Re: subclassing Gnome2::Canvas::Text objects

[James Muir <hemlock vtlink net>]

muppet wrote:

> James Muir said:
>  
>
> > Hi Everybody,
> >
> > I see in the FAQ that subclassing Gtk2 widgets is pretty straight
> > forward, but I want to subclass Gnome2::Canvas::Text. I've created a
> > subclass called EllipsisText that simply overrides the "text" method,
> > appending an ellipsis (...) to the text argument.
> >
> > However when I try something like this:
> >
> > local $ellipsisText = Gnome2::Canvas::Item->new($root, 'EllipsisText',
> > x=>10, y=>10, fill_color=>'black',
> >
> >            anchor=>'GTK_ANCHOR_NW', text=$text);
> >
> > I am met with the following error:
> >
> > "EllipsisText is not registered with gperl as an object type blah blah blah"
> >
> > Is what I am trying to do possible?
> >    
>
> You have to use Glib::Object::Subclass to do this type of subclassing, since
> that registers a new GType.  Gnome2::Canvas::Item::new() is a factory that
> keys off of GTypes, so if you don't create a new GType, it doesn't know what
> to do.
>
> Also, there's no "text" method; it's handled purely as a property.  We don't
> support property overrides or redirects (at least, i've never tried), so your
> best bet is to create a new property in your custom class, and implement your
> custom stuff there:
>
>  package EllipsisText;
>  use Glib ':constants';
>  use Glib::Object::Subclass
>      Gnome2::Canvas::Text::,
>      properties => [
>          {
>              pspec => Glib::ParamSpec->string ('ellipsis-text',
>                                                'Ellipsis Text',
>                                                'Text, ellipsized as needed',
>                                                '',
>                                                G_PARAM_READWRITE),
>              # implement this property as preprocessing of the actual
>              # 'text' property of the parent class.
>              get => sub { $_[0]->get ('text') },
>              set => sub {
>                  my ($object, $newval) = @_;
>                  $object->set (text => ellipsize_text ($newval));
>              },
>          },
>      ],
>      ;
>
> You could even have another property that specifies the maximum length, etc.
>
>
>  
This is very slick. Thanks for pointing me in the right direction. -James