Prefer safe alternatives to getWindowAttributes

Whenever possible, prefer the safe wrappers withWindowAttributes or
safeGetWindowAttributes to getWindowAttributes.

Places where these are not applicable are limited to layouts, where
there is not good "default value" to give back in case these calls fail.
In these cases, we let the exception handling of the layout mechanism
handle it and fall back to the Full layout.

Fixes: https://github.com/xmonad/xmonad-contrib/issues/146

XMonad/Layout/LayoutHints.hs

@@ -1,6 +1,7 @@
 {-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
 {-# LANGUAGE ParallelListComp, PatternGuards #-}
 {-# LANGUAGE TupleSections #-}
+{-# LANGUAGE LambdaCase #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module       : XMonad.Layout.LayoutHints
@@ -32,8 +33,8 @@ import XMonad(LayoutClass(runLayout), mkAdjust, Window,
               Dimension, Position, Rectangle(Rectangle), D,
               X, refresh, Event(..), propertyNotify, wM_NORMAL_HINTS,
               (<&&>), io, applySizeHints, whenX, isClient, withDisplay,
-              getWindowAttributes, getWMNormalHints, WindowAttributes(..))
-import XMonad.Prelude (All (..), fromJust, join, maximumBy, on, sortBy)
+              getWMNormalHints, WindowAttributes(..))
+import XMonad.Prelude
 import qualified XMonad.StackSet as W
 
 import XMonad.Layout.Decoration(isInStack)
@@ -264,8 +265,9 @@ hintsEventHook _ = return (All True)
 
 -- | True if the window's current size does not satisfy its size hints.
 hintsMismatch :: Window -> X Bool
-hintsMismatch w = withDisplay $ \d -> io $ do
-    wa <- getWindowAttributes d w
-    sh <- getWMNormalHints d w
-    let dim = (fromIntegral $ wa_width wa, fromIntegral $ wa_height wa)
-    return $ dim /= applySizeHints 0 sh dim
+hintsMismatch w = safeGetWindowAttributes w >>= \case
+    Nothing -> pure False
+    Just wa -> do
+        sh <- withDisplay $ \d -> io (getWMNormalHints d w)
+        let dim = (fromIntegral $ wa_width wa, fromIntegral $ wa_height wa)
+        return $ dim /= applySizeHints 0 sh dim