How to get screen position in CG fragment shader?

Unity Engine
1

in sm3.0, i can get this in VPOS

my code like this but it gets wrong : srcPos not specify

Shader "MyShader/test" {
	
	SubShader {
		Pass{
			Blend SrcAlpha OneMinusSrcAlpha
			
			CGPROGRAM

			#pragma target 3.0 
			#pragma fragment frag
			#pragma vertex vert
			
			#include "UnityCG.cginc"
			

			float4 vert( appdata_base v ) : POSITION{
				return mul(glstate.matrix.mvp, v.vertex);
			}

			float4 frag( srcPos : VPOS ) : COLOR {
				return float4(1.0, 0.0, 0.0, 0.5); 
				
			}
			ENDCG
		}
		
	} 
}
2

Where are the definition for all the non standard CG datatypes?

3

Non standard CG datatypes? Do you mean VPOS?

4

srcPos needs a type, not just a semantic. Try:

float4 srcPos : VPOS

I don’t recognize that semantic, though, so it might give you trouble.