xrt_app_policy.h

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// Copyright 2026, Beyley Cardellio.
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief  Header for application policy object.
 * @author Beyley Cardellio <ep1cm1n10n123@gmail.com>
 * @ingroup xrt_iface
 */
 
#pragma once
 
#include "xrt/xrt_defines.h"
#include "xrt/xrt_limits.h"
 
 
#ifdef __cplusplus
extern "C" {
#endif
 
 
struct xrt_system;
struct xrt_app_system;
struct xrt_view_config;
 
/*!
 * @interface xrt_app_instance
 *
 * This interface acts as a way to store per-application policy for @ref xrt_instance.
 *
 * Only a single one of these should be created per application (aka XrInstance, in OpenXR terminology).
 *
 * @sa xrt_instance
 * @sa xrt_instance_create_app_instance
 */
struct xrt_app_instance
{
        /*!
         * @name Interface Methods
         *
         * All implementations of the xrt_app_instance interface must
         * populate all these function pointers with their implementation
         * methods. To use this interface, see the helper functions.
         * @{
         */
 
        /*!
         * Creates an application system from the passed system.
         *
         * All @ref xrt_app_system instances created by this function are expected to be destroyed before the
         * xrt_app_instance is destroyed.
         *
         * @note Code consuming this interface should use xrt_app_instance_create_app_system()
         *
         * @param      xainst    Pointer to self
         * @param      xsys      Pointer to system to wrap.
         * @param[out] out_xasys Return of application system, required.
         */
        xrt_result_t (*create_app_system)(struct xrt_app_instance *xainst,
                                          struct xrt_system *xsys,
                                          struct xrt_app_system **out_xasys);
 
        /*!
         * Destroy the application instance and its owned objects.
         *
         * Code consuming this interface should use xrt_app_instance_destroy().
         *
         * @param xainst Pointer to self
         */
        void (*destroy)(struct xrt_app_instance *xainst);
 
        /*!
         * @}
         */
};
 
/*!
 * @copydoc xrt_app_instance::create_app_system
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_app_instance
 */
XRT_NONNULL_ALL static inline xrt_result_t
xrt_app_instance_create_app_system(struct xrt_app_instance *xainst,
                                   struct xrt_system *xsys,
                                   struct xrt_app_system **out_xasys)
{
        return xainst->create_app_system(xainst, xsys, out_xasys);
}
 
/*!
 * @copydoc xrt_app_instance::destroy
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_app_instance
 */
XRT_NONNULL_ALL static inline void
xrt_app_instance_destroy(struct xrt_app_instance **xainst_ptr)
{
        struct xrt_app_instance *xainst = *xainst_ptr;
        if (xainst == NULL) {
                return;
        }
 
        xainst->destroy(xainst);
        *xainst_ptr = NULL;
}
 
 
struct xrt_recommended_view_config_view
{
        //! The width of the view.
        uint32_t width_pixels;
        //! The height of the view.
        uint32_t height_pixels;
        //! The amount of samples for the swapchain.
        uint32_t sample_count;
};
 
struct xrt_recommended_view_config
{
        //! Whether the recommendation is valid.
        bool valid;
        //! The number of views in the configuration, invariant.
        uint32_t view_count;
        //! The views in the configuration.
        struct xrt_recommended_view_config_view views[XRT_MAX_VIEWS];
};
 
/*!
 * @interface xrt_app_system
 *
 * This interface acts as a way to store per-application policy for @ref xrt_system.
 *
 * Only a single one of these should be created per @ref xrt_system per application
 * (aka per XrInstance, in OpenXR terminology).
 *
 * @sa xrt_app_instance_create_app_system
 */
struct xrt_app_system
{
        /*!
         * @name Interface Methods
         *
         * All implementations of the xrt_app_system interface must
         * populate all these function pointers with their implementation
         * methods. To use this interface, see the helper functions.
         * @{
         */
 
        /*!
         * Gets the recommended view configuration for the given view type, if available and supported.
         * Only the `recommended` field is guaranteed to be provided, and `max` may be left unspecified.
         *
         * This allows a policy to set a new recommended view configuration for the lifetime of this application.
         *
         * @param      xasys                       Pointer to self
         * @param      view_type                   The view type to get the recommended view configuration for.
         * @param[out] out_recommended_view_config The recommendation for the client.
         */
        xrt_result_t (*get_recommended_view_configuration)(
            struct xrt_app_system *xasys,
            enum xrt_view_type view_type,
            struct xrt_recommended_view_config *out_recommended_view_config);
 
        /*!
         * Sets the recommended view configuration for the given view type.
         * Only the `recommended` field will be meaningfully read by the xrt_app_system.
         *
         * The callee should push a session event of type @ref XRT_SESSION_EVENT_RECOMMENDED_VIEW_CONFIGURATION_CHANGE
         * when the recommended view configuration changes, so that sessions can react to this change if they want to.
         *
         * @note The xrt_app_system may not do verification on the passed configuration, it is up to the callee to not
         *       pass invalid data into here.
         *
         * @param     xasys                   Pointer to self
         * @param     view_type               The view type to set the recommended view configuration for.
         * @param[in] recommended_view_config The recommended view configuration to set for the given view type.
         */
        xrt_result_t (*set_recommended_view_configuration)(
            struct xrt_app_system *xasys,
            enum xrt_view_type view_type,
            const struct xrt_recommended_view_config *recommended_view_config);
 
        /*!
         * Destroy the application system and its owned objects.
         *
         * @note Code consuming this interface should use xrt_app_system_destroy().
         *
         * @param xasys Pointer to self
         */
        void (*destroy)(struct xrt_app_system *xasys);
 
        /*!
         * @}
         */
};
 
/*!
 * @copydoc xrt_app_system::get_recommended_view_configuration
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_app_system
 */
XRT_NONNULL_ALL static inline xrt_result_t
xrt_app_system_get_recommended_view_configuration(struct xrt_app_system *xasys,
                                                  enum xrt_view_type view_type,
                                                  struct xrt_recommended_view_config *out_recommended_view_config)
{
        return xasys->get_recommended_view_configuration(xasys, view_type, out_recommended_view_config);
}
 
/*!
 * @copydoc xrt_app_system::set_recommended_view_configuration
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_app_system
 */
XRT_NONNULL_ALL static inline xrt_result_t
xrt_app_system_set_recommended_view_configuration(struct xrt_app_system *xasys,
                                                  enum xrt_view_type view_type,
                                                  const struct xrt_recommended_view_config *recommended_view_config)
{
        return xasys->set_recommended_view_configuration(xasys, view_type, recommended_view_config);
}
 
/*!
 * @copydoc xrt_app_system::destroy
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_app_system
 */
XRT_NONNULL_ALL static inline void
xrt_app_system_destroy(struct xrt_app_system **xasys_ptr)
{
        struct xrt_app_system *xasys = *xasys_ptr;
        if (xasys == NULL) {
                return;
        }
 
        xasys->destroy(xasys);
        *xasys_ptr = NULL;
}
 
 
#ifdef __cplusplus
};
#endif