如何让windows自动扩展桌面？程序实现。

Question

效果就好像通过打开“显示属性”－“设置”－“将windows桌面扩展到该显示器上”的效果一样。但不是模拟这样的操作过程，希望是通过api或者是注册表来修改。不知道有没有大侠帮忙解决一下。
先谢过了。

Answer 1

search some keys words like "ChangeDisplaySettingsEx"

Answer 2

int SetDisplaySetting()
{
    DWORD DispNum = 0;
    DISPLAY_DEVICE DisplayDevice;
    DEVMODE defaultMode;
    HDC hdc;
    int nWidth;
    BOOL bFoundSecondary = FALSE;
    try
    {
        hdc = GetDC(0);
        nWidth = GetDeviceCaps(hdc,HORZRES);
        ReleaseDC(0,hdc);        //Initialize DisplayDevice.
        ZeroMemory(&DisplayDevice, sizeof(DisplayDevice));
        DisplayDevice.cb = sizeof(DisplayDevice);        // Get display devices.
        while ((EnumDisplayDevices(NULL, DispNum, &DisplayDevice, 0)) &&
                                (bFoundSecondary == FALSE))
        {
            ZeroMemory(&defaultMode, sizeof(DEVMODE));
            defaultMode.dmSize = sizeof(DEVMODE);
            if (!EnumDisplaySettings((LPSTR)DisplayDevice.DeviceName,
                       ENUM_REGISTRY_SETTINGS, &defaultMode))
            {
                return FALSE; // Store default failed
            }
            if (!(DisplayDevice.StateFlags & DISPLAY_DEVICE_PRIMARY_DEVICE))
            {
                //Found the first secondary device.
                bFoundSecondary = TRUE;
                defaultMode.dmPosition.x += nWidth;
                defaultMode.dmFields = DM_POSITION;
                ChangeDisplaySettingsEx((LPSTR)DisplayDevice.DeviceName,
                            &defaultMode, NULL, CDS_NORESET|CDS_UPDATEREGISTRY, NULL);
                //A second call to ChangeDisplaySettings updates the monitor.
                ChangeDisplaySettings(NULL, 0);
            }
            // Reinitialize DisplayDevice.
            ZeroMemory(&DisplayDevice, sizeof(DisplayDevice));
            DisplayDevice.cb = sizeof(DisplayDevice);
            DispNum++;
        }
        return 0;
    }catch(Exception &ex)
    {
        return -1;
    }
}