Advanced Subclassing

摘要

Whenever you implement an event handler for a C++ window class, when such a window (or window that extends it) gets created on-screen, "subclassing" occurs behind the scenes. If you've programmed nontrivial GUI apps, you're probably familiar with the term. Simply put, if you subclass a window, you get to handle its events first. As Listing 1 shows, whenever you say create_wnd < hyper_link > (par), the hyperlink's event handler gets created and subclassing occurs. Event handlers are inherited. If you extend a window class, you automatically inherit all its event handler(s)—its base class(es), event handler(s), and the like. This makes sense because base class(es) need to implement their logic. In Listing 2, the sample_dlg class automatically inherits the event handler(s) from the dialog class (and its base class(es)) and from the resizable_wnd class (and its base class(es)).