dawn_wrapper

A C++ wrapper around Dawn, Google's WebGPU implementation. Targets both native (macOS) and browser (via Emscripten) from the same codebase.

Browser Support

Browser	Status	Notes
Chrome	✅ Supported	Primary target
Edge	✅ Supported	Chromium-based, behaves like Chrome
Safari	⚠️ Broken	Memory misalignment in SDF output. Under investigation
Firefox	❌ Not supported	Out of scope

Example

example.cpp

#include <iostream>
#include <sstream>

#include <lib/dawn_wrapper/src/dawn_wrapper.h>

using namespace std;
using namespace dawn_wrapper;

int main()
{
    using vector_type = vector<uint32_t>;
    const vector_type data = { 0, 1, 3, 5, 7, 11, 13, 17, 19 };
    const unsigned size_bytes = unsigned(data.size()) * sizeof(vector_type::value_type);

    enum {
        binding_in = 1,
        binding_out = 2,
        workgroup_size = 8,
    };
    const auto entry_point = "go";

    stringstream shader_script;
    shader_script
        << "@group(0) @binding(" << binding_in << ") var<storage, read> inputBuffer : array<u32>;\n"
        << "@group(0) @binding(" << binding_out << ") var<storage, read_write> outputBuffer: array<u32>;\n"
        << "@compute @workgroup_size(" << workgroup_size << ")\n"
        << "fn " << entry_point << "(@builtin(global_invocation_id) id: vec3<u32>) {\n"
        << "outputBuffer[id.x] = inputBuffer[id.x] + 2;"
        << "}";

    dawn_plugin plugin;

    // compile shader
    auto comp = plugin.make_compute();
    comp.compile_shader(shader_script.str(), entry_point);

    // layout and pipeline
    auto layout = comp.make_bindgroup_layout()
        .add_read_only_buffer(binding_in)
        .add_buffer(binding_out);
    comp.init_pipeline(layout);

    // buffers
    buffer_wrapper input = plugin.make_dst_buffer(size_bytes, buffer_type::storage).write(data.data());
    buffer_wrapper output = plugin.make_src_buffer(size_bytes, buffer_type::storage);
    buffer_wrapper mapped = plugin.make_dst_buffer(size_bytes, buffer_type::map_read);

    // compute
    auto bindgroup = comp.make_bindgroup()
        .add_buffer(binding_in, input)
        .add_buffer(binding_out, output);
    auto encoder = plugin.make_encoder();
    comp.compute(bindgroup, unsigned(data.size()), 1, encoder);
    plugin.run();

    // get result
    encoder.copy_buffer_to_buffer(output, mapped).submit_command_buffer();
    mapped.get_output([](auto size, auto data) {
        const uint32_t* p = reinterpret_cast<const vector_type::value_type*>(data);
        for (auto i = 0; i < size / sizeof(vector_type::value_type); ++i) {
            cout << p[i] << endl;
        }
    });

    while (!mapped.done()) {
        plugin.run();
    }

    return 0;
}

Output:

2
3
5
7
9
13
15
19
21

Build

CMakeLists.txt

cmake_minimum_required(VERSION 3.27)

project(Example)

add_executable(Example src/example.cpp)

set_target_properties(Example PROPERTIES
    CXX_STANDARD 20
    CXX_STANDARD_REQUIRED ON
    CXX_EXTENSIONS OFF
    COMPILE_WARNING_AS_ERROR ON
)

add_compile_definitions(TARGET_HEADLESS)
add_subdirectory(lib/dawn_wrapper)
add_subdirectory(lib/asserter)

if (EMSCRIPTEN)
    set_target_properties(Example PROPERTIES SUFFIX ".html")
    target_link_options(Example PRIVATE
        --use-port=emdawnwebgpu
        --closure=1
        --emrun
    )
endif()

target_link_libraries(Example PRIVATE dawn_wrapper)
target_include_directories(Example SYSTEM PUBLIC ${CMAKE_CURRENT_LIST_DIR}/lib)

Native:

cmake -B build
cmake --build build -j 8
./build/Example

Emscripten:

emcmake cmake -B web-build
cmake --build web-build
emrun --browser chrome web-build/Example.html

Dawn

Dawn is checked in wholesale under lib/dawn/ at branch chromium/7767. See dawn_integration.md for update instructions.