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 ?

Nope. That's just how Windows works.

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

---

It might just work that way since you would get it before it's send to the window proc...
The actual message should be in the msg variable, in the MSG struct.
It doesn't hurt to try.

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. :)

From what I understand, Windows creates and sends messages to windows. So if you don't have a window, no message is created and sent to your application.
If you do create a window, however, it will automatically begin sending notifications to your window. You could actually intercept them in your message loop after creating the window if you want, but you could just as well use the actual window proc.