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vsync_waiter_fallback should schedule firecallback for future #28817

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Sep 29, 2021
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vsync_waiter_fallback should schedule firecallback for future #28817

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2db5060
vsync_waiter_fallback should schedule firecallback for future
iskakaushik Sep 23, 2021
83dfdbd
Post at a later time from the same task runner
iskakaushik Sep 27, 2021
3d8bffa
address CR comments
iskakaushik Sep 29, 2021
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9 changes: 6 additions & 3 deletions shell/common/vsync_waiter.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -7,8 +7,10 @@
#include "flow/frame_timings.h"
#include "flutter/fml/task_runner.h"
#include "flutter/fml/trace_event.h"
#include "fml/logging.h"
#include "fml/message_loop_task_queues.h"
#include "fml/task_queue_id.h"
#include "fml/time/time_point.h"

namespace flutter {

Expand Down Expand Up @@ -95,6 +97,8 @@ void VsyncWaiter::ScheduleSecondaryCallback(uintptr_t id,
void VsyncWaiter::FireCallback(fml::TimePoint frame_start_time,
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@chinmaygarde chinmaygarde Sep 29, 2021

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In the headerdocs for this protected method, can you document that this subclasses must invoke this at (or close to because of scheduling overhead), the frame start time? Also, can you drop a note in the PR commit message that says verification of all vsync waiter subclasses was done to account for the new assertion for the start time requirements in FireCallback.

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@iskakaushik iskakaushik Sep 29, 2021

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Done! will also add the comment when I merge.

fml::TimePoint frame_target_time,
bool pause_secondary_tasks) {
FML_DCHECK(fml::TimePoint::Now() >= frame_start_time);

Callback callback;
std::vector<fml::closure> secondary_callbacks;

Expand Down Expand Up @@ -137,7 +141,7 @@ void VsyncWaiter::FireCallback(fml::TimePoint frame_start_time,
ui_task_queue_id = task_runners_.GetUITaskRunner()->GetTaskQueueId();
}

task_runners_.GetUITaskRunner()->PostTaskForTime(
task_runners_.GetUITaskRunner()->PostTask(
[ui_task_queue_id, callback, flow_identifier, frame_start_time,
frame_target_time, pause_secondary_tasks]() {
FML_TRACE_EVENT("flutter", kVsyncTraceName, "StartTime",
Expand All @@ -151,8 +155,7 @@ void VsyncWaiter::FireCallback(fml::TimePoint frame_start_time,
if (pause_secondary_tasks) {
ResumeDartMicroTasks(ui_task_queue_id);
}
},
frame_start_time);
});
}

for (auto& secondary_callback : secondary_callbacks) {
Expand Down
2 changes: 2 additions & 0 deletions shell/common/vsync_waiter.h
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Original file line number Diff line number Diff line change
Expand Up @@ -65,6 +65,8 @@ class VsyncWaiter : public std::enable_shared_from_this<VsyncWaiter> {
// as AwaitVSync().
virtual void AwaitVSyncForSecondaryCallback() { AwaitVSync(); }

// Schedules the callback on the UI task runner. Needs to be invoked as close
// to the `frame_start_time` as possible.
void FireCallback(fml::TimePoint frame_start_time,
fml::TimePoint frame_target_time,
bool pause_secondary_tasks = true);
Expand Down
20 changes: 16 additions & 4 deletions shell/common/vsync_waiter_fallback.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,10 @@

#include "flutter/shell/common/vsync_waiter_fallback.h"

#include <memory>

#include "flutter/fml/logging.h"
#include "flutter/fml/message_loop.h"
#include "flutter/fml/trace_event.h"

namespace flutter {
Expand Down Expand Up @@ -35,11 +38,20 @@ void VsyncWaiterFallback::AwaitVSync() {

constexpr fml::TimeDelta kSingleFrameInterval =
fml::TimeDelta::FromSecondsF(1.0 / 60.0);

auto next =
auto frame_start_time =
SnapToNextTick(fml::TimePoint::Now(), phase_, kSingleFrameInterval);

FireCallback(next, next + kSingleFrameInterval, !for_testing_);
auto frame_target_time = frame_start_time + kSingleFrameInterval;
std::weak_ptr<VsyncWaiterFallback> weak_this =
std::static_pointer_cast<VsyncWaiterFallback>(shared_from_this());

task_runners_.GetUITaskRunner()->PostTaskForTime(
[frame_start_time, frame_target_time, weak_this]() {
if (auto vsync_waiter = weak_this.lock()) {
vsync_waiter->FireCallback(frame_start_time, frame_target_time,
!vsync_waiter->for_testing_);
}
},
frame_start_time);
}

} // namespace flutter