Move most backend functionality to VideoCommon

Source/Core/VideoCommon/FramebufferShaderGen.h

@@ -0,0 +1,32 @@
+#pragma once
+#include <string>
+#include "VideoCommon/VideoCommon.h"
+
+enum class EFBReinterpretType;
+
+namespace FramebufferShaderGen
+{
+struct Config
+{
+  Config(APIType api_type_, u32 efb_samples_, u32 efb_layers_, bool ssaa_)
+      : api_type(api_type_), efb_samples(efb_samples_), efb_layers(efb_layers_), ssaa(ssaa_)
+  {
+  }
+
+  APIType api_type;
+  u32 efb_samples;
+  u32 efb_layers;
+  bool ssaa;
+};
+
+std::string GenerateScreenQuadVertexShader();
+std::string GeneratePassthroughGeometryShader(u32 num_tex, u32 num_colors);
+std::string GenerateTextureCopyVertexShader();
+std::string GenerateTextureCopyPixelShader();
+std::string GenerateResolveDepthPixelShader(u32 samples);
+std::string GenerateClearVertexShader();
+std::string GenerateEFBPokeVertexShader();
+std::string GenerateColorPixelShader();
+std::string GenerateFormatConversionShader(EFBReinterpretType convtype, u32 samples);
+
+}  // namespace FramebufferShaderGen