wgpuInstanceEnumerateAdapters will return 0 adapters when passed WGPUInstanceBackend_All

[laurelkeys]

Take this snippet from examples/enumerate_adapters/main.c:

wgpu-native/examples/enumerate_adapters/main.c

Lines 15 to 19 in 5b75378

	const size_t adapter_count =
	wgpuInstanceEnumerateAdapters(instance, NULL, NULL);
	WGPUAdapter *adapters = malloc(sizeof(WGPUAdapter) * adapter_count);
	assert(adapters);
	wgpuInstanceEnumerateAdapters(instance, NULL, adapters);

The following is expected to work like it, but it currently returns adapter_count = 0:

const WGPUInstanceEnumerateAdapterOptions options = { .backends = WGPUInstanceBackend_All };
const size_t adapter_count =
    wgpuInstanceEnumerateAdapters(instance, &options, NULL);
WGPUAdapter *adapters = malloc(sizeof(WGPUAdapter) * adapter_count);
assert(adapters);
wgpuInstanceEnumerateAdapters(instance, &options, adapters);

On the other hand, passing .backends = (WGPUInstanceBackend_Vulkan | WGPUInstanceBackend_GL | WGPUInstanceBackend_Metal | WGPUInstanceBackend_DX12 | WGPUInstanceBackend_DX11 | WGPUInstanceBackend_BrowserWebGPU) does work (i.e. it returns the same adapter_count as the first snippet where NULL is used.

The problem seems to be in src/lib.rs not accounting for the fact that WGPUInstanceBackend_All = 0 (and that, on Rust's side, it should be mapped to wgt::Backends::all()):

wgpu-native/src/lib.rs

Lines 2720 to 2725 in 5b75378

	let inputs = match options {
	Some(options) => wgc::instance::AdapterInputs::Mask(
	map_instance_backend_flags(options.backends as native::WGPUInstanceBackend),
	|_| (),
	),
	None => wgc::instance::AdapterInputs::Mask(wgt::Backends::all(), |_| ()),

Note: I didn't look further as I'm using the wgpu_native.dll and .pdb (v0.18.1.4) from C++ and haven't downloaded the code (e.g. to edit and build it), but please let me know if there's more information I could provide.

[laurelkeys]

Btw, are there plans on updating wgpu.h to use WGPU_NULLABLE like webgpu.h already does? This would be great for documenting Option<>al parameters, e.g.:

//                                                          vvvvvvvvvvvvv
size_t wgpuInstanceEnumerateAdapters(WGPUInstance instance, WGPU_NULLABLE WGPUInstanceEnumerateAdapterOptions const * options, WGPUAdapter * adapters);