Layout modifier, which is responsible for creation of decoration rectangles (windows), updating and removing them when needed. It is parameterized by DecorationGeometry, which says where decorations should be placed, and by DecorationEngine, which says how decorations should look.

This module exports decorationEx function, which is a generic function for adding decorations to your layouts. It can be used to use different decoration geometries and engines in any combination. For most used combinations, there are convenience functions in XMonad.Layout.DecorationEx.TextEngine, XMonad.Layout.DecorationEx.TabbedGeometry, and XMonad.Layout.DecorationEx.DwmGeometry.

You can use this module with the following in your xmonad.hs:

import XMonad.Layout.DecorationEx.LayoutModifier

Then edit your layoutHook by adding the DwmStyle decoration to your layout:

myL = decorationEx shrinkText myTheme myEngine myGeometry (layoutHook def)
        where
          myGeometry = DefaultGeometry -- or another geometry type
          myEngine = TextDecoration    -- or another decoration engine
          myTheme = GenericTheme {...} -- theme type should correspond to selected engine type

main = xmonad def { layoutHook = myL }

For more detailed instructions on editing the layoutHook see:

XMonad.Doc.Extending