Gnuplot on ubuntu



Hello everyone,
maybe mine is a silly problem but I can not figure it out: if I try to 
plot something from wxMaxima (e.g. plot2d(sin(x), [x, -2*%pi, 2*%pi]);) 
the gnuplot window appears correctly but I cannot use zoom controls or 
scroll controlls (i.e. shift+mouse-wheel, ctrl+mouse-wheel). Instead if 
I open a terminal, launch gnuplot and write plot sin(x); everything 
works fine. Any idea?

Best regards,
Michele M.