AdvancedOptionalfrontFacing?: neverReserved for @builtin(front_facing), which the compiler declares
Optionalposition?: neverReserved for @builtin(position), which the compiler declares
OptionalsampleIndex?: neverReserved for @builtin(sample_index)
OptionalsampleMask?: neverReserved for @builtin(sample_mask)
The varyings a bit declares, keyed by name
position,frontFacing,sampleIndexandsampleMaskare reserved. WGSL fragment code readsinput.positionandinput.frontFacingwithout declaring them; GLSL readsgl_FragCoordandgl_FrontFacing.