Greeping in sources doesn't show any references. Final binaries also aren't linked with libXrender.
You're right, this was dropped in 2010: https://git.gnome.org/browse/gtk+/commit/configure.ac?h=gtk-3-22&id=1e706ed64f143599c2c538aa3a14d8d8ae8af805
commit 8f5fa722ae8c53074fa4b2c210febca68b4fb429 Author: Mart Raudsepp <leio@gentoo.org> Date: Sun Mar 5 17:33:51 2017 +0200 x11-libs/gtk+: bump to 3.22.9 and apply various fixes * Stop inheriting eutils - epatch isn't used with EAPI-6 and einstalldocs comes from EAPI-6 itself as well * Remove cairo[svg] comment as it is a required dep since long ago after the bug was filed upstream - it is needed by file print backend (print to file), which is not optional * Adapt to libepoxy changes that made epoxy/glx.h and related source code optional and put it behind a USE flag, bug #611710 * Remove unnecessary libXrender dependency (though cairo[X] will still pull it in), bug #611032 * Remove -O3 to -O2 replacement and strip-flags; apparently people have been doing that with success, so lets give it a chance after issues that happened with -O3 over 10 years ago * Install select docs instead of the default ones, which include an uninteresting README.win32, README.in source file that for some reason is shipped in tarball, README.commits that is interesting for git usage instructions only, and a useless ChangeLog that isn't properly generated anymore. The DOCS array is declared locally in multilib_src_install_all, because gnome2_src_install calls "default" which calls einstalldocs too, which would fail if the DOCS is given in global scope and it sees it, as the docs won't be found in multilib WORKDIR. Gentoo-bug: 611032 Gentoo-bug: 611710
Note that libXrender will still be pulled in with USE=X as before, just indirectly via cairo[X?] dependency, but for correctness this was a good catch, thanks
