For gtk, I saw a compile error about cairo. Emerged cairo and that went away, and then the next error I saw that there was a function called gdk_screen_get_rgba_colormap that was undefined, a search on Google revealed that this function is new for gtk 2.8 (but seems to be used only if cairo is defined). Ebuild does not have cairo keyword, and if cairo is defined, it should require gtk 2.8.
Why just don't you paste the exact errors and emerge --info, it would make searching for duplicate bugs *so* much easier...
