Thread: Handling WM_CLOSE and WM_DESTROY

No. The only difference is the 1st sends 12 and the second sends 0.

The param of PostQuitMessage() is only used if your message pump (Peek/GetMessage) actually looks at the wParam.

IIRC technically you are required to return an int to the OS, zero for success or an application defined error code, so sending 12 (WM_QUIT == 0x0012) is not correct (if you actually use the wParam of the WM_QUIT msg in the msg pump).

The WM_CLOSE message (which is also sent by the X on the window frame) is intended to give you a chance to save settings etc. before exiting.

Also note that if you return TRUE or 1, you can prevent the application from closing.

Code:

case WM_CLOSE :
  SaveSettings();
  PlayExitNoise();
  if (MessageBox(hWindMain,"Do you want to quit", "Exit", MB_YESNO | MB_ICONWARNING) == IDOK)
    { DestroyWindow(hWindMain);
      return 0; }
  else
    return 1;

The WM_DESTROY message is the last thing on the way out the door, so that's where you PostQuitMessage()...

For most programs PostQuitMessage(0) is perfectly adequate.

Code:

case WM_DESTROY:
	PostQuitMessage(WM_QUIT);
	return 0;

Not that it's technically wrong, but I guess tutorial writers go against the grain of 0 just so they can see who's copying the code.

Originally Posted by novacain

so sending 12 (WM_QUIT == 0x0012)

That's 18. I'd go look at your contract, maybe they're not really paying you all that for MFC after all

Originally Posted by adeyblue

That's 18. I'd go look at your contract, maybe they're not really paying you all that for MFC after all

Typos, I test code for them, not forum posts.

I investigated an incident where 2 3km long trains fitted with my prototype data recorders collided head on. It cost the company over Au$100 million in damage and lost production (it would have been about Au$30 mill less if the crane driver had not dropped one of the locos when putting them back on track).

Turned out the cause was a typo, someone put a 2 (instead of a 3) in a track based transponder (that told the loco's Automated Train Protection system where it was on the track).