I have searched for people in similar situations, but mostly found out about people who could not make Chrome go fullscreen, but for whom Firefox would.In my case, I can only get fullscreen to work in Chrome, and not in Firefox. What I mean is that when I press F11, Chrome covers correctly xmobar above, but Firefox not. Firefox enters its fullscreen mode, hiding the tabs menu and title bar all of that, but it remains tiled and not covering xmobar, like so:My xmonad.hs is very long, but I have narrowed it down as much as I could to make this easier:import XMonad.Hooks.ManageDocksimport XMonad.Hooks.ManageHelpersimport XMonad.Layout.NoBordersimport XMonad.Util.Run(spawnPipe)import XMonad.Hooks.FloatNext (floatNextHook)import XMonad.Actions.SpawnOnimport qualified XMonad.Hooks.EwmhDesktops as EWMHimport System.IOimport XMonadimport XMonad.Hooks.DynamicLogimport XMonad.Layout.ResizableTilemyManageHook = manageDocks <+>               floatNextHook <+>               (isFullscreen --> doFullFloat) <+>               manageHook defaultConfigmyLayout = smartBorders . avoidStruts $ Full ||| tiled  where tiled = ResizableTall 1 (3 / 100) (2 / 3) [ 2 / 3]main = do  xmproc <- spawnPipe xmobar  xmonad $    EWMH.ewmh defaultConfig {        manageHook = myManageHook <+> manageSpawn      , handleEventHook = handleEventHook defaultConfig <+> EWMH.fullscreenEventHook      , logHook = dynamicLogWithPP $ xmobarPP { ppOutput = hPutStrLn xmproc }      , layoutHook         = myLayout  }The screenshot above was taken with this xmonad.hs.I also can get Zathura to go fullscreen, but not VLC nor Spacemacs.
Fullscreen works in Chrome but not in Firefox in XMonad
firefox;xmonad;fullscreen