chromium/src/third_party/blink/renderer/core/html/anchor_element_metrics.h

// Copyright 2018 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_HTML_ANCHOR_ELEMENT_METRICS_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_HTML_ANCHOR_ELEMENT_METRICS_H_

#include "base/optional.h"
#include "third_party/blink/public/mojom/loader/navigation_predictor.mojom-blink-forward.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/platform/heap/handle.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"

namespace blink {

class Document;
class HTMLAnchorElement;

// This class is used to hold metrics of an html anchor element. Metrics are
// extracted via static methods. Metrics can be recorded and converted to mojom
// message used to send to the browser process.
class CORE_EXPORT AnchorElementMetrics {
  STACK_ALLOCATED();

 public:
  // Creates AnchorElementMetrics from anchor element if possible. Then records
  // the metrics, and sends them to the browser process.
  static base::Optional<AnchorElementMetrics> MaybeReportClickedMetricsOnClick(
      const HTMLAnchorElement*);

  // Gets anchor elements from |document|, extracts features of valid anchor
  // elements and sends to the browser process.
  static void MaybeReportViewportMetricsOnLoad(Document& document);

  // Called when OnLoad occurs. Subscribes |document|'s
  // AnchorElementMetricsSender to document lifecycle events until the layout is
  // clean. The sender is expected to call |MaybeReportViewportMetricsOnLoad()|
  // one time.
  static void NotifyOnLoad(Document& document);

  // Getters of anchor element features.
  float GetRatioArea() const { return ratio_area_; }
  float GetRatioVisibleArea() const { return ratio_visible_area_; }
  float GetRatioDistanceTopToVisibleTop() const {
    return ratio_distance_top_to_visible_top_;
  }
  float GetRatioDistanceCenterToVisibleTop() const {
    return ratio_distance_center_to_visible_top_;
  }
  float GetRatioDistanceRootTop() const { return ratio_distance_root_top_; }
  float GetRatioDistanceRootBottom() const {
    return ratio_distance_root_bottom_;
  }
  bool GetIsInIframe() const { return is_in_iframe_; }
  bool GetContainsImage() const { return contains_image_; }
  bool GetIsSameHost() const { return is_same_host_; }
  bool GetIsUrlIncrementedByOne() const { return is_url_incremented_by_one_; }

 private:
  // The maximum number of anchor element metrics allowed to report to the
  // browser on page load.
  static const int kMaxAnchorElementMetricsSize;

  // Extract features of the anchor element.
  static base::Optional<AnchorElementMetrics> Create(const HTMLAnchorElement*);

  // Returns the mojom struct used to send metrics to the browser process.
  mojom::blink::AnchorElementMetricsPtr CreateMetricsPtr() const;

  // Record metrics of |anchor_element_|. Function is called when the anchor
  // element is clicked by the user.
  void RecordMetricsOnClick() const;

  // The anchor element that this class is associated with.
  const HTMLAnchorElement* anchor_element_;

  // The ratio of the absolute/visible clickable region area of an anchor
  // element, and the viewport area.
  const float ratio_area_;
  const float ratio_visible_area_;

  // The distance between the top/center of the clickable region of an anchor
  // element and the top edge of the visible region, divided by the viewport
  // height.
  const float ratio_distance_top_to_visible_top_;
  const float ratio_distance_center_to_visible_top_;

  // The distance between the top of the clickable region of an anchor element
  // and the top edge of the root frame, divided by the viewport height.
  const float ratio_distance_root_top_;

  // The distance between the bottom of the clickable region of an anchor
  // element and the bottom edge of the root frame, divided by the viewport
  // height.
  const float ratio_distance_root_bottom_;

  // Whether the anchor element is within an iframe.
  const bool is_in_iframe_;

  // Whether the anchor element contains an image element.
  const bool contains_image_;

  // Whether the link target has the same host as the root document.
  const bool is_same_host_;

  // Whether the target url and the host url only differ by one number,
  // and the number in target url equals the one in host url plus one.
  const bool is_url_incremented_by_one_;

  inline AnchorElementMetrics(const HTMLAnchorElement* anchor_element,
                              float ratio_area,
                              float ratio_visible_area,
                              float ratio_distance_top_to_visible_top,
                              float ratio_distance_center_to_visible_top,
                              float ratio_distance_root_top,
                              float ratio_distance_root_bottom,
                              bool is_in_iframe,
                              bool contains_image,
                              bool is_same_host,
                              bool is_url_incremented_by_one)
      : anchor_element_(anchor_element),
        ratio_area_(ratio_area),
        ratio_visible_area_(ratio_visible_area),
        ratio_distance_top_to_visible_top_(ratio_distance_top_to_visible_top),
        ratio_distance_center_to_visible_top_(
            ratio_distance_center_to_visible_top),
        ratio_distance_root_top_(ratio_distance_root_top),
        ratio_distance_root_bottom_(ratio_distance_root_bottom),
        is_in_iframe_(is_in_iframe),
        contains_image_(contains_image),
        is_same_host_(is_same_host),
        is_url_incremented_by_one_(is_url_incremented_by_one) {
    DCHECK_LE(0, ratio_area_);
    DCHECK_GE(1, ratio_area_);
    DCHECK_LE(0, ratio_visible_area_);
    DCHECK_GE(1, ratio_visible_area_);
  }
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_HTML_ANCHOR_ELEMENT_METRICS_H_