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"
+#include "core/dom/ElementTraversal.h"
+#include "core/editing/iterators/TextIterator.h"
+#include "core/html/HTMLHeadElement.h"
+#include "core/html/HTMLInputElement.h"
+#include "core/html/HTMLMetaElement.h"
+
+// TODO(wychen): The following lines will be gone before landing.
+#include "core/inspector/ConsoleMessage.h"
+
+#include "public/platform/WebDistillability.h"
+#include "wtf/text/StringBuilder.h"
+#include "wtf/text/StringImpl.h"
+
+namespace blink {
+
+using namespace HTMLNames;
+
+namespace {
+
+// Saturate the length of a paragraph to save time.
+const int kTextContentLengthSaturation = 1000;
+
+unsigned trimmedTextContentLength(Element& root)
+{
+    int firstNonWhite = -1, lastNonWhite = -1;
+    unsigned position = 0;
+    unsigned length = 0;
+    // TODO(wychen): scan backwards for lastNonWhite should be much faster in practice.
+    // This skips shadow dom intentionally.
+    for (Node& node : NodeTraversal::inclusiveDescendantsOf(root)) {
+        if (!node.isTextNode()) {
+            continue;
+        }
+        const String& text = toText(node).data();
+        for (unsigned i = 0; i < text.length(); i++) {
+            if (!isSpaceOrNewline(text[i])) {
+                if (firstNonWhite < 0) {
+                    firstNonWhite = lastNonWhite = i + position;
+                } else {
+                    lastNonWhite = i + position;
+                }
+            }
+        }
+        if (firstNonWhite >= 0) {
+            length = lastNonWhite - firstNonWhite + 1;
+            if (length > kTextContentLengthSaturation) {
+                return kTextContentLengthSaturation;
+            }
+        }
+        position += text.length();
+    }
+    return length;
+}
+
+unsigned innerTextLength(Element& root)

[wychen, 2015/10/28 22:00:51]

I'll remove innerTextLength() for this version.

+{
+    unsigned length = 0;
+    EphemeralRange range = EphemeralRange::rangeOfContents(root);
+    TextIterator it(range.startPosition(), range.endPosition(), TextIteratorForInnerText);
+    for (; !it.atEnd(); it.advance()) {
+        length += it.length();
+    }
+    return length;
+}
+
+bool isVisible(Element& element)
+{
+    const blink::ComputedStyle* style = element.ensureComputedStyle();

[esprehn, 2015/10/28 00:07:28]

don't use ensureComputedStyle(), it forces us to compute the style for display:
none nodes and allocate rare data. You just want to use computedStyle() and null
check it, that won't force any new style computations.

[wychen, 2015/10/28 00:25:45]

Quick question. I want to use getBoundingClientRect().{height, width}==0 to
replace display==none checking. Is this cheap enough to be used here?

[esprehn, 2015/10/28 00:37:17]

That'll be more expensive than just checking the display, it requires allocating
a ClientRect object, why do you want to do that instead of just checking
display?

[wychen, 2015/10/28 00:49:46]

Since display is not inherited, the current checking is not very accurate.
getBoundingClientRect() is available in JS, and works for the child elements of
a display=='none' element. I'm trying to find a way that is both more accurate,
and available in JS. Are there better alternatives?

[esprehn, 2015/10/28 00:57:19]

var computedStyle = getComputedStyle(element);
!computedStyle.width && !computedStyle.height

I'm not sure if that's faster than getBoundingClientRect() though.

For now I'd suggest just null checking the return value of computedStyle() until
we figure out the right web exposed API here.

[wychen, 2015/10/28 22:00:51]

I just tried that. If the parent is display==none, width and height become
"auto". I guess getBoundingClientRect() is still necessary to catch this case.
Done.

+    return (
+        style->display() != NONE
+        && 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()) {
+        for (auto word : {"banner", "combx", "comment", "community", "disqus", "extra", "foot", "header", "menu", "related", "remark", "rss", "share", "shoutbox", "sidebar", "skyscraper", "sponsor", "ad-break", "agegate", "pagination", "pager", "popup"}) {
+            unlikelyCandidates.append(word);
+        }
+    }
+    DEFINE_STATIC_LOCAL(Vector<String>, highlyLikelyCandidates, ());
+    if (highlyLikelyCandidates.isEmpty()) {
+        for (auto word : {"and", "article", "body", "column", "main", "shadow"}) {
+            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();
+            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)) {
+                features.textInputCount++;
+            } else if (equalIgnoringCase(input.type(), InputTypeNames::password)) {
+                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)
+                && (!matchAttributes(element, unlikelyCandidates) || matchAttributes(element, highlyLikelyCandidates))
+                ) {
+                unsigned length = trimmedTextContentLength(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)
+{
+    for (const Element* child = ElementTraversal::firstChild(head); child; child = ElementTraversal::nextSibling(*child)) {
+        if (!isHTMLMetaElement(*child))
+            continue;
+        const HTMLMetaElement& meta = toHTMLMetaElement(*child);
+        DEFINE_STATIC_LOCAL(AtomicString, ogType, ("og:type"));
+        DEFINE_STATIC_LOCAL(AtomicString, propertyAttr, ("property"));

[esprehn, 2015/10/28 00:07:28]

move these to the top of the function, not inside the loop.

[wychen, 2015/10/28 22:00:51]

Done.

+
+        if (meta.name() == ogType || meta.getAttribute(propertyAttr) == ogType) {
+            if (equalIgnoringCase(meta.content(), "article")) {
+                return true;
+            }
+        }
+    }
+    return false;
+}
+
+} // namespace
+
+WebDistillabilityFeatures DocumentStatisticsCollector::collectStatistics(Document& document)
+{
+    WebDistillabilityFeatures features = WebDistillabilityFeatures();
+
+    if (!document.frame() || !document.frame()->isMainFrame())
+        return features;
+
+    ASSERT(document.hasFinishedParsing());
+
+    if (!document.body() || !document.head())
+        return features;
+
+    // The following DISTILLER_NDEBUG sections would be gone when landing.
+#ifndef DISTILLER_NDEBUG
+    double startTime = WTF::currentTime();

[esprehn, 2015/10/28 00:07:28]

add tracing macros, remove your time based stuff. :)

[wychen, 2015/10/28 22:00:51]

Thanks for the tip. I gave it a try, but it involved with more GUI than I'd
like.

+#endif
+
+    // First, traverse the DOM tree and collect statistics.
+    collectFeatures(*document.body(), features);
+
+#ifndef DISTILLER_NDEBUG
+    double elapsedTime = WTF::currentTime() - startTime;
+    startTime = WTF::currentTime();
+#endif
+
+    features.openGraph = hasOpenGraphArticle(*document.head());
+
+#ifndef DISTILLER_NDEBUG
+    double ogElapsedTime = WTF::currentTime() - startTime;
+    startTime = WTF::currentTime();
+#endif
+
+    // Next, traverse the Layout tree and collect statistics on innerText length.
+    document.updateLayout();

[dglazkov, 2015/10/27 23:59:19]

Instead of updateLayout, just ASSERT to ensure the function is never called when
layout is dirty -- since you'll be calling this only out of didMeaningfulLayout
hook. This may seen counter to Elliott's earlier advice, but it's really the
same thing :)

[wychen, 2015/10/28 22:00:51]

Done.

+    features.innerTextLength = innerTextLength(*document.body());
+
+#ifndef DISTILLER_NDEBUG
+    double innerTextElapsedTime = WTF::currentTime() - startTime;
+#endif
+
+#ifndef DISTILLER_NDEBUG
+    StringBuilder message;
+    message.append("openGraph: ");
+    message.appendNumber(features.openGraph);
+    message.append(", elementCount: ");
+    message.appendNumber(features.elementCount);
+    message.append(", anchorCount: ");
+    message.appendNumber(features.anchorCount);
+    message.append(", formCount: ");
+    message.appendNumber(features.formCount);
+    message.append(", textInputCount: ");
+    message.appendNumber(features.textInputCount);
+    message.append(", passwordInputCount: ");
+    message.appendNumber(features.passwordInputCount);
+    message.append(", pCount: ");
+    message.appendNumber(features.pCount);
+    message.append(", preCount: ");
+    message.appendNumber(features.preCount);
+    message.append(", innerTextLength: ");
+    message.appendNumber(features.innerTextLength);
+    message.append(", textContentLength: ");
+    message.appendNumber(features.textContentLength);
+    message.append(", mozScore: ");
+    message.appendNumber(features.mozScore);
+    message.append(", mozScoreAllSqrt: ");
+    message.appendNumber(features.mozScoreAllSqrt);
+    message.append(", mozScoreAllLinear: ");
+    message.appendNumber(features.mozScoreAllLinear);
+    message.append("\nElapsed time (ms): ");
+    message.appendNumber(elapsedTime * 1000);
+    message.append(", openGraph time (ms): ");
+    message.appendNumber(ogElapsedTime * 1000);
+    message.append(", innerText time (ms): ");
+    message.appendNumber(innerTextElapsedTime * 1000);
+
+    RefPtrWillBeRawPtr<ConsoleMessage> consoleMessage = ConsoleMessage::create(ConsoleAPIMessageSource, DebugMessageLevel, message.toString());
+    document.addConsoleMessage(consoleMessage);
+#endif
+
+    return features;
+}
+
+}