[xmonad] How to extend layout modifier by visibility of status bar ?

[Dunric]

Hi,

I'm trying to extend XMonad.Layout.NoBorders.lessBorders modifier 
function. The goal is to don't draw border if there is only one window 
focused AND statusbar is hidden at the same time.

-- status bar gets spawned by XMonad.Hooks.DynamicLog.statusBar
main = xmonad =<< statusBar "xmobar" myBarPP toggleStrutsKey myConfig

-- an attempt to add SetsAmbiguous instance to handle status bar visibility
data MyAmbiguity = NoStatusBar deriving (Read, Show)
instance SetsAmbiguous MyAmbiguity where
     hiddens amb wset mst wrs
         | NoStatusBar <- amb = wins
         where
             wins        = filter (`elem` StackSet.integrate' mst) $
                             map fst (withoutSBar wrs)
             -- HERE I WOULD NEED TO CHECK IF STATUS BAR IS VISIBLE OR NOT
             withoutSBar = filter (\ (_, winrect) -> winrect == 
getScreenRect wset)
             getScreenRect  = screenRect . StackSet.screenDetail . 
StackSet.current

Any idea how to detect if status bar is visible or not ?

Thx.

David