I didn't find the gtk2 library on the ubuntu repositories and searching with 
google was not successful. So I downloaded the source code on sourceforge and 
tried to compile. The first step of the process : ruby extconf.rb output an 
empty file because gobject-2.0, gdk-pixbuf-2.0, pango, atk, gthread-2.0, 
gtk+-2.0 were not found. Perhaps, compiling gtk would solve this problem, and 
probably bring others. So, please help.

Best,
Michel