dom/vr/XRSession.cpp

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   5  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #include "mozilla/dom/XRSession.h"
   8
   9 #include "mozilla/dom/XRSessionEvent.h"
  10 #include "mozilla/dom/XRInputSourceEvent.h"
  11 #include "mozilla/EventDispatcher.h"
  12 #include "mozilla/dom/DocumentInlines.h"
  13 #include "mozilla/dom/Promise.h"
  14 #include "XRSystem.h"
  15 #include "XRRenderState.h"
  16 #include "XRBoundedReferenceSpace.h"
  17 #include "XRFrame.h"
  18 #include "XRNativeOrigin.h"
  19 #include "XRNativeOriginFixed.h"
  20 #include "XRNativeOriginViewer.h"
  21 #include "XRNativeOriginLocal.h"
  22 #include "XRNativeOriginLocalFloor.h"
  23 #include "XRView.h"
  24 #include "XRViewerPose.h"
  25 #include "VRLayerChild.h"
  26 #include "XRInputSourceArray.h"
  27 #include "nsGlobalWindowInner.h"
  28 #include "nsIObserverService.h"
  29 #include "nsISupportsPrimitives.h"
  30 #include "nsRefreshDriver.h"
  31 #include "VRDisplayClient.h"
  32 #include "VRDisplayPresentation.h"
  33
  34 /**
  35  * Maximum instances of XRFrame and XRViewerPose objects
  36  * created in the pool.
  37  */
  38 const uint32_t kMaxPoolSize = 16;
  39
  40 namespace mozilla::dom {
  41
  42 NS_IMPL_CYCLE_COLLECTION_CLASS(XRSession)
  43
  44 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(XRSession,
  45                                                   DOMEventTargetHelper)
  46   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mXRSystem)
  47   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mActiveRenderState)
  48   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mPendingRenderState)
  49   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mInputSources)
  50   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mViewerPosePool)
  51   NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mFramePool)
  52
  53   for (uint32_t i = 0; i < tmp->mFrameRequestCallbacks.Length(); ++i) {
  54     NS_CYCLE_COLLECTION_NOTE_EDGE_NAME(cb, "mFrameRequestCallbacks[i]");
  55     cb.NoteXPCOMChild(tmp->mFrameRequestCallbacks[i].mCallback);
  56   }
  57
  58 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
  59
  60 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(XRSession, DOMEventTargetHelper)
  61   NS_IMPL_CYCLE_COLLECTION_UNLINK(mXRSystem)
  62   NS_IMPL_CYCLE_COLLECTION_UNLINK(mActiveRenderState)
  63   NS_IMPL_CYCLE_COLLECTION_UNLINK(mPendingRenderState)
  64   NS_IMPL_CYCLE_COLLECTION_UNLINK(mInputSources)
  65   NS_IMPL_CYCLE_COLLECTION_UNLINK(mViewerPosePool)
  66   NS_IMPL_CYCLE_COLLECTION_UNLINK(mFramePool)
  67
  68   tmp->mFrameRequestCallbacks.Clear();
  69
  70   // Don't need NS_IMPL_CYCLE_COLLECTION_UNLINK_PRESERVED_WRAPPER because
  71   // DOMEventTargetHelper does it for us.
  72 NS_IMPL_CYCLE_COLLECTION_UNLINK_END
  73
  74 NS_IMPL_ISUPPORTS_CYCLE_COLLECTION_INHERITED_0(XRSession, DOMEventTargetHelper)
  75
  76 already_AddRefed<XRSession> XRSession::CreateInlineSession(
  77     nsPIDOMWindowInner* aWindow, XRSystem* aXRSystem,
  78     const nsTArray<XRReferenceSpaceType>& aEnabledReferenceSpaceTypes) {
  79   nsGlobalWindowInner* win = nsGlobalWindowInner::Cast(aWindow);
  80   if (!win) {
  81     return nullptr;
  82   }
  83   Document* doc = aWindow->GetExtantDoc();
  84   if (!doc) {
  85     return nullptr;
  86   }
  87   nsPresContext* context = doc->GetPresContext();
  88   if (!context) {
  89     return nullptr;
  90   }
  91   nsRefreshDriver* driver = context->RefreshDriver();
  92   if (!driver) {
  93     return nullptr;
  94   }
  95
  96   RefPtr<XRSession> session =
  97       new XRSession(aWindow, aXRSystem, driver, nullptr, gfx::kVRGroupContent,
  98                     aEnabledReferenceSpaceTypes);
  99   driver->AddRefreshObserver(session, FlushType::Display, "XR Session");
 100   return session.forget();
 101 }
 102
 103 already_AddRefed<XRSession> XRSession::CreateImmersiveSession(
 104     nsPIDOMWindowInner* aWindow, XRSystem* aXRSystem,
 105     gfx::VRDisplayClient* aClient, uint32_t aPresentationGroup,
 106     const nsTArray<XRReferenceSpaceType>& aEnabledReferenceSpaceTypes) {
 107   RefPtr<XRSession> session =
 108       new XRSession(aWindow, aXRSystem, nullptr, aClient, aPresentationGroup,
 109                     aEnabledReferenceSpaceTypes);
 110   return session.forget();
 111 }
 112
 113 XRSession::XRSession(
 114     nsPIDOMWindowInner* aWindow, XRSystem* aXRSystem,
 115     nsRefreshDriver* aRefreshDriver, gfx::VRDisplayClient* aClient,
 116     uint32_t aPresentationGroup,
 117     const nsTArray<XRReferenceSpaceType>& aEnabledReferenceSpaceTypes)
 118     : DOMEventTargetHelper(aWindow),
 119       mXRSystem(aXRSystem),
 120       mShutdown(false),
 121       mEnded(false),
 122       mRefreshDriver(aRefreshDriver),
 123       mDisplayClient(aClient),
 124       mFrameRequestCallbackCounter(0),
 125       mEnabledReferenceSpaceTypes(aEnabledReferenceSpaceTypes.Clone()),
 126       mViewerPosePoolIndex(0),
 127       mFramePoolIndex(0) {
 128   if (aClient) {
 129     aClient->SessionStarted(this);
 130   }
 131   mActiveRenderState = new XRRenderState(aWindow, this);
 132   mStartTimeStamp = TimeStamp::Now();
 133   if (IsImmersive()) {
 134     mDisplayPresentation =
 135         mDisplayClient->BeginPresentation({}, aPresentationGroup);
 136   }
 137   if (mDisplayClient) {
 138     mDisplayClient->SetXRAPIMode(gfx::VRAPIMode::WebXR);
 139   }
 140   // TODO: Handle XR input sources are no longer available cases.
 141   // https://immersive-web.github.io/webxr/#dom-xrsession-inputsources
 142   mInputSources = new XRInputSourceArray(aWindow);
 143 }
 144
 145 XRSession::~XRSession() { MOZ_ASSERT(mShutdown); }
 146
 147 gfx::VRDisplayClient* XRSession::GetDisplayClient() const {
 148   return mDisplayClient;
 149 }
 150
 151 JSObject* XRSession::WrapObject(JSContext* aCx,
 152                                 JS::Handle<JSObject*> aGivenProto) {
 153   return XRSession_Binding::Wrap(aCx, this, aGivenProto);
 154 }
 155
 156 bool XRSession::IsEnded() const { return mEnded; }
 157
 158 already_AddRefed<Promise> XRSession::End(ErrorResult& aRv) {
 159   nsCOMPtr<nsIGlobalObject> global = GetParentObject();
 160   NS_ENSURE_TRUE(global, nullptr);
 161
 162   ExitPresentInternal();
 163
 164   RefPtr<Promise> promise = Promise::Create(global, aRv);
 165   NS_ENSURE_TRUE(!aRv.Failed(), nullptr);
 166
 167   promise->MaybeResolve(JS::UndefinedHandleValue);
 168
 169   return promise.forget();
 170 }
 171
 172 bool XRSession::IsImmersive() const {
 173   // Only immersive sessions have a VRDisplayClient
 174   return mDisplayClient != nullptr;
 175 }
 176
 177 XRVisibilityState XRSession::VisibilityState() const {
 178   return XRVisibilityState::Visible;
 179   // TODO (Bug 1609771): Implement changing visibility state
 180 }
 181
 182 // https://immersive-web.github.io/webxr/#poses-may-be-reported
 183 // Given that an XRSession cannot be requested without explicit consent
 184 // by the user, the only necessary check is whether the XRSession's
 185 // visiblityState is 'visible'.
 186 bool XRSession::CanReportPoses() const {
 187   return VisibilityState() == XRVisibilityState::Visible;
 188 }
 189
 190 // https://immersive-web.github.io/webxr/#dom-xrsession-updaterenderstate
 191 void XRSession::UpdateRenderState(const XRRenderStateInit& aNewState,
 192                                   ErrorResult& aRv) {
 193   if (mEnded) {
 194     aRv.ThrowInvalidStateError(
 195         "UpdateRenderState can not be called on an XRSession that has ended.");
 196     return;
 197   }
 198   if (aNewState.mBaseLayer.WasPassed() &&
 199       aNewState.mBaseLayer.Value()->mSession != this) {
 200     aRv.ThrowInvalidStateError(
 201         "The baseLayer passed in to UpdateRenderState must "
 202         "belong to the XRSession that UpdateRenderState is "
 203         "being called on.");
 204     return;
 205   }
 206   if (aNewState.mInlineVerticalFieldOfView.WasPassed() && IsImmersive()) {
 207     aRv.ThrowInvalidStateError(
 208         "The inlineVerticalFieldOfView can not be set on an "
 209         "XRRenderState for an immersive XRSession.");
 210     return;
 211   }
 212   if (mPendingRenderState == nullptr) {
 213     mPendingRenderState = new XRRenderState(*mActiveRenderState);
 214   }
 215   if (aNewState.mDepthNear.WasPassed()) {
 216     mPendingRenderState->SetDepthNear(aNewState.mDepthNear.Value());
 217   }
 218   if (aNewState.mDepthFar.WasPassed()) {
 219     mPendingRenderState->SetDepthFar(aNewState.mDepthFar.Value());
 220   }
 221   if (aNewState.mInlineVerticalFieldOfView.WasPassed()) {
 222     mPendingRenderState->SetInlineVerticalFieldOfView(
 223         aNewState.mInlineVerticalFieldOfView.Value());
 224   }
 225   if (aNewState.mBaseLayer.WasPassed()) {
 226     mPendingRenderState->SetBaseLayer(aNewState.mBaseLayer.Value());
 227   }
 228 }
 229
 230 XRRenderState* XRSession::RenderState() { return mActiveRenderState; }
 231
 232 XRInputSourceArray* XRSession::InputSources() { return mInputSources; }
 233
 234 Nullable<float> XRSession::GetFrameRate() { return {}; }
 235
 236 void XRSession::GetSupportedFrameRates(JSContext*,
 237                                        JS::MutableHandle<JSObject*> aRetVal) {
 238   aRetVal.set(nullptr);
 239 }
 240
 241 // https://immersive-web.github.io/webxr/#apply-the-pending-render-state
 242 void XRSession::ApplyPendingRenderState() {
 243   if (mPendingRenderState == nullptr) {
 244     return;
 245   }
 246   mActiveRenderState = mPendingRenderState;
 247   mPendingRenderState = nullptr;
 248
 249   // https://immersive-web.github.io/webxr/#minimum-inline-field-of-view
 250   const double kMinimumInlineVerticalFieldOfView = 0.0f;
 251
 252   // https://immersive-web.github.io/webxr/#maximum-inline-field-of-view
 253   const double kMaximumInlineVerticalFieldOfView = M_PI;
 254
 255   if (!mActiveRenderState->GetInlineVerticalFieldOfView().IsNull()) {
 256     double verticalFOV =
 257         mActiveRenderState->GetInlineVerticalFieldOfView().Value();
 258     if (verticalFOV < kMinimumInlineVerticalFieldOfView) {
 259       verticalFOV = kMinimumInlineVerticalFieldOfView;
 260     }
 261     if (verticalFOV > kMaximumInlineVerticalFieldOfView) {
 262       verticalFOV = kMaximumInlineVerticalFieldOfView;
 263     }
 264     mActiveRenderState->SetInlineVerticalFieldOfView(verticalFOV);
 265   }
 266
 267   // Our minimum near plane value is set to a small value close but not equal to
 268   // zero (kEpsilon) The maximum far plane is infinite.
 269   const float kEpsilon = 0.00001f;
 270   double depthNear = mActiveRenderState->DepthNear();
 271   double depthFar = mActiveRenderState->DepthFar();
 272   if (depthNear < 0.0f) {
 273     depthNear = 0.0f;
 274   }
 275   if (depthFar < 0.0f) {
 276     depthFar = 0.0f;
 277   }
 278   // Ensure at least a small distance between the near and far planes
 279   if (fabs(depthFar - depthNear) < kEpsilon) {
 280     depthFar = depthNear + kEpsilon;
 281   }
 282   mActiveRenderState->SetDepthNear(depthNear);
 283   mActiveRenderState->SetDepthFar(depthFar);
 284
 285   XRWebGLLayer* baseLayer = mActiveRenderState->GetBaseLayer();
 286   if (baseLayer) {
 287     if (!IsImmersive() && baseLayer->mCompositionDisabled) {
 288       mActiveRenderState->SetCompositionDisabled(true);
 289       mActiveRenderState->SetOutputCanvas(baseLayer->GetCanvas());
 290     } else {
 291       mActiveRenderState->SetCompositionDisabled(false);
 292       mActiveRenderState->SetOutputCanvas(nullptr);
 293       mDisplayPresentation->UpdateXRWebGLLayer(baseLayer);
 294     }
 295   }  // if (baseLayer)
 296 }
 297
 298 void XRSession::WillRefresh(mozilla::TimeStamp aTime) {
 299   // Inline sessions are driven by nsRefreshDriver directly,
 300   // unlike immersive sessions, which are driven VRDisplayClient.
 301   if (!IsImmersive() && !mXRSystem->HasActiveImmersiveSession()) {
 302     nsGlobalWindowInner* win = nsGlobalWindowInner::Cast(GetOwner());
 303     if (win) {
 304       if (JSObject* obj = win->AsGlobal()->GetGlobalJSObject()) {
 305         js::NotifyAnimationActivity(obj);
 306       }
 307     }
 308     StartFrame();
 309   }
 310 }
 311
 312 void XRSession::StartFrame() {
 313   if (mShutdown || mEnded) {
 314     return;
 315   }
 316   ApplyPendingRenderState();
 317
 318   XRWebGLLayer* baseLayer = mActiveRenderState->GetBaseLayer();
 319   if (!baseLayer) {
 320     return;
 321   }
 322
 323   if (!IsImmersive() && mActiveRenderState->GetOutputCanvas() == nullptr) {
 324     return;
 325   }
 326
 327   // Determine timestamp for the callbacks
 328   TimeStamp nowTime = TimeStamp::Now();
 329   mozilla::TimeDuration duration = nowTime - mStartTimeStamp;
 330   DOMHighResTimeStamp timeStamp = duration.ToMilliseconds();
 331
 332   // Create an XRFrame for the callbacks
 333   RefPtr<XRFrame> frame = PooledFrame();
 334   frame->StartAnimationFrame();
 335
 336   baseLayer->StartAnimationFrame();
 337   nsTArray<XRFrameRequest> callbacks;
 338   callbacks.AppendElements(mFrameRequestCallbacks);
 339   mFrameRequestCallbacks.Clear();
 340   for (auto& callback : callbacks) {
 341     callback.Call(timeStamp, *frame);
 342   }
 343
 344   baseLayer->EndAnimationFrame();
 345   frame->EndAnimationFrame();
 346   if (mDisplayPresentation) {
 347     mDisplayPresentation->SubmitFrame();
 348   }
 349 }
 350
 351 void XRSession::ExitPresent() { ExitPresentInternal(); }
 352
 353 already_AddRefed<Promise> XRSession::RequestReferenceSpace(
 354     const XRReferenceSpaceType& aReferenceSpaceType, ErrorResult& aRv) {
 355   nsCOMPtr<nsIGlobalObject> global = GetParentObject();
 356   NS_ENSURE_TRUE(global, nullptr);
 357
 358   RefPtr<Promise> promise = Promise::Create(global, aRv);
 359   NS_ENSURE_TRUE(!aRv.Failed(), nullptr);
 360
 361   if (!mEnabledReferenceSpaceTypes.Contains(aReferenceSpaceType)) {
 362     promise->MaybeRejectWithNotSupportedError(nsLiteralCString(
 363         "Requested XRReferenceSpaceType not available for the XRSession."));
 364     return promise.forget();
 365   }
 366   RefPtr<XRReferenceSpace> space;
 367   RefPtr<XRNativeOrigin> nativeOrigin;
 368   if (mDisplayClient) {
 369     switch (aReferenceSpaceType) {
 370       case XRReferenceSpaceType::Viewer:
 371         nativeOrigin = new XRNativeOriginViewer(mDisplayClient);
 372         break;
 373       case XRReferenceSpaceType::Local:
 374         nativeOrigin = new XRNativeOriginLocal(mDisplayClient);
 375         break;
 376       case XRReferenceSpaceType::Local_floor:
 377       case XRReferenceSpaceType::Bounded_floor:
 378         nativeOrigin = new XRNativeOriginLocalFloor(mDisplayClient);
 379         break;
 380       default:
 381         nativeOrigin = new XRNativeOriginFixed(gfx::PointDouble3D());
 382         break;
 383     }
 384   } else {
 385     // We currently only support XRReferenceSpaceType::Viewer when
 386     // there is no XR hardware.  In this case, the native origin
 387     // will always be at {0, 0, 0} which will always be the same
 388     // as the 'tracked' position of the non-existant pose.
 389     MOZ_ASSERT(aReferenceSpaceType == XRReferenceSpaceType::Viewer);
 390     nativeOrigin = new XRNativeOriginFixed(gfx::PointDouble3D());
 391   }
 392   if (aReferenceSpaceType == XRReferenceSpaceType::Bounded_floor) {
 393     space = new XRBoundedReferenceSpace(GetParentObject(), this, nativeOrigin);
 394   } else {
 395     space = new XRReferenceSpace(GetParentObject(), this, nativeOrigin,
 396                                  aReferenceSpaceType);
 397   }
 398
 399   promise->MaybeResolve(space);
 400   return promise.forget();
 401 }
 402
 403 already_AddRefed<Promise> XRSession::UpdateTargetFrameRate(float aRate,
 404                                                            ErrorResult& aRv) {
 405   nsCOMPtr<nsIGlobalObject> global = GetParentObject();
 406   NS_ENSURE_TRUE(global, nullptr);
 407
 408   RefPtr<Promise> promise = Promise::Create(global, aRv);
 409   NS_ENSURE_TRUE(!aRv.Failed(), nullptr);
 410
 411   if (mEnded) {
 412     promise->MaybeRejectWithInvalidStateError(
 413         "UpdateTargetFrameRate can not be called on an XRSession that has "
 414         "ended.");
 415     return promise.forget();
 416   }
 417
 418   // https://immersive-web.github.io/webxr/#dom-xrsession-updatetargetframerate
 419   // TODO: Validate the rate with the frame rates supported from the device.
 420   // We add a no op for now to avoid JS exceptions related to undefined method.
 421   // The spec states that user agent MAY use rate to calculate a new display
 422   // frame rate, so it's fine to let the default frame rate for now.
 423
 424   promise->MaybeResolve(JS::UndefinedHandleValue);
 425   return promise.forget();
 426 }
 427
 428 XRRenderState* XRSession::GetActiveRenderState() const {
 429   return mActiveRenderState;
 430 }
 431
 432 void XRSession::XRFrameRequest::Call(const DOMHighResTimeStamp& aTimeStamp,
 433                                      XRFrame& aFrame) {
 434   RefPtr<mozilla::dom::XRFrameRequestCallback> callback = mCallback;
 435   callback->Call(aTimeStamp, aFrame);
 436 }
 437
 438 int32_t XRSession::RequestAnimationFrame(XRFrameRequestCallback& aCallback,
 439                                          ErrorResult& aError) {
 440   if (mShutdown) {
 441     return 0;
 442   }
 443
 444   int32_t handle = ++mFrameRequestCallbackCounter;
 445
 446   mFrameRequestCallbacks.AppendElement(XRFrameRequest(aCallback, handle));
 447
 448   return handle;
 449 }
 450
 451 void XRSession::CancelAnimationFrame(int32_t aHandle, ErrorResult& aError) {
 452   mFrameRequestCallbacks.RemoveElementSorted(aHandle);
 453 }
 454
 455 void XRSession::Shutdown() {
 456   mShutdown = true;
 457   ExitPresentInternal();
 458   mViewerPosePool.Clear();
 459   mViewerPosePoolIndex = 0;
 460   mFramePool.Clear();
 461   mFramePoolIndex = 0;
 462   mActiveRenderState = nullptr;
 463   mPendingRenderState = nullptr;
 464   mFrameRequestCallbacks.Clear();
 465
 466   // Unregister from nsRefreshObserver
 467   if (mRefreshDriver) {
 468     mRefreshDriver->RemoveRefreshObserver(this, FlushType::Display);
 469     mRefreshDriver = nullptr;
 470   }
 471 }
 472
 473 void XRSession::ExitPresentInternal() {
 474   if (mInputSources) {
 475     mInputSources->Clear(this);
 476   }
 477   if (mDisplayClient) {
 478     mDisplayClient->SessionEnded(this);
 479   }
 480
 481   if (mXRSystem) {
 482     mXRSystem->SessionEnded(this);
 483   }
 484
 485   if (mActiveRenderState) {
 486     mActiveRenderState->SessionEnded();
 487   }
 488
 489   if (mPendingRenderState) {
 490     mPendingRenderState->SessionEnded();
 491   }
 492
 493   mDisplayPresentation = nullptr;
 494   if (!mEnded) {
 495     mEnded = true;
 496
 497     XRSessionEventInit init;
 498     init.mBubbles = false;
 499     init.mCancelable = false;
 500     init.mSession = this;
 501     RefPtr<XRSessionEvent> event =
 502         XRSessionEvent::Constructor(this, u"end"_ns, init);
 503
 504     event->SetTrusted(true);
 505     this->DispatchEvent(*event);
 506   }
 507 }
 508
 509 void XRSession::DisconnectFromOwner() {
 510   MOZ_ASSERT(NS_IsMainThread());
 511   Shutdown();
 512   DOMEventTargetHelper::DisconnectFromOwner();
 513 }
 514
 515 void XRSession::LastRelease() {
 516   // We don't want to wait for the GC to free up the presentation
 517   // for use in other documents, so we do this in LastRelease().
 518   Shutdown();
 519 }
 520
 521 RefPtr<XRViewerPose> XRSession::PooledViewerPose(
 522     const gfx::Matrix4x4Double& aTransform, bool aEmulatedPosition) {
 523   RefPtr<XRViewerPose> pose;
 524   if (mViewerPosePool.Length() > mViewerPosePoolIndex) {
 525     pose = mViewerPosePool.ElementAt(mViewerPosePoolIndex);
 526     pose->Transform()->Update(aTransform);
 527     pose->SetEmulatedPosition(aEmulatedPosition);
 528   } else {
 529     RefPtr<XRRigidTransform> transform = new XRRigidTransform(this, aTransform);
 530     nsTArray<RefPtr<XRView>> views;
 531     if (IsImmersive()) {
 532       views.AppendElement(new XRView(GetParentObject(), XREye::Left));
 533       views.AppendElement(new XRView(GetParentObject(), XREye::Right));
 534     } else {
 535       views.AppendElement(new XRView(GetParentObject(), XREye::None));
 536     }
 537     pose = new XRViewerPose(this, transform, aEmulatedPosition, views);
 538     mViewerPosePool.AppendElement(pose);
 539   }
 540
 541   mViewerPosePoolIndex++;
 542   if (mViewerPosePoolIndex >= kMaxPoolSize) {
 543     mViewerPosePoolIndex = 0;
 544   }
 545
 546   return pose;
 547 }
 548
 549 RefPtr<XRFrame> XRSession::PooledFrame() {
 550   RefPtr<XRFrame> frame;
 551   if (mFramePool.Length() > mFramePoolIndex) {
 552     frame = mFramePool.ElementAt(mFramePoolIndex);
 553   } else {
 554     frame = new XRFrame(GetParentObject(), this);
 555     mFramePool.AppendElement(frame);
 556   }
 557
 558   return frame;
 559 }
 560
 561 }  // namespace mozilla::dom