Re: Must widgets stay in context?

[rob page <page rob gmail com>]

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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