wndproc:

switch (message)
{
case WM_SYSCOMMAND:
	// Early catch of close action.
	if (wParam == SC_CLOSE) {
		MessageBox(0, "got about-to-close message", 0, 0);
		break; // let defwndproc handle it,
		// you can return 0, and not let closing your app :(
	}
	break;
case WM_CLOSE:
	// The actual close action.
	if (IDYES == MessageBox(0, "quitting?", 0, MB_YESNO)) break;
	// return 0, so it won't quit, in case user chose 'no'.
	return 0;
case WM_DESTROY:
	// cleanup time + tell message loop to quit.
	PostQuitMessage(0);
	break;
}
return DefWindowProc(hWnd, message, wParam, lParam);