElementTraversal::nextSibling(*child)) {
+        if (!isHTMLMetaElement(*child))
+            continue;
+        const HTMLMetaElement& meta = toHTMLMetaElement(*child);
+
+        if (meta.name() == ogType || meta.getAttribute(propertyAttr) == ogType) {
+            if (equalIgnoringCase(meta.content(), "article")) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+bool isMobileFriendly(Document& document)
+{
+    FrameHost* frameHost = document.frameHost();
+    if (!frameHost)
+        return false;
+    return frameHost->visualViewport().shouldDisableDesktopWorkarounds();
+}
+
+} // namespace
+
+WebDistillabilityFeatures DocumentStatisticsCollector::collectStatistics(Document& document)
+{
+    WebDistillabilityFeatures features = WebDistillabilityFeatures();
+
+    if (!document.frame() || !document.frame()->isMainFrame())
+        return features;
+
+    ASSERT(document.hasFinishedParsing());
+

[esprehn, 2015/11/03 07:45:10]

TRACE_EVENT0("DocumentStatisticsCollector::collectStatistics")

[wychen, 2015/11/03 08:59:49]

Done.

+    HTMLElement* body = document.body();

[esprehn, 2015/11/03 07:45:10]

needs a trace macro

[wychen, 2015/11/03 08:59:48]

I don't understand this comment. Did you mean DEFINE_TRACE?

+    HTMLElement* head = document.head();
+
+    if (!body || !head)
+        return features;
+
+    if (isMobileFriendly(document)) {
+        features.isMobileFriendly = true;
+        return features;
+    }
+
+    double startTime = monotonicallyIncreasingTime();
+
+    // Traverse the DOM tree and collect statistics.
+    collectFeatures(*body, features);
+    features.openGraph = hasOpenGraphArticle(*head);
+
+    double elapsedTime = monotonicallyIncreasingTime() - startTime;
+    Platform::current()->histogramCustomCounts("WebCore.DistillabilityUs", static_cast<int>(1e6 * elapsedTime), 1, 1000000, 50);
+
+    return features;
+}
+
+}