I submitted my first patch to Cairo a few weeks back and depressingly it was met with tumbleweed. I tried contacting people on irc but again, nothing.
In contrast I submitted my first patch to fontforge recently too (GitHub) - it was merged in a couple of hours.
Developer interaction matters and I know plenty of open source devs who have put in a lot of good work are going to hate me for saying this - but those old platforms you're using suck for fostering community contributions. (And I thought the code quality in Cairo was great - I bet if it was on GitHub there would be loads more activity)