xrandr_toggle.rb

#!/usr/bin/ruby
output = `xrandr`
lvds = output[/LVDS connected.*mm/]
dfp1 = output[/DFP1 connected.*mm/]

if lvds && dfp1
  status = "(both)"
  options = "lvds\ndfp1"
elsif lvds
  status = "(lvds)"
  options = "dfp1\nboth"
elsif dfp1
  status = "(dfp1)"
  options = "lvds\nboth"
end

setup_lvds = 'xrandr --output LVDS --left-of DFP1 --mode 1366x768'
setup_dfp1 = 'xrandr --output DFP1 --right-of LVDS --mode 1440x900'

case `echo "#{options}" | dmenu -p "#{status}"`
when "lvds"
  `#{setup_lvds} && xrandr --output DFP1 --off`
when "dfp1"
  `#{setup_dfp1} && xrandr --output LVDS --off`
when "both"
  if lvds
    `#{setup_dfp1}`
  else
    `#{setup_lvds}`
  end
end

`nitrogen --restore` # reset wallpapers