gtk+-2.6.0 was released on December 16, and works fine here.
Created attachment 46511 [details] gtk+-2.6.0.ebuild Ebuild, derived from gtk+-2.4.14; the RDEPENDs have been updated, and the smoothscroll patch has beeen commented out (unfortunately, it seems to be incompatible with gtk+-2.6.0 without some reworking; for instance, the way gtk_range_scroll_event() works has changed a bit since 2.4.x)
that is a regression and should be fixed first & this is a dupe afaic *** This bug has been marked as a duplicate of 74683 ***