message: Include accum format in ref type
diff: @@ -39,7 +39,7 @@ public:
  using depth_type = typename pixel_traits<DepthFormat>::type;
  using accum_type = typename pixel_traits<DepthFormat>::type;
  - using ref_type = render_target_ref<ColorFormat, DepthFormat>;
  + using ref_type = render_target_ref<ColorFormat, DepthFormat, AccumFormat>;
  public:
  