Get unique identifier for Windows monitors

Question

I have a setup with two regular displays and three projectors connected to a windows pc. In my win32 program I need to uniquely identify each monitor and store information for each such that I can retrieve the stored information even after computer restart.

The EnumDisplayDevices seems to return different device orders after restarting the computer. There is also GetPhysicalMonitorsFromHMONITOR which at least gives me the display's name. However, I need something like a serial number for my projectors, since they are the same model. How can I get such a unique identifier?

EDIT: This is the solution I came up with after reading the answer from user Anders (thanks!):

DISPLAY_DEVICEA dispDevice;
ZeroMemory(&dispDevice, sizeof(dispDevice));
dispDevice.cb = sizeof(dispDevice);

DWORD screenID;
while (EnumDisplayDevicesA(NULL, screenID, &dispDevice, 0))
{
    // important: make copy of DeviceName
    char name[sizeof(dispDevice.DeviceName)];
    strcpy(name, dispDevice.DeviceName);

    if (EnumDisplayDevicesA(name, 0, &dispDevice, EDD_GET_DEVICE_INTERFACE_NAME))
    {
        // at this point dispDevice.DeviceID contains a unique identifier for the monitor
    }

    ++screenID;
}

Answer 1

EnumDisplayDevices with the EDD_GET_DEVICE_INTERFACE_NAME flag should give you a usable string. And if not, you can use this string with the SetupAPI to get the hardware id or driver key or whatever is unique enough for your purpose.

Set this flag to EDD_GET_DEVICE_INTERFACE_NAME (0x00000001) to retrieve the device interface name for GUID_DEVINTERFACE_MONITOR, which is registered by the operating system on a per monitor basis. The value is placed in the DeviceID member of the DISPLAY_DEVICE structure returned in lpDisplayDevice. The resulting device interface name can be used with SetupAPI functions and serves as a link between GDI monitor devices and SetupAPI monitor devices.