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// Copyright 2018 The Chromium Authors
// 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_PLATFORM_WIDGET_INPUT_SCROLL_PREDICTOR_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_WIDGET_INPUT_SCROLL_PREDICTOR_H_
#include <vector>
#include "third_party/blink/public/mojom/input/gesture_event.mojom-blink.h"
#include "third_party/blink/renderer/platform/widget/input/event_with_callback.h"
#include "third_party/blink/renderer/platform/widget/input/prediction/filter_factory.h"
#include "ui/base/prediction/input_predictor.h"
#include "ui/base/prediction/prediction_metrics_handler.h"
namespace blink {
namespace test {
class ScrollPredictorTest;
}
// This class handles resampling GestureScrollUpdate events on InputHandlerProxy
// at |BeginFrame| signal, before events been dispatched. The predictor use
// original events to update the prediction and align the aggregated event
// timestamp and delta_x/y to the VSync time.
class PLATFORM_EXPORT ScrollPredictor {
public:
// Select the predictor type from field trial params and initialize the
// predictor.
explicit ScrollPredictor();
ScrollPredictor(const ScrollPredictor&) = delete;
ScrollPredictor& operator=(const ScrollPredictor&) = delete;
~ScrollPredictor();
// Reset the predictors on each GSB.
void ResetOnGestureScrollBegin(const WebGestureEvent& event);
// Resampling GestureScrollUpdate events. Updates the prediction with events
// in original events list, and apply the prediction to the aggregated GSU
// event if enable_resampling is true.
std::unique_ptr<EventWithCallback> ResampleScrollEvents(
std::unique_ptr<EventWithCallback> event_with_callback,
base::TimeTicks frame_time,
base::TimeDelta frame_interval);
// Resamples the current GestureScrollUpdate events at the given `frame_time`.
std::unique_ptr<EventWithCallback> GenerateSyntheticScrollUpdate(
base::TimeTicks frame_time,
base::TimeDelta frame_interval,
mojom::blink::GestureDevice gesture_device,
int modifiers);
bool HasPrediction() const;
private:
friend class test::InputHandlerProxyEventQueueTest;
friend class test::ScrollPredictorTest;
// Reset predictor and clear accumulated delta. This should be called on
// GestureScrollBegin.
void Reset();
// Update the prediction with GestureScrollUpdate deltaX and deltaY
void UpdatePrediction(const WebInputEvent& event, base::TimeTicks frame_time);
// Apply resampled deltaX/deltaY to gesture events.
void ResampleEvent(base::TimeTicks frame_time,
base::TimeDelta frame_interval,
WebInputEvent* event);
// Reports metrics scores UMA histogram based on the metrics defined
// in |PredictionMetricsHandler|
void EvaluatePrediction();
std::unique_ptr<ui::InputPredictor> predictor_;
std::unique_ptr<ui::InputFilter> filter_;
std::unique_ptr<FilterFactory> filter_factory_;
// Whether predicted scroll events should be filtered or not
bool filtering_enabled_ = false;
// Total scroll delta from original scroll update events, used for calculating
// predictions. Reset on GestureScrollBegin.
gfx::PointF current_event_accumulated_delta_;
// Predicted accumulated delta from last vsync, use for calculating delta_x
// and delta_y for the resampled/predicted event.
gfx::PointF last_predicted_accumulated_delta_;
// Whether current scroll event should be resampled.
bool should_resample_scroll_events_ = false;
// Handler used for evaluating the prediction
ui::PredictionMetricsHandler metrics_handler_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_WIDGET_INPUT_SCROLL_PREDICTOR_H_
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