From 858f7f78afddd051cb091126b60715c7a2fe04fb Mon Sep 17 00:00:00 2001
From: Adam Kewley <contact@adamkewley.com>
Date: Mon, 26 Aug 2024 15:46:03 +0200
Subject: [PATCH] Refactor DepthStencilFormat OpenGL mappings into traits
 object

---
 src/oscar/CMakeLists.txt                      |  2 ++
 src/oscar/Graphics/GraphicsImplementation.cpp | 11 ++--------
 .../OpenGL/DepthStencilFormatOpenGLHelpers.h  | 20 +++++++++++++++++++
 .../OpenGL/DepthStencilFormatOpenGLTraits.h   | 20 +++++++++++++++++++
 4 files changed, 44 insertions(+), 9 deletions(-)
 create mode 100644 src/oscar/Graphics/OpenGL/DepthStencilFormatOpenGLHelpers.h
 create mode 100644 src/oscar/Graphics/OpenGL/DepthStencilFormatOpenGLTraits.h

diff --git a/src/oscar/CMakeLists.txt b/src/oscar/CMakeLists.txt
index 7f0c0ec6d..df8344c03 100644
--- a/src/oscar/CMakeLists.txt
+++ b/src/oscar/CMakeLists.txt
@@ -104,6 +104,8 @@ add_library(oscar STATIC
 
     Graphics/OpenGL/CPUDataTypeOpenGLTraits.h
     Graphics/OpenGL/CPUImageFormatOpenGLTraits.h
+    Graphics/OpenGL/DepthStencilFormatOpenGLTraits.h
+    Graphics/OpenGL/DepthStencilFormatOpenGLHelpers.h
     Graphics/OpenGL/Gl.cpp
     Graphics/OpenGL/Gl.h
     Graphics/OpenGL/TextureFormatOpenGLTraits.h
diff --git a/src/oscar/Graphics/GraphicsImplementation.cpp b/src/oscar/Graphics/GraphicsImplementation.cpp
index a684dede0..c05a8792e 100644
--- a/src/oscar/Graphics/GraphicsImplementation.cpp
+++ b/src/oscar/Graphics/GraphicsImplementation.cpp
@@ -31,6 +31,7 @@
 #include <oscar/Graphics/MeshTopology.h>
 #include <oscar/Graphics/OpenGL/CPUDataTypeOpenGLTraits.h>
 #include <oscar/Graphics/OpenGL/CPUImageFormatOpenGLTraits.h>
+#include <oscar/Graphics/OpenGL/DepthStencilFormatOpenGLHelpers.h>
 #include <oscar/Graphics/OpenGL/Gl.h>
 #include <oscar/Graphics/OpenGL/TextureFormatOpenGLTraits.h>
 #include <oscar/Graphics/RenderBufferLoadAction.h>
@@ -2051,8 +2052,6 @@ std::ostream& osc::operator<<(std::ostream& o, const Texture2D&)
 
 namespace
 {
-    enum class RenderBufferType { Color, Depth, NUM_OPTIONS };
-
     constexpr auto c_render_texture_format_strings = std::to_array<CStringView>({
         "Red8",
         "ARGB32",
@@ -2083,13 +2082,7 @@ namespace
 
     constexpr GLenum to_opengl_internal_color_format_enum(const DepthRenderBufferParams& params)
     {
-        static_assert(num_options<DepthStencilFormat>() == 2);
-
-        switch (params.format) {
-        case DepthStencilFormat::D24_UNorm_S8_UInt: return GL_DEPTH24_STENCIL8;
-        case DepthStencilFormat::D32_SFloat:        return GL_DEPTH_COMPONENT32F;
-        default:                                    return GL_DEPTH24_STENCIL8;
-        }
+        return detail::to_opengl_internal_color_format_enum(params.format);
     }
 
     constexpr CPUImageFormat equivalent_cpu_image_format_of(const RenderTextureFormat& format)
diff --git a/src/oscar/Graphics/OpenGL/DepthStencilFormatOpenGLHelpers.h b/src/oscar/Graphics/OpenGL/DepthStencilFormatOpenGLHelpers.h
new file mode 100644
index 000000000..3d01ceffc
--- /dev/null
+++ b/src/oscar/Graphics/OpenGL/DepthStencilFormatOpenGLHelpers.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <oscar/Graphics/Detail/DepthStencilFormatList.h>
+#include <oscar/Graphics/OpenGL/DepthStencilFormatOpenGLTraits.h>
+#include <oscar/Graphics/OpenGL/Gl.h>
+#include <oscar/Utils/EnumHelpers.h>
+
+#include <array>
+
+namespace osc::detail
+{
+    constexpr GLenum to_opengl_internal_color_format_enum(const DepthStencilFormat& format)
+    {
+        constexpr auto lut = []<DepthStencilFormat... Formats>(OptionList<DepthStencilFormat, Formats...>) {
+            return std::to_array({ DepthStencilFormatOpenGLTraits<Formats>::internal_color_format... });
+        }(DepthStencilFormatList{});
+
+        return lut.at(to_index(format));
+    }
+}
diff --git a/src/oscar/Graphics/OpenGL/DepthStencilFormatOpenGLTraits.h b/src/oscar/Graphics/OpenGL/DepthStencilFormatOpenGLTraits.h
new file mode 100644
index 000000000..01ed9a86d
--- /dev/null
+++ b/src/oscar/Graphics/OpenGL/DepthStencilFormatOpenGLTraits.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <oscar/Graphics/OpenGL/Gl.h>
+#include <oscar/Graphics/DepthStencilFormat.h>
+
+namespace osc::detail
+{
+    template<DepthStencilFormat>
+    struct DepthStencilFormatOpenGLTraits;
+
+    template<>
+    struct DepthStencilFormatOpenGLTraits<DepthStencilFormat::D24_UNorm_S8_UInt> final {
+        static inline constexpr GLenum internal_color_format = GL_DEPTH24_STENCIL8;
+    };
+
+    template<>
+    struct DepthStencilFormatOpenGLTraits<DepthStencilFormat::D32_SFloat> final {
+        static inline constexpr GLenum internal_color_format = GL_DEPTH_COMPONENT32F;
+    };
+}