On Mon, 2016-02-08 at 10:18 +1300, Ian Martin wrote: > Correct me if I'm wrong, but doesn't Gtk::manage work more like a > shared > pointer? i.e. maintain a count of the references to the object, > deleting > the object pointed to when the ref count goes to zero.
Not quite. GObject has simple reference-counting. But widgets have actual ownership by container widgets, with some reference-counting thrown in to confuse things. But in the end, containers can choose when to destroy their child widgets. Calling Gtk::manage() means "let the container destroy this", or more fundamentally, it means "I am giving away the ownership". > As you've said, using unique_pointer mandates a design with only one > access point to the controlled object, I don't think that's quite true. You can get (a pointer to) the widget back from its container widget. > and there's plenty of interesting > things you may want to do to widgets after construction. You'd call std::move() when giving the ownership to the container widget, not right after construction. I like the explicit handing over of ownership of std::move()ing a std::unique_ptr<> and I like that I'm encouraged to do that when I've finished with the setup of the object. > We use > Gtk::manage() freely because it keeps track of widget memory use for > us, > but doesn't control access to it within the code. The intent is similar with std::unique_ptr<> and std::move(), but it's a general and standardized technique. > One option might be to provide 2 variants for Gtk::manage(); one > using > shared_pointer semantics and one using unique_pointer, with a default > to > shared (because it'd be backwards compatible). > > It's also considered wise to receive a std::unique_ptr as a > > parameter > > if the method really plans to take ownership. For instance: > > void Foo::take_thing(std::shared_ptr<Thing> thing); > I think you've typed std::shared_ptr<Thing> when you meant > std::unique_ptr<Thing> ? Yes, sorry. -- Murray Cumming murr...@murrayc.com www.murrayc.com _______________________________________________ gtkmm-list mailing list gtkmm-list@gnome.org https://mail.gnome.org/mailman/listinfo/gtkmm-list
