Game closes with HMD Plugged in

Development Platform & Builds XR Development
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Hi everyone !

I have some trouble with my project when I try to use OpenXR.
For the context: I’ve exported some code we produced on a project which was running on UE4.23 and SteamVR and try to use it on UE4.27 with steam VR. Everything was fine until I try to run a build of the project: the controllers are not tracked and a window from SteamVR appears telling me that it needs keybinding for this project. I’ve read somewhere that new projects doesn’t works well with SteamVR, is that right ?

I tried with a project made from the VR template and everything works well, hands are tracked and no in game popup appears to ask for keybinding. So I chose to follow the settings of this project. I found out that this project doesn’t use the SteamVR plugin and use OpenXR instead. So I disabled the SteamVR plugin in my project.

The problem now is that the build closes almost instantly (it’s not crashing, it just closes itself). I dug into the engine to find out where the exit request is called and found the line, it’s from the OpenXRHMD.cpp file in the FOpenXRHMD::OnStartGameFrame(FWorldContext& WorldContext) method. It seems that the method catches an OpenXR event which is XR_TYPE_EVENT_DATA_INSTANCE_LOSS_PENDING which results in an exit request in build. I must have missed something but I don’t know what. The problem appears only if the headset is plugged in. Does someone have any idea ?

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Update !

I dug a bit more into the FOpenXRHMD::OnStartGameFrame() method with some breakpoint debug. I was wrong, it is a XR_SESSION_STATE_EXITING of a XR_TYPE_EVENT_DATA_SESSION_STATE_CHANGED that was tringerring the exit request (i didn’t see that the break at the end of the case was conditionnally called.

At some point the ReadNextEvent method gets XR_TYPE_EVENT_DATA_SESSION_STATE_CHANGED and its state is XR_SESSION_STATE_STOPPING which calls StopSession() which, I assume, raise state changed event with the XR_SESSION_STATE_EXITING state leading to the exit request

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Ok, it was just a blueprint command node to disable stereo mode without any checks on the conditions to disable it.