# Copyright 2013-2023 The Khronos Group Inc.
#
# SPDX-License-Identifier: Apache-2.0

# Relax NG schema for Khronos Vulkan API Registry XML
#
# See https://www.khronos.org/vulkan/
#
# This definition is subject to change (mostly in the form of additions)

namespace xsd = "http://www.w3.org/2001/XMLSchema-datatypes"

# Toplevel is a <registry> tag.
# May be led by an optional <comment> tag containing e.g. copyrights.
start = element registry {
    (
        element comment { text } ? |
        Platforms         * |
        Tags              * |
        Types             * |
        Enums             * |
        Commands          * |
        Feature           * |
        Extensions        * |
        Formats           * |
        Sync              * |
        SpirvExtensions   * |
        SpirvCapabilities *
    ) *
}

# <platforms> defines a group of platform names
Platforms = element platforms {
    Comment ? ,
    Platform *
}

# <platform> defines a single platform name.
#   name - string name of the platform, used as part of extension names
#   protect - preprocessor symbol to include platform headers from <vulkan.h>
#   comment - platform description
Platform = element platform {
    attribute name { text } ,
    attribute protect { text } ,
    Comment
}

# <tags> defines a group of author tags
Tags = element tags {
    Comment ? ,
    Tag *
}

# <tag> defines a single author tag.
#   name - name of the tag
#   author - name of the author (usually a company or project name)
#   contact - contact responsible for the tag (name and contact information)
Tag = element tag {
    attribute name { text } ,
    attribute author { text } ,
    attribute contact { text }
}

# <types> defines a group of types
Types = element types {
    Comment ? ,
    (
        Type |
        element comment { text }
    ) *
}

# <type> defines a single type. It is usually a C typedef but
# may contain arbitrary C code.
#   name - name of this type, if not present in the <name> tag
#   api - matches a <feature> api attribute, if present
#   alias - name of a type this type aliases
#   requires - name of another type definition required by this one
#   bitvalues - for a *Flags type, name of an enum definition that
#       defines the valid values for parameters of that type
#   name - name of the type being defined
#   category - if present, 'enum' indicates a matching <enums>
#       block to generate an enumerated type for, and 'struct'
#       causes special interpretation of the contents of the type
#       tag including ... TBD ...
#       Other allowed values are 'include', 'define', 'handle' and 'bitmask',
#       which do not change syntactic interpretation but allow organization
#       in the generated header.
#   deprecated - denotes that this type is deprecated, and why.
#       Valid values: 'aliased', 'true'.
#   parent - only applicable if category is 'handle'. Notes another type with
#       the 'handle' category that acts as a parent object for this type.
#   returnedonly - only applicable if category is 'struct'. Notes that this
#       struct is going to be filled in by the API, rather than an application
#       filling it out and passing it to the API.
#   structextends - only applicable if category is 'struct'. Lists parent
#       structures which this structure may extend via the pNext chain
#       of the parent.
#       When present it suppresses generation of automatic validity for the
#       pNext member of that structure, and instead the structure is added
#       to pNext chain validity for the parent structures it extends.
#   allowduplicate - only applicable if category is 'struct'. pNext can include
#       multiple structures of this type.
#   objtypeenum - name of VK_OBJECT_TYPE_* API enumerant which corresponds
#       to this type. Currently only specified for category="handle" types.
#   comment - descriptive text with no semantic meaning
# For types without a category, contents include
#   <apientry /> - substitutes for an APIENTRY-style macro on output
#   <name> - contains name of the type being defined
#   <type> - contains name of types used to define this type. There
#       may be multiple imbedded <type> tags
# For types with category 'enum', contents should be empty
# For types with category 'struct', contents should be one or more
#   <member> - like <param> for a struct or union member
#       len - if the member is an array, len may be one or more of the following
#           things, separated by commas (one for each array indirection):
#           another member of that struct, 'null-terminated' for a string,
#           '1' to indicate it is just a pointer (used for nested pointers),
#           or a latex equation (prefixed with 'latexmath:')
#       altlen - if len has latexmath equations, this contains equivalent C99
#                expressions separated by commas.
#       deprecated - denotes that this member is deprecated, and why.
#           Valid values: 'ignored', 'true'.
#       externsync - denotes that the member should be externally synchronized
#           when accessed by Vulkan
#       optional - whether this value can be omitted by providing NULL (for
#           pointers), VK_NULL_HANDLE (for handles) or 0 (for bitmasks/values)
#       selector - for a union member, identifies a separate enum member that
#           selects which of the union's members are valid
#       selection - for a member of a union, identifies an enum value indicating the member is valid
#       noautovalidity - tag stating that no automatic validity language should be generated
#       values - comma-separated list of legal values, usually used only for sType enums
#       limittype - only applicable for members of VkPhysicalDeviceProperties and
#           VkPhysicalDeviceProperties2, their substructures, and extensions.
#           Specifies the type of a device limit.
#           Valid values: 'min', 'max', 'pot', 'mul', 'bits', bitmask', 'range', 'struct', 'exact', 'noauto'
#       objecttype - only applicable for members representing a handle as
#           a uint64_t value. Specifies the name of another member which is
#           a VkObjectType or VkDebugReportObjectTypeEXT value specifying
#           the type of object the handle references.
#   <comment> - containing arbitrary text (unused)
#
# *** There is a problem here: I am not sure how to represent the <type>
# syntax where it may contain arbitrarily interleaved text, <type>, and
# <enum> child tags. This allows only the syntax
#   text <type>name</type> text <enum>name</enum> text
# where <type> and <enum> are both optional and occur in the specified
# order, which might eventually be a problem.
Type = element type {
    attribute api { text } ? ,
    attribute alias { text } ? ,
    attribute requires { text } ? ,
    attribute bitvalues { text } ? ,
    attribute name { TypeName } ? ,
    attribute category { text } ? ,
    attribute deprecated { text } ? ,
    attribute parent { TypeName } ? ,
    attribute returnedonly { text } ? ,
    attribute structextends { text } ? ,
    attribute allowduplicate { text } ? ,
    attribute objtypeenum { text } ? ,
    Comment ? ,
    (
        (
            ( text ,
              element type { text } *
            ) * ,
            element apientry { text } ? ,
            ( text ,
              element type { text } *
            ) * ,
            element name { TypeName } ? ,
            ( text ,
              element type { text } *
            ) *
        ) |
        (
            element member {
                attribute api { text } ? ,
                attribute len { text } ? ,
                attribute altlen { text } ? ,
                attribute externsync { text } ? ,
                attribute optional { text } ? ,
                attribute selector { text } ? ,
                attribute selection { EnumName } ? ,
                attribute noautovalidity { text } ? ,
                attribute values { text } ? ,
                attribute limittype { text } ? ,
                attribute objecttype { text } ? ,
                attribute deprecated { text } ? ,
                mixed {
                    element type { TypeName } ? ,
                    element name { text } ? ,
                    element enum { EnumName } ? ,
                    element comment { text } ?
                } +
            } |
            element comment { text }
        ) *
    )
}

# <enums> defines a group of enumerants
#   name - identifies a type name associated with this group. Should
#       match a <type> name to trigger generation of the type.
#   type - 'enum' or 'bitmask', if present
#   bitwidth - bit width of the enum value type.
#   comment - descriptive text with no semantic meaning
Enums = element enums {
    attribute name { text } ? ,
    attribute type { text } ? ,
    attribute bitwidth { Integer } ? ,
    Comment ? ,
    (
        Enum |
        Unused |
        element comment { text}
    ) *
}

# <enum> defines or references a single enumerant. There are two places it
# can be used: in an <enums> block, providing a global definition which
# may later be required by a feature or extension; or in a feature or
# extension, defining an enumerant specific to that feature. The second
# form has more possible attributes. Some combinations of attributes are
# nonsensical in on or the other place, but these are not detected by the
# validator.
#
# Ways to specify the enumerant value:
#   value - integer (including hex) value of the enumerant
#   bitpos - integer bit position of the enumerant in a bitmask
#   [extnumber], offset, [dir] - integer extension number specifying a
#       base block value (inherited from surrounding <extension> if
#       not specified); integer offset in that block; and direction
#       of offset ('-' for negative, positive if not specified).
#   alias - name of another enum this is an alias of
#
# value and bitpos allow, and extnumber/offset/dir require:
#   extends - type name of the enumerant being extended
#
# Other attributes:
#   api - matches a <feature> api attribute, if present
#   type - 'uint32_t', 'uint64_t', or 'float', if present. There are
#       certain conditions under which the tag must be present, or absent,
#       but they are context-dependent and difficult to express in the
#       RNC syntax.
#   name - enumerant name
#   alias - another enumerant this is semantically identical to
#   protect - additional #ifdef symbol to place around the enum
#   comment - descriptive text with no semantic meaning
#   deprecated - denotes that this enum is deprecated, and why.
#       Valid values: 'aliased', 'ignored', 'true'.
Enum = element enum {
    (
      (
        (
          attribute value { Integer } &
          attribute extends { TypeName } ?
        ) |
        (
          attribute bitpos { Integer } &
          attribute extends { TypeName } ?
        ) |
        (
          attribute extnumber { Integer } ? &
          attribute offset { Integer } &
          attribute dir { text } ? &
          attribute extends { TypeName }
        ) |
        (
          attribute extends { TypeName } ? &
          attribute alias { TypeName }
        )
      ) ? &
      attribute protect { text } ? &
      attribute api { text } ? &
      attribute type { TypeSuffix } ? &
      attribute name { text } &
      attribute deprecated { text } ? &
      Comment ?
    )
}

# <unused> defines a range of enumerants not currently being used
#   start, end - beginning and end of an unused numeric range
#   vendor - unused
#   comment - descriptive text with no semantic meaning
Unused = element unused {
    attribute start { Integer } ,
    attribute end { Integer } ? ,
    Vendor ? ,
    Comment ?
}

# <commands> defines a group of commands
Commands = element commands {
    Comment ? ,
    Command *
}

# <command> defines a single command
#
# There are two forms of the tag.
#
# Either form may have an 'api' attribute
#   api - matches a <feature> api attribute, if present
#
# The first form only has 'name' and 'alias' attributes, and no contents.
# It defines a command alias.
#
# The second form fully defines a command, and has the following structure:
# The possible attributes are not described in this comment block yet, but
# are in registry.html. The "prefix" and "suffix" attributes are currently
# present only in the OpenCL XML registry, where they are currently unused.
#
#   <proto> is the C function prototype, including the return type
#   <param> are function parameters, in order
#     len - if the member is an array, len may be one or more of the following
#           things, separated by commas (one for each array indirection):
#           another member of that struct, 'null-terminated' for a string,
#           '1' to indicate it is just a pointer (used for nested pointers),
#           or a latex equation (prefixed with 'latexmath:')
#     altlen - if len has latexmath equations, this contains equivalent C99
#              expressions separated by commas.
#     externsync - denotes that the member should be externally synchronized
#         when accessed by Vulkan
#     optional - whether this value can be omitted by providing NULL (for
#         pointers), VK_NULL_HANDLE (for handles) or 0 (for bitmasks/values)
#     selector - for a union parameter, identifies a separate enum parameter that
#         selects which of the union's members are valid
#     noautovalidity - tag stating that no automatic validity language should be
#         generated
#     objecttype - only applicable for parameters representing a handle as
#         a uint64_t value. Specifies the name of another parameter which is
#         a VkObjectType or VkDebugReportObjectTypeEXT value specifying
#         the type of object the handle references.
#     validstructs - only applicable for parameters which are pointers to
#         VkBaseInStructure or VkBaseOutStructure types, used as abstract
#         placeholders. Specifies a comma-separated list of structures which
#         may be passed in place of the parameter, or anywhere in the pNext
#         chain of the parameter.
#     stride - if the member is an array, stride specifies the name of
#         another member containing the byte stride between consecutive
#         elements in the array. Is assumed tightly packed if omitted.
#     <type> is a <type> name, if present
#     <name> is the function / parameter name, if present (normally should
#         be, except for void parameters).
# The textual contents of <proto> and <param> should be legal C
# for those parts of a function declaration.
#   <alias> - denotes function aliasing, if present
#     name - name of aliased function
#   <description> - unused text
#   <implicitexternsyncparams> are spec-language descriptions of
#       objects that are not parameters of the command, but
#       are related to them and also require external synchronization.
Command = element command {
    (   attribute name { text } ,
        attribute alias { text } ,
        attribute api { text } ?
        ) |
    (
        attribute tasks { text } ? ,
        attribute queues { text } ? ,
        attribute successcodes { text } ? ,
        attribute errorcodes { text } ? ,
        attribute renderpass { text } ? ,
        attribute videocoding { text } ? ,
        attribute cmdbufferlevel { text } ? ,
        attribute prefix { text } ? ,
        attribute suffix { text } ? ,
        attribute api { text } ? ,
        Comment ? ,
        element proto {
            mixed {
                element type { TypeName } ? ,
                element name { text }
            }
        } ,
        element param {
            attribute api { text } ? ,
            attribute len { text } ? ,
            attribute altlen { text } ? ,
            attribute externsync { text } ? ,
            attribute optional { text } ? ,
            attribute selector { text } ? ,
            attribute noautovalidity { text } ? ,
            attribute objecttype { text } ? ,
            attribute validstructs { text } ? ,
            attribute stride { text } ? ,
            mixed {
                element type { TypeName } ? ,
                element name { text } ?
            }
        } * ,
        (
            element alias {
                Name
            } ? &
            element description {
                text
            } ? &
            element implicitexternsyncparams {
                element param { text } *
            } ?
        )
    )
}

# Each <feature> defines the interface of an API version (e.g. OpenGL 1.2)
#   api - API tag (e.g. 'gl', 'gles2', etc. - used internally, not
#     necessarily an actual API name
#   name - version name (C preprocessor name, e.g. GL_VERSION_4_2)
#   number - version number, e.g. 4.2
#   protect - additional #ifdef symbol to place around the feature
#   sortorder - order relative to other features, default 0
#   <require> / <remove> contains features to require or remove in
#                        this version
#     profile - only require/remove when generated profile matches
#     comment - descriptive text with no semantic meaning
Feature = element feature {
    attribute api { text } ,
    Name ,
    attribute number { xsd:float } ,
    attribute protect { text } ? ,
    attribute sortorder { xsd:integer } ?,
    Comment ? ,
    (
        element require {
            ProfileName ? ,
            Depends ? ,
            Comment ? ,
            (
                InterfaceElement |
                element comment { text }
            ) *
        } |
        element remove {
            ProfileName ? ,
            Comment ? ,
            (
                InterfaceElement |
                element comment { text }
            ) *
        }
    ) *
}

Extensions = element extensions {
    Comment ? ,
    Extension *
}

# Each <extension> defines the interface of an API <extension>.
# Like a <feature> tag, but with slightly different attributes:
#   api - regexp pattern matching one or more API tags, indicating
#     which APIs the extension is known to work with. The only
#     syntax supported is <name>{|<name>}* and each name must
#     exactly match an API being generated (implicit ^$ surrounding).
#   name - extension name string
#   number - extension number (positive integer, should be unique)
#   sortorder - order relative to other extensions, default 0
#   protect - C preprocessor symbol to conditionally define the interface
#   platform - should be one of the platform names defined in the
#     <platform> tag. Currently unused.
#   author - name of the author (usually a company or project name)
#   contact - contact responsible for the tag (name and contact information)
#   type - 'device' or 'instance', if present
#   requires - commas-separated list of extension names required by this
#       extension
#   requiresCore - core version of Vulkan required by the extension, e.g.
#       "1.1". Defaults to "1.0".
#   supported - comma-separated list of API name(s) supporting this extension,
#       e.g. 'vulkan', or 'disabled' to never generate output.
#   ratified - comma-separated list of API name(s) for which this extension
#       has been ratified by Khronos. Defaults to "" if not specified.
#   promotedto - Vulkan version or a name of an extension that this
#       extension was promoted to; e.g. 'VK_VERSION_1_1', or
#       'VK_KHR_draw_indirect_county'
#   deprecatedby - Vulkan version or a name of an extension that deprecates
#       this extension. It may be empty string.
#       e.g. 'VK_VERSION_1_1', or 'VK_EXT_debug_utils', or ''
#   obsoletedby - Vulkan version or a name of an extension that obsoletes
#       this extension. It may be empty string.
#       e.g. 'VK_VERSION_1_1', or 'VK_EXT_debug_utils', or ''
#   provisional - 'true' if this extension is released provisionally
#   specialuse - contains one or more tokens separated by commas, indicating
#       a special purpose of the extension. Tokens may include 'cadsupport',
#       'd3demulation', 'devtools', 'debugging', and 'glemulation'. Others
#       may be added in the future.
# In addition, <require> / <remove> tags also support an api attribute:
#     api - only require/remove these features for the matching API.
#       Not a regular expression.
Extension = element extension {
    Name ,
    attribute number { Integer } ? ,
    attribute sortorder { xsd:integer } ?,
    attribute protect { text } ? ,
    attribute platform { text } ? ,
    attribute author { text } ? ,
    attribute contact { text } ? ,
    attribute type { text } ? ,
    attribute depends { text } ?,
    attribute supported { StringGroup } ? ,
    attribute ratified { text } ? ,
    attribute promotedto { text } ? ,
    attribute deprecatedby { text } ? ,
    attribute obsoletedby { text } ? ,
    attribute provisional { text } ? ,
    attribute specialuse { text } ? ,
    Comment ? ,
    (
        element require {
            attribute api { text } ? ,
            ProfileName ? ,
            Depends ? ,
            Comment ? ,
            (
                InterfaceElement |
                element comment { text }
            ) *
        } |
        element remove {
            attribute api { text } ? ,
            ProfileName ? ,
            Comment ? ,
            (
                InterfaceElement |
                element comment { text }
            ) *
        }
    ) *
}

# Each <format> define information about a VkFormat in a machine readable format
Formats = element formats {
    Format *
}

#    name - Format name, matching a VkFormat enum name
#    class - Used for 'Compatible Formats' table
#    blockSize - Used for 'Compatible Formats' table
#    texelsPerBlock - Used for 'Compatible Formats' table
#    blockExtent - 3D extent, no attribute is same as blockExtent=1,1,1
#    packed - number of bits data type
#    compressed - compression format class
#    planes - number of planes, no attribute is same as planes=1
#    chroma - can be one of [420, 422, 444] and used to mark if YCbCr Sampler are required by default
Format = element format {
    Name ,
    attribute class { text } ,
    attribute blockSize { text } ,
    attribute texelsPerBlock { text } ,
    attribute blockExtent { text } ? ,
    attribute packed { text } ? ,
    attribute compressed { text } ? ,
    attribute chroma { text } ? ,
    Component + ,
    Plane * ,
    SpirvImageFormat *
}

#   bits - size of component or "compressed" if part of block-compression format
#   numericFormat - as per Interpretation of Numeric Format table
#       some formats (depth/stencil) will have different numeric per component
#   planeIndex - For multi-planar formats to map to the plane element
Component = element component {
    Name ,
    attribute bits { text } ,
    attribute numericFormat { text },
    attribute planeIndex { text } ?
}

# For multi-planar formats
Plane = element plane {
    attribute index { text } ,
    attribute widthDivisor { text } ,
    attribute heightDivisor { text } ,
    attribute compatible { text }
}

# labels a SPIR-V Image Format
SpirvImageFormat = element spirvimageformat {
    Name
}

# <sync> is a set of all sync objects
Sync = element sync {
    Comment ? ,
    SyncStage *,
    SyncAccess *,
    SyncPipeline *
}

SyncSupport = element syncsupport {
    attribute queues { text } ? ,
    attribute stage { text } ?
}

SyncEquivalent = element syncequivalent {
    attribute stage { text } ?,
    attribute access { text } ?
}

# describes all Pipeline Stages
SyncStage = element syncstage {
    Name ,
    attribute alias { text } ? ,
    SyncSupport ? ,
    SyncEquivalent ?
}

# describes all Access Flags
SyncAccess = element syncaccess {
    element comment { text } ?,
    Name ,
    attribute alias { text } ? ,
    SyncSupport ? ,
    SyncEquivalent ?
}

SyncPipelineStage = element syncpipelinestage {
    attribute order { text } ? ,
    attribute before { text } ? ,
    attribute after { text } ?,
    text
}

# describes pipelines
SyncPipeline = element syncpipeline {
    Name ,
    attribute depends { text } ? ,
    SyncPipelineStage *
}

# Each <spirvextension> define a SPIR-V extension that can be used in the API.
# Each <spirvcapability> define a SPIR-V capability that can be used in the API.
# Contains information to both generate table in spec as well as validating
# what needs to be enabled or supported to be used in Vulkan
SpirvExtensions = element spirvextensions {
    Comment ? ,
    SpirvExtension *
}

SpirvExtension = element spirvextension {
    Name ,
    Enable +
}

SpirvCapabilities = element spirvcapabilities {
    Comment ? ,
    SpirvCapability *
}

SpirvCapability = element spirvcapability {
    Name ,
    Enable +
}

# <enable> defines a way to enable the parent element in the API.
# If anyone of the <enable> elements are valid then the parent element
# can be used.
#
# There are four forms of the tag.
#
# The first only has the minimal version of Vulkan of the application
#
# The second only has a single Vulkan extension that must be enabled
#
# The third has a single Vulkan feature with the struct where it is from
#
# The fourth has a property struct, the member field in it, and the value
# that must be present
#
# To make scripting easier, each <enable> has a require attribute to map
# to the asciidoctor conditional logic in the spec. For version and
# extension attribute variations, there is no need for the require attribute
# since it is a redundant 1:1 mapping.
#
# The 'alias' attribute is used in cases where the anchor link cannot be
# properly resolved and needs a manual name to link to
Enable = element enable {
    (
        attribute version { text } ) |
    (
        attribute extension { text } ) |
    (
        attribute struct { text },
        attribute feature { text },
        attribute requires { text },
        attribute alias { text } ? ) |
    (
        attribute property { text },
        attribute member { text },
        attribute value { text },
        attribute requires { text } ? )
}

# Contents of a <require> / <remove> tag, defining a group
# of features to require or remove.
#   <type> / <enum> / <command> all have attributes
#     name - feature name which must match
InterfaceElement =
    element type {
        Name ,
        Comment ?
    } |
    Enum |
    element command {
        Name ,
        Comment ?
    }

# Integers are allowed to be either decimal or C-hex (0x[0-9A-F]+), but
# XML Schema types do not seem to support hex notation, so we use this
# as a placeholder.
Integer = text

# EnumName is an compile-time constant name
EnumName = text

# TypeName is an argument/return value C type name
TypeName = text

# TypeSuffix is a C numeric type suffix, e.g. 'u' or 'ull'
TypeSuffix = text

# StringGroup is a regular expression with an implicit
#   '^(' and ')$' bracketing it.
StringGroup = text

# Repeatedly used attributes
ProfileName = attribute profile { text }
ExtensionName = attribute extension { text }
# Boolean expression of core version and extension names using (),+ operators
Depends = attribute depends { text }
Vendor = attribute vendor { text }
Comment = attribute comment { text }
Name = attribute name { text }