As specified in upstream's src/CMakeLists.txt. Configuration aborts on my machine with =net-libs/webkit-gtk-1.8.3-r300 Currently the webkit-gtk dependency only specifies a slot, not the minimum version.
+ 13 Sep 2013; Julian Ospald <hasufell@gentoo.org> geary-0.4.0_pre1.ebuild: + fix webkit-gtk dependency wrt #484632