Check if display is turned off by windows power management

Question

How can I programmatically check in Windows 7 and XP if 'windows power management' has turned off the display? (If I can receive an event, that would be even better.)

Answer 1

I don't think it can be done for XP. In Windows 7 there are all kinds of goodies related to power management. The Windows API Code Pack is a set of managed wrappers that are simple to call from C# or VB and that map Windows paradigms (like event sinks, Windows messages and function pointers) into .NET ones (like delegates and events.) From the Power Management Demo that comes with the code pack, here is some code you might like:

using Microsoft.WindowsAPICodePack.ApplicationServices;

// . . .
        PowerManager.IsMonitorOnChanged += new EventHandler(MonitorOnChanged);
// . . .
    void MonitorOnChanged(object sender, EventArgs e)
    {
        settings.MonitorOn = PowerManager.IsMonitorOn;
        AddEventMessage(string.Format("Monitor status changed (new status: {0})", PowerManager.IsMonitorOn ? "On" : "Off"));
    }

Edit:

Links to Windows API Code Pack: Windows API Code Pack: Where is it?

If you want use it just like is mentioned in this post check this: https://stackoverflow.com/a/27709672/846232

Answer 2

Your application will get a WM_SYSCOMMAND message with SC_MONITORPOWER in wParam (make sure to and wParam with 0xfff0 first). It will send a similar message when the screen saver kicks in (SC_SCREENSAVE). If your goal is preventing the screen to turn off you can return 0 on these, although that doesn't work when the user has a password set.