[Vala] Pango.Attribute questions

[pHilipp Zabel <philipp zabel gmail com>]

Hi,

I'm a bit confused about how Pango.Attribute is supposed to work,
probable because I don't understand ownership issues of [Compact]
classes properly.

I want to set some Pango attributes on a Gtk.CellRendererText, so I tried this:

1:      Pango.AttrList attr_list = new Pango.AttrList ();
2:      Pango.Attribute attr_color = Pango.attr_foreground_new (color.red,
color.green, color.blue);
3:      Pango.Attribute attr_scale = Pango.attr_scale_new (Pango.Scale.SMALL);
4:      attr_list.insert (attr_color);
5:      attr_list.insert (attr_scale);
6:      renderer.attributes = attr_list;

Vala complains with an "error: duplicating Attribute instance, use
unowned variable or explicitly invoke copy method" in lines 2, 3, 4
and 5.
It works when I change the code to look like this:

1:      Pango.AttrList attr_list = new Pango.AttrList ();
2:      unowned Pango.Attribute attr_color = Pango.attr_foreground_new
(color.red, color.green, color.blue);
3:      unowned Pango.Attribute attr_scale = Pango.attr_scale_new
(Pango.Scale.SMALL);
4:      attr_list.insert (attr_color.copy ());
5:      attr_list.insert (attr_scale.copy ());
6:      renderer.attributes = attr_list;

This compiles to the following C code:

1:      attr_list = pango_attr_list_new ();
2:      attr_color = pango_attr_foreground_new (color.red, color.green, color.blue);
3:      attr_scale = pango_attr_scale_new (PANGO_SCALE_SMALL);
4:      pango_attr_list_insert (attr_list, pango_attribute_copy (attr_color));
5:      pango_attr_list_insert (attr_list, pango_attribute_copy (attr_scale));
6:      g_object_set (renderer, "attributes", attr_list, NULL);

Am I not leaking memory for attr_color and attr_scale due to the copy
and the fact that pango_attribute_destroy is never called on either of
them after the copies are made?
I'd expect the correct C code to look something like this:

1:      attr_list = pango_attr_list_new ();
2:      attr_color = pango_attr_foreground_new (color.red, color.green, color.blue);
3:      attr_scale = pango_attr_scale_new (PANGO_SCALE_SMALL);
4:      pango_attr_list_insert (attr_list, attr_color);
5:      pango_attr_list_insert (attr_list, attr_scale);
6:      g_object_set (renderer, "attributes", attr_list, NULL);

regards
Philipp