clear = FrameBuffer $ ColorImage @1 $ V4 1 0 0 0.5

triangleRasterCtx = TriangleCtx CullNone PolygonFill NoOffset LastVertex
colorFragmentCtx = (ColorOp NoBlending (V4 True True True True))

rasterizeWith = rasterizePrimitives
triangles = triangleRasterCtx

quadVertexStream = fetch "quad" Triangle (Attribute "position" :: Vec 4 Float)

transform s f =  mapPrimitives (\v -> (f v, v)) s

mapFragments2 s fs = accumulate colorFragmentCtx (\a -> fs a) s clear

--render :: (Vec 4 Float -> Vec 4 Float) -> Output
render f = quadVertexStream                 -- id vertices
    `transform`    id
     &             rasterizeWith triangles Smooth  -- rasterize
    `mapFragments2` f
     &             ScreenOut                --  draw into screen

main = render $ \a -> let v = sin a in sin v