私は答えを見つけました。
SetDisplayConfig(0,NULL,0,NULL,SDC_TOPOLOGY_EXTEND|SDC_APPLY);
又は
SetDisplayConfig(0,NULL,0,NULL,SDC_TOPOLOGY_CLONE|SDC_APPLY);
:必要な表示設定を(重複などを拡張)を設定する
UINT32 PathArraySize = 0;
UINT32 ModeArraySize = 0;
DISPLAYCONFIG_PATH_INFO* PathArray;
DISPLAYCONFIG_MODE_INFO* ModeArray;
DISPLAYCONFIG_TOPOLOGY_ID CurrentTopology;
GetDisplayConfigBufferSizes(QDC_ALL_PATHS, &PathArraySize, &ModeArraySize);
PathArray = (DISPLAYCONFIG_PATH_INFO*)malloc(PathArraySize * sizeof(DISPLAYCONFIG_PATH_INFO));
memset(PathArray, 0, PathArraySize * sizeof(DISPLAYCONFIG_PATH_INFO));
ModeArray = (DISPLAYCONFIG_MODE_INFO*)malloc(ModeArraySize * sizeof(DISPLAYCONFIG_MODE_INFO));
memset(ModeArray, 0, ModeArraySize * sizeof(DISPLAYCONFIG_MODE_INFO));
LONG ret = QueryDisplayConfig(QDC_DATABASE_CURRENT,&PathArraySize, PathArray, &ModeArraySize, ModeArray, &CurrentTopology);
// Above CurrentTopology variable will aquire the current display setting (ie Extend, Duplicate etc)
free(PathArray);
free(ModeArray);
:現在の設定を識別するために