Re: a program halts on background and doesn't get the focus back

The magic words for "written in java" are to install wmname (from
suckless-tools) and run

   wmname LG3D

before starting the app.  If that works, it's an ancient thing (about
which I don't know any actual details, just that every so often I've got
some java nonsense to deal with and the above fixes it.)  If not, I
don't have any especially useful suggestions (Xepher or Xnest with a
different wm inside don't really count as *useful*) but maybe someone
else will chime in...