Re: subclassing Gnome2::Canvas::Text objects

["muppet" <scott asofyet org>]

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.


-- 
muppet <scott at asofyet dot org>