Behind the connection: Subclassing a window

Subclassing a window What is it? Subclassing a window is the process of intercepting all calls to the window procedure of a given window. When you subclass a window, you can get hand on every message sent/posted to the window you’ve subclassed. Why subclass? Why would you want to subclass a window ? For example if a windows does almost everything you want, but you need a few more