I think that there’s a bug in the sample code on line 20 at
OpenXR / specs / 1.0/html/xrspec.html#XR_MSFT_holographic_window_attachment
XR_TYPE_ATTACHED_CORE_WINDOW_MSFT is not defined. I think it should be XR_TYPE_HOLOGRAPHIC_WINDOW_ATTACHMENT_MSFT
Incidentally, the “Topic checker” here wouldn’t let me write “XR_MSFT_holographic_window_attachment” – it looked “ambiguous”.