Make default graphics backend not show up as empty

Fixes https://bugs.dolphin-emu.org/issues/12245.

I considered making a change to DolphinQt instead of
the core, but then additional effort would've been
required to add the same fix to the Android GUI once
we start using the new config system there.

Source/Core/Core/Config/MainSettings.cpp

@@ -12,6 +12,7 @@
 #include "Core/HW/Memmap.h"
 #include "Core/HW/SI/SI_Device.h"
 #include "Core/PowerPC/PowerPC.h"
+#include "VideoCommon/VideoBackendBase.h"
 
 namespace Config
 {
@@ -97,7 +98,8 @@ const Info<bool> MAIN_OVERCLOCK_ENABLE{{System::Main, "Core", "OverclockEnable"}
 const Info<bool> MAIN_RAM_OVERRIDE_ENABLE{{System::Main, "Core", "RAMOverrideEnable"}, false};
 const Info<u32> MAIN_MEM1_SIZE{{System::Main, "Core", "MEM1Size"}, Memory::MEM1_SIZE_RETAIL};
 const Info<u32> MAIN_MEM2_SIZE{{System::Main, "Core", "MEM2Size"}, Memory::MEM2_SIZE_RETAIL};
-const Info<std::string> MAIN_GFX_BACKEND{{System::Main, "Core", "GFXBackend"}, ""};
+const Info<std::string> MAIN_GFX_BACKEND{{System::Main, "Core", "GFXBackend"},
+                                         VideoBackendBase::GetDefaultBackendName()};
 const Info<std::string> MAIN_GPU_DETERMINISM_MODE{{System::Main, "Core", "GPUDeterminismMode"},
                                                   "auto"};
 const Info<std::string> MAIN_PERF_MAP_DIR{{System::Main, "Core", "PerfMapDir"}, ""};

Source/Core/VideoBackends/D3D/VideoBackend.h

@@ -21,6 +21,8 @@ public:
 
   void InitBackendInfo() override;
 
+  static constexpr const char* NAME = "D3D";
+
 private:
   void FillBackendInfo();
 };

Source/Core/VideoBackends/D3D/main.cpp

@@ -29,7 +29,7 @@ namespace DX11
 {
 std::string VideoBackend::GetName() const
 {
-  return "D3D";
+  return NAME;
 }
 
 std::string VideoBackend::GetDisplayName() const

Source/Core/VideoBackends/D3D12/VideoBackend.cpp

@@ -27,7 +27,7 @@ namespace DX12
 {
 std::string VideoBackend::GetName() const
 {
-  return "D3D12";
+  return NAME;
 }
 
 std::string VideoBackend::GetDisplayName() const

Source/Core/VideoBackends/D3D12/VideoBackend.h

@@ -19,6 +19,8 @@ public:
   std::string GetDisplayName() const override;
   void InitBackendInfo() override;
 
+  static constexpr const char* NAME = "D3D12";
+
 private:
   void FillBackendInfo();
 };

Source/Core/VideoBackends/Null/VideoBackend.h

@@ -10,11 +10,14 @@ namespace Null
 {
 class VideoBackend final : public VideoBackendBase
 {
+public:
   bool Initialize(const WindowSystemInfo& wsi) override;
   void Shutdown() override;
 
-  std::string GetName() const override { return "Null"; }
+  std::string GetName() const override { return NAME; }
   std::string GetDisplayName() const override;
   void InitBackendInfo() override;
+
+  static constexpr const char* NAME = "Null";
 };
 }  // namespace Null

Source/Core/VideoBackends/OGL/VideoBackend.h

@@ -13,6 +13,7 @@ namespace OGL
 {
 class VideoBackend : public VideoBackendBase
 {
+public:
   bool Initialize(const WindowSystemInfo& wsi) override;
   void Shutdown() override;
 
@@ -21,6 +22,8 @@ class VideoBackend : public VideoBackendBase
 
   void InitBackendInfo() override;
 
+  static constexpr const char* NAME = "OGL";
+
 private:
   bool InitializeGLExtensions(GLContext* context);
   bool FillBackendInfo();

Source/Core/VideoBackends/OGL/main.cpp

@@ -62,7 +62,7 @@ namespace OGL
 {
 std::string VideoBackend::GetName() const
 {
-  return "OGL";
+  return NAME;
 }
 
 std::string VideoBackend::GetDisplayName() const

Source/Core/VideoBackends/Software/SWmain.cpp

@@ -45,7 +45,7 @@ public:
 
 std::string VideoSoftware::GetName() const
 {
-  return "Software Renderer";
+  return NAME;
 }
 
 std::string VideoSoftware::GetDisplayName() const

Source/Core/VideoBackends/Software/VideoBackend.h

@@ -19,5 +19,7 @@ class VideoSoftware : public VideoBackendBase
   std::optional<std::string> GetWarningMessage() const override;
 
   void InitBackendInfo() override;
+
+  static constexpr const char* NAME = "Software Renderer";
 };
 }  // namespace SW

Source/Core/VideoBackends/Vulkan/VideoBackend.h

@@ -15,9 +15,11 @@ public:
   bool Initialize(const WindowSystemInfo& wsi) override;
   void Shutdown() override;
 
-  std::string GetName() const override { return "Vulkan"; }
+  std::string GetName() const override { return NAME; }
   std::string GetDisplayName() const override { return _trans("Vulkan"); }
   void InitBackendInfo() override;
   void PrepareWindow(WindowSystemInfo& wsi) override;
+
+  static constexpr const char* NAME = "Vulkan";
 };
 }  // namespace Vulkan

Source/Core/VideoCommon/VideoBackendBase.cpp

@@ -197,9 +197,21 @@ u16 VideoBackendBase::Video_GetBoundingBox(int index)
   return result;
 }
 
+// This function is called at static initialization, so we can't rely on s_default_backend being set
+std::string VideoBackendBase::GetDefaultBackendName()
+{
+#ifdef HAS_OPENGL
+  return OGL::VideoBackend::NAME;
+#elif defined(_WIN32)
+  return DX11::VideoBackend::NAME;
+#else
+  return Vulkan::VideoBackend::NAME;
+#endif
+}
+
 void VideoBackendBase::PopulateList()
 {
-  // OGL > D3D11 > Vulkan > SW > Null
+  // OGL > D3D11 > D3D12 > Vulkan > SW > Null
 #ifdef HAS_OPENGL
   g_available_video_backends.push_back(std::make_unique<OGL::VideoBackend>());
 #endif

Source/Core/VideoCommon/VideoBackendBase.h

@@ -59,6 +59,7 @@ public:
   u32 Video_GetQueryResult(PerfQueryType type);
   u16 Video_GetBoundingBox(int index);
 
+  static std::string GetDefaultBackendName();
   static void PopulateList();
   static void ClearList();
   static void ActivateBackend(const std::string& name);