xrt_system.h

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// Copyright 2020-2024, Collabora, Ltd.
// Copyright 2023, NVIDIA CORPORATION.
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief  Header for system objects.
 * @author Jakob Bornecrantz <jakob@collabora.com>
 * @author Korcan Hussein <korcan.hussein@collabora.com>
 * @ingroup xrt_iface
 */
 
#pragma once
 
#include "xrt/xrt_compiler.h"
#include "xrt/xrt_defines.h"
#include "xrt/xrt_device.h"
 
#include <stdalign.h>
 
#ifdef __cplusplus
extern "C" {
#endif
 
struct xrt_instance;
struct xrt_system_devices;
struct xrt_session;
struct xrt_compositor_native;
struct xrt_session_info;
 
 
/*
 *
 * System.
 *
 */
 
#define XRT_SYSTEM_ID 1
 
#define XRT_MAX_SYSTEM_NAME_SIZE 256
 
/*!
 * Properties provided by the system.
 */
struct xrt_system_properties
{
        uint32_t vendor_id;
        char name[XRT_MAX_SYSTEM_NAME_SIZE];
};
 
/*!
 * A system is a collection of devices, policies and optionally a compositor
 * that is organised into a chosive group that is usable by one user, most of
 * the functionality of a system is exposed through other objects, this is the
 * main object. It is from this you create sessions that is used to by apps to
 * interact with the "system".
 *
 * Sibling objects: @ref xrt_system_devices, @ref xrt_system_compositor and
 * @ref xrt_space_overseer.
 *
 * @ingroup xrt_iface
 */
struct xrt_system
{
        /*!
         * Create a @ref xrt_session and optionally a @ref xrt_compositor_native
         * for this system.
         *
         * param[in]  xsys    Pointer to self.
         * param[in]  xsi     Session info.
         * param[out] out_xs  Created session.
         * param[out] out_xcn Native compositor for this session, optional.
         */
        xrt_result_t (*create_session)(struct xrt_system *xsys,
                                       const struct xrt_session_info *xsi,
                                       struct xrt_session **out_xs,
                                       struct xrt_compositor_native **out_xcn);
 
        /*!
         * Destroy the system, must be destroyed after system devices and system
         * compositor has been destroyed.
         *
         * Code consuming this interface should use @ref xrt_system_destroy.
         *
         * @param xsys Pointer to self
         */
        void (*destroy)(struct xrt_system *xsys);
 
        struct xrt_system_properties properties;
};
 
/*!
 * @copydoc xrt_system::create_session
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_system
 */
static inline xrt_result_t
xrt_system_create_session(struct xrt_system *xsys,
                          const struct xrt_session_info *xsi,
                          struct xrt_session **out_xs,
                          struct xrt_compositor_native **out_xcn)
{
        return xsys->create_session(xsys, xsi, out_xs, out_xcn);
}
 
/*!
 * Destroy an xrt_system - helper function.
 *
 * @param[in,out] xsys_ptr A pointer to the xrt_system struct pointer.
 *
 * Will destroy the system if `*xsys_ptr` is not NULL. Will then set
 * `*xsys_ptr` to NULL.
 *
 * @public @memberof xrt_system
 */
static inline void
xrt_system_destroy(struct xrt_system **xsys_ptr)
{
        struct xrt_system *xsys = *xsys_ptr;
        if (xsys == NULL) {
                return;
        }
 
        *xsys_ptr = NULL;
        xsys->destroy(xsys);
}
 
 
/*
 *
 * System devices.
 *
 */
 
/*!
 * Maximum number of devices simultaneously usable by an implementation of
 * @ref xrt_system_devices
 *
 * @ingroup xrt_iface
 */
#define XRT_SYSTEM_MAX_DEVICES (32)
 
/*!
 * Data associating a device index (in @ref xrt_system_devices::xdevs) with a
 * given "role" for dynamic role switching.
 *
 * For each of the named roles, a negative value means unpopulated/not available.
 *
 * Populated by a call from the @ref xrt_system_devices interface.
 *
 * When the caller of @ref xrt_system_devices_get_roles sees a change (based on
 * comparing @ref generation_id) the caller must do the needed actions to handle
 * device changes. For example, for the OpenXR state tracker this may include
 * rebinding, queuing a change to the current interaction profile, and queuing
 * the events associated with such a change.
 *
 * @see xrt_system_devices
 * @ingroup xrt_iface
 */
struct xrt_system_roles
{
        /*!
         * Monotonically increasing generation counter for the association
         * between role and index.
         *
         * Increment whenever the roles are changed.
         *
         * All valid values are greater then zero; this is to
         * make init easier where any cache can start at zero and be guaranteed
         * to be replaced with a new @ref xrt_system_roles.
         *
         * alignas for 32 bit client support, see @ref ipc-design
         */
        alignas(8) uint64_t generation_id;
 
        /*!
         * Index in @ref xrt_system_devices::xdevs for the user's left
         * controller/hand, or negative if none available.
         */
        int32_t left;
 
        /*!
         * Index in @ref xrt_system_devices::xdevs for the user's right
         * controller/hand, or negative if none available.
         */
        int32_t right;
 
        /*!
         * Index in @ref xrt_system_devices::xdevs for the user's gamepad
         * device, or negative if none available.
         */
        int32_t gamepad;
 
        enum xrt_device_name left_profile;
 
        enum xrt_device_name right_profile;
 
        enum xrt_device_name gamepad_profile;
};
 
/*!
 * Guaranteed invalid constant for @ref xrt_system_roles, not using designated
 * initializers due to C++.
 *
 * @ingroup xrt_iface
 * @relates xrt_system_roles
 */
#define XRT_SYSTEM_ROLES_INIT                                                                                          \
        {                                                                                                              \
                0, -1, -1, -1, XRT_DEVICE_INVALID, XRT_DEVICE_INVALID, XRT_DEVICE_INVALID,                             \
        }
 
 
/*!
 * A collection of @ref xrt_device, and an interface for identifying the roles
 * they have been assigned.
 *
 * @see xrt_device, xrt_instance.
 */
struct xrt_system_devices
{
        /*!
         * All devices known in the system.
         *
         * This is conventionally considered the "owning" reference to the devices.
         * Valid entries are contiguous.
         */
        struct xrt_device *xdevs[XRT_SYSTEM_MAX_DEVICES];
 
        /*!
         * The number of elements in @ref xdevs that are valid.
         */
        size_t xdev_count;
 
        /*!
         * Observing pointers for devices in some static (unchangeable) roles.
         *
         * All pointers in this struct must also exist in @ref xdevs. The
         * association between a member of this struct and a given device
         * cannot change during runtime.
         */
        struct
        {
                /*!
                 * An observing pointer to the device serving as the "head"
                 * (and HMD).
                 *
                 * Required.
                 */
                struct xrt_device *head;
 
                /*!
                 * An observing pointer to the device providing eye tracking
                 * (optional).
                 */
                struct xrt_device *eyes;
 
                /*!
                 * An observing pointer to the device providing face tracking
                 * (optional).
                 */
                struct xrt_device *face;
 
                /*!
                 * An observing pointer to the device providing body tracking
                 * (optional).
                 */
                struct xrt_device *body;
 
                /*!
                 * Devices providing optical (or otherwise more directly
                 * measured than from controller estimation) hand tracking.
                 */
                struct
                {
 
                        /*!
                         * An observing pointer to the device providing hand
                         * tracking for the left hand (optional).
                         *
                         * Currently this is used for both optical and
                         * controller driven hand-tracking.
                         */
                        struct xrt_device *left;
 
                        /*!
                         * An observing pointer to the device providing hand
                         * tracking for the right hand (optional).
                         *
                         * Currently this is used for both optical and
                         * controller driven hand-tracking.
                         */
                        struct xrt_device *right;
                } hand_tracking;
        } static_roles;
 
 
        /*!
         * Function to get the dynamic input device roles from this system
         * devices, see @ref xrt_system_roles for more information.
         *
         * @param xsysd Pointer to self
         * @param[out] out_roles Pointer to xrt_system_roles
         */
        xrt_result_t (*get_roles)(struct xrt_system_devices *xsysd, struct xrt_system_roles *out_roles);
 
        /*!
         * Increment the usage count of a feature.
         * When the feature is used for the first time, then the feature will be begun.
         *
         * @param xsysd Pointer to self
         * @param type  Which feature is being counted.
         */
        xrt_result_t (*feature_inc)(struct xrt_system_devices *xsysd, enum xrt_device_feature_type type);
 
        /*!
         * Decrement the usage count of a feature.
         * When the feature is not used by the current application any more, then the feature will be ended.
         *
         * @param xsysd Pointer to self
         * @param type  Which feature is being counted.
         */
        xrt_result_t (*feature_dec)(struct xrt_system_devices *xsysd, enum xrt_device_feature_type type);
 
        /*!
         * Destroy all the devices that are owned by this system devices.
         *
         * Code consuming this interface should use @ref xrt_system_devices_destroy.
         *
         * @param xsysd Pointer to self
         */
        void (*destroy)(struct xrt_system_devices *xsysd);
};
 
/*!
 * @copydoc xrt_system_devices::get_roles
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_system_devices
 */
static inline xrt_result_t
xrt_system_devices_get_roles(struct xrt_system_devices *xsysd, struct xrt_system_roles *out_roles)
{
        return xsysd->get_roles(xsysd, out_roles);
}
 
/*!
 * @copydoc xrt_system_devices::feature_inc
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_system_devices
 */
static inline xrt_result_t
xrt_system_devices_feature_inc(struct xrt_system_devices *xsysd, enum xrt_device_feature_type type)
{
        return xsysd->feature_inc(xsysd, type);
}
 
/*!
 * @copydoc xrt_system_devices::feature_dec
 *
 * Helper for calling through the function pointer.
 *
 * @public @memberof xrt_system_devices
 */
static inline xrt_result_t
xrt_system_devices_feature_dec(struct xrt_system_devices *xsysd, enum xrt_device_feature_type type)
{
        return xsysd->feature_dec(xsysd, type);
}
 
/*!
 * Destroy an xrt_system_devices and owned devices - helper function.
 *
 * @param[in,out] xsysd_ptr A pointer to the xrt_system_devices struct pointer.
 *
 * Will destroy the system devices if `*xsysd_ptr` is not NULL. Will then set
 * `*xsysd_ptr` to NULL.
 *
 * @public @memberof xrt_system_devices
 */
static inline void
xrt_system_devices_destroy(struct xrt_system_devices **xsysd_ptr)
{
        struct xrt_system_devices *xsysd = *xsysd_ptr;
        if (xsysd == NULL) {
                return;
        }
 
        *xsysd_ptr = NULL;
        xsysd->destroy(xsysd);
}
 
 
#ifdef __cplusplus
}
#endif