dev-ruby/ruby-pango-2.0.2, 2.1.0, 2.2.0 depends on >=dev-ruby/rcairo-1.2.0 now, but it should be >=dev-ruby/rcairo-1.12.5 since ruby-pango-2.0.1. https://github.com/ruby-gnome2/ruby-gnome2/blob/2.0.1/pango/Rakefile For example, ruby-pango-2.2.0[ruby20] with rcairo-1.10.2-r1 fails to compile. checking for new allocation framework... yes checking for attribute assignment... no checking for rb_errinfo() in ruby.h... yes checking for cairo... yes checking for rb_cairo.h... no *** /var/tmp/portage/dev-ruby/ruby-pango-2.2.0/work/ruby20/ruby-gnome2-all-2.2.0/pango/ext/pango/extconf.rb failed *** Could not create Makefile due to some reason, probably lack of necessary libraries and/or headers. Check the mkmf.log file for more details. You may need configuration options.
Fixed for the ruby-pango-2.x versions. Thanks for the report.