Created attachment 282135 [details]
While emerging =dev-libs/libunique-3.0.2, I got test failures with it unable to open a display. Thanks to ABCD's help on IRC, I discovered that installing Xvfb on the host resolved this.
Attached patch for virtualx.eclass provides this information to end users.
This is my first eclass patch, so its style may not be what's desired/required; please feel free to make any changes necessary. :)
unfortunately the eclass has changed considerably since