A Vulkan binding generator for Zig.
vulkan-zig attempts to provide a better experience to programming Vulkan applications in Zig, by providing features such as integration of vulkan errors with Zig's error system, function pointer loading, renaming fields to standard Zig style, better bitfield handling, turning out parameters into return values and more.
vulkan-zig is automatically tested daily against the latest vk.xml and zig, and supports vk.xml from version 1.x.163.
vulkan-zig aims to be always compatible with the ever-changing Zig master branch (however, development may lag a few days behind). Sometimes, the Zig master branch breaks a bunch of functionality however, which may make the latest version vulkan-zig incompatible with older releases of Zig. This repository aims to have a version compatible for both the latest Zig master, and the latest Zig release. The master
branch is compatible with the master
branch of Zig, and versions for older versions of Zig are maintained in the zig-<version>-compat
branch.
A CLI-interface is provided to generate vk.zig from the Vulkan XML registry, which is built by default when invoking zig build
in the project root. To generate vk.zig, simply invoke the program as follows:
$ zig-cache/bin/vulkan-zig-generator path/to/vk.xml output/path/to/vk.zig
This reads the xml file, parses its contents, renders the Vulkan bindings, and formats file, before writing the result to the output path. While the intended usage of vulkan-zig is through direct generation from build.zig (see below), the CLI-interface can be used for one-off generation and vendoring the result.
Vulkan bindings can be generated from the Vulkan XML registry at compile time with build.zig, by using the provided Vulkan generation step:
const vkgen = @import("vulkan-zig/generator/index.zig");
pub fn build(b: *Builder) void {
...
const exe = b.addExecutable("my-executable", "src/main.zig");
// Create a step that generates vk.zig (stored in zig-cache) from the provided vulkan registry.
const gen = vkgen.VkGenerateStep.init(b, "path/to/vk.xml", "vk.zig");
// Add the generated file as package to the final executable
exe.addPackage(gen.package);
}
This reads vk.xml, parses its contents, and renders the Vulkan bindings to "vk.zig", which is then formatted and placed in zig-cache
. The resulting file can then be added to an executable by using addPackage
, after which the bindings will be made available to the executable under the name vulkan
.
Functions and fields are renamed to be more or less in line with Zig's standard library style:
- The vk prefix is removed everywhere
- Structs like
VkInstanceCreateInfo
are renamed toInstanceCreateInfo
. - Handles like
VkSwapchainKHR
are renamed toSwapchainKHR
(note that the tag is retained in caps). - Functions like
vkCreateInstance
are generated ascreateInstance
as wrapper and asPfnCreateInstance
as function pointer. - API constants like
VK_WHOLE_SIZE
retain screaming snake case, and are generates asWHOLE_SIZE
.
- Structs like
- The type name is stripped from enumeration fields and bitflags, and they are generated in (lower) snake case. For example,
VK_IMAGE_LAYOUT_GENERAL
is generated as justgeneral
. Note that author tags are also generated to lower case:VK_SURFACE_TRANSFORM_FLAGS_IDENTITY_BIT_KHR
is translated toidentity_bit_khr
. - Container fields and function parameter names are generated in (lower) snake case in a similar manner:
ppEnabledLayerNames
becomespp_enabled_layer_names
. - Any name which is either an illegal Zig name or a reserved identifier is rendered using
@"name"
syntax. For example,VK_IMAGE_TYPE_2D
is translated to@"2d"
.
vulkan-zig provides no integration for statically linking libvulkan, and these symbols are not generated at all. Instead, vulkan functions are to be loaded dynamically. For each Vulkan function, a function pointer type is generated using the exact parameters and return types as defined by the Vulkan specification:
pub const PfnCreateInstance = fn (
p_create_info: *const InstanceCreateInfo,
p_allocator: ?*const AllocationCallbacks,
p_instance: *Instance,
) callconv(vulkan_call_conv) Result;
For each function, a wrapper is generated into one of three structs:
- BaseWrapper. This contains wrappers for functions which are loaded by
vkGetInstanceProcAddr
without an instance, such asvkCreateInstance
,vkEnumerateInstanceVersion
, etc. - InstanceWrapper. This contains wrappers for functions which are otherwise loaded by
vkGetInstanceProcAddr
. - DeviceWrapper. This contains wrappers for functions which are loaded by
vkGetDeviceProcAddr
.
Each wrapper struct can be called with an array of the appropriate enums:
const vk = @import("vulkan");
const BaseDispatch = vk.BaseWrapper(.{
.CreateInstance,
});
The wrapper struct then provides wrapper functions for each function pointer in the dispatch struct:
pub const BaseWrapper(comptime cmds: anytype) type {
...
const Dispatch = CreateDispatchStruct(cmds);
return struct {
dispatch: Dispatch,
pub const CreateInstanceError = error{
OutOfHostMemory,
OutOfDeviceMemory,
InitializationFailed,
LayerNotPresent,
ExtensionNotPresent,
IncompatibleDriver,
Unknown,
};
pub fn createInstance(
self: Self,
create_info: InstanceCreateInfo,
p_allocator: ?*const AllocationCallbacks,
) CreateInstanceError!Instance {
var instance: Instance = undefined;
const result = self.dispatch.vkCreateInstance(
&create_info,
p_allocator,
&instance,
);
switch (result) {
.success => {},
.error_out_of_host_memory => return error.OutOfHostMemory,
.error_out_of_device_memory => return error.OutOfDeviceMemory,
.error_initialization_failed => return error.InitializationFailed,
.error_layer_not_present => return error.LayerNotPresent,
.error_extension_not_present => return error.ExtensionNotPresent,
.error_incompatible_driver => return error.IncompatibleDriver,
else => return error.Unknown,
}
return instance;
}
...
}
}
Wrappers are generated according to the following rules:
- The return type is determined from the original return type and the parameters.
- Any non-const, non-optional single-item pointer is interpreted as an out parameter.
- If a command returns a non-error
VkResult
other thanVK_SUCCESS
it is also returned. - If there are multiple return values selected, an additional struct is generated. The original call's return value is called
return_value
,VkResult
is namedresult
, and the out parameters are called the same exceptp_
is removed. They are generated in this order.
- Any const non-optional single-item pointer is interpreted as an in-parameter. For these, one level of indirection is removed so that create info structure pointers can now be passed as values, enabling the ability to use struct literals for these parameters.
- Error codes are translated into Zig errors.
- As of yet, there is no specific handling of enumeration style commands or other commands which accept slices.
Furthermore, each wrapper contains a function to load each function pointer member when passed either PfnGetInstanceProcAddr
or PfnGetDeviceProcAddr
, which attempts to load each member as function pointer and casts it to the appropriate type. These functions are loaded literally, and any wrongly named member or member with a wrong function pointer type will result in problems.
- For
BaseWrapper
, this function has signaturefn load(loader: anytype) error{CommandFailure}!Self
, where the type ofloader
must resemblePfnGetInstanceProcAddr
(with optionally having a different calling convention). - For
InstanceWrapper
, this function has signaturefn load(instance: Instance, loader: anytype) error{CommandFailure}!Self
, where the type ofloader
must resemblePfnGetInstanceProcAddr
. - For
DeviceWrapper
, this function has signaturefn load(device: Device, loader: anytype) error{CommandFailure}!Self
, where the type ofloader
must resemblePfnGetDeviceProcAddr
.
Note that these functions accepts a loader with the signature of anytype
instead of PfnGetInstanceProcAddr
. This is because it is valid for vkGetInstanceProcAddr
to load itself, in which case the returned function is to be called with the vulkan calling convention. This calling convention is not required for loading vulkan-zig itself, though, and a loader to be called with any calling convention with the target architecture may be passed in. This is particularly useful when interacting with C libraries that provide vkGetInstanceProcAddr
.
// vkGetInstanceProcAddr as provided by GLFW.
// Note that vk.Instance and vk.PfnVoidFunction are ABI compatible with VkInstance,
// and that `extern` implies the C calling convention.
pub extern fn glfwGetInstanceProcAddress(instance: vk.Instance, procname: [*:0]const u8) vk.PfnVoidFunction;
// Or provide a custom implementation.
// This function is called with the unspecified Zig-internal calling convention.
fn customGetInstanceProcAddress(instance: vk.Instance, procname: [*:0]const u8) vk.PfnVoidFunction {
...
}
// Both calls are valid, even
const vkb = try BaseDispatch.load(glfwGetInstanceProcAddress);
const vkb = try BaseDispatch.load(customGetInstanceProcAddress);
By default, wrapper load
functions return error.CommandLoadFailure
if a call to the loader resulted in null
. If this behaviour is not desired, one can use loadNoFail
. This function accepts the same parameters as load
, but does not return an error any function pointer fails to load and sets its value to undefined
instead. It is at the programmer's discretion not to invoke invalid functions, which can be tested for by checking whether the required core and extension versions the function requires are supported.
One can access the underlying unwrapped C functions by doing wrapper.dispatch.vkFuncYouWant(..)
.
Packed structs of bools are used for bit flags in vulkan-zig, instead of both a FlagBits
and Flags
variant. Places where either of these variants are used are both replaced by this packed struct instead. This means that even in places where just one flag would normally be accepted, the packed struct is accepted. The programmer is responsible for only enabling a single bit.
Each bit is defaulted to false
, and the first bool
is aligned to guarantee the overal alignment
of each Flags type to guarantee ABI compatibility when passing bitfields through structs:
pub const QueueFlags = packed struct {
graphics_bit: bool align(@alignOf(Flags)) = false,
compute_bit: bool = false,
transfer_bit: bool = false,
sparse_binding_bit: bool = false,
protected_bit: bool = false,
_reserved_bit_5: bool = false,
_reserved_bit_6: bool = false,
...
}
Note that on function call ABI boundaries, this alignment trick is not sufficient. Instead, the flags
are reinterpreted as an integer which is passed instead. Each flags type is augmented by a mixin which provides IntType
, an integer which represents the flags on function ABI boundaries. This mixin also provides some common set operation on bitflags:
pub fn FlagsMixin(comptime FlagsType: type) type {
return struct {
pub const IntType = Flags;
// Return the integer representation of these flags
pub fn toInt(self: FlagsType) IntType {...}
// Turn an integer representation back into a flags type
pub fn fromInt(flags: IntType) FlagsType { ... }
// Return the set-union of `lhs` and `rhs.
pub fn merge(lhs: FlagsType, rhs: FlagsType) FlagsType { ... }
// Return the set-intersection of `lhs` and `rhs`.
pub fn intersect(lhs: FlagsType, rhs: FlagsType) FlagsType { ... }
// Return the set-complement of `lhs` and `rhs`. Note: this also inverses reserved bits.
pub fn complement(self: FlagsType) FlagsType { ... }
// Return the set-subtraction of `lhs` and `rhs`: All fields set in `rhs` are cleared in `lhs`.
pub fn subtract(lhs: FlagsType, rhs: FlagsType) FlagsType { ... }
// Returns whether all bits set in `rhs` are also set in `lhs`.
pub fn contains(lhs: FlagsType, rhs: FlagsType) bool { ... }
};
}
Handles are generated to a non-exhaustive enum, backed by a u64
for non-dispatchable handles and usize
for dispatchable ones:
const Instance = extern enum(usize) { null_handle = 0, _ };
This means that handles are type-safe even when compiling for a 32-bit target.
Defaults are generated for certain fields of structs:
- sType is defaulted to the appropriate value.
- pNext is defaulted to
null
. - No other fields have default values.
pub const InstanceCreateInfo = extern struct {
s_type: StructureType = .instance_create_info,
p_next: ?*const anyopaque = null,
flags: InstanceCreateFlags,
...
};
Pointer types in both commands (wrapped and function pointers) and struct fields are augmented with the following information, where available in the registry:
- Pointer optional-ness.
- Pointer const-ness.
- Pointer size: Either single-item, null-terminated or many-items.
Note that this information is not everywhere as useful in the registry, leading to places where optional-ness is not correct. Most notably, CreateInfo type structures which take a slice often have the item count marked as optional, but the pointer itself not. As of yet, this is not fixed in vulkan-zig. If drivers properly follow the Vulkan specification, these can be initialized to undefined
, however, that is not always the case.
Defaults with the same ABI layout are generated for most platform-defined types. These can either by bitcasted to, or overridden by defining them in the project root:
pub const xcb_connection_t = if (@hasDecl(root, "xcb_connection_t")) root.xcb_connection_t else @Type(.Opaque);
For some times (such as those from Google Games Platform) no default is known. Usage of these without providing a concrete type in the project root generates a compile error.
vulkan-zig provides functionality to help compiling shaders using glslc. It can be used from build.zig as follows:
const vkgen = @import("vulkan-zig/generator/index.zig");
pub fn build(b: *Builder) void {
...
const exe = b.addExecutable("my-executable", "src/main.zig");
const gen = vkgen.VkGenerateStep(b, "path/to/vk.xml", "vk.zig");
exe.addPackage(gen.package);
const shader_comp = vkgen.ShaderCompileStep.init(
builder,
&[_][]const u8{"glslc", "--target-env=vulkan1.2"}, // Path to glslc and additional parameters
);
exe.step.dependOn(&shader_comp.step);
const spv_path = shader_comp.addShader("path/to/shader.frag");
}
Upon compilation, glslc is then invoked to compile each shader, and the result is placed within zig-cache
. addShader
returns the full path to the compiled shader code. This file can then be included in the project, as is done in build.zig for the example by generating an additional file which uses @embedFile
.
-
Currently, the self-hosted version of Zig's cache-hash API is not yet ready for usage, which means that the bindings are regenerated every time an executable is built.
-
vulkan-zig has as of yet no functionality for selecting feature levels and extensions when generating bindings. This is because when an extension is promoted to Vulkan core, its fields and commands are renamed to lose the extensions author tag (for example, VkSemaphoreWaitFlagsKHR was renamed to VkSemaphoreWaitFlags when it was promoted from an extension to Vulkan 1.2 core). This leads to inconsistencies when only items from up to a certain feature level is included, as these promoted items then need to re-gain a tag.
A partial implementation of https://vulkan-tutorial.org is implemented in examples/triangle.zig. This example can be ran by executing zig build run-triangle
in vulkan-zig's root.
- Implementation of https://vulkan-tutorial.org using
@cImport
'ed bindings: https://github.com/andrewrk/zig-vulkan-triangle. - Alternative binding generator: https://github.com/SpexGuy/Zig-Vulkan-Headers
- Zig bindings for GLFW: https://github.com/hexops/mach-glfw
- With vulkan-zig integration example: https://github.com/hexops/mach-glfw-vulkan-example