Add backends

- Renamed GfxOpenGL to GfxOPenGL2
- Added GfxOpenGL3 backend for OpenGL 3.3+
- Added WIP DirectX9 backend
- Added structure for Citro3D
- Added linear Allocator

backends/include/pd_system/gfx_directx9.hpp

@@ -0,0 +1,39 @@
+#pragma once
+
+#include <pd/drivers/gfx.hpp>
+
+namespace PD {
+struct GfxDirectX9Config {
+  // Vertex Allocator
+  template <typename T>
+  using VertexAlloc = std::allocator<T>;
+  // Index Allocator
+  template <typename T>
+  using IndexAlloc = std::allocator<T>;
+
+  static constexpr size_t NumVertices = 32768;  // 8192*4
+  static constexpr size_t NumIndices = 49152;   // 8192*6
+};
+
+class GfxDirectX9 : public GfxDriverBase<GfxDirectX9Config> {
+ public:
+  GfxDirectX9(void* device = nullptr)
+      : GfxDriverBase("DirectX9"), pDevice(device) {}
+  ~GfxDirectX9() {}
+
+  void SysInit() override;
+  void SysDeinit() override;
+  void Submit(size_t count, size_t start) override;
+  void BindTexture(TextureID id) override;
+  void SysReset() override;
+  TextureID LoadTexture(const std::vector<PD::u8>& pixels, int w, int h,
+                        TextureFormat type = TextureFormat::RGBA32,
+                        TextureFilter filter = TextureFilter::Linear) override;
+  void DeleteTexture(const TextureID& tex) override;
+
+ private:
+  struct Impl;
+  Impl* impl = nullptr;
+  void* pDevice = nullptr;
+};
+}  // namespace PD