monado/doc/implementing-extensions.md

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# Implementing OpenXR extensions {#implementing-extension}
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Copyright 2021, Collabora, Ltd. and the Monado contributors
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Khronos often adds new functionality to the OpenXR specification as extensions.
The general steps to implement an OpenXR extension in Monado are as follows.
* Edit scripts/generate_oxr_ext_support.py. Usually you only need to add an
entry to the `EXTENSIONS` list at the top.
* Run the script `python scripts/generate_oxr_ext_support.py`.
* Format the regenerated file with
`clang-format -i src/xrt/state_trackers/oxr/oxr_extension_support.h`.
* Add entry points for each new function in
`src/xrt/state_trackers/oxr/oxr_api_negotiate.c`.
* Monado internal implementations of "objects" (think XrSession or
XrHandTracker) go into `src/xrt/state_trackers/oxr/oxr_objects.h`.
* Enums, defines and types go into `src/xrt/include/xrt/xrt_defines.h`. OpenXR
types are not used outside of the `oxr_api_*` files, instead equivalents with
the prefix `XRT_` are defined here.
* Add Monado specific prototypes for the new functions in
`src/xrt/state_trackers/oxr/oxr_objects.h`. The Monado implementations of
OpenXR functions are prefixed with `oxr_`.
* Implement the Monado specific functions in an appropriate source file
`src/state_trackers/oxr/oxr_api_*.c`. Trivial functions can be implemented
right there along with the usual parameter checks. More complex functions that
access more internal monado state should call functions implemented in the
relevant `oxr_*.c` file (without `_api_`).