Automatically comment out the touchpad in the xorg.conf if there is an external mouse attached.

comment.touchpad.in.xorg.conf.hs

#!/usr/local/bin/runhaskell
-- Compile with: ghc --make -O2 -optl-s -odir /tmp -hidir /tmp mouse.hs
import Data.List
import Debug.Trace
import Control.Monad
import System.Directory; import System.Environment; import System.IO

{- If there is a USB mouse present in the system, then comment out the touchpad
mouse in "xorg.conf", otherwise uncomment it.
  Note: moused should be disabled (in rc.conf and devd.conf) to free the
/dev/ums0 for Xorg. AutoEnableDevices and AllowEmptyInput should be "false". -}

main =
  (liftM head $ getArgs) >>= \xorg ->
  (liftM lines . readFile) xorg >>= \conf -> length conf `seq`
  doesFileExist "/dev/ums0" >>= \haveUsbMouse ->
  let newConf = (usbmouse haveUsbMouse) . (touchpad (not haveUsbMouse)) $ conf in
  when (newConf /= conf) (writeFile xorg (unlines newConf))

touchpad :: Bool -> [String] -> [String]
touchpad = commentSection "# Touchpad mouse." "EndSection"

usbmouse :: Bool -> [String] -> [String]
usbmouse = commentSection "# USB mouse." "EndSection"

commentSection :: String -> String -> Bool -> [String] -> [String]
commentSection fromEx tillInc onOff conf =
  let (header, tmp) = break (== fromEx) conf in
  let (sec, footer) = break (isSuffixOf tillInc) tmp in
  header ++ [head sec] ++ (commentLines onOff $ (tail sec) ++ [head footer]) ++ (tail footer)

commentLines :: Bool -> [String] -> [String]
commentLines on conf = flip map conf (\line ->
  let commented = "#" `isPrefixOf` line in
  if (on && commented) then tail line
  else if (not on && not commented) then '#' : line
  else line)