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// Copyright 2020 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_PAGE_LOAD_METRICS_BROWSER_LAYOUT_SHIFT_NORMALIZATION_H_
#define COMPONENTS_PAGE_LOAD_METRICS_BROWSER_LAYOUT_SHIFT_NORMALIZATION_H_
#include <vector>
#include "base/time/time.h"
#include "components/page_load_metrics/browser/page_load_metrics_observer.h"
namespace page_load_metrics {
// LayoutShiftNormalization implements some experimental strategies for
// normalizing layout shift. Instead of adding all layout shift scores together
// like what we do in Cumulative Layout Shift(CLS), we aggregate layout shifts
// window by window. For more information, see go/layoutshiftnorm.
class LayoutShiftNormalization {
public:
LayoutShiftNormalization();
LayoutShiftNormalization(const LayoutShiftNormalization&) = delete;
LayoutShiftNormalization& operator=(const LayoutShiftNormalization&) = delete;
~LayoutShiftNormalization();
const NormalizedCLSData& normalized_cls_data() const {
return normalized_cls_data_;
}
void AddNewLayoutShifts(
const std::vector<page_load_metrics::mojom::LayoutShiftPtr>& new_shifts,
base::TimeTicks current_time,
/*Whole page CLS*/ float cumulative_layout_shift_score);
void ClearAllLayoutShifts();
private:
struct SessionWindow {
base::TimeTicks start_time;
base::TimeTicks last_time;
float layout_shift_score = 0.0;
};
void UpdateWindowCLS(
std::vector<std::pair<base::TimeTicks, double>>::const_iterator first,
std::vector<std::pair<base::TimeTicks, double>>::const_iterator
first_non_stale,
std::vector<std::pair<base::TimeTicks, double>>::const_iterator last,
float cumulative_layout_shift_score);
void UpdateSessionWindow(
SessionWindow* session_window,
base::TimeDelta gap,
base::TimeDelta max_duration,
std::vector<std::pair<base::TimeTicks, double>>::const_iterator begin,
std::vector<std::pair<base::TimeTicks, double>>::const_iterator end,
float& max_score);
// CLS normalization
NormalizedCLSData normalized_cls_data_;
// This vector is maintained in sorted order.
std::vector<std::pair<base::TimeTicks, double>> recent_layout_shifts_;
SessionWindow session_gap1000ms_max5000ms_;
};
} // namespace page_load_metrics
#endif // COMPONENTS_PAGE_LOAD_METRICS_BROWSER_LAYOUT_SHIFT_NORMALIZATION_H_
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