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// Copyright 2016 The Cobalt Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "cobalt/renderer/submission_queue.h"
#include <cmath>
#include <memory>
#include "base/logging.h"
#include "base/strings/string_number_conversions.h"
#include "base/trace_event/trace_event.h"
#include "cobalt/base/polymorphic_downcast.h"
#include "cobalt/render_tree/animations/animate_node.h"
namespace cobalt {
namespace renderer {
// The maximum change (in units of ms/s) of to_submission_time_in_ms_. This
// value must be less than 1000ms/s, or else it might be possible to adjust
// our render time/submission time offset by less than -1 second per second,
// meaning that we would move backwards in time. We keep this at a healthy
// value of 800ms. This also acts as a crude form of regularization.
const double kMaxSlopeMagnitude = 800.0;
SubmissionQueue::SubmissionQueue(
size_t max_queue_size, base::TimeDelta time_to_converge,
bool allow_latency_reduction,
const DisposeSubmissionFunction& dispose_function)
: max_queue_size_(max_queue_size),
dispose_function_(dispose_function),
to_submission_time_in_ms_(time_to_converge, kMaxSlopeMagnitude),
to_submission_time_cval_(
"Renderer.ToSubmissionTime", base::TimeDelta(),
"The current difference in milliseconds between the layout's clock "
"and the renderer's clock. The absolute value does not mean much, "
"but how it changes as the user navigates can show how the "
"renderer's clock changes relative to layout's clock."),
queue_size_(
"Renderer.SubmissionQueueSize", 0,
"The current size of the renderer submission queue. Each item in "
"queue contains a render tree and associated animations."),
allow_latency_reduction_(allow_latency_reduction) {}
void SubmissionQueue::PushSubmission(const Submission& submission,
const base::TimeTicks& now) {
TRACE_EVENT0("cobalt::renderer", "SubmissionQueue::PushSubmission()");
if (!submission_queue_.empty()) {
CheckThatNowIsMonotonicallyIncreasing(now);
}
if (submission_queue_.size() >= max_queue_size_) {
// If we are at capacity, then make room for the new submission by erasing
// our first element.
submission_queue_.pop_front();
// Ensure that the next oldest item in the queue is older than the current
// time. If this is not the case, snap time forward so that it is.
double to_front_submission_time_in_ms =
(submission_queue_.front().time_offset - render_time(now))
.InMillisecondsF();
if (to_submission_time_in_ms_.GetValueAtTime(now) <
to_front_submission_time_in_ms) {
to_submission_time_in_ms_.SetTarget(to_front_submission_time_in_ms, now);
to_submission_time_in_ms_.SnapToTarget();
}
}
base::TimeDelta latest_to_submission_time =
submission.time_offset - render_time(now);
double latest_to_submission_time_in_ms =
latest_to_submission_time.InMillisecondsF();
// Update our mapping from render time to submission time.
if (allow_latency_reduction_ || submission_queue_.empty() ||
to_submission_time_in_ms_.GetValueAtTime(now) >
latest_to_submission_time_in_ms) {
to_submission_time_in_ms_.SetTarget(latest_to_submission_time_in_ms, now);
}
// Snap time to the new submission if no existing animations are playing both
// currently and during the time that we are snapping to.
if (submission_queue_.size() == 1 &&
submission_queue_.front().render_tree->GetTypeId() ==
base::GetTypeId<render_tree::animations::AnimateNode>()) {
render_tree::animations::AnimateNode* animate_node =
base::polymorphic_downcast<render_tree::animations::AnimateNode*>(
submission_queue_.front().render_tree.get());
// Check the expiration of only animations that depend on the time
// parameter, since they are the only ones that will be affected by snapping
// time.
if (animate_node->depends_on_time_expiry() <= submission_time(now) &&
animate_node->depends_on_time_expiry() <=
latest_to_submission_time + render_time(now)) {
to_submission_time_in_ms_.SnapToTarget();
}
}
// Save the new submission.
submission_queue_.push_back(submission);
// Possibly purge old stale submissions.
PurgeStaleSubmissionsFromQueue(now);
}
Submission SubmissionQueue::GetCurrentSubmission(const base::TimeTicks& now) {
TRACE_EVENT0("cobalt::renderer", "SubmissionQueue::GetCurrentSubmission()");
CheckThatNowIsMonotonicallyIncreasing(now);
DCHECK(!submission_queue_.empty());
// First get rid of any stale submissions from our queue.
PurgeStaleSubmissionsFromQueue(now);
// Create a new submission with an updated time offset to account for the
// fact that time has passed since it was submitted.
Submission updated_time_submission(submission_queue_.front());
// Our current clock should always be setup (via PushSubmission()) such
// that it is always larger than the front of the queue.
DCHECK_GE(to_submission_time_in_ms_.GetValueAtTime(now),
(submission_queue_.front().time_offset - render_time(now))
.InMillisecondsF());
base::TimeDelta updated_time = submission_time(now);
// This if statement is very similar to the DCHECK above, but not exactly
// the same because of rounding issues.
if (updated_time > updated_time_submission.time_offset) {
updated_time_submission.time_offset = updated_time;
}
return updated_time_submission;
}
base::TimeDelta SubmissionQueue::render_time(const base::TimeTicks& time) {
if (!renderer_time_origin_) {
renderer_time_origin_ = time;
}
return time - *renderer_time_origin_;
}
base::TimeDelta SubmissionQueue::submission_time(const base::TimeTicks& time) {
return base::TimeDelta::FromMillisecondsD(
to_submission_time_in_ms_.GetValueAtTime(time)) +
render_time(time);
}
void SubmissionQueue::PurgeStaleSubmissionsFromQueue(
const base::TimeTicks& time) {
TRACE_EVENT0("cobalt::renderer",
"SubmissionQueue::PurgeStaleSubmissionsFromQueue()");
double current_to_submission_time_in_ms =
to_submission_time_in_ms_.GetValueAtTime(time);
SubmissionQueueInternal::iterator submission = submission_queue_.end();
--submission;
// If there is more than one element in the queue...
if (submission != submission_queue_.begin()) {
// Skip past the submissions that are in the future. This means we start
// from the back because the queue is sorted in ascending order of time.
while (current_to_submission_time_in_ms <
(submission->time_offset - render_time(time)).InMillisecondsF()) {
if (submission == submission_queue_.begin()) {
// It is an invariant of this class that the oldest submission in the
// queue is older than the current render time. This should be
// managed within PushSubmission().
NOTREACHED();
break;
}
--submission;
}
}
// Delete all previous, old render trees.
while (submission_queue_.begin() != submission) {
TRACE_EVENT0("cobalt::renderer", "Delete Render Tree Submission");
if (!dispose_function_.is_null()) {
// Package the submission for sending to the disposal callback function.
// We erase it from our queue before calling the callback in order to
// ensure that the callback disposes of the Submission object after we
// do.
std::unique_ptr<Submission> submission(
new Submission(submission_queue_.front()));
submission_queue_.pop_front();
dispose_function_.Run(std::move(submission));
} else {
// If no callback is passed in to dispose of submissions for us, just
// delete it immediately.
submission_queue_.pop_front();
}
}
// Update our CVal tracking the current (smoothed) to_submission_time value
// and the one tracking submission queue size.
to_submission_time_cval_ = base::TimeDelta::FromMilliseconds(
to_submission_time_in_ms_.GetValueAtTime(time));
queue_size_ = submission_queue_.size();
}
void SubmissionQueue::CheckThatNowIsMonotonicallyIncreasing(
const base::TimeTicks& now) {
if (last_now_) {
DCHECK(now >= *last_now_);
}
last_now_ = now;
}
} // namespace renderer
} // namespace cobalt