Proton/wineopenxr/make_openxr

#!/usr/bin/python3
# Wine Vulkan generator
#
# Copyright 2017-2018 Roderick Colenbrander
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
#  License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
#

import argparse
import logging
import os
import re
import sys
import urllib.request
import xml.etree.ElementTree as ET
from collections import OrderedDict
from collections.abc import Sequence
from enum import Enum

# This script generates code for a Wine Vulkan ICD driver from Vulkan's xr.xml.
# Generating the code is like 10x worse than OpenGL, which is mostly a calling
# convention passthrough.
#
# The script parses xr.xml and maps functions and types to helper objects. These
# helper objects simplify the xml parsing and map closely to the Vulkan types.
# The code generation utilizes the helper objects during code generation and
# most of the ugly work is carried out by these objects.
#
# Vulkan ICD challenges:
# - Vulkan ICD loader (vulkan-1.dll) relies on a section at the start of
#   'dispatchable handles' (e.g. XrDevice, XrInstance) for it to insert
#   its private data. It uses this area to stare its own dispatch tables
#   for loader internal use. This means any dispatchable objects need wrapping.
#
# - Vulkan structures have different alignment between win32 and 32-bit Linux.
#   This means structures with alignment differences need conversion logic.
#   Often structures are nested, so the parent structure may not need any
#   conversion, but some child may need some.
#
# xr.xml parsing challenges:
# - Contains type data for all platforms (generic Vulkan, Windows, Linux,..).
#   Parsing of extension information required to pull in types and functions
#   we really want to generate. Just tying all the data together is tricky.
#
# - Arrays are used all over the place for parameters or for structure members.
#   Array length is often stored in a previous parameter or another structure
#   member and thus needs careful parsing.

LOGGER = logging.Logger("openxr")
LOGGER.addHandler(logging.StreamHandler())

XR_XML_VERSION = "1.0.11"
WINE_XR_VERSION = (1, 1)

# Filenames to create.
WINE_OPENXR_H = "./wineopenxr.h"
WINE_OPENXR_DRIVER_H = "./wineopenxr_driver.h"
WINE_OPENXR_JSON = "./wineopenxr.json"
WINE_OPENXR_THUNKS_C = "./openxr_thunks.c"
WINE_OPENXR_THUNKS_H = "./openxr_thunks.h"

# Extension enum values start at a certain offset (EXT_BASE).
# Relative to the offset each extension has a block (EXT_BLOCK_SIZE)
# of values.
# Start for a given extension is:
# EXT_BASE + (extension_number-1) * EXT_BLOCK_SIZE
EXT_BASE = 1000000000
EXT_BLOCK_SIZE = 1000

UNSUPPORTED_EXTENSIONS = [
    # Instance extensions
    "XR_EXT_debug_report",
    # Handling of XR_EXT_debug_report requires some consideration. The win32
    # loader already provides it for us and it is somewhat usable. If we add
    # plumbing down to the native layer, we will get each message twice as we
    # use 2 loaders (win32+native), but we may get output from the driver.
    # In any case callback conversion is required.
    "XR_EXT_debug_utils",
    "XR_EXT_validation_features",
    "XR_EXT_validation_flags",
    "XR_KHR_display", # Needs WSI work.
    "XR_KHR_surface_protected_capabilities",
    "XR_KHR_loader_init",
    "XR_MSFT_perception_anchor_interop",

    # Device extensions
    "XR_AMD_display_native_hdr",
    "XR_EXT_display_control", # Requires XR_EXT_display_surface_counter
    "XR_EXT_full_screen_exclusive",
    "XR_EXT_hdr_metadata", # Needs WSI work.
    "XR_EXT_pipeline_creation_feedback",
    "XR_GOOGLE_display_timing",
    "XR_KHR_external_fence_win32",
    "XR_KHR_external_memory_win32",
    "XR_KHR_external_semaphore_win32",
    # Relates to external_semaphore and needs type conversions in bitflags.
    "XR_KHR_shared_presentable_image", # Needs WSI work.
    "XR_KHR_win32_keyed_mutex",

    # Extensions for other platforms
    "XR_EXT_external_memory_dma_buf",
    "XR_EXT_image_drm_format_modifier",
    "XR_KHR_external_fence_fd",
    "XR_KHR_external_memory_fd",
    "XR_KHR_external_semaphore_fd",

    # Deprecated extensions
    "XR_NV_external_memory_capabilities",
    "XR_NV_external_memory_win32",
]

ALLOWED_PROTECTS = [
        "XR_USE_PLATFORM_WIN32",
        "XR_USE_GRAPHICS_API_VULKAN",
        "XR_USE_GRAPHICS_API_OPENGL",
        "XR_USE_GRAPHICS_API_D3D11",
        "XR_USE_GRAPHICS_API_D3D12",
]

# Functions part of our wineopenxr graphics driver interface.
# DRIVER_VERSION should be bumped on any change to driver interface
# in FUNCTION_OVERRIDES
DRIVER_VERSION = 1

# Table of functions for which we have a special implementation.
# These are regular device / instance functions for which we need
# to do more work compared to a regular thunk or because they are
# part of the driver interface.
# - dispatch set whether we need a function pointer in the device
#   / instance dispatch table.
# - driver sets whether the API is part of the driver interface.
# - thunk sets whether to create a thunk in openxr_thunks.c.
FUNCTION_OVERRIDES = {
    # Global functions
    "xrCreateInstance" : {"dispatch" : False, "driver" : True, "thunk" : False},
    "xrCreateApiLayerInstance" : {"dispatch" : False, "driver" : True, "thunk" : False},
    "xrNegotiateLoaderRuntimeInterface" : {"dispatch" : False, "driver" : True, "thunk" : False},
    "xrNegotiateLoaderApiLayerInterface" : {"dispatch" : False, "driver" : False, "thunk" : False},
    "xrDestroyInstance" : {"dispatch" : False, "driver" : True, "thunk" : False},

    "xrCreateSession" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrDestroySession" : {"dispatch" : True, "driver" : True, "thunk" : False},

    "xrGetInstanceProcAddr" : {"dispatch" : False, "driver" : True, "thunk" : False},
    "xrEnumerateInstanceExtensionProperties" : {"dispatch" : False, "driver" : True, "thunk" : False},

    "xrConvertTimeToWin32PerformanceCounterKHR" : {"dispatch" : False, "driver" : True, "thunk" : False},
    "xrConvertWin32PerformanceCounterToTimeKHR" : {"dispatch" : False, "driver" : True, "thunk" : False},
    "xrGetD3D11GraphicsRequirementsKHR" : {"dispatch" : False, "driver" : True, "thunk" : False},
    "xrGetD3D12GraphicsRequirementsKHR" : {"dispatch" : False, "driver" : True, "thunk" : False},

    "xrGetVulkanGraphicsDeviceKHR" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrGetVulkanGraphicsDevice2KHR" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrGetVulkanDeviceExtensionsKHR" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrGetVulkanInstanceExtensionsKHR" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrCreateVulkanInstanceKHR" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrCreateVulkanDeviceKHR" : {"dispatch" : True, "driver" : True, "thunk" : False},

    "xrPollEvent" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrEnumerateSwapchainImages" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrGetSystem" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrEnumerateSwapchainFormats" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrCreateSwapchain" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrDestroySwapchain" : {"dispatch" : True, "driver" : True, "thunk" : False},
    "xrEndFrame" : {"dispatch" : True, "driver" : True, "thunk" : False},
}

NOT_OUR_FUNCTIONS = [
    # xr.xml defines that as a part of XR_LOADER_VERSION_1_0 commands but it looks like only layers should provide it
    # (through dll export).
    "xrNegotiateLoaderApiLayerInterface",
]

STRUCT_CHAIN_CONVERSIONS = [
    "XrInstanceCreateInfo",
]

STRUCTS_PUT_FIRST = [
    "XrUuid",
    "XrExtent3Df",
]

AUTO_MAPPED_HANDLES = [
    "XrSpace",
    "XrSpatialAnchorMSFT",
    "XrSpatialAnchorStoreConnectionMSFT",
    "XrHandTrackerEXT",
    "XrExportedLocalizationMapML",
    "XrMarkerDetectorML",
    "XrSceneMSFT",
    "XrSceneObserverMSFT",
    "XrSpatialGraphNodeBindingMSFT",
    "XrFoveationProfileFB",
    "XrTriangleMeshFB",
    "XrPassthroughFB",
    "XrPassthroughLayerFB",
    "XrGeometryInstanceFB",
    "XrEnvironmentDepthProviderMETA",
    "XrVirtualKeyboardMETA",
    "XrPlaneDetectorEXT",
    "XrEyeTrackerFB",
    "XrSpaceUserFB",
    "XrBodyTrackerFB",
    "XrFaceTrackerFB",
    "XrFaceTracker2FB",
    "XrEnvironmentDepthSwapchainMETA",
    "XrPassthroughHTC",
    "XrFacialTrackerHTC",
    "XrPassthroughColorLutMETA",
]

class Direction(Enum):
    """ Parameter direction: input, output, input_output. """
    INPUT = 1
    OUTPUT = 2
    INPUT_OUTPUT = 3


class XrBaseType(object):
    def __init__(self, name, _type, text, alias=None, requires=None):
        """ OpenXR base type class.

        XrBaseType is mostly used by OpenXR to define its own
        base types like XrFlags through typedef out of e.g. uint32_t.

        Args:
            name (:obj:'str'): Name of the base type.
            _type (:obj:'str'): Underlying type
            alias (bool): type is an alias or not.
            requires (:obj:'str', optional): Other types required.
                Often bitmask values pull in a *FlagBits type.
        """
        self.name = name
        self.type = _type
        self.alias = alias
        self.requires = requires
        self.required = False
        self.text = text

    def definition(self):
        # Definition is similar for alias or non-alias as type
        # is already set to alias.
        return self.text + "\n"

    def is_alias(self):
        return bool(self.alias)


class XrConstant(object):
    def __init__(self, name, value):
        self.name = name
        self.value = value

    def definition(self):
        text = "#define {0} {1}\n".format(self.name, self.value)
        return text


class XrDefine(object):
    def __init__(self, name, value):
        self.name = name
        self.value = value

    @staticmethod
    def from_xml(define):
        name_elem = define.find("name")

        if name_elem is None:
            # <type category="define" name="some_name">some_value</type>
            # At the time of writing there is only 1 define of this category
            # 'XR_DEFINE_NON_DISPATCHABLE_HANDLE'.
            name = define.attrib.get("name")

            # We override behavior of XR_DEFINE_NON_DISPATCHABLE handle as the default
            # definition various between 64-bit (uses pointers) and 32-bit (uses uint64_t).
            # This complicates TRACEs in the thunks, so just use uint64_t.
            if name == "XR_DEFINE_NON_DISPATCHABLE_HANDLE":
                value = "#define XR_DEFINE_NON_DISPATCHABLE_HANDLE(object) typedef uint64_t object;"
            else:
                value = define.text
            return XrDefine(name, value)

        # With a name element the structure is like:
        # <type category="define"><name>some_name</name>some_value</type>
        name = name_elem.text

        # Perform minimal parsing for constants, which we don't need, but are referenced
        # elsewhere in xr.xml.
        # - XR_API_VERSION is a messy, deprecated constant and we don't want generate code for it.
        # - AHardwareBuffer/ANativeWindow are forward declarations for Android types, which leaked
        #   into the define region.
        if name in ["XR_API_VERSION", "ANativeWindow"]:
            return XrDefine(name, None)

        # The body of the define is basically unstructured C code. It is not meant for easy parsing.
        # Some lines contain deprecated values or comments, which we try to filter out.
        value = ""
        for line in define.text.splitlines():
            value += "\n"
            # Skip comments or deprecated values.
            if "//" in line:
                continue
            value += line

        for child in define:
            value += child.text
            if child.tail is not None:
                # Split comments for XR_API_VERSION_1_0 / XR_API_VERSION_1_1
                if "//" in child.tail:
                    value += child.tail.split("//")[0]
                else:
                    value += child.tail

        return XrDefine(name, value.rstrip(' '))

    def definition(self):
        if self.value is None:
            return ""

        # Nothing to do as the value was already put in the right form during parsing.
        return "{0}\n".format(self.value)

    def is_alias(self):
        return False


class XrEnum(object):
    def __init__(self, name, values, alias=None):
        self.name = name
        self.values = values
        self.required = False
        self.alias = alias
        self.aliased_by = []

    @staticmethod
    def from_alias(enum, alias):
        name = enum.attrib.get("name")
        aliasee = XrEnum(name, alias.values, alias=alias)

        alias.add_aliased_by(aliasee)
        return aliasee

    @staticmethod
    def from_xml(enum):
        name = enum.attrib.get("name")
        values = []

        for v in enum.findall("enum"):
            # Value is either a value or a bitpos, only one can exist.
            value = v.attrib.get("value")
            alias_name = v.attrib.get("alias")
            if alias_name:
                alias = next(x for x in values if x.name == alias_name)
                values.append(XrEnumValue(v.attrib.get("name"), value=alias.value, hex=alias.hex))
            elif value:
                # Some values are in hex form. We want to preserve the hex representation
                # at least when we convert back to a string. Internally we want to use int.
                if "0x" in value:
                    values.append(XrEnumValue(v.attrib.get("name"), value=int(value, 0), hex=True))
                else:
                    values.append(XrEnumValue(v.attrib.get("name"), value=int(value, 0)))
            else:
                # bitmask
                value = 1 << int(v.attrib.get("bitpos"))
                values.append(XrEnumValue(v.attrib.get("name"), value=value, hex=True))

        # vulkan.h contains a *_MAX_ENUM value set to 32-bit at the time of writing,
        # which is to prepare for extensions as they can add values and hence affect
        # the size definition.
        max_name = re.sub(r'([0-9a-z_])([A-Z0-9])',r'\1_\2', name).upper() + "_MAX_ENUM"
        values.append(XrEnumValue(max_name, value=0x7fffffff, hex=True))

        return XrEnum(name, values)

    def add(self, value):
        """ Add a value to enum. """

        # Extensions can add new enum values. When an extension is promoted to Core
        # the registry defines the value twice once for old extension and once for
        # new Core features. Add the duplicate if it's explicitly marked as an
        # alias, otherwise ignore it.
        for v in self.values:
            if not value.is_alias() and v.value == value.value:
                LOGGER.debug("Adding duplicate enum value {0} to {1}".format(v, self.name))
                return
        # Avoid adding duplicate aliases multiple times
        if not any(x.name == value.name for x in self.values):
            self.values.append(value)

    def definition(self):
        if self.is_alias():
            return ""

        text = "typedef enum {0}\n{{\n".format(self.name)

        # Print values sorted, values can have been added in a random order.
        values = sorted(self.values, key=lambda value: value.value if value.value is not None else 0x7ffffffe)
        for value in values:
            text += "    {0},\n".format(value.definition())
        text += "}} {0};\n".format(self.name)

        for aliasee in self.aliased_by:
            text += "typedef {0} {1};\n".format(self.name, aliasee.name)

        text += "\n"
        return text

    def is_alias(self):
        return bool(self.alias)

    def add_aliased_by(self, aliasee):
        self.aliased_by.append(aliasee)


class XrEnumValue(object):
    def __init__(self, name, value=None, hex=False, alias=None):
        self.name = name
        self.value = value
        self.hex = hex
        self.alias = alias

    def __repr__(self):
        if self.is_alias():
            return "{0}={1}".format(self.name, self.alias)
        return "{0}={1}".format(self.name, self.value)

    def definition(self):
        """ Convert to text definition e.g. XR_FOO = 1 """
        if self.is_alias():
            return "{0} = {1}".format(self.name, self.alias)

        # Hex is commonly used for FlagBits and sometimes within
        # a non-FlagBits enum for a bitmask value as well.
        if self.hex:
            return "{0} = 0x{1:08x}".format(self.name, self.value)
        else:
            return "{0} = {1}".format(self.name, self.value)

    def is_alias(self):
        return self.alias is not None


class XrFunction(object):
    def __init__(self, _type=None, name=None, params=[], extensions=[], alias=None):
        self.extensions = []
        self.name = name
        self.type = _type
        self.params = params
        self.alias = alias

        # For some functions we need some extra metadata from FUNCTION_OVERRIDES.
        func_info = FUNCTION_OVERRIDES.get(self.name, None)
        self.dispatch = func_info["dispatch"] if func_info else True
        self.driver = func_info["driver"] if func_info else False
        self.thunk_needed = func_info["thunk"] if func_info else True
        self.private_thunk = func_info["private_thunk"] if func_info and "private_thunk" in func_info else False
        if self.private_thunk:
            self.thunk_needed = True

        # Required is set while parsing which APIs and types are required
        # and is used by the code generation.
        self.required = True if func_info else False

    @staticmethod
    def from_alias(command, alias):
        """ Create XrFunction from an alias command.

        Args:
            command: xml data for command
            alias (XrFunction): function to use as a base for types / parameters.

        Returns:
            XrFunction
        """
        func_name = command.attrib.get("name")
        func_type = alias.type
        params = alias.params

        return XrFunction(_type=func_type, name=func_name, params=params, alias=alias)

    @staticmethod
    def from_xml(command, types):
        proto = command.find("proto")
        func_name = proto.find("name").text
        func_type = proto.find("type").text

        params = []
        for param in command.findall("param"):
            xr_param = XrParam.from_xml(param, types)
            params.append(xr_param)

        return XrFunction(_type=func_type, name=func_name, params=params)

    def get_conversions(self):
        """ Get a list of conversion functions required for this function if any.
        Parameters which are structures may require conversion between win32
        and the host platform. This function returns a list of conversions
        required.
        """

        conversions = []
        for param in self.params:
            convs = param.get_conversions()
            if convs is not None:
                conversions.extend(convs)

        return conversions

    def is_alias(self):
        return bool(self.alias)

    def is_core_func(self):
        """ Returns whether the function is a core function.
        Core functions are APIs defined by the spec to be part of the
        Core API.
        """
        return not self.extensions

    def is_driver_func(self):
        """ Returns if function is part of Wine driver interface. """
        return self.driver

    def is_global_func(self):
        # Treat xrGetInstanceProcAddr as a global function as it
        # can operate with NULL for xrInstance.
        if self.name == "xrGetInstanceProcAddr":
            return True
        # Global functions are not passed a dispatchable object.
        elif self.params[0].is_dispatchable():
            return False
        return True

    def is_instance_func(self):
        # Instance functions are passed XrInstance.
        if self.params[0].type in ["XrInstance"]:
            return True
        return False

    def is_required(self):
        return self.required

    def needs_conversion(self):
        """ Check if the function needs any input/output type conversion.
        Functions need input/output conversion if struct parameters have
        alignment differences between Win32 and Linux 32-bit.
        """

        for p in self.params:
            if p.needs_conversion():
                LOGGER.debug("Parameter {0} to {1} requires conversion".format(p.name, self.name))
                return True

        return False

    def needs_dispatch(self):
        return self.dispatch

    def needs_thunk(self):
        return self.thunk_needed

    def needs_private_thunk(self):
        return self.private_thunk

    def pfn(self, prefix="p", call_conv=None, conv=False):
        """ Create function pointer. """

        if call_conv:
            pfn = "{0} ({1} *{2}_{3})(".format(self.type, call_conv, prefix, self.name)
        else:
            pfn = "{0} (*{1}_{2})(".format(self.type, prefix, self.name)

        for i, param in enumerate(self.params):
            if param.const:
                pfn += param.const + " "

            pfn += param.type
            if conv and param.needs_conversion():
                pfn += "_host"

            if param.is_pointer():
                pfn += " " + param.pointer

            if param.array_len is not None:
                pfn += "[{0}]".format(param.array_len)

            if i < len(self.params) - 1:
                pfn += ", "
        pfn += ")"
        return pfn

    def prototype(self, call_conv=None, prefix=None, postfix=None):
        """ Generate prototype for given function.

        Args:
            call_conv (str, optional): calling convention e.g. WINAPI
            prefix (str, optional): prefix to append prior to function name e.g. xrFoo -> wine_xrFoo
            postfix (str, optional): text to append after function name but prior to semicolon
        """

        proto = "{0}".format(self.type)

        if call_conv is not None:
            proto += " {0}".format(call_conv)

        if prefix is not None:
            proto += " {0}{1}(".format(prefix, self.name)
        else:
            proto += " {0}(".format(self.name)

        # Add all the parameters.
        proto += ", ".join([p.definition() for p in self.params])

        if postfix is not None:
            proto += ") {0}".format(postfix)
        else:
            proto += ")"

        return proto

    def body(self):
        body = ""

        if self.type != "void":
            body += "    {0} ret;\n\n".format(self.type)
        if not self.needs_private_thunk():
            body += "    {0}".format(self.trace())

        params = ", ".join([p.variable(conv=False) for p in self.params])

        # Call the native Vulkan function.
        if self.is_core_func():
            # core functions are exported by the native loader, so avoid dispatch for those
            if self.type == "void":
                body += "    {0}({1});\n".format(self.name, params)
            else:
                body += "    ret = {0}({1});\n".format(self.name, params)
        else:
            if self.type == "void":
                body += "    {0}.p_{1}({2});\n".format(self.params[0].dispatch_table(), self.name, params)
            else:
                body += "    ret = {0}.p_{1}({2});\n".format(self.params[0].dispatch_table(), self.name, params)

        if "Destroy" in self.name:
            for p in self.params:
                if p.type in AUTO_MAPPED_HANDLES:
                    body += "    unregister_dispatchable_handle((uint64_t){0});\n".format(p.name)
        if "Create" in self.name:
            for p in self.params:
                if p.type in AUTO_MAPPED_HANDLES and p.is_pointer():
                    body += "    if (!ret) register_dispatchable_handle((uint64_t)*{0}, &({1}));\n".format(p.name, self.params[0].dispatch_table())
        if self.type != "void":
            body += "    return ret;\n"
        return body

    def body_conversion(self):
        body = ""

        # Declare a variable to hold the result for non-void functions.
        if self.type != "void":
            body += "    {0} result;\n".format(self.type)

        # Declare any tmp parameters for conversion.
        for p in self.params:
            if not p.needs_conversion():
                continue

            if p.is_dynamic_array():
                body += "    {0}_host *{1}_host;\n".format(p.type, p.name)
            else:
                body += "    {0}_host {1}_host;\n".format(p.type, p.name)

        if not self.needs_private_thunk():
            body += "    {0}\n".format(self.trace())

        # Call any win_to_host conversion calls.
        for p in self.params:
            if not p.needs_input_conversion():
                continue

            body += p.copy(Direction.INPUT)

        # Build list of parameters containing converted and non-converted parameters.
        # The param itself knows if conversion is needed and applies it when we set conv=True.
        params = ", ".join([p.variable(conv=True) for p in self.params])

        # Call the native function.
        if self.type == "void":
            body += "    {0}.p_{1}({2});\n".format(self.params[0].dispatch_table(), self.name, params)
        else:
            body += "    result = {0}.p_{1}({2});\n".format(self.params[0].dispatch_table(), self.name, params)

        body += "\n"

        # Call any host_to_win conversion calls.
        for p in self.params:
            if not p.needs_output_conversion():
                continue

            body += p.copy(Direction.OUTPUT)

        # Perform any required cleanups. Most of these are for array functions.
        for p in self.params:
            if not p.needs_free():
                continue

            body += p.free()

        # Finally return the result.
        if self.type != "void":
            body += "    return result;\n"

        return body

    def stub(self, call_conv=None, prefix=None):
        stub = self.prototype(call_conv=call_conv, prefix=prefix)
        stub += "\n{\n"
        stub += "    {0}".format(self.trace(message="stub: ", trace_func="WINE_FIXME"))

        if self.type == "XrResult":
            stub += "    return XR_ERROR_OUT_OF_HOST_MEMORY;\n"
        elif self.type == "XrBool32":
            stub += "    return XR_FALSE;\n"
        elif self.type == "PFN_xrVoidFunction":
            stub += "    return NULL;\n"

        stub += "}\n\n"
        return stub

    def thunk(self, call_conv=None, prefix=None):
        thunk = self.prototype(call_conv=call_conv, prefix=prefix)
        thunk += "\n{\n"

        if self.needs_conversion():
            thunk += "#if defined(USE_STRUCT_CONVERSION)\n"
            thunk += self.body_conversion()
            thunk += "#else\n"
            thunk += self.body()
            thunk += "#endif\n"
        else:
            thunk += self.body()

        thunk += "}\n\n"
        return thunk

    def trace(self, message=None, trace_func=None):
        """ Create a trace string including all parameters.

        Args:
            message (str, optional): text to print at start of trace message e.g. 'stub: '
            trace_func (str, optional): used to override trace function e.g. FIXME, printf, etcetera.
        """
        if trace_func is not None:
            trace = "{0}(\"".format(trace_func)
        else:
            trace = "WINE_TRACE(\""

        if message is not None:
            trace += message

        # First loop is for all the format strings.
        trace += ", ".join([p.format_string() for p in self.params])
        trace += "\\n\""

        # Second loop for parameter names and optional conversions.
        for param in self.params:
            if param.format_conv is not None:
                trace += ", " + param.format_conv.format(param.name)
            else:
                trace += ", {0}".format(param.name)
        trace += ");\n"

        return trace


class XrFunctionPointer(object):
    def __init__(self, _type, name, members, params_text):
        self.name = name
        self.members = members
        self.type = _type
        self.required = False
        self.params_text = params_text

    @staticmethod
    def from_xml(funcpointer):
        members = []
        begin = None

        for t in funcpointer.findall("type"):
            # General form:
            # <type>void</type>*       pUserData,
            # Parsing of the tail (anything past </type>) is tricky since there
            # can be other data on the next line like: const <type>int</type>..

            const = True if begin and "const" in begin else False
            _type = t.text
            lines = t.tail.split(",\n")
            if lines[0][0] == "*":
                pointer = "*"
                name = lines[0][1:].strip()
            else:
                pointer = None
                name = lines[0].strip()

            # Filter out ); if it is contained.
            name = name.partition(");")[0]

            # If tail encompasses multiple lines, assign the second line to begin
            # for the next line.
            try:
                begin = lines[1].strip()
            except IndexError:
                begin = None

            members.append(XrMember(const=const, _type=_type, pointer=pointer, name=name))

        _type = funcpointer.text
        name = funcpointer.find("name").text
        params_text = None
        if members == []:
            index = 0
            for elem_part in funcpointer.itertext():
                index = index + 1
                if index == 3:
                    p = re.findall(r'\([^)]*\)', elem_part)
                    params_text = next(iter(p), None)
                    if params_text:
                        params_text = params_text[1:-1]
                    break

        return XrFunctionPointer(_type, name, members, params_text)

    def definition(self):
        text = "{0} {1})(\n".format(self.type, self.name)

        first = True
        if len(self.members) > 0:
            for m in self.members:
                if first:
                    text += "    " + m.definition()
                    first = False
                else:
                    text += ",\n    " + m.definition()
        elif self.params_text is not None:
            text += self.params_text
        else:
            # Just make the compiler happy by adding a void parameter.
            text += "void"
        text += ");\n"
        return text


class XrHandle(object):
    def __init__(self, name, _type, parent, alias=None):
        self.name = name
        self.type = _type
        self.parent = parent
        self.alias = alias
        self.required = False

    @staticmethod
    def from_alias(handle, alias):
        name = handle.attrib.get("name")
        return XrHandle(name, alias.type, alias.parent, alias=alias)

    @staticmethod
    def from_xml(handle):
        name = handle.find("name").text
        _type = handle.find("type").text
        parent = handle.attrib.get("parent")
        return XrHandle(name, _type, parent)

    def dispatch_table(self):
        if not self.is_dispatchable():
            return None

        if self.parent is None:
            # Should only happen for XrInstance
            return "funcs"
        if self.parent in ["XrInstance"]:
            return "wine_instance->funcs"
        if self.parent in ["XrSession"]:
            return "wine_session->wine_instance->funcs"
        if self.parent in ["XrActionSet"]:
            return "wine_action_set->wine_instance->funcs"

        LOGGER.error("Unhandled dispatchable parent: {0}".format(self.parent))

    def definition(self):
        """ Generates handle definition e.g. XR_DEFINE_HANDLE(xrInstance) """

        # Legacy types are typedef'ed to the new type if they are aliases.
        if self.is_alias():
            return "typedef {0} {1};\n".format(self.alias.name, self.name)

        return "{0}({1})\n".format(self.type, self.name)

    def is_alias(self):
        return self.alias is not None

    def is_dispatchable(self):
        """ Some handles, like XrInstance, are dispatchable objects,
        which means they contain a dispatch table of function pointers.
        """
        return self.type == "XR_DEFINE_HANDLE"

    def is_required(self):
        return self.required

    def native_handle(self, name):
        """ Provide access to the native handle of a wrapped object. """

        # Remember to add any new native handle whose parent is XrDevice
        # to unwrap_object_handle() in openxr.c
        if self.name == "XrCommandPool":
            return "wine_cmd_pool_from_handle({0})->command_pool".format(name)

        native_handle_name = None

        if self.name in AUTO_MAPPED_HANDLES:
            return None

        if self.name == "XrInstance":
            native_handle_name = "instance"
        if self.name == "XrSession":
            native_handle_name = "session"
        if self.name == "XrSwapchain":
            native_handle_name = "swapchain"
        if self.name == "XrActionSet":
            return None
        if self.name == "XrAction":
            return None

        if native_handle_name:
            return "((wine_{0} *){1})->{2}".format(self.name, name, native_handle_name)

        if self.is_dispatchable():
            LOGGER.error("Unhandled native handle for: {0}".format(self.name))
        return None


class XrMember(object):
    def __init__(self, const=False, struct_fwd_decl=False,_type=None, pointer=None, name=None, array_len=None,
            dyn_array_len=None, optional=False, values=None):
        self.const = const
        self.struct_fwd_decl = struct_fwd_decl
        self.name = name
        self.pointer = pointer
        self.type = _type
        self.type_info = None
        self.array_len = array_len
        self.dyn_array_len = dyn_array_len
        self.optional = optional
        self.values = values

    def __eq__(self, other):
        """ Compare member based on name against a string.

        This method is for convenience by XrStruct, which holds a number of members and needs quick checking
        if certain members exist.
        """

        return self.name == other

    def __repr__(self):
        return "{0} {1} {2} {3} {4} {5} {6}".format(self.const, self.struct_fwd_decl, self.type, self.pointer,
                self.name, self.array_len, self.dyn_array_len)

    @staticmethod
    def from_xml(member):
        """ Helper function for parsing a member tag within a struct or union. """

        name_elem = member.find("name")
        type_elem = member.find("type")

        const = False
        struct_fwd_decl = False
        member_type = None
        pointer = None
        array_len = None

        values = member.get("values")

        if member.text:
            if "const" in member.text:
                const = True

            # Some members contain forward declarations:
            # - XrBaseInstructure has a member "const struct XrBaseInStructure *next"
            # - XrWaylandSurfaceCreateInfoKHR has a member "struct wl_display *display"
            if "struct" in member.text:
                struct_fwd_decl = True

        if type_elem is not None:
            member_type = type_elem.text
            if type_elem.tail is not None:
                pointer = type_elem.tail.strip() if type_elem.tail.strip() != "" else None

        # Name of other member within, which stores the number of
        # elements pointed to be by this member.
        dyn_array_len = member.get("len")

        # Some members are optional, which is important for conversion code e.g. not dereference NULL pointer.
        optional = True if member.get("optional") else False

        # Usually we need to allocate memory for dynamic arrays. We need to do the same in a few other cases
        # like for XrCommandBufferBeginInfo.pInheritanceInfo. Just threat such cases as dynamic arrays of
        # size 1 to simplify code generation.
        if dyn_array_len is None and pointer is not None:
            dyn_array_len = 1

        # Some members are arrays, attempt to parse these. Formats include:
        # <member><type>char</type><name>extensionName</name>[<enum>XR_MAX_EXTENSION_NAME_SIZE</enum>]</member>
        # <member><type>uint32_t</type><name>foo</name>[4]</member>
        if name_elem.tail and name_elem.tail[0] == '[':
            LOGGER.debug("Found array type")
            enum_elem = member.find("enum")
            if enum_elem is not None:
                array_len = enum_elem.text
            else:
                # Remove brackets around length
                array_len = name_elem.tail.strip("[]")

        return XrMember(const=const, struct_fwd_decl=struct_fwd_decl, _type=member_type, pointer=pointer, name=name_elem.text,
                array_len=array_len, dyn_array_len=dyn_array_len, optional=optional, values=values)

    def copy(self, input, output, direction):
        """ Helper method for use by conversion logic to generate a C-code statement to copy this member. """

        if self.needs_conversion():
            if self.is_dynamic_array():
                if direction == Direction.OUTPUT:
                    LOGGER.warn("TODO: implement copying of returnedonly dynamic array for {0}.{1}".format(self.type, self.name))
                else:
                    # Array length is either a variable name (string) or an int.
                    count = self.dyn_array_len if isinstance(self.dyn_array_len, int) else "{0}{1}".format(input, self.dyn_array_len)
                    return "{0}{1} = convert_{2}_array_win_to_host({3}{1}, {4});\n".format(output, self.name, self.type, input, count)
            elif self.is_static_array():
                count = self.array_len
                if direction == Direction.OUTPUT:
                    # Needed by XrMemoryHeap.memoryHeaps
                    return "convert_{0}_static_array_host_to_win({2}{1}, {3}{1}, {4});\n".format(self.type, self.name, input, output, count)
                else:
                    # Nothing needed this yet.
                    LOGGER.warn("TODO: implement copying of static array for {0}.{1}".format(self.type, self.name))
            else:
                if direction == Direction.OUTPUT:
                    return "convert_{0}_host_to_win(&{2}{1}, &{3}{1});\n".format(self.type, self.name, input, output)
                else:
                    return "convert_{0}_win_to_host(&{2}{1}, &{3}{1});\n".format(self.type, self.name, input, output)
        elif self.is_static_array():
            bytes_count = "{0} * sizeof({1})".format(self.array_len, self.type)
            return "memcpy({0}{1}, {2}{1}, {3});\n".format(output, self.name, input, bytes_count)
        else:
            return "{0}{1} = {2}{1};\n".format(output, self.name, input)

    def definition(self, align=False, conv=False):
        """ Generate prototype for given function.

        Args:
            align (bool, optional): Enable alignment if a type needs it. This adds WINE_XR_ALIGN(8) to a member.
            conv (bool, optional): Enable conversion if a type needs it. This appends '_host' to the name.
        """

        text = ""
        if self.is_const():
            text += "const "

        if self.is_struct_forward_declaration():
            text += "struct "

        if conv and self.is_struct():
            text += "{0}_host".format(self.type)
        else:
            text += self.type

        if self.is_pointer():
            text += " {0}{1}".format(self.pointer, self.name)
        else:
            if align and self.needs_alignment():
                text += " WINE_XR_ALIGN(8) " + self.name
            else:
                text += " " + self.name

        if self.is_static_array():
            text += "[{0}]".format(self.array_len)

        return text

    def get_conversions(self):
        """ Return any conversion description for this member and its children when conversion is needed. """

        # Check if we need conversion either for this member itself or for any child members
        # in case member represents a struct.
        if not self.needs_conversion():
            return None

        conversions = []

        # Collect any conversion for any member structs.
        struct = self.type_info["data"]
        for m in struct:
            m.needs_struct_extensions_conversion()
            if m.needs_conversion():
                conversions.extend(m.get_conversions())

        struct.needs_struct_extensions_conversion()

        struct = self.type_info["data"]
        direction = Direction.OUTPUT if struct.returnedonly else Direction.INPUT
        if self.is_dynamic_array():
            conversions.append(ConversionFunction(False, True, direction, struct))
        elif self.is_static_array():
            conversions.append(ConversionFunction(True, False, direction, struct))
        else:
            conversions.append(ConversionFunction(False, False, direction, struct))

        if self.needs_free():
            conversions.append(FreeFunction(self.is_dynamic_array(), struct))

        return conversions

    def is_const(self):
        return self.const

    def is_dynamic_array(self):
        """ Returns if the member is an array element.
        OpenXR uses this for dynamically sized arrays for which
        there is a 'count' parameter.
        """
        return self.dyn_array_len is not None

    def is_handle(self):
        return self.type_info["category"] == "handle"

    def is_pointer(self):
        return self.pointer is not None

    def is_static_array(self):
        """ Returns if the member is an array.
        OpenXR uses this often for fixed size arrays in which the
        length is part of the member.
        """
        return self.array_len is not None

    def is_struct(self):
        return self.type_info["category"] == "struct"

    def is_struct_forward_declaration(self):
        return self.struct_fwd_decl

    def is_union(self):
        return self.type_info["category"] == "union"

    def needs_alignment(self):
        """ Check if this member needs alignment for 64-bit data.
        Various structures need alignment on 64-bit variables due
        to compiler differences on 32-bit between Win32 and Linux.
        """

        if self.is_pointer():
            return False
        elif self.type == "size_t":
            return False
        elif self.type in ["uint64_t"]:
            return True
        elif self.is_struct():
            struct = self.type_info["data"]
            return struct.needs_alignment()
        elif self.is_handle():
            # Dispatchable handles are pointers to objects, while
            # non-dispatchable are uint64_t and hence need alignment.
            handle = self.type_info["data"]
            return False if handle.is_dispatchable() else True
        return False

    def needs_conversion(self):
        """ Structures requiring alignment, need conversion between win32 and host. """

        if not self.is_struct():
            return False

        struct = self.type_info["data"]
        return struct.needs_conversion()

    def needs_free(self):
        if not self.needs_conversion():
            return False

        if self.is_dynamic_array():
            return True

        # TODO: some non-pointer structs and optional pointer structs may need freeing,
        # though none of this type have been encountered yet.
        return False

    def needs_struct_extensions_conversion(self):
        if not self.is_struct():
            return False

        struct = self.type_info["data"]
        return struct.needs_struct_extensions_conversion()

    def set_type_info(self, type_info):
        """ Helper function to set type information from the type registry.
        This is needed, because not all type data is available at time of
        parsing.
        """
        self.type_info = type_info


class XrParam(object):
    """ Helper class which describes a parameter to a function call. """

    def __init__(self, type_info, const=None, pointer=None, name=None, array_len=None, dyn_array_len=None):
        self.const = const
        self.name = name
        self.array_len = array_len
        self.dyn_array_len = dyn_array_len
        self.pointer = pointer
        self.type_info = type_info
        self.type = type_info["name"] # For convenience
        self.handle = type_info["data"] if type_info["category"] == "handle" else None
        self.struct = type_info["data"] if type_info["category"] == "struct" else None

        self._set_direction()
        self._set_format_string()
        self._set_conversions()

    def __repr__(self):
        return "{0} {1} {2} {3} {4} {5}".format(self.const, self.type, self.pointer, self.name, self.array_len, self.dyn_array_len)

    @staticmethod
    def from_xml(param, types):
        """ Helper function to create XrParam from xml. """

        # Parameter parsing is slightly tricky. All the data is contained within
        # a param tag, but some data is within subtags while others are text
        # before or after the type tag.
        # Common structure:
        # <param>const <type>char</type>* <name>pLayerName</name></param>

        name_elem = param.find("name")
        array_len = None
        name = name_elem.text
        # Tail contains array length e.g. for blendConstants param of xrSetBlendConstants
        if name_elem.tail is not None:
            array_len = name_elem.tail.strip("[]")

        # Name of other parameter in function prototype, which stores the number of
        # elements pointed to be by this parameter.
        dyn_array_len = param.get("len", None)

        const = param.text.strip() if param.text else None
        type_elem = param.find("type")
        pointer = type_elem.tail.strip() if type_elem.tail.strip() != "" else None

        # Since we have parsed all types before hand, this should not happen.
        type_info = types.get(type_elem.text, None)
        if type_info is None:
            LOGGER.err("type info not found for: {0}".format(type_elem.text))

        return XrParam(type_info, const=const, pointer=pointer, name=name, array_len=array_len, dyn_array_len=dyn_array_len)

    def _set_conversions(self):
        """ Internal helper function to configure any needed conversion functions. """

        self.free_func = None
        self.input_conv = None
        self.output_conv = None
        if not self.needs_conversion():
            return

        # Input functions require win to host conversion.
        if self._direction in [Direction.INPUT, Direction.INPUT_OUTPUT]:
            self.input_conv = ConversionFunction(False, self.is_dynamic_array(), Direction.INPUT, self.struct)

        # Output functions require host to win conversion.
        if self._direction in [Direction.INPUT_OUTPUT, Direction.OUTPUT]:
            self.output_conv = ConversionFunction(False, self.is_dynamic_array(), Direction.OUTPUT, self.struct)

        # Dynamic arrays, but also some normal structs (e.g. XrCommandBufferBeginInfo) need memory
        # allocation and thus some cleanup.
        if self.is_dynamic_array() or self.struct.needs_free():
            self.free_func = FreeFunction(self.is_dynamic_array(), self.struct)

    def _set_direction(self):
        """ Internal helper function to set parameter direction (input/output/input_output). """

        # The parameter direction needs to be determined from hints in xr.xml like returnedonly,
        # parameter constness and other heuristics.
        # For now we need to get this right for structures as we need to convert these, we may have
        # missed a few other edge cases (e.g. count variables).
        # See also https://github.com/KhronosGroup/Vulkan-Docs/issues/610

        if not self.is_pointer():
            self._direction = Direction.INPUT
        elif self.is_const() and self.is_pointer():
            self._direction = Direction.INPUT
        elif self.is_struct():
            if not self.struct.returnedonly:
                self._direction = Direction.INPUT
                return

            # Returnedonly hints towards output, however in some cases
            # it is inputoutput. In particular if next / type exist,
            # which are used to link in other structures without having
            # to introduce new APIs. E.g. xrGetPhysicalDeviceProperties2KHR.
            if "next" in self.struct:
                self._direction = Direction.INPUT_OUTPUT
                return

            self._direction = Direction.OUTPUT
        else:
            # This should mostly be right. Count variables can be inout, but we don't care about these yet.
            self._direction = Direction.OUTPUT

    def _set_format_string(self):
        """ Internal helper function to be used by constructor to set format string. """

        # Determine a format string used by code generation for traces.
        # 64-bit types need a conversion function.
        self.format_conv = None
        if self.is_static_array() or self.is_pointer():
            self.format_str = "%p"
        else:
            if self.type_info["category"] in ["bitmask", "enum"]:
                self.format_str = "%#x"
            elif self.is_handle():
                # We use uint64_t for non-dispatchable handles as opposed to pointers
                # for dispatchable handles.
                if self.handle.is_dispatchable():
                    self.format_str = "%p"
                else:
                    self.format_str = "0x%s"
                    self.format_conv = "wine_dbgstr_longlong({0})"
            elif self.type == "float":
                self.format_str = "%f"
            elif self.type == "int":
                self.format_str = "%d"
            elif self.type == "int32_t":
                self.format_str = "%d"
            elif self.type == "size_t":
                self.format_str = "0x%s"
                self.format_conv = "wine_dbgstr_longlong({0})"
            elif self.type in ["uint16_t", "uint32_t", "XrBool32"]:
                self.format_str = "%u"
            elif self.type in ["uint64_t","XrAsyncRequestIdFB"]:
                self.format_str = "0x%s"
                self.format_conv = "wine_dbgstr_longlong({0})"
            elif self.type == "HANDLE":
                self.format_str = "%p"
            elif self.type in ["XrSystemId", "XrPath", "XrTime", "XrDuration", "XrControllerModelKeyMSFT", "XrMarkerML"]:
                self.format_str = "0x%s"
                self.format_conv = "wine_dbgstr_longlong({0})"
            elif self.type in ["XrVector2f"]:
                self.format_str = "%f, %f"
                self.format_conv = "{0}.x, {0}.y"
            elif self.type in ["XrPosef"]:
                self.format_str = "{{%f, %f, %f, %f}, {%f %f %f}}"
                self.format_conv = "{0}.orientation.x, {0}.orientation.y, {0}.orientation.z, {0}.orientation.w, {0}.position.x, {0}.position.y, {0}.position.z"
            elif self.type in ["VisualID", "xcb_visualid_t", "VkInstance"]:
                # Don't care about Linux specific types.
                self.format_str = ""
            else:
                LOGGER.warning("Unhandled type: {0}".format(self.type_info))

    def copy(self, direction):
        if direction == Direction.INPUT:
            if self.is_dynamic_array():
                return "    {0}_host = convert_{1}_array_win_to_host({0}, {2});\n".format(self.name, self.type, self.dyn_array_len)
            else:
                return "    convert_{0}_win_to_host({1}, &{1}_host);\n".format(self.type, self.name)
        else:
            if self.is_dynamic_array():
                LOGGER.error("Unimplemented output conversion for: {0}".format(self.name))
            else:
                return "    convert_{0}_host_to_win(&{1}_host, {1});\n".format(self.type, self.name)

    def definition(self, postfix=None):
        """ Return prototype for the parameter. E.g. 'const char *foo' """

        proto = ""
        if self.const:
            proto += self.const + " "

        proto += self.type

        if self.is_pointer():
            proto += " {0}{1}".format(self.pointer, self.name)
        else:
            proto += " " + self.name

        # Allows appending something to the variable name useful for
        # win32 to host conversion.
        if postfix is not None:
            proto += postfix

        if self.is_static_array():
            proto += "[{0}]".format(self.array_len)

        return proto

    def direction(self):
        """ Returns parameter direction: input, output, input_output.

        Parameter direction in OpenXR is not straight-forward, which this function determines.
        """

        return self._direction

    def dispatch_table(self):
        """ Return functions dispatch table pointer for dispatchable objects. """

        if not self.is_dispatchable():
            return None

        if self.type in AUTO_MAPPED_HANDLES:
            return "(*get_dispatch_table((uint64_t)({0})))".format(self.name)
        else:
            return "((wine_{0} *){1})->{2}".format(self.type, self.name, self.handle.dispatch_table())

    def format_string(self):
        return self.format_str

    def free(self):
        if self.is_dynamic_array():
            if self.struct.returnedonly:
                # For returnedonly, counts is stored in a pointer.
                return "    free_{0}_array({1}_host, *{2});\n".format(self.type, self.name, self.dyn_array_len)
            else:
                return "    free_{0}_array({1}_host, {2});\n".format(self.type, self.name, self.dyn_array_len)
        else:
            # We are operating on a single structure. Some structs (very rare) contain dynamic members,
            # which would need freeing.
            if self.struct.needs_free():
                return "    free_{0}(&{1}_host);\n".format(self.type, self.name)
        return ""

    def get_conversions(self):
        """ Get a list of conversions required for this parameter if any.
        Parameters which are structures may require conversion between win32
        and the host platform. This function returns a list of conversions
        required.
        """

        if not self.is_struct():
            return None

        self.struct.needs_struct_extensions_conversion()
        for m in self.struct:
            m.needs_struct_extensions_conversion()

        if not self.needs_conversion():
            return None

        conversions = []

        # Collect any member conversions first, so we can guarantee
        # those functions will be defined prior to usage by the
        # 'parent' param requiring conversion.
        for m in self.struct:
            if not m.is_struct():
                continue

            if not m.needs_conversion():
                continue

            conversions.extend(m.get_conversions())

        # Conversion requirements for the 'parent' parameter.
        if self.input_conv is not None:
            conversions.append(self.input_conv)
        if self.output_conv is not None:
            conversions.append(self.output_conv)
        if self.free_func is not None:
            conversions.append(self.free_func)

        return conversions

    def is_const(self):
        return self.const is not None

    def is_dynamic_array(self):
        return self.dyn_array_len is not None

    def is_dispatchable(self):
        if not self.is_handle():
            return False

        return self.handle.is_dispatchable()

    def is_handle(self):
        return self.handle is not None

    def is_pointer(self):
        return self.pointer is not None

    def is_static_array(self):
        return self.array_len is not None

    def is_struct(self):
        return self.struct is not None

    def needs_conversion(self):
        """ Returns if parameter needs conversion between win32 and host. """

        if not self.is_struct():
            return False

        # If a structure needs alignment changes, it means we need to
        # perform parameter conversion between win32 and host.
        if self.struct.needs_conversion():
            return True

        return False

    def needs_free(self):
        return self.free_func is not None

    def needs_input_conversion(self):
        return self.input_conv is not None

    def needs_output_conversion(self):
        return self.output_conv is not None

    def variable(self, conv=False):
        """ Returns 'glue' code during generation of a function call on how to access the variable.
        This function handles various scenarios such as 'unwrapping' if dispatchable objects and
        renaming of parameters in case of win32 -> host conversion.

        Args:
            conv (bool, optional): Enable conversion if the param needs it. This appends '_host' to the name.
        """

        if conv and self.needs_conversion():
            if self.is_dynamic_array():
                return "{0}_host".format(self.name)
            else:
                return "&{0}_host".format(self.name)
        else:
            # We need to pass the native handle to the native calls.
            native_handle = self.handle.native_handle(self.name) if self.is_handle() else None
            return native_handle if native_handle else self.name


class XrStruct(Sequence):
    """ Class which represents the type union and struct. """

    def __init__(self, name, members, returnedonly, structextends, alias=None, union=False, dep_level=1000):
        self.name = name
        self.members = members
        self.returnedonly = returnedonly
        self.structextends = structextends
        self.required = False
        self.alias = alias
        self.union = union
        self.type_info = None # To be set later.
        self.struct_extensions = []
        self.aliased_by = []
        self.dep_level = dep_level

    def __getitem__(self, i):
        return self.members[i]

    def __len__(self):
        return len(self.members)

    @staticmethod
    def from_alias(struct, alias):
        name = struct.attrib.get("name")
        aliasee = XrStruct(name, alias.members, alias.returnedonly, alias.structextends, alias=alias)

        alias.add_aliased_by(aliasee)
        return aliasee

    @staticmethod
    def from_xml(struct):
        # Unions and structs are the same parsing wise, but we need to
        # know which one we are dealing with later on for code generation.
        union = True if struct.attrib["category"] == "union" else False

        name = struct.attrib.get("name")

        # 'Output' structures for which data is filled in by the API are
        # marked as 'returnedonly'.
        returnedonly = True if struct.attrib.get("returnedonly") else False

        structextends = struct.attrib.get("structextends")
        structextends = structextends.split(",") if structextends else []

        members = []
        for member in struct.findall("member"):
            xr_member = XrMember.from_xml(member)
            members.append(xr_member)

        if name in STRUCTS_PUT_FIRST:
            dep_level = 0
        else:
            dep_level = 1000
        return XrStruct(name, members, returnedonly, structextends, union=union, dep_level=dep_level)

    @staticmethod
    def decouple_structs(structs):
        """ Helper function which decouples a list of structs.
        Structures often depend on other structures. To make the C compiler
        happy we need to define 'substructures' first. This function analyzes
        the list of structures and reorders them in such a way that they are
        decoupled.
        """

        tmp_structs = list(structs) # Don't modify the original structures.
        decoupled_structs = []

        while (len(tmp_structs) > 0):
            for struct in tmp_structs:
                dependends = False

                if not struct.required:
                    tmp_structs.remove(struct)
                    continue

                for m in struct:
                    if not (m.is_struct() or m.is_union()):
                        continue

                    # XrBaseInstructure and XrBaseOutStructure reference themselves.
                    if m.type == struct.name:
                        break

                    found = False
                    # Check if a struct we depend on has already been defined.
                    for s in decoupled_structs:
                        if s.name == m.type:
                            found = True
                            break

                    if not found:
                        # Check if the struct we depend on is even in the list of structs.
                        # If found now, it means we haven't met all dependencies before we
                        # can operate on the current struct.
                        # When generating 'host' structs we may not be able to find a struct
                        # as the list would only contain the structs requiring conversion.
                        for s in tmp_structs:
                            if s.name == m.type:
                                dependends = True
                                break

                if dependends == False:
                    decoupled_structs.append(struct)
                    tmp_structs.remove(struct)

        return decoupled_structs

    def typedef(self):
        if not self.is_alias():
            if self.union:
                text = "typedef union {0} {0};\n".format(self.name)
            else:
                text = "typedef struct {0} {0};\n".format(self.name)
        else:
            text = ""

        for aliasee in self.aliased_by:
            text += "typedef {0} {1};\n".format(self.name, aliasee.name)

        return text

    def definition(self, align=False, conv=False, postfix=None):
        """ Convert structure to textual definition.

        Args:
            align (bool, optional): enable alignment to 64-bit for win32 struct compatibility.
            conv (bool, optional): enable struct conversion if the struct needs it.
            postfix (str, optional): text to append to end of struct name, useful for struct renaming.
        """

        # Only define alias structs when doing conversions
        if self.is_alias() and not conv:
            return ""

        if conv:
            text = "typedef "
        else:
            text = ""

        if self.union:
            text += "union {0}".format(self.name)
        else:
            text += "struct {0}".format(self.name)

        if postfix is not None:
            text += postfix

        text += "\n{\n"

        for m in self:
            if align and m.needs_alignment():
                text += "    {0};\n".format(m.definition(align=align))
            elif conv and m.needs_conversion():
                text += "    {0};\n".format(m.definition(conv=conv))
            else:
                text += "    {0};\n".format(m.definition())

        if postfix is not None:
            if conv:
                text += "}} {0}{1};\n\n".format(self.name, postfix)
            else:
                text += "}} {1};\n\n".format(self.name, postfix)
        else:
            text += "}};\n".format(self.name)

        text += "\n"

        return text

    def is_alias(self):
        return bool(self.alias)

    def add_aliased_by(self, aliasee):
        self.aliased_by.append(aliasee)

    def needs_alignment(self):
        """ Check if structure needs alignment for 64-bit data.
        Various structures need alignment on 64-bit variables due
        to compiler differences on 32-bit between Win32 and Linux.
        """

        for m in self.members:
            if m.needs_alignment():
                return True
        return False

    def needs_conversion(self):
        """ Returns if struct members needs conversion between win32 and host.
        Structures need conversion if they contain members requiring alignment
        or if they include other structures which need alignment.
        """

        if self.needs_alignment():
            return True

        for m in self.members:
            if m.type == self.name:
                continue
            if m.needs_conversion():
                return True
        return False

    def needs_free(self):
        """ Check if any struct member needs some memory freeing."""

        for m in self.members:
            if m.needs_free():
                return True

            continue

        return False

    def needs_struct_extensions_conversion(self):
        """ Checks if structure extensions in next chain need conversion. """
        ret = False

        for e in self.struct_extensions:
            if e.required and e.needs_conversion():
                LOGGER.error("Unhandled next chain conversion for {0}".format(e.name))
                ret = True

        return ret

    def set_type_info(self, types):
        """ Helper function to set type information from the type registry.
        This is needed, because not all type data is available at time of
        parsing.
        """
        for m in self.members:
            type_info = types[m.type]
            m.set_type_info(type_info)


class ConversionFunction(object):
    def __init__(self, array, dyn_array, direction, struct):
        self.array = array
        self.direction = direction
        self.dyn_array = dyn_array
        self.struct = struct
        self.type = struct.name

        self._set_name()

    def __eq__(self, other):
        return self.name == other.name

    def _generate_array_conversion_func(self):
        """ Helper function for generating a conversion function for array structs. """

        if self.direction == Direction.OUTPUT:
            params = ["const {0}_host *in".format(self.type), "uint32_t count"]
            return_type = self.type
        else:
            params = ["const {0} *in".format(self.type), "uint32_t count"]
            return_type = "{0}_host".format(self.type)

        # Generate function prototype.
        body = "static inline {0} *{1}(".format(return_type, self.name)
        body += ", ".join(p for p in params)
        body += ")\n{\n"

        body += "    {0} *out;\n".format(return_type)
        body += "    unsigned int i;\n\n"
        body += "    if (!in) return NULL;\n\n"

        body += "    out = HeapAlloc(GetProcessHeap(), 0, count * sizeof(*out));\n"

        body += "    for (i = 0; i < count; i++)\n"
        body += "    {\n"

        for m in self.struct:
            # TODO: support copying of next extension structures!
            # Luckily though no extension struct at this point needs conversion.
            body += "        " + m.copy("in[i].", "out[i].", self.direction)

        body += "    }\n\n"
        body += "    return out;\n"
        body += "}\n\n"
        return body

    def _generate_conversion_func(self):
        """ Helper function for generating a conversion function for non-array structs. """

        if self.direction == Direction.OUTPUT:
            params = ["const {0}_host *in".format(self.type), "{0} *out".format(self.type)]
        else:
            params = ["const {0} *in".format(self.type), "{0}_host *out".format(self.type)]

        body = "static inline void {0}(".format(self.name)

        # Generate parameter list
        body += ", ".join(p for p in params)
        body += ")\n{\n"

        body += "    if (!in) return;\n\n"

        if self.direction == Direction.INPUT and "next" in self.struct and self.struct.returnedonly:
            # We are dealing with an input_output parameter. For these we only need to copy
            # next and type as the other fields are filled in by the host. We do potentially
            # have to iterate over next and perform conversions based on switch(type)!
            # Luckily though no extension structs at this point need conversion.
            # TODO: support copying of next extension structures!
            body += "    out->next = in->next;\n"
            body += "    out->type = in->type;\n"
        else:
            for m in self.struct:
                # TODO: support copying of next extension structures!
                body += "    " + m.copy("in->", "out->", self.direction)

        body += "}\n\n"
        return body

    def _generate_static_array_conversion_func(self):
        """ Helper function for generating a conversion function for array structs. """

        if self.direction == Direction.OUTPUT:
            params = ["const {0}_host *in".format(self.type), "{0} *out".format(self.type), "uint32_t count"]
        else:
            params = ["const {0} *in".format(self.type), "{0} *out_host".format(self.type), "uint32_t count"]

        # Generate function prototype.
        body = "static inline void {0}(".format(self.name)
        body += ", ".join(p for p in params)
        body += ")\n{\n"
        body += "    unsigned int i;\n\n"
        body += "    if (!in) return;\n\n"
        body += "    for (i = 0; i < count; i++)\n"
        body += "    {\n"

        for m in self.struct:
            # TODO: support copying of next extension structures!
            body += "        " + m.copy("in[i].", "out[i].", self.direction)

        body += "    }\n"
        body += "}\n\n"
        return body

    def _set_name(self):
        if self.direction == Direction.INPUT:
            if self.array:
                name = "convert_{0}_static_array_win_to_host".format(self.type)
            elif self.dyn_array:
                name = "convert_{0}_array_win_to_host".format(self.type)
            else:
                name = "convert_{0}_win_to_host".format(self.type)
        else: # Direction.OUTPUT
            if self.array:
                name = "convert_{0}_static_array_host_to_win".format(self.type)
            elif self.dyn_array:
                name = "convert_{0}_array_host_to_win".format(self.type)
            else:
                name = "convert_{0}_host_to_win".format(self.type)

        self.name = name

    def definition(self):
        if self.array:
            return self._generate_static_array_conversion_func()
        elif self.dyn_array:
            return self._generate_array_conversion_func()
        else:
            return self._generate_conversion_func()


class FreeFunction(object):
    def __init__(self, dyn_array, struct):
        self.dyn_array = dyn_array
        self.struct = struct
        self.type = struct.name

        if dyn_array:
            self.name = "free_{0}_array".format(self.type)
        else:
            self.name = "free_{0}".format(self.type)

    def __eq__(self, other):
        return self.name == other.name

    def _generate_array_free_func(self):
        """ Helper function for cleaning up temporary buffers required for array conversions. """

        # Generate function prototype.
        body = "static inline void {0}({1}_host *in, uint32_t count)\n{{\n".format(self.name, self.type)

        # E.g. XrGraphicsPipelineCreateInfo_host needs freeing for pStages.
        if self.struct.needs_free():
            body += "    unsigned int i;\n\n"
            body += "    if (!in) return;\n\n"
            body += "    for (i = 0; i < count; i++)\n"
            body += "    {\n"

            for m in self.struct:
                if m.needs_conversion() and m.is_dynamic_array():
                    if m.is_const():
                        # Add a cast to ignore const on conversion structs we allocated ourselves.
                        body += "        free_{0}_array(({0}_host *)in[i].{1}, in[i].{2});\n".format(m.type, m.name, m.dyn_array_len)
                    else:
                        body += "        free_{0}_array(in[i].{1}, in[i].{2});\n".format(m.type, m.name, m.dyn_array_len)
                elif m.needs_conversion():
                    LOGGER.error("Unhandled conversion for {0}".format(m.name))
            body += "    }\n"
        else:
            body += "    if (!in) return;\n\n"

        body += "    HeapFree(GetProcessHeap(), 0, in);\n"

        body += "}\n\n"
        return body

    def _generate_free_func(self):
        # E.g. XrCommandBufferBeginInfo.pInheritanceInfo needs freeing.
        if not self.struct.needs_free():
            return ""

        # Generate function prototype.
        body = "static inline void {0}({1}_host *in)\n{{\n".format(self.name, self.type)

        for m in self.struct:
            if m.needs_conversion() and m.is_dynamic_array():
                count = m.dyn_array_len if isinstance(m.dyn_array_len, int) else "in->{0}".format(m.dyn_array_len)
                if m.is_const():
                    # Add a cast to ignore const on conversion structs we allocated ourselves.
                    body += "    free_{0}_array(({0}_host *)in->{1}, {2});\n".format(m.type, m.name, count)
                else:
                    body += "    free_{0}_array(in->{1}, {2});\n".format(m.type, m.name, count)

        body += "}\n\n"
        return body

    def definition(self):
        if self.dyn_array:
            return self._generate_array_free_func()
        else:
            # Some structures need freeing too if they contain dynamic arrays.
            # E.g. XrCommandBufferBeginInfo
            return self._generate_free_func()


class StructChainConversionFunction(object):
    def __init__(self, direction, struct):
        self.direction = direction
        self.struct = struct
        self.type = struct.name

        self.name = "convert_{0}_struct_chain".format(self.type)

    def __eq__(self, other):
        return self.name == other.name

    def prototype(self, postfix=""):
        return "XrResult {0}(const void *next, {1} *out_struct) {2}".format(self.name, self.type, postfix).strip()

    def definition(self):
        body = self.prototype()
        body += "\n{\n"

        body += "    XrBaseOutStructure *out_header = (XrBaseOutStructure *)out_struct;\n";
        body += "    const XrBaseInStructure *in_header;\n\n";

        body += "    out_header->next = NULL;\n\n"

        body += "    for (in_header = next; in_header; in_header = in_header->next)\n"
        body += "    {\n"
        body += "        switch (in_header->type)\n"
        body += "        {\n"

        # Ignore to not confuse host loader.
        body += "        case XR_TYPE_INSTANCE_CREATE_INFO:\n"
        body += "            break;\n\n"

        for e in self.struct.struct_extensions:
            if not e.required:
                continue

            stype = next(x for x in e.members if x.name == "type")

            body += "        case {0}:\n".format(stype.values)
            body += "        {\n"

            body += "            const {0} *in = (const {0} *)in_header;\n".format(e.name)
            body += "            {0} *out;\n\n".format(e.name)

            body += "            if (!(out = HeapAlloc(GetProcessHeap(), 0, sizeof(*out)))) goto out_of_memory;\n\n"

            for m in e:
                if m.name == "next":
                    body += "            out->next = NULL;\n"
                else:
                    body += "            " + m.copy("in->", "out->", self.direction)

            body += "\n            out_header->next = (XrBaseOutStructure *)out;\n"
            body += "            out_header = out_header->next;\n"
            body += "            break;\n"
            body += "        }\n\n"

        body += "        default:\n"
        body += "            WINE_FIXME(\"Application requested a linked structure of type %u.\\n\", in_header->type);\n"

        body += "        }\n"
        body += "    }\n\n"

        body += "    return XR_SUCCESS;\n"

        if any(x for x in self.struct.struct_extensions if x.required):
            body += "\nout_of_memory:\n"
            body += "    free_{0}_struct_chain(out_struct);\n".format(self.type)
            body += "    return XR_ERROR_OUT_OF_HOST_MEMORY;\n"

        body += "}\n\n"
        return body

class FreeStructChainFunction(object):
    def __init__(self, struct):
        self.struct = struct
        self.type = struct.name

        self.name = "free_{0}_struct_chain".format(self.type)

    def __eq__(self, other):
        return self.name == other.name

    def prototype(self, postfix=""):
        return "void {0}({1} *s) {2}".format(self.name, self.type, postfix).strip()

    def definition(self):
        body = self.prototype()
        body += "\n{\n"

        body += "    XrBaseOutStructure *header = (void *)s->next;\n\n";

        body += "    while (header)\n"
        body += "    {\n"
        body += "        void *prev = header;\n"
        body += "        header = header->next;\n"
        body += "        HeapFree(GetProcessHeap(), 0, prev);\n"
        body += "    }\n\n"

        body += "    s->next = NULL;\n"

        body += "}\n\n"
        return body


class XrGenerator(object):
    def __init__(self, registry):
        self.registry = registry

        # Build a list conversion functions for struct conversion.
        self.conversions = []
        self.struct_chain_conversions = []
        self.host_structs = []
        for func in self.registry.funcs.values():
            if not func.is_required():
                continue

            if not func.needs_conversion():
                continue

            conversions = func.get_conversions()
            for conv in conversions:
                # Pull in any conversions for openxr_thunks.c.
                if func.needs_thunk():
                    # Append if we don't already have this conversion.
                    if not any(c == conv for c in self.conversions):
                        self.conversions.append(conv)

                # Structs can be used in different ways by different conversions
                # e.g. array vs non-array. Just make sure we pull in each struct once.
                if not any(s.name == conv.struct.name for s in self.host_structs):
                    self.host_structs.append(conv.struct)

        for struct in self.registry.structs:
            if struct.name in STRUCT_CHAIN_CONVERSIONS:
                self.struct_chain_conversions.append(StructChainConversionFunction(Direction.INPUT, struct))
                self.struct_chain_conversions.append(FreeStructChainFunction(struct))

    def _generate_copyright(self, f, spec_file=False):
        f.write("# " if spec_file else "/* ")
        f.write("Automatically generated from OpenXR xr.xml; DO NOT EDIT!\n")
        lines = ["", "This file is generated from OpenXR xr.xml file covered",
            "by the following copyright and permission notice:"]
        lines.extend([l.rstrip(" ") for l in self.registry.copyright.splitlines()])
        for line in lines:
            f.write("{0}{1}".format("# " if spec_file else " * ", line).rstrip(" ") + "\n")
        f.write("\n" if spec_file else " */\n\n")

    def generate_thunks_c(self, f, prefix):
        self._generate_copyright(f)

        f.write("#include \"wine/debug.h\"\n")
        f.write("#include \"wine/vulkan.h\"\n")
        f.write("#include \"d3d11.h\"\n")
        f.write("#include \"d3d12.h\"\n")
        f.write("#define WINE_XR_HOST\n")
        f.write("#include \"wineopenxr.h\"\n")
        f.write("#include \"openxr_private.h\"\n\n")

        f.write("WINE_DEFAULT_DEBUG_CHANNEL(openxr);\n\n")

        # Generate any conversion helper functions.
        f.write("#if defined(USE_STRUCT_CONVERSION)\n")
        for conv in self.conversions:
            f.write(conv.definition())
        f.write("#endif /* USE_STRUCT_CONVERSION */\n\n")

        for conv in self.struct_chain_conversions:
            f.write(conv.definition())

        # Create thunks for instance and device functions.
        # Global functions don't go through the thunks.
        for xr_func in self.registry.funcs.values():
            if not xr_func.is_required():
                continue

            #if xr_func.is_global_func():
            #    continue

            if not xr_func.needs_thunk():
                continue

            # Exports symbols for Core functions.
            if not xr_func.is_core_func() and not xr_func.needs_private_thunk():
                f.write("static ")

            if xr_func.needs_private_thunk():
                f.write(xr_func.thunk(prefix="thunk_"))
            else:
                f.write(xr_func.thunk(prefix=prefix, call_conv="WINAPI"))

        f.write("static const struct openxr_func xr_dispatch_table[] =\n{\n")
        for xr_func in self.registry.instance_funcs:
            if not xr_func.is_required():
                continue
            f.write("    {{\"{0}\", &{1}{0}}},\n".format(xr_func.name, prefix))
        f.write("};\n\n")

        f.write("void *wine_xr_proc_addr(const char *name)\n")
        f.write("{\n")
        f.write("    unsigned int i;\n")
        f.write("    for (i = 0; i < ARRAY_SIZE(xr_dispatch_table); i++)\n")
        f.write("    {\n")
        f.write("        if (strcmp(xr_dispatch_table[i].name, name) == 0)\n")
        f.write("        {\n")
        f.write("            WINE_TRACE(\"Found name=%s in instance table\\n\", wine_dbgstr_a(name));\n")
        f.write("            return xr_dispatch_table[i].func;\n")
        f.write("        }\n")
        f.write("    }\n")
        f.write("    return NULL;\n")
        f.write("}\n\n")

        # Create array of instance extensions.
        f.write("static const char * const xr_extensions[] =\n{\n")
        for ext in self.registry.extensions:
            f.write("    \"{0}\",\n".format(ext["name"]))
        f.write("};\n\n")

        f.write("BOOL wine_xr_extension_supported(const char *name)\n")
        f.write("{\n")
        f.write("    unsigned int i;\n")
        f.write("    for (i = 0; i < ARRAY_SIZE(xr_extensions); i++)\n")
        f.write("    {\n")
        f.write("        if (strcmp(xr_extensions[i], name) == 0)\n")
        f.write("            return TRUE;\n")
        f.write("    }\n")
        f.write("    return FALSE;\n")
        f.write("}\n")

    def generate_thunks_h(self, f, prefix):
        self._generate_copyright(f)

        f.write("#ifndef __WINE_OPENXR_THUNKS_H\n")
        f.write("#define __WINE_OPENXR_THUNKS_H\n\n")

        f.write("#define WINE_XR_VERSION XR_API_VERSION_{0}_{1}\n\n".format(WINE_XR_VERSION[0], WINE_XR_VERSION[1]))

        # Generate prototypes for device and instance functions requiring a custom implementation.
        f.write("/* Functions for which we have custom implementations outside of the thunks. */\n")
        for xr_func in self.registry.funcs.values():
            if not xr_func.is_required():# or xr_func.is_global_func():
                continue
            if xr_func.needs_thunk() and not xr_func.needs_private_thunk():
                continue

            if xr_func.is_core_func():
                f.write("{0};\n".format(xr_func.prototype("WINAPI", prefix="wine_")))
            else:
                f.write("{0};\n".format(xr_func.prototype("WINAPI", prefix="wine_")))
        f.write("\n")

        f.write("/* Private thunks */\n")
        for xr_func in self.registry.funcs.values():
            if xr_func.needs_private_thunk():
                f.write("{0};\n".format(xr_func.prototype(prefix="thunk_")))
        f.write("\n")

        for struct in self.host_structs:
            f.write(struct.definition(align=False, conv=True, postfix="_host"))
        f.write("\n")

        for func in self.struct_chain_conversions:
            f.write(func.prototype() + ";\n")
        f.write("\n")

        f.write("/* For use by xrInstance and children */\n")
        f.write("struct openxr_instance_funcs\n{\n")
        for xr_func in self.registry.instance_funcs:
            if not xr_func.is_required():
                continue

            if not xr_func.needs_dispatch():
                LOGGER.debug("skipping {0} in openxr_instance_funcs".format(xr_func.name))
                continue

            if xr_func.needs_conversion():
                f.write("#if defined(USE_STRUCT_CONVERSION)\n")
                f.write("    {0};\n".format(xr_func.pfn(conv=True)))
                f.write("#else\n")
                f.write("    {0};\n".format(xr_func.pfn(conv=False)))
                f.write("#endif\n")
            else:
                f.write("    {0};\n".format(xr_func.pfn(conv=False)))
        f.write("};\n\n")

        f.write("#define ALL_XR_INSTANCE_FUNCS() \\\n")
        first = True
        for xr_func in self.registry.instance_funcs:
            if not xr_func.is_required():
                continue

            if not xr_func.needs_dispatch():
                LOGGER.debug("skipping {0} in ALL_XR_INSTANCE_FUNCS".format(xr_func.name))
                continue

            if first:
                f.write("    USE_XR_FUNC({0})".format(xr_func.name))
                first = False
            else:
                f.write(" \\\n    USE_XR_FUNC({0})".format(xr_func.name))
        f.write("\n\n")

        f.write("#endif /* __WINE_OPENXR_THUNKS_H */\n")

    def generate_openxr_h(self, f):
        self._generate_copyright(f)
        f.write("#ifndef __WINE_OPENXR_H\n")
        f.write("#define __WINE_OPENXR_H\n\n")

        f.write("#include <windef.h>\n")
        f.write("#include <stdint.h>\n\n")

        f.write("/* Define WINE_XR_HOST to get 'host' headers. */\n")
        f.write("#ifdef WINE_XR_HOST\n")
        f.write("#define XRAPI_CALL\n")
        f.write('#define WINE_XR_ALIGN(x)\n')
        f.write("#endif\n\n")

        f.write("#ifndef XRAPI_CALL\n")
        f.write("#define XRAPI_CALL __stdcall\n")
        f.write("#endif\n\n")

        f.write("#ifndef XRAPI_PTR\n")
        f.write("#define XRAPI_PTR XRAPI_CALL\n")
        f.write("#endif\n\n")

        f.write("#ifndef WINE_XR_ALIGN\n")
        f.write("#define WINE_XR_ALIGN DECLSPEC_ALIGN\n")
        f.write("#endif\n\n")

        f.write("#ifdef __x86_64__\n")
        f.write("#define XR_PTR_SIZE 8\n")
        f.write("#endif\n\n")

        # The overall strategy is to define independent constants and datatypes,
        # prior to complex structures and function calls to avoid forward declarations.
        for const in self.registry.consts:
            # For now just generate things we may not need. The amount of parsing needed
            # to get some of the info is tricky as you need to figure out which structure
            # references a certain constant.
            f.write(const.definition())
        f.write("\n")

        for define in self.registry.defines:
            f.write(define.definition())

        for handle in self.registry.handles:
            # For backward compatibility also create definitions for aliases.
            # These types normally don't get pulled in as we use the new types
            # even in legacy functions if they are aliases.
            if handle.is_required() or handle.is_alias():
                 f.write(handle.definition())
        f.write("\n")

        for base_type in self.registry.base_types:
            f.write(base_type.definition())
        f.write("\n")

        for bitmask in self.registry.bitmasks:
            f.write(bitmask.definition())
        f.write("\n")

        # Define enums, this includes values for some of the bitmask types as well.
        for enum in self.registry.enums.values():
            if enum.required:
                f.write(enum.definition())

        # This generates both structures and unions. Since structures
        # may depend on other structures/unions, we need a list of
        # decoupled structs.
        # Note: unions are stored in structs for dependency reasons,
        # see comment in parsing section.
        structs = XrStruct.decouple_structs(self.registry.structs)

        for struct in structs:
            f.write(struct.typedef())

        for fp in self.registry.funcpointers:
            if fp.required:
                f.write(fp.definition())
        f.write("\n")

        for struct in structs:
            LOGGER.debug("Generating struct: {0}".format(struct.name))
            f.write(struct.definition(align=True))

        for func in self.registry.funcs.values():
            if not func.is_required():
                LOGGER.debug("Skipping PFN definition for: {0}".format(func.name))
                continue

            f.write("typedef {0};\n".format(func.pfn(prefix="PFN", call_conv="XRAPI_PTR")))
        f.write("\n")

        f.write("#ifndef XR_NO_PROTOTYPES\n")
        for func in self.registry.funcs.values():
            if not func.is_required():
                LOGGER.debug("Skipping API definition for: {0}".format(func.name))
                continue

            LOGGER.debug("Generating API definition for: {0}".format(func.name))
            f.write("{0};\n".format(func.prototype(call_conv="XRAPI_CALL")))
        f.write("#endif /* XR_NO_PROTOTYPES */\n\n")

        f.write("#endif /* __WINE_OPENXR_H */\n")


class XrRegistry(object):
    def __init__(self, reg_filename):
        # Used for storage of type information.
        self.base_types = None
        self.bitmasks = None
        self.consts = None
        self.defines = None
        self.enums = None
        self.funcpointers = None
        self.handles = None
        self.structs = None

        # We aggregate all types in here for cross-referencing.
        self.funcs = {}
        self.types = {}

        self.version_regex = re.compile(
            r'^'
            r'XR_VERSION_'
            r'(?P<major>[0-9])'
            r'_'
            r'(?P<minor>[0-9])'
            r'$'
        )

        # Overall strategy for parsing the registry is to first
        # parse all type / function definitions. Then parse
        # features and extensions to decide which types / functions
        # to actually 'pull in' for code generation. For each type or
        # function call we want we set a member 'required' to True.
        tree = ET.parse(reg_filename)
        root = tree.getroot()
        self._parse_enums(root)
        self._parse_types(root)
        self._parse_commands(root)

        # Pull in any required types and functions.
        self._parse_features(root)
        self._parse_extensions(root)

        self.copyright = root.find('./comment').text

    def _is_feature_supported(self, feature):
        version = self.version_regex.match(feature)
        if not version:
            return True

        version = tuple(map(int, version.group('major', 'minor')))
        return version <= WINE_XR_VERSION

    def _is_extension_supported(self, extension):
        # We disable some extensions as either we haven't implemented
        # support yet or because they are for platforms other than win32.
        return extension not in UNSUPPORTED_EXTENSIONS

    def mark_bitmask_dependencies(self, bitmask):
        if bitmask.requires is not None:
            self.types[bitmask.requires]["data"].required = True

    def mark_funcpointer_dependencies(self, fp):
        for m in fp.members:
            type_info = self.types[m.type]

            # Complex types have a matching definition e.g. XrStruct.
            # Not needed for base types such as uint32_t.
            if "data" in type_info:
                self.types[m.type]["data"].required = True

    def mark_struct_dependencies(self, struct):
         for m in struct:
            type_info = self.types[m.type]


            # Complex types have a matching definition e.g. XrStruct.
            # Not needed for base types such as uint32_t.
            if "data" in type_info:
                if self.types[m.type]["data"].required:
                    continue
                self.types[m.type]["data"].required = True

            if type_info["category"] == "struct":
                # Yay, recurse
                self.mark_struct_dependencies(type_info["data"])
            elif type_info["category"] == "funcpointer":
                self.mark_funcpointer_dependencies(type_info["data"])
            elif type_info["category"] == "bitmask":
                self.mark_bitmask_dependencies(type_info["data"])

    def _mark_command_required(self, command):
        """ Helper function to mark a certain command and the datatypes it needs as required."""
        LOGGER.debug("marking " + command + " as required")
        func = self.funcs[command]
        func.required = True

        # Pull in return type
        if func.type != "void":
            self.types[func.type]["data"].required = True

        # Analyze parameter dependencies and pull in any type needed.
        for p in func.params:
            type_info = self.types[p.type]

            # Check if we are dealing with a complex type e.g. XrEnum, XrStruct and others.
            if "data" not in type_info:
                continue

            # Mark the complex type as required.
            type_info["data"].required = True
            if type_info["category"] == "struct":
                struct = type_info["data"]
                self.mark_struct_dependencies(struct)
            elif type_info["category"] == "bitmask":
                self.mark_bitmask_dependencies(type_info["data"])

    def _parse_commands(self, root):
        """ Parse command section containing the OpenXR function calls. """
        funcs = {}
        commands = root.findall("./commands/")

        # As of Vulkan 1.1, various extensions got promoted to Core.
        # The old commands (e.g. KHR) are available for backwards compatibility
        # and are marked in xr.xml as 'alias' to the non-extension type.
        # The registry likes to avoid data duplication, so parameters and other
        # metadata need to be looked up from the Core command.
        # We parse the alias commands in a second pass.
        alias_commands = []
        for command in commands:
            alias_name = command.attrib.get("alias")
            if alias_name:
                alias_commands.append(command)
                continue

            func = XrFunction.from_xml(command, self.types)
            funcs[func.name] = func

        for command in alias_commands:
            alias_name = command.attrib.get("alias")
            alias = funcs[alias_name]
            func = XrFunction.from_alias(command, alias)
            funcs[func.name] = func

        # To make life easy for the code generation, separate all function
        # calls out in the 3 types of functions: device, global and instance.
        instance_funcs = []
        for func in funcs.values():
            if not func.name in NOT_OUR_FUNCTIONS:
                instance_funcs.append(func)

        # Sort function lists by name and store them.
        self.instance_funcs = sorted(instance_funcs, key=lambda func: func.name)

        # The funcs dictionary is used as a convenient way to lookup function
        # calls when needed e.g. to adjust member variables.
        self.funcs = OrderedDict(sorted(funcs.items()))

    def _parse_enums(self, root):
        """ Parse enums section or better described as constants section. """
        enums = {}
        self.consts = []
        for enum in root.findall("./enums"):
            name = enum.attrib.get("name")
            _type = enum.attrib.get("type")

            if _type in ("enum", "bitmask"):
                enums[name] = XrEnum.from_xml(enum)
            else:
                # If no type is set, we are dealing with API constants.
                for value in enum.findall("enum"):
                    # If enum is an alias, set the value to the alias name.
                    # E.g. XR_LUID_SIZE_KHR is an alias to XR_LUID_SIZE.
                    alias = value.attrib.get("alias")
                    if alias:
                        self.consts.append(XrConstant(value.attrib.get("name"), alias))
                    else:
                        self.consts.append(XrConstant(value.attrib.get("name"), value.attrib.get("value")))

        self.enums = OrderedDict(sorted(enums.items()))

    def _process_require_enum(self, enum_elem, ext=None, only_aliased=False):
        if "extends" in enum_elem.keys():
            enum = self.types[enum_elem.attrib["extends"]]["data"]

            # Need to define XrEnumValues which were aliased to by another value. This is necessary
            # from XR spec version 1.2.135 where the provisional XR_KHR_ray_tracing extension was
            # added which altered XR_NV_ray_tracing's XrEnumValues to alias to the provisional
            # extension.
            aliased = False
            for _, t in self.types.items():
                if t["category"] != "enum":
                    continue
                if not t["data"]:
                    continue
                for value in t["data"].values:
                    if value.alias == enum_elem.attrib["name"]:
                        aliased = True

            if only_aliased and not aliased:
                return

            if "bitpos" in enum_elem.keys():
                # We need to add an extra value to an existing enum type.
                # E.g. XR_FORMAT_FEATURE_SAMPLED_IMAGE_FILTER_CUBIC_BIT_IMG to XrFormatFeatureFlagBits.
                enum.add(XrEnumValue(enum_elem.attrib["name"], value=(1 << int(enum_elem.attrib["bitpos"])), hex=True))

            elif "offset" in enum_elem.keys():
                # Extensions promoted to Core, have the extension number as part
                # of the enum value. Else retrieve from the extension tag.
                if enum_elem.attrib.get("extnumber"):
                    ext_number = int(enum_elem.attrib.get("extnumber"))
                else:
                    ext_number = int(ext.attrib["number"])
                offset = int(enum_elem.attrib["offset"])
                value = EXT_BASE + (ext_number - 1) * EXT_BLOCK_SIZE + offset

                # Deal with negative values.
                direction = enum_elem.attrib.get("dir")
                if direction is not None:
                    value = -value

                enum.add(XrEnumValue(enum_elem.attrib["name"], value=value))

            elif "value" in enum_elem.keys():
                enum.add(XrEnumValue(enum_elem.attrib["name"], value=int(enum_elem.attrib["value"])))
            elif "alias" in enum_elem.keys():
                enum.add(XrEnumValue(enum_elem.attrib["name"], alias=enum_elem.attrib["alias"]))

        elif "value" in enum_elem.keys():
            # Constants are not aliased, no need to add them here, they'll get added later on.
            if only_aliased:
                return

            self.consts.append(XrConstant(enum_elem.attrib["name"], enum_elem.attrib["value"]))

    @staticmethod
    def _require_type(type_info):
        if type_info.is_alias():
            type_info = type_info.alias
        type_info.required = True
        if type(type_info) == XrStruct:
            for member in type_info.members:
                if "data" in member.type_info:
                  XrRegistry._require_type(member.type_info["data"])

    def _parse_extensions(self, root):
        """ Parse extensions section and pull in any types and commands for this extension. """
        extensions = []
        exts = root.findall("./extensions/extension")
        deferred_exts = []

        def process_ext(ext, deferred=False):
            ext_name = ext.attrib["name"]

            # Set extension name on any functions calls part of this extension as we
            # were not aware of the name during initial parsing.
            commands = ext.findall("require/command")
            for command in commands:
                cmd_name = command.attrib["name"]
                self.funcs[cmd_name].extensions.append(ext_name)

            # Some extensions are not ready or have numbers reserved as a place holder.
            if ext.attrib["supported"] == "disabled":
                LOGGER.debug("Skipping disabled extension: {0}".format(ext_name))
                return

            protect = ext.attrib.get("protect", None)
            if not protect is None and \
                    not protect in ALLOWED_PROTECTS:
                return

            # Defer extensions with 'sortorder' as they are order-dependent for spec-parsing.
            if not deferred and "sortorder" in ext.attrib:
                deferred_exts.append(ext)
                return

            # Disable highly experimental extensions as the APIs are unstable and can
            # change between minor revisions until API is final and becomes KHR
            # or NV.
            if "KHX" in ext_name or "NVX" in ext_name:
                LOGGER.debug("Skipping experimental extension: {0}".format(ext_name))
                return

            # Extensions can define XrEnumValues which alias to provisional extensions. Pre-process
            # extensions to define any required XrEnumValues before the platform check below.
            for require in ext.findall("require"):
                # Extensions can add enum values to Core / extension enums, so add these.
                for enum_elem in require.findall("enum"):
                    self._process_require_enum(enum_elem, ext, only_aliased=True)

            platform = ext.attrib.get("platform")
            if platform and platform != "win32":
                LOGGER.debug("Skipping extensions {0} for platform {1}".format(ext_name, platform))
                return

            if not self._is_extension_supported(ext_name):
                LOGGER.debug("Skipping unsupported extension: {0}".format(ext_name))
                return
            elif "requires" in ext.attrib:
                # Check if this extension builds on top of another unsupported extension.
                requires = ext.attrib["requires"].split(",")
                if len(set(requires).intersection(UNSUPPORTED_EXTENSIONS)) > 0:
                    return

            LOGGER.debug("Loading extension: {0}".format(ext_name))

            # Extensions can define one or more require sections each requiring
            # different features (e.g. Vulkan 1.1). Parse each require section
            # separately, so we can skip sections we don't want.
            for require in ext.findall("require"):
                # Extensions can add enum values to Core / extension enums, so add these.
                for enum_elem in require.findall("enum"):
                    self._process_require_enum(enum_elem, ext)

                for t in require.findall("type"):
                    if t.attrib["name"] in self.types:
                        type_info = self.types[t.attrib["name"]]["data"]
                        self._require_type(type_info)
                feature = require.attrib.get("feature")
                if feature and not self._is_feature_supported(feature):
                    continue

                required_extension = require.attrib.get("extension")
                if required_extension and not self._is_extension_supported(required_extension):
                    continue

                # Pull in any commands we need. We infer types to pull in from the command
                # as well.
                for command in require.findall("command"):
                    cmd_name = command.attrib["name"]
                    self._mark_command_required(cmd_name)


            # Store a list with extensions.
            ext_info = {"name" : ext_name, "type" : ext.attrib["type"]}
            extensions.append(ext_info)


        # Process extensions, allowing for sortorder to defer extension processing
        for ext in exts:
            process_ext(ext)

        deferred_exts.sort(key=lambda ext: ext.attrib["sortorder"])

        # Respect sortorder
        for ext in deferred_exts:
            process_ext(ext, deferred=True)

        # Sort in alphabetical order.
        self.extensions = sorted(extensions, key=lambda ext: ext["name"])

    def _parse_features(self, root):
        """ Parse the feature section, which describes Core commands and types needed. """

        for feature in root.findall("./feature"):
            feature_name = feature.attrib["name"]
            for require in feature.findall("require"):
                LOGGER.info("Including features for {0}".format(require.attrib.get("comment")))
                for tag in require:
                    if tag.tag == "comment":
                        continue
                    elif tag.tag == "command":
                        if not self._is_feature_supported(feature_name):
                            continue
                        name = tag.attrib["name"]
                        LOGGER.debug("found command: " + name)
                        self._mark_command_required(name)
                    elif tag.tag == "enum":
                        self._process_require_enum(tag)
                    elif tag.tag == "type":
                        name = tag.attrib["name"]

                        # Skip pull in for openxr_platform_defines.h for now.
                        if name == "openxr_platform_defines":
                            continue

                        type_info = self.types[name]
                        type_info["data"].required = True

    def _parse_types(self, root):
        """ Parse types section, which contains all data types e.g. structs, typedefs etcetera. """
        types = root.findall("./types/type")

        base_types = []
        bitmasks = []
        defines = []
        funcpointers = []
        handles = []
        structs = []

        alias_types = []
        for t in types:
            type_info = {}
            type_info["category"] = t.attrib.get("category", None)
            type_info["requires"] = t.attrib.get("requires", None)

            # We parse aliases in a second pass when we know more.
            alias = t.attrib.get("alias")
            if alias:
                LOGGER.debug("Alias found: {0}".format(alias))
                alias_types.append(t)
                continue

            protect = t.attrib.get("protect", None)
            if not protect is None and \
                    not protect in ALLOWED_PROTECTS:
                continue

            if type_info["category"] in ["include"]:
                continue

            if type_info["category"] == "basetype":
                name = t.find("name").text
                _type = None
                if not t.find("type") is None:
                    _type = t.find("type").text
                basetype = XrBaseType(name, _type, collect_element_text(t))
                base_types.append(basetype)
                type_info["data"] = basetype

            # Basic C types don't need us to define them, but we do need data for them
            if type_info["requires"] == "xr_platform":
                requires = type_info["requires"]
                basic_c = XrBaseType(name, _type, collect_element_text(t), requires=requires)
                type_info["data"] = basic_c

            if type_info["category"] == "bitmask":
                name = t.find("name").text
                _type = t.find("type").text

                # Most bitmasks have a requires attribute used to pull in
                # required '*FlagBits" enum.
                requires = type_info["requires"]
                bitmask = XrBaseType(name, _type, collect_element_text(t), requires=requires)
                bitmasks.append(bitmask)
                type_info["data"] = bitmask

            if type_info["category"] == "define":
                define = XrDefine.from_xml(t)
                defines.append(define)
                type_info["data"] = define

            if type_info["category"] == "enum":
                name = t.attrib.get("name")
                # The type section only contains enum names, not the actual definition.
                # Since we already parsed the enum before, just link it in.
                try:
                    type_info["data"] = self.enums[name]
                except KeyError as e:
                    # Not all enums seem to be defined yet, typically that's for
                    # ones ending in 'FlagBits' where future extensions may add
                    # definitions.
                    type_info["data"] = None

            if type_info["category"] == "funcpointer":
                funcpointer = XrFunctionPointer.from_xml(t)
                funcpointers.append(funcpointer)
                type_info["data"] = funcpointer

            if type_info["category"] == "handle":
                handle = XrHandle.from_xml(t)
                handles.append(handle)
                type_info["data"] = handle

            if type_info["category"] in ["struct", "union"]:
                # We store unions among structs as some structs depend
                # on unions. The types are very similar in parsing and
                # generation anyway. The official Vulkan scripts use
                # a similar kind of hack.
                struct = XrStruct.from_xml(t)
                structs.append(struct)
                type_info["data"] = struct

            # Name is in general within a name tag else it is an optional
            # attribute on the type tag.
            name_elem = t.find("name")
            if name_elem is not None:
                type_info["name"] = name_elem.text
            else:
                type_info["name"] = t.attrib.get("name", None)

            # Store all type data in a shared dictionary, so we can easily
            # look up information for a given type. There are no duplicate
            # names.
            self.types[type_info["name"]] = type_info

        # Second pass for alias types, so we can retrieve all data from
        # the aliased object.
        for t in alias_types:
            type_info = {}
            type_info["category"] = t.attrib.get("category")
            type_info["name"] = t.attrib.get("name")

            alias = t.attrib.get("alias")

            if type_info["category"] == "bitmask":
                bitmask = XrBaseType(type_info["name"], alias, collect_element_text(t), alias=self.types[alias]["data"])
                bitmasks.append(bitmask)
                type_info["data"] = bitmask

            if type_info["category"] == "enum":
                enum = XrEnum.from_alias(t, self.types[alias]["data"])
                type_info["data"] = enum
                self.enums[enum.name] = enum

            if type_info["category"] == "handle":
                handle = XrHandle.from_alias(t, self.types[alias]["data"])
                handles.append(handle)
                type_info["data"] = handle

            if type_info["category"] == "struct":
                struct = XrStruct.from_alias(t, self.types[alias]["data"])
                structs.append(struct)
                type_info["data"] = struct

            self.types[type_info["name"]] = type_info

        # We need detailed type information during code generation
        # on structs for alignment reasons. Unfortunately structs
        # are parsed among other types, so there is no guarantee
        # that any types needed have been parsed already, so set
        # the data now.
        for struct in structs:
            struct.set_type_info(self.types)

            # Alias structures have enum values equivalent to those of the
            # structure which they are aliased against. we need to ignore alias
            # structs when populating the struct extensions list, otherwise we
            # will create duplicate case entries.
            if struct.alias:
                continue

            for structextend in struct.structextends:
                s = self.types[structextend]["data"]
                s.struct_extensions.append(struct)

            self.mark_struct_dependencies(struct)

        # Guarantee everything is sorted, so code generation doesn't have
        # to deal with this.
        self.base_types = sorted(base_types, key=lambda base_type: base_type.name)
        self.bitmasks = sorted(bitmasks, key=lambda bitmask: bitmask.name)
        self.defines = defines
        self.enums = OrderedDict(sorted(self.enums.items()))
        self.funcpointers = funcpointers
        self.handles = sorted(handles, key=lambda handle: handle.name)
        self.structs = sorted(structs, key=lambda struct: (struct.dep_level, struct.name))

def collect_element_text(e):
    return "".join(e.itertext())

def set_working_directory():
    path = os.path.abspath(__file__)
    path = os.path.dirname(path)
    os.chdir(path)

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("-v", "--verbose", action="count", default=0, help="increase output verbosity")

    args = parser.parse_args()
    if args.verbose == 0:
        LOGGER.setLevel(logging.WARNING)
    elif args.verbose == 1:
        LOGGER.setLevel(logging.INFO)
    else: # > 1
        LOGGER.setLevel(logging.DEBUG)

    set_working_directory()

    xr_xml = "xr.xml".format(XR_XML_VERSION)
    registry = XrRegistry(xr_xml)
    generator = XrGenerator(registry)

    with open(WINE_OPENXR_H, "w") as f:
        generator.generate_openxr_h(f)

    with open(WINE_OPENXR_THUNKS_H, "w") as f:
        generator.generate_thunks_h(f, "wine_")

    with open(WINE_OPENXR_THUNKS_C, "w") as f:
        generator.generate_thunks_c(f, "wine_")

if __name__ == "__main__":
    main()