// Copyright 2015-2023 The Khronos Group Inc.
//
// SPDX-License-Identifier: CC-BY-4.0

[[initialization]]
= Initialization

Before using Vulkan, an application must: initialize it by loading the
Vulkan commands, and creating a sname:VkInstance object.


[[initialization-functionpointers]]
== Command Function Pointers

Vulkan commands are not necessarily exposed by static linking on a platform.
Commands to query function pointers for Vulkan commands are described below.

[NOTE]
.Note
====
When extensions are <<extendingvulkan-compatibility-promotion,promoted>> or
otherwise incorporated into another extension or Vulkan core version,
command <<extendingvulkan-compatibility-aliases,aliases>> may be included.
Whilst the behavior of each command alias is identical, the behavior of
retrieving each alias's function pointer is not.
A function pointer for a given alias can only be retrieved if the extension
or version that introduced that alias is supported and enabled, irrespective
of whether any other alias is available.
====

[open,refpage='vkGetInstanceProcAddr',desc='Return a function pointer for a command',type='protos',xrefs='PFN_vkVoidFunction']
--
Function pointers for all Vulkan commands can: be obtained by calling:

include::{generated}/api/protos/vkGetInstanceProcAddr.adoc[]

  * pname:instance is the instance that the function pointer will be
    compatible with, or `NULL` for commands not dependent on any instance.
  * pname:pName is the name of the command to obtain.

fname:vkGetInstanceProcAddr itself is obtained in a platform- and loader-
specific manner.
Typically, the loader library will export this command as a function symbol,
so applications can: link against the loader library, or load it dynamically
and look up the symbol using platform-specific APIs.

The table below defines the various use cases for
fname:vkGetInstanceProcAddr and expected return value ("`fp`" is "`function
pointer`") for each case.
A valid returned function pointer ("`fp`") must: not be `NULL`.

The returned function pointer is of type tlink:PFN_vkVoidFunction, and must:
be cast to the type of the command being queried before use.

.fname:vkGetInstanceProcAddr behavior
[width="80%",options="header"]
|====
| pname:instance   | pname:pName                                  | return value
| *^1^             | `NULL`                                       | undefined:
| invalid non-`NULL` instance | *^1^                              | undefined:
| `NULL`           | _global command_^2^                          | fp
ifdef::VK_VERSION_1_2[]
| `NULL`           | flink:vkGetInstanceProcAddr                  | fp^5^
endif::VK_VERSION_1_2[]
| instance         | flink:vkGetInstanceProcAddr                  | fp
| instance         | core _dispatchable command_                  | fp^3^
| instance         | enabled instance extension dispatchable command for pname:instance    | fp^3^
| instance         | available device extension^4^ dispatchable command for pname:instance | fp^3^
2+|  any other case, not covered above                            | `NULL`
|====

1::
    "*" means any representable value for the parameter (including valid
    values, invalid values, and `NULL`).

2::
    The global commands are:
ifdef::VK_VERSION_1_1[flink:vkEnumerateInstanceVersion,]
    flink:vkEnumerateInstanceExtensionProperties,
    flink:vkEnumerateInstanceLayerProperties, and flink:vkCreateInstance.
    Dispatchable commands are all other commands which are not global.

3::
    The returned function pointer must: only be called with a dispatchable
    object (the first parameter) that is pname:instance or a child of
    pname:instance, e.g. slink:VkInstance, slink:VkPhysicalDevice,
    slink:VkDevice, slink:VkQueue, or slink:VkCommandBuffer.

4::
    An "`available device extension`" is a device extension supported by any
    physical device enumerated by pname:instance.

ifdef::VK_VERSION_1_2[]
5::
ifndef::VKSC_VERSION_1_0[Starting with Vulkan 1.2, ]
    fname:vkGetInstanceProcAddr can resolve itself with a `NULL` instance
    pointer.
endif::VK_VERSION_1_2[]

include::{generated}/validity/protos/vkGetInstanceProcAddr.adoc[]
--

[open,refpage='vkGetDeviceProcAddr',desc='Return a function pointer for a command',type='protos',xrefs='PFN_vkVoidFunction']
--
In order to support systems with multiple Vulkan implementations, the
function pointers returned by flink:vkGetInstanceProcAddr may: point to
dispatch code that calls a different real implementation for different
slink:VkDevice objects or their child objects.
The overhead of the internal dispatch for slink:VkDevice objects can be
avoided by obtaining device-specific function pointers for any commands that
use a device or device-child object as their dispatchable object.
Such function pointers can: be obtained by calling:

include::{generated}/api/protos/vkGetDeviceProcAddr.adoc[]

The table below defines the various use cases for fname:vkGetDeviceProcAddr
and expected return value ("`fp`" is "`function pointer`") for each case.
A valid returned function pointer ("`fp`") must: not be `NULL`.

The returned function pointer is of type tlink:PFN_vkVoidFunction, and must:
be cast to the type of the command being queried before use.
The function pointer must: only be called with a dispatchable object (the
first parameter) that is pname:device or a child of pname:device.

.fname:vkGetDeviceProcAddr behavior
[width="80%",options="header"]
|====
| pname:device   | pname:pName                      | return value
| `NULL`         | *^1^                             | undefined:
| invalid device | *^1^                             | undefined:
| device         | `NULL`                           | undefined:
| device         | requested core version^2^ device-level dispatchable command^3^ | fp^4^
| device         | enabled extension device-level dispatchable command^3^ | fp^4^
2+| any other case, not covered above               | `NULL`
|====

1::
    "*" means any representable value for the parameter (including valid
    values, invalid values, and `NULL`).

2::
    Device-level commands which are part of the core version specified by
    slink:VkApplicationInfo::pname:apiVersion when creating the instance
    will always return a valid function pointer.
ifndef::VK_KHR_maintenance5[]
    Core commands beyond that version which are supported by the
    implementation may: either return `NULL` or a function pointer.
    If a function pointer is returned, it must: not be called.
endif::VK_KHR_maintenance5[]
ifdef::VK_KHR_maintenance5[]
    If the <<features-maintenance5, pname:maintenance5>> feature is enabled,
    core commands beyond that version which are supported by the
    implementation will return `NULL`, otherwise the implementation may:
    either return `NULL` or a function pointer.
    If a function pointer is returned, it must: not be called.
endif::VK_KHR_maintenance5[]

3::
    In this function, device-level excludes all physical-device-level
    commands.

4::
    The returned function pointer must: only be called with a dispatchable
    object (the first parameter) that is pname:device or a child of
    pname:device e.g. slink:VkDevice, slink:VkQueue, or
    slink:VkCommandBuffer.

include::{generated}/validity/protos/vkGetDeviceProcAddr.adoc[]
--

[open,refpage='PFN_vkVoidFunction',desc='Placeholder function pointer type returned by queries',type='funcpointers',xrefs='vkGetDeviceProcAddr vkGetInstanceProcAddr']
--
The definition of tlink:PFN_vkVoidFunction is:

include::{generated}/api/funcpointers/PFN_vkVoidFunction.adoc[]

This type is returned from command function pointer queries, and must: be
cast to an actual command function pointer before use.
--


ifdef::VK_VERSION_1_1[]
=== Extending Physical Device Core Functionality

New core physical-device-level functionality can: be used when the
physical-device version is greater than or equal to the version of Vulkan
that added the new functionality.
The Vulkan version supported by a physical device can: be obtained by
calling flink:vkGetPhysicalDeviceProperties.
endif::VK_VERSION_1_1[]


ifdef::VK_VERSION_1_1,VK_KHR_get_physical_device_properties2[]
[[initialization-phys-dev-extensions]]
=== Extending Physical Device From Device Extensions

ifdef::VKSC_VERSION_1_0[In Vulkan SC 1.0,]
ifndef::VKSC_VERSION_1_0[]
When the `apiext:VK_KHR_get_physical_device_properties2` extension is
enabled,
ifdef::VK_VERSION_1_1[]
or when both the instance and the physical-device versions are at least 1.1,
endif::VK_VERSION_1_1[]
endif::VKSC_VERSION_1_0[]
physical-device-level functionality of a device extension can: be used with
a physical device if the corresponding extension is enumerated by
flink:vkEnumerateDeviceExtensionProperties for that physical device, even
before a logical device has been created.

To obtain a function pointer for a physical-device-level command from a
device extension, an application can: use flink:vkGetInstanceProcAddr.
This function pointer may: point to dispatch code, which calls a different
real implementation for different sname:VkPhysicalDevice objects.
Applications must: not use a slink:VkPhysicalDevice in any command added by
an extension or core version that is not supported by that physical device.

Device extensions may: define structures that can: be added to the
ptext:pNext chain of physical-device-level commands.
endif::VK_VERSION_1_1,VK_KHR_get_physical_device_properties2[]


[[initialization-instances]]
== Instances

[open,refpage='VkInstance',desc='Opaque handle to an instance object',type='handles']
--
There is no global state in Vulkan and all per-application state is stored
in a sname:VkInstance object.
Creating a sname:VkInstance object initializes the Vulkan library and allows
the application to pass information about itself to the implementation.

Instances are represented by sname:VkInstance handles:

include::{generated}/api/handles/VkInstance.adoc[]
--

ifdef::VK_VERSION_1_1[]
[open,refpage='vkEnumerateInstanceVersion',desc='Query instance-level version before instance creation',type='protos']
--
To query the version of instance-level functionality supported by the
implementation, call:

include::{generated}/api/protos/vkEnumerateInstanceVersion.adoc[]

  * pname:pApiVersion is a pointer to a code:uint32_t, which is the version
    of Vulkan supported by instance-level functionality, encoded as
    described in <<extendingvulkan-coreversions-versionnumbers>>.

[NOTE]
.Note
====
The intended behaviour of flink:vkEnumerateInstanceVersion is that an
implementation should: not need to perform memory allocations and should:
unconditionally return ename:VK_SUCCESS.
The loader, and any enabled layers, may: return
ename:VK_ERROR_OUT_OF_HOST_MEMORY in the case of a failed memory allocation.
====

include::{generated}/validity/protos/vkEnumerateInstanceVersion.adoc[]
--
endif::VK_VERSION_1_1[]

[open,refpage='vkCreateInstance',desc='Create a new Vulkan instance',type='protos']
--
To create an instance object, call:

include::{generated}/api/protos/vkCreateInstance.adoc[]

  * pname:pCreateInfo is a pointer to a slink:VkInstanceCreateInfo structure
    controlling creation of the instance.
  * pname:pAllocator controls host memory allocation as described in the
    <<memory-allocation, Memory Allocation>> chapter.
  * pname:pInstance points a slink:VkInstance handle in which the resulting
    instance is returned.

fname:vkCreateInstance verifies that the requested layers exist.
If not, fname:vkCreateInstance will return ename:VK_ERROR_LAYER_NOT_PRESENT.
Next fname:vkCreateInstance verifies that the requested extensions are
supported (e.g. in the implementation or in any enabled instance layer) and
if any requested extension is not supported, fname:vkCreateInstance must:
return ename:VK_ERROR_EXTENSION_NOT_PRESENT.
After verifying and enabling the instance layers and extensions the
sname:VkInstance object is created and returned to the application.
If a requested extension is only supported by a layer, both the layer and
the extension need to be specified at fname:vkCreateInstance time for the
creation to succeed.

.Valid Usage
****
  * [[VUID-vkCreateInstance-ppEnabledExtensionNames-01388]]
    All <<extendingvulkan-extensions-extensiondependencies, required
    extensions>> for each extension in the
    slink:VkInstanceCreateInfo::pname:ppEnabledExtensionNames list must:
    also be present in that list
****

include::{generated}/validity/protos/vkCreateInstance.adoc[]
--

[open,refpage='VkInstanceCreateInfo',desc='Structure specifying parameters of a newly created instance',type='structs']
--
The sname:VkInstanceCreateInfo structure is defined as:

include::{generated}/api/structs/VkInstanceCreateInfo.adoc[]

  * pname:sType is a elink:VkStructureType value identifying this structure.
  * pname:pNext is `NULL` or a pointer to a structure extending this
    structure.
  * pname:flags is a bitmask of elink:VkInstanceCreateFlagBits indicating
    the behavior of the instance.
  * pname:pApplicationInfo is `NULL` or a pointer to a
    sname:VkApplicationInfo structure.
    If not `NULL`, this information helps implementations recognize behavior
    inherent to classes of applications.
    slink:VkApplicationInfo is defined in detail below.
  * pname:enabledLayerCount is the number of global layers to enable.
  * pname:ppEnabledLayerNames is a pointer to an array of
    pname:enabledLayerCount null-terminated UTF-8 strings containing the
    names of layers to enable for the created instance.
    The layers are loaded in the order they are listed in this array, with
    the first array element being the closest to the application, and the
    last array element being the closest to the driver.
    See the <<extendingvulkan-layers>> section for further details.
  * pname:enabledExtensionCount is the number of global extensions to
    enable.
  * pname:ppEnabledExtensionNames is a pointer to an array of
    pname:enabledExtensionCount null-terminated UTF-8 strings containing the
    names of extensions to enable.

ifdef::VK_EXT_debug_report,VK_EXT_debug_utils[]
To capture events that occur while creating or destroying an instance, an
application can: link a
ifdef::VK_EXT_debug_report[]
slink:VkDebugReportCallbackCreateInfoEXT structure
ifdef::VK_EXT_debug_utils[]
or a
endif::VK_EXT_debug_utils[]
endif::VK_EXT_debug_report[]
ifdef::VK_EXT_debug_utils[]
slink:VkDebugUtilsMessengerCreateInfoEXT structure
endif::VK_EXT_debug_utils[]
to the pname:pNext element of the sname:VkInstanceCreateInfo structure given
to fname:vkCreateInstance.
This callback is only valid for the duration of the flink:vkCreateInstance
and the flink:vkDestroyInstance call.
Use
ifdef::VK_EXT_debug_report[]
flink:vkCreateDebugReportCallbackEXT
ifdef::VK_EXT_debug_utils[]
or
endif::VK_EXT_debug_utils[]
endif::VK_EXT_debug_report[]
ifdef::VK_EXT_debug_utils[]
flink:vkCreateDebugUtilsMessengerEXT
endif::VK_EXT_debug_utils[]
to create persistent callback objects.
endif::VK_EXT_debug_report,VK_EXT_debug_utils[]

ifdef::VK_LUNARG_direct_driver_loading[]
An application can add additional drivers by including the
slink:VkDirectDriverLoadingListLUNARG struct to the pname:pNext element of
the sname:VkInstanceCreateInfo structure given to fname:vkCreateInstance.

[NOTE]
.Note
====
slink:VkDirectDriverLoadingListLUNARG allows applications to ship drivers
with themselves.
Only drivers that are designed to work with it should be used, such as
drivers that implement Vulkan in software or that implement Vulkan by
translating it to a different API.
Any driver that requires installation should not be used, such as hardware
drivers.
====
endif::VK_LUNARG_direct_driver_loading[]

ifdef::VK_EXT_debug_report,VK_EXT_debug_utils,VK_KHR_portability_enumeration,VK_LUNARG_direct_driver_loading[]
.Valid Usage
****
ifdef::VK_EXT_debug_report[]
  * [[VUID-VkInstanceCreateInfo-pNext-04925]]
    If the pname:pNext chain of sname:VkInstanceCreateInfo includes a
    sname:VkDebugReportCallbackCreateInfoEXT structure, the list of enabled
    extensions in pname:ppEnabledExtensionNames must: contain
    `apiext:VK_EXT_debug_report`
endif::VK_EXT_debug_report[]
ifdef::VK_EXT_debug_utils[]
  * [[VUID-VkInstanceCreateInfo-pNext-04926]]
    If the pname:pNext chain of sname:VkInstanceCreateInfo includes a
    sname:VkDebugUtilsMessengerCreateInfoEXT structure, the list of enabled
    extensions in pname:ppEnabledExtensionNames must: contain
    `apiext:VK_EXT_debug_utils`
endif::VK_EXT_debug_utils[]
ifdef::VK_EXT_metal_objects[]
  * [[VUID-VkInstanceCreateInfo-pNext-06779]]
    If the pname:pNext chain includes a
    slink:VkExportMetalObjectCreateInfoEXT structure, its
    pname:exportObjectType member must: be either
    ename:VK_EXPORT_METAL_OBJECT_TYPE_METAL_DEVICE_BIT_EXT or
    ename:VK_EXPORT_METAL_OBJECT_TYPE_METAL_COMMAND_QUEUE_BIT_EXT
endif::VK_EXT_metal_objects[]
ifdef::VK_KHR_portability_enumeration[]
  * [[VUID-VkInstanceCreateInfo-flags-06559]]
    If pname:flags has the
    ename:VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR bit set, the list
    of enabled extensions in pname:ppEnabledExtensionNames must: contain
    `apiext:VK_KHR_portability_enumeration`
endif::VK_KHR_portability_enumeration[]
ifdef::VK_LUNARG_direct_driver_loading[]
  * [[VUID-VkInstanceCreateInfo-pNext-09400]]
    If the pname:pNext chain of sname:VkInstanceCreateInfo includes a
    slink:VkDirectDriverLoadingListLUNARG structure, the list of enabled
    extensions in pname:ppEnabledExtensionNames must: contain
    apiext:VK_LUNARG_direct_driver_loading
endif::VK_LUNARG_direct_driver_loading[]
****
endif::VK_EXT_debug_report,VK_EXT_debug_utils,VK_KHR_portability_enumeration,VK_LUNARG_direct_driver_loading[]

include::{generated}/validity/structs/VkInstanceCreateInfo.adoc[]
--

[open,refpage='VkInstanceCreateFlagBits',desc='Bitmask specifying behavior of the instance',type='enums']
--
include::{generated}/api/enums/VkInstanceCreateFlagBits.adoc[]

ifdef::VK_KHR_portability_enumeration[]
  * ename:VK_INSTANCE_CREATE_ENUMERATE_PORTABILITY_BIT_KHR specifies that
    the instance will enumerate available Vulkan Portability-compliant
    physical devices and groups in addition to the Vulkan physical devices
    and groups that are enumerated by default.
endif::VK_KHR_portability_enumeration[]

ifndef::VK_KHR_portability_enumeration[]
[NOTE]
.Note
====
All bits for this type are defined by extensions, and none of those
extensions are enabled in this build of the specification.
====
endif::VK_KHR_portability_enumeration[]
--

[open,refpage='VkInstanceCreateFlags',desc='Bitmask of VkInstanceCreateFlagBits',type='flags']
--
include::{generated}/api/flags/VkInstanceCreateFlags.adoc[]

ifndef::VK_KHR_portability_enumeration[]
tname:VkInstanceCreateFlags is a bitmask type for setting a mask, but is
currently reserved for future use.
endif::VK_KHR_portability_enumeration[]
ifdef::VK_KHR_portability_enumeration[]
tname:VkInstanceCreateFlags is a bitmask type for setting a mask of zero or
more elink:VkInstanceCreateFlagBits.
endif::VK_KHR_portability_enumeration[]
--

ifdef::VK_EXT_validation_flags[]
include::{chapters}/VK_EXT_validation_flags.adoc[]
endif::VK_EXT_validation_flags[]

ifdef::VK_EXT_validation_features[]
include::{chapters}/VK_EXT_validation_features.adoc[]
endif::VK_EXT_validation_features[]

ifdef::VK_LUNARG_direct_driver_loading[]
[open,refpage='VkDirectDriverLoadingListLUNARG',desc='Structure specifying additional drivers to load',type='structs']
--
The sname:VkDirectDriverLoadingListLUNARG structure is defined as:

include::{generated}/api/structs/VkDirectDriverLoadingListLUNARG.adoc[]

  * pname:sType is a elink:VkStructureType value identifying this structure.
  * pname:pNext is `NULL` or a pointer to a structure extending this
    structure.
  * pname:mode controls the mode in which to load the provided drivers.
  * pname:driverCount is the number of driver manifest paths.
  * pname:pDrivers is a pointer to an array of pname:driverCount
    slink:VkDirectDriverLoadingInfoLUNARG structures.

When creating a Vulkan instance for which additional drivers are to be
included, add a sname:VkDirectDriverLoadingListLUNARG structure to the pNext
chain of the slink:VkInstanceCreateInfo structure, and include in it the
list of sname:VkDirectDriverLoadingInfoLUNARG structures which contain the
information necessary to load additional drivers.

include::{generated}/validity/structs/VkDirectDriverLoadingListLUNARG.adoc[]
--

[open,refpage='VkDirectDriverLoadingInfoLUNARG',desc='Structure specifying the information required to load an additional driver',type='structs']
--
The sname:VkDirectDriverLoadingInfoLUNARG structure is defined as:

include::{generated}/api/structs/VkDirectDriverLoadingInfoLUNARG.adoc[]

  * pname:sType is a elink:VkStructureType value identifying this structure.
  * pname:pNext is `NULL` or a pointer to a structure extending this
    structure.
  * pname:flags is reserved for future use.
  * pname:pfnGetInstanceProcAddr is a tlink:PFN_vkGetInstanceProcAddrLUNARG
    pointer to the driver flink:vkGetInstanceProcAddr function.

include::{generated}/validity/structs/VkDirectDriverLoadingInfoLUNARG.adoc[]
--

[open,refpage='VkDirectDriverLoadingModeLUNARG',desc='Specify loader behavior of added drivers',type='enums']
--
Possible values of slink:VkDirectDriverLoadingListLUNARG::pname:mode,
specifying the mode in which drivers are used, are:

include::{generated}/api/enums/VkDirectDriverLoadingModeLUNARG.adoc[]

  * ename:VK_DIRECT_DRIVER_LOADING_MODE_EXCLUSIVE_LUNARG specifies that the
    provided drivers are used instead of the system-loaded drivers.
  * ename:VK_DIRECT_DRIVER_LOADING_MODE_INCLUSIVE_LUNARG specifies that the
    provided drivers are used in addition to the system-loaded drivers.
--

[open,refpage='VkDirectDriverLoadingFlagsLUNARG',desc='Reserved for future use',type='flags']
--
include::{generated}/api/flags/VkDirectDriverLoadingFlagsLUNARG.adoc[]

tname:VkDirectDriverLoadingFlagsLUNARG is a bitmask type for setting a mask,
but is currently reserved for future use.
--

[open,refpage='PFN_vkGetInstanceProcAddrLUNARG',desc='Type definition for vkGetInstanceProcAddr',type='funcpointers']
--
The type of tlink:PFN_vkGetInstanceProcAddrLUNARG is:

include::{generated}/api/funcpointers/PFN_vkGetInstanceProcAddrLUNARG.adoc[]

  * pname:instance is a slink:VkInstance handle.
  * pname:pName is the name of a Vulkan command.

This type is compatible with the type of a pointer to the
flink:vkGetInstanceProcAddr command, but is used only to specify device
driver addresses in
slink:VkDirectDriverLoadingInfoLUNARG::pname:pfnGetInstanceProcAddr.

[NOTE]
.Note
====
This type exists only because of limitations in the XML schema and
processing scripts, and its name may change in the future.
Ideally we would use the tname:PFN_vkGetInstanceProcAddr type generated in
the `vulkan_core.h` header.
====
--
endif::VK_LUNARG_direct_driver_loading[]

[open,refpage='VkApplicationInfo',desc='Structure specifying application information',type='structs']
--
The sname:VkApplicationInfo structure is defined as:

include::{generated}/api/structs/VkApplicationInfo.adoc[]

  * pname:sType is a elink:VkStructureType value identifying this structure.
  * pname:pNext is `NULL` or a pointer to a structure extending this
    structure.
  * pname:pApplicationName is `NULL` or is a pointer to a null-terminated
    UTF-8 string containing the name of the application.
  * pname:applicationVersion is an unsigned integer variable containing the
    developer-supplied version number of the application.
  * pname:pEngineName is `NULL` or is a pointer to a null-terminated UTF-8
    string containing the name of the engine (if any) used to create the
    application.
  * pname:engineVersion is an unsigned integer variable containing the
    developer-supplied version number of the engine used to create the
    application.
ifndef::VK_VERSION_1_1[]
  * pname:apiVersion is the version of the Vulkan API against which the
    application expects to run, encoded as described in
    <<extendingvulkan-coreversions-versionnumbers>>.
    If pname:apiVersion is 0 the implementation must: ignore it, otherwise
    if the implementation does not support the requested pname:apiVersion,
    or an effective substitute for pname:apiVersion, it must: return
    ename:VK_ERROR_INCOMPATIBLE_DRIVER.
endif::VK_VERSION_1_1[]
ifdef::VK_VERSION_1_1[]
  * pname:apiVersion must: be the highest version of Vulkan that the
    application is designed to use, encoded as described in
    <<extendingvulkan-coreversions-versionnumbers>>.
endif::VK_VERSION_1_1[]
    The patch version number specified in pname:apiVersion is ignored when
    creating an instance object.
    The variant version of the instance must: match that requested in
    pname:apiVersion.

ifdef::VK_VERSION_1_1[]
Vulkan 1.0 implementations were required to return
ename:VK_ERROR_INCOMPATIBLE_DRIVER if pname:apiVersion was larger than 1.0.
Implementations that support Vulkan 1.1 or later must: not return
ename:VK_ERROR_INCOMPATIBLE_DRIVER for any value of pname:apiVersion
ifndef::VKSC_VERSION_1_0[.]
ifdef::VKSC_VERSION_1_0[, unless an incompatible variant is requested.]

ifdef::VKSC_VERSION_1_0[]
[NOTE]
.Note
====
Vulkan SC 1.0 is based on Vulkan 1.2 and thus instance creation may only
fail with ename:VK_ERROR_INCOMPATIBLE_DRIVER if an incompatible variant is
requested - that is if the Vulkan SC API is requested from a Vulkan
implementation or if the Vulkan API is requested from a Vulkan SC
implementation.
====
endif::VKSC_VERSION_1_0[]

ifndef::VKSC_VERSION_1_0[]
[NOTE]
.Note
====
Because Vulkan 1.0 implementations may: fail with
ename:VK_ERROR_INCOMPATIBLE_DRIVER, applications should: determine the
version of Vulkan available before calling flink:vkCreateInstance.
If the flink:vkGetInstanceProcAddr returns `NULL` for
flink:vkEnumerateInstanceVersion, it is a Vulkan 1.0 implementation.
Otherwise, the application can: call flink:vkEnumerateInstanceVersion to
determine the version of Vulkan.
====

As long as the instance supports at least Vulkan 1.1, an application can:
use different versions of Vulkan with an instance than it does with a device
or physical device.

[NOTE]
.Note
====
The Khronos validation layers will treat pname:apiVersion as the highest API
version the application targets, and will validate API usage against the
minimum of that version and the implementation version (instance or device,
depending on context).
If an application tries to use functionality from a greater version than
this, a validation error will be triggered.

For example, if the instance supports Vulkan 1.1 and three physical devices
support Vulkan 1.0, Vulkan 1.1, and Vulkan 1.2, respectively, and if the
application sets pname:apiVersion to 1.2, the application can: use the
following versions of Vulkan:

  * Vulkan 1.0 can: be used with the instance and with all physical devices.
  * Vulkan 1.1 can: be used with the instance and with the physical devices
    that support Vulkan 1.1 and Vulkan 1.2.
  * Vulkan 1.2 can: be used with the physical device that supports Vulkan
    1.2.

If we modify the above example so that the application sets pname:apiVersion
to 1.1, then the application must: not use Vulkan 1.2 functionality on the
physical device that supports Vulkan 1.2.
====
endif::VKSC_VERSION_1_0[]

[NOTE]
.Note
====
Providing a `NULL` slink:VkInstanceCreateInfo::pname:pApplicationInfo or
providing an pname:apiVersion of 0 is equivalent to providing an
pname:apiVersion of
ifndef::VKSC_VERSION_1_0[`VK_MAKE_API_VERSION(0,1,0,0)`.]
ifdef::VKSC_VERSION_1_0[`VK_MAKE_API_VERSION(1,1,0,0)`.]
====
endif::VK_VERSION_1_1[]

ifdef::VK_EXT_application_parameters[]
To provide _application parameters_ at instance creation time, an
application can: link one or more slink:VkApplicationParametersEXT
structures to the pname:pNext chain of the sname:VkApplicationInfo
structure.

If slink:VkApplicationParametersEXT::pname:vendorID does not correspond to
an ICD that is currently available, or if
slink:VkApplicationParametersEXT::pname:deviceID is not `0` and does not
correspond to a physical device that is available on the system,
flink:vkCreateInstance will fail and return
ename:VK_ERROR_INCOMPATIBLE_DRIVER.
If slink:VkApplicationParametersEXT::pname:deviceID is `0`, the application
parameter applies to all physical devices supported by the ICD identified by
slink:VkApplicationParametersEXT::pname:vendorID.

If slink:VkApplicationParametersEXT::pname:key is not a valid
implementation-defined application parameter key for the instance being
created with pname:vendorID, or if pname:value is not a valid value for the
specified pname:key, flink:vkCreateInstance will fail and return
ename:VK_ERROR_INITIALIZATION_FAILED.

For any implementation-defined application parameter pname:key that exists
but is not set by the application, the implementation-specific default value
is used.
endif::VK_EXT_application_parameters[]

.Valid Usage
****
ifndef::VKSC_VERSION_1_0[]
  * [[VUID-VkApplicationInfo-apiVersion-04010]]
    If pname:apiVersion is not `0`, then it must: be greater than or equal
    to dlink:VK_API_VERSION_1_0
endif::VKSC_VERSION_1_0[]
ifdef::VKSC_VERSION_1_0[]
  * [[VUID-VkApplicationInfo-apiVersion-05021]]
    If pname:apiVersion is not `0` and its variant is
    dname:VKSC_API_VARIANT, then it must: be greater than or equal to
    dlink:VKSC_API_VERSION_1_0
endif::VKSC_VERSION_1_0[]
ifdef::VK_EXT_application_parameters[]
  * [[VUID-VkApplicationInfo-key-05093]]
    The pname:key value of each slink:VkApplicationParametersEXT structure
    in the slink:VkApplicationInfo::pname:pNext chain must: be unique for
    each pname:vendorID and pname:deviceID pairing
endif::VK_EXT_application_parameters[]
****

include::{generated}/validity/structs/VkApplicationInfo.adoc[]
--

ifdef::VK_EXT_application_parameters[]
[open,refpage='VkApplicationParametersEXT',desc='Structure specifying application parameters to an instance or device',type='structs']
--
The sname:VkApplicationParametersEXT structure is defined as:

include::{generated}/api/structs/VkApplicationParametersEXT.adoc[]

  * pname:sType is a elink:VkStructureType value identifying this structure.
  * pname:pNext is `NULL` or a pointer to a structure extending this
    structure.
  * pname:vendorID is the slink:VkPhysicalDeviceProperties::pname:vendorID
    of the ICD that the application parameter is applied to.
  * pname:deviceID is `0` or the
    slink:VkPhysicalDeviceProperties::pname:deviceID of the physical device
    that the application parameter is applied to.
  * pname:key is a 32-bit vendor-specific enumerant identifying the
    application parameter that is being set.
  * pname:value is the 64-bit value that is being set for the application
    parameter specified by pname:key.

include::{generated}/validity/structs/VkApplicationParametersEXT.adoc[]
--
endif::VK_EXT_application_parameters[]

[open,refpage='vkDestroyInstance',desc='Destroy an instance of Vulkan',type='protos']
--
To destroy an instance, call:

include::{generated}/api/protos/vkDestroyInstance.adoc[]

  * pname:instance is the handle of the instance to destroy.
  * pname:pAllocator controls host memory allocation as described in the
    <<memory-allocation, Memory Allocation>> chapter.

.Valid Usage
****
  * [[VUID-vkDestroyInstance-instance-00629]]
    All child objects created using pname:instance must: have been destroyed
    prior to destroying pname:instance
ifndef::VKSC_VERSION_1_0[]
  * [[VUID-vkDestroyInstance-instance-00630]]
    If sname:VkAllocationCallbacks were provided when pname:instance was
    created, a compatible set of callbacks must: be provided here
  * [[VUID-vkDestroyInstance-instance-00631]]
    If no sname:VkAllocationCallbacks were provided when pname:instance was
    created, pname:pAllocator must: be `NULL`
endif::VKSC_VERSION_1_0[]
****

include::{generated}/validity/protos/vkDestroyInstance.adoc[]
--
