xmonad-config/lib/DBus/Screensaver.hs

{-# LANGUAGE OverloadedStrings #-}

--------------------------------------------------------------------------------
-- | DBus module for X11 screensave/DPMS control

module DBus.Screensaver
  ( exportScreensaver
  , callToggle
  , callQuery
  , matchSignal
  ) where

import           Control.Monad             (void)

import           DBus
import           DBus.Client
import           DBus.Internal

import           Graphics.X11.Xlib.Display
import           Graphics.X11.XScreenSaver

import           Shell

import           XMonad

--------------------------------------------------------------------------------
-- | Low-level functions

type SSState = Bool -- true is enabled

toggle :: IO SSState
toggle = do
  st <- query
  -- TODO figure out how not to do this with shell commands
  spawn $ fmtCmd "xset" $ "s" : args st
  -- TODO this assumes the command succeeds
  return $ not st
  where
    args s = if s then ["off", "-dpms"] else ["on", "+dpms"]

query :: IO SSState
query = do
  dpy <- openDisplay ""
  xssi <- xScreenSaverQueryInfo dpy
  closeDisplay dpy
  return $ case xssi of
    Just XScreenSaverInfo { xssi_state = ScreenSaverDisabled } -> False
    Just XScreenSaverInfo { xssi_state = _ }                   -> True
    -- TODO handle errors better (at least log them?)
    Nothing                                                    -> False

--------------------------------------------------------------------------------
-- | DBus Interface
--
-- Define a methods to toggle the screensaver. This methods will emit signal
-- with the new state when called. Define another method to get the current
-- state.

path :: ObjectPath
path = "/screensaver"

interface :: InterfaceName
interface = "org.xmonad.Screensaver"

memState :: MemberName
memState = "State"

memToggle :: MemberName
memToggle = "Toggle"

memQuery :: MemberName
memQuery = "Query"

sigCurrentState :: Signal
sigCurrentState = signal path interface memState

ruleCurrentState :: MatchRule
ruleCurrentState = matchAny
  { matchPath = Just path
  , matchInterface = Just interface
  , matchMember = Just memState
  }

emitState :: Client -> SSState -> IO ()
emitState client sss = emit client $ sigCurrentState { signalBody = [toVariant sss] }

bodyGetCurrentState :: [Variant] -> Maybe SSState
bodyGetCurrentState [b] = fromVariant b :: Maybe SSState
bodyGetCurrentState _   = Nothing

-- | Exported haskell API

exportScreensaver :: Client -> IO ()
exportScreensaver client =
  export client path defaultInterface
    { interfaceName = interface
    , interfaceMethods =
      [ autoMethod memToggle $ emitState client =<< toggle
      , autoMethod memQuery query
      ]
    }

callToggle :: IO ()
callToggle = void $ callMethod $ methodCall path interface memToggle

callQuery :: IO (Maybe SSState)
callQuery = do
  reply <- callMethod $ methodCall path interface memQuery
  return $ reply >>= bodyGetCurrentState

matchSignal :: (Maybe SSState -> IO ()) -> IO SignalHandler
matchSignal cb = addMatchCallback ruleCurrentState $ cb . bodyGetCurrentState