catch exceptions when calling user-written code.

This is a minimal approach that only catches error
in actual user-written code.

Main.hs

@@ -165,6 +165,7 @@ handle (KeyEvent {ev_event_type = t, ev_state = m, ev_keycode = code})
     | t == keyPress = withDisplay $ \dpy -> do
         s  <- io $ keycodeToKeysym dpy code 0
         whenJust (M.lookup (cleanMask m,s) keys) id
+                     `catchX` return ()
 
 -- manage a new window
 handle (MapRequestEvent    {ev_window = w}) = withDisplay $ \dpy -> do
@@ -213,6 +214,7 @@ handle e@(ButtonEvent {ev_window = w,ev_event_type = t,ev_button = b })
     -- grabbed in grabButtons. Otherwise, it's click-to-focus.
     isr <- isRoot w
     if isr then whenJust (M.lookup (cleanMask (ev_state e), b) mouseBindings) ($ ev_subwindow e)
+                      `catchX` return ()
            else focus w
     sendMessage e -- Always send button events.
 

Operations.hs

@@ -66,7 +66,7 @@ manage w = whenX (fmap not $ isClient w) $ withDisplay $ \d -> do
 
     n <- fmap (fromMaybe "") $ io $ fetchName d w
     (ClassHint rn rc) <- io $ getClassHint d w
-    g <- manageHook w n rn rc
+    g <- manageHook w n rn rc `catchX` return id
     windows (g . f)
 
 -- | unmanage. A window no longer exists, remove it from the window
@@ -169,7 +169,7 @@ windows f = do
 
     whenJust (W.peek ws) $ \w -> io $ setWindowBorder d w fbc
     setTopFocus
-    logHook
+    logHook `catchX` return ()
     -- io performGC -- really helps, but seems to trigger GC bugs?
 
     -- hide every window that was potentially visible before, but is not