Custom attribute and reflection.

[obfuscate]

Hello!

I have faced some problems with retrieving reflection from a slang file.

For example, I want to mark some field in an Input Assembly structure as compressed. How I understood I should create a custom attribute and use it, something like this:

[__AttributeUsage(_AttributeTargets.Var)]
struct CompressedFormatAttribute
{
	string format;
};

struct IA2VS_Mesh
{
	float3 pos : POSITION;
	[CompressedFormat("ubyte")]
	float4 color : COLOR;
};

But I tried many options and I couldn't get that metadata during iterating over reflection. Reflection gives me IA2VS_Mesh data, gives me each field in the structure, but when I check the "COLOR" field I can't fetch "CompresedFormat" attribute. Can you help me?

there is my code snippet for reflection:

// I use here ICompileRequest and no modules.

Slang::ComPtr<slang::IComponentType> reflection;
request->getProgramWithEntryPoints(reflection.writeRef());
auto* layout = reflection->getLayout(targetIndex);

for (uint8_t entryId = 0; entryId < layout->getEntryPointCount(); ++entryId)
{
	auto* entry = layout->getEntryPointByIndex(entryId);

	const int32_t numParams = entry->getParameterCount();
	for (int32_t paramId = 0; paramId < numParams; ++paramId)
	{
		parseVariable(&globalSession, *entry->getParameterByIndex(paramId), * shader);
	}
	...
}

void parseVariable(slang::IGlobalSession* globalSession, slang::VariableLayoutReflection& var, render::Shader& shader)
{
	const auto category = var.getCategory();
	if (category != slang::ParameterCategory::VaryingInput && category != slang::ParameterCategory::Mixed)
	{
		return;
	}
	const auto kind = type->getKind();
	auto typeName = std::string_view(type->getName());
	if (kind == slang::TypeReflection::Kind::Struct)
	{
		if (var.getStage() == SlangStage::SLANG_STAGE_VERTEX
		 && typeName.find("IA2VS") != std::string_view::npos)
		{
			createInputAssembly(globalSession, var, shader);
		}
		...
	}
	...
}

void createInputAssembly(slang::IGlobalSession* globalSession, slang::VariableLayoutReflection& ia, render::Shader& shader)
{
	auto layout = ia.getTypeLayout();
	auto numFields = layout->getFieldCount();
	for (uint32_t fieldId = 0; fieldId < numFields; ++fieldId)
	{
		auto* field = layout->getFieldByIndex(fieldId);

		//-- How to get attributes here? I have tried to use field->getVariable(), field->getType(), field->getVariable()->getType(), field->getTypeLayout(), but getUserAttributeCount() always returned 0.


		auto* type = field->getType();
		auto kind = type->getKind();
		if (kind == slang::TypeReflection::Kind::Vector || kind == slang::TypeReflection::Kind::Scalar)
		{
			... create input element desc for graphics api here...
		}
		...
	}
}

//-- How to get attributes in the createInputAssembly for each field? I have tried to use field->getVariable(), field->getType(), field->getVariable()->getType(), field->getTypeLayout(), but getUserAttributeCount() always returned 0.
What I do wrong? Or may be there is a simpler way to do it?

Upd:
layout->toJson() returns the following data for the Color field:

{
    "name": "color",
    "type": {
        "kind": "vector",
        "elementCount": 4,
        "elementType": {
            "kind": "scalar",
            "scalarType": "float32"
        }
    },
    "stage": "vertex",
    "binding": {"kind": "varyingInput", "index": 6},
    "semanticName": "COLOR"
}

Is it ok?

[jhelferty-nv]

If I use your struct as a RWStructuredBuffer, I see your attribute under userAttribs, nested under returnType. See: slang playground, Compile and then look at the reflection tab.

If you want a quick way to look at the full json locally, you can also dump it on the command line by appending -reflection-json <file> to your normal slangc compilation arguments for the shader.

[obfuscate]

As I mentioned at the bottom of my post - layout->toJson() returned "reflection" without any user attributes, idk how your options (playground or compilation arguments) should help me:)

[jhelferty-nv]

I'm suggesting looking at the slang playground link because CompressedFormat and ubyte show up in the reflection there (scroll down, it's at the bottom). So the question is, is there a difference between that shader and the one you're using, or is your layout->toJson() reflecting a different place in the reflection hierarchy that doesn't include the user attribute (e.g., the Type instead of ResultType)?

[obfuscate]

So, I get a layout and reflection using the following code:

//-- Reflection.
Slang::ComPtr<slang::ICompileRequest> request;
 ...setup and compile request here...
Slang::ComPtr<slang::IComponentType> reflection;
request->getProgramWithEntryPoints(reflection.writeRef());
auto* layout = reflection->getLayout(targetIndex);
Slang::ComPtr<slang::IBlob> jsonBlob;
layout->toJson(jsonBlob.writeRef());

As far as I understand, this layout contains the representation of the whole shader. That's why it was strange for me why it didn't contain any mentioning about my custom attributes.