mach gpu

The WebGPU interface for Zig, featuring:

Zero-fuss installation, cross-compilation at the flip of a switch, and broad platform support.
100% API coverage. Every function, type, constant, etc. has been exposed in a ziggified API.
Desktop, Steam Deck, (soon) web, and (future) mobile support.
A modern graphics API similar to Metal, Vulkan, and DirectX 12.
Cross-platform shading language
Compute shaders
Advanced GPU features where hardware support is available.

Benefits of mach/gpu and WebGPU

mach/gpu is a zero-cost idiomatic Zig interface to the next-generation WebGPU API, which supersedes WebGL and exposes the common denominator between the latest low-level graphics APIs (Vulkan, Metal, D3D12) in the web.

Despite its name, WebGPU was built with native support in mind and has substantial investment from Mozilla, Google, Microsoft, Intel, and Apple.

When targeting WebAssembly, mach/gpu merely calls into the browser’s native WebGPU implementation.

When targeting native platforms, we build Google Chrome’s WebGPU implementation, Dawn using Zig as the C/C++ compiler toolchain. We bypass the client-server sandboxing model, and use zig build (plus a lot of hand-holding) to support zero-fuss cross compilation & installation without any third-party Google tools, libraries, etc. Just zig and git needed, nothing else.

Perfecting WebGPU for Zig

There is a detailed write-up of how we’ve been perfecting WebGPU for Zig.

Usage

On your own, this involves creating a window (using GLFW, and other APIs if you want Web, Mobile, or other platform support), using Dawn’s API to create a device and bind it to that window, using OS-specific APIs to get the window handle to bind, etc. examples/main.zig demonstrates how to do this. There’s a fair amount of setup code involved.

You may also want to consider using Mach core.

Goals

Allow comptime-defined interception of WebGPU API requests (comptime interfaces.)
Expose a standard Dawn webgpu.h-compliant C ABI, which routes through Zig comptime interfaces.
Support Dawn and Browser (via WASM/JS) implementations of WebGPU.
Broad platform support: desktop, mobile, web, consoles.
First-class Linux support (Wayland, OpenGL and OpenGL ES fallbacks, etc.)

Non-goals

Support non-Dawn (e.g. Rust WebGPU) implementations if they don’t match the same webgpu.h as Dawn.
Maintain backwards compatibility with deprecated webgpu.h methods.

Getting started

Create a build.zig.zon in your project (replace LATEST_COMMIT with the latest commit hash):

.{
    .name = "mypkg",
    .version = "0.1.0",
    .dependencies = .{
        .mach_gpu = .{
            .url = "https://pkg.machengine.org/mach-gpu/LATEST_COMMIT.tar.gz",
        },
    },
}

Run zig build in your project, and the compiler will instruct you to add a .hash = "..." field next to .url:

note: expected .hash = "12209838fcfb7a77d2d6931efdc7448c033a1b7dad11d082c94bbeeba9d1038cd311",

Then use the dependency in your build.zig:

pub fn build(b: *std.Build) void {
    ...
    exe.addModule("mach-gpu", b.dependency("mach_gpu", .{
        .target = target,
        .optimize = optimize,
    }).module("mach-gpu"));
}

You can now use it in your src/main.zig file:

const gpu = @import("mach-gpu");

Ran into trouble?

Triple-check you followed the build.zig.zon instructions correctly, it’s easy to mess that part up.

Feel free to join the Mach Discord community for help.

Quality of life improvements

We make the following quality of life improvements.

Flag sets

See perfecting WebGPU for Zig.

Optionality & nullability

Optional values default to their zero value (either null or a struct constructor .{}) when specified as optional in dawn.json. This means things like label, next_in_chain, etc. do not need to be specified.
Fields representing a slice with a _count field are nullable pointers defaulting to null and 0 by default.

Slice helpers

Some WebGPU APIs expose slices as pointers and lengths, we either wrap these to provide a slice or alter the method directly to provide a slice (if little overhead.) The original C-style API can always be accessed via the gpu.Impl type in any case.

The slice helpers are:

Adapter.enumerateFeaturesOwned
Buffer.getConstMappedRange
Buffer.getMappedRange
CommandEncoder.writeBuffer
ComputePassEncoder.setBindGroup
Device.enumerateFeaturesOwned
Queue.writeTexture
Queue.writeBuffer
RenderPassEncoder.executeBundles
RenderBundleEncoder.setBindGroup
RenderPassEncoder.setBindGroup

And, to initialize data structures with slices in them, the following helpers are provided:

BindGroupLayout.Descriptor.init
BindGroup.Descriptor.init
dawn.TogglesDescriptor.init
Device.Descriptor.init
PipelineLayout.Descriptor.init
QuerySet.Descriptor.init
RenderBundleEncoder.Descriptor.init
Texture.Descriptor.init
ComputePassDescriptor.init
RenderPassDescriptor.init
ProgrammableStageDescriptor.init
VertexBufferLayout.init
VertexState.init
FragmentState.init
CompilationInfo.getMessages

Typed callbacks

Most WebGPU callbacks provide a way to provide a userdata: *anyopaque pointer to the callback for context. We alter these APIs to expose a typed context pointer instead (again, the original API is always available via the gpu.Impl type should you want it):

Instance.requestAdapter
Adapter.requestDevice
Queue.onSubmittedWorkDone
Buffer.mapAsync
ShaderModule.getCompilationInfo
Device.createComputePipelineAsync
Device.createRenderPipelineAsync
Device.popErrorScope
Device.setDeviceLostCallback
Device.setLoggingCallback
Device.setUncapturedErrorCallback

next_in_chain extension type safety

WebGPU exposes struct types which are extendable arbitrarily, often by implementation-specific extensions. For example:

const extension = gpu.Surface.DescriptorFromWindowsHWND{
  .chain = gpu.ChainedStruct{.next = null, .s_type = .surface_descriptor_from_windows_hwnd},
  .hinstance = foo,
  .hwnd = bar,
}
const descriptor = gpu.Surface.Descriptor{
  .next_in_chain = @ptrCast(?*const ChainedStruct, &extension),
};

Here gpu.Surface.Descriptor is a concrete type. The next_in_chain field is set to an arbitrary pointer which follows the gpu.ChainedStruct pattern: it must begin with a gpu.ChainedStruct where the s_type identifies which fields may follow after, and .next could theoretically chain more extensions on too.

Complexity aside, next_in_chain is not type safe! It cannot be, because such an extension could be implementation-specific. To make this safer, we instead change the next_in_chain field type to be a union, where one option is the type-unsafe generic pointer, and the other options are known extensions:

pub const NextInChain = extern union {
    generic: ?*const ChainedStruct,
    from_windows_hwnd: *const DescriptorFromWindowsHWND,
    // ...
};

Additionally we initialize .chain with a default value, making our earlier snippet look like this in most cases:

const descriptor = gpu.Surface.Descriptor{
  .next_in_chain = .{.from_windows_hwnd = &.{
    .hinstance = foo,
    .hwnd = bar,
  }},
}

Others

Device.createShaderModuleWGSL (helper to create WGSL shader modules more nicely)

There may be other opportunities for helpers, to improve the existing APIs, or add utility APIs on top of the existing APIs. If you find one, please open an issue we’d love to consider it.