Remove Sync GetPose VRService call, implement VRVSyncProvider

chrome/browser/android/vr_shell/non_presenting_gvr_delegate.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/android/vr_shell/non_presenting_gvr_delegate.h"
+
+#include "chrome/browser/android/vr_shell/vr_shell.h"
+
+namespace vr_shell {
+
+namespace {
+static constexpr long kPredictionTimeWithoutVsyncNanos = 50000000;
+}  // namespace
+
+NonPresentingGvrDelegate::NonPresentingGvrDelegate(long context)
+    : task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      binding_(this),
+      weak_ptr_factory_(this) {
+  gvr_api_ = gvr::GvrApi::WrapNonOwned(reinterpret_cast<gvr_context*>(context));
+}
+
+NonPresentingGvrDelegate::~NonPresentingGvrDelegate() {
+  StopVSyncLoop();
+  if (binding_.is_bound())
+    binding_.Close();

[dcheng, 2017/01/18 23:46:06]

Nit: Close() already checks this, so just unconditionally Close(). Similar
comment for most other is_bound() checks.

(It's also unclear to me why this needs to explicitly call Close; shouldn't the
dtor automatically do that?)

[mthiesse, 2017/01/19 00:19:05]

haha it probably does, I was erring a little too far on the side of caution.
Done.

+}
+
+void NonPresentingGvrDelegate::OnVRVsyncProviderRequest(
+    device::mojom::VRVSyncProviderRequest request) {
+  if (binding_.is_bound())
+    binding_.Close();
+  binding_.Bind(std::move(request));
+  binding_.set_connection_error_handler(
+      base::Bind(&NonPresentingGvrDelegate::StopVSyncLoop,
+                 weak_ptr_factory_.GetWeakPtr()));
+  StartVSyncLoop();
+}
+
+void NonPresentingGvrDelegate::Pause() {
+  vsync_task_.Cancel();
+  paused_ = true;
+  gvr_api_->PauseTracking();
+}
+
+void NonPresentingGvrDelegate::Resume() {
+  if (!paused_)
+    return;
+  paused_ = false;
+  StartVSyncLoop();
+}
+
+device::mojom::VRVSyncProviderRequest
+NonPresentingGvrDelegate::OnSwitchToPresentingDelegate() {
+  StopVSyncLoop();
+  if (binding_.is_bound())
+    return binding_.Unbind();
+  return nullptr;
+}
+
+void NonPresentingGvrDelegate::StopVSyncLoop() {
+  vsync_task_.Cancel();
+  if (!callback_.is_null())
+    callback_.Run(nullptr, base::TimeDelta());
+  callback_.Reset();
+  gvr_api_->PauseTracking();
+  paused_ = false;

[dcheng, 2017/01/18 23:46:06]

Nit: minor comment about why paused_ = false is correct here would be nice
(Pause() sets it to true, so it's unclear why this should be the opposite)

[mthiesse, 2017/01/19 00:19:05]

Renamed and added clarifying comment.

+}
+
+void NonPresentingGvrDelegate::StartVSyncLoop() {
+  vsync_task_.Reset(
+      base::Bind(&NonPresentingGvrDelegate::OnVSync, base::Unretained(this)));
+  gvr_api_->RefreshViewerProfile();
+  gvr_api_->ResumeTracking();
+  OnVSync();
+}
+
+void NonPresentingGvrDelegate::OnVSync() {
+  base::TimeTicks now = base::TimeTicks::Now();
+  base::TimeTicks target;
+
+  // Don't run the VSync loop if we're not bound.
+  if (!binding_.is_bound()) {
+    return;
+  }
+
+  // Don't send VSyncs until we have a timebase/interval.
+  if (vsync_interval_.is_zero())
+    return;
+  target = now + vsync_interval_;
+  int64_t intervals = (target - vsync_timebase_) / vsync_interval_;
+  target = vsync_timebase_ + intervals * vsync_interval_;
+  if (!vsync_task_.IsCancelled()) {
+    task_runner_->PostDelayedTask(FROM_HERE, vsync_task_.callback(),
+                                  target - now);
+  }
+
+  base::TimeDelta time = intervals * vsync_interval_;
+  if (!callback_.is_null()) {
+    callback_.Run(GetPose(), time);
+    callback_.Reset();
+  } else {
+    pending_vsync_ = true;
+    pending_time_ = time;
+  }
+}
+
+void NonPresentingGvrDelegate::GetVSync(const GetVSyncCallback& callback) {
+  if (!pending_vsync_) {
+    if (!callback_.is_null()) {
+      mojo::ReportBadMessage("Requested VSync before waiting for response to "
+          "previous request.");
+      return;
+    }
+    callback_ = std::move(callback);

[dcheng, 2017/01/18 23:46:06]

Nit: |callback| is a const ref, so std::move() doesn't do anything.

[mthiesse, 2017/01/19 00:19:05]

Done.

+    return;
+  }
+  pending_vsync_ = false;
+  callback.Run(GetPose(), pending_time_);
+}
+
+void NonPresentingGvrDelegate::UpdateVSyncInterval(long timebase_nanos,
+                                                   double interval_seconds) {
+  vsync_timebase_ = base::TimeTicks();
+  vsync_timebase_ += base::TimeDelta::FromMicroseconds(timebase_nanos / 1000);
+  vsync_interval_ = base::TimeDelta::FromSecondsD(interval_seconds);
+  StartVSyncLoop();
+}
+
+device::mojom::VRPosePtr NonPresentingGvrDelegate::GetPose() {
+  gvr::ClockTimePoint target_time = gvr::GvrApi::GetTimePointNow();
+  target_time.monotonic_system_time_nanos += kPredictionTimeWithoutVsyncNanos;
+
+  gvr::Mat4f head_mat =
+      gvr_api_->GetHeadSpaceFromStartSpaceRotation(target_time);
+  head_mat = gvr_api_->ApplyNeckModel(head_mat, 1.0f);
+
+  uint32_t pose_index = pose_index_++;
+
+  return VrShell::VRPosePtrFromGvrPose(head_mat, pose_index);
+}
+
+}  // namespace vr_shell