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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.
#include "third_party/blink/renderer/platform/widget/input/input_event_prediction.h"
#include "base/feature_list.h"
#include "base/metrics/field_trial_params.h"
#include "base/metrics/histogram_functions.h"
#include "third_party/blink/public/common/features.h"
namespace blink {
namespace {
const WebPointerProperties* ToWebPointerProperties(const WebInputEvent* event) {
if (WebInputEvent::IsMouseEventType(event->GetType()))
return static_cast<const WebMouseEvent*>(event);
if (WebInputEvent::IsPointerEventType(event->GetType()))
return static_cast<const WebPointerEvent*>(event);
return nullptr;
}
WebPointerProperties* ToWebPointerProperties(WebInputEvent* event) {
if (WebInputEvent::IsMouseEventType(event->GetType()))
return static_cast<WebMouseEvent*>(event);
if (WebInputEvent::IsPointerEventType(event->GetType()))
return static_cast<WebPointerEvent*>(event);
return nullptr;
}
} // namespace
InputEventPrediction::InputEventPrediction(bool enable_resampling)
: enable_resampling_(enable_resampling) {
// When resampling is enabled, set predictor type by resampling flag params;
// otherwise, get predictor type parameters from kInputPredictorTypeChoice
// flag.
std::string predictor_name =
enable_resampling_
? GetFieldTrialParamValueByFeature(
blink::features::kResamplingInputEvents, "predictor")
: GetFieldTrialParamValueByFeature(
blink::features::kInputPredictorTypeChoice, "predictor");
if (predictor_name.empty()) {
selected_predictor_type_ =
input_prediction::PredictorType::kScrollPredictorTypeKalman;
} else {
selected_predictor_type_ =
PredictorFactory::GetPredictorTypeFromName(predictor_name);
}
mouse_predictor_ = CreatePredictor();
}
InputEventPrediction::~InputEventPrediction() {}
void InputEventPrediction::HandleEvents(
blink::WebCoalescedInputEvent& coalesced_event,
base::TimeTicks frame_time) {
switch (coalesced_event.Event().GetType()) {
case WebInputEvent::Type::kMouseMove:
case WebInputEvent::Type::kTouchMove:
case WebInputEvent::Type::kPointerMove: {
size_t coalesced_size = coalesced_event.CoalescedEventSize();
for (size_t i = 0; i < coalesced_size; i++)
UpdatePrediction(coalesced_event.CoalescedEvent(i));
if (enable_resampling_)
ApplyResampling(frame_time, coalesced_event.EventPointer());
AddPredictedEvents(coalesced_event);
break;
}
case WebInputEvent::Type::kTouchScrollStarted:
case WebInputEvent::Type::kPointerCausedUaAction:
pointer_id_predictor_map_.clear();
break;
default:
ResetPredictor(coalesced_event.Event());
}
}
std::unique_ptr<ui::InputPredictor> InputEventPrediction::CreatePredictor()
const {
return PredictorFactory::GetPredictor(selected_predictor_type_);
}
void InputEventPrediction::UpdatePrediction(const WebInputEvent& event) {
if (WebInputEvent::IsTouchEventType(event.GetType())) {
DCHECK(event.GetType() == WebInputEvent::Type::kTouchMove);
const WebTouchEvent& touch_event = static_cast<const WebTouchEvent&>(event);
for (unsigned i = 0; i < touch_event.touches_length; ++i) {
if (touch_event.touches[i].state ==
blink::WebTouchPoint::State::kStateMoved) {
UpdateSinglePointer(touch_event.touches[i], touch_event.TimeStamp());
}
}
} else {
DCHECK(event.GetType() == WebInputEvent::Type::kMouseMove ||
event.GetType() == WebInputEvent::Type::kPointerMove);
UpdateSinglePointer(*ToWebPointerProperties(&event), event.TimeStamp());
}
last_event_timestamp_ = event.TimeStamp();
}
void InputEventPrediction::ApplyResampling(base::TimeTicks frame_time,
WebInputEvent* event) {
base::TimeDelta prediction_delta = frame_time - event->TimeStamp();
base::TimeTicks predict_time;
if (event->GetType() == WebInputEvent::Type::kTouchMove) {
WebTouchEvent* touch_event = static_cast<WebTouchEvent*>(event);
for (unsigned i = 0; i < touch_event->touches_length; ++i) {
if (touch_event->touches[i].state ==
blink::WebTouchPoint::State::kStateMoved) {
if (auto* predictor = GetPredictor(touch_event->touches[i])) {
// When resampling, we don't want to predict too far away because the
// result will likely be inaccurate in that case. We then cut off the
// prediction to the MaxResampleTime for the predictor.
prediction_delta =
std::min(prediction_delta, predictor->MaxResampleTime());
predict_time = event->TimeStamp() + prediction_delta;
if (GetPointerPrediction(predict_time, &touch_event->touches[i]))
event->SetTimeStamp(predict_time);
}
}
}
} else {
WebPointerProperties* pointer_event = ToWebPointerProperties(event);
if (auto* predictor = GetPredictor(*pointer_event)) {
// Cutoff prediction if delta > MaxResampleTime
prediction_delta =
std::min(prediction_delta, predictor->MaxResampleTime());
predict_time = event->TimeStamp() + prediction_delta;
if (GetPointerPrediction(predict_time, pointer_event))
event->SetTimeStamp(predict_time);
}
}
}
void InputEventPrediction::ResetPredictor(const WebInputEvent& event) {
if (WebInputEvent::IsTouchEventType(event.GetType())) {
const WebTouchEvent& touch_event = static_cast<const WebTouchEvent&>(event);
for (unsigned i = 0; i < touch_event.touches_length; ++i) {
if (touch_event.touches[i].state !=
blink::WebTouchPoint::State::kStateMoved &&
touch_event.touches[i].state !=
blink::WebTouchPoint::State::kStateStationary)
pointer_id_predictor_map_.erase(touch_event.touches[i].id);
}
} else if (WebInputEvent::IsMouseEventType(event.GetType())) {
ResetSinglePredictor(static_cast<const WebMouseEvent&>(event));
} else if (WebInputEvent::IsPointerEventType(event.GetType())) {
ResetSinglePredictor(static_cast<const WebPointerEvent&>(event));
}
}
void InputEventPrediction::AddPredictedEvents(
blink::WebCoalescedInputEvent& coalesced_event) {
base::TimeTicks predict_time = last_event_timestamp_;
base::TimeTicks max_prediction_timestamp =
last_event_timestamp_ + mouse_predictor_->MaxPredictionTime();
bool success = true;
while (success) {
std::unique_ptr<WebInputEvent> predicted_event =
coalesced_event.Event().Clone();
success = false;
if (predicted_event->GetType() == WebInputEvent::Type::kTouchMove) {
WebTouchEvent& touch_event =
static_cast<WebTouchEvent&>(*predicted_event);
// Average all touch intervals
base::TimeDelta touch_time_interval;
for (unsigned i = 0; i < touch_event.touches_length; ++i) {
touch_time_interval +=
GetPredictionTimeInterval(touch_event.touches[i]);
}
predict_time += touch_time_interval / touch_event.touches_length;
if (predict_time <= max_prediction_timestamp) {
for (unsigned i = 0; i < touch_event.touches_length; ++i) {
if (touch_event.touches[i].state ==
blink::WebTouchPoint::State::kStateMoved) {
success =
GetPointerPrediction(predict_time, &touch_event.touches[i]);
}
}
}
} else {
WebPointerProperties* pointer_event =
ToWebPointerProperties(predicted_event.get());
predict_time += GetPredictionTimeInterval(*pointer_event);
success = predict_time <= max_prediction_timestamp &&
GetPointerPrediction(predict_time, pointer_event);
}
if (success) {
predicted_event->SetTimeStamp(predict_time);
coalesced_event.AddPredictedEvent(*predicted_event);
}
}
}
ui::InputPredictor* InputEventPrediction::GetPredictor(
const WebPointerProperties& event) const {
if (event.pointer_type == WebPointerProperties::PointerType::kMouse)
return mouse_predictor_.get();
auto predictor = pointer_id_predictor_map_.find(event.id);
if (predictor != pointer_id_predictor_map_.end())
return predictor->second.get();
return nullptr;
}
base::TimeDelta InputEventPrediction::GetPredictionTimeInterval(
const WebPointerProperties& event) const {
if (auto* predictor = GetPredictor(event))
return predictor->TimeInterval();
return mouse_predictor_->TimeInterval();
}
void InputEventPrediction::UpdateSinglePointer(
const WebPointerProperties& event,
base::TimeTicks event_time) {
ui::InputPredictor::InputData data = {event.PositionInWidget(), event_time};
if (auto* predictor = GetPredictor(event)) {
predictor->Update(data);
} else {
// Create new predictor.
auto pair = std::make_pair(event.id, CreatePredictor());
pointer_id_predictor_map_.insert(std::move(pair));
pointer_id_predictor_map_[event.id]->Update(data);
}
}
bool InputEventPrediction::GetPointerPrediction(base::TimeTicks predict_time,
WebPointerProperties* event) {
// Reset mouse predictor if pointer type is touch or stylus
if (event->pointer_type != WebPointerProperties::PointerType::kMouse)
mouse_predictor_->Reset();
if (auto* predictor = GetPredictor(*event)) {
if (auto predict_result = predictor->GeneratePrediction(predict_time)) {
event->SetPositionInWidget(predict_result->pos);
return true;
}
}
return false;
}
void InputEventPrediction::ResetSinglePredictor(
const WebPointerProperties& event) {
if (event.pointer_type == WebPointerProperties::PointerType::kMouse)
mouse_predictor_->Reset();
else
pointer_id_predictor_map_.erase(event.id);
}
} // namespace blink
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