starting/stopping compositing in xfce4 from the command line

[Micha Feigin <michf@post.tau.ac.il>]

Is it possible to start and stop compositing under xfce4 from the command line?
I trying to use screen rotation with the nvidia plugin and I found out that if
compositing is enabled when rotating the screen then part of it is unusable at
the rotated state (after doing xrandr -o left the I can move the mouse all over
the screen but windows are not shown on the bottom third or so). If I stop and
start compositing (or just stopping is enough) this is fixed. I would like to
write a script that restarts compositing after rotation to fix the issue which
requires command line control

thanks