-----------------------------------------------------------------------------
-- |
-- Module      :  XMonadContrib.UpdatePointer
-- Copyright   :  (c) Robert Marlow <robreim@bobturf.org>
-- License     :  BSD3-style (see LICENSE)
-- 
-- Maintainer  :  Robert Marlow <robreim@bobturf.org>
-- Stability   :  stable
-- Portability :  portable
--
-- Causes the pointer to follow whichever window focus changes to. Compliments
-- the idea of switching focus as the mouse crosses window boundaries to
-- keep the mouse near the currently focused window
--
-----------------------------------------------------------------------------

module XMonad.Actions.UpdatePointer 
    (
     -- * Usage
     -- $usage
     updatePointer
    )
    where

import XMonad
import Control.Monad

-- $usage
-- You can use this module with the following in your @~\/.xmonad\/xmonad.hs@:
--
-- > import XMonad
-- > import XMonad.Actions.UpdatePointer
--
-- Enable it by including it in your logHook definition. Eg:
-- 
-- > logHook = updatePointer
-- 
-- which will move the pointer to the nearest point of a newly focused window


-- | Update the pointer's location to the nearest point of the currently focused
-- window unless it's already there
updatePointer ::  X ()
updatePointer = withFocused $ \w -> do
  dpy <- asks display
  root <- asks theRoot
  wa <- io $ getWindowAttributes dpy w
  (_sameRoot,_,w',rootx,rooty,_,_,_) <- io $ queryPointer dpy root
  -- Can sameRoot ever be false in this case? I'm going to assume not
  unless (w == w') $ do
    let x = moveWithin rootx (wa_x wa) ((wa_x wa) + (wa_width  wa))
    let y = moveWithin rooty (wa_y wa) ((wa_y wa) + (wa_height wa))
    io $ warpPointer dpy none root 0 0 0 0 (fromIntegral x) (fromIntegral y)

moveWithin :: Integral a => a -> a -> a -> a
moveWithin current lower upper =
    if current < lower
    then lower
    else if current > upper
         then upper
         else current