How to specify capabilities of glsl / spirv shader

[dhardy]

I'm trying to use dual-source blending, but hit this validation error:

Pipeline expects the shader entry point to make use of dual-source blending.

It looks like WGSL has its own way of handling this:

enable dual_source_blending;

meanwhile a dual-source GLSL shader does no more than declare and assign to two output locations.

The naga test for this features a companion toml:

capabilities = "DUAL_SOURCE_BLENDING"

From what I can tell this has nothing to do with the GLSL standard, nor is it used by wgpu::include_spirv!, nor does naga/xtask appear to reference this, so the purpose of this is not clear.

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So how do I declare the "capabilities" of GLSL / SPIRV shaders?

[dhardy]

See: kas-gui/kas#620

I question whether this is a bug: attempting to validate a "capability" which is not defined by the (GLSL) shader?