MoltenVK reports VK_KHR_fragment_shader_barycentric, but its SPIR-V to MSL step
rejects the PerVertexKHR decoration that the barycentric path uses, so every
pixel shader on that path fails to compile into a pipeline. Treat the feature
as unavailable when the driver is MoltenVK, so the no-barycentric path is used.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Morten Holm