It changes certain properties of the window identified by Windows handle hWnd. Most frequently used flags are:
- GWL_STYLE, GWL_EXSTYLE -- changes window styles, such as border, caption, child/popup etc. See CreateWindow(Ex)entries for full list.
- GWL_WNDPROC -- changes the window procedure -- the function which handles all the messages for the window. This technique is called "subclassing". See POKER sample for illustration.
- GWL_USERDATA -- associates (a pointer to) arbitrary data with the given window. This provides some kind of OOP. For example, in a MDI application, you can associate your own data structure which will keep its contents with every open child window; behaviour (window procedure) of all windows is the same, but data displayed in them are different.
Jugoslav
