GetCurrrentTopology.cpp

LONG GetCurrentTopology(DISPLAYCONFIG_TOPOLOGY_ID& currentTopology)
{
	LONG lRet = ERROR_SUCCESS;
	UINT32 numPathInfoArrayElements = 0;
	UINT32 numModeInfoArrayElements = 0;
	DISPLAYCONFIG_PATH_INFO emptyPathInfo = { 0 };
	DISPLAYCONFIG_MODE_INFO emptyModeInfo = { 0 };
	std::vector<DISPLAYCONFIG_PATH_INFO> vecDisplayConfigPathInfo;
	std::vector<DISPLAYCONFIG_MODE_INFO> vecDisplayConfigModeInfo;
	currentTopology = DISPLAYCONFIG_TOPOLOGY_FORCE_UINT32;
	do
	{
		vecDisplayConfigPathInfo.clear();
		vecDisplayConfigModeInfo.clear();
		lRet = ::GetDisplayConfigBufferSizes(QDC_DATABASE_CURRENT, &numPathInfoArrayElements, &numModeInfoArrayElements);
		if (ERROR_SUCCESS != lRet)
		{
			// Log
			// std::cout << "Failed to get display config buffer size, error: " << std::hex << lRet << std::endl;
			break;
		}

		vecDisplayConfigPathInfo.resize(numPathInfoArrayElements, emptyPathInfo);
		vecDisplayConfigModeInfo.resize(numModeInfoArrayElements, emptyModeInfo);

		lRet = ::QueryDisplayConfig(QDC_DATABASE_CURRENT,
			&numPathInfoArrayElements, vecDisplayConfigPathInfo.data(),
			&numModeInfoArrayElements, vecDisplayConfigModeInfo.data(),
			&currentTopology);
		if (ERROR_SUCCESS != lRet)
		{
			// Log
			// std::cout << "Failed to query display config path and mode info, error: " << std::hex << lRet << std::endl;
		}
	} while (ERROR_INSUFFICIENT_BUFFER == lRet);

	return lRet;
}

int main()
{
	DISPLAYCONFIG_TOPOLOGY_ID m = DISPLAYCONFIG_TOPOLOGY_FORCE_UINT32;
	if (SUCCEEDED(GetCurrentTopology(m)))
	{
		std::cout << "current topology: " << m;
	}
	
	return 0;
  }