dolphin/Source/Core/VideoCommon/VideoBackendBase.cpp

// Copyright 2011 Dolphin Emulator Project
// Licensed under GPLv2+
// Refer to the license.txt file included.

#include <algorithm>
#include <memory>
#include <string>
#include <vector>

// TODO: ugly
#ifdef _WIN32
#include "VideoBackends/D3D/VideoBackend.h"
#include "VideoBackends/D3D12/VideoBackend.h"
#endif
#include "VideoBackends/Null/VideoBackend.h"
#include "VideoBackends/OGL/VideoBackend.h"
#include "VideoBackends/Software/VideoBackend.h"

#include "VideoCommon/VideoBackendBase.h"

std::vector<std::unique_ptr<VideoBackendBase>> g_available_video_backends;
VideoBackendBase* g_video_backend = nullptr;
static VideoBackendBase* s_default_backend = nullptr;

#ifdef _WIN32
#include <windows.h>

// Nvidia drivers >= v302 will check if the application exports a global
// variable named NvOptimusEnablement to know if it should run the app in high
// performance graphics mode or using the IGP.
extern "C" {
__declspec(dllexport) DWORD NvOptimusEnablement = 1;
}
#endif

void VideoBackendBase::PopulateList()
{
  // OGL > D3D11 > D3D12 > SW > Null
  g_available_video_backends.push_back(std::make_unique<OGL::VideoBackend>());
#ifdef _WIN32
  g_available_video_backends.push_back(std::make_unique<DX11::VideoBackend>());

  // More robust way to check for D3D12 support than (unreliable) OS version checks.
  HMODULE d3d12_module = LoadLibraryA("d3d12.dll");
  if (d3d12_module != nullptr)
  {
    FreeLibrary(d3d12_module);
    g_available_video_backends.push_back(std::make_unique<DX12::VideoBackend>());
  }
#endif
  g_available_video_backends.push_back(std::make_unique<SW::VideoSoftware>());
  g_available_video_backends.push_back(std::make_unique<Null::VideoBackend>());

  const auto iter =
      std::find_if(g_available_video_backends.begin(), g_available_video_backends.end(),
                   [](const auto& backend) { return backend != nullptr; });

  if (iter == g_available_video_backends.end())
    return;

  s_default_backend = iter->get();
  g_video_backend = iter->get();
}

void VideoBackendBase::ClearList()
{
  g_available_video_backends.clear();
}

void VideoBackendBase::ActivateBackend(const std::string& name)
{
  // If empty, set it to the default backend (expected behavior)
  if (name.empty())
    g_video_backend = s_default_backend;

  const auto iter =
      std::find_if(g_available_video_backends.begin(), g_available_video_backends.end(),
                   [&name](const auto& backend) { return name == backend->GetName(); });

  if (iter == g_available_video_backends.end())
    return;

  g_video_backend = iter->get();
}