Thread: Receiving a notification after resuming from sleep state

Hi,

I'm looking for a way of launching a small executable every time a computer resumes from sleep state (this is for a laptop, i want to do some stuff every time the lid is open and every time the computer is started). I know how to add a program for it to be run every time windows start, but i'm completely lost on if there's a way for a program to be notified when the computer resumes from the sleep state or some things like that.

I did some search on the internet, but it was unsuccessful.

Thanks

Check out WM_POWERBROADCAST on MSDN. Which means you'll need to have a app running to recieve the message in the first place.

gg

Thanks. I got something working.

I have another question. I really don't know much about Windows programming in general, and this being said, the only way i managed to make my program work is by creating a window (that i never show) so it can handle the WM_POWERBROADCAST message (else, i wasn't able to receive the message (or maybe i just did something wrong )). But this is rather ugly, and i would prefer not creating a window (even if we don't see it). So... is there something easy to do about this ?

Well - you don't need a window to have a message queue. And even though the documentation says "A window receives this message through its WindowProc function" - the message may just show up in a message queue not associated with any windows. It's worth a quick try anyways...

Code:

    MSG msg;
    BOOL bRet;
    for (;;)
    {
        bRet = GetMessage(&msg, 0, 0, 0);
        if ((bRet == 0) || (bRet == -1))
            break;

        // check message here

    }//while

Indeed, in my first try, i wasn't creating any windows and i wasn't either receiving the message. Maybe i did some errors while writing the code. But it was looking like

Code:

// ...
MSG msg;
while (GetMessage(&msg, NULL, 0, 0) > 0)
{
   if (msg.message == WM_POWERBROADCAST)
   {
      if (msg.wParam == PBT_APMRESUMESUSPEND)
      {
         MessageBox(...);
      }
   }
}

Never received the notification after re-opening the lid of my laptop. The other version where i create a window does work.

But i might retry eventually. I'll give some feedback about it.

And i read this on MSDN: "Because the system directs messages to individual windows in an application, a thread must create at least one window before starting its message loop.". Don't know what we can conclude from it.

Anyway. Thanks for the help.