message: Include accum format in ref typ
diff: @@ -29,7 +29,7 @@ public:
  using depth_type = typename pixel_traits<DepthFormat>::type;
  using accum_type = typename pixel_traits<AccumFormat>::type;
  - using ref_type = render_target_ref<ColorFormat, DepthFormat>;
  + using ref_type = render_target_ref<ColorFormat, DepthFormat, AccumFormat>;
  public:
  