glfw/docs/vulkan.dox

/*!

@page vulkan_guide 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 and leaves it to
the Vulkan documentation to explain the details of Vulkan functions.

To develop for Vulkan you should install an SDK for your platform, for example
the [LunarG Vulkan SDK](https://vulkan.lunarg.com/) for Windows and Linux or
[MoltenVK](https://moltengl.com/moltenvk/) for macOS.  Apart from headers and
link libraries, they should also provide 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.

@macos Because MoltenVK is typically not installed system-wide, you will need to
point CMake to it using the `CMAKE_FRAMEWORK_PATH` variable when configuring the
GLFW source tree.  Set this variable to the `MoltenVK/macOS` subdirectory of the
SDK, either on the command-line or in the CMake GUI.

For details on a specific function in this category, see the @ref vulkan.  There
are also guides for the other areas of the GLFW API.

 - @ref intro_guide
 - @ref window_guide
 - @ref context_guide
 - @ref monitor_guide
 - @ref input_guide


@section vulkan_loader Linking against the Vulkan loader

By default, GLFW will look for the Vulkan loader on demand at runtime via its
standard name (`vulkan-1.dll` on Windows, `libvulkan.so.1` on Linux and other
Unix-like systems and `libMoltenVK.dylib` on macOS).  This means that GLFW does
not need to be linked against the loader.  However, it also means that if you
are using the static library form of the Vulkan loader GLFW will either fail to
find it or (worse) use the wrong one.

The @ref GLFW_VULKAN_STATIC CMake option makes GLFW link directly against the
static library form.  Not linking against the Vulkan loader will then be
a compile-time error.

@macos When using the static library form of MoltenVK (i.e. `MetalVK.framework`
and not `libMoltenVK.dylib`) you must also link against its dependencies: the
`Cocoa`, `Metal` and `QuartzCore` system frameworks and the `libc++` library.


@section vulkan_include Including the Vulkan and GLFW header files

To include the Vulkan header, define @ref GLFW_INCLUDE_VULKAN before including
the GLFW header.

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

If you instead want to include the Vulkan header from a custom location or use
your own custom Vulkan header then do this 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 and ICD with @ref
glfwVulkanSupported.

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

This function returns `GLFW_TRUE` if the Vulkan loader and any minimally
functional ICD was found.

If if one or both were not 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
uint32_t 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 with the
[GLFW_CLIENT_API](@ref GLFW_CLIENT_API_hint) hint.

@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

If an OpenGL or OpenGL ES context was created on the window, the context has
ownership of the presentation on the window and a Vulkan surface cannot be
created.

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.

*/