Intercept WM_CLOSE for cleanup operations

Question

I have an external application that calls my application and is supposed to end it when the job is done. The log from this external application claims it uses WM_CLOSE

Answer 1

The easiest way I think is to call PeekMessage from time to time.

BOOL IsCloseEventReceived()
{
    MSG msg;
    return PeekMessage(&msg, NULL, WM_CLOSE, WM_CLOSE, PM_NOREMOVE);
}

This function should work to check if a WM_CLOSE message has been posted. It's not blocking, and you'll need to call it on a regular basis.

I might be wrong, but I think you don't need a hidden window to handle messages, a message queue is attached to your process the first time you call a messages-related function, like PeekMessage. However if you receive a WM_CLOSE message prior to your first call of this function it might be lost.