WindowArranger: add a SetGeometry message - needed to enable mouseDrag

XMonad/Layout/WindowArranger.hs

@@ -90,6 +90,7 @@ data WindowArrangerMsg = DeArrange
                        | MoveRight     Int
                        | MoveUp        Int
                        | MoveDown      Int
+                       | SetGeometry   Rectangle
                          deriving ( Typeable )
 instance Message WindowArrangerMsg
 
@@ -134,6 +135,9 @@ instance (Show a, Read a, Eq a) => LayoutModifier WindowArranger a where
               fa             = fromAWR     wr
               chk        x y = fi $ max 1 (fi x - y)
 
+    pureMess (WA t b (wr:wrs)) m
+        | Just (SetGeometry   r) <- fromMessage m, (w,_) <- fromAWR wr = Just . WA t b $ AWR (w,r):wrs
+
     pureMess (WA _ b l) m
         | Just DeArrange <- fromMessage m = Just $ WA False b l
         | Just Arrange   <- fromMessage m = Just $ WA True  b l