Is there any way to detect the monitor state in Windows (on or off)?

Question

Does anyone know if there is an API to get the current monitor state (on or off) in Windows (XP/Vista/2000/2003)?

All of my searches seem to indicate there is no real way of doing this.

This thread tries to use GetDevicePowerState which according to Microsoft's docs does not work for display devices.

In Vista I can listen to GUID_MONITOR_POWER_ON but I do not seem to get events when the monitor is turned off manually.

In XP I can hook into WM_SYSCOMMAND SC_MONITORPOWER, looking for status 2. This only works for situations where the system triggers the power off.

The WMI Win32_DesktopMonitor class does not seem to help out as well.

Edit: Here is a discussion on comp.os.ms-windows.programmer.win32 indicating there is no reliable way of doing this.

Anyone else have any other ideas?

Answer 1

What will you be using this information for?

Have you considered the case where the monitor is on but is not connected to the display card?

Answer 2

GetDevicePowerState sometimes works for monitors. If it's present, you can open the \\.\LCD device. Close it immediately after you've finished with it.

Essentially, you're out of luck -- there is no reliable way to detect the monitor power state, short of writing a device driver and filtering all of the power IRPs up and down the display driver chain. And that's not very reliable either.

Answer 3

Of course it's possible. There are several standard methods

You can ask on Win32 api newsgroup : news://194.177.96.26/comp.os.ms-windows.programmer.win32 where it has often been discussed

Answer 4

Before doing anything based on the monitor state, just remember that users can use a machine with remote desktop of other systems that don't require a monitor connected to the machine - so don't turn off any visualization based on the monitor state.

Answer 5

Look like all monitor power capabilities connected to the "power safe mode"
After searching i found here code that connecting between SC_MONITORPOWER message and system values (post number 2)
I use the code to testing if the system values is changing when i am manually switch off the monitor.

int main()
{
    for(;monitorOff()!=1;)
        Sleep(500);
    return 0;
}//main

And the code is never stopped, no matter how long i am switch off my monitor.
There the code of monitorOff function:

int monitorOff()
{
    const GUID MonitorClassGuid =
        {0x4d36e96e, 0xe325, 0x11ce, 
            {0xbf, 0xc1, 0x08, 0x00, 0x2b, 0xe1, 0x03, 0x18}};

    list<DevData> monitors;
    ListDeviceClassData(&MonitorClassGuid, monitors);

    list<DevData>::iterator it = monitors.begin(),
                            it_end = monitors.end();
    for (; it != it_end; ++it)
    {
        const char *off_msg = "";

        //it->PowerData.PD_PowerStateMapping
        if (it->PowerData.PD_MostRecentPowerState != PowerDeviceD0)
        {
            return 1;
        }
    }//for

    return 0;
}//monitorOff

Conclusion : when you manually switch of the the monitor, you cant catch it by windows (if there is no unusual driver interface for this), because all windows capabilities is connected to "power safe mode".

Answer 6

I don't see why you are so against telling us why you want to do that. There is a good chance that what you want to acomplish can be done in another fashion without the monitor involved at all.

For example, you can detect if the screen saver is active or if the workstation is locked.

HOW TO: Determine If Screen Saver Is Running

Detecting Windows/Workstation Locked / Unlocked in .NET

Answer 7

You could hook up a webcam, point it at your screen and do some analysis on the images you receive ;)

Answer 8

If this can be done, I'm not sure how you are going to solve the next problem of ensuring someone is actually looking at the monitor.

Answer 9

Hi,

In Windows XP or later you can use the IMSVidDevice Interface.

See http://msdn.microsoft.com/en-us/library/dd376775(VS.85).aspx

(not sure if this works in Sever 2003)