I just tested it, it builds, it works. You definitely don't want to install gtk2 *AND* 3 just to run the xfce panel. It should be configurable via a use flagm and link to either version. Reproducible: Always Steps to Reproduce: 1. keywords xfce4-panel-4.11.x for your ~arch 2. emerge it in a gtk+3-less system 3. watch it pull yet another gtk+ version into your system Expected Results: It only needs one of the gtk+'s to run, it shouldn't pull in both of them. Upstream has just release "initial support for gtk+-3", as I see it, it shouldn't be either necessary nor the default toolkit. In any case, I am pretty sure a lot of Gentoo users would welcome the possibility to continue using their panels without gtk+3 once 4.11.x is stabilized.
*** This bug has been marked as a duplicate of bug 374057 ***