Like many applications, mine creates multiple windows. I do not know and cannot keep track of how many windows have been created, so I don't know when there are none.
My problem is that when all the windows are closed, unless I call PostQuitMessage somehow, the application keeps running with no windows open (obviously). I can't call PostQuitMessage in the message handler in response to the WM_DESTROY message because that will close all the windows when the first one is closed, even if there are twenty others still open.
My question is how do I know when to call PostQuitMessage(0) to actually terminate the application?
Just keep a static variable with a count of the number of open windows. When a windows opens have it increment the counter; in the WM_DESTROY handler decrement it. When the count goes to zero, call PostQuitMessage.