Switch Primary Monitor in Ubuntu 10.4

The default Monitor Preferences dialog, while sweet, does not allow you to make your secondary monitor your primary. This is a problem if you want the top and bottom Ubuntu Panels displayed on the secondary monitor. Thankfully I found this sweet little script.

#!/bin/sh
#
# Change Primary Monitor for Gnome
# ver 1.0
# 
# Copyright (c) 2010 michal@post.pl
# 
# This file is free software. You can redistribute it 
# and/or modify it under the terms of the GNU
# General Public License (GPL) as published by
# the Free Software Foundation, in version 3.
# It works for me. I hope it works for you as well.
# NO WARRANTY of any kind. 
#


# get list of top-level gnome panels
getTopPanels() {
 gconftool-2 --all-dirs /apps/panel/toplevels
}

# get monitor number for this panel
getMonitor() {
 local PANEL=$1
 gconftool-2 --get $PANEL/monitor
}

# set monitor to display on for given top-level panel
setMonitor() {
 local PANEL=$1
 local NEW=$2
 gconftool-2 --set --type int $PANEL/monitor $NEW
}

# return number of connected monitors
getConnectedMonitors() {
 xrandr --query | grep -c '^.* connected'
}

# compute next monitor
nextMonitor() {
 # number of monitors
 local CURRENT=$1
 local MONITORS=$2
 awk 'BEGIN{ print ('$CURRENT' + 1) % '$MONITORS'; }'
}

# logging finction
log() {
 echo $@ 1>&2
}

# main logic below #############

MONITORS=`getConnectedMonitors`
log "Detected $MONITORS connected monitors"

getTopPanels | while read PANEL
do
 MONITOR=`getMonitor $PANEL`
 NEW=`nextMonitor $MONITOR $MONITORS`
 log "Panel $PANEL is displayed on $MONITOR. Switching to monitor $NEW."
 setMonitor $PANEL $NEW
done