Re: Must widgets stay in context?

[Karen Pease <meme DaughtersOfTiresias org>]

Wow, that has to be the fastest (working!) response I ever had to a problem.  
You guys are great  :)

	- Karen

On Wednesday 14 December 2005 02:22 pm, you wrote:
> I believe you want to be using Gtk::manage
>
> advbox->add(*Gtk::manage(new class Gtk::Label(_("Misc Settings"))));
>
> (code ripped from one of my programs)
>
> which should be much easier to use dynamically.
>
> Rob.
>
> On 14/12/05, Karen Pease <meme daughtersoftiresias org> wrote:
> > Hi - I'm new to gtkmm, and still just starting to get my feet wet.  I'm a
> > bit confused by something and can't find information in the documentation
> > about it - namely, must widgets stay in context after they're added to a
> > container? gtkmm forbids, say:
> >
> > some_frame.add(Gtk::Label("Test"));
> >
> > because it wants a Gtk::Label&, not a Gtk::Label.  Most sample code that
> > I've seen have a member variable (say, m_label_test) used like:
> >
> > SomeClass::SomeClass() : m_label_test("Test")
> > {
> >    some_frame.add(Gtk::Label("Test"));
> > }
> >
> > This seems to suggest to me that gtk cares whether the widget goes out of
> > context or not - that it's not copying the widget that I gave it, but
> > referencing it by pointer.  And thus, it would seem to suggest that this
> > is unacceptable:
> >
> > some_function()
> > {
> >     Gtk::Label label_test("Test");
> >     some_frame.add(label_test);
> > }
> >
> > If I am correct in this, then how do I deal with a situation in which
> > what widgets are used is dynamic?  In my application, I have an
> > information frame which can display information about any one of a wide
> > range of possible objects in a scene, and each object will display
> > different kinds of information about itself (it's not the same type of
> > information between different objects - a wire may list its current,
> > voltage, resistance, conductor material, conductor diameter, etc; a
> > vehicle may list its velocity, wind resistance, drag coefficient,
> > G-forces, mass, etc).
> >
> > Do I have to have a member variable widget for every last label
> > possibility even though at any given time the vast majority of them will
> > be unused?  That would be a pain, at least as far as labels go.  I tried
> > creating std::vector<Gtk::Label> label_list to store any widgets that got
> > created, but that didn't work.  Gtk::Label's copy constructor is private,
> > so
> > label_list.push_back(Gtk::Label(text)) fails.  Right now I'm using a
> > roundabout hack, using a std::vector<Gtk::Label*>, filling it with
> > label_list.push_back(new Gtk::Label(text)), deferencing the pointers when
> > I add them to the frame, and using a cleanup function that deallocates
> > everything in label_list when it is no longer used.  Needless to say,
> > this is ugly.  Is there a better way?
> >
> > Thanks for your help!
> >
> >         - Karen
> >
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