This version of synaptics is unmasked for ~x86 but that version of xfree does not exist. I've installed it here over my -r3 and it appears to work fine... Is the -r4 requirement appropriate? Calculating world dependencies \ !!! all ebuilds that could satisfy ">=x11-base/xfree-4.3.0-r4" have been masked. !!! (dependency required by "x11-misc/synaptics-0.12.1" [ebuild])
Please look at the bug I'm marking this a duplicate of. *** This bug has been marked as a duplicate of 34201 ***