anchor.diff:  
           // fragment shader code
           // TODO: 3D: figure out how to apply layout(location ...) to uniform.
  -        let samplerFragmentShaderStr =
  +        let fragmentShaderStr =
               [Constants.Render.GlslVersionPragma
                "uniform sampler2D tex;"
                "uniform vec4 color;"
  
positive.code: 
          // vertex shader code
          // TODO: 3D: figure out how to apply layout(location ...) to uniform.
          let samplerVertexShaderStr =
              [Constants.Render.GlslVersionPragma
               "layout(location = 0) in vec2 position;"
               "layout(location = 1) in vec2 texCoordsIn;"
  
negative.code:              "}"] |> String.join "\n"
  
          // create shader
          let shader = CreateShaderFromStrs (vertexShaderStr, fragmentShaderStr)
          let colorUniform = OpenGL.Gl.GetUniformLocation (shader, "color")
          let modelViewProjectionUniform = OpenGL.Gl.GetUniformLocation (shader, "modelViewProjection")
          let texUniform = OpenGL.Gl.GetUniformLocation (shader, "tex")
  