APITraitsFwd.h

Go to the documentation of this file.

// Copyright 2018-2019, Collabora, Ltd.
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief  Header with forward declarations/default specializations of functions
 * and traits defined/specialized by the generated file APITraitsImpl.h, which
 * includes this one.
 * @author Ryan Pavlik <ryan.pavlik@collabora.com>
 */

// IWYU pragma: private, include "xrtraits/APITraits.h"
// IWYU pragma: friend "APITraitsImpl\.h"

#pragma once

// Internal Includes
// - none

// Library Includes
#include <openxr/openxr.h>

// Standard Includes
#include <cstddef>

namespace xrtraits {
namespace traits {

#ifndef XRTRAITS_DOXYGEN
    namespace detail {
        /*! Declaration/default implementation of the actual trait
         * used by is_xr_tagged_type_v - specializations are generated.
         */
        template <typename T>
        constexpr bool is_xr_tagged_type_impl_v = false;

        /*! Is true for types that are XR tagged types and have a
         * defined enum value (type tag) for their type member, false
         * otherwise.
         *
         * Not all types with is_xr_tagged_type_v have their own type
         * tag: some (that primarily serve as "abstract" types, often
         * named `...BaseHeader`) do not but are intended primarily as
         * ways to pass references to concrete types that do have a
         * defined type tag.
         */
        template <typename T>
        constexpr bool has_xr_type_tag_impl_v = false;

        /*! For types that are XR tagged types and have a defined enum
         * value (type tag) for their type member, defines a
         * XrStructureType.
         *
         * Default value is nullptr in order to break if it shouldn't
         * be used with a given type.
         */
        template <typename T>
        constexpr std::nullptr_t xr_type_tag_impl_v = nullptr;

        /*! A string literal with the type name for all known XR
         * structure types.
         */
        template <typename T>
        constexpr std::nullptr_t xr_type_name_impl_v = nullptr;

        /*! A string literal with the type name for all XR types with
         * known tags.
         */
        template <XrStructureType Tag>
        constexpr std::nullptr_t xr_type_name_by_tag_impl_v = nullptr;

    } // namespace detail

#endif // !XRTRAITS_DOXYGEN

    /*! A struct template to wrap a type, to be able to pass it as
     * an argument.
     */
    template <typename T> struct TypeWrapper
    {
        //! The type that we're wrapping.
        using type = T;

        // Default constructor, constexpr to permit usage in constexpr
        // functions.
        constexpr TypeWrapper() = default;
    };

    /*! Calls your functor with a TypeWrapper<T> argument, where T is the
     * static type matching the enum value.
     *
     * If the enum value is not recognized, your functor will not be called.
     */
    template <typename F>
    constexpr void typeDispatch(XrStructureType t, F&& f);
} // namespace traits
} // namespace xrtraits