I have a native app that adjusts the eye view matrix for doing additional turning on top of the view matrix I'm getting in VrAppInterface::::DrawEyeView. I properly set the ExternalVelocity matrix. It works fine, except for objects that I want to remain fixed in one spot (eg. the player's score, which is always at the same place on the screen). The fixed overlayed objects jump back and forth on the screen when the view is being adjusted, similarly to how the overall scene jumps back and forth if I don't set ExternalVelocity. I'm guessing TimeWarp is applying the same transformations to the overlayed fixed image as it does to the main scene. How do I avoid this?
In case anyone has the same problem, I fixed it by adding the VRAPI_FRAME_LAYER_FLAG_FIXED_TO_VIEW flag in ovrFrameLayer::Flags for the fixed layer, in DrawEyeView.