Since X86_ABI support was added to media-libs/mesa, 32-bit GTK+ programs will fail on an amd64 system if mesa is built with USE=-egl due to missing /usr/lib32/libEGL.so.1, which is referenced by libcairo from emul-linux-x86-gtklibs: $ ldd /usr/lib32/libcairo.so | grep EGL libEGL.so.1 => not found $ equery b /usr/lib32/libcairo.so * Searching for /usr/lib32/libcairo.so ... app-emulation/emul-linux-x86-gtklibs-20131008 (/usr/lib32/libcairo.so.2.11200.14) app-emulation/emul-linux-x86-gtklibs-20131008 (/usr/lib32/libcairo.so -> libcairo.so.2.11200.14) app-emulation/emul-linux-x86-gtklibs (or maybe -opengl?) should depend on media-libs/mesa[egl], or perhaps there should be an EGL virtual along the lines of virtual/opengl. [Random note: Is anyone working on multilib GTK+ ebuilds? I can look into it if not.]
Maybe opengl set should be changed to depend on that (as, with the 32 bits USE enabled it's meant to act like a meta for the transition period) Regarding the migration, help is needed for sure, but a lot of things from gtklibs set still need other things from baselibs to be migrated first. If you want to help you can open bugs with patches and make them block bug 454644
Created attachment 361326 [details, diff] Patch to require mesa[egl] in emul-linux-x86-opengl Trivial, but attaching a patch to emul-linux-x86-opengl-20131008.ebuild in case you want it. Thanks for the note on bug 454644, I'll take a look.
x11-drivers/nvidia-drivers-331.13 and probably also upcoming versions do have 32bit libEGL.so in the upstream package but they are not installed with the current ebuilds. manual installed libs are correctly set with eselect opengl nvidia, so it seems app-admin/eselect-opengl is ready for an updated >=x11-drivers/nvidia-drivers-331.13 ebuild. making app-emulation/emul-linux-x86-gtklibs depend on a virtual egl package, which in turn either depends on mesa[egl] or nvidia-drivers looks like a good idea imho.
The emul-linux-x86 packages have been removed.
