anchor.diff:                  OpenGL.Gl.EnableVertexAttribArray 0u
                   OpenGL.Gl.EnableVertexAttribArray 1u
                   OpenGL.Gl.EnableVertexAttribArray 2u
  -                OpenGL.Gl.VertexAttribPointer (0u, 2, OpenGL.VertexAttribType.Float, false, sizeof<Vertex>, Marshal.OffsetOf (typeof<Vertex>, "Pos"))
  +                OpenGL.Gl.VertexAttribPointer (0u, 2, OpenGL.VertexAttribType.Float, false, sizeof<Vertex>, Marshal.OffsetOf (typeof<Vertex>, "Position"))
                   OpenGL.Gl.VertexAttribPointer (1u, 2, OpenGL.VertexAttribType.Float, false, sizeof<Vertex>, Marshal.OffsetOf (typeof<Vertex>, "Coords"))
                   OpenGL.Gl.VertexAttribPointer (2u, 4, OpenGL.VertexAttribType.Float, false, sizeof<Vertex>, Marshal.OffsetOf (typeof<Vertex>, "Color"))
                   OpenGL.Gl.BufferData (OpenGL.BufferTarget.ArrayBuffer, uint sizeof<Vertex> * 6u * uint spriteMax, nativeint 0, OpenGL.BufferUsage.DynamicDraw)
  
positive.code:     /// Create a sprite shader program with uniforms:
      ///     0: sampler2D tex
      /// and attributes:
      ///     0: vec2 pos
      ///     1: vec2 coordIn
      ///     2: vec4 colorIn
      let private CreateSpriteProgram () =
  
          // vertex shader code
          let samplerVertexShaderStr =
              [Constants.Render.GlslVersionPragma
               "layout(location = 0) in vec2 pos;"
               "layout(location = 1) in vec2 coordIn;"
               "layout(location = 2) in vec4 colorIn;"
               "out vec2 coord;"
               "out vec4 color;"
               "void main()"
               "{"
               "  gl_Position = vec4(pos.x, pos.y, 0, 1);"
               "  coord = coordIn;"
               "  color = colorIn;"
               "}"] |> String.join "\n"
  
  
negative.code: 
          type [<StructuralEquality; NoComparison; StructLayout (LayoutKind.Sequential)>] private Vertex =
              struct
                  val mutable Position : Vector2
                  val mutable Coords : Vector2
                  val mutable Color : Color
                  end
  