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// 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 "third_party/blink/renderer/core/dom/document_statistics_collector.h"
#include "third_party/blink/public/platform/platform.h"
#include "third_party/blink/public/platform/web_distillability.h"
#include "third_party/blink/renderer/core/dom/element_traversal.h"
#include "third_party/blink/renderer/core/dom/node_computed_style.h"
#include "third_party/blink/renderer/core/dom/text.h"
#include "third_party/blink/renderer/core/frame/local_frame.h"
#include "third_party/blink/renderer/core/frame/visual_viewport.h"
#include "third_party/blink/renderer/core/html/forms/html_input_element.h"
#include "third_party/blink/renderer/core/html/html_head_element.h"
#include "third_party/blink/renderer/core/html/html_meta_element.h"
#include "third_party/blink/renderer/core/html_names.h"
#include "third_party/blink/renderer/core/input_type_names.h"
#include "third_party/blink/renderer/core/page/page.h"
#include "third_party/blink/renderer/platform/instrumentation/histogram.h"
namespace blink {
namespace {
// Saturate the length of a paragraph to save time.
const int kTextContentLengthSaturation = 1000;
// 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.
// 6 * sqrt(kTextContentLengthSaturation - kParagraphLengthThreshold)
const double kMozScoreSaturation = 175.954539583;
// 6 * sqrt(kTextContentLengthSaturation);
const double kMozScoreAllSqrtSaturation = 189.73665961;
const double kMozScoreAllLinearSaturation = 6 * kTextContentLengthSaturation;
unsigned TextContentLengthSaturated(const Element& root) {
unsigned length = 0;
// This skips shadow DOM intentionally, to match the JavaScript
// implementation. We would like to use the same statistics extracted by the
// JavaScript implementation on iOS, and JavaScript cannot peek deeply into
// shadow DOM except on modern Chrome versions.
// Given shadow DOM rarely appears in <P> elements in long-form articles, the
// overall accuracy should not be largely affected.
for (Node& node : NodeTraversal::InclusiveDescendantsOf(root)) {
auto* text_node = DynamicTo<Text>(node);
if (!text_node) {
continue;
}
length += text_node->length();
if (length > kTextContentLengthSaturation) {
return kTextContentLengthSaturation;
}
}
return length;
}
bool IsVisible(const Element& element) {
const ComputedStyle* style = element.GetComputedStyle();
if (!style)
return false;
return (style->Display() != EDisplay::kNone &&
style->Visibility() != EVisibility::kHidden && style->Opacity() != 0);
}
bool MatchAttributes(const 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;
}
bool IsGoodForScoring(const WebDistillabilityFeatures& features,
const Element& element) {
DEFINE_STATIC_LOCAL(Vector<String>, unlikely_candidates, ());
if (unlikely_candidates.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) {
unlikely_candidates.push_back(word);
}
}
DEFINE_STATIC_LOCAL(Vector<String>, highly_likely_candidates, ());
if (highly_likely_candidates.IsEmpty()) {
auto words = {"and", "article", "body", "column", "main", "shadow"};
for (auto* word : words) {
highly_likely_candidates.push_back(word);
}
}
if (!IsVisible(element))
return false;
if (features.moz_score >= kMozScoreSaturation &&
features.moz_score_all_sqrt >= kMozScoreAllSqrtSaturation &&
features.moz_score_all_linear >= kMozScoreAllLinearSaturation)
return false;
if (MatchAttributes(element, unlikely_candidates) &&
!MatchAttributes(element, highly_likely_candidates))
return false;
return true;
}
// underListItem denotes that at least one of the ancesters is <li> element.
void CollectFeatures(Element& root,
WebDistillabilityFeatures& features,
bool under_list_item = false) {
for (Element& element : ElementTraversal::ChildrenOf(root)) {
bool is_list_item = false;
features.element_count++;
if (element.HasTagName(html_names::kATag)) {
features.anchor_count++;
} else if (element.HasTagName(html_names::kFormTag)) {
features.form_count++;
} else if (element.HasTagName(html_names::kInputTag)) {
const auto& input = To<HTMLInputElement>(element);
if (input.type() == input_type_names::kText) {
features.text_input_count++;
} else if (input.type() == input_type_names::kPassword) {
features.password_input_count++;
}
} else if (element.HasTagName(html_names::kPTag) ||
element.HasTagName(html_names::kPreTag)) {
if (element.HasTagName(html_names::kPTag)) {
features.p_count++;
} else {
features.pre_count++;
}
if (!under_list_item && IsGoodForScoring(features, element)) {
unsigned length = TextContentLengthSaturated(element);
if (length >= kParagraphLengthThreshold) {
features.moz_score += sqrt(length - kParagraphLengthThreshold);
features.moz_score =
std::min(features.moz_score, kMozScoreSaturation);
}
features.moz_score_all_sqrt += sqrt(length);
features.moz_score_all_sqrt =
std::min(features.moz_score_all_sqrt, kMozScoreAllSqrtSaturation);
features.moz_score_all_linear += length;
features.moz_score_all_linear = std::min(features.moz_score_all_linear,
kMozScoreAllLinearSaturation);
}
} else if (element.HasTagName(html_names::kLiTag)) {
is_list_item = true;
}
CollectFeatures(element, features, under_list_item || is_list_item);
}
}
bool HasOpenGraphArticle(const Element& head) {
DEFINE_STATIC_LOCAL(AtomicString, og_type, ("og:type"));
DEFINE_STATIC_LOCAL(AtomicString, property_attr, ("property"));
for (const Element* child = ElementTraversal::FirstChild(head); child;
child = ElementTraversal::NextSibling(*child)) {
auto* meta = DynamicTo<HTMLMetaElement>(child);
if (!meta)
continue;
if (meta->GetName() == og_type ||
meta->getAttribute(property_attr) == og_type) {
if (EqualIgnoringASCIICase(meta->Content(), "article")) {
return true;
}
}
}
return false;
}
bool IsMobileFriendly(Document& document) {
if (Page* page = document.GetPage())
return page->GetVisualViewport().ShouldDisableDesktopWorkarounds();
return false;
}
} // namespace
WebDistillabilityFeatures DocumentStatisticsCollector::CollectStatistics(
Document& document) {
TRACE_EVENT0("blink", "DocumentStatisticsCollector::collectStatistics");
WebDistillabilityFeatures features = WebDistillabilityFeatures();
if (!document.GetFrame() || !document.GetFrame()->IsMainFrame())
return features;
DCHECK(document.HasFinishedParsing());
HTMLElement* body = document.body();
HTMLElement* head = document.head();
if (!body || !head)
return features;
features.is_mobile_friendly = IsMobileFriendly(document);
base::TimeTicks start_time = base::TimeTicks::Now();
// This should be cheap since collectStatistics is only called right after
// layout.
document.UpdateStyleAndLayoutTree();
// Traverse the DOM tree and collect statistics.
CollectFeatures(*body, features);
features.open_graph = HasOpenGraphArticle(*head);
base::TimeDelta elapsed_time = base::TimeTicks::Now() - start_time;
DEFINE_STATIC_LOCAL(CustomCountHistogram, distillability_histogram,
("WebCore.DistillabilityUs", 1, 1000000, 50));
distillability_histogram.CountMicroseconds(elapsed_time);
return features;
}
} // namespace blink
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