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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/viz/service/frame_sinks/begin_frame_tracker.h"
namespace viz {
void BeginFrameTracker::SentBeginFrame(const BeginFrameArgs& args) {
++outstanding_begin_frames_;
last_frame_id_ = args.frame_id;
}
void BeginFrameTracker::ReceivedAck(const BeginFrameAck& ack) {
if (MatchesLastSent(ack)) {
// If the BeginFrameAck matches the last sent BeginFrameArgs then we know
// the client has read every message from the pipe. While the client
// should send an ack for every args, this guards against bugs that make a
// responsive client occasional drop a begin frame with no ack. Otherwise
// the occasional dropped ack would add up and eventually throttle then
// stop sending begin frames entirely.
outstanding_begin_frames_ = 0;
} else if (outstanding_begin_frames_ > 0) {
// The condition above makes it such that we aren't necessarily evenly
// incrementing/decrementing |outstanding_begin_frames_|, so ensure it
// never goes negative.
--outstanding_begin_frames_;
}
}
bool BeginFrameTracker::ShouldThrottleBeginFrame() const {
return outstanding_begin_frames_ >= kLimitThrottle &&
outstanding_begin_frames_ < kLimitStop;
}
bool BeginFrameTracker::ShouldStopBeginFrame() const {
return outstanding_begin_frames_ >= kLimitStop;
}
bool BeginFrameTracker::MatchesLastSent(const BeginFrameAck& ack) {
return last_frame_id_ == ack.frame_id;
}
} // namespace viz
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