emerge -uDN @world
Calculating dependencies |

!!! Problem resolving dependencies for x11-libs/cairo from @selected
... done!

!!! The ebuild selected to satisfy "x11-libs/cairo" has unmet requirements.
- x11-libs/cairo-1.14.8::gentoo-gpu USE="X glib opengl svg (-aqua) -debug (-directfb) -egl (-gles2) -glx -static-libs -valgrind -xcb -xlib-xcb" ABI_X86="32 (64) (-x32)"

  The following REQUIRED_USE flag constraints are unsatisfied:
    opengl? ( any-of ( egl glx ) )

  The above constraints are a subset of the following complete expression:
    gles2? ( !opengl egl ) opengl? ( any-of ( egl glx ) ) xlib-xcb? ( xcb ) glx? ( opengl )

(dependency required by "@selected" [set])
(dependency required by "@world" [argument])