yeah, i know, my problem is not related to cairo.
i installed rcairo, so that message is gone now.

Masao Mutoh wrote:
Hi,

Ruby/Cairo is not a part of Ruby-GNOME2 project.

See:
http://www.cairographics.org/
http://www.cairographics.org/rcairo

On Wed, 23 Aug 2006 10:02:56 +0300
Dobai-Pataky Balint <dpblnt@gmail.com> wrote:

  
i installed 0.15.0, and when requiring gtk2 i get the following error:

Exception `LoadError' at 
/usr/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:35 - no such file 
to load -- cairo
/usr/lib/ruby/site_ruby/1.8/glib2.rb: line 55
   GLib-GObject-CRITICAL **:g_boxed_type_register_static: assertion 
`g_type_from_name (name) == 0' failed
Aborted

there is no cairo in ruby-gnome2-all-0.15.0, so i don't get this.

i searched the net, and found on this thread 
http://mail.gnome.org/archives/gtk-perl-list/2005-December/msg00012.html
that there is a libgnomecanvas problem. my libgnomecanvas did not 
change, it's 2.14.0: 
http://ftp.gnome.org/pub/gnome/sources/libgnomecanvas/2.14/

i use gentoo, gtk+-2.10.1, gnome-desktop-2.15.92