Remember if focus changes were caused by mouse actions or by key commands

If the user used the mouse to change window focus (moving into or clicking on a
window), this should be handled differently than focus changes due to keyboard
commands. Specifically, it's inappropriate to discard window enter/leave events
while the mouse is moving. This fixes the bug where a fast mouse motion across
multiple windows resulted in the wrong window keeping focus.

It's also helpful information for contrib modules such as UpdatePointer - it's
supposed to move the mouse pointer only in response to keyboard actions, not if
the user was moving the mouse.

XMonad/Core.hs

@@ -69,6 +69,7 @@ data XConf = XConf
                                       -- ^ a mapping of key presses to actions
     , buttonActions :: !(M.Map (KeyMask, Button) (Window -> X ()))
                                       -- ^ a mapping of button presses to actions
+    , mouseFocused :: !Bool           -- ^ was refocus caused by mouse action?
     }
 
 -- todo, better name

XMonad/Main.hsc

@@ -98,7 +98,8 @@ xmonad initxmc = do
             , normalBorder  = nbc
             , focusedBorder = fbc
             , keyActions    = keys xmc xmc
-            , buttonActions = mouseBindings xmc xmc }
+            , buttonActions = mouseBindings xmc xmc
+            , mouseFocused  = False }
         st = XState
             { windowset     = initialWinset
             , mapped        = S.empty

XMonad/Operations.hs

@@ -165,7 +165,8 @@ windows f = do
     -- will overwrite withdrawnState with iconicState
     mapM_ (flip setWMState withdrawnState) (W.allWindows old \\ W.allWindows ws)
 
-    clearEvents enterWindowMask
+    isMouseFocused <- asks mouseFocused
+    unless isMouseFocused $ clearEvents enterWindowMask
 
 -- | setWMState.  set the WM_STATE property
 setWMState :: Window -> Int -> X ()
@@ -294,7 +295,9 @@ setTopFocus = withWindowSet $ maybe (setFocusX =<< asks theRoot) setFocusX . W.p
 -- the mouse to a new screen).
 focus :: Window -> X ()
 focus w = withWindowSet $ \s -> do
-    if W.member w s then when (W.peek s /= Just w) $ windows (W.focusWindow w)
+    if W.member w s then when (W.peek s /= Just w) $ do
+                              local (\c -> c { mouseFocused = True }) $ do
+                                  windows (W.focusWindow w)
                     else whenX (isRoot w) $ setFocusX w
 
 -- | Call X to set the keyboard focus details.