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e2d981c029
* Bump API patch number and header version number to 20 for this
update.
Github Issues:
* Replaced existing reference pages by text automatically extracted
from the specification source, or generated from vk.xml in some
cases. This isn't a complete solution for the reference pages, but
puts them in a much better state. The ref pages (only) are now
placed under a CC BY open source license, which is more current than
the obsolete license previously used.
Further improvements to the pages should not edit them directly, but
instead concentrate on the specification source from which the ref
pages are being extracted (public issues 44, 55, 160; internal issue
389).
228 lines
9.5 KiB
Plaintext
228 lines
9.5 KiB
Plaintext
// Copyright (c) 2015-2016 The Khronos Group Inc.
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// Copyright notice at https://www.khronos.org/registry/speccopyright.html
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[[initialization]]
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= Initialization
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Before using Vulkan, an application must: initialize it by loading the
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Vulkan commands, and creating a sname:VkInstance object.
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[[initialization-functionpointers]]
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== Command Function Pointers
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// refBegin vkGetInstanceProcAddr Return a function pointer for a command
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Vulkan commands are not necessarily exposed statically on a platform.
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Function pointers for all Vulkan commands can: be obtained with the
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command:
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include::../protos/vkGetInstanceProcAddr.txt[]
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* pname:instance is the instance that the function pointer will be
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compatible with.
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* pname:pName is the name of the command to obtain.
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fname:vkGetInstanceProcAddr itself is obtained in a platform- and loader-
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specific manner. Typically, the loader library will export this command as a
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function symbol, so applications can: link against the loader library, or
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load it dynamically and look up the symbol using platform-specific APIs.
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Loaders are encouraged to export function symbols for all other core
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Vulkan commands as well; if this is done, then applications that use only
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the core Vulkan commands have no need to use fname:vkGetInstanceProcAddr.
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Function pointers to commands that do not operate on a specific instance can:
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be obtained by using this command with pname:instance equal to `NULL`. The
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following commands can: be accessed this way:
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* flink:vkEnumerateInstanceExtensionProperties
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* flink:vkEnumerateInstanceLayerProperties
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* flink:vkCreateInstance
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The returned function pointer is of type tlink:PFN_vkVoidFunction, and must
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be cast to the type of the command being queried.
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If pname:instance is a valid sname:VkInstance, function pointers to any
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commands that operate on pname:instance or a child of pname:instance can: be
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obtained. The returned function pointer must: only be called with a
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dispatchable object (the first parameter) that is a child of pname:instance.
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If pname:pName is not the name of a core Vulkan command, or is an
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extension command for any extension not supported by any available layer or
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implementation, then fname:vkGetInstanceProcAddr will return `NULL`.
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ifdef::editing-notes[]
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[NOTE]
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.editing-note
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====
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(Jon, Bug 14886 / Gitlab issue 4) The WSI group tentatively agreed that the
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WSI extensions were special, and should get static entry points in link
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libraries and prototypes in +vulkan.h+, while future extensions would have
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to be dynamically loaded. If this decision is upheld by the group as a
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whole, it would probably be encoded in the previous paragraph, in the WSI
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extensions branch of the Specification.
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However, this decision has not been fully signed off on by the entire Vulkan
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WG yet AFAIK. Note that implementations typically will not support many of the
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WSI extensions, so ``static entry points'' do not relieve apps of the
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neccessity of runtime enabling and testing of each extension before using
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it.
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====
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endif::editing-notes[]
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include::../validity/protos/vkGetInstanceProcAddr.txt[]
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// refEnd vkGetInstanceProcAddr PFN_vkVoidFunction
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// refBegin vkGetDeviceProcAddr Return a function pointer for a command
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In order to support systems with multiple Vulkan implementations
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comprising heterogeneous collections of hardware and software, the function
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pointers returned by fname:vkGetInstanceProcAddr may: point to dispatch
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code, which calls a different real implementation for different
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sname:VkDevice objects (and objects created from them). The overhead of this
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internal dispatch can: be avoided by obtaining device-specific function
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pointers for any commands that use a device or device-child object as their
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dispatchable object. Such function pointers can: be obtained with the
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command:
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include::../protos/vkGetDeviceProcAddr.txt[]
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* pname:device is the logical device that provides the function pointer.
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* pname:pName is the name of any Vulkan command whose first parameter
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is one of
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** sname:VkDevice
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** sname:VkQueue
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** sname:VkCommandBuffer
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The returned function pointer is of type tlink:PFN_vkVoidFunction, and must
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be cast to the type of the command being queried.
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If pname:pName is not the name of one of these Vulkan commands, and is
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not the name of an extension command belonging to an extension enabled for
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pname:device, then fname:vkGetDeviceProcAddr will return `NULL`.
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include::../validity/protos/vkGetDeviceProcAddr.txt[]
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// refEnd vkGetInstanceProcAddr PFN_vkVoidFunction
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// refBegin PFN_vkVoidFunction Dummy function pointer type returned by queries
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The function pointer type returned from the flink:vkGetInstanceProcAddr and
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flink:vkGetDeviceProcAddr is a dummy type not corresponding to any actual
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Vulkan function:
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include::../funcpointers/PFN_vkVoidFunction.txt[]
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// refEnd PFN_vkVoidFunction vkGetDeviceProcAddr vkGetInstanceProcAddr
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[[initialization-instances]]
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== Instances
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// refBegin VkInstance - Opaque handle to a instance object
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There is no global state in Vulkan and all per-application state is
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stored in a sname:VkInstance object. Creating a sname:VkInstance object
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initializes the Vulkan library and allows the application to pass
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information about itself to the implementation.
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Instances are represented by sname:VkInstance handles:
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include::../handles/VkInstance.txt[]
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// refEnd VkInstance
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// refBegin vkCreateInstance Create a new Vulkan instance
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To create an instance object, call:
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include::../protos/vkCreateInstance.txt[]
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* pname:pCreateInfo points to an instance of slink:VkInstanceCreateInfo
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controlling creation of the instance.
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* pname:pAllocator controls host memory allocation as described in the
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<<memory-allocation, Memory Allocation>> chapter.
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* pname:pInstance points a sname:VkInstance handle in which the resulting
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instance is returned.
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fname:vkCreateInstance creates the instance, then enables and initializes
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global layers and extensions requested by the application. If an extension
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is provided by a layer, both the layer and extension must: be specified at
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fname:vkCreateInstance time. If a specified layer cannot be found, no
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sname:VkInstance will be created and the function will return
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ename:VK_ERROR_LAYER_NOT_PRESENT. Likewise, if a specified extension cannot
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be found the call will return ename:VK_ERROR_EXTENSION_NOT_PRESENT.
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include::../validity/protos/vkCreateInstance.txt[]
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// refBegin VkInstanceCreateInfo - Structure specifying parameters of a newly created instance
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The sname:VkInstanceCreateInfo structure is defined as:
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include::../structs/VkInstanceCreateInfo.txt[]
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* pname:sType is the type of this structure.
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* pname:pNext is `NULL` or a pointer to an extension-specific structure.
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* pname:flags is reserved for future use.
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* pname:pApplicationInfo is `NULL` or a pointer to an instance of
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sname:VkApplicationInfo. If not `NULL`, this information helps
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implementations recognize behavior inherent to classes of applications.
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slink:VkApplicationInfo is defined in detail below.
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* pname:enabledLayerCount is the number of global layers to enable.
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* pname:ppEnabledLayerNames is a pointer to an array of
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pname:enabledLayerCount null-terminated UTF-8 strings containing the
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names of layers to enable for the created instance. See the
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<<extended-functionality-layers,Layers>> section for further details.
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* pname:enabledExtensionCount is the number of global extensions to
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enable.
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* pname:ppEnabledExtensionNames is a pointer to an array of
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pname:enabledExtensionCount null-terminated UTF-8 strings containing the
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names of extensions to enable.
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include::../validity/structs/VkInstanceCreateInfo.txt[]
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The pname:pApplicationInfo member of slink:VkInstanceCreateInfo can: point
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to an instance of sname:VkApplicationInfo.
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// refBegin VkApplicationInfo - Structure specifying application info
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The sname:VkApplicationInfo structure is defined as:
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include::../structs/VkApplicationInfo.txt[]
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* pname:sType is the type of this structure.
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* pname:pNext is `NULL` or a pointer to an extension-specific structure.
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* pname:pApplicationName is a pointer to a null-terminated UTF-8 string
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containing the name of the application.
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* pname:applicationVersion is an unsigned integer variable containing the
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developer-supplied version number of the application.
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* pname:pEngineName is a pointer to a null-terminated UTF-8 string
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containing the name of the engine (if any) used to create the
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application.
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* pname:engineVersion is an unsigned integer variable containing the
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developer-supplied version number of the engine used to create the
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application.
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* pname:apiVersion is the version of the Vulkan API against which the
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application expects to run, encoded as described in the
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<<fundamentals-versionnum,API Version Numbers and Semantics>> section.
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If pname:apiVersion is 0 the implementation must: ignore it, otherwise
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if the implementation does not support the requested pname:apiVersion it
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must: return ename:VK_ERROR_INCOMPATIBLE_DRIVER. The patch version number
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specified in pname:apiVersion is ignored when creating an instance
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object. Only the major and minor versions of the instance must: match
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those requested in pname:apiVersion.
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include::../validity/structs/VkApplicationInfo.txt[]
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// refBegin vkDestroyInstance Destroy an instance of Vulkan.
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To destroy an instance, call:
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include::../protos/vkDestroyInstance.txt[]
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* pname:instance is the handle of the instance to destroy.
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* pname:pAllocator controls host memory allocation as described in the
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<<memory-allocation, Memory Allocation>> chapter.
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include::../validity/protos/vkDestroyInstance.txt[]
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