[App] Only start D3D12 if DLL exists

src/xenia/app/xenia_main.cc

@@ -105,11 +105,13 @@ std::unique_ptr<gpu::GraphicsSystem> CreateGraphicsSystem() {
     std::unique_ptr<gpu::GraphicsSystem> best;
 
 #if XE_PLATFORM_WIN32
+    if (xe::gpu::d3d12::D3D12GraphicsSystem::IsD3D12APIAvailable()) {
       best = std::unique_ptr<gpu::GraphicsSystem>(
           new xe::gpu::d3d12::D3D12GraphicsSystem());
       if (best) {
         return best;
       }
+    }
 #endif  // XE_PLATFORM_WIN32
     best = std::unique_ptr<gpu::GraphicsSystem>(
         new xe::gpu::vulkan::VulkanGraphicsSystem());

src/xenia/gpu/d3d12/d3d12_graphics_system.cc

@@ -27,6 +27,10 @@ D3D12GraphicsSystem::D3D12GraphicsSystem() {}
 
 D3D12GraphicsSystem::~D3D12GraphicsSystem() {}
 
+bool D3D12GraphicsSystem::IsD3D12APIAvailable() {
+  return xe::ui::d3d12::D3D12Provider::IsD3D12APIAvailable();
+}
+
 std::wstring D3D12GraphicsSystem::name() const {
   auto d3d12_command_processor =
       static_cast<D3D12CommandProcessor*>(command_processor());

src/xenia/gpu/d3d12/d3d12_graphics_system.h

@@ -26,6 +26,8 @@ class D3D12GraphicsSystem : public GraphicsSystem {
   D3D12GraphicsSystem();
   ~D3D12GraphicsSystem() override;
 
+  static bool IsD3D12APIAvailable();
+
   std::wstring name() const override;
 
   X_STATUS Setup(cpu::Processor* processor, kernel::KernelState* kernel_state,

src/xenia/ui/d3d12/d3d12_provider.cc

@@ -27,6 +27,15 @@ namespace xe {
 namespace ui {
 namespace d3d12 {
 
+bool D3D12Provider::IsD3D12APIAvailable() {
+  HMODULE library_d3d12 = LoadLibrary(L"D3D12.dll");
+  if (!library_d3d12) {
+    return false;
+  }
+  FreeLibrary(library_d3d12);
+  return true;
+}
+
 std::unique_ptr<D3D12Provider> D3D12Provider::Create(Window* main_window) {
   std::unique_ptr<D3D12Provider> provider(new D3D12Provider(main_window));
   InitializationResult result = provider->Initialize();
@@ -81,6 +90,7 @@ D3D12Provider::InitializationResult D3D12Provider::Initialize() {
   library_d3dcompiler_ = LoadLibrary(L"D3DCompiler_47.dll");
   if (library_dxgi_ == nullptr || library_d3d12_ == nullptr ||
       library_d3dcompiler_ == nullptr) {
+    XELOGE("Failed to load dxgi.dll, D3D12.dll and D3DCompiler_47.dll.");
     return InitializationResult::kLibraryLoadFailed;
   }
   bool libraries_loaded = true;

src/xenia/ui/d3d12/d3d12_provider.h

@@ -23,6 +23,8 @@ class D3D12Provider : public GraphicsProvider {
  public:
   ~D3D12Provider() override;
 
+  static bool IsD3D12APIAvailable();
+
   static std::unique_ptr<D3D12Provider> Create(Window* main_window);
 
   std::unique_ptr<GraphicsContext> CreateContext(