Fix for compile errors with wgpu backend on OSX/dawn

[trbabb]

On OSX clang when building for wgpu with -DIMGUI_IMPL_WEBGPU_BACKEND_DAWN=1, the following errors occur:

theta/thirdparty/imgui/imgui_impl_wgpu.cpp:400:13: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
  400 |             "Dear ImGui Vertex buffer",
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
      |             {
  401 | #if defined(IMGUI_IMPL_WEBGPU_BACKEND_DAWN) || defined(IMGUI_IMPL_WEBGPU_BACKEND_WGPU)
      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  402 |             WGPU_STRLEN,
      |             ~~~~~~~~~~~
      |                        }
theta/thirdparty/imgui/imgui_impl_wgpu.cpp:427:13: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
  427 |             "Dear ImGui Index buffer",
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~
      |             {
  428 | #if defined(IMGUI_IMPL_WEBGPU_BACKEND_DAWN) || defined(IMGUI_IMPL_WEBGPU_BACKEND_WGPU)
      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  429 |             WGPU_STRLEN,
      |             ~~~~~~~~~~~
      |                        }
theta/thirdparty/imgui/imgui_impl_wgpu.cpp:639:9: error: suggest braces around initialization of subobject [-Werror,-Wmissing-braces]
  639 |         "Dear ImGui Uniform buffer",
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |         {
  640 | #if defined(IMGUI_IMPL_WEBGPU_BACKEND_DAWN) || defined(IMGUI_IMPL_WEBGPU_BACKEND_WGPU)
      | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  641 |         WGPU_STRLEN,
      |         ~~~~~~~~~~~
      |                    }

The definition for a wgpu BufferDescriptor is:

typedef struct WGPUBufferDescriptor {
    WGPUChainedStruct * nextInChain;
    WGPUStringView label;
    WGPUBufferUsage usage;
    uint64_t size;
    WGPUBool mappedAtCreation;
} WGPUBufferDescriptor WGPU_STRUCTURE_ATTRIBUTE;

and for WGPUStringView:

typedef struct WGPUStringView {
    WGPU_NULLABLE char const * data;
    size_t length;
} WGPUStringView WGPU_STRUCTURE_ATTRIBUTE;

In order for the length parameter to be included in the string view, braces are needed around that parameter.

[ocornut]

Have you tried with Emscripten and other backends?

[trbabb]

I haven't— is there a test I can run?

[ocornut]

I haven't— is there a test I can run?

There are examples apps running on Emscripten and supposedly Dawn, although the general status of it is a mess partly because there are PR coming from every direction, mostly #8381, but I myself don't have easy TL;DR; steps and compatibility tables to understand what's going on with those evolving API.

[ocornut]

The CI test for Emscripten fails on this with latest Emscripten:
https://github.com/ocornut/imgui/actions/runs/17170197464/job/48930521396?pr=8898

[ocornut]

@BrutPitt can you explain why this PR (you check the diff) needs to adds braces to fix "wgpu backend on OSX/dawn" whereas your PR #8381 doesn't? How is that possible, it is because either PR is relying on an older Dawn or would it be due to another difference?

[ocornut]

I understood that the issue with Dawn did not manifest in #8381 because it requires -Wall which was messing.