text: // 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_STICKY_AD_DETECTOR_H_
  #define THIRD_PARTY_BLINK_RENDERER_CORE_FRAME_STICKY_AD_DETECTOR_H_
  
  #include "base/optional.h"
  #include "base/time/time.h"
  #include "third_party/blink/renderer/core/core_export.h"
  #include "third_party/blink/renderer/platform/graphics/dom_node_id.h"
  
  namespace blink {
  
  class LocalFrame;
  
  // Detects large sticky ad at the bottom of the viewport, and record a use
  // counter when an instance is found.
  //
  // Better Ads Standards definition:
  // https://www.betterads.org/desktop-large-sticky-ad/
  // https://www.betterads.org/mobile-large-sticky-ad/
  //
  // Heuristic:
  // We do hit testing at the bottom center of the browser viewport at regular
  // intervals. The top element is a sticky ad candidate if the following
  // conditions are met:
  // 1) It has a non-default position w.r.t. the viewport.
  // 2) It's large in size (> 30% viewport size).
  // 3) The main page is not scrollable.
  //
  // The candidate will be actually counted as a sticky ad instance at a later
  // point, when we detect that the main frame scrolling position has changed by a
  // distance greater than the height of the candidate, and the candidate is still
  // at the bottom center. This allows us to exclude false positives like
  // parallax/scroller ads.
  class CORE_EXPORT StickyAdDetector {
   public:
    StickyAdDetector() = default;
    ~StickyAdDetector() = default;
  
    void MaybeFireDetection(LocalFrame* main_frame);
  
   private:
    void OnLargeStickyAdDetected(LocalFrame* main_frame);
  
    base::Optional<base::Time> last_detection_time_;
  
    DOMNodeId candidate_id_;
    int candidate_height_;
    int candidate_start_main_frame_scroll_offset_;
  
    bool done_detection_ = false;
  
    DISALLOW_COPY_AND_ASSIGN(StickyAdDetector);
  };
  
  }  // namespace blink
  
  #endif  // THIRD_PARTY_BLINK_RENDERER_CORE_FRAME_STICKY_AD_DETECTOR_H_
  