glfw/docs/vulkan.dox

/*!

@page vulkan Vulkan guide
 
@tableofcontents

This guide is intended to fill the gaps between the [Vulkan
documentation](https://www.khronos.org/vulkan/) and the rest of the GLFW
documentation and is not a replacement for either.  It assumes some familiarity
with Vulkan concepts like loaders, devices, queues and surfaces.

To develop for Vulkan you should install an SDK for your platform, for example
the [LunarG Vulkan SDK](https://vulkan.lunarg.com/).  Apart from the headers and
libraries, it also provides the validation layers necessary for development.

The GLFW library does not need the Vulkan SDK to enable support for Vulkan.
However, any Vulkan-specific test and example programs are built only if the
CMake files find a Vulkan SDK.


@section vulkan_include Including the Vulkan and GLFW header files

To include the Vulkan header, define [GLFW_INCLUDE_VULKAN](@ref build_macros)
before including the GLFW header.

@code
#define GLFW_INCLUDE_VULKAN
#include <GLFW/glfw3.h>
@endcode

If you want to include the Vulkan header from a custom location or use your own
custom Vulkan header then you need to include them before the GLFW header.

@code
#include <path/to/vulkan.h>
#include <GLFW/glfw3.h>
@endcode

Unless a Vulkan header is included, either by the GLFW header or above it, any
GLFW functions that take or return Vulkan types will not be declared.

The `VK_USE_PLATFORM_*_KHR` macros do not need to be defined for the Vulkan part
of GLFW to work.  Define them only if you are using these extensions directly.


@section vulkan_support Querying for Vulkan support

If you are linking directly against the Vulkan loader then you can skip this
section.  The canonical desktop loader library exports all Vulkan core and
Khronos extension functions, allowing them to be called directly.

If you are loading the Vulkan loader dynamically instead of linking directly
against it, you can check for the availability of a loader with @ref
glfwVulkanSupported.

@code
if (glfwVulkanSupported())
{
    // Vulkan is available, at least for compute
}
@endcode

This function returns `GLFW_TRUE` if the Vulkan loader was found.  This check is
performed by @ref glfwInit.

If no loader was found, calling any other Vulkan related GLFW function will
generate a @ref GLFW_API_UNAVAILABLE error.


@subsection vulkan_proc Querying Vulkan function pointers

To load any Vulkan core or extension function from the found loader, call @ref
glfwGetInstanceProcAddress.  To load functions needed for instance creation,
pass `NULL` as the instance.

@code
PFN_vkCreateInstance pfnCreateInstance = (PFN_vkCreateInstance)
    glfwGetInstanceProcAddress(NULL, "vkCreateInstance");
@endcode

Once you have created an instance, you can load from it all other Vulkan core
functions and functions from any instance extensions you enabled.

@code
PFN_vkCreateDevice pfnCreateDevice = (PFN_vkCreateDevice)
    glfwGetInstanceProcAddress(instance, "vkCreateDevice");
@endcode

This function in turn calls `vkGetInstanceProcAddr`.  If that fails, the
function falls back to a platform-specific query of the Vulkan loader (i.e.
`dlsym` or `GetProcAddress`).  If that also fails, the function returns `NULL`.
For more information about `vkGetInstanceProcAddr`, see the Vulkan
documentation.

Vulkan also provides `vkGetDeviceProcAddr` for loading device-specific versions
of Vulkan function.  This function can be retrieved from an instance with @ref
glfwGetInstanceProcAddress.

@code
PFN_vkGetDeviceProcAddr pfnGetDeviceProcAddr = (PFN_vkGetDeviceProcAddr)
    glfwGetInstanceProcAddress(instance, "vkGetDeviceProcAddr");
@endcode

Device-specific functions may execute a little bit faster, due to not having to
dispatch internally based on the device passed to them.  For more information
about `vkGetDeviceProcAddr`, see the Vulkan documentation.


@section vulkan_ext Querying required Vulkan extensions

To do anything useful with Vulkan you need to create an instance.  If you want
to use Vulkan to render to a window, you must enable the instance extensions
GLFW requires to create Vulkan surfaces.

To query the instance extensions required, call @ref
glfwGetRequiredInstanceExtensions.

@code
int count;
const char** extensions = glfwGetRequiredInstanceExtensions(&count);
@endcode

These extensions must all be enabled when creating instances that are going to
be passed to @ref glfwGetPhysicalDevicePresentationSupport and @ref
glfwCreateWindowSurface.  The set of extensions will vary depending on platform
and may also vary depending on graphics drivers and other factors.

If it fails it will return `NULL` and GLFW will not be able to create Vulkan
window surfaces.  You can still use Vulkan for off-screen rendering and compute
work.

The returned array will always contain `VK_KHR_surface`, so if you don't
require any additional extensions you can pass this list directly to the
`VkInstanceCreateInfo` struct.

@code
VkInstanceCreateInfo ici;

memset(&ici, 0, sizeof(ici));
ici.enabledExtensionCount = count;
ici.ppEnabledExtensionNames = extensions;
...
@endcode

Additional extensions may be required by future versions of GLFW.  You should
check whether any extensions you wish to enable are already in the returned
array, as it is an error to specify an extension more than once in the
`VkInstanceCreateInfo` struct. 


@section vulkan_present Querying for Vulkan presentation support

Not every queue family of every Vulkan device can present images to surfaces.
To check whether a specific queue family of a physical device supports image
presentation without first having to create a window and surface, call @ref
glfwGetPhysicalDevicePresentationSupport.

@code
if (glfwGetPhysicalDevicePresentationSupport(instance, physical_device, queue_family_index))
{
    // Queue family supports image presentation
}
@endcode

The `VK_KHR_surface` extension additionally provides the 
`vkGetPhysicalDeviceSurfaceSupportKHR` function, which performs the same test on
an existing Vulkan surface.


@section vulkan_window Creating the window

Unless you will be using OpenGL or OpenGL ES with the same window as Vulkan,
there is no need to create a context.  You can disable context creation by
setting the [GLFW_CLIENT_API](@ref window_hints_ctx) hint to `GLFW_NO_API`.

@code
glfwWindowHint(GLFW_CLIENT_API, GLFW_NO_API);
GLFWwindow* window = glfwCreateWindow(640, 480, "Window Title", NULL, NULL);
@endcode

See @ref context_less for more information.


@section vulkan_surface Creating a Vulkan window surface

You can create a Vulkan surface (as defined by the `VK_KHR_surface` extension)
for a GLFW window with @ref glfwCreateWindowSurface.

@code
VkSurfaceKHR surface;
VkResult err = glfwCreateWindowSurface(instance, window, NULL, &surface);
if (err)
{
    // Window surface creation failed
}
@endcode

It is your responsibility to destroy the surface.  GLFW does not destroy it for
you.  Call `vkDestroySurfaceKHR` function from the same extension to destroy it.

*/