The open source OpenXR runtime
doc: Add documentation for implementing extensions
authored by
Christoph Haag
and committed by
Jakob Bornecrantz
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doc/implementing-extensions.md
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doc/implementing-extensions.md
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# Implementing OpenXR extensions {#implementing-extension}
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<!--
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Copyright 2021, Collabora, Ltd. and the Monado contributors
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SPDX-License-Identifier: BSL-1.0
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-->
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Khronos often adds new functionality to the OpenXR specification as extensions.
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The general steps to implement an OpenXR extension in Monado are as follows.
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* Edit scripts/generate_oxr_ext_support.py. Usually you only need to add an
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entry to the `EXTENSIONS` list at the top.
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* Run the script `python scripts/generate_oxr_ext_support.py`.
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* Format the regenerated file with
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`clang-format -i src/xrt/state_trackers/oxr/oxr_extension_support.h`.
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* Add entry points for each new function in
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`src/xrt/state_trackers/oxr/oxr_api_negotiate.c`.
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* Monado internal implementations of "objects" (think XrSession or
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XrHandTracker) go into `src/xrt/state_trackers/oxr/oxr_objects.h`.
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* Enums, defines and types go into `src/xrt/include/xrt/xrt_defines.h`. OpenXR
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types are not used outside of the `oxr_api_*` files, instead equivalents with
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the prefix `XRT_` are defined here.
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* Add Monado specific prototypes for the new functions in
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`src/xrt/state_trackers/oxr/oxr_objects.h`. The Monado implementations of
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OpenXR functions are prefixed with `oxr_`.
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* Implement the Monado specific functions in an appropriate source file
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`src/state_trackers/oxr/oxr_api_*.c`. Trivial functions can be implemented
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right there along with the usual parameter checks. More complex functions that
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access more internal monado state should call functions implemented in the
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relevant `oxr_*.c` file (without `_api_`).