// Copyright (c) 2015-2016 The Khronos Group Inc. // Copyright notice at https://www.khronos.org/registry/speccopyright.html [[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 // refBegin vkGetInstanceProcAddr Return a function pointer for a command Vulkan commands are not necessarily exposed statically on a platform. Function pointers for all Vulkan commands can: be obtained with the command: include::../protos/vkGetInstanceProcAddr.txt[] * pname:instance is the instance that the function pointer will be compatible with. * 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. Loaders are encouraged to export function symbols for all other core Vulkan commands as well; if this is done, then applications that use only the core Vulkan commands have no need to use fname:vkGetInstanceProcAddr. Function pointers to commands that do not operate on a specific instance can: be obtained by using this command with pname:instance equal to `NULL`. The following commands can: be accessed this way: * flink:vkEnumerateInstanceExtensionProperties * flink:vkEnumerateInstanceLayerProperties * flink:vkCreateInstance The returned function pointer is of type tlink:PFN_vkVoidFunction, and must be cast to the type of the command being queried. If pname:instance is a valid sname:VkInstance, function pointers to any commands that operate on pname:instance or a child of pname:instance can: be obtained. The returned function pointer must: only be called with a dispatchable object (the first parameter) that is a child of pname:instance. If pname:pName is not the name of a core Vulkan command, or is an extension command for any extension not supported by any available layer or implementation, then fname:vkGetInstanceProcAddr will return `NULL`. ifdef::editing-notes[] [NOTE] .editing-note ==== (Jon, Bug 14886 / Gitlab issue 4) The WSI group tentatively agreed that the WSI extensions were special, and should get static entry points in link libraries and prototypes in +vulkan.h+, while future extensions would have to be dynamically loaded. If this decision is upheld by the group as a whole, it would probably be encoded in the previous paragraph, in the WSI extensions branch of the Specification. However, this decision has not been fully signed off on by the entire Vulkan WG yet AFAIK. Note that implementations typically will not support many of the WSI extensions, so ``static entry points'' do not relieve apps of the neccessity of runtime enabling and testing of each extension before using it. ==== endif::editing-notes[] include::../validity/protos/vkGetInstanceProcAddr.txt[] // refEnd vkGetInstanceProcAddr PFN_vkVoidFunction // refBegin vkGetDeviceProcAddr Return a function pointer for a command In order to support systems with multiple Vulkan implementations comprising heterogeneous collections of hardware and software, the function pointers returned by fname:vkGetInstanceProcAddr may: point to dispatch code, which calls a different real implementation for different sname:VkDevice objects (and objects created from them). The overhead of this internal dispatch 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 with the command: include::../protos/vkGetDeviceProcAddr.txt[] * pname:device is the logical device that provides the function pointer. * pname:pName is the name of any Vulkan command whose first parameter is one of ** sname:VkDevice ** sname:VkQueue ** sname:VkCommandBuffer The returned function pointer is of type tlink:PFN_vkVoidFunction, and must be cast to the type of the command being queried. If pname:pName is not the name of one of these Vulkan commands, and is not the name of an extension command belonging to an extension enabled for pname:device, then fname:vkGetDeviceProcAddr will return `NULL`. include::../validity/protos/vkGetDeviceProcAddr.txt[] // refEnd vkGetInstanceProcAddr PFN_vkVoidFunction // refBegin PFN_vkVoidFunction Dummy function pointer type returned by queries The function pointer type returned from the flink:vkGetInstanceProcAddr and flink:vkGetDeviceProcAddr is a dummy type not corresponding to any actual Vulkan function: include::../funcpointers/PFN_vkVoidFunction.txt[] // refEnd PFN_vkVoidFunction vkGetDeviceProcAddr vkGetInstanceProcAddr [[initialization-instances]] == Instances // refBegin VkInstance - Opaque handle to a instance object 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::../handles/VkInstance.txt[] // refEnd VkInstance // refBegin vkCreateInstance Create a new Vulkan instance To create an instance object, call: include::../protos/vkCreateInstance.txt[] * pname:pCreateInfo points to an instance of slink:VkInstanceCreateInfo controlling creation of the instance. * pname:pAllocator controls host memory allocation as described in the <> chapter. * pname:pInstance points a sname:VkInstance handle in which the resulting instance is returned. fname:vkCreateInstance creates the instance, then enables and initializes global layers and extensions requested by the application. If an extension is provided by a layer, both the layer and extension must: be specified at fname:vkCreateInstance time. If a specified layer cannot be found, no sname:VkInstance will be created and the function will return ename:VK_ERROR_LAYER_NOT_PRESENT. Likewise, if a specified extension cannot be found the call will return ename:VK_ERROR_EXTENSION_NOT_PRESENT. include::../validity/protos/vkCreateInstance.txt[] // refBegin VkInstanceCreateInfo - Structure specifying parameters of a newly created instance The sname:VkInstanceCreateInfo structure is defined as: include::../structs/VkInstanceCreateInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:flags is reserved for future use. * pname:pApplicationInfo is `NULL` or a pointer to an instance of sname:VkApplicationInfo. 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. See the <> 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. include::../validity/structs/VkInstanceCreateInfo.txt[] The pname:pApplicationInfo member of slink:VkInstanceCreateInfo can: point to an instance of sname:VkApplicationInfo. // refBegin VkApplicationInfo - Structure specifying application info The sname:VkApplicationInfo structure is defined as: include::../structs/VkApplicationInfo.txt[] * pname:sType is the type of this structure. * pname:pNext is `NULL` or a pointer to an extension-specific structure. * pname:pApplicationName 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 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. * pname:apiVersion is the version of the Vulkan API against which the application expects to run, encoded as described in the <> section. If pname:apiVersion is 0 the implementation must: ignore it, otherwise if the implementation does not support the requested pname:apiVersion it must: return ename:VK_ERROR_INCOMPATIBLE_DRIVER. The patch version number specified in pname:apiVersion is ignored when creating an instance object. Only the major and minor versions of the instance must: match those requested in pname:apiVersion. include::../validity/structs/VkApplicationInfo.txt[] // refBegin vkDestroyInstance Destroy an instance of Vulkan. To destroy an instance, call: include::../protos/vkDestroyInstance.txt[] * pname:instance is the handle of the instance to destroy. * pname:pAllocator controls host memory allocation as described in the <> chapter. include::../validity/protos/vkDestroyInstance.txt[]