Encode frame number in pixel data for pose sync

third_party/WebKit/Source/modules/vr/VRPose.h

 // Copyright 2015 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.
 
 #ifndef VRPose_h
 #define VRPose_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/dom/DOMTypedArray.h"
 #include "device/vr/vr_service.mojom-blink.h"
 #include "platform/heap/Handle.h"
 #include "wtf/Forward.h"
 
 namespace blink {
 
 class VRPose final : public GarbageCollected<VRPose>, public ScriptWrappable {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
   static VRPose* create() { return new VRPose(); }
 
   DOMFloat32Array* orientation() const { return m_orientation; }
   DOMFloat32Array* position() const { return m_position; }
   DOMFloat32Array* angularVelocity() const { return m_angularVelocity; }
   DOMFloat32Array* linearVelocity() const { return m_linearVelocity; }
   DOMFloat32Array* angularAcceleration() const { return m_angularAcceleration; }
   DOMFloat32Array* linearAcceleration() const { return m_linearAcceleration; }
 
+  // TODO(klausw): expose timestamp and poseNum to JS? We have those in the

[bajones, 2016/10/04 06:33:57]

timestamp is exposed in the VRFrameData object. I don't think poseNum is a good
thing to surface to JS, because it's use is really just for tracking render
state internally and we don't want developers relying on something that opaque.

[klausw, 2016/10/04 06:47:04]

OK, I'll remove the comment. When you mentioned Oculus being interested, I
wasn't sure if you meant via JS or just internally in the WebVR implementation
itself.

Side note, I guess it would be possible to use timestamps as keys for a pose map
to avoid the need for separate pose numbers, but using doubles as keys seems
weird even if it should technically work.

[klausw, 2016/10/04 17:52:47]

Removed the comment.

+  // underlying VRPosePtr, and they could be useful to scripts. If yes,
+  // they would need to be added to VRPose in the WebVR spec.
+
   void setPose(const device::blink::VRPosePtr&);
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   VRPose();
 
   Member<DOMFloat32Array> m_orientation;
   Member<DOMFloat32Array> m_position;
   Member<DOMFloat32Array> m_angularVelocity;
   Member<DOMFloat32Array> m_linearVelocity;
   Member<DOMFloat32Array> m_angularAcceleration;
   Member<DOMFloat32Array> m_linearAcceleration;
 };
 
 }  // namespace blink
 
 #endif  // VRPose_h