time = Uniform "Time" :: Float
clear = FrameBuffer ((ColorImage @1 $ V4 1 0 0 0.5))

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

rasterizeWith = rasterizePrimitives
triangles = triangleRasterCtx

quadVertexStream = fetch "quad" ((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 f = quadVertexStream                 -- id vertices
    `transform`    id
     &             rasterizeWith triangles ((Smooth))  -- rasterize
    `mapFragments2` f
     &             ScreenOut                --  draw into screen

main = render $ \c -> if time < 0.5 then c else blue