xrEnumerateViewConfigurations

xrEnumerateViewConfigurations and xrEnumerateViewConfigurationViews are functions in the OpenXR API used to discover rendering configurations and per-eye rendering requirements for a given XR system. They form part of the process for preparing the swapchain and view setup before rendering a scene.

xrEnumerateViewConfigurations reports the view configurations supported by a given system. Calling it requires an OpenXR instance and a system identifier. The function first returns the number of supported view configurations when the output array parameter is NULL. If a caller provides an array, the runtime fills it with XrViewConfigurationType values up to the reported count. Typical return codes include XR_SUCCESS on success, XR_ERROR_SIZE_INSUFFICIENT if the provided array is too small, and other standard error codes for invalid handles or states. The set of view configuration types is defined by the OpenXR specification and may include configurations such as primary stereo rendering.

xrEnumerateViewConfigurationViews queries per-view details for a chosen view configuration on a given system. After selecting a configuration type, the function can be invoked with a NULL array to obtain the number of views (usually two for stereoscopic setups). A subsequent call provides an array of XrViewConfigurationView structures describing per-eye rendering parameters, such as image rectangle dimensions and viewport or swapchain requirements. The returned information guides the allocation and sizing of swapchains and the setup of per-eye rendering targets.

Typical usage involves obtaining a system, enumerating available view configurations, choosing one, and then querying its per-view configuration to size swapchains and viewports accordingly. These functions help ensure rendering aligns with the capabilities of the hardware and the runtime, enabling correct stereo rendering and efficient resource management.