# Blockers when subclassing Gtk::Container

**URL:** <https://www.ruby-forum.com/t/blockers-when-subclassing-gtk-container/112474>\
**Category:** Ruby-Gnome 2\
**Created:** [August 20, 2007, 12:30am UTC](https://www.ruby-forum.com/t/blockers-when-subclassing-gtk-container/112474 "2007-08-20T00:30:17Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![wo\_boo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/f475e1/32.png) [@wo\_boo](https://www.ruby-forum.com/u/wo_boo)\
**Post date:** [August 20, 2007, 12:30am UTC](https://www.ruby-forum.com/t/blockers-when-subclassing-gtk-container/112474/1 "2007-08-20T00:30:17Z")

</div>

When subclassing Gtk::Container I’ve found that overriding “abstract”  
methods seems to go unnoticed by the underlying gtk system…

When I override Gtk::Container#add and do child.parent=self inside it I  
get  
this:

/usr/lib64/ruby/site\_ruby/1.8/rubygems/custom\_require.rb: line 27  
Gtk-WARNING \*\*:GtkContainerClass::add not implemented for `FooTest’

This message is generated by the “abstract” add method  
(gtk\_container\_add\_unimplemented()) in gtkcontainer.c and it tells me  
that  
Ruby-GNOME2 has not updated these function pointers when I call  
type\_register in the ruby class definition of FooTest.

Likewise, it seems that my overridden Gtk::Container#size\_allocate and  
Gtk::Container#size\_request methods are not called by my FooTest  
object’s  
parent.

I’ve attempted to hunt down this problem myself, but I’m not sure where  
to  
go next; I’ve noticed that the only two implementations of type\_register  
are  
found in the C code for GLib::Object and Gtk::Container and that there  
are  
only subtle differences in how they function. I’m pretty sure it’s meant  
to  
either update the function pointers or install some hook that update  
function pointers when abstract methods are added to a Gtk::Container  
subclass, but I can’t find evidence that this has even been implemented  
yet?

---

<div class="post-metadata">

**Author:** ![wo\_boo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/f475e1/32.png) [@wo\_boo](https://www.ruby-forum.com/u/wo_boo)\
**Post date:** [August 24, 2007, 9:49am UTC](https://www.ruby-forum.com/t/blockers-when-subclassing-gtk-container/112474/2 "2007-08-24T09:49:05Z")

</div>

On 8/20/07, wo boo [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> This message is generated by the “abstract” add method  
> (gtk\_container\_add\_unimplemented()) in gtkcontainer.c and  
> it tells me that Ruby-GNOME2 has not updated these function pointers when I  
> call type\_register in the ruby class definition of FooTest.

Can you paste your FooTest code somewhere?

–  
Guillaume C. - [Guillaume Cottenceau](http://zarb.org/~gc/)

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---

<div class="post-metadata">

**Author:** ![wo\_boo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/f475e1/32.png) [@wo\_boo](https://www.ruby-forum.com/u/wo_boo)\
**Post date:** [August 28, 2007, 8:37pm UTC](https://www.ruby-forum.com/t/blockers-when-subclassing-gtk-container/112474/3 "2007-08-28T20:37:25Z")

</div>

Hi again. Digging through the mailing list for an answer to my problem,  
I  
found the “treemodel” discussion from mid-July 2007. Can anyone confirm  
or  
deny my suspicion that my problem extending Gtk::Container is related to  
this? That is, overriding any existing method for a native GTK class  
will  
leave it in some “meta state” where Ruby code calling Gtk::Container#add  
will (in the correct manner) call the overridden Ruby method, but any  
GTK  
library C code doing gtk\_container\_add() on the same object will instead  
get  
the super-method - the native method for the GTK class?

I’m very interested in finding a general solution for this and possibly  
help  
implementing it. The “treemodel” thread also mentioned that there were  
problems with the Ruby garbage collector. Can anyone elaborate on this?  
I  
don’t see how overriding methods is a lot different from installing  
signal  
handlers, which seems to work just fine. In both cases Ruby-GNOME2 will  
callback to Ruby code based on something that happens internally in the  
native GTK library.

---

<div class="post-metadata">

**Author:** ![wo\_boo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/w/f475e1/32.png) [@wo\_boo](https://www.ruby-forum.com/u/wo_boo)\
**Post date:** [August 27, 2007, 4:13pm UTC](https://www.ruby-forum.com/t/blockers-when-subclassing-gtk-container/112474/4 "2007-08-27T16:13:40Z")

</div>

I’ve posted an example of subclassing Gtk::Container that does not work,  
here:

[http://pastebin.com/f1171f0ee](http://pastebin.com/f1171f0ee)

and here it is in plain text:

require ‘gtk2’

class Foo \< Gtk::Container  
type\_register  
def initialize  
super()  
set\_flags Gtk::Widget::NO\_WINDOW  
end  
def add child  
# !! following code generates this warning: “Gtk-WARNING  
\*\*:GtkContainerClass::add not implemented for `Foo’”  
child.parent = self  
end  
def size\_allocate  
# this method should be called by gtk subsystem, but it isn’t  
puts “called size\_allocate”  
end  
def size\_request  
# this method also should be called by gtk subsystem, but it  
isn’t  
puts “called size\_request”  
end  
end

class App \< Gtk::Window  
def initialize  
super()  
foo = Foo.new

```
    button = Gtk::Button.new("hello")
    foo.add button

    add foo
end

```

end

app = App.new  
app.show\_all  
Gtk.main