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// Copyright 2020 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.
#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_FRAME_OVERLAY_INTERSTITIAL_AD_DETECTOR_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_FRAME_OVERLAY_INTERSTITIAL_AD_DETECTOR_H_
#include "base/macros.h"
#include "base/time/time.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/platform/geometry/int_size.h"
#include "third_party/blink/renderer/platform/graphics/dom_node_id.h"
namespace blink {
class LocalFrame;
// Detects overlay interstitials and record a use counter when an instance is
// found. The current scope is to consider only pop-ups, which appear after
// content on the page begins to load.
//
// Better Ads Standards definition:
// https://www.betterads.org/desktop-pop-up-ad/
// https://www.betterads.org/mobile-pop-up-ad/
//
// Heuristic:
// We do hit testing at the center of the browser viewport at regular intervals.
// The top element is an interstitial pop-up candidate if the following
// conditions are met:
// 1) It's immobile to scrolling (e.g. position:fixed).
// 2) The size is large.
// 3) It's created without user gesture.
// 4) It's created after the main content has loaded.
//
// The candidate will be actually counted as an overlay pop-up instance after we
// have checked some status at its dismissal time. On dismissal, if the main
// frame scrolling offset hasn't changed since the candidate's appearance, we
// count it as an overlay pop-up; otherwise, we skip that candidate because it
// could be a parallax/scroller ad.
//
// We could potentially miss some true positive cases: the user could click at
// an empty space which activates the user gesture, and coincidentally the
// pop-up automatically shows up; the user could make some scrolling
// before closing the pop-up; etc. However, we accept the trade-off exchanging a
// lower rate of false positive for an increase in the rate of false negatives.
class CORE_EXPORT OverlayInterstitialAdDetector {
public:
OverlayInterstitialAdDetector() = default;
~OverlayInterstitialAdDetector() = default;
void MaybeFireDetection(LocalFrame* main_frame);
void OnPopupAdDetected(LocalFrame* main_frame);
private:
bool started_detection_ = false;
bool main_content_has_loaded_ = false;
// The following members are valid only when |started_detection_| is true.
base::Time last_detection_time_;
IntSize last_detection_main_frame_size_;
DOMNodeId candidate_id_;
// The following members are valid only when |candidate_| is not nullptr.
int candidate_start_main_frame_scroll_offset_ = 0;
// The node id of the last element that was detected as unqualified to be an
// overlay pop-up. We compare any potential candidate with the last
// unqualified element and skip it if they are equal.
//
// It allows us to exclude some false positive cases. e.g. an
// overlay was excluded from the initial consideration because it was created
// with a gesture. After 5 seconds the gesture would be gone, but we still
// want to exclude it as it was originally created with a gesture.
//
// Another advantage is this saves some computation cost. e.g. if an ad was
// unqualified because it didn't have a viewport constraint position, then we
// can skip it on its next occurrence without computing the style again.
DOMNodeId last_unqualified_element_id_;
bool done_detection_ = false;
DISALLOW_COPY_AND_ASSIGN(OverlayInterstitialAdDetector);
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_FRAME_OVERLAY_INTERSTITIAL_AD_DETECTOR_H_
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