Thanks for the information. I think this gives me more questions than it answers.
Murray Cumming wrote: > On Sat, 2008-01-12 at 10:02 -0500, JLM wrote: >> Some widget event handler functions return a boolean value. >> on_expose_event is one. I think the return value is supposed to tell the >> caller whether this widget handled the event or not. > > Yes: > http://www.gtkmm.org/docs/gtkmm-2.4/docs/tutorial/html/sec-xeventsignals.html > >> What exactly does it mean to handle the event? > > It means that no further signal handler will be asked to handle the > event too. > >> For example, I have an on_expose_event function set up for my widget >> that is subclassed from DrawingArea. > > When overeriding, remember also to call the base class's implementation. > Sometimes it does something useful. > Should the base class's function always be called? If not, when should it? I noticed that this isn't followed in the tutorial. The Cairo example (first one I think) does not call the base class in the on_expose_event function. >> It only does something if the >> widget is realized, so I put everything in an if(is_realized()) { ... } >> block. So should I return false if the widget is not realized when this >> function is called? Or is the widget considered to handle the event, but >> it just happens to not do anything? >> >> Are there any rules of thumb for when to return true versus false in >> these cases? > > I have often wondered the same thing in similar situations. I don't > think I have a general answer, but maybe someone else does. I am > generally not a fan of these signals or this technique because I think > it requires you to have a knowledge of what the default implementation > is. If you are not a fan of this technique, then I am curious how you do these things. The recommended techniques in the manual suggests subclassing widgets to better organize your code, so I have done that. I am not sure how to customize the drawing of my new widget without using the on_expose_event function. I'm only doing it this way because it's the only way I know how. If you have a better way, I'm interested in hearing it. > > But that would be the same with the more-traditional C++ technique of > override-and-sometimes-call-the-base-handler. > Thanks again. _______________________________________________ gtkmm-list mailing list [email protected] http://mail.gnome.org/mailman/listinfo/gtkmm-list
