x11-libs/libxkbcommon does not need dependencies on x11-proto/xproto or x11-proto/kbproto. They are not checked for in libxkbcommon's configure, and none of the headers they install are used by libxkbcommon. This is true even when installed with USE="+X" (although in that case libxkbcommon depends on libxcb, which will bring in xproto).
Created attachment 441448 [details] libxkbcommon-0.6.1.ebuild
Failed to configure for me without xproto/kbproto. This works for you?
Yes, this works for me. I even updated it to 0.7.1 (no changes needed) and it continues working. What error do you get from configure?
(forgot to take this off of needinfo when I responded)
(In reply to dolphinling from comment #4) > (forgot to take this off of needinfo when I responded) Must have been a PEBKAC :) You are right. Fixed by: commit fc2569837710e0cc981421473b313d4fae71c326 Author: Matt Turner <mattst88@gentoo.org> Date: Fri Mar 3 23:10:46 2017 -0800 x11-libs/libxkbcommon: Depend on xproto and kbproto only for USE=X