The EXTX_overlay API layer has been abandoned for 3 years (it’s not even based on OpenXR 1.0), it can work with some hacks, but it’s very awkward. I forked it in the past and tried to make it work reliably, it’s real PITA, and not terribly efficient.
Instead I developed my own thing, even wrote a tutorial. It still has quite a few shortcomings.
I sort of given up on overlays as API layers, there are too many caveats. This feature truly must be implemented inside the OpenXR runtime to work reliably. So instead I’m just looking into integrating overlays into my OpenXR runtime (which is the one for Virtual Desktop, so that won’t work generically for all platforms).
It’s a huge gap that platforms vendors have created here, and I’m not seeing much interest in the past 3 years from anyone in the group to address it
EXTX_overlay is overkill for what 98% of people want to do IMO, we really need something focused on secondary app processes ability to submit quad/cylinder with a limited degree of interactability.
EXTX_overlay mandating full OpenXR core spec and extensions support is just a turn down to implement if you don’t have a proper multiclient compositor and tracking service. Narrowing down the scope would be much helpful.