Record zero-attribute vertex buffer when creating render pipeline

Currently Dawn ignores all zero-attribute vertex buffer in the given
pipeline descriptor when creating RenderPipelineBase because
zero-attribute vertex buffer is treated as unused slot, however the spec
doesn't state that zero-attribute vertex buffer should be ignored.

To support zero-attribute vertex buffer, this commit has the following

1. Add VertexBufferNotUsed enum value to wgpu::VertexStepMode to
   represent unused slots
2. Ignore VertexBufferNotUsed  step mode buffers when creating
   RenderPipelineBase and add tests to check it
3. Record zero-attribute vertex buffers when creating RenderPipelineBase
   and add tests to check it
4. Fix VertexStateTest::LastAllowedVertexBuffer broken by the above

Temporarily we set the enum value of
wgpu::VertexStepMode::VertexBufferNotUsed to 0 to pass the CTS tests
because currently empty vertex buffer slots step mode can be
zero-initialized. We will make a CL to Blink to explicitly set
wgpu::VertexStepMode::VertexBufferNotUsed for empty slots and change
the enum value to 2.

Bug: dawn:1000
Change-Id: Ibd4ab87f2c922e8e460f2311547f13d58f1d5611
Reviewed-by: Corentin Wallez <>
Kokoro: Kokoro <>
Commit-Queue: Takahiro <>
9 files changed
tree: 0c46c077c43f4e1c89a9f02beef44d64586c2967
  1. .vscode/
  2. build_overrides/
  3. docs/
  4. generator/
  5. include/
  6. infra/
  7. scripts/
  8. src/
  9. test/
  10. third_party/
  11. tools/
  12. webgpu-cts/
  13. .clang-format
  14. .clang-tidy
  15. .gitattributes
  16. .gitignore
  17. .gn
  20. CMakeLists.txt
  21. CMakeSettings.json
  23. codereview.settings
  25. CPPLINT.cfg
  26. dawn.json
  27. dawn_wire.json
  28. DEPS
  30. Doxyfile
  31. go.mod
  32. go.sum
  34. OWNERS
  36. README.chromium
  38. tint_overrides_with_defaults.gni

Dawn's logo: a sun rising behind a stylized mountain inspired by the WebGPU logo. The text Dawn is written below it.

Dawn, a WebGPU implementation

Dawn is an open-source and cross-platform implementation of the work-in-progress WebGPU standard. More precisely it implements webgpu.h that is a one-to-one mapping with the WebGPU IDL. Dawn is meant to be integrated as part of a larger system and is the underlying implementation of WebGPU in Chromium.

Dawn provides several WebGPU building blocks:

  • WebGPU C/C++ headers that applications and other building blocks use.
    • The webgpu.h version that Dawn implements.
    • A C++ wrapper for the webgpu.h.
  • A “native” implementation of WebGPU using platforms' GPU APIs:
    • D3D12 on Windows 10
    • Metal on macOS and iOS
    • Vulkan on Windows, Linux, ChromeOS, Android and Fuchsia
    • OpenGL as best effort where available
  • A client-server implementation of WebGPU for applications that are in a sandbox without access to native drivers
  • Tint is a compiler for the WebGPU Shader Language (WGSL).

Helpful links:

Documentation table of content

Developer documentation:

User documentation: (TODO, figure out what overlaps with the webgpu.h docs)




Apache 2.0 Public License, please see LICENSE.


This is not an officially supported Google product.